TBIRAZOLOPYRIMIDINES: THEIR SYNTHESIS AND STRUCTURE

By

Leonard Everett Brady

A THESIS

Submitted to the School for Advanced Graduate Studies of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of

DOCTOR OF PHILOSOPHY

Department of Chemistry

1958 ProQuest Number: 10008592

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iii TETRAZOLOPYRIM IDINES: THEIR SYNTHESIS AND STRUCTURE

By

Leonard Everett Brady

AN ABSTRACT

Submitted to the School for Advanced Graduate Studies of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of

DOCTOR OF PHILOSOPHY

Department of Chemistry

Year 195>8

Approved f ABSTRACT

The objectives of this work were to prepare some tetrazolopyrimidines for examination of their pharmacological properties and to attempt to

shed some light on the structure of these compounds.

The earliest recorded preparation of compounds of this group was that reported in 1909 by Billow (1). He assigned the bicyclic tetra-

zolopyrimidine structure rather arbitrarily to his products and no attempt had been made until now to gather evidence regarding the actual

structure of these compounds. Two points have been in doubt with regard to this structure. The first concerns the orientation of substituents, while the second point involves determination of whether the compounds actually contain the bicyclic system proposed by Btilow.

In the condensation of p -«ketoesters with 5-aminotetrazole two

orientations are possible, depending upon whether the amino group of

the 5-aminotetrazole reacts with the carbonyl group or with the

carbethoxy group of the ketoester,

(A)

- N OH R-C0-CH2-C02C2H5 + h 2n-c' II or HH- N

R Experiments were conducted involving the attempted acylation of

5 -aminotetrazole by acid chlorides and anhydrides and by free carboxylic

v acids. Acylation m s also attempted, by the action of esters alone and

in acetic acid solution or in ethanolic solution in the presence of piperidine. These experiments revealed that acylation occurred in the presence of acid chlorides or anhydrides or of free carboxyli© acids.

Acylation also tpok place under conditions which could lead to the

equilibrium formation of free carboxylic acids, as in the case of the

esters dissolved in glacial acetic acid.

Treatment of 5-aminotetrazole with ethyl acetoacetate in ethanolic

solution in the presence of a basic catalyst resulted in a greatly

increased, yield of condensation product over that obtained in the

absence of such catalysts. Since these are conditions which normally

promote azomethine formation, and. in view of the lack of acylation by

simple esters under the same conditions, this is interpreted, as

evidence for the formation of Structure A in this reaction. This is

In agreement with the structure assignment made by Billow.

A series of condensation products of this type m s synthesized by

interaction of ^mminotetrazole with variously substituted p-ketoesters

and with acetylacetone.

Proof of the bicyclic structure m s accomplished by an alternate

method of synthesis of the series of compounds just described. The

same carbonyl compounds which had reacted with 5-aminotetrazole were

allowed to react with S-methylisothiourea, producing a series of

2-methylmercaptopyrimid.ines.

Hydrazinolysis of the 2-*methylmercaptopyrimidines m s carried out

by treatment with either aqueous hydrazine hydrate solutions or absolute

vi ethanolic solutions of anhydrous hydrazine. Higher yields resulted from the use of the aqueous solutions, but were accompanied, by increased by-product formation.

Benzal derivatives of these 2-hydrazinopyrimidines were prepared by heating them with benzaldehyde in aqueous ethanolic acetic acid solution.

Diazotization of the 2-hydrazinopyrimidines resulted in the formation of a series of compounds identical with those prepared by interaction of 5-aminotetrazole with the various carbonyl compounds.

Identity was established, in each case by determination of melting points and mixture melting point and. by comparison of the infrared, absorption spectra of the compounds prepared by both routes.

The proof of the tetrazolopyr imidine structure may be represented schematically as follows?

R-CO

CH2-C02C2Hs By one route the pyrimidine ring is formed on an existing tetra- zole nucleus*. In the second method a pyrimidine derivative is treated so as to form the tetrazole ring upon it. This removed any doubt that the Billow synthesis had formed the postulated bicyclic products .

Members of this series of compounds were submitted to Parke, Davis and Company to be screened as possible cancer antimetabolites and as potential central nervous system stimulants.

Reference Cited

1. C. Billow, Ber., 1+2, 14+29 (1909).

viii TABLE OF CONTENTS

Page

INTRODUCTION. *...... 1

HISTORICAL...... 2

DISCUSSION...... 5

EXPERIMENTAL...... 22

Preparation of Tetrazolo[a]pyrimidines From 5-Aminotetrazole.. 22 5-Hydroxy-7-methyltetrazolo [a ]pyr imidine ,...... 22 A . In Glacial Acetic Acid ...... 22 B. In l,U-Dioxane...... 23 C . In Ethanol, with Piperidine Catalyst...... 2k 5-Hydroxy-7~phenyltetrazolo [a]pyrimidine...... 2k A . Duplication of Billow1 s Method ...... 2k B. Condensation of Ethyl Benzoylacetate with 5-Amino­ tetrazole ...... 25 C. Isolation of the Tetrazolo[a]pyrimidine from the Salt 26 5,7-Dimethyltetrazolo [ajpyrimidine ...... 26 5-Hydroxy-6 , 7-dimethyltetrazolo[ajpyrimidine...... 27 5-Hydroxy-6-ethyl-7-methyltetrazolo [a] pyrimidine ...... 28 5-Hydroxy-6-n-propyl~7-iriethyltetrazolo [a]pyrimidine...... 28 5~Hydroxy-6-isopropyl-7~methyltetraz olo [a]pyrimidine...... 29 5-Hydroxy-6-n-butyl-7-methyltetrazolo [ajpyrimidine...... 29 5-Hydr oxy-6, 7 , 8,9 -t etrahydr otetraz olo [b ] quinaz oline...... 30 Attempted Preparation of 5*7-Dihydroxytetrazolo[aj­ pyrimidine ...... 30

Acylation of 5-Aminotetrazole...... 31 A . Acylation by Carboxylic Acids ...... , .. 31 5-Acetylaminotetrazole ...... 31 5-PropionylaminotetraZole ...... s 31 5-Butyrylaminotetrazole ...... 32 5-Diethylacetylaminotetrazole ...... 32 B. Acylation by Acid Chlorides or Anhydrides...... 33 5-Propionylaminotetrazole ...... 33 5-Butyrylaminotetrazole ...... 3U 5-Diethylacetylaminotetrazole ...... 3 k 5-Benzoylaminotetrazole ...... 3U C. Acylation by Esters in Glacial Acetic Acid...... 35 5-Diethylacetylaminotetrazole ...... 35 D. Attempted Acylation by Esters Alone ...... 36

ix TABLE OF CONTENTS - Continued

Page

Attempted Preparation of 5^Acetylaminotetrazole ...... 36 Attempted Preparation of 5-Propionylaminotetraz0le , 36 Attempted Preparation of 5-Butyrylarainotetrazole...... 36 Attempted Preparation of 5-Benzoylaminotetrazole...... , 36 E. Attempted Acylation by Esters in Ethanolic Solution -with Piperidins Catalyst 37 Attempted Preparation of 5-Acetylamiuotetrazole...... 3 7

Preparation of 2-Methylmer capt opyr imid ine s ...... 37 2-Methylmer capto-U-methyl-6-hydroxypyr imidine ...... 37 2 -Methylmer capt o -1+ , 5 -dimethyl-6-hydr oxypyr imidine...... 38 2 -Methylmercapt o-U-methyl-5-ethyl-6-hydroxypyrimidine..... 38 2-Methylmer capto~i+-methyl-5-n-propyl-6-hydr oxypyr imidine. . . 39 Attempted Preparation .of 2-Methylmercapto-l+-methyl-5- isopropyl-6-hydroxypyrimidine...... 39 2-Methylmer capt o-l+-methyl-5-n-butyl-6-hydr oxypyr imid ine, ... 1+0 2-Methylmer capt o-l+-hydroxy-5,6 ,7,8-tetrahydroquinazoline ... 1+0 2-Methylmercapto-l+-phenyl-6-hydroxypyrimidine...... 1+1 Attempted Preparation of 2-Methylmer cap to-l+, 6-dihydroxy- pyrimidine ...... 1+1

Hydrazinolysis of 2-Methylmercaptopyrimidines ...... 1+2 2-Hydraz ino ~1|-me thyl-6-hydr oxypyr imid ine ...... 1+2 2-Hydrazino-l+,5-dlmethyl-6-hydroxypyrimidine...... 1+2 2 -Hydraz ino-U-methyl-5-ethyl -6-hydr oxypyr imidine .... 1+3 2-Hydrazino-1+-methyl-5-n-pr opyl-6-hydroxypyrimidine .... l+U 2-Hydrazino-l+-methyl-5-n-butyl-6-hydroxypyrimidine...... 1+1+ 2 -Hydraz ino-!+■-hydroxy-5 >6 , 7 > 8-tetrahydroquinaz oline 1+5 2-Hydraz ino-U-phenyl-6-hydroxypyrimidine ...... 1+5 2-Hydraz ino-1+,6-dimethylpyr imid ine...... 1+6

Preparation of Benzal Derivatives of the 2 -Hydraz in opyr imi- dines ...... 1+7 2-Benzalhydrazino-li-methyl-6-hydroxypyrimidine...... 1+7 2-Benzalhydrazino-li,5-dimethyl-6-hydroxypyriinidine...... 1+7 2-Benzalhydrazino-l+-methyl-5-ethyl-6-hydroxypyrimidine..... 1+8 2 -Benz alhyd raz ino -1+ -methyl-5-n-pr opyl -6-hyd r oxypyr imid ine ., 1+8 2-Benzalhydrazino-l+-methyl-5-n-butyl-6-hydroxypyrimidine... 1+8 2-Benzalhydrazino-l+-hydroxy-5,6 ,7,8-tetrahydroquinaz oline.. 1+9 2-Benzalhyd.razino-U-phenyl-6-hydr oxypyr imidine ...... 1+9 2-Benz alhyd raz ino-U, 6-dimethylpyr imidine ...... 1+9

Diazotization of 2-Hydraz inopyr imid ine s ...... 50 2-Hydroxy-7-methyltetrazolo[a]pyrimidine...... 50

x TABLE OF CONTENTS - Continued

Page

5-*Hydroxy-6,7-dxinethyltetrazolo[a]pyrimidine...... 5>T 5-Hydroxy-6-ethyl-7-*methyltetrazolo [a] pyrimidine...... 5l 5-Hydroxy~6-n-propyl-7“methyltetrazolo [a]pyrimidine.... ,.. 52 5-Hydroxy-6-n-butyl-7-methyltetrazolo[a]pyrimidine...... 52 5-Nydroxy-6j7j8>9"tetrahydrotetrazolo[b]quinazoline...... 53 5-Hyd.roxy-7",phenyltetrazolo [ajpyrimidine ...... 5U 5 57-Dlmethyltetrazolo [a]pyrimidine ...... 5h

Other Reactions...... 55 Attempted Hydrogenation of 5-Hydroxy-7~methyltetrazolo[a]- pyrimidine ...... 55 Hydrogenolysis of 5-Hydroxy-7-methyltetrazolo[ajpyrimidine. 55 Infrared-Absorption Spectra.... 4 *...... 56

SUMMARY...... 57

LITERATURE CITED...... 58

APPENDIX...... 59

xi LIST OF FIGURES

FIGURE Page

1. Infrared Spectrum of 5-Hydroxy-7-methyltetrazolo[a]- pyrimidine..... , , * , ,...... 60

2. Infrared Spectrum of 5“Hydroxy-6,7-dimethyltetrazolo[a]- pyrimidlne ...... *. 61

3. Infrared Spectrum of 5-Hydroxy-6-ethyl-7-niethyltetrazolo[a]- pyrimidine ...... 62

U. Infrared Spectrum of 5-,Hydroxy-6-Ji-jpropyl-7-methyltetrazolo- [a]pyr imid ine ...... 63

5. infrared Spectrum of 5~Hydroxy-6-n-butyl-7~methyltetrazolo- [alpyr imid ine ...... 64

6. Infrared Spectrum of 5-Hydroxy-7-ph.enyltetrazolo [aj- pyrimidine ..... 65

7. Infrared Spectrum of 5~,Hydroxy-6>7?'8,9-tetrahydrotetrazolo- [b ] quinaz oline...... 66

8. Infrared Spectrum of 5>7-Dimethyltetrazolo [a]pyrimidine 67

xii 1

INTRODUCTION

This work is concerned with tetrazolo [aJpyrimidines (Structure I).

In view of their structural similarity to the purines (Structure II),

it was thought that it might be of interest to prepare a series of these compounds to be submitted to screening as possible purine anti­ metabolites.

(I) (i d (m)

Metrazole (Structure III) is a bicyclic tetrazole derivative which

is known to exhibit pharmacodynamic activity. The tetrazolopyrlmidines,

then, might well be examined for possible effects upon the central

nervous system.

The assignment of the tetrazolo [a jpyrimidine structure was made

quite arbitrarily. It has, in fact, never been demonstrated that the

compounds are actually bicyclic. Furthermore, even assuming that the

bicyclic structure is correct, the relative positions of different

substituents have not been established. It would be useful, therefore,

to shed as much light as possible on the structure of these materials.

The objectives of this work, then, are to attempt to elucidate

the structure of the tetrazolofajpyrimidines and to prepare a series

of variously substituted compounds of this type to be submitted to screen­ ing as purine antimetabolites and as central nervous system stimulants. 2

HISTORICAL

■X* The first recorded preparation of a tetrazolo [a]pyrimid.ine (11)

■was that reported in 1909 by Billow who synthesized several compounds of this type (l) . Interaction of 5-a.minotetrazole with ethyl acetoacetate in glacial acetic acid led to the formation of a compound which was assumed to be 5-hydroxy-7-methyltetrazolo [ajpyrimidine . Similarly, by interaction of 5-aminotetrazole and ethyl benzoylacetate, 5-hydroxy-7- phenyltetrazolofajpyrimidine was reported to have been prepared. In the same paper, Bulow described the reaction of p-diicetones with

5-aminotetrazole upon refluxing in ethanolic solution in the presence of piperidine. Benzoylacetone gave rise to a compound which Bulow reported as ^-^ethyl-l-phenyltetrazolofajpyrimidine, while 5 ,7-dimethyl - and 5 ,6,7-trimethyltetrazolo fa]pyr imidines were said to be formed with acetylacetone and n-methylacetylacetone, respectively.

In 19UU, Dewar reported the synthesis of another member of this group of compounds (2). By using piperidine as catalyst in a reaction developed directly from Billow*s experience with diketones, Dewar condensed 5-aminotetrazole with 7-diethylamino-2,U-heptanedione. The product of this reaction melted over a wide range, although its elemental composition agreed well with calculated values . Dewar felt that this Indicated the presence of the two isomeric compoundsj

7c^-c-XN2 6C^?.r,^'N— § b 3 3

5-methyl-7 '(3 -diethylaminopropyl) tetrazolo fa Jpyriinidine and 5 - (3 -diethyl­ aminopropyl) -7-methyltetrazolo [a]pyr imidine, He -was finally able to separate, as the picrate, one pure isomeride. Ho attempt -was made to determine which one had been obtained or to find the other in the crude product.

Nachod and Steck in 19U8 repeated Bulow1 s synthesis of 5,7-dimethyl- tetraz olo fa]pyr imidine for the purpose of examining the ultraviolet spectrum of this compound (10). They concluded, on the basis of their findings, that Bulow1 s proposed structure was probably correct. The spectra in neutral and acidic media showed similarity to that of a benzenoid system. They attributed this to the existence of dipolar ions (Structures II, III, IV and V) which might accept protons in acid medium* In alkaline medium (pH 13), the spectrum was similar to that of 1 ,3 ,5 i7~octatetraene which has four conjugated double bonds as would the tetrazolopyrimidine in the unionized form (Structure I).

(IV) (V) h

In 19f?l* Ettel and Nosek synthesized two new tetrazolo[a]pyrimidines

(3). They allowed acetylpyruvic acid to condense with f?-amino tetraz ole by heating in the presence of hydrochloric acid to form a substance which they designated 7-methyltetrazolo[a]pyrimidIne-5-carboxylic acid.

Treatment of this substance with diethylamine and phosphorus oxychloride in benzene solution yielded the N,N~diethylcarboxamide. 5

DISCUSSION

When Bulow prepared the first tetrazolo[a]pyrimidines, he assigned certain structures for which he reported no experimental justification.

In the case of the condensation of acetylacetone with ^■•^irin'tetrazole there can be no doubt concerning the position of substituents since acetylacetone is symmetrical, provided, however, that the bicyclic

Structure ^ ant/nall-vr fnrmpH _

CHo-CO-CHP-CO-CH. + H ?N

In the reaction of ethyl acetoacetate, however, it seems possible that Bulow* s proposed structure (A) is not the only one which could result from the condensation.

(A)

OH N — N or

CH3

Structure A would result by the formation of an azomethine deriva­ tive from the carbonyl group of the ketoester and the amino group of

5-aminotetrazole followed by closure of the pyrimidine ring through acylation of the 1-position by the carbethoxy group . 6

Bulow completely ignored the possibility that Structure B could result from acylation of the amino group of 5-aminotetrazole by the carbethoxy or carboxyl group and cyclization involving the carbonyl group and the 1 -position of the tetrazole nucleus.

Bulow carried out the reaction of ethyl acetoac-etate and 5-amino­ tetrazole in refluxing glacial acetic acid. In attempting to repeat

Bulow1s preparation, variable results tfere obtained. In some cases the tetrazolopyrimidine, m.p. 2li7°C., separated from the reaction mixture first followed by a second product not described by Bulow,

In other cases a mixture of products was obtained immediately. The mixture was separable by repeated extractions with small amounts of hot water into Bulow* s compound and the same second product.

Elemental analysis of the product which appeared to be the material described by Bulow corresponded to that calculated for 5-hyd.roxy-?- methyltetrazolo£a]pyrimidine, while the elemental composition of the second product indicated it to be a mixture of one mole of 5-hydroxy-

7-methyltetrazolo[a]pyrimidine with two moles of 5-acetylaminotetrazole.

Some of the 5-aminotetrazole had apparently been acetylated by the glacial acetic acid used as solvent for the reaction.

An attempt was made to avoid the formation of side products of this type. Ethyl acetoacetate was refluxed with 5-aminotetrazole using l>ii-dioxane as a solvent. The product of this reaction was purer, consisting only of the material described by Bulow, but the yield was only 6 .6$ of theory compared with the 1'7.2$ obtained by Bulow* s method. 7

If Bulow had assigned the correct structure to this compound, then its synthesis in this case involved the formation of an azomethine derivative by reaction of the amino group of 5-aminotetrazole and the carbonyl group of ethyl acetoacetate. In 1925.* Stolle and. Orth (13) had reported preparation of the benzylidene derivative of 2-phenyl-5- aminotetrazole by prolonged heating of the tetrazole with benzaldehyde, but this was a ring-substituted tetrazole having no acid function.

The apparent failure of 5-aminotetrazole to form azomethines was explained by Henry and Finnegan (6) . They postulated that 5-amino­ tetrazole when unsubstituted on the ring probably did not form a benzal derivative because of its own acidity which would catalyze the hydrolysis of the azomethine.

N — N OH N—N

They found it possible to bring about azomethine formation by using the guanidinium or triethylammonium salt of 5-aminotetrazole, It was not necessary to use added basic catalyst in the case in which p-dimethyl- aminobenzaldehyde was allowed to react with 5-aminotetrazole, since the aldehyde itself was basic enough to drive the reaction to completion.

In another paper (5)* t-he same workers synthesized some 5-benzal- aminotetrazoles using piperidine as the catalyst.

In view of these facts, it was thought advisable to attempt the reaction of 5-aminotetrazole and ethyl acetoacetate under basic con­ ditions, Accordingly, an ethanolic solution of 5-aminotetrazole and 8 ethyl acetoacetate was treated with piperidine and refluxed for I|8 hours. The yield of the Bulow product, m.p, 2U7DC., was 3 9 * 7 % of theory, representing a sixfold increase over that obtained in the absence of such catalysis.

This observation seemed to support Bulow* s views, since the basic

catalysis which so vastly increased the yield of this reaction would

have been expected to be most effective had the reaction actually

involved the condensation of the carbonyl group of the ketoester with

the amino group of the tetrazole. It seemed proper, however, to

examine the other reactive function of the ester. In order to supple­

ment the above observations, it would be useful to demonstrate! the

reactivity of the carbethoxy and carboxyl groups with the amino group

of 5-aminotetrazole,

Samples of 5-aminotetrazole were heated with various carboxylic

acids. By heating in an oil bath thermostatically maintained at

116-118°C., 5-acetylamino-, 5-propionylamino-, and 5-diethylacetylamino-

tetrazoles were prepared from the appropriate acids. When 5-aminotetra­

zole was heated in butyric acid under reflux, the yield was only

slightly greater in spite of the fact that the temperature of reaction

was approximately ii5° higher in this case.

The 5-acylaminotetrazoles prepared from the acids were identified

by comparison with samples of the same compounds prepared by treating

5-aminotetrazole with the appropriate acid chloride or anhydride. When

the acid chloride and 5-aminotetrazole were heated in refluxing

l,U-dioxane, the yields obtained were smaller than when 5-aminotetrazole 9

■was heated on the steain bath with the undiluted acyl chloride. In the one case in which the acid anhydride was employed, the yield was significantly lower than with the acyl chlorides.

This demonstration of the reactivity of the free carboxyl group with 5-aminotetrazole explained the presence of 5-acetylaminotetrazole as a contaminant .in the product from the reaction of 5-aminotetrazole with ethyl acetoacetate in glacial acetic acid. It shed no immediate light, however, on the possible reaction of the carbethoxy group of ethyl acetoacetate with the amino group of 5-aminotetrazole to give rise to

a product having Structure B. If reaction could be induced between

5-aminotetrazole and a simple ester having no ketone function, this

would give weight to the argument in favor of the possibility that

Structure B is the correct one.

A sample of ethyl diethylacetate was treated with 5-aminotetrazole

in refluxing glacial acetic acid, duplicating the conditions under

which Bulow carried out his reaction with ethyl acetoacetate. The

product was 5-diethylacetylaminotetrazole identical with that formed by

interaction of 5-aminotetrazole and either diethylacetlc acid or

diethylacetyl chloride,

In an attempt to draw further analogy between the reaction of the

ketoesters and that of the simple esters, several of the latter were

treated with 5-aminotetrazole without solvent or catalyst. Ethyl acetate,

ethyl propionate, ethyl butyrate, and ethyl benzoate were heated in

turn with 5-aminotetrazole. After as much as 72 hours of heating, the

5-aminotetrazole could be recovered quantitatively. 10

It will be remembered that the yield of product from the treatment of 5-amtnotetrazole -with ethyl acetoacetate -was vastly increased when the reaction was carried out in the presence of piperidine. Therefore, an ethanolic solution of ethyl acetate and 5-aminotetrazole was treated with piperidine and heated under reflux for 96 hours. At the end of this time, evaporation of the reaction mixture and recrystallization

of the residue led to complete recovery of the 5-aminotetrazole.

From the foregoing observations it is apparent that acylation of

5-aminotetrazole requires the presence of the free acid or an acid

chloride or anhydride. Acylation by interaction with an ester occurs

only when acetic acid is present and the opportunity for an equilibrium

between ester and acid is available.

R-C02C2H5 - CH3-C02H------R-C02H i- ch3-co2c2h5

If Structure B were to result from the interaction of ethyl

acetoacetate and 5-aminotetrazole in glacial acetic acid, it seems

necessary to postulate the presence of acetoacetic acid in the reaction

mixture. Mien ethyl acetoacetate and 5-aminotetrazole are heated

together without solvent or catalyst a small amount of tetrazolopyrimidine

is formed. The fact that the presence of glacial acetic acid increases

the yield would appear to support the view that an acid interchange and

acylation with acetoacetic acid is involved.

On the other hand, it has also been determined that the yield of

tetrazolopyrimidine is markedly enhanced when the reaction is done in

ethanol solution in the presence of piperidine as catalyst. 11

These conditions are known to favor azomethine formation. It should also be emphasized that piperidine does not catalyze a reaction between

simple esters and £-aminotetrazole, From these considerations it

appears that azomethine formation between 5-aminotetrazole and ethyl

acetoacetate leading to a tetrazolopyrimidine of Structure A is the

most plausible explanation of these observations.

The possibility that the presence of the electrophilic carbonyl

group on the a-carbon atom in the ketoesters causes the carbethoxy group

to react differently than in the simple esters remains to be considered.

An experiment was devised in which 5-'aininotetrazole was treated with

diethyl malonate in ethanolic solution with piperidine. The two

carbethoxy groups of this compound should approximate for each other

the electrical environment of the carbethoxy group of the p-ketoesters.

After 192 hours of refluxing, only 5~arain-otetrazole was recovered from

the reaction mixture.

The experiment described by Bulow in which he treated 5-amino­

tetrazole with ethyl benzolyacetate in refluxing glacial acetic acid

was repeated according to his directions/ The product described by

Bulow as 5-hydroxy-7~phenyltetrazolo[a]pyrimidine was ascertained by

means of elemental analysis, melting point, mixture melting point and

comparison of infrared spectra to be 5-acetylaminotetrazole. It is

interesting to note that Bulow did not report an elemental analysis of

this product. Reinvestigation of this reaction using an ethanolic

solution of ethyl benzoylacetate and 5-a-minotetrazole with piperidine

as catalyst led to the formation of the desired 5-hydroxy-7-phenyl-

tetrazolo[a]pyrimidine. This tetrazolopyrimidine separated from the reaction mixture as a piperidinium salt from which the free tetrazolo- pyriiriidine could be obtained by treatment with acids. The piperidinium

salt was obtained both as a hydrate and in anhydrous form on crystalli­

zation from aqueous solvents or absolute ethanol, respectively.

A series of ethyl a-alkylacetoacetates was prepared by the method

of Wislicenus (18). These compounds were allowed to react with 5-amino­

tetrazole in ethanolic solution with piperidine as catalyst. In this

manner a group of 5-hydroxy-6-alkyl-7-methyltetrazolo [a]pyrimidines was

synthesized. The alkyl radicals involved were the methyl, ethyl,

n-propyl, isopropyl, and n-butyl groups. In addition to these compounds

and those previously mentioned, the condensation product of 5-amino­

tetrazole with ethyl cyclohexanone-2-carboxylate was prepared . This

product was presumably 5-hydroxy-6,7,8 ,9-tetrahydrotetrazolofb]-

quinazolineElemental analyses of all of these compounds were in

good agreement with calculated values.

All of the reasoning hitherto employed regarding the probable

structure of these materials has been predicated upon acceptance of the

existence of the fused-ring bicyclic system as proposed by Bulow.

It was felt that confirmation of the ring structure could best be

achieved by synthetic means. In the preparations already described,

the synthesis had commenced with the tetrazole nucleus present; the

pyrimidine ring was formed in the course of the reaction. If it were 13 possible to start -with an appropriately substituted pyrimidine and add

the tetrazole ring, there would be no doubt as to the actual existence

of the tetrazolopyrimidine nucleus.

Precedent for such a synthesis was found in the work of Finnegan,

Henry and Lieber (U). These workers had synthesized l-alkyl(or aryl)-

5-aminotetrazoles by treatment of appropriately substituted amino-

guanidines with nitrous acid. This synthesis is presumed to proceed

through cyclization of the intermediate azido compound.

m HONO m R-NH-C-NH-NH2 > R-NH-C-N3 R-N C-NH2 I tl N

By means of this reaction, Finnegan and his co-workers prepared

5-aminotetrazoles substituted in the 1-position with various alkyl and

aryl groups. The substituted amino guanidines had been prepared by the

method of Kirsten and Smith (9) through hydrazinolysis of N-substituted-

S-methylisothiuronium iodides.

HH NH RNH-C-SCH3 *HI + N 2H4 RNH-8-NaH3 + GH3SH

A close structural analogy between the tetrazolo [aIpyrimidines

and the 1-substituted-^-aminotetrazoles led to the conjecture that

treatment of a 2-hydrazinopyrimidine with nitrous acid could lead to

formation of a 2-azidopyrimidine which could undergo ring closure to

form a tetrazolo fa]pyrimidine.

HONO

R R R lU

The chemical literature showed no instance of the preparation of a 2-hydrazinopyrimidine, but reference was made to the synthesis of

2-methylmercaptopyrimidines, Wheeler and Jamieson (If?) had condensed acetylacetone with S-methylisothiuronium iodide in aqueous alkali.

This reaction was repeated and the liquid product purified by vacuum distillation.

Wheeler and Merriam (16) had reported the reaction of S-alkyliso- thiuronium iodides with ethyl acetoacetate, ethyl a-ethylacetoacetate and ethyl benzoylacetate to form 2-alkylmercapto-6-hydroxypyrimidines with U-methyl, 1;-methy1-5-ethyl, and U-phenyl substituents, respectively.

In some of their syntheses they employed S-methylated thiourea and in others the S-ethylated compound, each prepared by treatment of thiourea with the appropriate alkyl halide.

By adaptation of the method of Wheeler and Merriam, a series of pyrimidines was prepared from S-methylisothiuronium iodide with the same ketoesters which had been utilized in the condensations with

5-aminotetrazole.

It was noted that, as reported by Wheeler and Merriam, when the ketoester and S-methylisothiuronium iodide were dissolved in an aqueous solution of potassium hydroxide and allowed to stand for some days, the reaction could not be depended upon to take place in every instance,

The same reactants which had performed well on one occasion would fail completely on another. They found, and it was here confirmed, that these failures could be eliminated if the reaction mixture, after stand­ ing overnight at room temperature, was heated to its boiling point, 15 cooled and acidified, Prolonged heating of this mixture would probably result in hydrolysis of the S~methylisothiourea. Indeed, the methyl- mercaptopyrimidines themselves are susceptible to hydrolysis to the corresponding uracils, as was noted in one instance when an attempt was made to recrystallize a methylmercaptopyrimidine from water,

Two attempts to cause interaction of S-methylisothiuronium iodide with ethyl a-isopropylacetoacetate were unsuccessful. Possibly steric hindrance due to the presence of the a-isopropyl substituent on the acetoacetic ester was responsible for the failure of these attempts.

Those acetoacetic esters substituted in this position with methyl, ethyl, n-propyl or n-butyl groups performed well in this type of preparation. No a-branched substituents other than the isopropyl were examined in this regard. It is interesting that the yield was also lower than with the other members of the series when ethyl a-isopropyl­ acetoacetate was allowed to react with 5>-aminotetraz ole ■

Investigation of the hydrazinolysis of the methylmercaptopyrimidin.es disclosed that it was possible to obtain 2-hydrazinopyrimidines by this method.

R R

Two methods were found efficacious. The difference between them was in the solvent employed. In most cases, a 9 % % ethanolic solution of the 2-methylmercaptopyrimidine was treated with a tenfold excess of an aqueous solution of hydrazine hydrate. This was heated under 16 reflux until the odor of methyl mercaptan "was no longer detectable at the top of the reflux condenser. When the reaction mixture -was chilled, the solid hydrazinopyrimidine separated and could be isolated by

filtration.

The second method of synthesis involved the use of anhydrous

hydrazine in absolute ethanolic solution. The hydrazinopyrimidines

formed in this -way could not be depended upon to precipitate upon cool­

ing since they were rather more soluble in the anhydrous ethanolic

solution than they had been in aqueous ethanolic solution. It was

necessary, therefore, when using this solvent, to evaporate the reaction

mixture in order to collect this product.

Upon evaporation of the mother liquor from the preparations employ­

ing aqueous hydrazine, a highly impure residue resulted. In two cases,

exhaustive recrystallization of this material revealed it to be mainly

composed of the uracil derived from hydrolysis of the 2-methylmercapto-

pyrimidine. No attempt was made to isolate and purify this material

in every case.

In spite of the formation of the uracil as by-product, the use of

aqueous hydrazine solutions invariably led to larger yields than were

obtainable under anhydrous conditions. It is thought that this merely

represented a temperature effect, since the anhydrous reaction mixtures

boiled at lower temperatures than did the aqueous mixtures. In cases

involving the use of very small amounts of starting material it was

found better to use the anhydrous conditions and accept the smaller

yield of pure product rather than to risk the separation of the desired 17 product from the resultant mixture -when the aqueous medium was employed.

In order to characterize these hitherto unknown hydrazinopyrimidines, elemental analyses were obtained. The results of these analyses agreed with calculated values for the anticipated hydrazinopyrimidines.

As another check, benzal derivatives of the hydrazinopyrimidines were synthesized in several instances. Aqueous alcoholic solutions of benzaldehyde and the hydrazino compounds with acetic acid were evaporated to dryness on the steam bath. Recrystallization of the residue from ethanol was the method of purification employed. The analytical data for most of these substances were in accord with calculated values.

In the cases of 2-benzalhydrazino-lj~met hyl-6-hydroxypyrimidine and

2-benzalhydrazino-U-hydroxy~5,6,7>8-tetrahydroqiinazoline, however, the observed figures in the nitrogen analyses were lower than those calculated though the carbon and hydrogen analyses were in agreement with theory. One other member of this series gave unexpected analytical results. The elemental composition of 2-benzalhydrazinO“U-methyl-5-n- propyl-6-hydroxypyrimidine indicated it to be the hemihydrate. The composition was unchanged by drying the analytical samples to constant weight before analysis. It had been noted that this compound and the other b enz alhyd raz inopyr imid ine s in this series were hygroscopic, but this was the only case in which hydration to a constant value was observed and also the only one in which the hydration was persistent enough to be unremovable by heating at diminished pressure.

The final step in the chain of reactions involved the treatment of the 2-hydrazinopyrimidines with nitrous acid to determine whether they 18 would form tetrazolo [aIpyrimidines In a maimer analogous to the for­ mation of 1-substituted-5-aminotetrazoles from substituted aminoguanidines ,

Each of the 2-hydrazinopyrimidines was dissolved in excess dilute hydrochloric acid and treated with saturated aqueous sodium nitrite solution until the first excess of nitrous acid was indicated by the starch-potassium iodide paper end point. During the addition of the nitrite a solid substance often separated from solution. No attempt was made to determine whether this precipitate was the final product or the intermediate 2-azidopyrimidine. The solid redissolved as the reaction mixture was gradually made alkaline with sodium carbonate.

The tetrazolopyrimidine precipitated when the alkaline solution was acidified after standing for some hours. Two exceptions to this behavior were noted. Due, perhaps, to the presence of the hydrophobic phenyl group , 2-hydrazino-U-phenyl-6-hydroxypyrimidine was not completely soluble In either the acid or base, 2-Hydrazino-U,6-dimethylpyrimidine dissolved readily enough in the hydrochloric acid solution, but the solid which separated upon treatment with sodium nitrite solution did not redissolve when the mixture was made basic. This was due, of course, to the absence of the acid hydroxyl function present in the pyrimidines derived from the substituted ketoesters, In every case the tetrazolo- pyrimidine prepared in this m y was identical with the product from the

Bulow-type reaction of 5-aminotetrazole -with the appropriate ketoester or dicarbonyl compound. Identity was established in each case by observation of melting point and mixture melting point, and by compari­ son of infrared spectra. 19

The successful synthesis of the same products by adding a pyrimidine ring to a preformed tetrazole ring in one case and a tetrazole ring to a preformed pyrimidine ring in the second case leaves no doubt as to the structure of these products as bicyclic tetraz olopyr imid ine s.

Since the azido group is considered (1?) to exist as a resonance hybrid of two main resonance forms,

R : N : : N :: H j R : N : N ::: N : it may be seen that the terminal nitrogen atom is either electrically neutral or carries a negative charge, "When it is considered that this is the atom which presumably attacks the pyrimidine nucleus to effect closure of the tetrazole ring, it becomes necessary to consider the electrical nature of the ring atoms. This is also necessary because here too it is possible that either of two isomeric structures may be f ormed,

(A)

OH R

or

OH

(B)

R

The terminal nitrogen atom of the azido group would seem to be a nucleo- philic center and as such should have a greater tendency to attack the pyrimidine nitrogen having the most electrophilic character. 20

Inspection of the hydroxypyrimidine nitrogens reveals one to be an amine-type nitrogen while the other partakes more of the nature of an amide by tautomerism with the hydroxyl group.

R

OH 0

Location of a hydroxyl group on the ring atom adjacent to a nitrogen

should make it a more electrophilic atom than the nitrogen neighbored

only by an alkyl radical. It is felt, therefore, that ring closure probably takes place toward the pyrimidine nitrogen nearer the hydroxyl

group, giving rise to Structure A, This supports the conclusions drawn

from examination of the reactions of 5-amino tetrazole with carbonyl and

carbethoxy compounds.

Two attempts were made to hydrogenate 5“hydroxy-7-methyltetrazolo-

[alpyrimidine in the hope that the pyrimidine ring would be reduced.

This was part of a proposed scheme for proof of the orientation of the

methyl and hydroxyl groups in this compound. Hydrogenation of the

tetrazolopyrimidine in hot glacial acetic acid in the presence of

platinum oxide at about 50 p.s.i, hydrogen pressure at 60°C. gave a

substance other than starting material. The elemental analysis of this

product indicated that it had the empirical formula C5H7N30. A compound

of this same elemental composition is 2-amino-U-methyl-6-hydroxypyrimi-

dine. This material was found to agree in melting point with the sub­

stance obtained from the hydrogenation. When an authentic sample of

this compound was synthesized by treatment of guanidine carbonate with 21 ethyl aeetoacetate according to the method of Jaeger (8), the two were shown by mixture melting point to be identical.

Milder reaction conditions, under which hydrogenation of the tetra- zolopyrimidine was attempted in aqueous ethanol containing an excess of potassium hydroxide in the presence of platinum oxide catalyst had no

effect on the starting material. No further attempts were made to

reduce the tetrazolo [a]pyrimid.ine ring system.

Samples of the tetrazolo[a]pyrimidines prepared in this study were

submitted to Parke, Davis and Company for screening as cancer anti­

metabolites and as possible central nervous system stimulants. Testing

had not been completed at the time of this writing, but a preliminary

report indicated that one of these compounds had some effect as a

central nervous system stimulant. 22

EXPERIMENTAL*

Preparation of Tetrazolo [a]pyrimidines From 5>-Aminotetrazole

5>-Hydr oxy-7-methyltetra.z olo [a ]pyrimid ine

A. In Glacial Acetic Acid

The method of Biilow (1) -was altered to the extent of increasing

the reaction time for this preparation. Forty-two and five-tenths

grams (0.^0 mole) of 5-^aminotetrazole (7) and 78.0 grams (0.60 mole)

of ethyl acetoacetate were dissolved in 2^0 ml. of glacial acetic acid,

After I|8 hours at reflux temperature, the mixture was allowed to stand

at room temperature for 2l± hours and then chilled . The solid material

which separated was recrystallized from boiling water. The resulting

solid melted with decomposition at 2i|l°C. and appeared to consist of a

mixture of more than one type of crystal. Several recrystallizations

did .not alter the appearance or melting point of the material.

Treatment of the solid with one-fifth the amount of boiling water

necessary to dissolve it entirely and filtration while hot were repeated

five times. The solid material which precipitated from the first eluate

upon cooling melted with decomposition at 2U7-2U8°C, The melting points

of the other four portions ranged progressively lower with the last

melting and decomposing at 238°C, Each of the three intermediate

fractions was subjected to the same treatment as the original mixture

N/j 'All e3.emental analyses done by Micro-Tech, Skokie, 111. All melting points uncorrected. 23 and this process was repeated until virtually the entire amount of material isolated from the reaction had been separated into two portions.

The higher melting portion, melting point 2J4.7—2L|_8°C., comprised

13*0 grams of colorless needles and appeared to be the compound described by Bulow.

Analysis: Calculated for C5H5N50: C, 39.83 H, 3.35 N, U6.3.

Found: C, 39.95 H, 3-5i N, 1*7.5.

The remainder of the material consisted of 13 .0 grams of colorless plates which melted with decomposition at 238°C. Elemental analysis for this material is in agreement with that calculated for a mixture of two moles of 5-acetylaminotetrazole with one of 5~hydroxy-7-methyl- tetrazolo [a Jpyrimidine.

Analysis: Calculated for (C5H5N50 )(C3H4N50 )2: C, 32.65 H, 3*75 N, 51.8.

Found: C, 33 .65 H, 3.75 N, 52.0.

B. In l,l*-Dioxane

To a solution of 81*.5 grams (0,60 mole) of ethyl acetoacetate in

100 ml. of l,l|-dioxane were added 1*2.5 grams (0.50 mole) of 5-amino- tetrazole. The flask was fitted with a reflux condenser and heated by immersion in a thermostatted oil bath maintained at ll7°C. After 90 hours at the reflux temperature, the reaction mixture was evaporated on the steam bath and the solid residue recrystallized from boiling water. Sixteen and eight-tenths grams of 5-aminotetrazole were recovered and evaporation of the crystallization liquor followed by .recrystalli­ zation of the residue gave 3.0 grams of white needles which melted with 21* decomposition at 2l*7 0. This material was shown by means of a mixture melting point determination and comparison of infrared spectra to be identical with the compound prepared by Bulow1 s method, The amount

obtained represented a yield of 6.6$ of theory, based on unrecovered

5-aminotetrazole.

C. In Ethanol, with Piperidine Catalyst

A solution of 8.5 grams (0.10 mole) of 5-amino tetrazole and 19.5

grams (0.15 mole) of ethyl acetoacetate and 1 ml. of piperidine in 100

ml. of absolute ethyl alcohol was heated under reflux for a period of

1*8 hours. After this period, the reaction mixture was chilled in an

ice-water bath. "When very little solid precipitated, the entire mixture

was evaporated to dryness on a steam bath while a stream of air was

directed across the surface of the liquid. The dry residue was

recrystallized twice from boiling water, yielding 6,0 grams of colorless

needles identical with those prepared by the two previous' methods-as

evidenced by determination of melting point and mixture melting point

and by examination of the infrared spectrum of the product. The amount

of product after purification was 39.7$ of theory.

5-Hyd.r oxy-7 -phenylt et razol o [alpyrimidine

A. Duplication of Bulow*s Method

Twenty-four grams (0.28 mole) of 5-®Jrrinotetrazole and 61.5 grams

(0.32 mole) of ethyl benzoylacetate were heated at the reflux

temperature In 150 ml. of glacial acetic acid for 21* hours. After

standing another 30 hours at room temperature, the mixture was chilled 25

filtered. The solid material thus obtained was recrystallized twice from boiling water. Twelve and one-tenth grams of colorless plates were collected. These melted with decomposition at 267-2683C., which was in accordance with the results reported by Billow,

Analysis: Calculated for C3H5N50: C, 28.35 H, l*.Oj N, 55.1.

Found: C, 28,5l H, 1*.1$ N, 55-9> Ash, 1.0,

The elemental analyses indicated that the product, might be

5-acetylaminotetrazole. The substance showed no depression in melting point when mixed with an authentic sample of 5-a-cetyJaminotetrazole.

B. Condensation of Ethyl Benzoylacetate with 5“Aminotetrazole

Eight and five-tenths grams (0,10 mole) of 5-aminotetrazole and

21.1 gramcs (0.11 mole) of ethyl benzoylacetate and 3 ml. of piperidine dissolved in 100 ml, of absolute ethanol were heated under reflux by immersion of the flask in a thermostatted oil bath for 96 hours. At the end of this period, the reaction mixture was evaporated on the steam bath and the residue was recrystallized from boiling water. The white crystalline product melted sharply at 119°C. and then resolidified.

Upon further heating, the sample melted for a second time at lUi*°C,

This behavior was apparently due to the formation of a hydrate, since a sample dried at 100 C. in vacuum exhibited only the higher melting point. When a portion of the dried sample was recrystallized frdm water and air-dried, the 119°C. melting point recurred. When the whole reaction was repeated and the product recrystallized from absolute

ethanol, only the higher melting point was observed. The yield from

each preparation was 6.3 grams. The elemental composition of a dried 26 sample of this material corresponds to that which would be observed for the piperidine salt of the expected product.

Analysis; Calculated for C^H-jgNgO: C, 60.U$ H, 6,lj N, 28.2.

Found; C, 60.3$ H, 6.3$ N, 28.2.

The 6.3 grams obtained represented a yield 21.1$ of theory.

C, Isolation of the Tetrazolo[a]pyrimidine from the Salt

To isolate the tetrazolo[a]pyrlmidine from the salt 6 grams (0.02 mole) of the salt were dissolved in hot water and treated with U.3 ml. of concentrated hydrochloric acid. The curdy white precipitate which formed at once was filtered off after the mixturehad been cooled.

The residue was washed with water and then dried. It melted with o o vigorous decomposition at 22l*-225 0. after darkening from 200 C. This cream-colored product was recrystallized from water. The U.l grams of purified material (96,2$ of theory) melted with decomposition at

22b »5“225>°C,

Analysis; Calculated for C10H7N50: C a 56.3$ H, 3.3$ N, 32.8.

Found; C, 56.6$ H, 3.6$ N, 33.1.

5»?-Dimethyltetraz olo [a Jpyrimidine

In a duplication of a procedure reported by Bulow, 18.75 grams

(0.22 mole) of 5-aminotetrazole and 25.0 grams (0.25 mole) of acetyl- acetone and 1.5 ml, of piperidine were dissolved in 312 ml. of absolute

ethanol. This mixture was heated, under reflux f or 2b hours, When the reaction mixture was allowed to cool to room temperature, sturdy tan crystals were deposited. Sixteen and one-tenth grams (1*9.1# of theory) 27 of this substance were collected by filtration and melted at l5l-l523C.

After recrystallization from boiling water, the melting point was

151.5-152.0°C.

Analysis: Calculated for C6H7N5: C, 1+8.3$ H, l+.7$ N, 1+7.0.

Found: C, 1+8.3$ H, l+.6$ N, 1+6.9.

Mien the mother liquor was chilled in an ice-water bath, precipi­ tation of fine tan needles occurred. Seven grams of these crystals, m.p. lll+-1280C., were obtained, Recrystallization from boiling water gave long, hairlike crystals (ca. 1,5 inches in length) which melted at

139-lU0°C.

Analysis Found; C, 57.1$ H, 5.5$ N, 30.1.

These analytical data correspond with values calculated for a combination of one molecule of 5-aminotetrazole with two molecules of acetylacetone by elimination of three molecules of water. This sub­

stance was not investigated further,

5-Hydroxy-6,7-dimethyltetraz olo [a]pyr.imldine

A seventeen gram (0.20 mole) portion of 5-aminotetrazole was heated with 31.7 grams (0.22 mole) of ethyl a-methylacetoacetate prepared by the method of Wislicenus (18) in 150 ml. of absolute ethanol

containing 3 ml. of piperidine. Heating in the oil bath was continued

for 120 hours. At the end of this time, the reaction, mixture was

chilled and the precipitated solid removed by filtration. After two recrystallizations from 50$ aqueous ethanol, the yield from this reaction amounted to 16.0 grams (1+8.5$ of theory) of colorless needles melting at 226.5°C. with decomposition, 28

Analysis: Calculated for C6H7N50: C, 1*3.63 H, U*3J N, 1*2.1*

Found.: C, 1*3.93 H, 1*.53 N, 1*2.3. g-^ydroxy^-ethyl-T-methyltetrazoloJaJpyriinidine

The reaction of 17,0 grams (0.20 mole) of 5~ami.notetrazole with

3U• 8 grams (0.22 mole) of ethyl a-ethylacetoacetate (18) was carried out exactly as was the preparation of 5-hydroxy-6,7-dimethyltetraz olo-

[aIpyrimidine, The 16.1* grams of long colorless needles resulting corresponded to a yield of 1*5.8# of theory and melted at 182-183°G,

Analysis: Calculated for C7H9N50: C, 1*6.93 H, 5.13 N, 39.1.

Found: C, 1*6.83 H, 5.13 N, 39.0,

5 -H|ydr oxy-6-n-propyl-7-methylt etraz olo [ajpyrimidine

Seventeen grams (0.20 mole) of 5-aminotetraz o 1 e and 37.5 grams

(0.218 mole) of ethyl a-n-propylacetoacetate (18) were dissolved in

150 ml. of absolute ethanol with 3 ml, of piperidine and the reaction

flask was heated under reflux by immersion in a thermostat-controlled

oil bath for 180 hours. The reaction mixture was then evaporated by

directing a jet of air across its surface at room temperature. The

solid residue was recrystallized three times from boiling water. Twenty

and two-tenths grams of colorless needles which melted at lU5-^li60C .

were obtained (5 2 .3# of theory).

Analysis: Calculated for C, 1*9.73 H, 5.73 N, 36.2.

Found: 0 } 1*9.83 H, 5*83 N, 36.3. 29

5-Hydr oxy-6-»iscrpr opyl-7-methyltetraz olo [a 3 pyrimidine

A solution of 8,5 grams (0,10 mole) of 5~a-minotetrazole and 17.2 grams (0,10 mole) of ethyl a-isopropylacetoacetate (18) with 3 ml. of piperidine in 100 ml. of absolute ethanol was heated (oil bath) under reflux for 120 hours. At the end of this time, when no solid material

separated from solution upon cooling in an ice bath, the reaction mixture was evaporated on the steam bath. The syrupy concentrate was

treated with a few milliliters of water and then stirred and chilled with ethyl ether layered over the mass. As the beaker was scratched,

the aqueous layer became cloudy and some solid began to form. This was allowed to stand in the hood until the ether evaporated, leaving

a sticky solid which was recrystallized from 50$ aqueous ethanol.

Three grams (15-5$ of theory) of colorless platelets melting at

l82-l83°C. resulted.

Analysis: Calculated for C^H-j^NgO: C, U9 -75 H, 5*7$ N, 36.2.

Found: C, U9.7$ H, 5.6$ N, 36.2,

5 -Hydr oxy ^6 -n-butyl -7 -me t hylt et raz olo [ajpyrimidine

This material was prepared by the same procedure as that used for

the preparation of 5-hydroxy-6,7~dimethyltetrazolo[a]pyrimidine. From

17.0 grams (0.20 mole) of 5-aminotetrazole and IfL.O grams (0.22 mole)

of ethyl a-n-butylacetoacetate (18) 12.2 grams (29.5$ of theory) of

colorless needles, m.p. l5l-l52°C., were obtained.

Analysis: Calculated for C9H 13N50: C, 52.2$ H, 6.3$ N, 33.8,

Found: C, 52.1) H, 6.3$ N, 3U.1* 30

5~Hydroxy-6,7,8,9 -tetrahydr otetraz olo [b ] quinazoline

In 150 ml, of absolute ethanol were dissolved 1?.0 grams (0.20 mole) of 5-amino tetrazole, 37 .U grams (0,22 mole) of ethyl cyclohexanone—

2-carboxylate and 3 ml, of piperidine. This mixture was heated under reflux for 168 hours, The mixture was then chilled and the solid material separated by filtration and then recrystallized from 50**50 ethanol-isopropyl alcohol, The tan ’solid thus obtained melted at ll{ii-l860C , with decomposition. This material was then recrystallized from 1 0 % aqueous isopropyl alcohol and once more from 50:50 ethanol- isopropyl alcohol at which point 9.7 grams (25.h % of theory) of colorless flat needles were isolated, m.p. 199-200°C. with decomposition.

Analysis: Calculated for Cq Hq I^O: C, 50.2j H, U .7i N, 36.6.

Found: C, 50,0j H, 5.0$ N, 36.6.

Attempted Preparation of 5»7-IHhydroxytetrazolo[ajpyrimidine

The method employed in the attempted synthesis of this compound was essentially identical with that employed for the preparation of most of the monohydroxy compounds. Three milliliters of piperidine were used as catalyst for the reaction of 17.0 grams (0.20 mole) of 5-aminotetra- zple with 32.0 grams (0,20 mole) of diethyl malonate dissolved in 100 mlo of absolute ethanol. The mixture was heated under reflux for a period of 192 hours, at the end of which time it was chilled and the precipitated solid material separated by filtration and then purified by recrystallization from boiling water, using Norit decolorizing carbon. When dried under vacuum at 100°C., the colorless crystalline 31 product, crumbled and turned white and opaque. The dried material melted with decomposition at 201—202°C, and showed the characteristic explosion

of 5>-aminotetrazole when heated above its melting point on a spatula held over an open flame. “When a mixture melting point with 5~amino-

tetrazole was determined, no depression m s observed. The amount of

starting material recovered m s 15*1 grams. No other product could be

isolated.

Acylation of 5-Aminotetrazole

A. Acylation by Carboxylic Acids

5-A c ebylamino t e t raz ole

Seven and four-tenths grams (0.08? mole) of 5“aminotetrazole were

heated with 150 ml. of glacial acetic acid at the reflux temperature

for U8 hours. Crystals formed in the solution during the heating

period. The reaction mixture m s evaporated to dryness on the steam

bath and the dry residue recrystallized twice from boiling mter. Four

grams (36.0$ of theory) of colorless plates melting with decomposition

at 268-269°C. were obtained.

Analysis: Calculated for C3H5N50: C, 28.U* H, U-0; N, 55*1*

Found: C, 28.5i H, l+.lj N, 55*2.

5 -Prop ionylaminotetra z ole

Eight and five-tenths grams (0.10 mole) of 5-aminotetrazole were

placed in a flask with 150 ml. of propionic acid and the flask m s

heated by immersion in an oil bath. The temperature of the oil bath 32 was held by means of a thermostat at 115°C. for 53 hours. "When allowed to cool, white plates formed in the reaction vessel. These were separated by filtration and recrystallized from boiling water. The 3.8 grams of colorless platelets resulting from this treatment melted at

265°C, and represented 27.1# of the theoretical amount.

Analysis: Calculated for C4H6N50: C, 3k.0; H, 5.0; N, k9.6.

Found: C, 3k.0; H, 5.2; N, k9.k.

5 -Ba tyr ylamino t e t r a z 01 e

This reaction was carried out just as was the previous one, except that the reaction mixture was heated to reflux temperature instead of the lower temperature of the oil bath. Eight and five-tenths grams

(0.10 mole) of 5-aminotetrazole were heated in 200 ml. of butyric acid under reflux for 53 hours. The reaction mixture, when allowed to cool, yielded a solid material which was removed from the mixture by fil­ tration and recrystallized from boiling water. The purified product amounted to 6.1 grams ( 3 9 o f theory) and melted with decomposition

at 250°C.

Analysis: Calculated for C5HgN50: G, 38.7$ H, 5.8; N, k5»l»

Found: C, 38.7; H, 5.8; N, k5-2.

5"Piethylac etylaminot etraz o l e

A flask containing 8.5 grams (0.10 mole) of 5-aminotetrazole and

100 grams of diethylacetic acid was immersed in an oil bath maintained

at ll8°C. At the end of 58 hours, the reaction mixture was chilled and the solid material removed by filtration. All of the original 33 charge of 5~nminotetrazole was recovered. The diethylacetic acid was distilled and the reactants were recombined and the flask replaced, in the oil bath. The temperature of the bath was raised to ll40°C. and kept there for I4.8 hours. The mixture was cooled and filtered. The solid product was recrystallized from 50% aqueous isopropyl alcohol.

One and five-tenths grams of product ( 8 , 2 % of theory) were recovered after one more recrystallization from boiling water. The purified material melted at 237-238°C. (1U) and this melting point was not depressed when the material was mixed with a sample of 5-diethylacetyl- aminotetrazole prepared from 5“S-mino tetrazole and diethylacetyl chloride.

B. Acylation by Acid Chlorides or Anhydrides

5>-Propionylamino tetrazole

An 8.5 gram portion (0.10 mole) of 5^minotetrazole in 200 ml. of l,U-dioxane was treated with 19.5 grams (0.15 mole) of propionic anhydride. The mixture was heated under reflux on the steam bath for

I48 hours, then poured into 150 ml. of water and evaporated on the steam bath. Recrystallization from boiling water yielded 3.8 grams

(26,9$ of theory) of colorless platelets which melted at 265°C. with decomposition.

Analysis: Calculated for C4H7N50: C, 3U.0j H, 5*0j N, U9.6,

Found: C, 3U.0j H, 5.0* N, U9-6. 3b

5~Butyrylaminotetrazole

Eight- and five—tenths grains (Q’,10 mole) of 5-aminotetrazole were placed, in a round—bottomed flask fitted with a reflux condenser and treated with 11.7 grams (0*11 mole) of butyryl chloride. After heating for 20 hours by immersion in an oil bath kept at 116°C., the mixture was evaporated on the steam bath. The residue was recrystallized twice from boiling water. The 5.6 grams ( 3 6 , 1 % of theory) of colorless platelets melted with decomposition at 250°C,

Analysis: Calculated for CbHq N50: C, 38.75 H, 5.95 N, 1+5.1.

Found: C, 38,75 H, 6.0; N, 1+5-0.

5-Diethylacetylaminotetrazole

A mixture of 20.1+ grams (0.21+ mole) of 5-aminotetrazole with 28.2 grams (0,21 mole) of diethylacetyl chloride was heated under reflux on the steam bath for eight hours, though solid product appeared to have been formed immediately upon mixing the reactants. When the reaction mixture was filtered and the solid residue recrystallized from boiling water, the yield was 29.5 grams (76.8# of theory) of white plates which decomposed at 238°C . (11+).

5-Benz oylaminotetraz ole

A solution of 8,5 grams (0.10 mole) of 5-nminotetrazole and 13.6

grams (0.10 mole) of benzoyl chloride in 200 ml. of l,l+-dioxane was heated under reflux on the steam bath for 1+0 hours and then evaporated to dryness. The residue was a highly insoluble tan powder. It was not possible to recrystallize this material in the usual fashion due to its 35 insolubility in most solvents. The entire mass was placed in an asbestos thurible in a Soxhlet extraction apparatus and extracted for 72 hours with *~>0% aqueous ethanol. When the solution from the Soxhlet flask was evaporated at the end of this period, only a trace of unreacted 5-a.mino- tetrazole was found to have been extracted.

The pink powder was removed from the asbestos thimble and dissolved in aqueous potassium hydroxide solution, boiled with Norit decolorizing carbon, filtered and acidified. The precipitated white powder when dried melted with decomposition at 280°C. (12). The 10.2 grams finally isolated amounted to 5U*0$ of theory.

C . Acylatlon by Esters in Glacial Acetic Acid

5-Biethylacetylaminotetraz ole

A mixture of 15.8 grams (0.11 mole) of ethyl diethylacetate and

8.5 grams (0.10 mole) of 5-aminotetrazole in 250 ml. of glacial acetic acid was heated at the reflux temperature for 2[+ hours. The crystalline product which separated upon cooling was recrystallized from boiling water. The yield of l+.l grams of white platelets melting at 238°C,

(li+) with decomposition represented 22.1;$ of the theoretical yield.

This material was shown by means of a mixture melting point and by comparison of Infrared spectra to be identical with the material prepared by treatment of 5-aminotetrazole with diethylacetyl chloride. 36

D. Attempted Acylation by Esters Alone

Attempted Preparation of 5-Acety'lamlnotetrazole

Eight and five-tenths grams (0.10 mole) of 5—aminotetrazole were heated under reflux with 26.ii grams (0.30 mole) of ethyl acetate for 72 hours. The reaction mixture was evaporated on the steam bath and the residue was recrystallized from boiling water. The 5-aminotetrazole was recovered quantitatively.

Attempted Preparation of S’rPyopionylaj'rcinotetrazole

The procedure followed in this attempted acylation was the same in every respect as that followed in the preceding case. One-tenth mole of 5-aminotetrazole was treated with two-tenths mole of ethyl propionate.

The ^-aminotetrazole was recovered completely.

Attempted Preparation of 5-Butyrylaminotetrazole

One-tenth mole of 5-aminotetrazole and one-quarter mole of ethyl butyrate were heated under reflux in an oil bath at 116°C. for hours.

At the end of this time, the full amount of 5-amino tetrazole was re­ covered unchanged by evaporation of the reaction mixture followed by recrystallization of the residue from boiling water.

Attempted Preparation of g-Benzoylaminotetrazole

One-tenth mole of 5*^mino'ketrazQle was heated under reflux with

0.15 mole of ethyl benzoate. The mixture was heated at 116°C. (oil bath) for 72 hours, and evaporation of the mixture led to complete recovery of the 5— amino tetrazole. 37

E. Attempted Acylation by Esters In Ethanolic Solution with Piperidine Catalyst

Attempted Preparation of 5~Acetylaminatetraz ole

Eight and five-tenths grams (0,10 mole) of 5>-aminotetrazole and

13.2 grams (0 .1^ mole) of ethyl acetate were heated under reflux with

1 milliliter of piperidine in 100 ml. of absolute ethanol. After 96 hours of heating, the mixture was evaporated and the solid residue recrystallized from boiling water. The 5-aminotetrazole was recovered quantitatively. 1 Preparation of 2-Methylmercaptopyrimidines

2-Methylmercapto-l+~methyl-6-hydroxypyrimidine

The method employed for the synthesis of this compound was adapted from that employed by "Wheeler and Merriam (16) , The amounts of reactants were increased and their contact time lengthened.

To a solution of 103.1+ grams (0.1+7 mole) of S-methylisothiuronium iodide in 100 ml. of water was added at once a solution of 28.1+ grams

(0.5l mole) of potassium hydroxide in 100 ml. of water. The solution changed from yellow to colorless and then to pink. To this was added a 61.8 gram (0 .1+8 mole) portion of ethyl acetoacetate which dissolved in the mixture immediately. After 2l+ hours, long needles could be seen forming in the liquid. The mixture was allowed to stand at room temperature for a total of 1+8 hours and was then filtered . The solid material was recrystallized from absolute ethanol. Thirty-seven grams of product melting at 219°C. (16) were obtained. This yield was 50.0$ of theory. 38

reap to -I4 j 5 imethyl-6 —hydr oxypyr imid ine

Seventy and four-tenths grams (0,32 mole) of S-methylisothiuronium iodide were added in one portion to a solution of 18.7 grams (0.33 mole)

■of potassium hydroxide in 60 ml. of water. "When this had been dissolved,

Il.6,5 grams (0.32 mole) of ethyl a-methylacetoacetate (18) were added with enough ethanol (20 ml.) to bring about complete solution of the

ester in the aqueous phase. After standing at room temperature for

72 hours, the mixture was chilled and filtered. The solid product was recrystallized twice from 50:50 ethanol-isopropyl alcohol. The yield was 10,1 grams (18.of theory) of colorless plates melting at 2l6-217°C,

Analysis: Calculated for CVH 10N 2OS: C, U9.U) H, 5.9) N, 16.5) S, 18.8.

Found: C, 1+9 -Uj H, 5.9) N, 16.5) S, 17.0.

2 -Metbylmer cap 1 0 -I4-methyl -5-ethyl-6-hydr oxypyr imidine

To a solution of 56.1 grams (1,00 mole) of potassium hydroxide in

100 ml. of water were added 109.0 grams (0.50 mole) of S-methyl-

isothiuronium iodide followed by 79.0 grams (0.50 mole) of ethyl

a-ethylacetoacetate (18). Seventy ml. of ethanol were added to bring

about solution of the ester and the mixture was allowed to stand over­

night. After 9 hours at room temperature, the solution was brought to

its boiling point on the steam bath and. then cooled. The precipitate

which formed upon acidification to pH 2 with concentrated hydrochloric

acid was removed by filtration and then recrystallized from absolute

ethanol. Fourteen and five-tenths grams of product (15.7$ of theory)

melting at 201-202°C. (16) were obtained. 39

2~MethyImer capto^H-methyl-5-n^r opyl-6-h^ydr oxypyr imidine

Seventy-rive and eight-tenths grams (0.35 mole) of S-methyliso- thiuronium iodide and 59*9 grams (0.35 mole) of ethyl a-n-propylaceto- acetate (18) were added to a solution of 29.3 grams (0.52 mole) of potassium hydroxide in 50 ml.'of water with 50 ml. of ethanol added to dissolve the ester. The mixture was left overnight at room temperature.

After 9.5 hours, the reaction mixture was brought to its boiling point

on the steam bath and held there for 1+5 minutes. The cooled solution was treated with concentrated hydrochloric acid until it had been brought to pH 2, when the solid material was separated by filtration

and purified by recrystallizing twice from absolute ethanol. The yield

from this preparation was 3.8 grams of product (5.5$ of theory) which

melted at l8l-l82°C.

Analysis: Calculated for C9H ly

Found: C, 5H.5* H, 7.2* N, 13.9* S, 16.-0,

Attempted Preparation of 2-Methylmercapto-l4-niethyl-5",tsopropyl-6- hy^roa^yrimidine

To a solution of 29,3 grains (0.52 mole) of potassium hydroxide in

50 ml. of water were added 75.8 grams (0.35 mole) of S-methyl-iso-

thiuronium iodide and 59-9 grams (0.35 mole) of ethyl a-isopropylaceto-

acetate (18) with sufficient (50 ml.) ethanol to cause solution. After

standing overnight for 9.5 hours at room temperature, the mixture was

brought to its boiling point on the steam bath and held there for 1+5

minutes. After this heating period, the mixture was cooled and

acidified to pH 2 with concentrated hydrochloric acid. The precipitated Uo solid was removed by filtration and was triturated three times with 30 ml. each time of boiling absolute ethanol. The alcohol was evaporated and no product was obtained.

2-Methylmercapto-UHnethyl-5~n-butyl-6-hydroxypyrimidine

One hundred and nine grams (0,50 mole) of S-methylisothiuronium iodide and 93.1 grams (0.50 mole) of ethyl a-n-butylacetoacetate (18) were added to a solution containing U2.1 grams (0.75 mole) of potassium hydroxide in 100 ml. of waterj 100 ml, of ethanol were added to dissolve the ester. After standing for 72 hours at room temperature, the mixture was cooled and acidified to pH 2 with concentrated hydrochloric acid.

The precipitated solid was collected by filtration and then recrystallized three times from absolute ethanol. The purified product melted at

159~160°C. and weighed 9.5 grams (8,9$ of theory).

Analysis: Calculated for C10H 16N3OS: C, 56.6j H, 7.6j N, 13.2) S, 15.1.

Found: C, 56.6) H, 7.6) N, 13.U) S, 15.1.

2-Methylmercapto-U-hydroxy-5.6,7»8-tetrahydroquinaz oline

Thirty-seven and four tenths grams (0.67 mole) of potassium

hydroxide were dissolved in 100 ml, of water and to this solution were

added 72.7 grams (0,33 mole) of S-methylisothiuronium iodide and 56.?

grams (0,33 mole) of ethyl cyclohexanone-2-carboxylate with 100 ml. of

ethanol to bring about solution of the ester in the reaction mixture.

After standing for 72 hours at room temperature, the mixture was

chilled and brought to pH 2 by addition of concentrated hydrochloric

acid. The solid resulting from filtration of this mixture was Hi recrystallized twice from absolute ethanol, The 17• 7 grams of color­ less needles obtained melted at 218.0—218,5^C. and corresponded to

27.1$ of theory.

Analysis: Calculated for C9H 12H3'0S: C, 55.1) H, 6.2) N, lH.3) S, 16.3.

Found: C, 5H.9j H, 6.Hi N, lH.3i S, 16.2.

2-Methylmer capt Q-H-phenyl-6-hydrox^yr iriid ine

A thirty gram (O.lH mole) portion of S-methylisothiuronium iodide was dissolved in a solution of 16.0 grains of potassium hydroxide in 80 ml. of water. this were added 2H.0 grams (0,12 mole) of ethyl benzoylacetate. Twenty milliliters of ethanol were added, to cause complete solution of the ester in the reaction mixture. After standing at room temperature for 36 hours, the mixture was placed on the steam bath and allowed to reach the boiling point." Cooling of the mixture followed by acidification to pH 2 with concentrated hydrochloric acid caused the precipitation of a quantity of solid material which was purified by recrystallization from absolute ethanol. Three and seven- tenths grams of product (13.6$ of theory) melting at 238°C. were obtained. "Wheeler and Merriam (16) reported that their preparation melted at 2H0°C.

Attempted. Preparation of 2-Methylmercapto-H, 6-dihydroxypyrimidine

Fifty-seven and eight-tenths grams (1.03 moles) of potassium hydroxide were dissolved in 100 ml. of water. To this solution were added 112.3 grams (0.52 mole) of S-methylisothiuronium iodide, 85.H

grams (0.52 mole) of diethyl malonate and enough ethanol to cause solution (HO ml.). The mixture m s .allowed to stand for 12 hours at room temperature and was then brought to its boiling pointy cooled and acidified to pH 2 with concentrated hydrochloric acid« The precipitated material was extracted with 200 ml. of hot absolute ethanol. When no crystallization occurred upon cooling the extract, the alcohol was evaporated. Only an extremely thin film of material remained on the bottom of the beaker when the alcohol had been completely evaporated.

Hydrazinolysis of 2-Methylmercaptopyrimidines

2 -Hydraz ino -U-methyl-6-hydr oxy pyr imid ine

A solution of 10.5 grams (0.067 mole) of 2-methylmercapto-i;-methyl-

6-hydr oxypyr imid ine in 150 ml. of ethanol was treated with 33.7 grams of aqueous 85$ hydrazine hydrate solution containing 0.57 mole of hydrazine. This mixture was heated on the steam bath with stirring.

After eight hours, the reaction mixture was chilled and filtered.

Recrystallization from boiling water yielded I4.O grams ([4.2 .6$ of theory) of creamy-white crystals which melted at 230.5-231 C. with decomposition.

Analysis: Calculated for C5H8N4P: C, i+2*85 H, 5-8j N, I4O.O.

Found: C, 1+3.13 H, £-7$ N, 39.8.

2 -Hydraz ino-U,5 -dime thyl-6-hydr oxypyr imidine

This substance was synthesized by two methods. The first was substantially the same as that used in the preparation of the preceding compound in which an aqueous solution of hydrazine hydrate was eirployed.

The second method involved the use of anhydrous hydrazine; The yield was notably lower in the latter case. 1+3

Four and three-tenths grains (0.025 mole) of 2-methylmercapto-l+,5” dimethyl—6-hydr oxypyr imid ine in 75 ml. of ethanol were treated with

12.65 grams of 85$ aqueous hydrazine hydrate solution containing 0.2 mole of hydrazine. This mixture was stirred under reflux on the steam bath until evolution of methyl mercaptan ceased after 60 hours. At this time, the solution was chilled and the precipitated solid recrystallized from ethanol. The yield of product was 1.6 grams, m.p.

333^0 . with decomposition, corresponding to 1+1$ of theory.

In the second case l+.l grams (0.021+ mole) of 2-methylmercapto~l+,5- dimethyl-6-hydroxypyrimidine in 150 ml. of absolute ethanol were heated with stirring under reflux on the steam bath with 8.2 grams of anhydrous

(95$) hydrazine containing 0.21+ mole of hydrazine. After 28 hours the

mixture was evaporated and the residue was recrystallized from ethanol.

Only 0.7 gram (18.9$ of theory) of product was obtained. The material

was identical with that prepared by the other method.

Analysis:Calculated for C6H loN4 0 : C, 1+6.73 H,6 ,5j N, 36.3.

Found: C, 1+6.53 H, 6.63 N, 36.3.

2 -Hydrazin 0 -1+ -methyl -5 -ethyl-6-hydr oxypyr imid ine

A solution of 1.8 grams (0.01 mole) of 2-methylmercapto-l+-methyl-

5-ethyl-6-hydroxypyrimidine in 25 ml. of absolute ethanol was treated

with 3.3 grams of anhydrous (95$) hydrazine. The mixture was stirred

under reflux on the steam bath for 36 hours then evaporated to dryness.

Tne solid material was recrystallized three times from absolute ethanol,

yielding 0.3 gram (18.3$ of theory). The purified material melted with slight decomposition at 231,5 C,, resolidifying to melt a second time

■with extensive decomposition at 320°C.

Analysis: Calculated for C7H 13N40 i C, 50.0j H, 7.2* N, 33.3.

Found: C, 50.2| H, 7.3j N, 33.5.

2 -Hydraz ino -U-methyl-5-n--pr opyl—6-hydr oxypyr imidine

Ten grams of an 85$ aqueous solution of hydrazine hydrate contain­

ing 0.17 mole of hydrazine were added to a solution of 3.35 grams

(0.017 mole) of 2-methylmercapto-l+-methyl-5-n-propyl-6-hydroxypyrimidine in 30 ml. of ethanol. The mixture was stirred under reflux on the

steam bath until methyl mercaptan ceased to be evolved in large amounts.

After 30 hours, the mixture was chilled and filtered. The residue was

recrystallized from absolute ethanol and then from 50$ aqueous iso­ propyl alcohol and once more from ethanol. When heated slowly, the

material sintered and yellowed slightly at 2l5°C., then rehardened to

melt again at 323°C. with decomposition. When heated more rapidly, it

melted at 215-216 C. and resolidified to melt with extensive decompo­

sition at 323°C. The yield of 2,1 grams of product was 6 7 .8$ of theory.

Analysis: Calculated for C8H 14N40: C, 52.73 H, 7.73 N, 30.8.

Found: C, 52.8j H, 7.83 N, 30.8.

2 -Hydraz ine -H-me thyl-5-n-bu tyl-6-hyd r oxypyr imid ine

To a solution of 9.0 grams (0.01+2 mole) of 2-methylmercapto-l+-

methyl-5-n-butyl-6-hydroxypyrimidine in 30 ml. of ethanol were added

25.0 grams of an 85$ aqueous solution of hydrazine hydrate containing

0.1+2 mole of hydrazine. The mixture was stirred and heated under reflux 1*5 on the steam bath for 57 hours, Tnlhen cooled and filtered the reaction mixture yielded a tan solid ■which "was purified by recrystallization once from ethanol and three times from 50$ aqueous isopropyl alcohol, giving 1.3 grams ( 1 $ . 7 % of theory) of product which melted at 201~202°C.

Analysis: Calculated for C9H 16N40: C, 55.13 H, 8.2* N, 28.6.

Found: C, 55.33 H, 8.1*3 N, 28.8.

2-Hyd razino ~l4.~h.yd r oxy "5 >6,7,8-1 etrahydr o qu inaz oline

Ten grams (0.05l mole) of 2-methylmercapto-l*-hydroxy-5,6,7* 8- tetrahydroquinazoline in 50 ml, of ethanol were treated with 30.0 grams of 85$ aqueous solution of hydrazine hydrate containing 0.51 mole of hydrazine and stirred under reflux on the steam bath for 21; hours at the end of which time the rate of evolution of methyl mercaptan was vastly less than when the reaction first began. Chilling the reaction mixture caused the separation of a quantity of solid material which was separated by filtration and recrystallized three times from ethanol.

Tne amount of pure product melting at 32U°C. withcfecopposition was 3.8 grams (1*1 .3$ of theory),

Analysis: Calculated for CaH 12N40: C, 53.33 H, 6.73 N, 31.1.

Found: C, 53.2* H, 6.83 N, 31.1*.

2 -Hydra-zino -4*-phenyl-6-hydr oxypyr imidine

A solution consisting of 3.7 grams (0.017 mole) of 2-methylmercapto-

1* -phenyl-6 -hyd r oxypyr imid ine and 5.7 grams of anhydrous (95$) hydrazine

(0.17 mole) in 50 ml. of absolute ethanol was stirred under reflux while heated on the steam bath for 20 hours. The reaction mixture was U6 evaporated to dryness and the residue was recrystallized once from ethanol and twice from 30$ aqueous isopropyl alcohol (the last time * using Norit decolorizing carbon) but the crystalline product retained a slight yellowish tinge. The product, 1.2 grams (35*3$ of theory), melted at 219-219.5°C. with slight decomposition.

Analysis: Calculated for C10H 10N40: C, 59 .J+j H, $ >0; N, 27.7.

Found: C, 59.6j H, 5.0$ N, 27.7.

2-Hydrazino-li,6-dimethylpyrimidine

Twenty and nine-tenths grams (O.lU mole) of 2-methylmercapto-l4,6-

dimethylpyr imid ine prepared according to the method of 'Wheeler and

Jamieson (15) were dissolved in 150 ml. of absolute ethanol and to this

solution were added 2-5.0 grams of 85$ aqueous hydrazine hydrate solution

containing 0.U2 mole of hydrazine. After stirring and heating on the

steam bath for 12 hours, the mixture "was chilled. One and five-tenths

grams of solid material melting at 270°C. with decomposition was

separated by filtration. The filtrate was combined with an additional

0.51 mole of hydrazine (30.0 grams of 85$ aqueous hydrazine hydrate

solution) and heated under reflux with stirring for 2h hours. The

mixture was then evaporated and the residue recrystallized twice from

ethanol had a melting point of 165°C. The yield of this material was

1.6 grams, representing 8,5$ of theory.

Analysis: Calculated for CgH-LoH^O: C, 52.2j H, 7 »3 3 N, ij.0,6.

Found (165°C,-melting product): G, 52. Oj H, 7«2j N, U0.8. U7

The high-melting material was dissolved in water by addition of glacial acetic acid to pH I4., filtered and reprecipitated by addition of ammonium hydroxide solution to pH 8 * The product was washed first with water, then with ethanol. The melting point of this material was determined to be 271-271.5°C. (decomposition) and elemental analysis corresponded to an empirical formula C^f^N^. This substance was not

investigated further.

Preparation of Benzal Derivatives of the 2 -Hydraz in opyr imid ines

2 -B enzalhydraz ino -U-methyl -6-hydr oxypyr imid ine

One and one-tenth grams (0.010 mole) of benzaldehyde were dissolved in 5 ml. of ethanol and 0.60 grams (0.010 mole) of glacial acetic acid.

\ Water was added until the solution became faintly cloudy. To this mixture was added 0.7 gram (0.005 mole) of 2-hydrazino-I4-methyl-6- hydr oxypyr imid ine. This mixture was heated on the steam bath until

evaporated to dryness. The residue m s recrystallized three times from absolute ethanol, yielding 0.5 gram (li3»8$ of theory)j m.p. 228-229°C.

Analysis: Calculated for C 12H 12N40: C, 63.13 H, 5*3i N, 2I4..6 .

Found: C, 62.93 H, 5 N, 23.6.

2-Benzalhydraz ino-U » 5 -dimethyl-6-hyd roxypyr imid ine

This material was prepared exactly as was the previous one. Five-

tenths of a gram of 2 -hyd raz ino -U, 5-d imethyl-6-hydr oxypyr imidine was used. The product was recrystallized twice from ethanolj yield,

0.25 gram (3 1 .6$ of theory)3 m.p. 2Ul-2U2°C. U8

Analysis? Calculated for C13H14N40: C, 61;. Uj H, 5.8* N, 23.1.

Found: C, 61;.2* H, 5.9* N, 23.0.

2-Ben^alhyd raz in 0 -1; -"me t hryl~^"&thyl"6~hydroxyp^irn.id|ine

One-tenth gram (0,0006 mole) of 2—hydraz ino-1;-methyl-5-ethyl-6- hydr oxypyr imid ine was treated as in the previous two examples. The product was recrystallized three times from absolute ethanol* yield,

0.025 gram (16.7$ of theory)* m.p. 228-229°C.

Analysis: Calculated for C 14H 16N40: C 9 65.6* H, 6,3J N, 21.9.

Found: C, 65.83 H, 6.3* N, 21.7.

2 -B enzalhydraz ino -U-methyl-^-n-pr ppyl-6-bjydr oxypyr imid ine

A 0.50 gram (0.0027 mole) sample of 2-hydraz ino-1;-methyl-5-n-pr opyl-

6-hydr oxypyr imid ine was treated in the same manner as described above.

The product was recrystallized twice from ethanol* yield, 0.25 gram

(33.8$ of theory)* m.p. 199-199.5°C.

Analysis: Calculated for C 15H 18N40.-jJf H20: C, 61;.5* H, 6.9* N, 20.1.

Found: C, 6 k *0* H, 6.8* N, 20.0.

2 -B enzallhyd raz±no-l;-me thyl -5 -n-butyl-6-lydr oxypyr imidine

In the same fashion as with the other members of this series, 0.50 gram (0.0026 mole) of 2-hydrazino-U-methyl-5-n-butyl-6-hydroxypyrimidine was caused to react with benzaldehyde. The product melted at 192-193°C. after being twice recrystallized from ethanol* yield, 0.20 gram (27.0$ of theory). 1*9

Analysis: Calculated for C16H3ON40: C, 67.6j H, 7.1] N, 19-7.

Found: C, 67 .U] H, 7.2] N, 19.6.

2-Benzalhyd raz ino -U-hy droxy-5 #6 ,7,8 -tetrnhydr o qu inaz oline

Five—tenths of a gram (0,0028 mole) of 2 —hydraz ino -I;-hydroxy-

5 >6,7* 8—tetrahydroquinazoline was treated as described above. The product was recrystallized twice from ethanol] yield, 0.60 gram (80.5$

of theory)] m.p, 22U-225°C. (slight decomposition).

Analysis: Calculated for C15H 16N40: C, 67.1] H, 6.0] N, 20,9.

Found: C, 67.0] H, 5-8] N, I1;.5.

2 -B enzalhydraz ino "U^henyl*6"hydr jjcjypyrimidine

By the same method already described, 0.50 gram (0,0025 mole) of

2-hydrazino-U-phenyl-6-hydr oxypyr Imid ine was allowed to react with

benzaldehyde. The product was recrystallized. twice from ethanol] yield,

O.Ij.0 gram (55.6$ of theory)] m.p. 261-262.5°C.

Analysis: Calculated for C 17H 14N40: C, 70,3] H, U.9] N, 19.3.

Found: C, 70.5] H, U.7] N, 19.3.

2-Benzalh^drazino-U. 6-dimethylpyrimidlne

The non-hydroxyl-bearing pyrimidine of the group was caused to

react as were the others. Five-tenths of a gram (0.0036 mole) of

2-hyd.razino-Uj6-dimethylpyrimidlne was used] yield, O.I4.O gram (35»U$

of theory) ] m ,p. l60°C.

Analysis: Calculated for C 13H 14N4 : C, 69.0] H, 6,2] N, 2J4..8 ,

Found: C, 68.8] H, 6.2] N, 2U.9. 5o

Diaz otization of 2 —Hydraz inopyr imidines

5-Hydr oxy-7~methyltetraz olo [alpyrimidine

Into a solution of 5 ml. of concentrated hydrochloric acid (0.058 mole) in 30 ml. of water were placed U.O grams (0.029 mole) of

2-hydraz ino-U-methyl-6-hydr oxypyr imidine, This solution was mechanically stirred in a beaker immersed in an ice bath, A saturated solution of sodium nitrite in water was added dropwise until the first excess of nitrous acid was indicated by the starch-potassium iodide paper end­ point. Stirring was continued in the cold for 15 minutes, then solid sodium carbonate was added until the pH of the mixture was 8. At this point, the solid material which had formed in the solution during the addition of the sodium nitrite solution dissolved. The ice bath was removed and the mixture was allowed to stand overnight at room tempera­ ture. After 9 hours, the mixture was brought to pH 5 by the addition

of concentrated hydrochloric acid, upon which solid material separated

from solution. The mixture was cooled and filtered and the solid product recrystallized from boiling water. The product crystallized as colorless needles which were identical with the compound synthesized

from 5"^sirriinotetrazole as evidenced by determination of melting point

and mixture melting point and by comparison of infrared spectra of the

two samples. The yield from this reaction was 2.3 grams (52.3 of

theory) of product, m.p. 2U7°C. 51

5.-Hydroxy-6,7“dimethyltetrazolo [ajpyrimidine

One and six-■tenths grams (O.Oil mole) of 2—hydr az ino ~h, 5-dimethyl- tetrazolo [ajpyrimidine were dissolved in a solution of 2 ml, of concen­ trated hydrochloric acid (0,023 mole) in 10 ml. of water. The solution was stirred in an ice bath while saturated sodium nitrite solution was added until the first excess of nitrous acid was indicated by the starch-potassium iodide endpoint. After fifteen minutes of stirring, the mixture was made basic by addition of solid sodium carbonate to pH 8, The ice bath was removed and stirring was continued for an hour and a half, at the end of which interval the mixture was acidified to pH 5 by the addition of concentrated hydrochloric acid, chilled and

filtered. The solid residue was recrystallized from boiling watery yield, 1,0 gram (55»6$ of theory) of colorless needles, m.p. 226 C,

(decomposition). Mixture melting point and infrared spectrum demonstrated,

this product to be the same compound as that synthesized from 5-amino-

tatrazole.

5-Hydr oxy-6-ethyl-7 -methyltetraz olo [ a ]pyr imidine

Into a 10 ml. beaker immersed in an ice bath were placed 0.10 gram

(0.0006 mole) of 2 -hyd raz ino -1;-methyl-5-ethyl-6-hydr oxypyr imid ine and

1.5 ml. of concentrated hydrochloric acid dissolved in 2.5 ml. of water.

Saturated sodium nitrite solution was added dropwise until the first

excess of nitrous acid was indicated by the starch-potassium iodide

endpoint. After 15 minutes in the ice bath, the mixture was made basic

(pH 8) by addition of solid sodium carbonate and allowed to come to

room temperature. After two and a half hours, the solution was chilled 52 and brought to pH 2 with concentrated hydrochloric acid. The solid formed was separated by filtration and recrystallized from ethanol.

The yield was O.OUU gram (1+0 ,0$ of theory) of long, colorless needles, m.p, 182-183°C., which were shown by mixture melting point determination and by infrared spectrum to be the same material as that prepared from

5-aminotetrazole.

5-Hydroxy-6-n-propyl-7-methyltetrazolo[a1pyTimldine

Four-tenths of a gram(0.0022 mole) of 2-hydraz ino-l+-methyl-5~n- propyl-6-hydroxypyrimidine was added to a solution of 1+ ml. of concen­

trated hydrochloric acid in 10 ml. of water and the solution stirred in an ice bath while saturated sodium nitrite solution was added dropwise until the first excess of nitrous acid was indicated by starch-potassium

iodide paper. After 15 minutes, the mixture was made basic (pH 8) by

addition of solid sodium carbonate and allowed to come to room temper­

ature . After an hour and a half, the mixture was acidified to pH 2

with concentrated hydrochloric acid and chilled. The precipitated

solid material was separated by filtration and recrystallized from

ethanolj yield, 0,25 gram (59.5$ of theory) of product, m.p. lU5°C,

Mixture melting point determination and comparison of infrared spectra

revealed that this material was identical with that prepared from

5-aminotetrazole.

5-Hydr ox^-6-n-butyl-7~methyltetrazolo [a ] pyrimidine

A solution of 0.30 gram (0.0015 mole) of 2-hydraz ino-l+-methyl-

5-n-butyl-6-hydroxypyrimidine in 10 ml. of water and 3 m3-, of 53 concentrated hydrochloric acid was treated with saturated sodium nitrite solution until an excess of nitrous acid was indicated by starch- potassium iodide paper. Stirring in the cold was continued for 15 minutes, then solid sodium carbonate was added (pH 8) and the mixture allowed to warm to room temperature, After an hour and a half of stirring at room temperature, the reaction mixture was acidified to pH 2 with concentrated hydrochloric acid., chilled and filtered. The residue was recrystallized from boiling water j yield, 0.20 gram (62.5^ of theory) of colorless needles, m.p. l5l-l52°C., which were shown to be identical with the material prepared from 5-aminotetrazole. The melting points and mixture melting points as well as the infrared spectra of both preparations were identical.

5-Hydr oxy-6, 7 > 8,9-tetrahydrotetraz olo [b ] quinaz oline

To a solution of 6 ml. of concentrated hydrochloric acid in 10 ml.

of water was added 0.60 gram (0.0033 mole) of 2-hydrazino-U-hydroxy-

5, 6,7, 8-tetrahydr oquinazoline , This mixture was stirred in an ice bath

while a saturated solution of sodium nitrite was added dropwise until

tbe first excess of nitrous acid was indicated by starch-potassium

iodide paper. After fifteen minutes, the cold mixture was made basic

(pH 8) with solid sodium carbonate and allowed to come to room temper­

ature. The solution was stirred at room temperature for one and a half

hours and then brought to pH 2 by addition of concentrated hydrochloric

acid, chilled and filtered. The residue was purified by two recrystal­

lizations from ethanolj yield, 0.20 gram (31.2$ of theory)5 m.p. 199°C. 5k

This product was shown by means of mixture melting point determination and by comparison of infrared spectra to be identical with the compound prepared from 5-aminotetrazole and ethyl cyclohexanone-2-carboxylate.

5-Hydrox3r~7-phenYltetrazolo[a3pyrimidine

Four—tenths of a gram (0.002 mole) of 2-hydraz ino-L;-phenyl-6- hydr oxypyr imid ine was suspended in a solution of 1,7 ml, of concentrated hydrochloric acid in 20 ml, of water and stirred in an ice bath while saturated sodium nitrite solution was added dropwise until the first indication of excess nitrous acid was noted by the use of starch- potassium iodide test paper. The mixture was made basic (pH 8) by adding solid sodium carbonate after 15 minutes. The mixture of liquid and Suspended solid was then stirred for one and a half hours at room temperature, chilled and acidified to pH 2 with concentrated hydrochloric acid. The solid material was removed by filtration and recrystallized from ethanolj yield, 0,30 gram (70,U$ of theory) of a. product, m.p.

22i4.-225°C. (decomposition), identical with the one prepared from

5-aminotetrazole, as demonstrated by a mixture melting point determin­ ation and comparison of infrared spectra.

5 » 7-Diineth.yltetraz olo [alpyriniditie

A solution of 0.30 gram (0.0022 mole) of 2-hydrazino-1+,6-dimethyl- pyrimidine in 10 ml. of water with 2 ml. of concentrated hydrochloric acid was chilled in an ice bath and stirred mechanically as a saturated solution of sodium nitrite was added dropwise until the first excess of nitrous acid was indicated by starch-potassium iodide paper. 55

After 15 minutes of stirring at ice bath temperature, the mixture of liquid and solid was made basic (pH 8) by addition of solid sodium

carbonate and then stirred for two and a half hours at room temperature.

The reaction mixture was neutralized with concentrated hydrochloric

acid, chilled and filtered, The solid residue was recrystallized from

ethanol j yield, 0,10 gram (31.2$ of theory) m.p, l5l-l52°C, The product

was shown to be identical with the compound obtained from 5-s-minotetra-

zole and acetylacetone by mixture melting point determination and

comparison of infrared spectra.

Other Reactions

Attempted Hydrogenation of 5 -Hydroxy-7 -methyltetraz olo[a] pyr imid ine

Three grams (0.02 mole) of 5-hydroxy~7-methyltetrazolo[a]pyrimidine

were dissolved in 150 ml, of $ 0 % aqueous ethanol containing 1.8 grams

(0,032 mole) of potassium hydroxide. This solution was placed in a

Parr hydrogenation flask with 150 mg, of platinum oxide catalyst and

shaken for 20 hours at room temperature under a hydrogen pressure of

1+9.5 p.s.i. The catalyst was removed by filtration and the clear,

colorless solution was acidified with concentrated hydrochloric acid.

The white powder which precipitated was separated by filtration and

washed with water. Recrystallization of the material and mixture melt­

ing point determination revealed it to be unreacted starting material.

H^ydro ^enolysis of 5-Hydroxy-7 -methylt etraz olo [a ]pyr imidlne

Three grams (0.02 mole) of 5~hydro;xy-7-methyltetrazolo[a]pyTimidine

and 175 mg * of platinum oxide were placed in a Parr hydrogenation flask 56 with 150 ml. of glacial acetic acid, and shaken at 65°C. for 2l+ hours under a hydrogen pressure of 1+9 p*s.i. After removal of the catalyst by filtration of the hot solution, the solvent was evaporated and the

residue was reciystallized from boiling water. The product was a white

powder which melted with decomposition at 297°C. Elemental analysis of

the compound gave an empirical formula that suggested the loss of two

atoms of nitrogen and the possibility that 2-amino-l+-methyl-6-hydroxy-

pyriinidine had been formed. A sample of the latter was prepared by the

method, of Jaeger (8) and was found to be identical with the hydro genolysis

product.

Analysis: Calculated for C5H7N30: C, 1+8.Oj H, 5.6j N, 33.6.

F o u n d : C , 1+8 . l j H , 5 .85 IT, 3U.U.

Infra-red absorption spectra

The infra-red absorption spectra were obtained using a Perkin-Elmer

Recording Spectrophotometer, Model 21. All compounds were run as Nujol

mulls. 57

SUMMARY

1. Early work on tetrazolo [a]pyrimidines has been repeated and an error

discovered in one instance, The compound reported as 5-hydroxy-7~

phenylt etraz olo [ajpyrimidine was shown to be 5-acetylaminotetrazole .

2. The reactivity of the amino group of 5-aminotetrazole with carboxyl

and carbethoxy groups has been examined. 5-Acylaminotetrazoles are

formed when 5-aminotetrazole is heated with carboxylic acids but not

upon heating with the esters alone. Acylation of 5-aminotetrazole

was observed on heating with esters in glacial acetic acid solution,

possibly due to an acyl group exchange between the esters and acetic

acid.

3. A series of tetrazolo [a jpyrimidines has been prepared from 5-amino­

tetrazole by interaction with a-alkylaeetoacetic esters,

U. A proof of the existence of the tetrazolo[ajpyrimidine nucleus has

been accomplished through an alternate method of synthesis from

2-hydrazinopyrimidines by diazotization of the hydraz ino group and

cyclization of the resulting azidopyrimidines.

5. Members of this series of compounds have been submitted for screen­

ing as possible purine antagonists and as central nervous system

stimulants. 58

LITERATURE CITED

1. C. Bulow, Ber., ]£, I4J4.29 (1909).

2. to. J. S. De-war, J. Chem. Soc., (19hU) 615.

3* V. Ettel and J. Nosek, Collection Czechoslov. Chem. Commans., 15 335 (1950)1 C. A., 1951:3853b.

U- W. G. Finnegan, R. A. Henry and E. Lieber, J. Org. Chem., 18, 779 (1953).

5. R. A. Henry and ¥. G. Finnegan, J, Am. Chem. Soc., 76, 923 (195U).

6. R. A. Henry and W. G. Finnegan, J. Am. Chem. Soc., 76* 926 (195U)•

7* R. M. Herbst and J. A. Garrison, J. Org. Chem., 18, 9Ul (1953).

8. J. Jaeger, Ann., 262, 365 (1891).

9. G. W. Kirsten and G. B. L. Smith, J. Am. Chem. Soc,, 58, 800 (1936).

10. F. C. Naehod and E. A. Steck, J. Am. Chem. Soc., 70» 2819 (19U8).

U . A. M. Patterson and L. T. Campbell, "The Ring Index," Reinhold Publishing Corporation, New York, 19l|0, p. Ill,

12. R. Stoll6 and F. Henke-Stark, J. prakt. Chem., 12U , 261 (1930).

13. R. Stoll6 and 0. Orth, Ber., £8, 2100 (1925). lU. R. StollS and 0. Roser, J. prakt. Chem., 136, 3lU (1933).

15. H. L. Wheeler and G. S. Jamieson, Am. Chem. J., 3,2, 3h2 (I90U).

16. H. L. Wheeler and H. F. Merriam, Am. Chem. J., 2£, b?S (1903).

17. F. C. Whitmore, "Organic Chemistry," D. Fan Nostrand Co., Inc,, New York, 1951, ed. 2, p. 181+.

18. J. Wislicenus, Ann., 186, l6l (1877). APPENDIX

7 -dimethyltetraz olo [ajpyrlmidine. olo -dimethyltetraz 7 5-Hydroxy-6 of Spectrum Infrared 2, Figure } aeegh (microns) Wavelength CO o O

ocm tio^ssxuxsTreaj; q.usojsj Q

co Wavelength Wavelength (microns) Figure i|. Figure i|. Spectrum 5-H7droxy-6-n-propyl-7-methyltetrazolo[a]pyrijnidiiie. of Infrared

O O Q oo

HOTS STIUSTTBJqfiXdOJ&d 100 0Q‘ O oSfUte: q. s,l is a s .u q uofSSfiUBtreo:! s s a- o CO 62* I •H $ H rn & o Pi o © © bO L i ■— *H •S •S I—1 •g -P ___ rH v£> u\ "LA -p r£> g 0 cd I o o ■? I N •H <+H P -p T T5 CO ? f I I © fi © p* o I © o I h 100 opstsrj q.uaojsd uorpssftusireji 65

Wavelength (micrcns)

Figure 6. Infrared Spectrum of 5'flydroxy-7-phenyltetrazolo[a]pyrimidine. OJ

Q

CO Wavelength Wavelength (microns) Figure 7. Infrared Spectrum of 5-Hydroxy-65 7> 8,9-tetrahydrotetrazolo [bjquinazollne. 8,9-tetrahydrotetrazolo 7> Figure Spectrum 5-Hydroxy-65 Infrared of 7.

O Q CO Q CNJO O

ttofssTutsxraij, cpjsOvTO^ 100 CQ ospirsirea'j; uofssp CM o CM CO CM O 67 Wavelength (microns)

Figure 8. Infrared Spectrum of 5,7-DimethyltetrazoloWpyrimidine.