Patented Nov. 27, 1951 2,576,31

UNITED STATES PATENT OFFICE 2,56,31 METHOD OF REDUCING AND BY DRO GENATING CHEMICA, COMPOUNDS BY REACTING WITE: ALUMNUM-CONAN NG BYOFREDES Hermann E. Schlesirager and Albert E. Finholt, Chicago, Ill.; said Schlesinger assignor of one fourth to. Edaa, M. Schlesinger and said Fin holt assignor of one-fourth to Marion H. Finholt No Drawing. Application June 3, 1947, Serial No. 752,286 2 (Cairns. (C. 260-638) 2 This invention relates to methods of making LiAlH4. Although this new compound will be aluminum-containing hydrides and the reactions called lithium aluminum hydride in the present thereof, and also relates to products prepared by application, it may also be called lithium alumi said methods. nohydride or lithium tetrahydroaluminide. In This application is a continuation-in-part of one method of making lithium aluminum hydride, our copending application Serial No. 717,312, filed lithium hydride is reacted with an aluminum December 19, 1946, now Patent No. 2,567,972, halide such as aluminum chloride in the presence issued September 18, 1951. of a suitable liquid medium such as an ether. If We have discovered that these compounds, es the reagents are mixed in the proportions of the pecially the ether soluble lithium aluminum hy 0 following equation, or if an excess of lithium hy dride, are extremely useful chemical reagents. dride is used, the reaction proceeds as follows: - They may be employed for replacing halogens or Organic radicals by hydrogen in a great variety 4Li H--AlCl3->LiAlH4--3LiCl of compounds. As a result, their discovery has led to new methods, safer, more convenient, and 16 The liquid medium used is one in which one of more efficient than those hitherto known, for pro the reaction products, e. g., the lithium chloride ducing hydrides of other elements or for pro is insoluble, and the other, e.g., lithium aluminum ducing derivatives of such hydrides, as well as for hydride, is soluble or vice versa. This provides reducing certain types of organic halides to the easy separation of the reaction products. The corresponding hydrocarbons. Furthermore, these 20 preferred liquid is an ether as in the ether the aluminum-containing hydrides are strong re lithium aluminum hydride is soluble while the ducing agents and have been effectively used in lithium chloride is not. After removing the in reducing a great variety of organic compounds. soluble materials, the solvent is removed by Examples are the reduction of carbon dioxide to evaporation leaving the Solid lithium aluminum derivatives of formaldehyde, of esters to alcohols 25 hydride. The solvent may be evaporated first or aldehydes, of nitro compounds to azo con at ordinary temperatures and pressures and pounds, of nitriles to amines, and the like. In finally at higher temperatures under reduced many instances these reductions are more effi pressures. In this reaction three gram equiva ciently and conveniently carried out than with lents of aluminum chloride are reacted with four hitherto used reducing agents. A particular ad- 30 gram equivalents of lithium hydride. The term vantage of the aluminum-containing hydrogen "gram equivalent' means the quotient of the compounds is the specificity of their reactions; gram molecular weight of the compound by the thus, in general they reduce functional groups, product of the valences of the ions of the Com Such as the carbonyl, nitro, and other reducible pound. groups, of compounds containing an unsaturated 35 In carrying out the above reaction, the two carbon to carbon linkage without attacking the solids may first be mixed with each other in a . Carbon to carbon link. suitable apparatus and the liquid solvent then The new hydrides include a new aluminum hy added. In an alternate procedure, the Solid dride-ether complex, alkali metal aluminum hy lithium hydride may be introduced into the re drides, and alkaline earth metal aluminum hy- 40 action vessel and then the aluminum chloride drides. In general, these are prepared by react may be added, preferably as a Solution in the ing an aluminum halide with an alkali metal hy liquid to be used. This latter is the preferred dride or an alkaline earth metal hydride. procedure. It is also preferred that the air be One of the most important of the new hydrides displaced from the reaction vessel by an inert gas is lithium aluminum hydride having the formula 45 such as dry nitrogen. This is not essential, howa 2,576,811 V 3 4. ever, since the reaction has been carried out in ever, to remove all of the ether by evaporation air of ordinary humidity. without decomposing the hydride. If the ether When the reacting materials are mixed, the is removed at room temperature without exten mixture usually becomes warm. Ordinarily, how sive evacuation, the Solid product has a compo ever, this incipient reaction soon stops or ben sition approximating the formula. comes too slow to be readily appreciable. After an induction period, which may be only a few minutes in length or may last for Several hours, the reaction again sets in, usually with Such vigor Its composition, however, depends on the time that cooling of the mixture is necessary. This O and temperature during ether removal. Thus by induction period is undesirable for several rea heating the Solid at 90° C. in vacuo for several sons. It is difficult or impossible to foretell when hours, the composition may reach proportions the vigorous reaction will begin. It is therefore corresponding to 6Al H3 O(Cahs) 2. Irrespective necessary that the reaction mixture be closely of its composition, the Solid is at best only watched in order that the cooling may be begun slightly soluble in ether. Nevertheless, either the before the reaction has become too vigorous for original solution of aluminum hydride or the safety. It has been found that the induction ether insoluble Solids may be used in place of period may be eliminated by adding to the lithium lithium aluminum hydride. hydride a relatively small amount of previously As can be seen from the first and second equa prepared lithium aluminum hydride, preferably 20 tions set out herein, lithium hydride and alumi dissolved in the liquid that is used in the reac num chloride may be reacted together to form tions. When this is done, the reaction proceeds either lithium aluminum hydride or aluminum smoothly on addition of the aluminum halide. hydride. The final product is determined by the Under these conditions, the rate of reaction may proportions of the reacting materials. Thus, to be conveniently controlled by controlling the rate 25 prepare lithium aluminum hydride four moles or of addition of the aluminum halide, which is pref more of lithium hydride are reacted per mole of erably added in the form of a Solution. Among aluminum chloride. If... the final product is to be the preferred solvents are the ethers such as di aluminum hydride, only three moles of lithium ethyl ether, dibutyl ether, dioxane, and any other hydride are reacted per mole of aluminum chlo liquid ether non-reactive toward lithium alumi 30 ride. AS has been pointed out above, it is possible num hydride. For best results, the liduid used to use aluminum halides other than the chloride. should be anhydrous and the aluminum halide It is also possible to use hydrides of alkali metals should be reasonably free from hydrogen halide. other than lithium, or hydrides of the alkaline In all of the operations, moisture should be ex earth metals. cluded although it is not necessary to work under 35 The new compound lithium aluminum hydride absolutely anhvdro is conditions. The alkali is a white solid that is stable in dry air at room metal and alkaline earth metal hydrides that are temperature. It may be heated without appre used should be of good quality. It is preferred clable decomposition to temperatures below 100' that each of these materials be used in a finely . C. in a vacuum. Above 100° C., it decomposes powdered condition, preferably between 100 and 40 slowly, but the rate of decomposition increases 200 mesh. with rise in temperature. At 150° C., the decom Although it is preferred that a solvent such as position can be observed by color changes after an ether be used, this is not absolutely neces a relatively short time. The products of decom sary. The aluminum halide and the hydride may position are lithium hydride, aluminum, and hy be reacted in the absence of a liquid, but the re 45 drogen. The new compound is soluble in diethyl action is sometimes difficult to control. ether to the extent of about 25 grams per 100 Aluminum hydride is closely related to the grams solvent. It is also soluble in other ethers. lithium aluminum hydride in its chemical prop The new compound reacts with water to give erties. Aluminum hydride may be prepared by hydrogen, and either lithium hydroxide and alu reacting aluminum halides with either lithium 50 minum hydroxide, or lithium aluminate. This hydride or lithium aluminum hydride. Any reaction is quite rapid. In spite of this, the com similar hydride of an alkali metal or an alkaline pound does not decompose very rapidly on ex earth metal may be used in place of the lithium posure to air of even fairly high humidity. It compound in producing the aluminum hydride. is believed that this is true because the solid When the reagents are mixed in the proper pro 55 becomes coated with a protective layer of reac portions the reaction of aluminum chloride and tion product. lithium hydride proceeds as follows: In a typical embodiment of the method of making lithium aluminum hydride, 0.02 mole of anhydrous aluminum chloride was mixed with 60 0.50 mole of lithium hydride under dry nitrogen The reaction between aluminum chloride and in a flask. The flask was then attached through lithium aluminum hydride proceeds according to a standard taper to a vacuum System and evacu the following: ated. 15 cc. of anhydrous diethyl ether were ... distilled into the fiask by condensing the ether 3LiAlH4--AlCls->3LiCl-4AlHs 35 in with liquid nitrogen. The mixture was warmed until a reaction occurred. The reaction As can be seen, it is not necessary separately to was allowed to proceed vigorously, but was kept prepare lithium aluminum hydride as the reac under control by cooling the flask with liquid tion may be controlled So that it occurs only as nitrogen from time to time. The total reaction an intermediate product with the reaction con 70 time was approximately five minutes. When the inuing to produce lithium chloride. The above reaction was thus carried out in the vacuum, no eactions are preferably carried out in the pres induction period occurred. . . . ence of a liquid Solvent Such as ether. Most of In another example of making lithium alumi he ether may be removed from the aluminum num hydride, a reaction vessel was used having hydride by evaporation. It is impossible, how 75 three necks to which were, attached a mercury 2,576,836 s S sealed stirrer, a dropping funnel, and a bulb con a solution of 0.547 g. (0.0144 mole) of lithium denser. The open ends of the condenser and the aluminum hydride in 9.10 g. of anhydrous di funnel were protected from moisture by calcium ethyl ether was placed in a reaction vessel which chloride drying tubes. The reaction vessel and had been flushed out with nitrogen. To the Solu its attachments were dried and flushed with dry tion, after further addition of 15 g. of ether, 0.629 nitrogen. Into the flask was placed 25 cc. of a g. (0.00472 mole) of anhydrous aluminum chlo solution containing 10 granas of lithiun alumi -- ride was added. A vigorous reaction occurred, num hydride per 100 grams of diethyl ether. 30 but soon subsided. The precipitated lithium grams of lithium hydride were dropped into the chloride was removed from the solution by filtra solution and the mixture was stirred for a short tion, and the ether was evaporated from the fil time. Through the dropping funnel a solution trate under vacuum conditions, leaving a white, of 100 grams of aluminum chloride and 500 cc. non-volatile solid. The latter was slowly heated of diethyl ether was added slowly with continue in vacuo to about 96° C. at which temperature a ous stirring. The addition rate was so controlled small amount of hydrogen was evolved and the that the boiling in the reaction vessel was kept s white solid started to turn grey. The flask was constant thus showing a Smooth reaction. Stir immediately cooled. The resulting material had ring was continued for a short time after the a composition corresponding to the formula 4.5 addition of aluminum chloride was finished and AH3 O(CHs) and the quantity obtained rep until the reaction appeared to cease. The reases resented a 92% yield of aluminum hydride. tion product was filtered through a sintered glass 2. In the preparation of Sodium aluminum hy disk under a pressure of dry nitrogen to remove dride, sodium hydride is reacted with an alumi the lithium chloride and the excess of lithium nun halide using an ether as a Solvent. In a hydride. The ether was distilled from the filtrate specific preparation, the aluminum halide was at atmospheric pressure until a thick Syrup was aluminum bromide and the ether was dinnethyl formed. The last of the ether was removed 25 ether. As dimethyl ether has a boiling point that under vacuum and by heating the product at is below room temperature, the reaction was carr about 70° C. In general, the yields were from ried out under pressure in order to maintain the 85 to 90% of the theoretical and the purity varied dimethyl ether in the liquid state at room tem from 93 to 98%. perature. In the actual preparation 3.345 g. of In the procedure just described, a Small 30 sodium hydride was mixed with 4.470 g. Of alumin amount of lithium aluminum hydride was added nunn bromide that had previously been freed to the reaction inixture to avoid the induction from hydrogen bromide in vacuo. These were period. When lithium aluminum hydride is not mixed at a low temperature with 15 to 20 cc. of available for this purpose a procedure in all ree liquid dimethyl ether, and the reaction vessel spects like that described above, except that 35 was sealed of and warmed to room temperature. dioxane is used in place of diethyl ether and The quantity of dimethyl ether was such that a that the reflux temperature is higher, may be en considerable annount of the latter renained in a ployed with relatively small quantities of the liquid state at room temperature. The mixture reagent. The solid product resulting from the was stirred for three hours after which the resid ual Solid was renoved from the liquid by filtra removal of the dioxane from the filtered Solution tion through a filter disk. The dimethyl ether may then be used to start the reaction in the was evaporated leaving the Solid sodium alumi procedure described above. In carrying out this nurn hydride (NaAlH4). 0.54 g. of Sodium alu provedure, it is preferred that a small amount minum hydride was recovered, representing a of diethyl ether be added before filtering the re 5 60% yield. action mixture. This is done because the lithiurn 4. The properties of sodium aluminum hydride aluminum hydride is more Soluble in diethyl are like those of the lithium compound except ether than in dioxane. that the sodium compound is somewhat more In a typical preparation of aluminum hydride stable toward thermal decomposition and is Only from lithium hydride according to the following very slightly soluble in diethyl ether. reaction: 5 O The aluminum hydide, alkali metal aluminum hydrides and alkaline earth metal aluminum hy drides may be used to reduce or hydrogenate a Solution of 33.00 g. 0.248 role) of aluminum (terms which are used interchangeably herein) chloride in 70 g. of anhydrous diethyl ether was a great variety of compounds, organic and in added during a 20 minute period to a nitrogen 5 s organic. In setting forth the valuable results filled reaction vessel containing a mixture of 5.90 which may be achieved by means of these sub g. (0.743 mole) of lithium hydride, 0.3 g. of lith stances it is desirable to define certain terms. ium aluminum hydride, and 240 g. of ether. (It An "inorganic reactant' is defined as consisting is to be noted that the relative quantity of alumi 60 of the class of ionizable or hydrolyzable halides num chloride was as nearly as possible that de of metals and of readily hydrolyzable alkyl and manded by the equation, and that a relatively aryl compounds of metals excluding the alkali large amount of ether was used.) The reaction metals but including as metals, in addition to mixture was stirred for One hour after complet those universally so classified, the elements bo ing the addition of aluminum chloride. The pre sron, silicon, arsenic and antimony. cipitated lithium chloride was removed by paSS The term "an organic derivative of an inor ing the solution through a sintered glass disk. ganic reactant" is used to designate a compound, The solution was analyzed and found to contain containing a metal, as defined above, combined approximately 6.3 g. (0.21 mole) of aluminum with one or more halogen atoms and with one hydride, or about 85% of the theoretical. 79 or more difficultly hydrolyzable alkyl or aryl In preparing aluminum hydride from lithium groups, as for example, diethyldichloro silane. It aluminum hydride according to the following is to be noted that the terms inorganic and or reaction: ganic compounds are employed as is customary in chemical literature. 3LiAlHa--AlCl3->4AH3-3LiC 5 The term 'organic reactant' is further defined 2,576,811 7 as a compound in which one or more halogen eral method for accomplishing the desired re atoms are attached (or bound) to a carbon atom, Sult. A second advantage is that the reaction which in turn, is attached (or bound) to hydrogen of the new hydrides is often highly specific. or to groups designated by Ri, R2, R3; if the Thus aromatic nitro compounds may be reduced halogen is iodine, these groups may be any to produce only azo-compounds and nitriles may aliphatic, aromatic, substituted aliphatic or sub be reduced to produce only primary amines. stituted aromatic radical, but when the halogen is Furthermore, in an organic compound which chlorine or bromine the reaction proceeds most also contains an unsaturated carbon-to-carbon favorably when at least one of the groups desig linkage, a reducible functional group may be nated by R1, R2, R3 is an aromatic or an un O reduced without reduction (hydrogenation) of Saturated aliphatic radical. the unsaturated linkage, as occurs, for example, Through the use of the new compounds here in compounds containing an olefinic linkage such in described, inorganic hydrides and their Organic as crotonaldehyde, methyl oleate, allyl bromide derivatives may be prepared by the interaction or sorbic acid, and in compounds containing of the new hydrides with inorganic reactants or 5 acetylenic linkages such as propiolic acid. If, With Organic derivatives of inorganic reactants however, the unsaturated link is activated by its as is illustrated by the generalized equation: position relative to other functional groups, as for example by the phenyl and carboxyl groups (4-ac) LiAlH4-1-4SiRaCl4--> of cinnamic acid, the unsaturated link may be, but (4-ac) LiCl--(4-ac) AlCl3--4SiRHA-e 20 is not necessarily, also reduced. A third advan tage of the use of the new hydrides is that re in which ac may vary from 0 to 3 and R is an alky ductions carried out with them may be effected or an aryl group. Examples of silicon compounds in homogeneous systems, or in substantially thus obtained are: Silicon hydrides, methyl Silicon homogeneous systems. Reaction in a homo hydrides, ethyl silicon hydrides, propyl silicon 25 geneous System means a reaction in which all hydrides, monophenyl silicon hydrides, diethyl of the reacting substances, but not necessarily silicon hydrides, dibutyl silicon hydrides, and the reaction products, are present in a single many others of similar nature. Similar reactions phase, Such as in Solution; reaction in a substan occur with inorganic reactants other than Silicon tially homogeneous system means a reaction in compounds and with their organic derivatives, as 30 which one or both of the reactants, but not in the case of compounds of germanium, tin, necessarily the reaction products, are at least arsenic, antimony and the like. partially soluble in the liquid medium employed. This new method of preparation is far more A fourth advantage of the use of these hydrides convenient than any hitherto known and, in is in the variety of temperatures which may be general, gives better yields. The preferred pro 35 employed to suit the requirements of special cedure is to carry the reactions out in an ether cases. Thus Some reactions, for example the Solution. Such as diethyl ether. In case the de reduction of benzoyl chloride, may be effected sired product has a volatility so nearly that of at temperatures as low as -80° C.; in other cases diethyl ether as to cause difficulty in separating temperatures as high as 65° C. have been em the ether from the solvent, ethers other than the diethyl ether, or other solvents, may be em 40 ployed to accelerate the reactions. The maximum ployed. The reactions may usually be carried out temperature should, however, not be above that at room temperatures but often proceed satis at which the hydrides decompose. For this reason factorily at much lower temperatures or may be the reaction temperature may be stated as lying carried out at any temperature below the boiling approximately between -80° C. and -125° C., point of the solutions or the decomposition ten 45 though with certain of the hydrides temperatures peratures of the new compound. as high as 150° C. might be used. A fifth ad Another example of the use of the new Com vantage in the use of the new hydrides is the pounds is in the formation of hitherto unknown fact they do not ordinarily cause the condensa inorganic hydrides, such as zinc hydride. In tions and the polymerization reactions which this case the inorganic reactant may be either 50 often accompany the use of other reducing zinc chloride or an alkyl-zinc compound. Hy agents; consequently these hydrides in practical drides of beryllium and of aluminum have been ly all cases produce the purer products. obtained by similar reactions. The reductions by the new hydrides are prefer When compounds herein designated as "organic ably carried out in ether solutions, diethyl ether reactants' are treated with the new hydrides, 55 being the preferred ether because of its ready hydrocarbons are formed. Examples are the availability. Other ethers, however, may be used reduction of methyl iodide to methane, allyl when the particular hydride employed or the bromide to propene, and benzyl chloride to compound to be reduced is more soluble in such toluene. Organic compounds, other than those other ethers than in diethyl ether, or if a higher herein defined as organic reactants, may also be 30 temperature than can be attained in the pres reduced, but in Suchi cases reduction does not ence of diethyl ether is desirable. When one of proceed to the hydrocarbon stage. Thus acids, both reactants are only slightly soluble in the esters, ketones, quinones, and other compounds Solvent employed, the latter may be recirculated containing carbon doubly linked to oxygen, i. e., through the materials until the reaction is sub containing a carbonyl group, may be reduced 65 stantially complete. to alcohols; aromatic nitro or nitroso com In many, though not all of the reductions of pounds are reduced to a Zo compounds, aliphatic organic Compounds, the initial reduction product nitro compounds are reduced to amines, as are consists of aluminum and lithium salts of the de nitriles. 70 sired compound. Such salts are formed, for ex The advantages of the new hydrides in the ample, where the ultimate products are alcohols reduction of Organic compounds may be Sun or amines. In such cases, the salt first formed marized as follows: In some instances, as in the is hydrolyzed by water or by aqueous acids or reduction of organic (carboxylic) acids the use aqueous bases to obtain the final reduction prod Of these new hydrides constitutes the only gen 75 licts. 2,576,811 10 The specific reduction of n-heptaldehyde to After the last addition, water was added to de n-heptanol is as follows: stroy the excess hydride. Then 500 cc. of a 20% A two liter flask was equipped with a stirrer, solution of sodium potassium tartrate (a sodium dropping funnel, and a reflux condenser (both hydroxide solution can also be used to dissolve the dropping funnel and reflux condenser were the aluminum hydroxide) was added and the protected with calcium chloride drying tubes). water layer extracted with three 100 cc, portions To a solution of lithium aluminum hydride, pre Of ethyl ether. The ether was removed and the pared from 100 g. of aluminum chloride, 28 g. of . orthoxylylamine collected at 134° C./85 mm. lithium hydride, and 1 liter of diethyl ether, 200 (no 1.5412). The yield was 21.3 grams or 88% g. of redistilled n-heptaldehyde Was added drop O of the theoretical. The benzamide derivative was wise so as to maintain gentle refluxing. One prepared and melted at 88° C. hour after the last addition of aldehyde, 30 cc. The reduction of para-nitrobromobenzene to of wet ether (1 water : 3 ether) was added drop 4,4'-dibromoazobenzene is as follows: wise. The addition of 29 cc. caused the mixture A One-liter three-necked flask equipped with to reflux gently. Then 40 cc. of water was added 5 a rebux condenser, mechanical stirrer, and drop dropwise but no further reaction took place. The ping funnel was used. The condenser and fun mixture was then poured into 300 cc. of ice water nel were protected with calcium chloride drying and acidified with one liter of 10% sulfuric acid. tubes. One-tenth of a mole (20 grams) of para After separation of the ether layer, the aqueous nitrobromobenzene (M. P. 127 C.) was dissolved layer was extracted with two further 100 cc. por 20 in 150 cc. of ether and added dropwise to 0.15 tions of ether. The product obtained after mole of lithium aluminum hydride (in 250 cc. of evaporation of the ether from the dried ether ether). After the last addition, water was added extracts was fractionally distilled. An 86% yield to destroy the excess hydride, and then 150 cc. of n-heptyl alcohol was obtained. of 10% sulfuric acid added to dissolve the alumi The specific reduction of ethyl benzoate to 25 num hydroxide. The azo-compound was insoluble benzyl alcohol is as follows: in water and only slightly soluble in ether and To a solution of 1.5 g. of lithium aluminum remained between the water-ether layers. There hydride in 22 g. of diethyl ether, 12.6 g. of ethyl fore the azo-compound was filtered off and com benzoate was added dropWise. Each drop re bined with the Small amount found in the ether acted vigorously and the Solution became very 30 extract. The compound was washed with hot viscous. No precipitate appeared however. The water and dried in vacuo over calcium chloride. mixture was refluxed 2 hours and was then al The yield of 4,4'-dibromoazobenzene melting at lowed to stand for a day. The mixture Was 203 C. was 15 grams or 88% of the theoretical. poured into water, acidified with hydrochloric The reduction of cetyl iodide to n-hexadecane acid and the ether layer was separated. After is as follows: the ether had been removed by distillation, 50 ml. A one-liter three-necked flask equipped with of 25% NaOH solution was added and the mix a reflux condenser, mechanical stirrer, and drop ture was refluxed for 3 hours. The ether extract ping funnel was used. The funnel and reflux was dried over sodium sulfate, then heated to condenser were protected with calcium chloride remove the ether. The residue, a light yellow oil, drying tubes. One-tenth mole (35.2 grams) of weighed 8 grams. This represents an 88% yield cetyl iodide (B. P. 190° C./6 mm. and n24 1.4810) of benzyl alcohol. was dissolved in 100 cc. of ether and added drop The first of the two preceding examples illus wise to 0.05 mole of lithium aluminum hydride trates a case in which the LiAlH4 was not iso (in 300 cc. of ether). The mixture was heated lated from the ether solution in which it was for six hours under reflux after the last addition prepared. of organic halide and then allowed to stand The second illustrates a reaction starting with overnight before the excess hydride was destroyed the Solid LiAlH4. with water. Next 150 cc. of 10% sulfuric acid The preparation of zinc hydride from Zinc was added, and the aqueous layer extracted with methyl is as follows: 50 two 100 cc. portions of ether, and the ether ex A solution of 0.6 g. of lithium aluminum hy tract dried over three grams of calcium chloride. . dride in 10 g. of diethyl ether was placed in a The ether was removed and a 95% yield of reaction vessel connected with a vacuum System n-hexadecane boiling at 147 C./9 mm., no by a standard ground glass joint. Zinc methyl, 1.4340, and M. P. 17.5° C. Was obtained. 136 cc. (gaseous at standard conditions) was 5 5 The reduction of 2-nitrobutane to 2-amino condensed into the flask after the latter had been butane is as follows: cooled with liquid nitrogen and evacuated. The A one-liter three-necked flask was equipped mixture was allowed to warm slowly to room tem with a reflux condenser, dropping funnel, and perature and formation of a white precipitate Oc a mechanical Stirrer. The funnel and condenser curred. The reaction mixture was filtered and 60 were protected with calcium chloride drying the precipitate was washed several times with tubes. To 0.096 mole of lithium aluminum hy ether. The precipitate was heated at 50° C. in dride (in 130 cc. of ether) 0.0485 mole (5 grams) vacuo to remove the last traces of ether. Zinc of 2-nitrobutane dissolved in 50 cc. of ether was hydride weighing 0.389 g. was obtained for a added. After the last addition, water was added yield of 95%. to decompose the excess hydride, and 250 cc. of The reduction of o-tolunitrile to O-xylylamine 10% sodium hydroxide added. The aqueous is as follows: layer was extracted with four 100 cc. portions A three-necked one-liter flask equipped with a of ether and the ether extract dried over potas reflux condenser, mechanical stirrer, and drop sium hydroxide. Three grams of sec-butyl amine ping funnel was used. The condenser and funnel or 85% of the theoretical amount which boiled were protected with calcium chloride drying at 63 C./750 mm. was obtained. The benzamide tubes. Two-tenths of a mole (23.4 g.) of Ortho derivative was prepared and melted at 75-75.5° C. tolunitrile (B. P. 92-94 C./16 mm.) was dissolved It is not always desirable or essential to isolate in 200 cc. of ether and added dropwise to 0.2 mole the alkali metal aluminum hydride or the like of lithium aluminum hydride (in 300 cc. of ether). 75 prior to a reduction. For example, the prepara 2,576,811 11 tion of diethylsilane from diethyldichlorosilane A list of some of the12 many compounds which may be as follows: are reduced or hydrogenated and the products A suspension of 14 g. (5.8 mole) of sodium hy dride suspended in 200 g. of anhydrous dioxane that are formed are as follows: W was heated to reflux temperature in an appara Starting Material Product tus which had been flushed out with nitrogen. 16 g. (0.10 mole) of diethyldichlorosilane and Heptaldehyde------. N-Hepty Alcohol. Crotonaldehyde. - Croty Alcohol 44 g. (0.33 mole) of aluminum chloride was then Benzaldehyde. -- Beny Alcohol. added and refluxing continued several hours. Benzoyl Chloride. - Benzyl Alcohol. O Panity Chloride- ...texadecano-1, The resulting mixture was then distilled; the Isocaptoy Chloride------Isohexyl Alcohol. Trimethylacetyl Chloride...... Neopenity Alcohol. fraction boiling between 60° and 100° C., at which Symmetrical ortho-Phthaly Phthaly Alcohol. temperature diethylsilane had all been removed, Chloride, was collected. This fraction amounted to about Sorbyl Chloride.------Sorby Alcohol, Benzoic Anhydride. Beny Alcohol. 30 g. The product was refractionated through a Phthalic Anhydride Phthaly Alcohol. Vigreaux column to give 4 g. of a sample boiling 5 Benzoic Acid.----- Beny Alcohol. Cinnamic Acid.---- Eydrocinnany Alcohol. between 50 and 55° C. After repurification of Phenylacetic Acid..... B-Phenylethyl Alcohol. the material in a vacuum system, a 2 g. (0.023 Trimethylacetic Acid Neoperty Alcohol. Steard Acid.------Octadecano-1. W mole) sample having a molecular weight of 88.8 uroic Acid--- Furfury Alcohol. . Saicyclic Acid------O- ESSEE Alcohol. (calculated molecular weight 88.2) was isolated. O-Chlorobenzoic Acid o-Chlorobenzyl Alcohol. This amounted to a yield of 23%. Sorbic Acid.----.--- Sorby Alcohol. The preparation of silane from silicon tetra Pheny Propolic Acid - Phenylpropargy Alcohol. Anthrallic Acid. o-Aninobenzy Alcohol. chloride is as follows: Benzoylformic Acid- Phenylethyleneglycol. A solution of 0.348 g. (9.19 m. moles) of lithium Sebacic Acid.------Decanedio-, 10. Choral Hydrate--- - B.B.B-Trichloroethano. aluminum hydride in 12.5 g. of diethyl ether Ethy Hydrogen Sebacate.-- Decanediol-1, 0. 25 Ethyl Benzoate------Benzyl Alcohol. was placed in a reaction vessel connected with Ethy Palmitate. - Hexadecano-1. a vacuum system by a standard ground glass Methyl Laurate- - Dodecanol Ethy Adipate--- - Hexandiol-1, 6. joint. Somewhat less than the equivalent Methyl Oleate------. Oley Alcohol amount of silicon tetrachloride, 175.2 cc. (7.82 n-Butylmalonic Ester. - 2-Butylpropyleneglycol. m. moles) was condensed into the flask after the Acetone.------Isopropyl Alcohol. Butanone-2----- Sec.-Butyl Alcohol. latter had been cooled with liquid nitrogen and 30 Cycloperatanone. Cyclopenitano. evacuated. The mixture was allowed to warn Cyclohexanone--- Cyclohexanol. slowly to about 0, at which temperature rapid Acetonitrile.--Acetonestylene- Ethylamine.Stylcarbinol. oToluntrile-- o-Xylylamine. evolution of gas and the formation of a white Bentonitrile. Benzylamine. precipitate occurred. Sebaconitrile------1,10-Diaminodecane. The volatile material was fractionated through 35 Nitrobenzene.------Azobenzene. an isopentane bath (-159) and the silane col SEitronesitylene...... 4,4-Dibronoazobenzene.Azomesitylene, Azoxybenzene.------Azobenzene. lected at liquid nitrogen temperature. A 99% p-Nitrosodimethylaniline- Azodimethylanie. yield (175.0 cc.), based on the amount of silicon 2-Nitrobutane.------2-Aminobutane. Ouinone.------Hydroquinone. tetrachloride used, was obtained. The molecular Phenanthraquinone--- Phenanthrahydroquinone, weight of the product was 31.9 (calc. 32.1), the 40 Ally Bronide. Propeae. Methyl Iodide. Methane. vapor tension at -111.9 was 781 mm., or some Cetyl Iodide------Hexadecane. what higher than the 760 mm. value reported Benzy Chloride- Touene. This reaction is effected only by Stock and Somieski. by running at a higher ten The preparation of n-dipropylsilane from perature than the boiling point n-dipropylchlorosiane is as follows: 45 of ether. Tetrahydrofuran was To a solution of iO.0 g. (0.264 mole) of lithium Benzene Sulfonyl Chloride...... Miffused as a solvent. Thiophenol and aluminum hydride in 22.5 g. of diethyl ether, Y Phenyl disulfide. contained in an apparatus, which had previously Phosgene------Methanol. been flushed with nitrogen, 77.8 g. (0.42 mole) of n-dipropylchlorosilane was added with con 50 In the explanation of the invention, reductions stant stirring at a rate to keep the mixture re of unsaturated esters, acids, aldehydes, and other fluxing gently. After completion of the addi carbonyl containing organic compounds, to alco tion, the mixture was maintained at refluxing hols in which the double or triple bonds remain temperature for one hour, and was then filtered. intact, have been described for relatively simple Most of the volatile material was distilled from 55 aliphatic and aromatic compounds. The reduc the filtrate at atmospheric pressure; when the tion of steroid compounds, and substances con temperature of the vapor reached 110, the re taining two or more double bonds, such as in maining portion was removed at 70 and 1 mm. compounds which are related to vitamin A, but pressure. The distiliate was fractionated to ob which contain tain 39.1 g. (80% yield) of n-dipropylsilane, 60 B. P. 110-112 (uncorrected). The following tabulated examples, listed as to starting materials and final products, represent Several types of reactions. Thus, there is the O reduction of aldehydes to alcohols, acid chlorides to alcohols, acid anhydrides to alcohols, acids to alcohols, esters to alcohols, ketones to alco hols, nitriles to primary amines, nitro to azo compounds, nitro to amino compounds, quinones as terminal groups are believed to be within the to hydroquinones, organic halides to hydrocar O invention. Examples of such reduction of more bons, sulfonyl compounds to thioalcohols, as well Complex compounds than those hitherto mens as the reduction. Of carbon dioxide and phos tioned are the reduction of cholestanone to choles gene. Many other types of reactions are possi tanol; of coprastanone to coprasterole; of cholic ble as the new compounds disclosed herein are acid and desoxycholic acid to the corresponding excellent reducing and hydrogenating agents. 5 alcohols; of pregesterOne to 4-dehydropregnaney 2,576,811 13 14 " . diol; and in general, of the reduction of Com bon to carbon link without reacting at said link, pounds having the structure the step, which comprises associating said com pound with a member of the class consisting of H. H. H. H. O aluminum hydride and alkali metal, aluminum hydrides at a reaction temperature sufficiently low that said member does not substantially ther mally decompose during the reduction. O 11. The method of claim 10 wherein said com pound contains more than one unsaturated car O bon to carbon link. 12. The method of claim 10 wherein-the com pound contains conjugated double bonds. to compounds of the structure 13. In the reduction of a hydrocarbon deriva tive compound containing a carbonyl functional 5 group, the step which comprises associating said compound with a member of the class consisting in which R is an organic radical, Saturated or of aluminum hydride and alkali metal aluminum unsaturated, or a saturated or unsaturated cyclic hydrides at a reaction temperature sufficiently radical. low that said member does not substantially ther Having described our invention in considerable 20 mally decompose during the reduction. detail, it is our intention that the invention be 14. In the reduction of a hydrocarbon deriva not limited by any of the details of description tive compound having a nitrogen-containing unless otherwise specified, but rather be con functional group, the step which comprises asso strued broadly within its spirit and Scope as set clating said compound with a member of the class out in the accompanying claims. 25 consisting of aluminum hydride and alkali metal , We claim: aluminum hydrides at a reaction temperature 1. In the reduction of a chemical compound sufficiently low that said member does not sub containing a reducible functional group including stantially thermally decompose during the reduc an atom other than hydrogen and carbon, the tion. step which comprises associating the compound 30 15. In the reduction of a hydrocarbon deriva with a member of the class consisting of alumi tive compound containing an ester group, the num hydride and alkali metal aluminum hydrides step which comprises associating the compound at a reaction temperature sufficiently low that with a member of the class consisting of alumi said member does not substantially thermally de num hydride and alkali metal aluminum hydrides compose during the reduction. 35 at a reaction temperature sufficiently low that 2. The method of claim 1 wherein the reactants Said member does not substantially thermally de are homogeneously mixed together in a substan compose during the reduction. tially nonaqueuos medium. 16. In the reduction of a hydrocarbon deriva 3. The method of claim 1 wherein the reactants tive compound containing a ketone group, the are associated together in a liquid phase. 40 step which comprises associating the compound 4. The method of claim 1 wherein the reactants with a member of the class consisting of alumi are associated together in a solvent in which both num hydride and alkali metal aluminum hydrides reactants are at least partially soluble. at a reaction temperature sufficiently low that 5. The method of claim 1 wherein the reactants said member does not substantially thermally de are associated together in an ether environment. 45 compose during the reduction. 6. The method of claim 5 wherein the ether is 17. In the reduction of a hydrocarbon deriva diethyl ether. tive compound containing an acid group, the step 7. In the reduction of a hydrocarbon deriva which comprises associating said compound with tive compound containing a reducible functional a member of the class consisting of aluminum hy group including an atom other than hydrogen dride and alkali metal aluminum hydrides at a and carbon, the step which comprises associating 50 reaction temperature sufficiently low that said the compound with a member of the class con member does not substantially thermally decom sisting of aluminum hydride and alkali metal pose during the reduction. aluminum hydrides at a reaction temperature 18. In the reduction of a hydrocarbon deriva sufficiently low that said member does not Sub tive compound containing a reducible functional stantially thermally decompose during the reduc 55 group including an atom other than hydrogen tion. and carbon, the step which comprises associating 8. The method of claim 7 wherein the salt of said compound with an aluminum halide and a the desired reduction product is formed and then member of the class consisting of alkali metal hydrolyzed to produce the desired reduction 60 hydrides and a solvent at a reaction temperature product. sufficiently low that said member does not sub 9. In the production of hydrides from an in stantially thermally decompose during the reduc organic compound containing a reducible func tion. tional group including an atom other than hy 19. The method of claim 18 wherein the alumi drogen and carbon, the step which comprises as nun halide is the chloride. sociating the compound with a member of the 20. The method of claim 18 wherein the alumi class consisting of aluminum hydride and alkali num halide is the bromide. metal aluminum hydrides at a reaction tempera 21. The method of claim 18 wherein the solvent ture sufficiently low that said member does not is an ether. substantially thermally decompose during the re 70 22. In the reduction of an inorganic compound duction. containing a functional group including an atom 10. In the reduction of a hydrocarbon deriva other than carbon and hydrogen, the step which tive compound containing a reducible functional comprises associating Said compound with an group including an atom other than hydrogen aluminum halide, an alkali metal hydride and a and carbon and containing an unsaturated car 5 Solvent at a reaction temperature Sufficiently low 9,378,811 5 . - 6 that said member does not substantially ther REFERENCES CITE) mally decompose during the reduction. The following references are of record in the 23. A substantially anhydrous ether solution file of this patent: of a member of the class consisting of alkali metal aluminum hydrides and aluminum hydride, said s UNITED STATEs PATENTs last mentioned aluminum hydride being prepared Number Name Date in said ether by reacting aluminum chloride with 1,521,708 Reacock ----- in m man as a -s. Jan. 8, 1925 a member of the class consisting of alkali metal 2,109,708 Pfister ------Mar. 1, 1938. hydrides and alkali metal aluminum hydrides in 2,263,195 Shikata ------Nov. 18, 1941 the presence of said ether. O 2,425,711 Alexander ------Aug. 19, 1947 24. The solution of claim 23 wherein said ether 2,427,339 Alexander ------Sept. 16, 1947 is diethyl ether. 2,427,791 Ipatief et al. ------Sept. 23, 1947 25. A substantially anhydrous ether solution of aluminum hydride prepared by reacting alumi w FOREIGN PATENTS num chloride with a member of the class Con s Number Country Date sisting of alkali metal hydrides and alkali metal 709,227 Germany ------Aug. 9, 1941 aluminum hydrides in the presence of Said ether. OTHER REFERENCES 26. The solution of claim 25 wherein said ether Tomkinson: Chemical News, May 27, 1921, vol. is diethyl ether. CCK, 27. In the reduction of a hydrocarbon deriva Finholt et al.: Abstracts of Papers, 110th Meet tive compound having a halide-containing func ing Am. Chem. Soc., September 9-13 (1946), page. tional group, the step which comprises associating 27P. said compound with a member of the class Con Brown et al.: Ibid., pages 27P-28P. sisting of aluminum hydride and alkali metal Stecher et al.: Berichte, vol. 75, 2003-12 (1942). aluminum hydrides at a reaction temperature "Reduction of Organic Compounds by Lithium sufficientlystantially thermally low that decomposesaid member during does the not reduc sub Aluminum Hydride,' by Nystrom et al., Journal tion. of the American Chem. Soc., vol. 69, pages 1197 HERMANNI. SCHLESINGER. to 1199 (1947). ALBERT E. ENEOT.