THE USE OF TRIAZENES AS VINYL CATION PRECURSORS By FREDERICK WILLIAM MILLER A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA December, 1966 ACKNOWLEDGMENTS The author would like to express his gratitude to the faculty members and staff of the Chemistry Department and to his fellow graduate students for their friendship. He is especially indebted to Dr. W. M. Jones, who directed his research and gave invaluable suggestions during the progress of this work and the preparation of this dissertation. He also wishes to thank the other members of his committee for their helpful suggestions in the preparation of this dissertation and Mrs. Carol Miller for her excellent typing. 11 - - - TABLE OF CONTENTS Page ACKNOWLEDGMENTS ii LIST OF TABLES vii Chapter I. INTRODUCTION 1 II. THE SYNTHESIS AND DECOMPOSITION OF l-(TRIPHENYLETHENYL) 3-PHENYL-l-TRIAZENE 6 III. THE SYNTHESIS AND DECOMPOSITION OF l-(2,2-DI-P-TOLYL- P HENYL ETHENYL ) - 3 -P HENYL - 1 -TR I AZ EN E 15 2 IV. THE SYNTHESIS AND DECOMPOSITION OF 1 - ( 2 , -DIPHENYL -METHYL ETHENYL) -3-PHENYL-l-TRIAZENE 21 V. THE SYNTHESIS AND DECOMPOSITION OF 1 -(2, 2-DIPHENYLETHENYL) 3-PHENYL-l-TRIAZENE 26 VI. A DISCUSSION OF THE ADDITION-ELIMINATION MECHANISM IN THE ACID DECOMPOSITION OF THE VINYL TRIAZENES 37 VII. SUMMARY 47 VIII. EXPERIMENTAL 49 General 49 Preparation of bromo-2,2-diphenylethylene 50 Preparation of bromo-triphenylethylene 50 Preparation of bromo-phenyl-(2,2-di-p-tolyl)- ethyler.e. 50 Preparation of bromo-methyl-(2,2-dipheaylethylene) 51 Preparation of phenyl azide 51 Preparation of l-(2,2-diphenylethenyl )-3-phenyl-l- triazene (X) 51 iii Ozonolysis of l-(2, 2-diphenylethenyl )-3-phenyl- 1 -triazene 53 Preparation of l-( triphenylethenyl )-3-phenyl- 1 -triazene (i) 54 Ozonolysis of l-(triphenylethenyl )-3-phenyl- 1 -triazene 54 Preparation of l-(2,2-di-p-tolyl-phenylethenyl )- 3-phenyl-l-triazene ( VI II) 54 Ozonolysis of l-(2,2-di-p-tolyl-phenylethenyl)- 3-phenyl-l-triazene 55 Preparation of l-(2,2-diphenyl-methylethenyl)- 3-phenyl-l-triazene (IX) 55 Ozonolysis of l-(2,2-diphenyl-methylethenyl )- 3-phenyl-l-triazene 55 Preparation of diphenylacetylene 56 Preparation of , 1 1 ,4,4-tetraphenyl-l ,3-butadiene . .... 56 Preparation of sodium p-toluenesulf inate and p- toluenesulfinic acid 56 Preparation of di-p-tolyl ketone 57 Preparation of p-methylbenzophenone 57 Preparation of desoxybenzoin 57 Preparation of phenyl benzhydryl ketone 57 Preparation of cis and trans -1 , 2-diphenvl- vinyl acetate (19) 58 Preparation of 2,2-diphenylvinyl acetate 60 Preparation of triphenylvinyl acetate 60 Preparation of triphenylethyleneglycol diacetate 60 Preparation of hydrobenzoin diacetate 61 Typical decomposition of l-(2,2-diphenylethenyl)- 3-phenyl-l-triazene with acetic acid 61 IV - Attempted interception of vinyl diazoniun ion with (3-naphthol 62 Attempted interception of vinyl diazo intermediate with dimethyl fumarate 63 Preparation of acetanilide under reaction conditions. 64 Typical acetic acid stability of the products resulting from the decomposition of l-(2,2- diphenylethenyl )-3-phenyl-l-triazene 64 Decomposition of l-(triphenylethenyl )-3-phenyl- 1-triazene with acetic acid 68 Decomposition of l-( triphenylethenyl )-3 -phenyl- 1-triazene with sulfuric acid 69 Decomposition of l-( triphenylethenyl )-3-phenyl- 1-triazene with p-toluenesulfonic acid 70 Decomposition of l-( triphenylethenyl) -3-phenyl- 1-triazene with phenol. -An attempt to intercept a vinyl diazonium ion with phenol. 71 Decomposition of l-(triphenylethenyl )-3-phenyl- 1-triazene with p-toluenesulfinic acid 72 Preparation of triphenylvinyl acetate, itriazene method 72 Decomposition of l-(2,2-di-p-tolyl-phenylethenyl) 3-phenyl-l-triazene with acetic acid 73 Ozonolysis of di-p-tolylphenylvinyl acetate 74 Decomposition of l-(2,2-di-p-tolyl-phenylethenyl )- 3-phenyl-l-triazene with p-toluenesulfinic acid 74 Ozonolysis of di-p-tolyl-phenylvinyl-p-tolyl sulfone. 75 Typical ozone stability test of the products resulting from the decomposition of l-(2,2-di-p- tolyl-phenylethenyl) -3-phenyl-l-triazene with acid. ... 75 Decomposition of l-(2,2-diphenylethenyl)-3-phenyl- 1-triazene with deuterated acetic acid-acetic anhydride. .76 Decomposition of l-(2,2-diphenylethenyl)-3-phenyl- 1-triazene with acetic acid-acetic anhydride 77 v Decomposition of l-(2,2-diphenyl-methylethenyl)-3- phenyl-l-triazene with acetic acid 78 Ozonolysis of diphenylmethyl vinyl acetate from the decomposition of l-(2,2-diphenyl-methylethenyl)- 3-phenyl-l-triazene with acetic acid. 78 Hydrolysis of diphenylmethylvinyl acetate from the decomposition of l-(2,2-diphenyl-methylethenyl )-3- phenyl-l-triazene 79 Preparation of 9-bromomethylenefluorene 80 Preparation of bromo-2,2-dimethyl-phenylethylene 80 Attempted preparation of 9-bromomethylene-10-xanthene. .81 Attempted preparation of bromomethylene-cyclopentane . .81 Attempted preparation of l-(2-pentamethylene- ethenyl)-3-phenyl-l-triazene 81 Attempted preparation of l-(2,2-dimethyl~phenyl- ethenyl )-3-phenyl-l-triazene 82 Attempted preparation of l-(phenylethynyl)-3- phenyl-l-triazene 83 BIBLIOGRAPHY 85 BIOGRAPHICAL SKETCH 89 vi LIST OF TABLES Table Page I DECOMPOSITION OF l-(TRIPHENYLETHENYL)-3-PHENYL-l-TRIAZENE. .13 II DECOMPOSITION OF l-(2,2-DIPHENYLETHENYL) -3-PK£NYL-l- TRIAZENE WITH VARIED ACETATE ION CONCENTRATION 31 III ATTEMPTED INTERCEPTION OF THE PRECURSORS OF THE 1,2- DIPHENYLVINYL CATION vii . THE USE OF TRIAZENES AS VINYL CATION PRECURSORS I. INTRODUCTION Within the past ten years several groups of investigators have studied reactions in which vinyl cations have been postulated as inter mediates. The methods of access to vinyl cation intermediates can be conveniently divided into two general categories. In the first method the vinyl cation is produced by the hydration of a triple bond. For example, Peterson (l) has postulated a vinyl cation in the reaction of 1 -hexyne with trif luoroacetic acid, and in trif luoroacetolysis of 6-heptyn-2-yl p-toluenesulfonate (2) (Scheme A) © © G O2CCF3 0 CCF ^ 2 3 NaOnCCF., •0 CCF 2 ; ho ccf (Scheme A) •OTs 2 3 Ws Noyce (3) has gathered product and kinetic evidence for the existence of a vinyl cation in the acid hydration of phenyl propiolic acids and phenyl acetylenes (Scheme B) © © ArC=CC02H+ H O > ArC = CHCO^H © 3 ArC=CHC0 H + H 0 -> 2 2 ArC =CHCOzH ©oh -H® 2 ArC = CHC02H ArC = CHCOoFl ©OH 2 6h ArC =CHC0 - oH ArC CHJSCL-iH2 OH 6 r (Scheme B) 1 . ' . 2 Richey (4) has presented spectral evidence far the existence of an unusual vinyl cation intermediate in a study of alkynyl cations (Scheme C) ?H © Ar-C —C=CCH Ar-C CSCCHo Ar Ar © © Ar-C — C = CCH < > Ar-^ =C=CCH J Ar At Ar-C — C —?CH„ H 90 Ar-C = CH-C-CHg (Scheme C) In the second general method the vinyl cation is produced by the loss of a vinylic halide ion or by the loss of elemental nitrogen from a vinyl diazonium ion. For example, Grob (5,6) has gathered evidence for the existence of a vinyl cation intermediate In the solvolytic decarboxylation of °c, r3 -unsaturated p-halo acids and the solvolysis of bromo styrenes (Scheme D) H H / -co2 c =c R-C: > RC=CH COr © CO, © ‘ © h o -co 2 2 > > R-£-CH 0 © /H HO :c=c r-c^c R CH R s \ n , "6' 2 R R ^ “ R-C=C-R (Scheme D) One of the better examples of this second route to the vinyl cation intermediate can be found in the recent ivoric of Curtin (7) on the nitrosation of primary vinyl amines. Curtin postulated that the nitrosation produced a vinyl diazonium ion which decomposed to a 3 vinyl cation. The vinyl cation intermediate accounted for the products and yields under various reaction conditions. Curtin, however, found (8) that the products that were produced on nitrosation of 3-amino-2- phenylindenone were better explained by invoking an addition-elimination of acetic acid on the vinyl diazonium ion produced in the nitrosation (Scheme E) .* © Ar NH Ar / 9 /N2 -N Ar^ © C=C 2 x n > xC=C-Ar a/ h N0C1 Ar H H (Scheme E) As a possible reason for the mechanistic change, Curtin suggested that the 1 ,2-diphenylvinyl cation could adopt a linear configuration but the analogous cation from the decomposition of the 3-diazonium-2- phenyl indenone cation could not assume this linear configuration, and * Product stereochemistry is not implied. 4 forced the decomposition to proceed through the observed addition- elimination mechanism. The concept that a linear vinyl cation is more stable than a non-linear vinyl cation because of charge delocal- ization is 1 generally accepted ( —8 and references therein) and deserves little additional comment at this point. The change in mechanism which was inferred by Curtin (8) has serious implications . A study of any system in which a vinyl cation is postulated as a possible intermediate must also include evidence designed specifically to rule out a possible addition-elimination route to products. In light of the recent success of Curtin, it was decided that a study of vinyl cations using vinyl diazonium ion precursors might prove even more fruitful if a wider variety of vinyl diazonium ions were available and if the scope of the mechanistic study could be broadened by making solvent changes. Several problems became evident. First, aryl vinyl amines are not a well known class of compounds and aliphatic vinyl amines are not synthetically accessible. Second, the fact that the diazonium ion is generated and destroyed in situ automatically limits the choice of solvents and conditions under which the vinyl cation can be studied. There is some evidence that the decomposition of phenyl diazonium ions in polar media can lead to the formation of phenyl cations (9,10), which are formally analogous to vinyl cations.