Cis and Trans 1-CYCLOHEXYL-2-PHENYL-3-p-TOLUYL ETHYLENE IMINES

Herman Hoeksema’s 1948 Ph.D. dissertation, “Ethylene imine ketones”, found that the low melting isomer was least stable and seemed to convert to the high melter in solution. This was indicated during lengthy fractional recrystallization and time light-absorption spectrum studies. The interconversion was apparently light catalyzed. He also reacted these isomers with phenylhydrazine to give a pyrazole in the case of the low-melting isomer. By heating the aminopyrazoline with 20% sulfuric acid, benzylamine was split out to form the pyrazole. A possible mechanism was offered for this reaction. It was of interest to see if Hoeksema’s case was merely an isolated case or whether it was possible to form isomers in similar cases by varying the amine to cyclohexylamine which was known to react to give ethylene imine ketones. After those isomers were obtained it was of interest to see if there would be a difference in the reactions of these with the Grignard reagent since previous studies with the Grignard had been carried out with what appears to have been high melting isomers only. Also, it seemed necessary to study the reaction of such compounds with phenylhydrazine, confirming and extending the investigations of Hoeksema. Cyclohexylamine has been found to condense with benzal-p-methylacetophenome dibromide or with α- bromobenzal-p-methylacetophenone to form cis and trans l-cyclohexyl-2-phenyl-3-p-toluyl ethylene imines. The above isomers have the following properties. Their absorption spectra are very similar to the cis and trans isomers prepared by Hoeksema. The cis form is less stable to light than the trans isomer, but no evidence has been found that a cis-trans interconversion occurs with these compounds. In the case of the trans ethylene imine, the reaction with the phenyl Grignard reagent leads to only one racemic enamine carbinol. However, in the case of the cis ethylene imine, the reaction with the phenyl Grignard reagent has apparently led to the two possible racemic enamine carinols to be expected from this ethylene imine ketone. The trans isomer reacts with phenyhydrazine to form 1, 5-diphenyl-3-p-tolyl pyrazole. When acetic acid is used as the solvent a second yellow by-product is obtained which is believed to be an acetylated phenylhydrazone of the ketone. In the case of the cis isomer the intermediate 1, 5-diphenyl-3-p-tolyl-4-cyclohexylaminopyrazoline can be isolated. Upon heating with glacial acetic acid the pyrazoline is converted to the same pyrazole produced by the trans isomer. With acetic anhydride the amino pyrazoline gives an acetylated aminopyrazoline. Advisor: Norman H. Cromwel