Search

Conjugated phenylazoalkenes add anionic reagents to give 2-substituted anti phenylhydrazones, as demonstrated by 1 H NMR spectroscopy and, in some cases, by comparison with authentic samples.

Conjugated phenylazocycloalkenes sterically hindered towards the antiparallel attach react with PhMgBr via parallel attack, to givesyn-phenylhydrazones. When such a sterical hindrance is absent in the azoalkenes, the reaction occurs via antiparallel attack even when the arylmagnesium bromide bears a particularly hindering aryl group. The conformation of thesyn-phenylhydrazones obtained by the above reactions and those of the corresponding ketones are discussed with the aid of the benzylic proton NMR analysis.

2-Methoxy- and 2-methyl-azobenzene reacted with aromatic Grignard reagents giving 2-methoxy-2′,6′-diaryl- and2-methyl-6-aryl-azobenzene respectively. The mechanism of these arylation reactions was investigated. Evidence for a mechanism of 1,4-addition involving the azo group, followed by elimination of magnesium bromohydride is reported.

A synthesis of the title compounds with the substituents at C-2 and C-6 trans to each other is described. 2-Aryl-cyclohexanones were converted into 1-phenylazo-6-arylcyclohexenes, which by reaction with Grignard reagents led to trans-2,6-diaryl- and trans-2-alkyl-6-aryl-cyclohexanone phenylhydrazones. These compounds by oxidative hydrolysis furnished the corresponding trans-ketones, which were readily epimerised into the more stable cis-isomers.

Conjugated arylazocyclohexenes react with aromatic and aliphatic Grignard reagents to furnish 2-aryl- and 2-alkyl-cyclohexanone arylhydrazones having the syn-configuration with the 2-substituent axially oriented. Their structures have been established by chemical and spectroscopic methods. These compounds, as well as the anti-isomers, undergo ready autoxidation to give arylazo-hydroperoxides. The structure of 1-hydroperoxy-1-(o-methoxyphenylazo)-2-phenylcyclohexane has been determined by X-ray analysis.

4-Methyl- and 4-t-butyl-1-arylazocyclohexenes react with aliphatic and aromatic Grignard reagents, to furnish, after oxidative hydrolysis of the intermediate aryihydrazones, 2-alkyl-4-methyl-, 2-aryl-4-methyl-, 2-alkyl-4-tbutyl-, and 2-aryl-4-t-butyl-cyclohexanones, with a trans-configuration. From the reactions with o-tolyl- and α-naphthyl-magnesium bromide only the cis-isomers were obtained. The structures of the products were, determined by spectroscopic methods and by epimerization of the trans-cyclohexanones into the more stable cis-isomers.