Reactions of 1,2-diaminobenzene with 1,3-diketones

Abstract

The reaction of 3-substituted derivatives of pentane-2,4-dione (acetylacetone) with 1,2-diaminobenzene has been studied. The 3-methyl, 3-prop-2-ynyl, and 3-benzyl derivatives gave 1,5-benzodiazepines, but no cyclization occurs with the 3-chloro and 3-(2,4-dinitrophenyl) derivatives. No 3,3-disubstituted benzodiazepines were obtained. 3,3-Dichloropentane-2,4-dione affords non-cyclized chloro-products. The mechanism of formation of 2,3-diaminophenazine derivatives, significant when the reactions are prolonged, is rationalized.