Pyrrolnitrin analogues. V. Knorr's pyrrole condensation between N-(4-nitrophenacyl)-3,5-dimethylaniline and ethyl acetoacetate.

The reaction between N-(4-nitrophenacyl)-3,5-dimethylaniline and ethyl acetoacetate in boiling ethanol afforded 3-carbethoxy-5-(1-carbethoxyacetonyl)-4,5-dihydro-1-(3,5-dimethylphenyl)-4-hydroxy-2-methyl-4-(4-nitrophenyl)pyrrole and in low yield 3-carbethoxy-1-(3,5-dimethylphenyl)-2-methyl-4-(4-nitrophenyl)pyrrole. Chemical transformation of the former compound into 5-acetonyl-1-(3,5-dimethylphenyl)-2-methyl-4-(4-nitrophenyl)pyrrole is described. The structure of 3-carbethoxy-5-(1-carbethoxyacetonyl)-4,5-dihydro-1-(3,5-dimethylphenyl)-4-hydroxy-2-methyl-4-(4-nitrophenyl)pyrrole has been established by the aid of N.M.R. spectral data. The above reaction, when carried out in boiling ethanol in the presence of a catalytic amount of 3,5-dimethylaniline hydrobromide, led to the formation of 3-carbethoxy-1-(3,5-dimethylphenyl)-2-methyl-4-(4-nitrophenyl)pyrrole and 4,6-dimethyl-2-(4-nitrophenyl)indole, the former formed in a very good yield. Some pyrrolnitrin analogues have been prepared starting from 3-carbethoxy-1-(3,5-dimethylphenyl)-2-methyl-4-(4-nitrophenyl)pyrrole.