Total Synthesis of Pyrrolnitrin. I. Synthesis of 3-Arylpyrrole Derivatives by Knorr's Condensation

摘要: Alkyl 3-aryl-5-methyl-4-pyrrolecarboxylate (IIIa-j) and alkyl 2, 5-dimethyl-3-aryl-4-pyrrolecarboxylate (IIIk-m), two kinds of key intermediates for synthesizing pyrrolnitrin (I), were obtained from 2-aminoacetophenones (IV) acetoacetate by Knorr's pyrrole synthesis. The mechanism the ringclosure above compounds was proposed since 3-substituted benzoylmethylaminocrotonates (VIII) could be isolated as presumably because their difficult cyclization to corresponding pyrroles ; which infrared spectra nitro carbonyl group VIII discussed.