Unusual Michael reaction of acyclic 1,3-dicarbonyl compounds with nitre-olefins. A novel pyrrole synthesis

Abstract

Acetoacetic esters and pentane-2,4-dione undergo unusual Michael reactions with β-nitrostyrene in methanolsodium methoxide to formthe (2R,3R,2′S,3′S)-bis-(4-acy1-2,3-dihydro-5-methyl-3-phenyl-2)-furylhydroxylamines (5) in high yields. The normal adducts (6) are intermediates in these reactions. Acetylation of compounds (5) gives the hydroxylamine O-acetates (7).

Compounds (5) react with ammonia and amines in methanol to give the 3-acylpyrroles (9) which can be isolated in high yields. These pyrroles can be easily obtained in high yields in a one-pot process by reaction of the 1,3dicarbonyl compound with β-nitrostyrene and subsequent treatment of the reaction mixture with ammonia or amines.

A mechanism for the formation of the unusual Michael products (5) is discussed.