Synthesis of novel bis(β-aminocarbonyl) compounds and some β-aminocarbonyls by catalyst-free multicomponent Mannich reactions

Abstract

A highly diastereoselective catalyst-free multicomponent Mannich reaction between cyclohexanone, aromatic aldehydes and amines in cyclohexane is described. The double Mannich reaction of diamines and two equivalents of aldehydes and cyclohexanone gave the novel bis(β-aminocarbonyl) compounds. Reactions proceeded in good to high yields with an excellent diastereoselectivity. The best selectivity was obtained where there are weak electron donating and electron-withdrawing groups on the aldehyde. The rate formation of Mannich product is decreased when strong electron-withdrawing groups and/or electron-releasing groups are present on aldehyde. In these cases only the corresponding imines are obtained in moderate to high yields. Aromatic diamines are more suitable than aliphatic diamines in this reaction. Usually, aliphatic diamines only produce the corresponding imines albeit in high yields. .