Enaminones in the mannich reaction. Part 2. Further investigations of internal mannich reactions

Abstract

The reactions of two 3-aminocyclohex-2-enones with formaldehyde have been investigated in detail. The course of each reaction has been followed by u.v. spectroscopy and the conclusions confirmed by chromatography. The gem-dimethyl group of the dimedone derivative directs the reaction to give exclusively the spiran formed by an internal Mannich reaction, but the unsubstituted cyclohexanedione enaminone gives mixtures of spiran and acridinedione derivatives. The results are rationalised on the basis of the different rates of hydrolysis of fhe enaminones.