A New Synthesis of Bis-Enaminones via Acylation of Ketones

Abstract

A short and efficient synthesis for a series of 1,6-diaryl- 3,4-diarylaminohexa-2,4-diene-1,6-diones was developed. Based on the acylation-prototropism sequence during the reaction of vari- ous aryl methyl ketones with bis-imidoyl chlorides, the products were isolated in good yields. Substituted acetophenones, acetyl- thiophene, 3-acetylpyridine, and acetylferrocene can be integrated into this reaction as ketone component. Similarly, a-tetralone can be transformed with bis-electrophiles into the corresponding bis- enaminones. Treatment of 2-acetylpyridine with N,N¢-bis(4- tolyl)ethanebis(imidoyl) dichloride yielded not only the expected bis-enaminone, but also a new quinolizine derivative which was structurally characterized by single crystal X-ray analysis. Analo- gously, pinacolone and cyclopropyl methyl ketone can readily be converted into bis-enaminones. Monoimidoyl chlorides showed the same reactivity, providing derivatives in high yields.