Divergent Pathways of Reaction Between Cyclohexanone Enamines and α,β-Unsaturated Acid Chlorides

Abstract

The reaction of cyclohexanone enamines with α,β-unsaturated acid chlorides and 2- and 3-chloropropanoyl chlorides under various conditions has been investigated. a,ae-Annulation of enamines Ia-Ie occurs on treatment with chlorides IIa-IId or 3-chloropropanoyl chloride to give bicyclo[3.3.1]nonane-2,9-dione derivatives III. The formation of isomeric bicyclononanediones IIIe and IIIh and chromanones VIIIa and VIIIb in the reaction of enamines derived from substituted cyclohexanones suggests that the cyclization might proceed also by another pathway than via [3,3] sigmatropic rearrangement. Based on the reaction course and product distribution in these reactions, a parallel reaction pathway involving a C-acylation-Michael addition has been suggested.