A General Method for the Preparation of 7-Substituted Cyclohexenals and Cycloheptenals

A general procedure for the preparation of γ-substituted or β'-unsaturated cycloalkenals is described. Starting from 2-cycloalkenones substituents may be introduced as nucleophiles by 1,4-addition followed by trapping of the regiospecifically generated enolate (86-92%). Peracid oxidation of the enol silane derivative produces an a-hydroxy ketone which, after protection (70-93%), is homologated to an enol ether by a Horner-Wittig reaction. Mild hydrolysis of the labile vinylogous acetal produces the aldehydes in good yields (62-75%), Advantages of this method in comparison to known procedures are discussed as are other unsuccessful approaches to this substitution pattern.