The cyclopropylmethylsilane terminated prins reaction:: Stereoelectronic controlled formation of (E)-skipped dienes alcohols and a (Z)-skipped diene modification

The reaction of 1-phenyldimethylsilyl-2-vinyl cyclopropane with aldehydes under the influence of dimethylaluminium chloride proceeds smoothly to provide skipped diene alcohols with exclusive E-olefin geometry regardless of the initial cis/trans configuration of the starting cyclopropane. The reaction is under stereoelectronic control where the Prins cation favours an anti-bisected conformation. A syn-bisected conformation can be partially induced by the introduction of a buttressing trimethylsilyl group on the cyclopropane ring, leading to competitive (masked) Z-skipped diene formation.