Highly Regio‐ and Stereoselective Double Michael Addition–Cyclization of 2,3‐Allenoates with Organozinc Compounds: Efficient Synthesis of 5‐Benzylidenecyclohex‐2‐enones

Highly substituted α,β-unsaturated cyclohexenones, a key structural motif in many natural products, were prepared in the title reaction (see scheme). High diastereoselectivity was observed with respect to the two stereogenic centers at the 4- and 6-positions. When optically active starting materials were used, the desired products were formed without evident racemization. A rationale for the observed stereoselectivity is proposed.