Highly Diastereoselective Synthesis of <i>vicinal</i> Quaternary and Tertiary Stereocenters Using the Iodo-aldol Cyclization

The intramolecular iodo-aldol cyclization of α-substituted enoate aldehydes and ketones is described. Using prochiral starting materials, the reaction produces hetero- and carbocycles containing quaternary centers adjacent to secondary or tertiary centers. The reactions occur in good yields and are highly selective for the trans-products, having the hydroxyl and iodomethyl groups on opposite faces of the ring system.