STEREOCONTROLLED CONSTRUCTION OF COMPLEX CYCLIC-KETONES VIA OXY-COPE REARRANGEMENT

Convergency is a highly serviceable aspect of organic synthesis, particularly when its application is accompanied by high levels of chirality transfer and regiocontrol. A reaction that is notably well suited to these objectives is the oxy‐Cope rearrangement. In addition, the benefits that can accrue from suitable condensation of β γ‐unsaturated ketones with a vinyl organometallic and subsequent [3,3] sigmatropic shift are substantive enhancement in structural complexity and the ability to generate a myriad of polycyclic frameworks. Another profitable feature is the complementary regeneration of the carbonyl group in a new structural context. In view of the pivotal role played by the carbonyl functionality in synthetic transformations, reacquisition of such a reaction site translates into heightened chemical versatility. The trajectories followed by vinyl organometallics as they engage in 1,2 addition to ketones are gradually being understood. Proper diastereoselective control of this bond‐making process, when coupled with full awareness of the chair or boat topography adopted during the ensuing oxy‐Cope electronic reorganization, provides for exciting new strategy‐level dimensions not often available in other contexts. The use of this two‐step sequence as a prelude to a third chemical event clearly serves to expand the possibilities for molecular construction still more. While a considerable amount of the work to date has focused on the preparation of rather elaborate carbocyclic molecules, principally with a view to gaining access to complex natural products, the possibilities for heterocyclic synthesis are currently being accorded increased attention. Copyright © 1990 by VCH Verlagsgesellschaft mbH, Germany