A Method for the Late-Stage Formation of Ketones, Acyloins, and Aldols from Alkenylstannanes: Application to the Total Synthesis of Paecilonic Acid A.

Treatment of alkenylstannanes with Cu(OAc)2 /Et3 N affords the corresponding enol esters or ketones under conditions that proved compatible with many common functionalities; these include groups that would neither survive under the standard Tamao-Fleming conditions for the oxidation of Csp2 -SiR3 bonds nor under the conditions commonly used to oxidize C-B bonds. Chiral centers adjacent to the unveiled carbonyls are not racemized and competing protodestannation is marginal, even if the substrate carries unprotected -OH groups as internal proton sources. Therefore, the procedure is well suited for the preparation of acyloin and aldol derivatives. These enabling virtues are illustrated by a concise approach to the bicyclic lipid paecilonic acid A.