Cyclooctanoid Ring Systems from Mixed Acetals via Heteroatom-Assisted [1,2]-Shift of Oxonium Ylides

Cyclic mixed acetals with pendant diazoketone side chains undergo efficient rearrangement to ether-bridged cyclooctanoid systems upon treatment with Cu(hfacac)2. This result demonstrates that heterosubstituted carbons are suitable migrating groups for the Stevens [1,2]-shift of oxonium ylides. In the case of a mixed thioacetal, the resulting sulfide served as a trigger for cleavage of the bridging ether through one of two complementary strategies, furnishing a bicyclo[6.3.0]octene product with an angular hydroxyl group.