Stereoselective Epoxidation of Cyclic Dienes and Trienes by Dioxiranes

Epoxides are essential building blocks in organic chemistry. The epoxidation of unsubstituted cyclic dienes 2-4, and triene 5 using dimethyldioxirane (DDO, 1a) and its trifluoro analog 1b (TFDO) has been investigated. The excellent yields obtained (90-98%) are accompanied by outstandingly high diastereoselectivities (90-98%). Interpretation of results based upon the early idea that polar groups can direct the dioxirane attack by dipole-dipole interaction provides a likely rationale, along with a more generalized mechanistic view.