Stereoselective Epoxidation of cis-3,4-Disubstituted-(CH2X)-Cyclobutenes with Dimethyldioxirane and Peroxy Acids. Experimental and Computational Evidence for a Syn-Orienting Electrostatic Effect

The epoxidation reactions of a series of cis-3,4-disubstituted-(CH2X)-cyclobutenes with dimethyldioxirane (DMD) and mClPBA have been investigated with both reagents. A remarkable syn diastereoselectivity in the formation of the epoxide has been obsd. for substrates bearing electron withdrawing substituents.