Synthesis of 1,2,3-trisubstituted cyclopropanes by MIRC reactions of dithianyllithiums with monocarboxylic vinyl epoxide analogues

A variety of cyclopropane derivatives bearing stereochemistry at all three positions on the ring were readily obtained in a high yield of 76-92% and high stereoselectivity (trans:cis > 95:5) when the monocarboxylic vinyl epoxide analogues reacted with dithianyllithiums in the presence of HMPA. This reaction was supposed to be a tandem conjugation addition-opening epoxide ring sequence.