Theoretical Mechanistic Studies on Methyltrioxorhenium-Catalyzed Olefin Cyclopropanation: Stepwise Transfer of a Terminal Methylene Group

Methyltrioxorhenium (MTO)-catalyzed transfer of a methylene group to styrene has been computationally found to preferably follow a stepwise mechanism to give phenylcyclopropane via formation of a pseudo-metallacyclic intermediate and subsequent alkylative cyclization. The present result serves as the first theoretical evidence for d0 transition metal mediated transfer of methylene as a terminal form rather than a metal carbene or carbenoid fashion, accompanied by the cleavage of a H2CO double bond. The mechanism presented here is in contrast to the carbenoid or metal carbene promoted methylene transfer and to the MTO-catalyzed isoelectronic atom (group) transfer in MeRe­(O)2(η2-O–NH) or MeRe­(O)2(η2-O–O). This study not only enriches the chemistry of olefin cyclopropanation and the MTO-catalyzed group (atom) transfer event but also sheds new light on the reaction chemistry of formaldehyde.