Alkylcarbene mediated intramolecular alkene cyclopropanation to construct aza[3.1.0] bicycles

Abstract

The substituents at a carbene carbon atom have a marked influence on the reactivity profiles of carbene intermediates. Compared to acceptor carbenes, alkylcarbenes are far less explored in metal-catalyzed carbene transfer reactions. Herein, we disclose an alkylcarbene-mediated intramolecular alkene cyclopropanation to construct azabicyclo[3.1.0]hexanes. With Rh₂(esp)₂ as catalyst, alkyl diazomethanes in situ generated from 2,4,6-triisopropylbenzenesulfonylhydrazones underwent intramolecular cyclopropanation with alkenes to afford azabicyclo[3.1.0]hexanes in good to high yields under mild reaction conditions. From a synthetic point of view, the intramolecular cyclopropanation of arenesulfonylhydrazones can be viewed as a reductive [2 + 1] cycloaddition between a CC bond and a CO bond, since arenesulfonylhydrazones can be readily prepared from carbonyl compounds.