In situ generation of zinc carbenoids from diazo compounds and zinc salts: asymmetric synthesis of 1,2,3-substituted cyclopropanes.

The first enantioselective cyclopropanation of alkenes using zinc carbenoids generated in situ from diazo compounds and zinc salts is reported. This new method allows the highly enantio- and diastereoselective synthesis of 1,2,3-substituted cyclopropanes via aryl-substituted carbenoids. The first Simmons-Smith reaction using a catalytic amount of zinc to generate enantioenriched cyclopropane is also reported.