STEREODEFINED SUBSTITUTED CYCLOPROPYL ZINC REAGENTS FROM GEM-BISMETALLICS

1,1- or n,n-Bismetallic reagents bearing a methoxymethyl ether in the gamma position undergo cyclization at room temperature to give monomet alated, diastereoselectively substituted cyclopropanes, The nature of the substituents is crucial for this diastereoselection, a pi-chelatio n between one metal and a properly located unsaturation, as well as 1, 2-strain, are proposed to explain the steric outcome of these reaction s.