Reaction of olefins with CHCl2F and BuLi gave stereospecifically the cis and trans isomers of 2-R1, 2-R3, 3-R2, 3-R4 = tetrasubstituted 1-chloro-1-fluorocyclopropanes (I) (R1 = H, Me; R2 = H, Me, Pr; R3 = Me, Pr, Ph, amyl, OEt, OBu-iso; R4 = H, Me, Pr), which on redn. with Na/liq. NH3 gave 40-84% 2-R1, 2-R3, 3-R2, 3-R4-tetrasubstituted fluorocyclopropanes (II) with retention of the configuration. With excess Na, I were reduced to halogen-free alkyl- and alkoxy-substituted cyclopropanes. [on SciFinder (R)]