A method of preparing a cyclopropane ring-bearing compound of the formula (I) in which R1 and R2 are independently selected from C1-C10 alky], optionally substituted, or R1 and R2 together with the bonds linking them to the cyclopropane ring, form a monocyclic or bicyciic ring system, which may comprise at least one hetero-atom, comprising the reaction of a compound of formula (II) in which R1 and R2 have the significances hereinabove defined, with a compound of formula (III) in which X is selected a nucieofuge selected from halides and pseudohalides and Y is an electro flige selected from boranes and borates, in the presence of a metal catalyst complex selected from those that a useful for catalytic cyclopropanation and those useful for catalyzing Heck coupling. The method prov ides a particularly easy and non-hazardous method of cyclopropanation.