Catalytic Cyclopropanation of Fluorine-Containing Alkenes and Dienes with Diazomethane and Methyl Diazoacetate

The reactivities of various double bonds in fluorine-containing unsaturated compounds toward cyclopropanation with diazomethane and methyl diazoacetate with catalysis by copper, rhodium and palladium compounds were studied. In general, the presence of fluorine atoms attached to the double bond or arranged at neighbouring positions exerted a suppressive effect on the cyclopropanation of this bond. As would be expected, diazomethane in the presence of palladium compounds primarily cyclopropanated less highly substituted double bonds. In the case of 2-fluoro-3-methylbutadiene, the reaction took place at both of the double bonds. When methyl diazoacetate was used, [Rh2(OAc)4] was an efficient catalyst, yielding cyclopropanation products on monofluoro-substituted double bonds in alkenes and cycloalkenes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)