REACTIONS OF FISCHER CARBENE COMPLEXES WITH ELECTRON-DEFICIENT OLEFINS - SCOPE AND LIMITATIONS OF THIS ROUTE TO DONOR ACCEPTOR-SUBSTITUTED CYCLOPROPANES

The Fischer carbene complex [(CO)5Cr═C(OMe)Ph] (1) is able to transfer its carbene ligand to a variety of electron-deficient olefins and provides donor-acceptor-substituted cyclopropanes in good yields. Apt activating groups with respect to the alkene are ester, amide, nitrile, sulfone, and dialkyl phosphonate functions. Methyl vinyl ketone (19) affords products in low yield that may arise from an intermediate cyclopropane derivative. Phenyl vinyl sulfoxide (24) mainly acts as an oxidizing agent, transforming 1 into methyl benzoate. For olefin 24 and α-(N-methylanilino)acrylonitrile we found products that should be formed on an olefin metathesis pathway. The methyl-substituted carbene complex 48 also affords the expected donor‒acceptor-substituted cyclopropanes; however, acyclic isomers are formed in higher amounts. The molybdenum and tungsten complexes 55 and 56, respectively, also furnish cyclopropane derivatives, but the yields are lower than with the chromium compound 1. Disubstituted olefins and complex 1 still give the cyclopropanes in moderate yields, while all trisubstituted and most of the difunctionalized alkenes do not react with this Fischer carbene complex. The cyclopropanes synthesized can be deprotonated and alkylated or transformed into ring-opened products. These model reactions demonstrate the synthetic potentials of donor‒acceptor-substituted cyclopropanes prepared via Fischer carbene complexes. © 1990, American Chemical Society. All rights reserved.