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The first examples of the cyclopropanation of 1,3-dienes with transition metal carbene complexes is reported for the heteroatom-stablized pentacarbonyl complexes of the group 6 metals. The reaction of the chromium phenylmethoxymethylene complex 36 with Danishefsky's diene gives varying amounts of cyclopro- panes and metathesis products whose distribution is carbon monoxide dependent. The reactions of the cyclo- hexenylmethoxymethylene complexes is metal dependent. The chromium complex 12a gives a chemoselective reaction with Danishefsky's diene resulting in the formation of cyclopropanes, whereas, the same reaction of the tungsten complex 12b chemoselectively gives Diels-Alder cycloadducts. Some cyclopropanation reactions of the phenylmethoxymethylene complex 36 with silyl enol ethers and enamines are also presented.

Cyclopropanations and cycloadditions of transition metal carbene complexes