Dimerization Behavior of Substituted Bicyclo[3.1.0]hex‐1‐ene Derivatives

The different reaction profiles of lithium trimethylsilyldiazomethane with various 4-alkenyl ketones are described. It was found that the individual steps along the reaction pathway including a Brook rearrangement, elimination of lithium trimethylsilanolate to form alkylidene carbenes, and their addition to an alkene to form strained bicyclo[3.1.0]hex-1-ene derivatives were significantly affected by the substituents near or on the alkene moiety. Especially, the dimerization of bicyclo[3.1.0]hex-1-enes depends critically on the substituent pattern of the alkene, which controls the reaction to proceed in a concerted or a stepwise manner. On the basis of X-ray diffraction analysis, the dimers, which are of unprecedented structural complexity, were unambiguously elucidated.