Foiled carbenes

Suitably constructed bridged carbenes exhibit a tendency for structural rearrange ment and undergo the so-called foiled methylene reaction 141 142) with formation of bicyclo[3.3.0]octane derivatives. The behavior of P6143) and 97144) exemplifies such conversions. Carbonium ion analogies to such reactions are known. ... 

Anchimeric stabilization of foiled carbenes by a cyclopropane ring has been explored for compounds such as (2) This stabilization arises from the interaction between the vacant orbital of the carbene and the occupied Walsh orbital of the cyclopropane which results in the bending of the bridge towards the cyclopropane ring, and in the stereochemical outcome of trapping experiments. 

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