Trimethylenemethanes from alkylidene carbenes and their [3+2] cycloaddition reaction

Abstract

Studies aimed at the synthesis of angularly fused tricyclopentanoid have been performed. The key step of the sequence utilized intramolecular diyl trapping reaction via cyclopropanation of alkylidene carbene. When a variety of different substrates were subjected to annulation, methylene tricyclo [$5.2.1.0^{1,5}$] decane system was obtained, instead of angular triquinane that initially we expected. It seemed that the stability of transition state did a significant role in determining the regiochemical course of diyl trapping reactions. Although attempts to convert acyclic ketone bearing two double bonds to angularly fused tricyclopentanoid, was not fruitful, we developed a new method for the preparation of bridged tricyclic compound.