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

Abstract

Preparation of alkylidenecyclopropane and synthesis of triqunanes have been studied. Alkylidenecyclopropanes are useful intermediates in organic synthesis. We have developed a practical method for the preparation of alkylidene- cyclopropane. This cyclopropanation also provided valuable information in gaining insight into the electronic as well as steric factors that affect the addition of carbenes to alkenes. Electron rich and less substituted alkenes showed good yield. Electron poor and more substituted alkenes showed moderate yield. Synthesis of tricyclopentanoid derivatives through diyl trapping reaction was progressed. This diyl was generated from intramolecular cyclization of alkylidene carbene to olefin. Cyclization was accomplished through sequential generation of alkylidene carbene, cyclopropanation, diyl generation and diyl trapping reaction. The advantage of our process was construction of all cyclic structure at once. For the reason of pseudo-chair transition state conformation and secondary orbital interaction, this cyclization gave desired cis, anti-fused-ring product. Using our method, various natural products of possession of tricyclic structure could be synthesized.