Highly Selective Synthesis of Alkylidenecyclopropanes

Significance

The preparation of enantioenriched alkylidenecyclopropanes with quaternary stereocenters is still challenging. The authors recently reported the copper-catalyzed Grignard addition to cyclopropenyl alcohols to yield alkylidenecyclopropanes with high stereoselectivity (Angew. Chem. Int. Ed. 2006, 45, 3963). Herein, they report a very mild method to generate similar structures with high control of chirality and E/Z selectivity by [3,3]-sigmatropic rearrangements.