Diastereoselective Synthesis of Allenes through Phosphine-Catalyzed Cascade Isomerization/Annulation.

Phosphine-catalyzed cascade isomerization/annulation has been developed to realize a diastereoselective synthesis of allenes installed on the hexahydropentalene skeleton, which contains five chiral centers (and one axial chirality). This reaction tolerated a broad range of allenoates and enynes. The allene products were transformed to various halogen-substituted fused-ring compounds.