Stereoselective Reductive Rearrangement of α-Hydroxy Epoxides:  A New Method for Synthesis of 1,3-Diols¹

A novel and short synthetic method for the stereoselective synthesis of 1,3-diols has been developed by an unusual reductive rearrangement of a series of α-hydroxy epoxides with aluminum isopropoxide. The reaction process was also investigated with deuterium-labeled aluminum isopropoxide, which revealed a site-specific 1,2-carbon-to-carbon migration and successive stereoselective hydride shift. The main synthetically valuable feature is that up to three contiguous carbon centers, the C-1, C-2, and C-3, were stereoselectively controlled with C-2 being quaternary. This reaction is of particular importance to the synthesis of newly developed powerful asymmetric hydrogenation catalysts containing the chiral ligands of spirocyclic diols.