Hydrogenolysis of Unstrained Carbon−Carbon σ Bonds: Stereoselective Entry into Benzylic Tertiary Centers

The modification of sp(3)-hybridized carbon centers through Pd-catalyzed reductive cleavage of unstrained carbon-carbon sigma bonds is described. From the hydrogenolysis of benzyl Meldrum's acids bearing an all-carbon benzylic quaternary center, Meldrum's acid and aromatics substituted with a tertiary benzylic stereocenter were obtained in good to excellent yields. Mechanistic studies showed that the reductive cleavage of enantioenriched benzylic quaternary centers proceeded with inversion of configuration, supporting a "loose" S(N)2 pathway.