Investigation of a dialkylation approach for enantioselective construction of vicinal quaternary stereocenters.

A detailed study of the dialkylation of dianions derived from dihydroisoindigo 1 with enantiopure ditriflate 2 is reported. The LHMDS-mediated process has been optimized to give C(2)-symmetric product 3 with high selectivity (C(2) selectivity 3:5 = 100:1; C(2):C(1) selectivity = 8:1). Stereoselection in the C(2) manifold is determined in both the bimolecular and intramolecular alkylation steps.