Construction of Ge-Stereogenic Center by Desymmetric Carbene Insertion of Dihydrogermanes

Abstract

We developed a method for the enantioselective synthesis of germanium-stereogenic compounds by the desymmetric carbene insertion of dihydrogermanes. A chiral rhodium phosphate catalyst decomposes diaryldiazo-methanes to generate rhodium carbenes that insert enantioselectively into one of the two Ge−H bonds of dihydrogermanes to form germanium-stereogenic compounds under mild reaction conditions. By this method, a variety of chiral germanes with germanium-stereogenic centers were synthesized in high yields and excellent enantioselectivities. Kinetic studies of the reaction showed that the diazo decomposition process was the rate-determining step. The remaining Ge− H bond of the chiral germane products provides a possibility for preparing chiral tetra-substituted germanium-stereogenic compounds.

D4-Symmetric Dirhodium Tetrakis(binaphthylphosphate) Catalysts for Enantioselective Functionalization of Unactivated C–H Bonds

“…However, the corresponding tetraphenyl catalyst S - 6a , which is closely related to the current catalyst design, results in much lower levels of enantioselectivity (11% ee), although the p - n -butylphenyl derivative S - 6b gave up to 63% ee . It should be noted that another C 2 -symmetric phosphate ligand class that have been successfully applied to generate D 4 -symmetric dirhodium catalysts are the spiro ligands developed by Zhou, but we decided to focus on binaphthylphosphates because of their ease of synthesis.…”