Copper(I)-Catalyzed Asymmetric Hydrogermylation of 3,3-Disubstituted Cyclopropenes.

Catalytic asymmetric approaches to enantioenriched organogermanium compounds remain severely underdeveloped. Herein, we report a CuOAc-catalyzed enantioselective hydrogermylation of 3,3-disubstituted cyclopropenes, which furnishes structurally diverse chiral organogermanes in high to excellent diastereo- and enantioselectivities. Control experiments demonstrate that copper carboxylate is uniquely effective for this transformation. In contrast, catalytic systems composed of Cu(CH3CN)4PF6 and an exogenous base (e.g., triethylamine, Barton's base) afford negligible reactivity. Mechanistic studies elucidate that the CuOAc-bisphosphine catalysts enable the critical deprotonation of H3GeAr/H2GeAr2 through a possible synergistic six-membered cyclic transition state. Finally, versatile post-functionalization of the obtained products further expands the structural library of enantioenriched organogermanium compounds.