-Ge/B 1,1-Hydroboration of Alkynylgermanes with 9-BBN.

A 1,1-hydroboration of alkynylgermanes with unique -Ge/B stereochemistry under transition-metal-free conditions is reported. Mechanistic studies suggest that a pathway involving α-boration followed by a stepwise 1,2-Ge/H shift on the intermediate structurally lies between an alkyne-Ge π complex and a typical vinyl cation. The resulting Ge/B bimetallic modules, along with a /Ge/B trimetallic variant, can be conveniently transformed into trisubstituted olefins through iterative divergent cross-coupling. This work demonstrates that incorporating metalloids into classical organic reactions may offer unconventional chemical selectivity and efficient synthetic applications.