Organogermanes can be useful, e.g., in organic synthesis and catalysis. Methods for the formation of C–Ge bonds are, thus, interesting research targets. Access to alkynylgermanes, in particular, could still be improved.

Amit Dahiya and Franziska Schoenebeck, RWTH Aachen University, Germany, have developed a direct C(sp)–H germylation of terminal alkynes with triethyl germanium hydride (Et₃GeH). The team used B(C₆F₅)₃ as a Lewis acid catalyst and 2,6-lutidine as an organic base. They reacted different phenylacetylene derivatives with Et₃GeH in toluene at 100 °C.

The desired products (general structure pictured) were obtained in good yields. The reaction tolerates both electron-withdrawing and electron-donating groups at the aromatic ring. The team proposes a mechanism that involves a hydride transfer from Et₃GeH to B(C₆F₅)₃ to give [HB(C₆F₅)₃]^–, while the 2,6-lutidine stabilizes the Et₃Ge⁺ cation.  The cation can then attack the alkyne group, and 2,6-lutidine facilitates the deprotonation of the resulting intermediate, giving the germylated product. The catalyst is then regenerated and H₂ is released.

• Direct C–H Dehydrogenative Germylation of Terminal Alkynes with Hydrogermanes,
  Amit Dahiya, Franziska Schoenebeck,
  Org. Lett. 2022.
  https://doi.org/10.1021/acs.orglett.2c00840