Trans- and cis-selective Lewis acid catalyzed hydrogermylation of alkynes

reactions: see text] The first examples of Lewis acid catalyzed hydrogermylation of alkynes have been demonstrated. It was found that this method has much higher functional group compatibility compared to the known Lewis acid catalyzed hydrosilylation and hydrostannation reactions. Remarkably, the stereochemical outcome of this hydrogermylation reaction depends on the nature of the alkyne used: proceeding via a trans-addition pathway with simple alkynes and cis-addition with propiolates. Mechanistic studies strongly support the proposed rationale on the origins of cis-selectivity in the hydrogermylation of activated alkynes.