An On-Demand, Selective Dehydrogenative Borylation or Hydroboration of Terminal Alkynes Using Zn2+-based Catalyst

An air-stable dicationic Zn2+ complex (1) in a tripod-type ligand with non-bound phosphorus base and three pyridinyl arms (TPPh) was synthesized. Remarkably, while 2 mol% of 1 at room temperature selectively catalyzed dehydrogenative borylation of terminal alkynes with HBPin, a lower loading of 1 (0.5 mol%) at 90 degrees C selectively promoted hydroboration reaction of the same alkynes skipping the dehydrogenative borylation step. The mode of action of 1 was proposed based on experimental observations as well as the mechanism of dehydrogenative borylation was studied by DFT computations.

Automated summary

An air-stable dicationic Zn2+ complex was synthesized and found to selectively catalyze dehydrogenative borylation and hydroboration reactions of terminal alkynes under different conditions. The mode of action and mechanism of dehydrogenative borylation were investigated using experimental and computational methods.