Scheme 2. Dehydrogenative Borylation of Terminal Alkynes Catalyzed by [L¹ZnH]₂ Precatalyst(I)^a.

Reaction conditions: terminal alkynes (0.3 mmol, 1.0 equiv.), pinacolborane (0.315 mmol, 1.05 equiv.), precatalyst I (1.5 mol %), at rt under N₂.

Preparative-scale reaction: 1 mmol of terminal alkynes, precatalyst I (1.5 mol %), 1.05 mmol of HBpin, 6 h, rt.

For 2a, 2c, and 2i, 1 mol % precatalyst was used and stirred for 1, 1.5, and 0.8 h, respectively, and the NMR yield was determined by ¹H NMR spectroscopy using mesitylene as the internal standard.

For 2n, NMR yield was determined by ¹H NMR spectroscopy using mesitylene as the internal standard.

For 2o, pinacolborane (0.63 mmol, 2.1 equiv.) was used and stirred for 12 h.

For 2x, stirred for 2 h. Based on alkyne consumption, the NMR yield was determined by ¹H and ¹¹B NMR spectroscopy and identified the Bpin peak to confirm the product.