Optimization of the dihydrosilylation reaction of alkynes^a.

Entry	Si–H combinations	3	4	5
1b,c	2a	76%	—	<5%
2c	2a	68%	—	29%
3	2a/2b = 1 : 1	ND	66%	34%
4	2a/2c = 1 : 1	ND	>95% (92%)	ND
5d	2a/2c = 1 : 1	ND	>95%	ND

^aReaction conditions: 1a (0.4 mmol), EtMe₂SiH (2a, 0.60 mmol), Si–H (2a–2c, 0.60 mmol), B(C₆F₅)₃ (0.04 mmol), in dichloromethane (1.0 mL). Yields were determined by NMR analysis; isolated yield in parentheses.

^b5 mol% B(C₆F₅)₃.

^cWith 3.0 equiv. of 2a.

^dAt −40 °C.