Investigation of reaction conditions^a.

Entry	Variations from the standard conditions	Yield of 4a (%)
1	None	84 (74)b
2	CuCN instead of CuCl	80
3	MeIPrCuCl instead of CuCl/xantphos	21
4	MeIPrCuCl instead of CuCl	33
5	IMesCuCl instead of CuCl/xantphos	12
6	DPPP instead of xantphos	61
7	DPPF instead of xantphos	65
8	DPEphos instead of xantphos	42
9	LiOtBu instead of NaOtBu	Trace
10	KOtBu instead of NaOtBu	Trace
11	NaOMe instead of NaOtBu	<10
12	1.5 equiv. of NaOtBu instead of 2.5 equiv.	46
13	THF instead of toluene	18
14	80 °C instead of 100 °C	76
15	10 bar CO instead of 20 bar	79

^aStandard conditions: 1a (0.2 mmol, 1.0 equiv.), B₂pin₂ (0.24 mmol, 1.2 equiv.), CuCl (10 mol%), ligand (10 mol%), NaO^tBu (0.5 mmol, 2.5 equiv.), CO (20 bar), toluene (1.0 mL), 100 °C, 24 h; yields are determined by GC analysis using hexadecane as the internal standard.

^bIsolated yield.