Table 1 Optimization of the reaction conditions^a


entry	variation of standard conditions	yield (%)^b
1	none	78(73)^c
2	PC2 instead of PC1	trace
3	PC3 instead of PC1	45
4	PC4 instead of PC1	n.d.
5	PC5 instead of PC1	n.d.
6	PC6 instead of PC1	n.r.
7	B₂pin₂ instead of B₂cat₂	n.r.
8	DMF instead of DEF	47
9	MeCN instead of DEF	n.r.
10	NMP instead of DEF	27
11^d	Purple LEDs	52
12	Without PC1	n.r.
13	Without light irradiation	n.r.

^aStandard reaction conditions: PC1 (3 mol%), 1a (0.2 mmol), B₂cat₂ 2 (0.8 mmol), DEF (2 mL), blue LEDs (λ_max = 466 nm), ambient temperature, 24 h; then pinacol (4.0 equiv), Et₃N (0.5 mL),1 h. ^bGC yield using biphenyl as internal standard; ^cIsolated yield; ^dλ_max = 390 nm. n.d. = not detected; n.r. = no reaction; DEF = N,N-diethylformamide; DMF = N,N-dimethylformamide; NMP = N-methyl-2-pyrrolidone.

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