Table 1.

Optimization of Conditions for Visible-Light Photoredox Olefination

Entry	PC	Base (equiv)	Solvent	Time (h)	Yielda
1	A	Cs2CO3	CH3CN	6	93
2	B	Cs2CO3	CH3CN	6	21
3	C	Cs2CO3	CH3CN	6	89
4	D	Cs2CO3	CH3CN	6	67
5	A	K2CO3	CH3CN	6	93
6	A	NA2CO3	CH3CN	6	61
7b	A	–	CH3CN	6	11
8c	A	K2CO3	CH3CN	6	92
9d	A	K2CO3	CH3CN	6	80
10e	A	K2CO3	CH3CN	6	NR
11	A	K2CO3	CH3CN	4	93
12	A	K2CO3	CH3CN	3	88
13	A	K2CO3	DMF	4	90
14	A	K2CO3	DMA	4	74
15	A	K2CO3	DMSO	4	43
16	A	K2CO3	CH2Cl2	4	45
17f	A	K2CO3	CH3CN	4	84
18g	A	K2CO3	CH3CN	9	90
19h	A	K2CO3	CH3CN	4	Trace
20i	–	K2CO3	CH3CN	4	Trace
21j	A	K2CO3	CH3CN	4	Trace

Reaction conditions: Ar atmosphere and irradiation of visible light with 23-W CFL, 4-bromobenzyl bromide (1a) (1.0 mmol), paraformaldehyde (2a) (2.0 mmol, relative to amount of formaldehyde), triphenylphosphine (PPh₃) (1.5 mmol), photocatalyst (5.0 μmol), base (1.5 mmol), solvent (10 mL), temperature (room temperature ∼25 ^oC), time 3–6 hr, in a sealed Schlenk tube.

PC, photocatalyst; CFL, compact fluorescent light; DMA, N,N-dimethylacetamide; NR, no reaction.

^aIsolated yield.

^bNo base.

^cIn the presence of 2 equiv of PPh₃.

^dIn the presence of 1 equiv of PPh₃.

^eNo PPh₃.

^fUsing aqueous formaldehyde (2b) (37% aqueous solution) (2.0 mmol) instead of paraformaldehyde (2a).

^gUnder irradiation of 5-W blue LED light for 9 hr.

^hThe reaction was carried out in air.

ⁱNo photocatalyst.

^jNo light.