Table 1. Optimization of the reaction conditions.

Entry	Cat a	Additive b	Solvent	Conv. [%]	Yield c
1	A	—	DMSO (0.34 M)	∼35%	— d
2	A	(BnO)2P(O)OH	DMSO (0.34 M)	100	10 a %
3	A	(BnO)2P(O)OH	DMSO (0.34 M)	100	30%
4	A	Benzoic acid	DMSO (0.34 M)	100	8%
5	A	Acetic acid	DMSO (0.34 M)	100	10%
6	A	PTSA	DMSO (0.34 M)	100	0%
7	A	H3PO4	DMSO (0.34 M)	100	40%
8	B	H3PO4	DMSO (0.34 M)	60	—
9	C	H3PO4	DMSO (0.34 M)	75	—
10	A	H3PO4	DMF (0.34 M)	60	—
11	A	H3PO4	ACN (0.34 M)	20	—
12	A	H3PO4	DMSO (0.09 M)	100	65 e %
13	A	H3PO4	DMSO (0.09 M)	100	51 f %
14	A	H3PO4	DMSO (0.09 M)	95	30 g %
15	—	H3PO4	DMSO (0.09 M)	0	—
16	A	H3PO4	DMSO (0.09 M)	0	— h

^a2.5 mol% of catalyst.

^b2 equiv. of additive with respect to 1a.

^cIsolated yields.

^dPhenylisocyanate and benzamide are obtained.

^eReaction conditions: 1a (0.34 mmol, 1 equiv.), 2a (1.7 mmol, 5 equiv.), additives (0.68 mmol, 2 equiv.) and photocatalyst (8.5 μmol, 2.5 mol%) in dry solvent (0.09 M) under N₂ was irradiated with blue light for 4 h.

^f1 mol% of the catalyst used.

^g1 equiv. of N-methylpyrrole.

^hWithout light.