Table 1. Optimization of the reaction conditions.

Entry	Catalyst	Additive	Solvent	Temperature (oC)	Time (h)	Yield (%)
1	Cu(OTf)2	None	CH3CN	90	5	58
2	CuCl	None	CH3CN	90	5	40
3	Fe(OTf)2	None	CH3CN	90	7	50
4	Zn(OTf)2	None	CH3CN	90	20	47
5	Sc(OTf)3	None	CH3CN	90	20	44
6	Cu(OTf)2	None	CH3CN	70	5	54
7	Cu(OTf)2	None	CH3CN	50	24	Trace
8	Cu(OTf)2	None	DCM	70	24	34
9	Cu(OTf)2	None	EtOAc	70	24	NR*
10	Cu(OTf)2	None	THF	70	24	—†
11	Cu(OTf)2	C6H5COOH	CH3CN	70	4	60
12	Cu(OTf)2	CH3COOH	CH3CN	70	3	61
13	Cu(OTf)2	CF3SO3H	CH3CN	70	4	40
14	Cu(OTf)2	CF3COOH	CH3CN	70	5	78
15	None	None	CH3CN	70	24	NR*
16	None	None	CH3CN	130	10	32

Reaction conditions: 1a (0.5 mmol), NFSI (1.5 equiv., 0.75 mmol), CH₃OH (3 equiv., 1.5 mmol), catalysts (10 mol %), additives (1 equiv., 0.5 mmol), anhydrous solvents (2 ml), N₂ atmosphere. Isolated yield.

^*NR, no reaction.

^†HN(SO₂Ph)₂ was identified.