Table 1. Optimization of the Reaction Conditions for the Reductive Cyclization.

entry	solvent	T (°C)	time	base	yield (%)
1	THF	70	5 h	CH(NMe)3 (5 equiv)	0
2	THF	70	5 h	CH(NMe)2Ot-Bu (3 equiv)	0
3	DMF	rt	18 h	TBAF (2 equiv) + HMPA (6 equiv)	13
4	DMF	150	4 h	K2CO3 (2 equiv) + CuI (1 equiv)	37
5	DMF	150	4 h	K2CO3 (2 equiv)	36
6	DMF	150a	15 min	K2CO3 (2 equiv)	40
7	DMF	150a	15 min	K2CO3 (4 equiv)	44
8	NMP	150a	15 min	K2CO3 (4 equiv)	50
9	NMP	100a	15 min	K2CO3 (4 equiv)	29
10	NMP	200a	15 min	K2CO3 (4 equiv)	34
11	NMP	150a	15 min	K2CO3 (10 equiv)	55
12	NMP	150	1 h	K2CO3 (10 equiv)	50
13	NMPb	150	1 h	K2CO3 (10 equiv)	82
14c	NMPb	150	1 h	K2CO3 (10 equiv)	87

^aUse of microwaves.

^bConcentration = 0.01 M.

^cThe reaction was carried out on a 1 mmol scale.