Table 2.

Optimization reaction conditions of Et₃B-hexane induced radical addition of 4-methoxy-3-nitrobenzyl thiol (3) to 2,4,6-trimethoxyphenyl acetylene (7)^a

Entry	Solvent	Temp (°C)	Time (h)	Yieldb (%)	Z/Ec
1	Benzene	25	2	82	86 : 14
2	Benzene	5	2	75	78 : 22
3	Benzene + 4 eq. methanold	25	2	92	0 : 100
4	Toluene	25	2	85	88 : 12
5	Toluene	0	3	80	79 : 21
6	Toluene	−20	4	75	86 : 14
7	Toluene + 4 eq. methanold	0	2	95	0 : 100
8	Acetonitrile	25	3	82	72 : 28
9	1,4-Dioxane	25	3	60	48 : 52
10	DCM	25	0.5	85	58 : 42
11	DCM	−30	1	88	91 : 9
12	DCM	−78	8	68	100 : 0
13	THF	25	4	80	62 : 38
14	NMP	25	2	85	63 : 37
15	DMSO	25	2	60	8 : 92
16	DMF	25	2	72	28 : 72

^aUnless noted, all the reactions were carried out with 3 (1.2 mmol), 7 (1.0 mmol), base (1.2 mmol) in 10 mL of solvent at indicated time and temperature.

^bYield of isolated product.

^cZ/E ratio was determined by the ¹H NMR spectrum of crude products.

^dMethanol was added to the reaction mixture before Et₃B-hexane addition.