Table 1.

ZnX₂-promoted deprotective heterocyclization of N-Boc-2-(hex-1-in-1-yl)-1H-benzo[d]imidazole 1a under different conditions ^a.

Entry	ZnX2 (Equiv)	T (°C)	Solvent	Concentration of 1a b	Conversion of 1a (%) c	Yield of 2a (%) d
1	ZnBr2 (1)	25	CH2Cl2	0.5	51	25
2	ZnBr2 (1)	25	MeOH	0.5	3	0
3	ZnBr2 (1)	25	acetone	0.5	12	Traces
4	ZnBr2 (0.5)	25	CH2Cl2	0.5	9	6
5	ZnBr2 (1.5)	25	CH2Cl2	0.5	100	72
6	ZnBr2 (2)	25	CH2Cl2	0.5	100	70
7	ZnBr2 (1)	25	CH2Cl2	1.0	62	33
8	ZnBr2 (1)	25	CH2Cl2	0.2	42	10
9	ZnBr2 (1)	40	CH2Cl2	0.5	100	63
10	ZnBr2 (1.5)	40	CH2Cl2	1.0	100	79
11	ZnCl2 (1.5)	40	CH2Cl2	1.0	100	82
12	ZnI2 (1.5)	40	CH2Cl2	1.0	100	77

^a All reactions were carried out for 3 h. ^b Mmol of starting 1a per mL of solvent. ^c Based on unreacted 1a, upon isolation from the reaction mixture. ^d Isolated yield based on starting 1a.