A mild, simple, and efficient approach to the synthesis of some novel 7-benzylidene-2,3-diphenyl-3,3a,4,5,6,7-hexahydro-2H-indazole derivatives

Figures & data

Scheme 1. Synthesis of 7-benzylidene-2,3-diphenyl-3,3a,4,5,6,7-hexahydro-2H-indazole derivatives.

Table 1. Synthesis of 3f in the presence of various catalysts.

Entry	Catalyst	Reaction conditions	Time	Yield (%)
1	None	EtOH/reflux	36 (hours)	45
2	Et3N	EtOH/reflux	18 (hours)	52
3	NaOH	EtOH/reflux	18 (hours)	60
4	DBU	EtOH/reflux	12 (hours)	70
5	DABCO	EtOH/reflux	10 (hours)	73
6	DABCO	H2O/reflux	24 (hours)	trace
7	DABCO	EtOAC/reflux	24 (hours)	78
8	None	Solvent-free 120 (°C)	2 (hours)	trace
9	Et3N	Solvent-free 120 (°C)	1 (hour)	62
10	NaOH	Solvent-free 120 (°C)	45 (min)	78
11	DBU	Solvent-free 120 (°C)	30 (min)	80
12	DABCO	Solvent-free 120 (°C)	20 (min)	82

Table 2. DABCO catalyzed synthesis of some new indazole derivatives.

Entry	Product	Ar	Z	Time (min)	Yield (%)	Mp(°C)
1	3a	C6H5	CH2	12	97	136–138
2	3b	4-Me-C6H4	CH2	15	92	141–143
3	3c	2-Cl-C6H4	CH2	11	95	156–158
4	3d	4-Cl-C6H4	CH2	10	98	174–176
5	3e	2,3-Cl2-C6H3	CH2	15	99	202–204
6	3f	4-Me-C6H4	CH(Me)	20	82	165–167
7	3g	4-Cl-C6H4	CH(Me)	17	85	163–164