Optimization of the tandem imine formation via auto-hydrogen transfer from benzyl alcohol to nitrobenzene.

Entrya	Catalyst (mol%)	Solvent	Base	Temperature (°C)	Time (h)	Isolated yield (%)
1	2	—	K2CO3	100	5	42
2	2	—	Et3N	100	24	Trace
3	2	—	Na2CO3	100	24	35
4	2	—	KOH	100	9	95
5	2	—	NaOH	100	9	86
6	2	—	—	100	6	30
7	2	EtOH	KOH	65	3	22
8	2	H2O	KOH	80	24	0
9	2	Acetonitrile	KOH	68	24	Trace
10	2	Benzyl alcohol	KOH	100	7	81
11	2	n-Hexane	KOH	50	5	35
12	2	Toluene	KOH	90	3	32
13	2	Ethyl acetate	KOH	60	24	Trace
14	2	—	KOH	r.t.	24	Trace
15	2	—	KOH	65	7	56
16	1	—	KOH	100	10	92
17	0.5	—	KOH	100	6	63
18	0	—	KOH	100	24	21
19b	1	—	KOH	100	24	43
20c	1	—	KOH	100	24	30
21d	1	—	KOH	100	10	0e
22f	1	—	KOH	100	10	0
22g	1	—	KOH	100	10	90
23h	1	—	KOH	100	12	87

^aReaction conditions: nitrobenzene (0.5 mmol, except for entry 21), benzyl alcohol (0.5 mmol, except for entry 22), base (0.5 mmol, except for entry 6), solvent (3 mL, entries 7–13).

^bCuCl₂·2H₂O was used as a catalyst.

^cIsatin Schiff base-γ-Fe₂O₃ as a catalyst.

^dWithout nitrobenzene.

^eBenzaldehyde was obtained as the only product in 60% yield.

^fWithout benzyl alcohol.

^gUnder O₂.

^hUnder Ar.