Optimization of conditions for copper-catalyzed reaction of 3-benzyl-1-methylindolin-2-imine hydrochloride (1h) with 2-iodobenzyl bromide (2a) leading to 10b-benzyl-6-methyl-10b,11-dihydro-6H-indolo[2,3-b]quinoline (3h)^a.

Entry	Cat.	Base	Solvent	Yieldb (%)
1	CuI	t BuONa	t BuOH	73
2	CuBr	t BuONa	t BuOH	78
3	CuCl	t BuONa	t BuOH	90
4	Cu2O	t BuONa	t BuOH	75
5	Cu(OAc)2	t BuONa	t BuOH	83
6	Cu(TFA)2	t BuONa	t BuOH	81
7	CuCl	t BuONa	CH3CN	46
8	CuCl	t BuONa	iPrOH	81
9	CuCl	t BuONa	Toluene	42
10	CuCl	t BuONa	1,4-Dioxane	38
11	CuCl	t BuOLi	t BuOH	89
12	CuCl	K 2 CO 3	t BuOH	91
13	CuCl	Cs2CO3	t BuOH	88
14	CuCl	K3PO4	t BuOH	86
15	CuCl	NaOAc	t BuOH	43
16	CuCl	DIPEA	t BuOH	Trace
17c	CuCl	K2CO3	t BuOH	80
18d	CuCl	K2CO3	t BuOH	91

^aReaction conditions: under nitrogen atmosphere, 3-benzyl-1-methylindolin-2-imine hydrochloride (1h) (0.33 mmol, 1.1 equiv.), 2-iodobenzyl bromide (2a) (0.3 mmol, 1.0 equiv.), catalyst (30 μmol, 10 mol%), base (1.2 mmol, 4.0 equiv.), solvent (3.0 mL), temperature (100 °C), time (20 h) in a sealed Schlenk tube.

^bIsolated yield.

^cTemperature (80 °C).

^dTemperature (120 °C).