Table 2.

Optimization for in situ generation of (1H-indol-3-yl)methyl electrophile from 7a and its nucleophilic substitution with NaN₃ in a microflow reactor.

Entry	Reagent	X (Equiv.)a	Time (s)	Yield (%)b
				3b	7a
1	PBr3	0.500	0.02	77	Trace
2	PCl3	0.500	0.02	52	4
3	POCl3	0.500	0.02	n.d.	>99
4c	AcBr	1.50	0.02	4	61
5c	AcCl	1.50	0.02	n.d.	>99
6c	Ac2O	1.50	0.02	n.d.	67
7c	Tf2O	1.50	0.02	8	38
8c	MsCl	1.50	0.02	29	41
9c	TsCl	1.50	0.02	n.d.	n.d.
10	SOBr2	0.750	0.02	7	23
11	SOCl2	0.750	0.02	15	16
12	PBr3	0.500	0.05	60	n.d.
13	PBr3	0.500	0.1	54	n.d.
14	PBr3	0.500	0.5	20	n.d.
15	PBr3	0.350	0.02	84	n.d.
16d	PBr3	0.350	0.02	74	n.d.
17e	PBr3	0.350	0.02	93 ± 2f	n.d.
18e,g	PBr3	0.350	10	n.d.f	n.d.

^aThe reagent quantities were changed based on the reaction mechanism. Theoretically, 1 equiv. of PBr₃, PCl₃, or POCl₃ can convert 3 equiv. of alcohol to the alkyl halide, 1 equiv. of SOBr₂, or SOCl₂ can convert 2 equiv. of alcohol, and 1 equiv. of AcBr, AcCl, Ac₂O, Tf₂O, MsCl, or TsCl can convert equimolar quantities of alcohol.

^bYields were determined by ¹H NMR analysis using 1,1,2-trichloroethane as an internal standard.

^cNEt₃ was added with a solution of 7a instead of a solution of NaN₃.

^dThe reaction was carried out at 0 °C.

^e0.0500 M solution of 7a was used.

^fThree independent experiments were performed.

^gReaction mixture was magnetically stirred (1000 rpm) under batch conditions.