Table 1.

Catalyst Optimization for the Asymmetric Chlorination of 3-Phenyloxindole 1a.^a

entry	catalyst	solvent	yield (%)b	ee (%)c
1d	-	toluene	< 20	-
2	PA1 purified on silica gel	toluene	99	51
3	PA1 purified on silica gel	DCM	99	48
4	PA1 purified on silica gel	EtOAc	99	50
5	PA1 purified on silica gel	benzene	99	60
6	PA1 purified on silica gel	i-PrOAc	99	80
7e	PA1 purified on silica gel	i-PrOAc	99	90
7e,f	PA1 washed with HCI	i-PrOAc	99	0
9e	Na[P1]	i-PrOAc	99	6
10e	K[P1]	i-PrOAc	99	0
11e	Mg[P1]2	i-PrOAc	99	37
12e	Ca[P1]2	i-PrOAc	99	91
13e	Sr[P1]2	i-PrOAc	99	86
14e	Ba[P1]2	i-PrOAc	99	9
15g	Ca[P1]2	i-PrOAc	99	94

^aReaction conditions: 1a (1.0 equiv), NCS (1.2 equiv), 5 mol % catalyst (based on VAPOL phosphate), with solvent indicated [0.10 M].

^bIsolated yield.

^cEnantiomeric excess determined by chiral HPLC analysis.

^dReaction time of 24 h.

^eReaction performed at [0.050 M].

^fReaction time of 3 h.

^gNCS was added as a [0.12 M] solution in i-PrOAc.