Table 2. Scope of Isatins for Phosphoric acid-catalyzed Spirocyclization.

entry	R	R1	product	method	yield (%)[a]	er[b]
1	CH3	Br	4aa	A	99	91:9
				B	70	82:18
2	CH3	Cl	4ba	A	99	92:8
				B	90	88:12
3	CH3	H	4ca	A	99	88:12
				B	99	95:5
4	CH3	OCH3	4da	A	99	58:42
				B	79	70:30
5	Bn	H	4ea	A	99	82:18
				B	95	97:3
6	PMB	H	4fa	A	72	87:13
				B	87	93:7
7	PMB	Br	4ga	A	86	87:13
				B	81	75:25
8	CH2CCH	F	4ha	A	60	92:8
				B	86	92:8
9	Ph	H	4ia	A	99	85:15
				B	44	97:3
10	Ac	H	4ja	A	87[c]	--
				B	53[c]	--
11	H	H	4ka	A	66	94:6
				B	99	94:6
12	H	Cl	4la	A	99	84:16
				B	88	80:20
13	H	OCH3	4ma	A	84	97:3
				B	92	96:4

Method A: 20 mol % catalyst (R)-8b in CH₂Cl₂ at 23°C for 72-96h.

Method B: 10 mol % catalyst (S)-8d in DMF at 40°C for 24-48h.

^[a]Isolated yield.

^[b]Enantioselectivity determined by chiral phase HPLC.

^[c]Yield is for imine.