Table 1.

Solvent and catalyst screen of the GBB-3CR^a.

Entry	Catalyst	Cat. load (mol %)	Solvent	Reaction time	Yield (%)
1	–	–	EtOH	> 72 h	0
2	In(OTf)3	20	EtOH	15 min	61b
3	InCl3	20	EtOH	15 min	67b
4	TMSCl	20	EtOH	15 min	64b
5	TsOH∙H2O	20	EtOH	15 min	52b
6	HClO4	20	EtOH	15 min	59b
7	TFA	20	EtOH	15 min	74b
8	TFA	20	CH2Cl2	15 min	35c
9	TFA	20	CH2Cl2	20 h	59b
10	TFA	20	CH2Cl2/MeOH 1:1	15 min	68b
11	TFA	20	MeCN	15 min	68b
12	TFA	20	THF	15 min	74b
13	TFA	20	MeOH	15 min	71b
14	TFA	20	H2O	15 min	63c
15	TFA	20	EtOH/H2O 1:1	15 min	79b
16	TFA	1	EtOH/H2O 1:1	36 h	46b
17	TFA	2	EtOH/H2O 1:1	20 h	62b
18	TFA	5	EtOH/H2O 1:1	1 h	75b
19	TFA	10	EtOH/H2O 1:1	25 min	76b

^aReaction conditions: 1a (0.50 mmol), 2a (0.55 mmol), 3a (0.55 mmol), solvent (1 mL), room temperature. ^bIsolated yield after simple filtration. ^cIsolated yield after flash chromatography.