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. Author manuscript; available in PMC: 2011 Jun 26.
Published in final edited form as: Tetrahedron. 2010 Jun 26;66(26):4687–4695. doi: 10.1016/j.tet.2010.02.050

Table 1.

Survey of acids to promote furoindoline formation.

graphic file with name nihms179917t1.jpg
entry acid source conditions yielda
1 PCl3 benzene, 60 °C < 5%
2 ZnCl2 EtOH, 100 °C < 5%
3 TsOH EtOH, H2O, 60 °C 51%
4 TFA CH3CN, 60 °C 64%
5 5% HCl CH3CN, 60 °C 70%
6 4% H2SO4 CH3CN, 60 °C 87%
7 AcOH AcOH, 60 °C 52%
8 AcOH 1:1 AcOH/H2O, 60 °C 89%b
a

Unless otherwise noted, yields determined by 1H NMR analysis.

b

Isolated yield.