An efficient synthesis of 4-(phenylsulfonyl)-4H-furo[3,4-b]indoles.
The fused heterocycle 4-(phenylsulfonyl)-4H-furo[3,4-b]indole, which is an indole-2,3-quinodimethane synthetic analogue, is prepared in five steps from indole in 46% yield. A similar sequence is used to synthesize C-3 derivatives (3-methyl, 3-phenyl, and 3-heptyl). Thus, indole-3-carbaldehyde (1) is protected as the N-phenylsulfonyl derivative 2 and converted to the ethylene acetal 6. Lithiation at C-2 followed by treatment with an aldehyde affords the expected hydroxy acetals 7 and 8. Exposure to acid effects cyclization to the furoindoles 5 and 9. Furthermore, C-1 lithiation of furo[3,4-b]indole 9c followed by treatment with methyl iodide affords disubstituted furo[3,4-b]indole 10.
Gribble
Gordon W
GW
Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755-3564, USA. grib@dartmouth.edu
Jiang
Jun
J
Liu
Yanbing
Y
D007211:Indoles / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D013057:Spectrum Analysis
D007211:Indoles