The chemistry of indoles. XIII. Syntheses of substituted indoles carrying an amino, nitro, methoxycarbonyl, or benzyloxy group at the 4-position and their 1-hydroxy derivatives.
The chemistry of indoles. XIII. Syntheses of substituted indoles carrying an amino, nitro, methoxycarbonyl, or benzyloxy group at the 4-position and their 1-hydroxy derivatives.
CLARK, R. D.;REPKE, D. B., J. HETEROCYCL. CHEM., 1985, 22, N 1, 121-125
作者:CLARK, R. D.、REPKE, D. B.
DOI:——
日期:——
The chemistry of indoles. XIII. Syntheses of substituted indoles carrying an amino, nitro, methoxycarbonyl, or benzyloxy group at the 4-position and their 1-hydroxy derivatives.
Various 1-hydroxyindoles carrying a nitro, methoxycarbonyl, or benzyloxy group at the 4 position were prepared by the controlled reduction of 6-substituted trans-β-dimethylamino-2-nitrostyrenes with either aqueous titanium (III) chloride or zinc in aqueous ammonium chloride. The stability of 4-substituted 1-hydroxyindoles decreased in the following order : 4-nitro-»4-methoxycarbonyl->4-benzyloxy-1-hydroxyindole. This result clearly indicates that an electron-withdrawing group at the 4-position can stabilize the 1-hydroxyindole structure. It was also found that 4-hydroxy-and 4-benzyloxy-indole were readily accessible by the reduction of 6-benzyloxy-2-nitrophenyl acetaldehyde. A unique route to 4-or 7-aminoindole from cinnoline is also described.