1. The Fischer Indole Synthesis.
2. Chem. Rev., 69, 227 (1969).
3. The formation of isomers has been demonstrated for the cyclization of those phenylhydrazones having a meta-carboxyl (3a, 3b), nitro (3c), bromo (3d), chloro (3b), and methoxy (3d) substituent. However, the m-hydroxy- (3f) and methoxy phenylhydrazones (3g) of cyclohexanone are reported to afford only one isomer, which was subsequently demonstrated to be the corresponding 7-substituted-1,2,3,4-tetrahydrocarbazole (3h).
4. W. M. Collar and S. G. P. Plant, J. Chem. Soc., 808 (1926);
5. (b) R. C. G. Moggridge and S. G. P. Plant, J. Chem. Soc., 1125 (1937);