Fischer Indole Synthesis
The conversion of aryl hydrazones to indoles; requires elevated temperatures and the addition of Brĝnsted or Lewis acids. Some interesting enhancements have been published recently; for example a milder conversion when N-trifluoroacetyl enehydrazines are used as substrates. (abstract).
Mechanism of the Fischer Indole Synthesis
Aryl Hydrazide beyond as Surrogate of Aryl Hydrazine in the Fischer Indolization: The Synthesis of N-Cbz-indoles, N-Cbz-carbazoles, and N,N'-Bis-Cbz-pyrrolo[2,3-f]indoles
I.-K. Park, S.-E. Suh, B.-Y. Lim, C.-G. Cho, Org. Lett., 2009, 11, 5454-5456.
Three- and Four-Component Syntheses of 3-Arylmethylindoles by Microwave-Assisted One-Pot Heck Isomerization-Fischer Indolization (Alkylation) (HIFI and HIFIA) Sequences
J. Panther, T. J. J. Müller, Synthesis, 2016, 48, 974-986.
Thermal cyclization of N-trifluoracetyl enehydrazines under mild conditions: A novel entry into the Fischer indole synthesis
O. Miyata, Y. Kimura, K. Muroya, H. Hiramatsu, T. Naito, Tetrahedron Lett., 1999, 40, 3601-3604.