Fischer indole synthesis (3) (sometimes called Fischer indolization) is one of the oldest and most convenient, and it is currently used for a broad range of applications.
Fischer indole synthesis of 2-methoxyphenylhydrazone (5)
(1982) In The Fischer Indole Synthesis. John Wiley and Sons, New York, p.
(1997) A novel method for suppression of the abnormal Fischer indole synthesis. Tetrahedron 53, 8853-8870.
(1999) Thermal cyclization of N-trifluoroacetyl enehydrazines under milder conditions: A novel entry into the Fischer indole synthesis. Tetrahedron Lett.