Indole aus cyclischen 1.3-Dicarbonylverbindungen mit substituierter 2-Stellung

Indoles from Cyclic 1,3-Dicarbonyl Compounds with Substituents at Position 2 The phenylhydrazones 1b–g, 11 of cyclohexane-1,3-diones alkylated at C-2 suffer β-dicarbonyl fission under the conditions of the Fischer indole synthesis. A lactam ring is closed and the pyrido1,2-a]indoles 6b–g, 12 are formed. This reaction also applies to heterocyclic diones (13→14) . The carboxylic acids corresponding to the lactams of type 5 cannot be isolated as intermediates, nor are they obtained in the course of the synthesis of 6b and c from 5-(phenylhydrazono)-n-heptanoic and 5-(phenylhydrazono)-n-octanoic acid. The reaction pathway is discussed.