Preparation of indoles and oxindoles from N-(tert-butoxycarbonyl)-2-alkylanilines

Article abstract of DOI:10.1055/s-1991-26597

Treatment of dilithiated N-(tert-butoxycarbonyl)anilines 1 with dimethylformamide or carbon dioxide furnishes intermediates 3, 5, that are easily converted to N-(tert-butoxycarbonyl)indoles 4 and oxindoles (indol-2(3H)-ones, 7), respectively. Condensation of dilithiated 1 with N-methoxy-N-methylamides provides ketones 9 which are cyclized upon trifluoroacetic acid treatment to either 2-substituted 1-(tert-butoxycarbonyl)indoles 10 or 2-substituted indoles 11 depending on the reaction time. This general methodology has been applied to efficient synthesis of 1,2-alkyl-bridged indoles 12, 1,3,4,5-tetrahydrobenz[c,d]indole (16), 2a,3,4,5-tetrahydrobenz[c,d]indol-2(1H)-one (18), and 1-(tert-butoxycarbonyl)1H-pyrrolo[2,3-b]pyridine (21).