A General Synthesis of Quinoline-2,5,8(1H)-triones via Acylation of 2,5-Dimethoxyaniline with S-tert-Butyl Thioacetates by Application of the Knorr Cyclization

Pilar López-Alvarado; Carmen Avendaño; J. Carlos Menéndez

doi:10.1055/s-1998-2014

Synthesis 1998; 1998(2): 186-194
DOI: 10.1055/s-1998-2014

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A General Synthesis of Quinoline-2,5,8(1H)-triones via Acylation of 2,5-Dimethoxyaniline with S-tert-Butyl Thioacetates by Application of the Knorr Cyclization

Pilar López-Alvarado^* , Carmen Avendaño, J. Carlos Menéndez

^*Departamento de Química Orgánica y Farmacéutica, Facultad de Farmacia, Universidad Complutense, ES-28040 Madrid, Spain; Fax + 34(91)3 94 18 22; E-mail: josecm@eucmax.sim.ucm.es

Abstract

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An efficient synthesis of quinoline-2,5,8(1H)-triones bearing alkyl groups at C₃ and/or C₄ is described. The reaction sequence employed involves Knorr cyclization of 2,5-dimethoxyanilides into 5,8-dimethoxyquinoline systems, followed by oxidative demethylation with cerium ammonium nitrate. The starting 2,5-dimethoxyanilides were prepared by chemoselective acylation by regioselective alkylation of S-tert-butyl acetothioacetate (1) at C₂ and/or C₄. The introduction of electrophiles other than alkyl groups at C₂ on 1 was also studied.

quinoline-2,5,8(1H)-triones - Knorr cyclization - 2,5-dimethoxyanilides - β-oxo thioesters - regioselective alkylation

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