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The one-pot reduction-cyclization of 2-nitroanilines and 1,2-diketones to give quinoxalines was investigated. Using indium and an appropriate acid such as acetic acid or indium(III) chloride, various quinoxaline derivatives including 2,3-dialkylquinoxalines, 2,3-diphenylquinoxalines, 2,3-di-2-thiophenylquinoxalines, 2,3-di(pyridin-2-yl)quinoxalines, and dibenzo[ a , c ]phenazines were synthesized in moderate to excellent yield. [ABSTRACT FROM AUTHOR]

Abstract: One-pot reduction-triggered heterocyclizations from 2-nitroanilines or 1,2-dinitroarenes to benzimidazoles were investigated in this study. In the presence of indium/AcOH in ethyl acetate at reflux, reaction of 2-nitroanilines or 1,2-dinitroarenes with R–C(OMe)3 (R=Me, Ph) produced excellent yields of the corresponding benzimidazoles within 30 min to 6 h depending on the substituents of the starting materials. Indium-mediated heterocyclization of 2-nitroanilines to benzimidazole was faster and had better yields than 1,2-dinitroarenes to benzimidazole under similar reaction conditions. [Copyright &y& Elsevier]

Abstract: One-pot reduction-triggered heterocyclizations from 2-nitrophenols to benzoxazoles and from 1-aryl-2-nitroethanones to oxazoles were investigated. In the presence of indium/AcOH in benzene at reflux, 2-nitrophenols and R–C(OMe)3 (R=H, Me, Ph) produced excellent yields of corresponding benzoxazoles within an hour. Similarly, 1-aryl-2-nitroethanones and Ph–C(OMe)3 in the presence of indium/AcOH in acetonitrile transformed into the corresponding oxazoles with good yields. [Copyright &y& Elsevier]

Abstract: Photostimulated tethered free radical reactions for the intramolecular cyclizations towards α-tetralones, N-containing α-tetralone analogues, 3,4,4a,10b-tetrahydro-2H-pyrano[3,2-c]chromen-5-ones and 2,3,4,4a,6,10b-hexahydropyrano[3,2-c]quinolin-5-one were investigated. Photolysis of the t-BuHgX/Dabco with 1-aryl-4-penten-1-ones produced α-tetralones via tert-butyl radical attacks on the terminal, followed by secondary radical attack to the aromatic ring, proton abstraction and electron transfer from the radical anion intermediate to t-BuHgX. At similar conditions, formation of N-containing α-tetralone analogues, 3,4,4a,10b-tetrahydro-2H-pyrano[3,2-c]chromen-5-ones and 2,3,4,4a,6,10b-hexahydropyrano[3,2-c]quinolin-5-one also occurs in reasonable yields. [Copyright &y& Elsevier]