title: Regioselective synthesis of 3-acylindolizines and benzo- analogues via 1,3-dipolar cycloadditions of N-ylides with maleic anhydride.
abstract: 3-Acylindolizines (5a-5f) and their benzo- analogues 1-acylpyrrolo[1,2-a]quinolines (6a-6f) and 1-acylpyrrolo[2,1-a]isoquinolines (7a-7i) are regioselectively synthesized by a convenient one pot reaction of the corresponding pyridinium (quinolinium, isoquinolinium) ylide with maleic anhydride (MA) in the presence of the mild oxidant tetrakispyridinecobalt(ii) dichromate (TPCD). These reactions proceed via a tandem reaction sequence of 1,3-dipolar cycloaddition of azomethine ylide with MA, anhydride hydrolysis and oxidative bisdecarboxylation of the primary cycloadducts followed by dehydrogenative aromatization of the dihydroindolizines. TPCD serves as both decarboxylation and dehydrogenation reagent in the reactions. These results show that TPCD is a promising new reagent for bisdecarboxylation of aliphatic carboxylates.
authors.affiliation: Institute of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, PR China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Liu
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yong-Miao
authors.initials: YM
authors.lastname: Shen
authors.forename: Hong-Wen
authors.initials: HW
authors.lastname: Hu
authors.forename: Jian-Hua
authors.initials: JH
authors.lastname: Xu
mesh_terms: D000475:Alkenes / Q000737:chemistry; D007212:Indolizines / Q000138:chemical synthesis* / Q000737:chemistry*; D008299:Maleic Anhydrides / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry; D011804:Quinolines / Q000737:chemistry*; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D000475:Alkenes; D007212:Indolizines; D008299:Maleic Anhydrides; D011725:Pyridines; D011804:Quinolines; C035094:indolizine; D009584:Nitrogen; C023666:pyridine