Regioselective synthesis of 3-acylindolizines and benzo- analogues via 1,3-dipolar cycloadditions of N-ylides with maleic anhydride

• Published in: Organic & biomolecular chemistry Vol. 8; no. 10; pp. 2449 - 2456
• Main Authors: Liu, Yun, Zhang, Yan, Shen, Yong-Miao, Hu, Hong-Wen, Xu, Jian-Hua
• Format: Journal Article
• Language: English
• Published: CAMBRIDGE Royal Soc Chemistry 01.01.2010
• Subjects: Alkenes - chemistry; Chemistry; Chemistry, Organic; Indolizines - chemical synthesis; Indolizines - chemistry; Maleic Anhydrides - chemistry; Nitrogen - chemistry; Physical Sciences; Pyridines - chemistry; Quinolines - chemistry; Science & Technology; Stereoisomerism; Substrate Specificity; CATALYZED CYCLOISOMERIZATION; NITROGEN-BRIDGED HETEROCYCLES; ONE-POT SYNTHESIS; FUSED HETEROCYCLES; SUBSTITUTED INDOLIZINES; PYRROLE-CONTAINING HETEROCYCLES; EFFICIENT SYNTHESIS; AZOMETHINE YLIDES; LAMELLARIN-ALPHA 20-SULFATE; HETEROAROMATIC-COMPOUNDS
• ISSN: 1477-0520; 1477-0539
• DOI: 10.1039/c000277a

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.