Regioselective synthesis of 3-acylindolizines and benzo- analogues via 1,3-dipolar cycloadditions of N-ylides with maleic anhydride.
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.
Liu
Yun
Y
Institute of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, PR China.
Zhang
Yan
Y
Shen
Yong-Miao
YM
Hu
Hong-Wen
HW
Xu
Jian-Hua
JH
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
D000475:Alkenes; D007212:Indolizines; D008299:Maleic Anhydrides; D011725:Pyridines; D011804:Quinolines; C035094:indolizine; D009584:Nitrogen; C023666:pyridine