Reaction modes and mechanism in indolizine photooxygenation reactions

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	Reaction modes and mechanism in indolizine photooxygenation reactions
	Li, Y ; Hu, HY ; Ye, JP ; Fun, HK ; Hu, HW ; Xu, JH
刊名	JOURNAL OF ORGANIC CHEMISTRY
	2004-04-02
卷号	69 期号:7 页码:2332-2339
ISSN号	0022-3263
英文摘要	Photooxygenations of 1,2-, 1,3-, and 2,3-di- and 1,2,3-trisubstituted indolizines 1a-1f under different reaction conditions in methanol and acetonitrile have been investigated to establish the general reaction pattern and mechanism in indolizine photooxygenation in view of the influence of the ring substituents and substitution pattern. Photooxygenations of 1-acyl-2-phenylindolizines 1a and 1b and 1,3-dibenzoyl-2-phenylindolizine (1d) are self-sensitized, while those of 1-(p-nitrobenzoyl)2-phenylindolizine (1c) and 2-phenyl-3-(p-chlorobenzoyl)indolizine (1e) need to be sensitized by rose bengal (RB) or methylene blue (MB). These reactions proceed via a singlet oxygen mechanism yet follow different pathways in methanol and in acetonitrile, with peroxidic zwitterion D (in methanol) and dioxetane E across the indolizine C2-C3 bond (in acetonitrile) as the intervening intermediates. Methanol trapping of the peroxidic zwitterion results in C3-N bond cleavage and pyrrole ring opening to give the corresponding (E)- and (Z)-3-(2-pyridinyl)-3-benzoylpropenoic acid methyl esters (2 and 3) and 4-(2-pyridinyl)-3-phenyl-5-aryl-5-hydroxyfuran-2-one (4) as products in methanol, while O-O bond homolysis of the dioxetane furnishes 3-(2-pyridinyl)-3-benzoyl-2-phenyloxirane-2-carboxaldehyde (6) and 1-(6-methyl-2-pyridinyl)-2-phenylethanedione (5) as products in acetonitrile. 3-Benzoyl-1-indolizinecarboxylic acid methyl ester (If) is unreactive toward singlet oxygen; however, it could be photooxygenated under electron transfer conditions with 9,10-dicyanoanthracene (DCA) as a sensitizer. This reaction takes place by the combination of the indolizine cation radical with the superoxide anion radical (or molecular oxygen) to give the pyridine ring oxidized methyl 3-benzoyl-5-methoxy-8-hydroxy-1-indolizinecarboxylate (9f), dimethyl 2-(2-pyridinyl)fumarate (8f), and dimethyl 2-(2-pyridinyl)maleate (7f) as products.
语种	英语
出版者	AMER CHEMICAL SOC
WOS记录号	WOS:000220506200015
内容类型	期刊论文
源URL	[http://ir.iccas.ac.cn/handle/121111/81993]
专题	中国科学院化学研究所
通讯作者	Xu, JH
作者单位	1.Nanjing Univ, Dept Chem, Nanjing 210093, Peoples R China 2.Chinese Acad Sci, Inst Chem, Beijing 100080, Peoples R China 3.Univ Sains Malaysia, Sch Phys, Xray Crystallog Unit, George Town, Malaysia
推荐引用方式 GB/T 7714	Li, Y,Hu, HY,Ye, JP,et al. Reaction modes and mechanism in indolizine photooxygenation reactions[J]. JOURNAL OF ORGANIC CHEMISTRY,2004,69(7):2332-2339.
APA	Li, Y,Hu, HY,Ye, JP,Fun, HK,Hu, HW,&Xu, JH.(2004).Reaction modes and mechanism in indolizine photooxygenation reactions.JOURNAL OF ORGANIC CHEMISTRY,69(7),2332-2339.
MLA	Li, Y,et al."Reaction modes and mechanism in indolizine photooxygenation reactions".JOURNAL OF ORGANIC CHEMISTRY 69.7(2004):2332-2339.