PALLADIUM COMPLEX-CATALYZED REDUCTIVE N-HETEROCYCLIZATION OF NITROARENES - NOVEL SYNTHESIS OF INDOLE AND 2H-INDAZOLE DERIVATIVES
PALLADIUM COMPLEX-CATALYZED REDUCTIVE N-HETEROCYCLIZATION OF NITROARENES - NOVEL SYNTHESIS OF INDOLE AND 2H-INDAZOLE DERIVATIVES
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DOI：
10.1021/jo00091a026
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发表时间：
1994-06-17
影响因子：
3.6
通讯作者：
WATANABE, Y
中科院分区：
文献类型：
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作者：
AKAZOME, M;KONDO, T;WATANABE, Y
二氯双(三苯基膦)钯(PdCl2(PPh(3))(2))-氯化锡(II)(SnCl2)体系在20 kg·cm(-2)初始一氧化碳压力下于100℃反应16 h，对各种2-硝基苯乙烯和N-(2-硝基亚苄基)胺衍生物的还原N-杂环化表现出较高的催化活性，得到相应的产物吲哚和2H-吲唑衍生物的收率良好。例如，通过2-硝基芪的还原N-杂环化得到2-苯基吲哚，收率75%。类似地，通过 N-(2-硝基亚苄基)丙胺的还原性 N-杂环化，可以容易地制备 2-丙基-2H-吲唑，产率 83%。基于氘标记实验和吲哚骨架构建中烷基重排的研究，提出了用于本反应的氮宾中间体。一氧化碳有效地充当硝基的脱氧剂以提供氮宾中间体。
The dichlorobis(triphenylphosphine)palladium (PdCl2(PPh(3))(2))-tin(II) chloride (SnCl2) system shows high catalytic activity for the reductive N-heterocyclization of various 2-nitrostyrene and N-(2-nitrobenzylidene)amine derivatives when employed at 100 degrees C for 16 h under 20 kg cm(-2) of initial carbon monoxide pressure, to give the corresponding indole and 2H-indazole derivatives in good yield. For example, 2-phenylindole was obtained in 75% yield from the reductive N-heterocyclization of 2-nitrostilbene. Similarly, 2-propyl-2H-indazole was readily prepared in 83% yield by the reductive N-heterocyclization of N-(2-nitrobenzylidene)propylamine. A nitrene intermediate for the present reaction is proposed on the basis of deuterium-labeling experiments and the investigation of alkyl rearrangement in the construction of the indole skeleton. Carbon monoxide effectively operates as a deoxygenating agent of the nitro group to afford a nitrene intermediate.