Scope and Mechanism of the PdII-Catalyzed Arylation/Carboalkoxylation of Unactivated Olefins with Indoles
作者:Cong Liu、Ross A. Widenhoefer
DOI:10.1002/chem.200500787
日期:2006.3.1
Stereochemical analyses of the palladium-catalyzed cyclization/carboalkoxylation of both 2- and 3-alkenyl indoles are in agreement with mechanisms involving outer-sphere attack of the indole on a palladium-olefin complex followed by alpha-migratory insertion of CO and methanolysis of the resulting acyl palladium intermediate. CuCl2 functions as the terminal oxidant in this palladium-catalyzed cyclization/carboalkoxylation
在CO中用催化量的[PdCl2(MeCN)2](2; 5 mol%)和化学计量的CuCl2(3当量)在甲醇中处理1-甲基-2-(4-戊烯基)吲哚(5) (1 atm)在室温下放置30分钟,得到(9-甲基-2,3,4,9-四氢-4-咔唑基)乙酸甲酯(6),其分离率为83%。许多2-和3-烯基吲哚经历相似的钯催化的环化/羰基烷氧基化反应,以中等至优异的产率得到相应的多环吲哚衍生物,并具有极好的区域和非对映选择性。在类似条件下,乙烯基芳烃与吲哚进行分子间芳基化/羰基烷氧基化,以中等收率和高区域选择性得到3-(1-芳基-2-羰甲氧基乙基)吲哚。对2-和3-烯基吲哚的钯催化的环化/羰基烷氧基化的立体化学分析与涉及吲哚在钯-烯烃络合物上的外球攻击,随后CO的α-迁移插入和甲醇的甲醇分解的机理一致。生成的酰基钯中间体。在该钯催化的烯基吲哚的环化/羰基烷氧基化反应中,CuCl2用作末端氧化剂,并且还显着提