化学
脱氢
催化作用
芳构化
苯甲醇
钯
酒
基质(水族馆)
组合化学
动力学同位素效应
有机化学
光化学
氘
地质学
物理
海洋学
量子力学
作者
Taku Nakayama,Shogo Harada,Shoko Kikkawa,Hidemasa Hikawa,Isao Azumaya
标识
DOI:10.1002/ajoc.202200510
摘要
Abstract We report a synthesis of imidazoquinolines via dehydrogenative coupling of 3,4‐diaminoquinolines with benzylic alcohols utilizing our π‐benzylpalladium(II) system in water. Readily available benzylic alcohols initially undergo catalytic dehydrogenation to form benzaldehydes, which are then reacted with 3,4‐diaminoquinolines via sequential cyclocondensation/aromatization, leading to the formation of imidazoquinolines. This experimentally simple and practical one‐pot procedure provides direct access to the desired products without adding strong bases, toxic oxidants or other additives. Several experiments were carried out toward an understanding of the reaction mechanism to propose plausible catalytic cycles. The dehydrogenative coupling was found to be first order with respect to the benzyl alcohol and Pd catalyst, and zero order with respect to the 3,4‐diaminoquinoline substrate. A kinetic isotope effect of 3.1 was observed by separately determining the reaction rates of benzyl alcohol and benzyl‐α,α‐ d 2 alcohol. Water molecules accelerate the catalytic dehydrogenative coupling, suggesting that they act as a proton donor to activate the benzylic alcohols by a hydrogen‐bonding network.
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