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首页> 外文期刊>Chemistry: A European journal >Palladium-Catalyzed Cross-Coupling Reactions of Amines with Alkenyl Bromides:A New Method for the Synthesis of Enamines and Imines
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Palladium-Catalyzed Cross-Coupling Reactions of Amines with Alkenyl Bromides:A New Method for the Synthesis of Enamines and Imines

机译：钯与烯基溴化物的钯催化交叉偶联反应：一种合成烯胺和亚胺的新方法

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摘要

The palladium-catalyzed cross-coupling reaction of alkenyl bromides with secondary and primary amines gives rise to enamines and imines,respectively.This new transformation expands the applicability of palladium-catalyzed C-N bond forming reactions (the Buchwald-Hartwig amination),which have mostly been applied to aryl halides.After screening of different ligands,bases,and solvents,the catalytic combination [Pd_2(dba)_3]/BINAP in the presence of NaOtBu in toluene gave the best results in the cross-coupling of secondary amines with 1-bromostyrene (dba=dibenzylideneacetone,BINAP=2,2'-bis(diphenylphosphino)-1,1'-binaphthyl).The corresponding enamines are obtained cleanly and in nearly quantitative yields.However,steric hindrance seems to be a limitation of the reaction,as amines carrying large substituents are not well converted.The same methodology can be applied to the coupling of secondary amines with 2-bromostyrene.Moreover,the reaction with substituted 2-bromopropenes allows regioselective synthesis of isomerizable terminal enamines without isomerization of the double bond.The best catalytic conditions for the cross-coupling of 1-bromostyrene with primary amines include again the use of the Pd~0/BINAP/NaOtBu system.The reaction gives rise to the expected imines in very short times and with low catalyst loadings A.set of structurally diverse imines can be prepared by this methodology through variations in the structure of both coupling partners.However 2-bromostyrene failed to give good results in this coupling reaction,probably due to product inhibition of the catalytic cycle.Competition experiments of vinyl versus aryl amination reveal that the reaction occurs preferentially on vinyl bromides.
机译：烯基溴化物与仲胺和伯胺的钯催化交叉偶联反应分别产生烯胺和亚胺。这一新的转变扩大了钯催化的CN键形成反应（布赫瓦尔德-哈特维希胺化）的适用性。在筛选了不同的配体，碱和溶剂后，NaOtBu在甲苯中的催化组合[Pd_2（dba）_3] / BINAP在仲胺与1的交叉偶联中获得了最佳结果。 -溴代苯乙烯（dba =二亚苄基丙酮，BINAP = 2,2'-双（二苯基膦基）-1,1'-联萘基）反应，因为带有大取代基的胺不能很好地转化。相同的方法可用于仲胺与2-溴苯乙烯的偶联。此外，与取代的2-溴丙烯的反应允许区域选择性1溴苯乙烯与伯胺交叉偶联的最佳催化条件包括再次使用Pd〜0 / BINAP / NaOtBu体系。可以在很短的时间内并以较低的催化剂负载量获得预期的亚胺通过这种方法，可以通过改变两个偶联配偶体的结构来制备一组结构多样的亚胺。但是，2-溴苯乙烯未能在该偶联反应中获得良好的结果，可能是由于乙烯基胺与芳基胺的竞争实验表明，该反应优先发生在乙烯基溴上。

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