Copper-catalyzed cross-coupling of amides and potassium alkenyltrifluoroborate salts: a general approach to the synthesis of enamides
作者:Yuri Bolshan、Robert A. Batey
DOI:10.1016/j.tet.2010.03.076
日期:2010.7
Potassium alkenyltrifluoroborate salts undergo coupling with amides to give enamides using a catalytic amount of Cu(OAc)2 under mild oxidative conditions. The air and water stable alkenyltrifluoroborate salts offer a practical alternative to the use of alkenyl halides and alkenylboronic acids as cross-coupling partners. A range of amides participate in the cross-coupling, including heterocyclic amides
链烯基三氟硼酸钾盐与酰胺偶合以在温和的氧化条件下使用催化量的Cu(OAc)2生成酰胺。空气和水稳定的烯基三氟硼酸酯盐提供了一种实用的替代方法,可替代使用烯基卤化物和烯基硼酸作为交叉偶联伴侣。多种酰胺参与交叉偶联,包括杂环酰胺,酰亚胺,氨基甲酸酯,苯甲酰胺和乙酰胺。优化研究确定了两组条件,最适合于高p K a或低p K a酰胺底物。较低的p K a在4Å分子筛,10 mol%的Cu(OAc)2和20 mol%的N-甲基咪唑的存在下,使用二氯甲烷溶剂系统,酰胺底物效果最佳。在4Å分子筛和10 mol%Cu(OAc)2的存在下,使用1:1二氯甲烷/ DMSO溶剂系统的“无配体”方案,较高的p K a酰胺底物效果最佳。交叉偶联反应立体定向地发生,并保留了烯基三氟硼酸盐的烯构型。所采用的温和的反应条件可耐受各种功能,包括硝基,乙缩醛,烷基和芳基卤化物,以及α,β-不饱和羰基。最后,研究了铜源的重要性和微量杂质的存在。
Enamide Synthesis by Copper-Catalyzed Cross-Coupling of Amides and Potassium Alkenyltrifluoroborate Salts