The reaction of mesitylene with ethyl propiolate in the presence of [Pd(dppe)(OAc)2] in TFA at 30 °C for 5 h gave diethyl (2E,4Z)-4-[(2,4,6-trimethylphenyl)methylene]-2-pentenedioate selectively. Screening several bidentate phosphines ligands showed that dppe and dppm ligands are good for the arylbutadiene formation. This reaction was applied to other electron-rich arenes and found to be effective for synthesis of arylbutadienes and extended π-conjugated molecules. The regio- and stereoselective addition of an arene to propiolate was confirmed by NMR and single-crystal X-ray structural analyses of the products, suggesting that the arylbutadiene formation consisted of anti addition of an arene and a metal to the triple bond of ethyl propiolate, followed by syn addition to another molecule of ethyl propiolate. Similarly, the reaction of various arenes with ethyl propiolate in the presence of [Pt(dppe)(OTf)2] catalyst gave arylbutadienes selectively. In the Pd- or Pt-catalyzed reaction of arenes with ethyl propiolate, it was found that a bidentate ligand controlled the reaction to lead the formation of arylbutadienes.
在30°C下,使用[Pd(dppe)(OAc)2]催化剂,在TFA中,间
三甲苯与
乙基丙二酸乙酯反应5小时,选择性地生成了
二乙基(2E,4Z)-4-[(2,4,6-三甲基苯基)亚甲基]-2-
戊二烯二酸酯。筛选多种双齿
膦配体表明,dppe和dppm
配体有利于芳基
丁二烯的形成。此反应应用于其他富电子
芳烃,发现对于芳基
丁二烯和扩展π共轭分子的合成是有效的。通过NMR和单晶X射线结构分析确认了
芳烃对
丙二酸酯的区域和立体选择性加成,表明芳基
丁二烯的形成包括
芳烃和一个
金属对
乙基丙二酸酯三键的反式加成,随后对另一分子
乙基丙二酸酯进行顺式加成。类似地,使用[Pt(dppe)(OTf)2]催化剂,在多种
芳烃与
乙基丙二酸酯的反应中,选择性地生成了芳基
丁二烯。在Pd或Pt催化的
芳烃与
乙基丙二酸酯反应中,发现双齿
配体控制了反应,引导芳基
丁二烯的形成。