The palladium-catalyzed reaction of arenediazonium tetrafluoroborates with methyl 4-hydroxy-2-butenoate in MeOH under mild conditions gives 4-arylbutenolides usually in good to high yields through a domino vinylic substitution/cyclization process. The reaction tolerates a variety of useful substituents including the whole range of halogen substituents, nitro, ether, cyano, keto, and ester groups and can be performed as a one-pot process generating the arenediazonium salt in situ. By using this method, the marine antibiotic rubrolide E has been synthesized via an expeditious and efficient sequential protocol that omits the isolation of the butenolide intermediate (two operative steps, 52% overall yield).
在温和的条件下,MeOH 中的四
氟硼酸腙与
4-羟基-2-丁烯酸甲酯在
钯催化下发生反应,通过多米诺
乙烯基取代/环化过程,通常可以得到收率很高的 4-芳基
丁烯酸酯。该反应可容忍各种有用的取代基,包括各种卤素取代基、硝基、醚基、
氰基、酮基和酯基,并可作为一种单锅工艺进行,在原位生成均二
甲苯盐。利用这种方法,我们通过一个快速高效的顺序方案合成了海洋抗生素红环内酯 E,省去了
丁烯内酯中间体的分离过程(两个操作步骤,总产率为 52%)。