Development of a Pd-catalyzed Selective synthetic Method for Polysubstituted Benzenes

点击翻译按钮获取中文摘要

In this study, we developed a novel synthetic method for polysubstituted benzenes, which is based on the key reaction of alkynes with π-allylpalladium complexes.(1)While there is few reports on the insertion of alkynes into π-allylpalladium complexes, we found that the insertion proceeds smoothly if the complex has a weak ligand, and utilized it for catalysis. In the catalysis, the ligating ability of leaving groups on allylating agents is quite important. Using allyl tosylate as an allylating compound, the reaction proceeded effectively. In this reaction, penta-substituted benzenes were obtained form one molecule of allyl tosylate and two moleculae of internal alkynes in moderate to high yields. Using terminal, alkynes, trisubstituted benzenes were formed.(2)All results in this study are consistent with the mechanism that includes the insertion of alkynes into π-allylpalladium complexes as a key step.(3)The addition of p-toluenesulfonic anhydride made an employment of allylis alcohols possible. The fact increases the usability of the catalysis because allylic alcohols are cheaper and more available than other allylic compounds.(4)Being carried out under carbon monoxide atmosphere, the reaction afforded cyclopentenones instead of arenes. Using alkenes instead of alkynes, the allylic alkenylation of allylic compounds took place.