A high hydroarylation activity of K2PtCl4/AgOTf catalyst in the reaction of propiolic acid with unactivated and activated arenes

A mixed catalyst K2PtCl4/AgOTf showed the highest activity for hydroarylation of propiolic acid, among palladium and platinum catalysts. This catalyst was effective for hydroarylation with less reactive benzene to give cis-cinnamic acid in good yield. The hydroarylation with toluene gave a higher yield of hydroarylation products than that with benzene and resulted in ortho/para orientation with an almost statistical ratio, suggesting that the result is very close to that of the Friedel-Crafts alkylation with methyl bromide or p-nitrobenzyl chloride. Hydroarylation of propiolic acid with other electron-rich arenes proceeded efficiently in the presence of the K2PtCl4/AgOTf catalyst in trifluoroacetic acid forming cis-cinnamic acids in good to high yields. This method was also applied to hydroarylation of ethyl propiolate.

Graphical abstractA mixed catalyst K2PtCl4/AgOTf showed an extremely high activity for hydroarylation of propiolic acid to form cis-cinnamic acids in good to high yields. This catalyst was effective even in the reaction with less reactive benzene and toluene to give cis-cinnamic acids in good yield.Figure optionsDownload full-size imageDownload as PowerPoint slide