A Convenient Synthesis of 3,3-Bis(thienyl)propionic Acids by Platinum (Ii)-Catalyzed Reaction of Thiophenes with Propiolic Acids

Platinum(II)-catalyzed hydroarylation of propiolic acids was applied to thiophenes, and we found that the reaction with thiophenes predominantly afforded double thienylated products. Reaction of thiophenes with ethyl propiolate proceeded efficiently in the presence of K2PtCl4 (2 mol%) and AgOTf (8 mol%) in trifluoroacetic acid under mild conditions to give ethyl 3,3-bis(substituted thienyl)propionates in good yields. The same platinum(II)-catalyzed reaction with propiolic acid instead of the ethyl ester provided bis(substituted thienyl)propionic acids in high yields.