One-Pot Synthesis of Unsymmetrical 1,3-Butadiyne Derivatives and their Application in the Synthesis of Unsymmetrical 2,5- Diarylthiophenes

摘要

A one-pot protocol was developed for the synthesis of unsymmetrical 1,3-butadiynes. The procedure is based on two sequential reactions: deprotection of R-C≡C-C≡C- C(Me)_2OH derivatives in a retro-Favorskii reaction to furnish a terminal 1,3-butadiyne compound, which reacted with aryl iodides in a Sonogashira-type cross-coupling reaction catalyzed by Pd(PPh_3)_4 and CuI, using TBAOH as activator and toluene as solvent under reflux for 10 min. We also studied in situ thiocyclization of 1,3-butadiynes, leading to unsymmetrical 2,5-diarylthiophenes. The principal features of this method are operational simplicity, good substrate scope, very fast reaction, and high yields.