Synthesis of Thioalkynes by Desilylative Sonogashira Cross-Coupling of Aryl Iodides and 1-Methylthio-2-(trimethylsilyl)ethyne

1-Methylthio-2-arylethynes were prepared in typically good to excellent yields from aryl iodides and 1-methylthio-2-(trimethylsilyl)ethyne by a desilylative Sonogashira process employing Pd(PPh3)(2)Cl-2 (1 mol %), CuI (10 mol %), and K2CO3 (6 eq) in MeOH-Et3N-THF (1 : 2 : 2) at rt for 16 h (16 examples, 31-96 % yield). Thienyl and pyridyl iodides (all regioisomers) were similarly converted to 1-methylthio-2-heteroarylethynes (5 examples, 54-82 % yield). The process was extended with similar results to comparable thioalkynes substituted on sulfur by n-alkyl, s-alkyl, and aryl groups.

Automated summary

In this study, a desilylative Sonogashira process was employed to prepare 1-methylthio-2-arylethynes and 1-methylthio-2-heteroarylethynes from aryl iodides and 1-methylthio-2-(trimethylsilyl)ethyne. The reaction conditions were optimized to achieve high yields, and the method was also applicable for thioalkynes substituted on sulfur.