Transition‐Metal‐Free Selective Synthesis of (Z)‐1,2‐Diarylthio‐1‐arylalkenes, (2‐Arylethene‐1,1,2‐triyl)tris(arylsulfane)s and Alkynyl Sulfides from Thiocyanates and Terminal Arylalkynes

Abstract

AbstractA transition‐metal‐free strategy using organic thiocyanate as a source of ArS or RS moiety allowed a facile and efficient synthesis of bis(tris)‐vinyl sulfides and alkynyl thioethers under mild conditions. The types of thiocyanates and the choice of bases and solvents had significant effects on the outcomes of the reactions. Aryl thiocyanates reacted with terminal arylalkynes in DMF in the presence of t‐BuOK or MOH (M=Cs, K, Na) at room temperature to form (Z)‐1,2‐diarylthio‐1‐arylalkenes in 24–93% yields, while the same reactions with alkyl thiocyanates provided alkyl alkynyl sulfides in 40–96% yields. Using NaH instead of t‐BuOK or MOH as a base in the similar reactions of aryl thiocyanates and terminal arylalkynes led to the formation of (2‐arylethene‐1,1,2‐triyl)tris(arylsulfane)s in 33–85% yields. Varying the solvent from DMF to THF, the reactions of aryl thiocyanates with terminal arylalkynes at −78 °C to room temperature in the presence of t‐BuOK supplied aryl alkynyl sulfides in 34–96% yields. Aryl and alkyl selenocyanates were also suitable substrates in these reactions. This work is the first time transition‐metal‐free selective construction of (Z)‐1,2‐diarylthio‐1‐arylalkenes, (2‐arylethene‐1,1,2‐triyl)tris(arylsulfane), and alkynyl sulfides from organic thiocyanates and terminal arylalkynes in the presence of a certain base.