Competitive Carbothiolation and Sonogashira Cross‐Coupling in the Reaction of Trimethylsilylacetylene with Arylthioacetates

• Published in: ChemistrySelect (Weinheim) 2016-10, Vol.1 (16), p.5201-5205
• Main Authors: Iovine, Valentina, Cruciani, Federico, Picini, Flavio, Varrone, Marta, Rossi, Enrico, Bassetti, Mauro, D'Annibale, Andrea
• Format: Article
• Language: English
• Subjects: acetylthiolation; alkyne carbothiolation; arylthioesters; bimetallic catalysis; Sonogashira cross-coupling
• ISSN: 2365-6549; 2365-6549
• DOI: 10.1002/slct.201601373

p‐Bromo‐ or p‐iodophenylthioacetate can react with trimethylsilylacetylene by simultaneous Sonogashira coupling at the halide function and addition of acetyl and arylthio moieties to the triple bond. Reaction of arylthioacetates with p‐OMe, ‐Me, Ph and ‐Cl substituents, under the typical conditions of the Sonogashira coupling, leads only to the regio‐ and stereoselective acetylthiolation of trimethylsilylacetylene affording β‐silylated‐β‐arylthio‐α,β‐unsaturated ketones. The carbothiolation of PhSAc is faster than the Sonogashira coupling of Ph−Br and slower than that of Ph−I, implying that the rates of oxidative addition to Pd(0) are in the order (X=I > SAc >Br). p‐Bromo‐ or p‐iodophenylthioacetate react with trimethylsilylacetylene under Pd/Cu catalysis by simultaneous Sonogashira coupling at the halide function and acetylarylthiolation of the triple bond. This latter reaction proves to occur also on other substituted arylthioacetates, affording regio‐ and stereoselectively the corresponding β‐silylated‐β‐arylthio‐α,β‐unsaturated ketones.