Synthesis And Reactivity Of Alpha-Sulfenyl-Beta-Chloroenones, Including Oxidation And Stille Cross-Coupling To Form Chalcone Derivatives

The synthesis of a range of novel alpha-sulfenyl-beta-chloroenones from the corresponding a-sulfenylketones, via a NCS mediated chlorination cascade, is described. The scope of the reaction has been investigated and compounds bearing alkyl- and arylthio substituents have been synthesised. In most instances, the Z alpha-sulfenyl-beta-chloroenones were formed as the major products, while variation of the substituent at the beta-carbon position led to an alteration in stereoselectivity. Stille cross-coupling with the Z alpha-sulfenyl-beta-chloroenones led to selective formation of Z sulfenyl chalcones, while the E alpha-sulfenyl-beta-chloroenones did not react under the same conditions. Oxidation of the Z alpha-sulfenyl-beta-chloroenones was followed by isomerisation, leading to the E alpha-sulfinyl-beta-chloroenones. Stille cross-coupling with the E alpha-sulfinyl-beta-chloroenones produced the E sulfinyl chalcones. Either the E or Z sulfinyl chalcones can be obtained by altering the sequence of oxidation and Stille cross-coupling. (C) 2021 The Author(s). Published by Elsevier Ltd.