Scandium-Catalyzed Propargylation of 1,3-Diketones with Propargyl Alcohols Bearing Sulfur or Selenium Functional Groups: Useful Transformation to Furans and Pyrans

Abstract

Propargylations of 1,3-diketones using 3-sulfanyl and 3-selanylpropargyl alcohols 1 in MeNO₂–H₂O gave alkynyl ketones 2a—m, 2o—v and 6,7-dihydro-5H-cyclohexa[b]pyran-5-ones 3k—n. With some bases, the useful propargylated 1,3-diketones underwent intramolecular cyclization to give 6,7-dihydro-5H-benzofuran-4-ones 4a—i or 4,5,6,7-tetrahydrobenzofurans 5p, 6p—v.