Regioselective Synthesis of 3-(aryloxyacetyl)-2,3-dihydrothieno[3,2-c][1] benzothiopyran-4-ones: A Tandem [2,3] and [3,3]sigmatropic Rearrangement Approach

Hitherto unreported 3-(aryloxyacetyl)-2,3-dihydrothieno[3,2-c][1]benzothiopyran-4-ones (4a-f) were synthesized in excellent yield by the application of the tandem [2,3] and [3,3] sigmatropic rearrangements of the 4-(4' -aryloxybut-2'-ynylthio)[1]benzothiopyran-2-ones (3a-f). The substrates (3a-f) were synthesized by phase transfer catalyzed alkylation of previously unreported 4-mercaptothiopyran-2-ones with different 1-aryloxy-4-chlorobut-2-ynes.