Studies on sulfoxide rearrangements: regioselective synthesis of 3-(aryloxyacetyl)-2,3-dihydrothieno[3,2-c][1]benzopyran-4-ones

Hitherto unreported 3-(aryloxyacetyl)-2,3-dihydrothieno[3,2-c][1] benzopyran-4-ones 5a–f were synthesised in 70–75% yields by the application of the sulfoxide rearrangement of 4-(4-aryloxybut-2-ynylthio)[1]benzopyran-2-ones 4a–f. The substrates 4a–f were synthesised by phase-transfer-catalysed alkylation of previously unreported 4-mercaptocoumarin.