Studies of bioactive heterocycles: facile thio-Claisen rearrangement of propargylthio[1]benzopyran-2-ones

Hitherto unreported 2H-thiopyrano[3,2-c][1]benzopyran-5-ones 6a–f are synthesized regioselectively in 79–85% yields by the thio-Claisen rearrangement of 4-propargylthio[1]benzopyran-2-ones 5a–f. The substrates 5a–f are synthesized by alkylation of hitherto unreported 4-mercaptocoumarins.