Regioselective Synthesis of Thieno[3,2-<Emphasis Type="Italic">c</Emphasis>][1]benzopyran-4-ones by Thio-<Emphasis Type="Italic">Claisen</Emphasis> Rearrangement

Summary. A number of thieno3,2-c]1]benzopyran-4-ones, potential antiinflamatory, antipyretic, and antiallergic drugs, are synthesized in 65–80% yield by thermal thio-Claisen rearrangement of 4-allylthio1]benzopyran-2-ones in refluxing quinoline for 0.5–8.0h. The 4-allylthio1]benzopyran-2-ones are in turn prepared in 75–85% yield from 4-mercaptocoumarin and different allylic halides by phase-transfer-catalysed alkylation with TBAB or BTEAC catalyst in chloroform-aq. NaOH at room temperature.