Synthesis of bioactive heterocycles: Thermal [3,3] sigmatropic rearrangement of 4-(4 '-aryloxybut-2-ynyloxy)-6-methyl-2-pyrones

Synthesis of a number of hitherto unreported 4-aryloxymethylene-7-methyl-2,3-dihydropyrano[3,2-c]pyran-5-ones (4a-e) have been achieved in moderate yields by the thermal [3,3] sigmatropic rearrangement of 4-(4'-aryloxybut-2'-ynyloxy)-6-methylpyran-2-ones (3a-e).