A useful modification of the Garst-Spencer furan annulation: An improved synthesis of 3,4-substituted furans

Article abstract of DOI:10.1016/S0040-4039(98)02017-6

The reaction of keto thioenol ether 6 with dimethylsulfonium methylide gives the isolable epoxide 7, which smoothly rearranges under thermal conditions to yield the five-membered thioacetal 8. Subsequent desulfurization/aromatization with a catalytic amount of iodine furnishes the desired furan 5 in greater than 70% overall yield.