Rearrangements de dihydro-2,3 benzo-b furannes α vinyliques en milieu acide : acces a des benzo-b furannes et 2h-benzo-b pyrannes

Abstract

Neighbouring alkene group participation, resulting in isomerization, has been studied in reactions of some 2,3 dihydrobenzofurans with hydrobromic acid (in acetic acid) and with paratoluene sulfonic acid (in benzene). It was found that these 2-vinyl cyclic ethers afford benzo-b furans and Δ 3-chromenes ; the ratio of five-to six menbered ring products depending upon the reaction conditions and upon the number of methyl groups at the double bond.