REARRANGEMENTS DE DIHYDRO-2,3 BENZO-b FURANNES α VINYLIQUES EN MILIEU ACIDE: ACCES A DES BENZO-b FURANNES ET 2H-BENZO-b PYRANNES

Article abstract of DOI:10.1016/S0040-4020(01)85988-3

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 membered ring products depending upon the rection conditions and upon the number of methyl groups at the double bond.