209-08-5

A new heterocycle, furobenzopyran (2) was synthesized.A key step in the sequence was the allylic bromination of 3,4-dihydrofurobenzopyran (8) to give 3-bromo-3,4-dihydrofurobenzopyran (10) using N-bromosuccinimide under irradiation and high dilution conditions.Bromide 10 was dealt with 1,8-diazabicycloundec-7-ene to afford compound 2.Several reactions of 2 were examined.Protonation of 2 in trifluoroacetic acid occurred at the 2-position to form a pyrylium ion 12.Catalytic hydrogenation of 2 with palladium on charcoal proceeded smoothly to give 8.Reduction of 2 by sodium and ethanol afforded 3-ethyl-4-hydroxybenzofuran (14).Electrophilic substitutions of 2 such as formylation, acetylation, and bromination, occurred easily at the 2-position.The above results show that compound 2 has both properties of benzofuran and 4-methylenepyran.