Furan Derivatives. VII. Synthesis of Cyclohepta[<i>cd</i>]benzofurans

Cyclohepta[cd]benzofurans 1a‐c were synthesized by heating (5‐oxo‐5H‐benzocyclohepten‐4‐yloxy)acetic acids 7a‐c with sodium acetate in acetic anhydride or by irradiation of 7a‐c in acetonitrile. Several reactions such as protonation, catalytic hydrogenation, Diels‐Alder reaction, acylation, and photoreaction were examined for 1a‐b. The results show that cyclohepta[cd]benzofurans have both properties of heptafulvene and benzofuran. The carbon‐carbon double bond in the furan ring of 1a has aromatic character, however, the carbon‐carbon double bonds in the seven‐membered ring have olefinic character.

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Synthesis and properties of furo[4,3,2‐de][1]benzopyran

Toko

Suzuki

Horaguchi

et al. 1991

Journal of Heterocyclic Chem

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A new heterocycle, furo[4,3,2‐de][1]benzopyran (2), was synthesized. A key step in the sequence was the allylic bromination of 3,4‐dihydrofuro[4,3,2‐de][1]benzopyran (8) to give 3‐bromo‐3,4‐dihydrofuro[4,3,2‐de][1]‐benzopyran (10) using N‐bromosuccinimide under irradiation and high dilution conditions. Bromide 10 was dealt with 1,8‐diazabicyclo[5.4.0]undec‐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.

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Furan Derivatives. VII. Synthesis of Cyclohepta[cd]benzofurans

Abstract: 7-Methoxy-3,4-dihydrocyclohepta[cd]benzofuran and 7-methoxycyclohepta[cd]benzofuran were synthesized.

Cited by 3 publications

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ChemInform Abstract: FURAN DERIVATIVES. VII. SYNTHESIS OF CYCLOHEPTA(CD)BENZOFURANS

ChemInform Abstract: FURAN DERIVATIVES. VII. SYNTHESIS OF CYCLOHEPTA(CD)BENZOFURANS

Furan derivatives. Part 9. Synthesis and properties of cyclohepta[cd]benzofurans

Synthesis and properties of furo[4,3,2‐de][1]benzopyran

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