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

Abstract

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.

Hierarchically Porous Sphere-Like Copper Oxide (HS-CuO) Nanocatalyzed Synthesis of Benzofuran Isomers with Anomalous Selectivity and Their Ideal Green Chemistry Metrics

“…As a result, enormous synthetic strategies and methodologies have been developed for the construction of benzo­[b]­furan scaffolds such as decarboxylation of o-acylphenoxyacetic acids or esters, − dehydrative cyclization of (α-(phenoxy)-alkyl ketones, , palladium catalyzed cyclization of 2-(1-alkynyl)­phenols, , [3,3]-sigmatropic rearrangement of arenes etc . Recently, A3 coupling strategy, is a three-component coupling of an aldehyde, an alkyne and an amine, has been considered to be a sustainable tool with high atom economy to afford N-heterocyclic natural products and O-heterocycles including 2,3-disubstituted benzo­[b]­furans. − However, most of the reported catalytic conditions generate excess waste along with desired product due to the usage of extra additives and base reagents, toxic organic solvents and nonrecyclable catalysts which limit their applications at industrial scale production.…”