Шаблон:Chembox3-Benzoxepin is an annulated ring system with an aromatic benzene ring and a non-aromatic, unsaturated, oxygen-containing seven-membered heterocyclicoxepin. The first synthesis was described by Karl Dimroth and coworkers in 1961.[1] It is one of the three isomers of the benzoxepins.
Unsubstituted 3-benzoxepin can be synthesized through a double Wittig reaction from o-phthalaldehyde with bis-(α,α′-triphenylphosphonium)-dimethylether-dibromide.[5] The latter compound can be synthesized from α,α′-dibromodimethyl ether (bis(bromomethyl)ether or BBME) which is accessible from hydrobromic acid, paraformaldehyde,[6] and triphenylphosphine. The reaction is performed in dry methanol with sodium methoxide, and the product is obtained in 55% yield.[1][7]
The latter syntheses give 3-benzoxepins in low yields (4–6%).[8]
Properties
3-Benzoxepin is a bright yellow solid that crystallizes in platelets, with a smell similar to naphthalene. The material is soluble in apolar, organic solvents. Like naphthalene, it can be purified through sublimation. The solid is relatively acid-resistant, only under refluxing in concentrated, acidic alcohol solutions an unsaturated aldehyde is formed (likely an indene-3-aldehyde). Catalytic hydrogenation with a palladium catalyst results in 1,2,4,5-tetrahydro-3-benzoxepin.
