3-Benzoxepin
Chemical compound
From Wikipedia, the free encyclopedia
3-Benzoxepin is an annulated ring system with an aromatic benzene ring and a non-aromatic, unsaturated, oxygen-containing seven-membered heterocyclic oxepin. The first synthesis was described by Karl Dimroth and coworkers in 1961.[1] It is one of the three isomers of the benzoxepins.
 | |
| Names | |
|---|---|
| Preferred IUPAC name
3-Benzoxepine | |
| Identifiers | |
3D model (JSmol) |
|
| ChemSpider | |
PubChem CID |
|
CompTox Dashboard (EPA) |
|
| |
| |
| Properties | |
| C10H8O | |
| Molar mass | 144.173 g·mol−1 |
| Appearance | Yellow solid[1] |
| Melting point | 84 (83–84 °C;[2] 84 °C[1]) |
| Solubility | soluble in apolar solvents (diethyl ether, benzene, tetrachloromethane)[3] and alcohols (methanol)[2] |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
| |
Occurrence and synthesis
3-Benzoxepin itself is a non-natural compound, but the bicyclic ring system is part of the naturally occurring compounds perilloxin (I) from Perilla frutescens (variant acuta),[4] tenual (II), and tenucarb (III) from Asphodeline tenuior.[5] Perilloxin inhibits the enzyme cyclooxygenase with an IC50 of 23.2 μM.[4] Non-steroidal anti-inflammatory drugs like aspirin and ibuprofen also work by inhibiting the cyclooxygenase enzyme family.[6]
Structural formulas of perilloxin, tenual, and tenucarb
Unsubstituted 3-benzoxepin can be synthesized through a double Wittig reaction from o-phthalaldehyde with bis-(α,α′-triphenylphosphonium)-dimethylether-dibromide.[2] The latter compound can be synthesized from α,α′-dibromodimethyl ether (bis(bromomethyl)ether or BBME) which is accessible from hydrobromic acid, paraformaldehyde,[7] and triphenylphosphine. The reaction is performed in dry methanol with sodium methoxide, and the product is obtained in 55% yield.[1][3]
Synthesis from 3-benzoxepin according to K. Dimroth
The compound can also be obtained through UV-irradiation of certain naphthalene derivatives such as 1,4-epoxy-1,4-dihydronaphthalene.[8]
3-Benzoxepin from UV-irradiation from epoxydihydronaphthaline
It can also be obtained by photooxygenation of 1,4-dihydronaphthalene, followed by pyrolysis of the formed hydroperoxides.[9]
3-Benzoxepin durch Pyrolyse aus Hydroperoxydihydronaphthalen
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.
Reactions with 3-Benzoxepin
