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] and tenual (II) and tenucarb (III) from Asphodeline tenuior.

[4] Non-steroidal anti-inflammatory drugs like aspirin and ibuprofen also work by inhibiting the cyclooxygenase enzyme family.

[6] Unsubstituted 3-benzoxepin can be synthesized through a double Wittig reaction from o-phthalaldehyde with bis-(α,α′-triphenylphosphonium)-dimethylether-dibromide.

The reaction is performed in dry methanol with sodium methoxide, and the product is obtained in 55% yield.

The solid is relatively acid-resistant, only under refluxing in concentrated, acidic alcohol solutions an unsaturated aldehyde is formed (likely an indene-3-aldehyde).