Photochemical reactions of P-mentha-13,8-triene and structural related P-menthadienes

Article abstract of DOI:10.1016/S0040-4020(01)96033-8

The photochemical and thermal behaviour of cyclic olefins like p-mentha-1,3,8-triene (2) and structural related p-mentha-1,3- and -1,4-dienes under the influence of oxygen have been investigated. Dehydration, ring opening, (4+2)-cycloaddition of singlet oxygen¹ and dimerization were observed as concurring mechanisms. The photochemical and thermal dehydrogenation of α-terpinene (1), α-phellandrene (3), γ-terpinene (4) and p-mentha-1,3,8-triene (2) leads to p-cymene (5) and p-cymenene (6), respectively. The mechanism of this aromatization reaction will be discussed in this paper.