Intramolecular [2+2] photocycloaddition of bichromophoric derivatives of 3,5-dihydroxybenzoic acid and 3,5-dihydroxybenzonitrile

摘要

The irradiation of 3-alkenyloxy-5-hydroxybenzoic acid derivatives 1a-d yields highly functionalized alkyloxyenone derivatives when the reaction is carried out in the presence of acid. A higher reactivity is observed for the corresponding 3-alkenyloxy-5-hydroxybenzonitrile compounds 7a, b, which also react in neutral reaction media. In the first step of the reaction, a [2+2] photocy cloaddition occurs. The following steps, leading to stable final prod ucts, need acid catalysis in the case of the substrates 1a-d. The irradiation of the benzonitrile derivative 7b also furnishes the side product 9, which results from a [2+3] photocycloaddition. [References: 93]