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]photocycloaddition occurs.The following steps,leading to stable final products,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.