Photochemical syntheses. X. Photodimers of derivatives of naphthalenecarboxylic acids

Abstract

Photodimers that are derivatives of the ring system (3) have been obtained from six out of 28 mono- and di-substituted naphthalenes examined. The only dimers obtained are head-to-tail isomers that are formed by bonding between the substituted rings of two molecules of the naphthalene derivative. 2-Naphthoic acid anhydride gives the intramolecnlar adduct (3g). The dimers (3h) and (3i) rearrange below 100º to give (4h) and (4i), respectively. Irradiation of methyl 3-methoxy-2-naphthoate in the presence of pyrene gives a mixture of (3i) and (6).