PHOTOCHEMICAL REACTIONS OF AROMATIC ESTERS .I. PHOTOCHEMICAL SYNTHESIS OF NEW OXETANES FROM AROMATIC ESTERS WITH 1,1-DIPHENYLETHYLENE

Irradiation of dimethyl terephthalate IIIa with 1,1-diphenylethylene IV afforded an oxetane Va as a sole adduct. The structure of the oxetane was established on the basis of its spectroscopic properties. Similar irradiation of p- or o-cyanobenzoate with IV gave a corresponding oxetane Vb or Vc, respectively. Trimethyl trimesate VII could also add to IV photochemically to form an oxetane VIII. On the other hand, irradiation of dimethyl phthalate IIId with IV could not give an oxetane Vd but an olefin VI which was considered to be produced through the elimination of a formaldehyde molecule from an unstable intermediate oxetane Vd. A reactive species of the photocycloaddition was suggested to be an n-π* triplet state of the aromatic ester from the evidences of the phosphorescence emissions of the esters and the direction of the addition. © 1969.