Photochemical Conversion of 2,6-Dihalo Substituted Methyl a-Phenylcinnamates.

Jón K.F. Geirsson and Ágúst Kvaran

Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavík, Iceland


Photolysis of methyl a-phenylcinnamate derivatives which have both ortho positions of the b-aromatic ring halogenated gives methyl 9-phenanthroates as the only identifiable products in good yields. This photochemical conversion involves a photocyclization with subsequent dehydrohalogenation, and is insensitive to oxygen.  The mechanism of this transformation is briefly discussed: electronic factors seem to govern the outcome of the reaction but steric factors are apparently also of importance.  The ester group attached to the  double bond seems to be essential for the cyclization to take place.