Intramolecular Photocycloaddition Of 1,3-Dienes With 2-Pyridones

Intramolecular photocycloaddition of a 2-pyridone and an acyclic 1,3-diene leads to formation of an apparent [2 + 2] product. This is presumably formed by an initial [4 + 4] cycloaddition followed by Cope rearrangement of the highly strained product. The isolated 1,2-divinylcyclobutane undergoes a Cope rearrangement at 120 degrees C to give a polycyclic cyclooctadiene. (C) 1999 Elsevier Science Ltd. All rights reserved.