UV irradiation of the ride compound produces cis-1,2-diphenylbenzocycl
obutenol quantitatively. While stable at temperatures below 0 degrees
at room temperature it establishes a high enough equilibrium populatio
n of its EE o-xylylenol precursor to undergo slow reversion to ketone
and rapid reaction with maleic anhydride or oxygen, as well as photoin
duced cyclization to the trans cyclobutenol. (C) 1998 Elsevier Science
Ltd. All rights reserved.