Synthesis,Structure and Photoreactivity of Several Cinnamophane Vinylogs

摘要

In preceding papers,cinnamophanes 1a-d (two cinnamic ester units locked in a [2.2]paracyclophane skeleton) were described.In particular,the pseudo-gem isomer la was shown to produce in solution an intramolecular cyclobutane photo-cycloadduct with stereospecificity and very high efficiency,following the topochemical rule observed in the solid state.Here are reported the synthesis and X-ray structure determination of their vinylogs 5a-d.The photoreactivity of the pseudo-gem isomer 5a was especially investigated in order to examine whether the same specificity would be maintained for the longer dienic substituents.It was found that,depending on the irradiation wavelengths,different bicyclic (8) and tetracyclic (9 and 10) intramolecular photocycload-ducts (ladderanes) were produced,but with reduced efficiency as compared to that of la.The pseudo-ortho- and pseudo-para isomers 5b and 5d form the oxetenes 11 and 12,respectively,on irradiation.