PHOTOACTIVE CYCLOPHANES .1. SYNTHESIS, PHOTOPHYSICAL AND PHOTOCHEMICAL PROPERTIES OF CINNAMOPHANES

In order to transfer the so-called topochemical control established by Schmidt and coworkers to fluid solutions, the [2.2]paracyclophane fra mework was substituted with two acryloyl substituents, one on each of the two decks. The 4 products thus formed are termed cinnamophanes. Th e pseudo-gem derivative, 1, was shown to undergo a very efficient ster eospecific [2 + 2] photocycloaddition to form 5 with the highest quant um yield (approximate to 0.8) ever observed for such a reaction. Where as 2, 3 and 4, the regioisomers of 1, undergo a trans-cis photoisomeri sation, compound 1 leads to the photocycloadduct as the sole photoprod uct. This unusually fast cycloaddition reaction is not sensitive to ox ygen and is largely unaffected by temperature variations. It is believ ed to be a singlet state reaction. The synthesis and a spectroscopic ( absorption and fluorescence emission) study of 1-4 and 5 are described .