H. Greiving et al., PHOTOACTIVE CYCLOPHANES .1. SYNTHESIS, PHOTOPHYSICAL AND PHOTOCHEMICAL PROPERTIES OF CINNAMOPHANES, Liebigs Annalen, (11), 1995, pp. 1949-1956
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
.