| Research Abstract |
In the present study, we first examined the enantiodifferentiating photoisomerizations of prochiral cycloalkenes and cyclopropanes sensitized by several aromatic esters of naturally occurring optically active alcohols to give the optical yields (o.y.) of up to 40%. In order to enhance the product s o.y., we designed a variety of novel chiral sensitizers carrying bulky and/or electron-donating substituents with the aid of molecular mechanics and molecular orbital calculations. These tailored photosensitizers afforded exceptionally high, as enantiodifferentiating photosensitizations, o. y. s. of >50% at room temperature (r. t.) and of up to 70% at -90ﾟC
The above encouraging results prompted us to investigate the more difficult, never tried area of photochemistry : enantiodifferentiating photoaddition reactions. Thus, the enantiodifferentiating anti-Markovnikov methanol addition to 1,1-diphenylpropene sensitized by chiral naphthalene(di) carboxylates gave the o. y. s up to 27% even at r. t.
The present work clearly indicates that the photosensitized enantiodifferentiating uni- and bimolecular reactions, demanding only a catalytic amount of chiral sensitizer, are not only of theoretical interest but also of practical importance in the asymmetric synthesis.
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