Molecular Design of New Optically Active Sensitizers for Highly Efficient Photosensitized Asymmetric Reactions

在本研究中，我们首先研究了几种天然存在的光学活性醇的芳香酯敏化的前手性环烯烃和环丙烷的对映异构化，得到了光学产率（o.y.）高达40%。为了提高产品的舒适度，借助于分子力学和分子轨道计算，我们设计了多种携带大体积和/或供电子取代基的新型手性敏化剂。这些定制的光敏剂提供了非常高的，作为对映体分化的光敏化，o。y. S.在室温下的>50%（R. t.）上述令人鼓舞的结果促使我们研究更困难的，从未尝试过的光化学领域：对映体分化光加成反应。因此，手性萘（二）羧酸酯敏化的1，1-二苯基丙烯与甲醇的反马氏加成反应得到了O. y.即使在r下，s也高达27%。目前的工作清楚地表明，光敏对映体分化的单分子和双分子反应，只需要催化量的手性敏化剂，不仅是理论上的兴趣，而且在不对称合成的实际意义。

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CThe 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.