Department of Chemistry, University of Miami, Coral Gables, FL 33143, USA.
Molecules. 2019 Oct 2;24(19):3570. doi: 10.3390/molecules24193570.
Obtaining enantiomerically-enriched photoproducts from achiral reactants has been a long-sought goal. The various methods developed to achieve chiral induction in photoproducts during the last fifty years still suffer from a lack of predictability, generality, and simplicity. With the current emphasis on green chemistry, obtaining enantiomerically enriched products via photochemistry is a likely viable alternative for the future. Of the various approaches developed during the last three decades, the one pioneered in the author's laboratory involved the use of commercially-available and inexpensive achiral zeolites as the media. This approach does not use any solvent for the reaction. Examples from these studies are highlighted in this article. Since no chiral zeolites were available, when the work was initiated in the author's laboratory, commercially-available zeolites X and Y were modified with chiral inductors so that the reaction space becomes chiral. The results obtained established the value of chirally-modified, commercial zeolites as media for achieving chiral induction in photochemical reactions. A recent report of the synthesis of a chiral zeolite is likely to stimulate zeolite-based chiral photochemistry in synthesizing enantiomerically-pure organic molecules. The availability of chiral zeolites in future is likely to energize research in this area. Our earlier observations on this topic, we believe, would be valuable for progress of the field. Keeping this in mind, I have summarized the work carried out in our laboratory on chiral photochemistry on chirally-modified zeolites. This review does not include examples where high chiral induction has been obtained via a strategy that examines molecules appended with chiral auxiliary within achiral and chirally-modified zeolites. The latter approach yields products with diastereomeric excess >80%.
从非手性反应物中获得对映体富集的光产物一直是人们长期追求的目标。在过去五十年中开发的各种方法在光产物中实现手性诱导仍然缺乏可预测性、通用性和简单性。在当前强调绿色化学的情况下，通过光化学获得对映体富集的产物可能是未来的一种可行选择。在过去三十年中开发的各种方法中，作者实验室首创的方法涉及使用商业上可获得的和廉价的非手性沸石作为介质。这种方法不使用任何溶剂进行反应。本文重点介绍了这些研究中的一些例子。由于当时没有手性沸石，当作者实验室开始这项工作时，商用沸石 X 和 Y 用手性诱导剂进行了修饰，以使反应空间具有手性。所得结果确立了手性修饰的商业沸石作为介质在光化学反应中实现手性诱导的价值。最近关于合成手性沸石的报道可能会激发基于沸石的手性光化学在合成对映体纯有机分子中的应用。未来手性沸石的可用性可能会激发该领域的研究。我们相信，我们之前在这个主题上的观察结果对于该领域的进展将是有价值的。考虑到这一点，我总结了我们实验室在手性修饰沸石上进行的手性光化学研究工作。这篇综述不包括通过在非手性和手性修饰沸石中附加手性辅助剂的分子来获得高手性诱导的例子。后一种方法得到的产物具有大于 80%的非对映体过量。
