Abstract
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%.
Highlights
The origin and continued existence of life on earth depends on light absorption by molecules [1].The science of light, especially in the context of organic chemistry, has a history exceeding a century.Several photochemical reactions employed today were discovered in the early 1900’s [2]
The confinement provided by the zeolite medium and the weak interaction between the charge-compensating cations and the guest forces an interaction between the achiral reactant and the chiral inductor
We have d chiral induction in a variety of photoreactions of achiral molecules within achiral zeolites with the help of chiral inductors
Summary
The origin and continued existence of life on earth depends on light absorption by molecules [1]. In conjunction with discoveries of new photoreactions, the development of theoretical and physical concepts related to triplet state, radiative and radiationless transitions, and energy- and electron transfer have contributed to the vigorous growth of the field of organic photochemistry [1]. These concepts, verified by several pioneering studies from 1960–1990 with time resolved techniques, have placed the field of photochemistry on a firm footing and have allowed it to permeate other disciplines of chemistry. The monograph on asymmetric photochemistry in various media by Inoue and Ramamurthy provides detailed coverage of this topic [24]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
