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Stereoselective synthesis of heterocycles from the opening of chiral epoxides or azidirines

Grant number: 18/23761-0
Support type:Scholarships in Brazil - Doctorate
Effective date (Start): October 01, 2019
Effective date (End): July 31, 2023
Field of knowledge:Physical Sciences and Mathematics - Chemistry
Principal Investigator:Arlene Gonçalves Corrêa
Grantee:Lorena Suelen Ribeiro Martelli
Home Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
Associated research grant:14/50249-8 - Green chemistry: sustainable synthetic methods employing benign solvents, safer reagents, and bio-renewable feedstock, AP.PCPE

Abstract

The formation of aziridines in alfa, beta-unsaturated ketones using organocatalysts is still a challenge. There are few efficient methods described in the literature, with only moderate enantiomeric excesses and mostly using toxic solvents. Epoxides and aziridines are important building blocks because, since they have high ring tension, they can be easily opened in the presence of different nucleophiles. This opening occurs diastereoselectively and, depending on the reaction conditions, it's possible to obtain the product with anti or syn relative configuration. Among the numerous methodologies of functionalization of epoxides, the opening promoted photochemically through radical reaction stands out. Although there are reports of functionalization of epoxides and aziridines via photochemical processes, the use of photo-organocatalysts has not yet been explored in these substrates, since it presents difficulties in the choice of an ideal fossensibilizer. Particularly, the photocatalyzed reactions have received great attention in the last years, because it has emerged as an efficient and sustainable alternative in the development of new methodologies and in the obtaining of interesting compounds. In the search for even more effective conditions, the synthesis using continuous flow method offers the opportunity to accelerate chemical transformations, maximize the products results and automate syntheses. In addition, this method has advantages such as greater safety, efficiency in heat transfer and good control of reaction variations such as temperature and residence time. The photochemical reactions in continuous flow have been studied recently, because the irradiation of light through the microtubes is more efficient than in reactional flasks. Thus, this project has the porpose of studying the ring opening of epoxides/aziridines aiming the formation of 5- and 6-membered heterocyclic rings via photochemical reactions in a continuous flow, then the synthesized products will be submitted to inhibition tests of cysteine proteases, such as cathepsins D and L. (AU)