Catalytic asymmetric synthesis of alfa,alfa-disubstituted alfa-thio- and alfa-amino acid derivatives

449 p

Molecular-Level Insight into Charge Carrier Transport and Speciation in Solid Polymer Electrolytes by Chemically Tuning Both Polymer and Lithium Salt

The advent of Li-metal batteries has seen progress toward studies focused on the chemical modification of solid polymer electrolytes, involving tuning either polymer or Li salt properties to enhance the overall cell performance. This study encompasses chemically modifying simultaneously both polymer matrix and lithium salt by assessing ion coordination environments, ion transport mechanisms, and molecular speciation. First, commercially used lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt is taken as a reference, where F atoms become partially substituted by one or two H atoms in the −CF3 moieties of LiTFSI. These substitutions lead to the formation of lithium(difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide (LiDFTFSI) and lithium bis(difluoromethanesulfonyl)imide (LiDFSI) salts. Both lithium salts promote anion immobilization and increase the lithium transference number. Second, we show that exchanging archetypal poly(ethylene oxide) (PEO) with poly(ε-caprolactone) (PCL) significantly changes charge carrier speciation. Studying the ionic structures of these polymer/Li salt combinations (LiTFSI, LiDFTFSI or LiDFSI with PEO or PCL) by combining molecular dynamics simulations and a range of experimental techniques, we provide atomistic insights to understand the solvation structure and synergistic effects that impact macroscopic properties, such as Li+ conductivity and transference number.The authors acknowledge support from the European Commission grant for Erasmus Mundus Joint Master’s Degree MESC+ under Framework Agreement Number 2018-1424/001-001-EMJMD, the EU Marie Sklodowska-Curie COFUND DESTINY project under Grant Agreement No. 945357, and the Basque Government PhD Grant. H.M. acknowledges funding from the “Departamento de Educación, Política Lingüística y Cultura del Gobierno Vasco” (Grant IT1358-22). They also thank SGI/IZO-SGIker UPV/EHU for supercomputing resources

Catalytic asymmetric synthesis of alfa,alfa-disubstituted alfa-thio- and alfa-amino acid derivatives

449 p

Catalytic Enantioselective Synthesis of Tertiary Thiols From 5H-Thiazol-4-ones and Nitroolefins: Bifunctional Ureidopeptide-Based Brønsted Base Catalysis

The direct catalytic reaction between an enolizable carbonyl compound and an electrophile under proton-transfer conditions has emerged as a challenging versatile transformation in organic synthesis.1 Over the last years several chiral Brønsted bases have been developed to promote this transformation diastereo- and enantioselectively.2 However, successful examples are mostly limited to 1,3-dicarbonyl compounds and acidic carbon analogues as the pronucleophilic reaction partners. 5H-Thiazol-4-ones, in contrast, have been well known for a long time and have found several applications in pharmaceutical and medicinal chemistry.3 Although structurally related to 5H-oxazol-4-ones4 and 4H-oxazol-5-ones (azlactones),5 5H-thiazol-4-ones have, as far as we know, been never been used in asymmetric synthesis in spite of the fact that they may be easily deprotonated6 and in spite of the importance of thiols and organosulfur compounds in organic synthesis7 and chemical biology.8 In this context, whilst chiral secondary thiol derivatives have been the subject of most investigations, tertiary thiols have remained mostly unexplored owing to the insufficient catalytic enantioselective methodology for their preparation in optically pure form.