Carbon Dioxide-Catalyzed Stereoselective Cyanation Reaction

© 2019 American Chemical Society.We report a Michael-type cyanation reaction of coumarins by using CO2 as a catalyst. The delivery of the nucleophilic cyanide was realized by catalytic amounts of CO2, which forms cyanoformate and bicarbonate in the presence of water. Under ambient conditions, CO2-catalyzed reactions afforded high chemo- A nd diastereoselectivity of β-nitrile carbonyls, whereas only low reactivities were observed under argon or N2. Computational and experimental data suggest the catalytic role of CO2, which functions as a Lewis acid, and a protecting group to mask the reactivity of the product, suppressing byproducts and polymerization. The utility of this convenient method was demonstrated by preparing biologically relevant heterocyclic compounds with ease11sciescopu

¹H and ¹³C NMR Assignment of Sunitinib Malate in Aqueous Media

Despite expanding therapeutic application of sunitinib and advances in its formulation, pharmacochemical and spectroscopical study on its aqueous solution is rather insufficient due to poor solubility of its base or salt form. In this report, ¹H (900 MHz) and ¹³C (225 MHz) NMR spectra of sunitinib malate in H₂O/D₂O=9/1 have been analyzed, whose spectral peaks have been assigned to each hydrogen and carbon atom, assisted by a combination of two-dimensional homo- and heteronuclear NMR: COSY, HSQC-DEPT, and HMBC. The assignment of labile H-N hydrogens in ¹H NMR spectrum is of particular interest in aqueous media, where such labile hydrogens could be potentially affected by intermolecular interactions (e.g., hydrogen bonding) with co-solvated constituents. Peak splitting patterns and corresponding ⁿJ(H-H), ⁿJ(H-F), and ⁿJ(C-F) coupling constants observed in each assigned spectrum have been jointly discussed, and ⁿJ(C-F) coupling constants were compared to those taken in DMSO-d6

(+)-Dimericbiscognienyne A: Total Synthesis and Mechanistic Investigations of the Key Heterodimerization

The first total synthesis of (+)-dimericbiscognienyne A is described. Key to the successful access to (+)-dimericbiscognienyne A was a biosynthetically inspired Diels-Alder reaction between two differential epoxyquinoid monomers and the subsequent intramolecular hemiacetal formation. The selective formation of the natural product among other possible diastereomers during the late-stage [4+2] cycloaddition reaction was investigated by DFT calculations and experimental control studies. Copyright (c) 2018 American Chemical Societ

Unexpected Selectivity of Intramolecular [3+2] Cycloaddition of Trimethylenemethane (TMM) Diyl toward Total Synthesis of Conidiogenone B

In the course of a study toward a total synthesis of conidiogenone B through TMM diyl-mediated tandem cycloaddition reaction, unexpected regioselectivity for a bridged isomer was observed. The synthetic and computational studies with model compounds revealed that regioselectivity can be rendered by changing substitution patterns on the TMM diyl moiety and the olefin moiety by altering the activation energy of cycloaddition reaction through a singlet TMM diyl pathway © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinhei

Aldehyde Carboxylation: A Concise DFT Mechanistic Study and a Hypothetical Role of CO (2) in the Origin of Life

Carbon dioxide is arguably one of the most stable carbon-based molecules, yet enzymatic carbon fixation processes enabled the sustainable life cycle on Earth. Chemical reactions involving CO (2) -functionalization often suffer from low efficiency with highly reactive substrates. We recently reported mild carboxylation of aldehydes to furnish -keto acids - a building block for chiral -amino acids via reductive amination. Here, we discuss potential reaction mechanisms of aldehyde carboxylation reactions based on two promoters: NHCs and KCN in the carboxylation reaction. New DFT mechanistic studies suggested a lower reaction barrier for a CO (2) -functionalization step, implying a potential role of CO (2) in prebiotic evolution of organic molecules in the primordial soup. 1 Introduction: Aldehydes, Benzoins, Carboxylic Acids 2 CO (2) -Activation: NHC, Cyanide, Lewis Acid and Water 3 A Breslow Intermediate: Benzoin Reaction vs. Carboxylation with CO (2) 4 Carboxylation in the Primordial Soup 5 Conclusio © Georg Thieme Verlag Stuttgart · New Yor