Magnesium chloride (MgCl2) catalyzed highly regioselective C-3 ring opening of 2,3 epoxy alcohols by N-nucleophile

Catalytic Asymmetric Synthesis of β-Amino α-Tertiary Alcohol through Borrowing Hydrogen Amination

The first enantioconvergent transition-metal-catalyzed amination of racemic α-tertiary 1,2-diols providing access to vicinal β-amino α-tertiary alcohols is disclosed. The iridium-catalyzed amination reaction proceeds through a chiral phosphoric acid-mediated borrowing hydrogen pathway with excellent yields and enantioselectivities for a range of amine nucleophiles and α-tertiary 1,2-diols. An array of β-amino α-tertiary alcohols were obtained with high yields and enantioselectivities (50 examples with up to 91% yield and up to 99% ee). These important chiral amino alcohol products can be easily converted into chiral ligands and bioactive skeletons. Mechanistic investigations proposed a dynamic kinetic resolution pathway involving imine formation and then imine reduction as the enantiodetermining step.

Quantifying the Epoxide Group and Epoxide Index in Graphene Oxide by Catalyst-Assisted Acid Titration

Graphene oxide (GO), having diverse oxygen functional groups, including carboxyl, hydroxyl, carbonyl, and epoxy groups, is a significant graphene-related 2D material (GR2M) essential for various applications. The quantification of these functional groups traditionally utilizes Boehm acid titration, which, however, does not account for epoxy groups crucial for these applications. Presently, there exists no analytical method enabling quantitative assessment of the concentration of epoxy groups in GO available in the market in different forms such as powders, pastes, and dispersions. This paper presents a new approach employing catalyst-assisted acid-water-based titration to quantify epoxy groups in GO materials. The method's efficacy was validated using a well-characterized reference GO sample and tested on commercially produced GO powders, yielding epoxy group concentrations ranging from 1.15 ± 0.047 to 1.37 ± 0.051 mmol/g with high precision and reproducibility. The method introduces two new quality parameters, including the epoxide index (EI) and the equivalent epoxide weight (EEW) not implemented for GO before. Control measurements with a commercial epoxide material of known epoxide content demonstrated excellent agreement by using the proposed approach. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used for comparative characterizations of epoxide groups in GO samples during titrations.

Synthesis and medicinal chemical characterisation of antiproliferative O,N-functionalised isopulegol derivatives

Benzylation of isopulegol furnished O-benzyl-protected isopulegol, which was transformed into aminodiols via epoxidation followed by ring opening of the corresponding epoxides and subsequent hydrogenolysis. On the other hand, (-)-isopulegol was oxidised to a diol, which was then converted into dibenzyl-protected diol derivatives. The products were then transformed into aminotriols by using a similar method. The antiproliferative activity of aminodiol and aminotriol derivatives was examined. In addition, structure-activity relationships were also explored from the aspects of substituent effects and stereochemistry on the aminodiol and aminotriol systems. The drug-likeness of the compounds was assessed by in silico and experimental physicochemical characterisations, completed by kinetic aqueous solubility and in vitro intestinal-specific parallel artificial membrane permeability assay (PAMPA-GI) measurements.

A Tandem Semipinacol Rearrangement/Aldehyde Arylation or Alkylation of Trisubstituted 2,3-Epoxy Alcohols with Grignard Reagents for Functionalized 1,3-Diols

A tandem semipinacol rearrangement/aldehyde arylation or alkylation reaction leading to formation of functionalized 1,3-diols bearing three consecutive tertiary stereocenters is identified from the reaction of various new trisubstituted 2,3-epoxy alcohols with numerous Grignard reagents. This reaction is useful for stereoselective construction of three consecutive tertiary stereocenters. The observed 1,3-diols exist in the anti configuration, which is confirmed by two-dimensional nuclear Overhauser effect spectroscopy, the crystal structure of acetonide of 1,3-diol analogue 3ai, and further density functional theory studies.

Transition metal-free, base mediated one-pot approach for the construction of the benzo[b][1,4,5]oxathiazepine 1-oxide core

Protocol for synthesising selected separable diastereomers of benzo[b][1,4,5]oxathiazepine 1-oxides via intermolecular epoxide ring opening by o-halogenated NH-sulfoximine followed by cyclisation and configurations were assigned by 2D NMR and X-ray crystallography.