Enantioselective reduction of ketoxime ethers with borane–oxazaborolidines and synthesis of the key intermediate leading to (S)-rivastigmine

Sustainable chemo-enzymatic preparation of enantiopure (R)-β-hydroxy-1,2,3-triazoles via lactic acid bacteria-mediated bioreduction of aromatic ketones and a heterogeneous “click” cycloaddition reaction in deep eutectic solvents

A chemo-enzymatic strategy for the preparation of enantiopure (R)-β-hydroxy-1,2,3-triazoles using a lactic acid bacterium as a whole-cell biocatalyst and a heterogeneous “click” cycloaddition reaction in deep eutectic solvents is disclosed.

Dual Roles of tert-Butyl Nitrite in the Transition Metal- and External Oxidant-Free Trifluoromethyloximation of Alkenes

By employing tert-butyl nitrite as both nitrogen source and oxidant, the trifluoromethyloximation of alkenes proceeds smoothly in a free-radical process. The developed difunctionalization reaction enables practical and efficient synthesis of a wide range of α-CF₃ ketoximes in moderate yields with excellent regioselectivity. This method features the use of readily available and stable alkenes as substrates and inexpensive CF₃ SO₂ Na as a CF₃ reagent, no involvement of transition metals or external oxidant, and room-temperature conditions. Moreover, a scale-up of the reaction, further transformation of the products into various valuable CF₃ -containing compounds, and removal of the trifluoromethyl group are readily achieved.

Fe-polyaniline composite nanofiber catalyst for chemoselective hydrolysis of oxime

A facile chemoselective one-pot strategy for the deprotection of oxime has been developed using Fe⁰-polyaniline composite nanofiber (Fe⁰-PANI), as a catalyst. Nano material based Fe⁰-PANI catalyst has been synthesized via in-situ polymerization of ANI monomer and followed by reductive deposition of Fe⁰ onto PANI matrix. The catalyst was characterized by FE-SEM, HR-TEM, BET, XRD, ATR-FTIR, XPS and VSM techniques. The scope of the transformation was studied for aryl, alkyl and heteroarylketoxime with excellent chemoselectivity (>99%). Mechanistic investigations suggested the involvement of a cationic intermediate with Fe³⁺ active catalytic species. Substituent effect showed a linear free energy relationship. The activation energy (E_a) was calculated to be 17.46 kJ mol^-1 for acetophenone oxime to acetophenone conversion. The recyclability of the catalyst demonstrated up to 10 cycles without any significant loss of efficiency. Based on the preliminary experiments a plausible mechanism has been proposed involving a carbocationic intermediate.

Metal-Involving Synthesis and Reactions of Oximes

This review classifies and summarizes the past 10-15 years of advancements in the field of metal-involving (i.e., metal-mediated and metal-catalyzed) reactions of oximes. These reactions are diverse in nature and have been employed for syntheses of oxime-based metal complexes and cage-compounds, oxime functionalizations, and the preparation of new classes of organic species, in particular, a wide variety of heterocyclic systems spanning small 3-membered ring systems to macroheterocycles. This consideration gives a general outlook of reaction routes, mechanisms, and driving forces and underlines the potential of metal-involving conversions of oxime species for application in various fields of chemistry and draws attention to the emerging putative targets.

The design, synthesis and biological evaluation of novel thiamin diphosphate analog inhibitors against the pyruvate dehydrogenase multienzyme complex E1 from Escherichia coli

Optimal binding mode for the novel potent inhibitor 4j against PDHc-E1 from E. coli.

Asymmetric synthesis of nonracemic primary amines via spiroborate-catalyzed reduction of pure (E)- and (Z)-O-benzyloximes: applications toward the synthesis of calcimimetic agents

Highly enantiopure (1-aryl)- and (1-naphthyl)-1-ethylamines were synthesized by the borane-mediated reduction of single-isomeric (E)- and (Z)-O-benzyloxime ethers using the stable spiroborate ester derived from (S)-diphenyl valinol and ethylene glycol as the chiral catalyst. Primary (R)-arylethylamines were prepared by the reduction of pure (Z)-ethanone oxime ethers in up to 99% ee using 15% of catalyst. Two convenient and facile approaches to the synthesis of new and known calcimimetic analogues employing enantiopure (1-naphthalen-1-yl)ethylamine as chiral precursor are described.