ZnMe2-Mediated, Direct Alkylation of Electron-Deficient N-Heteroarenes with 1,1-Diborylalkanes: Scope and Mechanism

The regioselective, direct alkylation of electron-deficient N-heteroarenes is, in principle, a powerful and efficient way of accessing alkylated N-heteroarenes that are important core structures of many biologically active compounds and pharmaceutical agents. Herein, we report a ZnMe2-promoted, direct C2- or C4-selective primary and secondary alkylation of pyridines and quinolines using 1,1-diborylalkanes as alkylation sources. While substituted pyridines and quinolines exclusively afford C2-alkylated products, simple pyridine delivers C4-alkylated pyridine with excellent regioselectivity. The reaction scope is remarkably broad, and a range of C2- or C4-alkylated electron-deficient N-heteroarenes are obtained in good yields. Experimental and computational mechanistic studies imply that ZnMe2 serves not only as an activator of 1,1-diborylalkanes to generate (alpha-borylalkyl)methylalkoxy zincate, which acts as a Lewis acid to bind to the nitrogen atom of the heterocycles and controls the regioselectivity, but also as an oxidant for rearomatizing the dihydro-N-heteroarene intermediates to release the product.11Nsciescopu

Base-promoted, deborylative secondary alkylation of N-heteroaromatic N-oxides with internal gem-bis[(pinacolato)boryl]alkanes: a facile derivatization of 2,2′-bipyridyl analogues

A base-promoted, secondary alkylation of N-heteroaromatic N-oxides using internal gem -bis[(pinacolato)boryl] alkanes as alkylation reagents is reported. The reaction exhibits a broad scope, providing deoxygenated secondary alkylated N-heteroaromatic compounds with high efficiency. The usefulness of the developed protocol is evidenced by the sequential direct alkylation of 2,2'-bipyridine-N-oxide.11166sciescopu

Diborylmethyl Group as a Transformable Building Block for the Diversification of Nitrogen-Containing Molecules

© 2022 Wiley-VCH GmbH.The development of new approaches to installing diverse carbon fragments to a nitrogen atom has attracted considerable attention in chemical science. While numerous strategies have been devised to forge C(sp3)−N bonds, one conceptually powerful and straightforward approach is to insert a transformable sp3-carbon unit onto a nitrogen atom for modular diversification. Here we describe the successful synthesis of halo-diborylmethanes and their applications to the preparation of nitrogen-substituted diborylmethanes through their homologative coupling with a variety of nitrogen nucleophiles including biologically relevant molecules. This process exhibits a remarkably broad substrate scope, and the usefulness of the obtained compounds is demonstrated by the modular diversification of the diborylmethyl group to access various nitrogen-containing molecules.11Nsciescopu

ZnMe2-Mediated, Direct Alkylation of Electron-Deficient N-Heteroarenes with 1,1-Diborylalkanes: Scope and Mechanism

© 2020 American Chemical Society The regioselective, direct alkylation of electron-deficient N-heteroarenes is, in principle, a powerful and efficient way of accessing alkylated N-heteroarenes that are important core structures of many biologically active compounds and pharmaceutical agents. Herein, we report a ZnMe2-promoted, direct C2- or C4-selective primary and secondary alkylation of pyridines and quinolines using 1,1-diborylalkanes as alkylation sources. While substituted pyridines and quinolines exclusively afford C2-alkylated products, simple pyridine delivers C4-alkylated pyridine with excellent regioselectivity. The reaction scope is remarkably broad, and a range of C2- or C4-alkylated electron-deficient N-heteroarenes are obtained in good yields. Experimental and computational mechanistic studies imply that ZnMe2 serves not only as an activator of 1,1-diborylalkanes to generate (alpha-borylalkyl)methylalkoxy zincate, which acts as a Lewis acid to bind to the nitrogen atom of the heterocycles and controls the regioselectivity, but also as an oxidant for rearomatizing the dihydro-N-heteroarene intermediates to release the product11sci

Facile Synthesis of alpha-Boryl-Substituted Allylboronate Esters Using Stable Bis[(pinacolato)boryl]methylzinc Reagents

Reported herein is the utilization of bis[(pinacolato)boryl]methylzinc halides, whose structures are characterized via single-crystal X-ray analysis, as solid storable reagents for copper-catalyzed coupling with vinyliodonum salts. The reaction proceeds under mild conditions and shows broad scope with respect to vinyliodonium salts, affording various alpha-boryl-substituted allylboronate esters in good yields. Synthetic applications of the obtained products are also demonstrated.11Nsciescopu

The effect of epigallocatechin gallate on suppressing disease progression of ALS model mice

Epigallocatechin gallate (EGCG) is a constituent of green tea, and increasing evidence suggests that EGCG has neuroprotective effects on oxidative stress-injured neuronal cells, especially motoneurons. Although the neuroprotective effects of EGCG have been demonstrated in Parkinson's and Alzheimer's diseases and ischemic stroke models, there has been no report on the effect of EGCG on an in vivo model of amyotrophic lateral sclerosis (ALS). This study was undertaken to evaluate the effect of EGCG on ALS model mice with the human G93A mutated Cu/Zn-superoxide dismutase (SOD1) gene. We treated each group of 11 ALS model mice with EGCG (1.5, 2.9, and 5.8 microg/g body weight), dissolved in 0.5 ml of 0.9% sterile NaCl, and one group of 11 with 0.5 ml of 0.9% sterile NaCl (control group) intraorally every day after 60 days of age (presymptomatic treatment). The treatment of more than 2.9 microg EGCG/g body weight significantly prolonged the symptom onset and life span, preserved more survival signals, and attenuated death signals. These data suggest that EGCG could be a potential therapeutic candidate for ALS as a disease-modifying agent.This work was supported by the research fund of Hanyang University (HY-2005-I)