Shunsuke Chiba 교수

Recent developments in experimental and computational chemistry have identified a rapidly growing class of nucleophilic aromatic substitutions that proceed by concerted (cS_N Ar) rather than classical, two-step, S_N Ar mechanisms. Whereas traditional S_N Ar reactions require substantial activation of the aromatic ring by electron-withdrawing substituents, such activating groups are not mandatory in the concerted pathways.

This review updates on recent advances in aliphatic sp(3) C-H bond oxidation by remote H-radical abstraction with oxygen- and nitrogen-radicals classifying by the type of the radical precursors.

A copper-catalyzed reaction of alpha-azido-N-arylamides was found to proceed under an oxygen atmosphere to afford azaspirocyclohexadienones. The present transformation is carried out by a sequence of denitrogenative formation of iminyl copper species from alpha-azido-N-arylamides and their imino-cupration with an intramolecular benzene ring on the amido nitrogen followed by consecutive formation of C=O bonds. The preliminary investigation revealed that molecular oxygen is a prerequisite for achi

In this account, recent advances made on the reactions of several types of organic azides, such as vinyl azides, cyclic 2-azido alcohols, a-azido carbonyl compounds, towards the synthesis of nitrogen-containing molecules are described.

Two synthetic methods for tetra- and trisubstituted N-H pyrroles are presented: (i) the thermal pyrrole formation by the reaction of vinyl azides with 1,3-dicarbonyl compounds via the 1,2-addition of 1,3-dicarbonyl compounds to 2H-azirine intermediates generated in situ from vinyl azides; (ii) the Cu(II)-catalyzed synthesis of pyrroles from alpha-ethoxycarbonyl vinyl azides and ethyl acetoacetate through the 1,4-addition reaction of the acetoacetate to the vinyl azides. By applying these two met

This review updates recent advances in Cu-catalyzed (anaerobic) oxidative carbon-heteroatom bond formation on sp(3)- and sp(2)-C-H bonds as well as alkenes, classified according to the types of stoichiometric oxidants.

The fluorine-containing organic motif is becoming privileged in pharmaceuticals, agrochemicals, and functional materials, owing to its unique properties such as electron-withdrawing character, metabolic stability, and lipophilicity. Described herein is the PhI(OAc)2 -mediated radical trifluoromethylation of vinyl azides with Me3 SiCF3 to efficiently generate α-trifluoromethyl azines. The resulting α-trifluoromethyl azines were successfully transformed to valuable fluorine-containing molecules su

A Pd(II)-catalyzed ring expansion-reaction of cyclic 2-azidoalcohol derivatives was found to proceed via an unprecedented C-C bond cleavage-C-N bond formation sequence, providing substituted azaheterocycles.

A copper-catalyzed reaction of alpha-azidocarbonyl compounds under an oxygen atmosphere is reported where nitriles are formed via C-C bond cleavage of a transient iminyl copper intermediate. The transformation is carried out by a sequence of denitrogenative formation of iminyl copper species from alpha-azidocarbonyl compounds and their C-C bond cleavage, where molecular oxygen (1 atm) is a prerequisite to achieve the catalytic process and one of the oxygen atoms of O(2) was found to be incorpora

Polysulfide anions are endowed with unique redox properties, attracting considerable attentions for their applications in alkali metals–sulfur batteries. However, the employment of these anionic species in redox catalysis for small molecule synthesis remains underdeveloped due to their moderate–poor electrochemical potential in the ground state, whereas some of them are characterized by photoabsorptions in visible spectral regions. Herein, we disclose the use of polysulfide anions as visible lig

A simple protocol for hydrodebromination and -deiodination of halo(hetero)arenes was enabled by sodium hydride (NaH) in the presence of lithium iodide (LiI). Mechanistic studies showed that an unusual concerted nucleophilic aromatic substitution operates in the present process.

A method for the synthesis of amide-containing molecules was developed using vinyl azides as an enamine-type nucleophile towards carbon electrophiles, such as imines, aldehydes, and carbocations that were generated from alcohols in the presence of BF3 ⋅OEt2 . After nucleophilic attack of the vinyl azide, a substituent of the resulting iminodiazonium ion intermediate migrates to form a nitrilium ion, which is hydrolyzed to afford the corresponding amide.

The first total synthesis of (-)-sordarin (1) was accomplished exploiting the following key reactions: (i) Ag(I)-catalyzed oxidative radical cyclization of a cyclopropanol derivative leading to a bicyclo[5.3.0]decan-3-one skeleton; (ii) Pd(0)-catalyzed intramolecular allylation reaction resulting in the entire strained bicyclo[2.2.1]heptan-2-one framework of sordaricin (2); (iii) selective dihydroxylation of terminal alkenes by the combined use of OsO(4) and PhB(OH)(2); and (iv) beta(1,2-cis)-se

Abstract This Highlight Review describes a Cu–Rh bimetallic redox relay catalytic system that enables efficient synthesis of highly substituted isoquinolines and their derivatives from readily available aryl ketoximes or α-arylvinyl azides with internal alkynes via C–H bond functionalization. A preliminary mechanistic investigation revealed that both the Cu and Rh catalysts are prerequisites to achieve the present process, and play their particular roles with synergistic cooperation during the m

Sodium hydride (NaH) is widely used as a Brønsted base in chemical synthesis and reacts with various Brønsted acids, whereas it rarely behaves as a reducing reagent through delivery of the hydride to polar π electrophiles. This study presents a series of reduction reactions of nitriles, amides, and imines as enabled by NaH in the presence of LiI or NaI. This remarkably simple protocol endows NaH with unprecedented and unique hydride-donor chemical reactivity.