Recent advances in the chemistry and applications of N-heterocyclic carbenes

Nature Reviews Chemistry, Journal Year: 2021, Volume and Issue: 5(10), P. 711 - 725

Published: Sept. 3, 2021

Language: Английский

---

First-Row d-Block Element-Catalyzed Carbon–Boron Bond Formation and Related Processes

Chemical Reviews, Journal Year: 2021, Volume and Issue: 121(21), P. 13238 - 13341

Published: Oct. 7, 2021

Organoboron reagents represent a unique class of compounds because their utility in modern synthetic organic chemistry, often affording unprecedented reactivity. The transformation the carbon–boron bond into carbon–X (X = C, N, and O) stereocontrolled fashion has become invaluable medicinal agrochemistry, natural products chemistry as well materials science. Over past decade, first-row d-block transition metals have increasingly widely used catalysts for formation bond, traditionally catalyzed by expensive precious metals. This recent focus on alternative enabled growth fundamental methods organoboron chemistry. review surveys current state-of-the-art use element-based bonds.

Language: Английский

---

Copper-Catalyzed Borylative Difunctionalization of π-Systems

ACS Catalysis, Journal Year: 2020, Volume and Issue: 10(19), P. 11578 - 11622

Published: Aug. 25, 2020

Organoboronates represent a cornerstone functional group in modern synthesis owing to their unique reactivity and divergent synthetic capability. Copper catalysis has become one of the most powerful methods stereoselectively install boron across diverse π-systems. Additionally, this method affords tremendous versatility enabled by difunctionalization π-system addition an electrophile. This review covers known electrophiles intercept catalytic intermediates borylative strategies that have been reported up end May 2020.

Language: Английский

---

Beyond Carbon: Enantioselective and Enantiospecific Reactions with Catalytically Generated Boryl- and Silylcopper Intermediates

ACS Central Science, Journal Year: 2020, Volume and Issue: 6(7), P. 1070 - 1081

Published: July 9, 2020

Catalytic asymmetric C–C bond formation with alkylcopper intermediates as carbon nucleophiles is now textbook chemistry. Related chemistry boron and silicon where the boryl- accordingly silylcopper are catalytically regenerated from bench-stable pronucleophiles had been underdeveloped for years or did not even exist until recently. Over past decade, copper catalysis employing those main-group elements rapidly transformed into a huge field in its own right an impressive breadth of enantioselective C–B C–Si bond-forming reactions, respectively. Its current state art does have to shy away comparison that boron's silicon's common neighbor periodic table, carbon. This Outlook meant be detailed summary manifold advances. It rather aims at providing brief conceptual what forms basis latest exciting progress, especially area three-component reactions cross-coupling reactions.

Language: Английский

---

Catalytic Chemo- and Enantioselective Transformations of gem-Diborylalkanes and (Diborylmethyl)metallic Species

Accounts of Chemical Research, Journal Year: 2021, Volume and Issue: 54(20), P. 3917 - 3929

Published: Oct. 6, 2021

ConspectusChemo- and stereoselective transformations of polyborylalkanes are powerful efficient methods to access optically active molecules with greater complexity diversity through programmed synthetic design. Among the various polyborylalkanes, gem-diborylalkanes have attracted much attention in organic chemistry as versatile handles. The notable advantage lies their ability generate two key intermediates, α-borylalkyl anions (gem-diborylalkyl) anions. These different intermediates can be applied enantioselective reactions rapidly a diverse set enantioenriched organoboron compounds, which further manipulated chiral molecule libraries via stereospecific C(sp3)–B bond transformations.In this Account, we summarize our recent contributions development catalytic chemo- using nucleophiles, categorized follows: (1) copper-catalyzed coupling electrophiles (2) design synthesis (diborylmethyl)metallic species applications reactions. Since Shibata Endo reported Pd-catalyzed chemoselective Suzuki–Miyaura cross-coupling organohalides 2014, Morken Hall subsequently developed first analogous TADDOL-derived phosphoramidite supporting ligand palladium catalyst. This discovery sparked interest electrophiles. Our initial studies focused on generating (α-borylmethyl)copper by enantiotopic-group-selective transmetalation copper complexes aldimines ketimines afford syn-β-aminoboronate esters excellent enantio- diastereoselectivity. Moreover, allylation that proceeded reaction situ-generated (α-borylalkyl)copper allyl bromides. Mechanistic investigations revealed between complex occurred open transition state rather than closed state, thereby effectively species. We also utilized such (diborylmethyl)silanes (diborylmethyl)zinc halides succeeded developing aryl iodides benzylic 1,1-silylboronate esters, could used for consecutive molecules. In addition, synthesized time isolated (diborylmethyl)lithium zinc(II) utilization bearing center at β-position an iridium-catalyzed allylic substitution process. addition research efforts, include other groups. hope Account will draw community gem-diboryl compounds provide guiding principles future compounds.

Language: Английский

---

BIAN‐NHC Ligands in Transition‐Metal‐Catalysis: A Perfect Union of Sterically Encumbered, Electronically Tunable N‐Heterocyclic Carbenes?

Chemistry - A European Journal, Journal Year: 2020, Volume and Issue: 27(14), P. 4478 - 4499

Published: Sept. 29, 2020

The discovery of NHCs (NHC = N-heterocyclic carbenes) as ancillary ligands in transition-metal-catalysis ranks one the most important developments synthesis and catalysis. It is now well-recognized that strong σ-donating properties along with ease scaffold modification a steric shielding N-wingtip substituents around metal center enable dramatic improvements catalytic processes, including reactions are not possible using other ligands. In this context, although classical based on imidazolylidene imidazolinylidene ring systems well-established, recently tremendous progress has been made development applications BIAN-NHC (BIAN bis(imino)acenaphthene) class enhanced reactivity BIAN-NHCs direct result combination electronic collectively allow for major expansion scope processes can be accomplished NHCs. take advantage (1) stronger σ-donation, (2) lower lying LUMO orbitals, (3) presence an extended π-system, (4) rigid backbone pushes closer to by buttressing effect, thus resulting significantly improved control air-stability BIAN-NHC-metal complexes at low oxidation state. Acenaphthoquinone precursor enables facile modification, first time high yielding unsymmetrical unique properties. Overall, results highly attractive, easily accessible bring advances emerge leading practical alternative various aspects catalysis, cross-coupling C-H activation endeavors.

Language: Английский

---

Design and Application of Chiral Bifunctional 4-Pyrrolidinopyridines: Powerful Catalysts for Asymmetric Cycloaddition of Allylic N-Ylide

ACS Catalysis, Journal Year: 2022, Volume and Issue: 12(12), P. 7221 - 7232

Published: June 2, 2022

We designed bifunctional 4-pyrrolidinopyridines as powerful Lewis base catalysts. The catalyst structure features a 4-hydroxy-2-(hydroxydiphenylmethyl)pyrrolidine-1-formyl group at the pyridine's C3 site and chiral side arm C2 position of p-pyrrolidine ring. An operationally simple three-step synthetic route allows for efficient economical preparation. In comparison with other bases, exhibits excellent efficiency stereoselectivity in asymmetric (3 + 2) cycloaddition allylic N-ylide generated situ from pyrazolone-derived Morita–Baylis–Hillman carbonate, providing platform construction spiropyrazolone derivatives. reaction mechanism was thoroughly studied. Control experiments DFT calculations illustrated origin chemoselectivity stereocontrol model. H-bonding is crucial control enantioselectivity diastereoselectivity. also successfully applied reactions, such an acylative dynamic kinetic resolution to synthesize phthalidyl ester, including prodrug Talmetacin.

Language: Английский

---

Copper-Catalyzed Yne-Allylic Substitutions Using Stabilized Nucleophiles

ACS Catalysis, Journal Year: 2022, Volume and Issue: 12(12), P. 6840 - 6850

Published: May 25, 2022

Using stabilized "soft" nucleophiles in copper-catalyzed allylic substitutions is highly desirable but remains an unsolved challenge for the last 40 years. In this work, a general protocol of using such as indoles, pyrroles, amines, and 1,3-dicarbonyls has been developed, delivering large variety functionalized 1,3- 1,4-enynes with high levels regio- stereoselectivities (67 examples). A range further transformations products can be easily achieved to release various molecules. mechanistic rationale copper acetylide-bonded cation key intermediate that features outer-sphere nucleophilic attack proposed. Additionally, series diversified reactivities have demonstrated, which will inspire studies.

Language: Английский

---

Copper-Catalyzed Coupling of Alkyl Vicinal Bis(boronic Esters) to an Array of Electrophiles

Journal of the American Chemical Society, Journal Year: 2022, Volume and Issue: 144(39), P. 17815 - 17823

Published: Sept. 22, 2022

A neighboring boronate group in the substrate provides a dramatic rate acceleration transmetalation to copper and thereby enables organoboronic esters participate unprecedented site-selective cross-couplings. This cross-coupling operates under practical experimental conditions allows for coupling between vicinal bis(boronic esters) allyl, alkynyl, propargyl electrophiles as well simple proton. Because reactive substrates are esters), described herein an expedient new method construction of boron-containing reaction products from alkenes. Mechanistic experiments suggest that chelated cyclic ate complexes may play role transmetalation.

Language: Английский

---

Transfer Hydrogenation of Aldehydes and Ketones in Air with Methanol and Ethanol by an Air-Stable Ruthenium–Triazole Complex

ACS Sustainable Chemistry & Engineering, Journal Year: 2021, Volume and Issue: 9(13), P. 4903 - 4914

Published: March 22, 2021

Coordination of 1,4-disubstituted 1,2,3-triazoles L1 and L2 with [(p-cymene)RuCl2]2 followed by dehydrochlorination in the presence a base resulted formation complexes 1 2, respectively. Both were tested for transfer hydrogenation aldehydes ketones air using ecologically benign cheap ethanol as hydrogen source catalytic amount base. Air-stable complex was proved to be an active catalyst wide variety aromatic aliphatic bearing various functionalities. Catalyst also effective carbonyls simplest primary alcohol, methanol, under aerobic conditions. Under present protocol, labile or reducible functionalities such nitro, cyano, ester groups tolerated. Good selectivity observed acyclic α,β-unsaturated carbonyls. However, this protocol not selective 2-cyclohexen-1-one both alkene keto moieties reduced. The hydrogenations are believed proceed via ruthenium-hydride intermediate. Finally, acetophenone isopropanol commonly used performed sustainable green credentials these protocols utilizing ethanol, compared help CHEM21 metrics toolkit.

Language: Английский

---