scholarly journals Intermolecular Diastereoselective Annulation of Azaarenes into Fused N-heterocycles by Ru(II) Reductive Catalysis

2021 ◽  
Author(s):  
He Zhao ◽  
Yang Wu ◽  
Chenggang Ci ◽  
Zhenda Tan ◽  
Jian Yang ◽  
...  
Keyword(s):  
Building Block ◽  
Transfer Rate ◽  
Hydrogen Transfer ◽  
Functional Group ◽  
Critical Role ◽  
Hydride Transfer ◽  
Mechanistic Studies ◽  
Mild Conditions ◽  
Excellent Selectivity ◽  
Coupling Sequence

Abstract Despite the important advances in azaaryl C−H activation/functionalization, reductive functionalization of ubiquitously distributed but weakly reactive azaarenes remains to date a challenge. Herein, by a strategy incorporating a tandem coupling sequence into the reduction of azaarenes, we present a dearomative annulation of azaarenes into promising fused syn-N-heterocycles by combination with a large variety of aniline derivatives and paraformaldehyde under ruthenium(II) reductive catalysis, proceeding with excellent selectivity, mild conditions, and broad substrate and functional group compatibility. Mechanistic studies reveal that the products are formed via hydride transfer-initiated β-aminomethylation and α-arylation of the pyridyl core in azaarenes, paraformaldehyde serves as both the C1-building block and reductant precursor, and the use of Mg(OMe)2 base plays a critical role in determining the reaction chemo-selectivity by lowering the hydrogen transfer rate. The present work opens a door to further develop valuable reductive functionalization of unsaturated systems by taking profit of formaldehyde-endowed two functions.

scholarly journals Halogen-bonding-promoted Photo-induced C–X Borylation of Aryl Halide using Phenol Derivatives

2022 ◽  
Author(s):  
Kazuki Matsuo ◽  
Eiji Yamaguchi ◽  
Akichika Itoh
Keyword(s):  
Functional Group ◽  
Aryl Halide ◽  
Halogen Bonding ◽  
Mechanistic Studies ◽  
Boronate Esters ◽  
Aryl Radicals ◽  
Phenol Derivatives ◽  
Mild Conditions ◽  
Donor Acceptor ◽  
Photo Induced Electron Transfer

This study investigates the photo-induced C–X borylation reaction of aryl halides by forming a halogen-bonding complex. The method employs 2-naphthol as a halogen-bonding acceptor and proceeds under mild conditions without a photoredox catalyst under 420 nm blue light irradiation. The method is highly chemoselective, broadly functional group tolerant, and provides concise access to corresponding boronate esters. Mechanistic studies reveal that forming the halogen-bonding complex between aryl halide and naphthol acts as an electron donor-acceptor complex to furnish aryl radicals through photo-induced electron transfer.

Acetic Acid-Promoted Rhodium(III)-Catalyzed Hydroarylation of Terminal Alkynes

Synlett ◽  
2019 ◽  
Vol 30 (08) ◽  
pp. 932-938 ◽  
Author(s):  
Chang-Lin Duan ◽  
Xing-Yu Liu ◽  
Yun-Xuan Tan ◽  
Rui Ding ◽  
Shiping Yang ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Functional Group ◽  
Bond Activation ◽  
Side Reactions ◽  
Terminal Alkynes ◽  
Terminal Alkyne ◽  
Mechanistic Studies ◽  
Mild Conditions ◽  
Reaction Proceeds

Rhodium(III)-catalyzed hydroarylation of terminal alkynes has not previously been achieved because of the inevitable oligomerization and other side reactions. Here, we report a novel Cp*Rh(III)-catalyzed hydroarylation of terminal alkynes in acetic acid as solvent to facilitate the C–H bond activation and subsequent transformations. This reaction proceeds under mild conditions, providing an effective approach to the synthesis of alkenylated heterocycles in high to excellent yields (31–99%) with a broad substrate scope (37 examples) and good functional-group compatibility. In this transformation, the loading of the alkyne can be reduced to 1.2 equivalents, which indicates the significant role of HOAc in lowering the reaction temperature and suppressing the oligomerization of the terminal alkyne. Preliminary mechanistic studies are also presented.

Iridium-Catalyzed Silylation of C-H bonds in Unactivated Arenes: A Sterically-Encumbered Phenanthroline Ligand Accelerates Catalysis Enabling New Reactivity

2019 ◽  
Author(s):  
Caleb Karmel ◽  
Zhewei Chen ◽  
John Hartwig
Keyword(s):  
High Activity ◽  
Functional Group ◽  
Activity Analysis ◽  
High Reactivity ◽  
High Yield ◽  
Phen Ligand ◽  
Mechanistic Studies ◽  
Phenanthroline Ligand ◽  
First Time ◽  
New System

We report a new system for the silylation of aryl C-H bonds. The combination of [Ir(cod)(OMe)]<sub>2</sub> and 2,9-Me<sub>2</sub>-phenanthroline (2,9-Me<sub>2</sub>phen) catalyzes the silylation of arenes at lower temperatures and with faster rates than those reported previously, when the hydrogen byproduct is removed, and with high functional group tolerance and regioselectivity. Inhibition of reactions by the H<sub>2</sub> byproduct is shown to limit the silylation of aryl C-H bonds in the presence of the most active catalysts, thereby masking their high activity. Analysis of initial rates uncovered the high reactivity of the catalyst containing the sterically hindered 2,9-Me<sub>2</sub>phen ligand but accompanying rapid inhibition by hydrogen. With this catalyst, under a flow of nitrogen to remove hydrogen, electron-rich arenes, including those containing sensitive functional groups, undergo silylation in high yield for the first time, and arenes that underwent silylation with prior catalysts react over much shorter times with lower catalyst loadings. The synthetic value of this methodology is demonstrated by the preparation of key intermediates in the synthesis of medicinally important compounds in concise sequences comprising silylation and functionalization. Mechanistic studies demonstrate that the cleavage of the aryl C-H bond is reversible and that the higher rates observed with the 2,9-Me<sub>2</sub>phen ligand is due to a more thermodynamically favorable oxidative addition of aryl C-H bonds.

Asymmetric Synthesis of α-Alkylated γ-Lactam via Nickel/8-Quinim-Catalyzed Reductive Alkyl-Carbamoylation of Unactivated Alkene

Synlett ◽  
2021 ◽  
Author(s):  
Xianqing Wu ◽  
Mohini Shrestha ◽  
Yifeng Chen
Keyword(s):  
Functional Group ◽  
Enantioselective Synthesis ◽  
Chiral Auxiliary ◽  
Alkyl Iodide ◽  
General Strategy ◽  
Chemical Bonds ◽  
Mild Conditions ◽  
Chiral Carbon ◽  
Enantioselective Reaction ◽  
Metal Catalyzed

AbstractChiral-auxiliary-mediated synthesis represents the most frequently used synthetic tool for the induction of chirality on α-position of γ-lactams in organic synthesis. However, the general strategy requires the stoichiometric use of chiral reagents with multiple manipulation steps. Transition-metal-catalyzed asymmetric alkene dicarbofunctionalization using readily available substrates under mild conditions allows the simultaneous construction of two vicinal chemical bonds and a chiral carbon center, hence, gain expedient access to chiral heterocycles. Herein, we disclose a Ni-catalyzed enantioselective reaction of 3-butenyl carbamoyl chloride and primary alkyl iodide enabled by a newly designed chiral 8-quinoline imidazoline ligand (8-Quinim). This protocol features broad functional group tolerance and high enantioselectivities, achieving unprecedented synthesis of chiral nonaromatic heterocycles via catalytic reductive protocol.1 Introduction2 Development of 8-Quinim Ligand3 Nickel/8-Quinim-Catalyzed Enantioselective Synthesis of Chiral α-Alkylated γ-Lactam4 Conclusion and Outlook

Rh (III)-catalyzed C(sp2)-H functionalization/cyclization cascade of N-carboxamide indole and iodonium reagent for access to indoloquinazolinone derivatives

2021 ◽  
Author(s):  
Zhi-Peng Han ◽  
Mengmeng Xu ◽  
Rui-Ying Zhang ◽  
Xiao-Ping Xu ◽  
Shun-Jun Ji
Keyword(s):  
Functional Group ◽  
Mild Conditions

Rhodium-catalyzed synthesis of indoloquinazoline from readily available hypervalent iodonium reagent and N-carboxamide indole was developed. The protocol features broad functional group tolerance, mild conditions, excellent yields and simple workup. Notably,...

scholarly journals Homocoupling of terminal alkynes catalyzed by CuCl under solvent-free conditions

2021 ◽  
pp. 174751982110325
Author(s):  
Yan Xiao ◽  
Jiyu Gao ◽  
Peng Chen ◽  
Guangliang Chen ◽  
Zicheng Li ◽  
...  
Keyword(s):  
Functional Group ◽  
Reaction Times ◽  
Environmentally Friendly ◽  
Solvent Free ◽  
Copper Salt ◽  
Terminal Alkynes ◽  
Mild Conditions ◽  
Solvent Free Conditions ◽  
Environmentally Friendly Process

A series of symmetrical 1,4-disubstituted buta-1,3-diynes is prepared with excellent yields (up to 95%) through homocoupling of terminal alkynes catalyzed by a copper salt under solvent-free conditions. This method provides an environmentally friendly process to prepare 1,3-diynes in short reaction times under mild conditions. Furthermore, the method is suitable for a wide substrate scope and has excellent functional group compatibility. The reaction can also be scaled up to gram level.

scholarly journals Transition-Metal-Free Boryl Substitution Using Silylboranes and Alkoxy Bases

Synlett ◽  
2017 ◽  
Vol 28 (11) ◽  
pp. 1258-1267 ◽  
Author(s):  
Hajime Ito ◽  
Eiji Yamamoto ◽  
Satoshi Maeda ◽  
Tetsuya Taketsugu
Keyword(s):  
Transition Metal ◽  
Functional Group ◽  
Experimental Studies ◽  
Transition Metal Catalysts ◽  
Alkyl Halides ◽  
Aryl Halides ◽  
Nucleophilic Attack ◽  
Important Class ◽  
Mechanistic Studies ◽  
Induced Reaction

Silylboranes are used as borylation reagents for organohalides in the presence of alkoxy bases without transition-metal catalysts. PhMe2Si–B(pin) reacts with a variety of aryl, alkenyl, and alkyl halides, including sterically hindered examples, to provide the corresponding organoboronates in good yields with high borylation/silylation ratios, showing good functional group compatibility. Halogenophilic attack of a silyl nucleophile on organohalides, and subsequent nucleophilic attack on the boron electrophile are identified to be crucial, based on the results of extensive theoretical and experimental studies. This boryl­ation reaction is further applied to the first direct dimesitylboryl (BMes2) substitution of aryl halides using Ph2MeSi–BMes2 and Na(O-t-Bu), affording aryldimesitylboranes, which are regarded as an important class of compounds for organic materials.1 Introduction2 Boryl Substitution of Organohalides with PhMe2Si–B(pin)/Alkoxy Bases3 Mechanistic Investigations4 DFT Mechanistic Studies Using an Artificial Force Induced Reaction (AFIR) Method5 Dimesitylboryl Substitution of Aryl Halides with Ph2MeSi–BMes2/Na(O-t-Bu)6 Conclusion

Direct and metal-free oxidative amination of sp3 C–H bonds for the construction of 2-hetarylquinazolin-4(3H)-ones

2016 ◽  
Vol 3 (9) ◽  
pp. 1096-1099 ◽  
Author(s):  
Huanhuan Liu ◽  
Tianran Zhai ◽  
Shiteng Ding ◽  
Yalei Hou ◽  
Xiangyu Zhang ◽  
...  
Keyword(s):  
Transition Metal ◽  
Functional Group ◽  
New Method ◽  
Oxidative Amination ◽  
Metal Free ◽  
Mild Conditions

New method for synthesis of 2-hetarylquinazolin-4(3H)-ones from 2-aminobenzamides and (2-azaaryl)methanes under transition-metal free conditions, featuring a wide substrate scope with a broad range of functional group tolerance under mild conditions.

scholarly journals Selective oxidation of uronic acids into aldaric acids over gold catalyst

RSC Advances ◽  
2015 ◽  
Vol 5 (25) ◽  
pp. 19502-19507 ◽  
Author(s):  
Sari Rautiainen ◽  
Petra Lehtinen ◽  
Jingjing Chen ◽  
Marko Vehkamäki ◽  
Klaus Niemelä ◽  
...  
Keyword(s):  
Selective Oxidation ◽  
Building Block ◽  
Gold Catalyst ◽  
Uronic Acids ◽  
Mild Conditions ◽  
Aldaric Acids

Uronic acids available from hemicelluloses were oxidized into aldaric acids, valuable building block chemicals. Au/Al2O3 oxidized glucuronic and galacturonic acids quantitatively to the corresponding glucaric and galactaric acids at mild conditions.

Sign in / Sign up

Export Citation Format

Share Document