scholarly journals Thiocarbonyl-enabled ferrocene C–H nitrogenation by cobalt(III) catalysis: thermal and mechanochemical

2018 ◽  
Vol 14 ◽  
pp. 1546-1553 ◽  
Author(s):  
Santhivardhana Reddy Yetra ◽  
Zhigao Shen ◽  
Hui Wang ◽  
Lutz Ackermann
Keyword(s):  
Functional Group ◽  
Strong Support ◽  
Mechanistic Studies ◽  
Weakly Coordinating

Versatile C–H amidations of synthetically useful ferrocenes were accomplished by weakly-coordinating thiocarbonyl-assisted cobalt catalysis. Thus, carboxylates enabled ferrocene C–H nitrogenations with dioxazolones, featuring ample substrate scope and robust functional group tolerance. Mechanistic studies provided strong support for a facile organometallic C–H activation manifold.

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.

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

scholarly journals Intermolecular 3+3 Ring Expansion of Aziridines to Dehydropiperidines through the Intermediacy of Aziridinium Ylides

2019 ◽  
Author(s):  
Jennifer Schomaker ◽  
Josephine Eshon ◽  
Kate A. Nicastri ◽  
Steven C. Schmid ◽  
William T. Raskopf ◽  
...  
Keyword(s):  
Natural Product ◽  
Functional Group ◽  
Ring Expansion ◽  
Sigmatropic Rearrangement ◽  
Reactive Intermediate ◽  
Mechanistic Studies ◽  
Reaction Conditions ◽  
Complex Molecules ◽  
Form Complex ◽  
Reaction Proceeds

Bicyclic aziridines undergo formal [3+3] ring expansion reactions when exposed to rhodium-bound vinyl carbenes to form complex dehydropiperidines in a highly stereocontrolled rearrangement. Mechanistic studies and DFT computations indicate the reaction proceeds through the formation of a vinyl aziridinium ylide; this reactive intermediate undergoes a concerted, asynchronous, pseudo-[1,4]- sigmatropic rearrangement to directly furnish the heterocyclic products with net retention at the new C-C bond. In combination with an asymmetric silver-catalyzed aziridination developed in our group, this method quickly delivers enantioenriched scaffolds with up to three contiguous stereocenters. The mild reaction conditions, functional group tolerance, and high stereochemical retention of this method are especially well-suited for appending piperidine motifs to natural product and complex molecules. Ultimately, our work establishes the value of underutilized aziridinium ylides as key intermediates in strategies to convert small, strained rings to larger N-heterocycles.

scholarly journals Cu/Pd-catalyzed borocarbonylative trifunctionalization of alkynes and allenes: synthesis of β-geminal-diboryl ketones

2021 ◽  
Author(s):  
Yang Yuan ◽  
Fu-Peng Wu ◽  
Anke Spannenberg ◽  
Xiao-Feng Wu
Keyword(s):  
Organic Synthesis ◽  
Functional Group ◽  
Building Blocks ◽  
Mechanistic Studies ◽  
Efficient Strategy ◽  
New Class ◽  
Reaction Proceeds

AbstractFunctionalized bisboryl compounds have recently emerged as a new class of synthetically useful building blocks in organic synthesis. Herein, we report an efficient strategy to synthesize β-geminal-diboryl ketones enabled by a Cu/Pd-catalyzed borocarbonylative trifunctionalization of readily available alkynes and allenes. This reaction promises to be a useful method for the synthesis of functionalized β-geminal-diboryl ketones with broad functional group tolerance. Mechanistic studies suggest that the reaction proceeds through borocarbonylation/hydroboration cascade of both alkynes and allenes.

Electrophilic Amination with Anthranils through Thioamide-Assisted Cobalt(III)-Catalyzed C(sp3)–H Activation

Synthesis ◽  
2020 ◽  
Vol 52 (24) ◽  
pp. 3881-3890
Author(s):  
Jie Li ◽  
Lei Liu ◽  
Zhao Zhang ◽  
Yucheng Wang ◽  
Yan Zhang
Keyword(s):  
Late Stage ◽  
Functional Group ◽  
Atom Economy ◽  
Electrophilic Amination ◽  
Amino Aldehydes ◽  
Mild Conditions ◽  
Weakly Coordinating

Cobalt(III)-catalyzed electrophilic amination of inert C(sp3)–H bonds of weakly coordinating thioamides with readily accessible anthranil derivatives was accomplished under mild conditions, with good functional group tolerance, thus providing various amino aldehydes and amino ketones. Moreover, our protocol with the versatile [Cp*Co(MeCN)3][SbF6]2 features excellent atom-economy and oxidant-free conditions, and allows facile late-stage functionalization.

scholarly journals Pd-catalyzed intramolecular addition of active methylene compounds to alkynes with subsequent cross-coupling with (hetero)aryl halides

RSC Advances ◽  
2019 ◽  
Vol 9 (68) ◽  
pp. 40152-40167 ◽  
Author(s):  
Aleksandra Błocka ◽  
Paweł Woźnicki ◽  
Marek Stankevič ◽  
Wojciech Chaładaj
Keyword(s):  
Functional Group ◽  
Cross Coupling ◽  
Aryl Halides ◽  
Mechanistic Studies ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Active Methylene Compounds ◽  
Tandem Cyclization ◽  
Rate Limiting ◽  
Active Methylene

A tandem cyclization/coupling of acetylenic active methylene compounds with aryl halides features broad scope and excellent functional group compatibility. Mechanistic studies identified 5-exo-dig cyclization as the rate limiting step.

Cobalt Catalyzed Hydroarylation of Michael Acceptors with Indolines Directed by a Weakly Coordinating Functional Group

2019 ◽  
Vol 21 (11) ◽  
pp. 4049-4053 ◽  
Author(s):  
Shyam Kumar Banjare ◽  
Rajesh Chebolu ◽  
P. C. Ravikumar
Keyword(s):  
Functional Group ◽  
Michael Acceptors ◽  
Weakly Coordinating

scholarly journals Weinreb Amides as Directing Groups for Transition Metal-Catalyzed C-H Functionalizations

Molecules ◽  
2019 ◽  
Vol 24 (5) ◽  
pp. 830 ◽  
Author(s):  
Jagadeesh Kalepu ◽  
Lukasz Pilarski
Keyword(s):  
Transition Metal ◽  
Functional Group ◽  
Metal Catalysts ◽  
Mechanistic Studies ◽  
Weinreb Amides ◽  
Transition Metal Catalyzed ◽  
Metal Catalyzed

Weinreb amides are a privileged, multi-functional group with well-established utility in classical synthesis. Recently, several studies have demonstrated the use of Weinreb amides as interesting substrates in transition metal-catalyzed C-H functionalization reactions. Herein, we review this part of the literature, including the metal catalysts, transformations explored so far and specific insights from mechanistic studies.

C–H Functionalization Reactions of Phenyl and Vinyl Carbocations Paired with Weakly Coordinating Anions

Synlett ◽  
2020 ◽  
Vol 31 (19) ◽  
pp. 1851-1856
Author(s):  
Hosea M. Nelson ◽  
Stasik Popov ◽  
Brian Shao ◽  
Alex L. Bagdasarian ◽  
Benjamin Wigman
Keyword(s):  
High Energy ◽  
Mechanistic Studies ◽  
Insertion Reactions ◽  
Weakly Coordinating Anions ◽  
Recent Developments ◽  
Weakly Coordinating ◽  
Weakly Coordinating Anion

Carbocations have played a central role in the chemical sciences for over a century. In a synthetic setting, most methods utilize stabilized tricoordinate carbocations, while there are far fewer examples of reactions featuring nonstabilized dicoordinate cations. Here, we provide an overview of recent developments in the generation of high-energy carbocations mediated by weakly coordinating anions and the C–H insertion reactions of such carbocations. Moreover, we discuss mechanistic studies of these catalytic C–H insertion reactions aimed at furthering our understanding of the reactive nature of these rarely invoked cationic intermediates.1 Introduction2 Background: Phenyl Carbocations3 Silylium/Carborane-Catalyzed C–H Insertion Reactions of Phenyl Carbocations4 Silane-Fueled, Weakly Coordinating Anion-Catalyzed, Reductive C–H Insertion Reactions of Vinyl Carbocations5 C–H Insertion Reactivity of Vinyl Carbocations under Basic Conditions6 Conclusion and Outlook

scholarly journals Palladium-catalyzed Heck-type reaction of secondary trifluoromethylated alkyl bromides

2017 ◽  
Vol 13 ◽  
pp. 2610-2616 ◽  
Author(s):  
Tao Fan ◽  
Wei-Dong Meng ◽  
Xingang Zhang
Keyword(s):  
Alkyl Radical ◽  
Functional Group ◽  
High Efficiency ◽  
Mechanistic Studies ◽  
Reaction Conditions ◽  
Type Reaction ◽  
Alkyl Bromides ◽  
Reaction Proceeds ◽  
Palladium Catalyzed ◽  
Hydroxy Groups

An efficient palladium-catalyzed Heck-type reaction of secondary trifluoromethylated alkyl bromides has been developed. The reaction proceeds under mild reaction conditions with high efficiency and excellent functional group tolerance, even towards formyl and hydroxy groups. Preliminary mechanistic studies reveal that a secondary trifluoromethylated alkyl radical is involved in the reaction.

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