Electrochemical C–H functionalization and subsequent C–S and C–N bond formation: paired electrosynthesis of 3-amino-2-thiocyanato-α,β-unsaturated carbonyl derivatives mediated by bromide ions

2016 ◽  
Vol 18 (13) ◽  
pp. 3767-3774 ◽  
Author(s):  
Li-Shuo Kang ◽  
Mi-Hai Luo ◽  
Chiu Marco Lam ◽  
Li-Ming Hu ◽  
R. Daniel Little ◽  
...  
Keyword(s):  
Bond Formation ◽  
Carbonyl Derivatives ◽  
Paired Electrosynthesis ◽  
Bromide Ions

An efficient paired electrosynthesis involving C–H functionalization and subsequent C–S and C–N bond formation has been developed.

scholarly journals Transition Metal-Catalyzed α-Position Carbon–Carbon Bond Formations of Carbonyl Derivatives

Catalysts ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 861 ◽  
Author(s):  
Ha-Eun Lee ◽  
Dopil Kim ◽  
Ahrom You ◽  
Myung Hwan Park ◽  
Min Kim ◽  
...  
Keyword(s):  
Transition Metal ◽  
Carbonyl Compounds ◽  
Bond Formation ◽  
Chiral Ligand ◽  
Catalytic Systems ◽  
Carbon Bond ◽  
Carbonyl Derivatives ◽  
Carbon Carbon Bond ◽  
Transition Metal Catalyzed ◽  
Metal Catalyzed

α-Functionalization of carbonyl compounds in organic synthesis has traditionally been accomplished via classical enolate chemistry. As α-functionalized carbonyl moieties are ubiquitous in biologically and pharmaceutically valuable molecules, catalytic α-alkylations have been extensively studied, yielding a plethora of practical and efficient methodologies. Moreover, stereoselective carbon–carbon bond formation at the α-position of achiral carbonyl compounds has been achieved by using various transition metal–chiral ligand complexes. This review describes recent advances—in the last 20 years and especially focusing on the last 10 years—in transition metal-catalyzed α-alkylations of carbonyl compounds, such as aldehydes, ketones, imines, esters, and amides and in efficient carbon–carbon bond formations. Active catalytic species and ligand design are discussed, and mechanistic insights are presented. In addition, recently developed photo-redox catalytic systems for α-alkylations are described as a versatile synthetic tool for the synthesis of chiral carbonyl-bearing molecules.

Stereodivergent Alkyne Hydrofluorination Using a Simple Practical Reagent

2020 ◽  
Author(s):  
Rui Guo ◽  
Xiaotian Qi ◽  
Hengye Xiang ◽  
Paul Geaneoates ◽  
Ruihan Wang ◽  
...  
Keyword(s):  
Bond Formation ◽  
Biologically Active ◽  
Dft Studies ◽  
Thermodynamic Control ◽  
Important Goal ◽  
Peptide Bonds ◽  
Metal Free ◽  
Vinyl Cation ◽  
E And Z Isomers ◽  
Vinyl Fluorides

Vinyl fluorides play an important role in drug development as they serve as bioisosteres for peptide bonds and are found in a range of biologically active molecules. The discovery of safe, general and practical procedures to prepare vinyl fluorides remains an important goal and challenge for synthetic chemistry. Here we introduce an inexpensive and easily-handled reagent and report simple, scalable, and metal-free protocols for the regioselective and stereodivergent hydrofluorination of alkynes to access both the E and Z isomers of vinyl fluorides. These conditions were suitable for a diverse collection of alkynes, including several highly-functionalized pharmaceutical derivatives. Mechanistic and DFT studies support C–F bond formation through a vinyl cation intermediate, with the (E)- and (Z)-hydrofluorination products forming under kinetic and thermodynamic control, respectively.<br>

Imine as a Linchpin Approach for Distal C(sp2)–H Functionalization

2020 ◽  
Author(s):  
Sukdev Bag ◽  
Sadhan Jana ◽  
Sukumar Pradhan ◽  
Suman Bhowmick ◽  
Nupur Goswami ◽  
...  
Keyword(s):  
Organic Molecules ◽  
Bond Activation ◽  
Bond Formation ◽  
Ancillary Ligand ◽  
Significant Challenge ◽  
Site Selectivity ◽  
Directing Group ◽  
Covalently Linked ◽  
Complex Organic ◽  
Post Functionalization

<p>Despite the widespread applications of C–H functionalization, controlling site selectivity remains a significant challenge. Covalently attached directing group (DG) served as an ancillary ligand to ensure proximal <i>ortho</i>-, distal <i>meta</i>- and <i>para</i>-C-H functionalization over the last two decades. These covalently linked DGs necessitate two extra steps for a single C–H functionalization: introduction of DG prior to C–H activation and removal of DG post-functionalization. We introduce here a transient directing group for distal C(<i>sp<sup>2</sup></i>)-H functionalization <i>via</i> reversible imine formation. By overruling facile proximal C-H bond activation by imine-<i>N</i> atom, a suitably designed pyrimidine-based transient directing group (TDG) successfully delivered selective distal C-C bond formation. Application of this transient directing group strategy for streamlining the synthesis of complex organic molecules without any necessary pre-functionalization at the distal position has been explored.</p>

Carbon Dioxide-Mediated C(sp2)–H Arylation of Primary and Secondary Benzylamines

2018 ◽  
Author(s):  
Mohit Kapoor ◽  
Pratibha Chand-Thakuri ◽  
Michael Young
Keyword(s):  
Carbon Dioxide ◽  
Transition Metal ◽  
Bond Activation ◽  
Bond Formation ◽  
Carbon Bond ◽  
Chelate Effect ◽  
Free Amine ◽  
Carbon Carbon Bond ◽  
New Strategy ◽  
Metal Catalyzed

Carbon-carbon bond formation by transition metal-catalyzed C–H activation has become an important strategy to fabricate new bonds in a rapid fashion. Despite the pharmacological importance of <i>ortho</i>-arylbenzylamines, however, effective <i>ortho</i>-C–C bond formation from C–H bond activation of free primary and secondary benzylamines using Pd<sup>II</sup> remains an outstanding challenge. Presented herein is a new strategy for constructing <i>ortho</i>-arylated primary and secondary benzylamines mediated by carbon dioxide (CO<sub>2</sub>). The use of CO<sub>2</sub> is critical to allowing this transformation to proceed under milder conditions than previously reported, and that are necessary to furnish free amine products that can be directly used or elaborated without the need for deprotection. In cases where diarylation is possible, a chelate effect is demonstrated to facilitate selective monoarylation.

Radical Capture at Ni(II) Complexes: C-C, C-N, and C-O Bond Formation

2019 ◽  
Author(s):  
Abolghasem (Gus) Bakhoda ◽  
Stefan Wiese ◽  
Christine Greene ◽  
Bryan C. Figula ◽  
Jeffery A. Bertke ◽  
...  
Keyword(s):  
Functional Groups ◽  
Bond Formation ◽  
Dft Studies ◽  
Bond Forming ◽  
Aryl Amines ◽  
Shed Light ◽  
Competing Pathways

<p>The dinuclear b-diketiminato Ni<sup>II</sup><i>tert</i>-butoxide {[Me<sub>3</sub>NN]Ni}<sub>2</sub>(<i>μ</i>-O<i><sup>t</sup></i>Bu)<sub>2 </sub>(<b>2</b>), synthesized from [Me<sub>3</sub>NN]Ni(2,4-lutidine) (<b>1</b>) and di-<i>tert</i>-butylperoxide, is a versatile precursor for the synthesis of a series of Ni<sup>II</sup>complexes [Me<sub>3</sub>NN]Ni-FG to illustrate C-C, C-N, and C-O bond formation at Ni<sup>II </sup>via radicals. {[Me<sub>3</sub>NN]Ni}<sub>2</sub>(<i>μ</i>-O<i><sup>t</sup></i>Bu)<sub>2 </sub>reacts with nitromethane, alkyl and aryl amines, acetophenone, benzamide, ammonia and phenols to deliver corresponding mono- or dinuclear [Me<sub>3</sub>NN]Ni-FG species (FG = O<sub>2</sub>NCH<sub>2</sub>, R-NH, ArNH, PhC(O)NH, PhC(O)CH<sub>2</sub>, NH<sub>2</sub>and OAr). Many of these Ni<sup>II </sup>complexes are capable of capturing the benzylic radical PhCH(•)CH<sub>3 </sub>to deliver corresponding PhCH(FG)CH<sub>3 </sub>products featuring C-C, C-N or C-O bonds. DFT studies shed light on the mechanism of these transformations and suggest two competing pathways that depend on the nature of the functional groups. These radical capture reactions at [Ni<sup>II</sup>]-FG complexes outline key C-C, C-N, and C-O bond forming steps and suggest new families of nickel radical relay catalysts.</p>

Design and Development of Fe-Catalyzed Intra- and Intermolecular Carbofunctionalization of Vinyl Cyclopropanes

2019 ◽  
Author(s):  
Lei Liu ◽  
Wes Lee ◽  
Mingbin Yuan ◽  
Chris Acha ◽  
Michael B. Geherty ◽  
...  
Keyword(s):  
Bond Formation ◽  
Cross Coupling ◽  
Alkyl Halides ◽  
Grignard Reagents ◽  
Mechanistic Studies ◽  
Radical Intermediates ◽  
Design And Implementation ◽  
Solvent Cage ◽  
Radical Cascade ◽  
Radical Processes

Design and implementation of the first (asymmetric) Fe-catalyzed intra- and intermolecular difunctionalization of vinyl cyclopropanes (VCPs) with alkyl halides and aryl Grignard reagents has been realized via a mechanistically driven approach. Mechanistic studies support the diffusion of the alkyl radical intermediates out of the solvent cage to participate in an intra- or -intermolecular radical cascade with the VCP followed by re-entering the Fe radical cross-coupling cycle to undergo selective C(sp2)-C(sp3) bond formation. Overall, we provide new design principles for Fe-mediated radical processes and underscore the potential of using combined computations and experiments to accelerate the development of challenging transformations.

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