scholarly journals Electrochemical Nozaki–Hiyama–Kishi Coupling: Scope, Applications, and Mechanism

2021 ◽  
Author(s):  
Yang Gao ◽  
david hill ◽  
wei hao ◽  
Brendon J. McNicholas ◽  
julien Vantourout ◽  
...  
Keyword(s):  
Cyclic Voltammetry ◽  
Bond Formation ◽  
Active Esters ◽  
Vinyl Halides ◽  
Redox Active ◽  
Chemical Techniques ◽  
Detailed Kinetics ◽  
Limited Scope

One of the most oft-employed methods for C–C bond formation involving the coupling of vinyl-halides with aldehydes catalyzed by Ni and Cr (Nozaki–Hiyama–Kishi, NHK) has been rendered more practical using an electroreductive manifold. Although early studies pointed to the feasibility of such a process those precedents were never applied by others due to cumbersome setups and limited scope. Here we show that a carefully optimized electroreductive procedure can enable a more sustainable approach to NHK, even in an asymmetric fashion on highly complex medicinally relevant systems. The e-NHK can even enable non-canonical substrate classes, such as redox-active esters, to participate with low loadings of Cr when conventional chemical techniques fail. A combination of detailed kinetics, cyclic voltammetry, and in situ UV-vis spectroelectrochemistry of these processes illuminates the subtle features of this mechanistically intricate process.

scholarly journals Electrochemical Nozaki–Hiyama–Kishi Coupling: Scope, Applications, and Mechanism

2021 ◽  
Author(s):  
Yang Gao ◽  
david hill ◽  
wei hao ◽  
Brendon J. McNicholas ◽  
julien Vantourout ◽  
...  
Keyword(s):  
Cyclic Voltammetry ◽  
Bond Formation ◽  
Active Esters ◽  
Vinyl Halides ◽  
Redox Active ◽  
Chemical Techniques ◽  
Detailed Kinetics ◽  
Limited Scope

One of the most oft-employed methods for C–C bond formation involving the coupling of vinyl-halides with aldehydes catalyzed by Ni and Cr (Nozaki–Hiyama–Kishi, NHK) has been rendered more practical using an electroreductive manifold. Although early studies pointed to the feasibility of such a process those precedents were never applied by others due to cumbersome setups and limited scope. Here we show that a carefully optimized electroreductive procedure can enable a more sustainable approach to NHK, even in an asymmetric fashion on highly complex medicinally relevant systems. The e-NHK can even enable non-canonical substrate classes, such as redox-active esters, to participate with low loadings of Cr when conventional chemical techniques fail. A combination of detailed kinetics, cyclic voltammetry, and in situ UV-vis spectroelectrochemistry of these processes illuminates the subtle features of this mechanistically intricate process.

scholarly journals Insight into the template effect of vesicles on the laccase-catalyzed oligomerization of N-phenyl-1,4-phenylenediamine from Raman spectroscopy and cyclic voltammetry measurements

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Aleksandra Janoševic Ležaić ◽  
Sandra Luginbühl ◽  
Danica Bajuk-Bogdanović ◽  
Igor Pašti ◽  
Reinhard Kissner ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Cyclic Voltammetry ◽  
Redox Activity ◽  
Salt Form ◽  
Template Effect ◽  
Structural Units ◽  
Redox Active ◽  
First Time ◽  
Insight Into

Abstract We report about the first Raman spectroscopy study of a vesicle-assisted enzyme-catalyzed oligomerization reaction. The aniline dimer N-phenyl-1,4-phenylenediamine (= p-aminodiphenylamine, PADPA) was oxidized and oligomerized with Trametes versicolor laccase and dissolved O2 in the presence of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) vesicles (80–100 nm diameter) as templates. The conversion of PADPA into oligomeric products, poly(PADPA), was monitored during the reaction by in situ Raman spectroscopy. The results obtained are compared with UV/vis/NIR and EPR measurements. All three complementary methods indicate that at least some of the poly(PADPA) products, formed in the presence of AOT vesicles, resemble the conductive emeraldine salt form of polyaniline (PANI-ES). The Raman measurements also show that structural units different from those of “ordinary” PANI-ES are present too. Without vesicles PANI-ES-like products are not obtained. For the first time, the as-prepared stable poly(PADPA)-AOT vesicle suspension was used directly to coat electrodes (without product isolation) for investigating redox activities of poly(PADPA) by cyclic voltammetry (CV). CV showed that poly(PADPA) produced with vesicles is redox active not only at pH 1.1–as expected for PANI-ES–but also at pH 6.0, unlike PANI-ES and poly(PADPA) synthesized without vesicles. This extended pH range of the redox activity of poly(PADPA) is important for applications.

scholarly journals Copper-catalysed photoinduced decarboxylative alkynylation: a combined experimental and computational study

2020 ◽  
Vol 11 (19) ◽  
pp. 4939-4947 ◽  
Author(s):  
Yu Mao ◽  
Wenxuan Zhao ◽  
Shuo Lu ◽  
Lei Yu ◽  
Yi Wang ◽  
...  
Keyword(s):  
Alkyl Radical ◽  
Computational Study ◽  
Bond Formation ◽  
Active Esters ◽  
Redox Active

Redox-active esters (RAEs) as alkyl radical precursors have demonstrated great advantages for Cu-catalysed C–C bond formation.

scholarly journals Decarboxylative thiolation of redox-active esters to free thiols and further diversification

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Tianpeng Cao ◽  
Tianxiao Xu ◽  
Ruting Xu ◽  
Xianli Shu ◽  
Saihu Liao
Keyword(s):  
Natural Products ◽  
Carboxylic Acid ◽  
Visible Light ◽  
High Efficiency ◽  
Direct Access ◽  
Active Esters ◽  
Redox Active ◽  
Sulfur Containing ◽  
Sulfur Containing Compounds

Abstract Thiols are important precursors for the synthesis of a variety of pharmaceutically important sulfur-containing compounds. In view of the versatile reactivity of free thiols, here we report the development of a visible light-mediated direct decarboxylative thiolation reaction of alkyl redox-active esters to free thiols based on the abundant carboxylic acid feedstock. This transformation is applicable to various carboxylic acids, including primary, secondary, and tertiary acids as well as natural products and drugs, forging a general and facile access to free thiols with diverse structures. Moreover, the direct access to free thiols affords an advantage of rapid in situ diversification with high efficiency to other important thiol derivatives such as sulfide, disulfide, thiocyanide, thioselenide, etc.

scholarly journals Ni-Electrocatalytic C(sp3)–C(sp3) Doubly Decarboxylative Coupling

2021 ◽  
Author(s):  
benxiang zhang ◽  
yang gao ◽  
yuta hioki ◽  
martins oderinde ◽  
jennifer qiao ◽  
...  
Keyword(s):  
Organic Synthesis ◽  
Present Method ◽  
Bond Formation ◽  
Amide Bond ◽  
Bond Forming ◽  
Amide Bond Formation ◽  
Redox Active ◽  
Decarboxylative Coupling ◽  
The 19Th Century

This work presents a modern spin on one of the oldest known Csp3–Csp3 bond forming reactions in synthetic chemistry: the Kolbe electrolysis. This reaction holds incredible promise for synthesis, yet its use has been near non-existent in mainstream organic synthesis. In contrast to the strongly oxidative electrolytic protocol employed traditionally since the 19th century, the present method utilizes in situ generated redox-active esters (RAEs) which are combined with a mildly reductive Ni-electrocatalytic cycle. It can be used to heterocouple 1o, 2o, and even certain 3o RAEs with a protocol reminiscent of amide bond formation in terms of simplicity. Due to its mild nature the reaction tolerates a range of functional groups, is scalable, and was strategically enlisted for the synthesis of 25 known compounds to reduce overall step-counts by 74%.

scholarly journals A cross-dehydrogenative C(sp3)−H heteroarylation via photo-induced catalytic chlorine radical generation

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Chia-Yu Huang ◽  
Jianbin Li ◽  
Chao-Jun Li
Keyword(s):  
Hydrogen Atom ◽  
Hydrogen Evolution ◽  
Alkyl Radical ◽  
Cobalt Catalyst ◽  
Alkylation Reaction ◽  
Hydrogen Atom Abstraction ◽  
Dehydrogenative Coupling ◽  
Radical Generation ◽  
Limited Scope

AbstractHydrogen atom abstraction (HAT) from C(sp3)–H bonds of naturally abundant alkanes for alkyl radical generation represents a promising yet underexplored strategy in the alkylation reaction designs since involving stoichiometric oxidants, excessive alkane loading, and limited scope are common drawbacks. Here we report a photo-induced and chemical oxidant-free cross-dehydrogenative coupling (CDC) between alkanes and heteroarenes using catalytic chloride and cobalt catalyst. Couplings of strong C(sp3)–H bond-containing substrates and complex heteroarenes, have been achieved with satisfactory yields. This dual catalytic platform features the in situ engendered chlorine radical for alkyl radical generation and exploits the cobaloxime catalyst to enable the hydrogen evolution for catalytic turnover. The practical value of this protocol was demonstrated by the gram-scale synthesis of alkylated heteroarene with merely 3 equiv. alkane loading.

scholarly journals Bioelectrocatalytic cofactor regeneration coupled to CO2 fixation in a redox‐active hydrogel for stereoselective C‐C bond formation

2021 ◽  
Author(s):  
Leonardo Castañeda-Losada ◽  
David Adam ◽  
Nicole Paczia ◽  
Darren Buesen ◽  
Fabian Steffler ◽  
...  
Keyword(s):  
Co2 Fixation ◽  
Bond Formation ◽  
Cofactor Regeneration ◽  
Redox Active
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