scholarly journals Lewis Acid-Activated 8-Quinolinethiosulfonates: An Efficient Methodology for CS(alkyl) Bond Formation

2020 ◽  
Author(s):  
erwan galardon
Keyword(s):  
Lewis Acid ◽  
Bond Formation ◽  
The Other ◽  
Sulfinic Acid ◽  
Metal Free ◽  
Noble Metal Catalysts ◽  
Large Pool ◽  
Metal Catalyzed ◽  
Sulfur Containing ◽  
Sulfur Containing Compounds

The importance of sulfur-containing compounds in various fields, ranging from material science1-2 to medicinal chemistry, 3 has called for the development of synthetic strategies to form carbon-sulfur (C-S) bonds. Thus, numerous approaches based on the nucleophilicity of thiols have been designed over the years, which mostly use air-sensitive noble metal catalysts.4- 9 At the opposite, the use of electrophilic sulfur reagents is also a powerful, more eco-friendly approach, in particular for the sulfenylation of C-H bonds into C-S bonds.10-11 In this context, the sulfenylation of indoles (Equation 1) has become a benchmark reaction to develop and test new sulfenyl transfer reagents, because indoles are good nucleophiles and their occurrence in many natural products or biological active compounds makes them attractive synthetic targets.12-14 For instance, metal-catalyzed or metal-free protocols have been proposed, in which disulfides, sulfinic acid and their salts, sulfonyl chlorides, sulfonylhydrazine, or Nthiophtalimides are used as source of electrophilic sulfur.10,15-16 Thiosulfonates (RSO2SR’) are another class of emerging17 reagents, which were also studied for C-S bond formation18-20 and for indole sulfenylation.21 However, despite the large pool of sulfenylation agents listed above, the difficult activation of the chalcogen centre essentially limits these reagents to the formation of C-S(aryl) bonds. On the other hand, the transfer of alkylsulfenyl groups requires harsher activating conditions and is so far still limited<br>

scholarly journals Efficient C3-alkylsulfenylation of indoles under mild conditions using Lewis acid-activated 8-quinolinethiosulfonates.

2020 ◽  
Author(s):  
erwan galardon
Keyword(s):  
Lewis Acid ◽  
The Other ◽  
Sulfinic Acid ◽  
Metal Free ◽  
Noble Metal Catalysts ◽  
Mild Conditions ◽  
Large Pool ◽  
Metal Catalyzed ◽  
Sulfur Containing ◽  
Sulfur Containing Compounds

The importance of sulfur-containing compounds in various fields, ranging from material science1-2 to medicinal chemistry, 3 has called for the development of synthetic strategies to form carbon-sulfur (C-S) bonds. Thus, numerous approaches based on the nucleophilicity of thiols have been designed over the years, which mostly use air-sensitive noble metal catalysts.4- 9 At the opposite, the use of electrophilic sulfur reagents is also a powerful, more eco-friendly approach, in particular for the sulfenylation of C-H bonds into C-S bonds.10-11 In this context, the sulfenylation of indoles (Equation 1) has become a benchmark reaction to develop and test new sulfenyl transfer reagents, because indoles are good nucleophiles and their occurrence in many natural products or biological active compounds makes them attractive synthetic targets.12-14 For instance, metal-catalyzed or metal-free protocols have been proposed, in which disulfides, sulfinic acid and their salts, sulfonyl chlorides, sulfonylhydrazine, or Nthiophtalimides are used as source of electrophilic sulfur.10,15-16 Thiosulfonates (RSO2SR’) are another class of emerging17 reagents, which were also studied for C-S bond formation18-20 and for indole sulfenylation.21 However, despite the large pool of sulfenylation agents listed above, the difficult activation of the chalcogen centre essentially limits these reagents to the formation of C-S(aryl) bonds. On the other hand, the transfer of alkylsulfenyl groups requires harsher activating conditions and is so far still limited<br>

scholarly journals Efficient C3-alkylsulfenylation of indoles under mild conditions using Lewis acid-activated 8-quinolinethiosulfonates.

2020 ◽  
Author(s):  
erwan galardon
Keyword(s):  
Lewis Acid ◽  
The Other ◽  
Sulfinic Acid ◽  
Metal Free ◽  
Noble Metal Catalysts ◽  
Mild Conditions ◽  
Large Pool ◽  
Metal Catalyzed ◽  
Sulfur Containing ◽  
Sulfur Containing Compounds

The importance of sulfur-containing compounds in various fields, ranging from material science1-2 to medicinal chemistry, 3 has called for the development of synthetic strategies to form carbon-sulfur (C-S) bonds. Thus, numerous approaches based on the nucleophilicity of thiols have been designed over the years, which mostly use air-sensitive noble metal catalysts.4- 9 At the opposite, the use of electrophilic sulfur reagents is also a powerful, more eco-friendly approach, in particular for the sulfenylation of C-H bonds into C-S bonds.10-11 In this context, the sulfenylation of indoles (Equation 1) has become a benchmark reaction to develop and test new sulfenyl transfer reagents, because indoles are good nucleophiles and their occurrence in many natural products or biological active compounds makes them attractive synthetic targets.12-14 For instance, metal-catalyzed or metal-free protocols have been proposed, in which disulfides, sulfinic acid and their salts, sulfonyl chlorides, sulfonylhydrazine, or Nthiophtalimides are used as source of electrophilic sulfur.10,15-16 Thiosulfonates (RSO2SR’) are another class of emerging17 reagents, which were also studied for C-S bond formation18-20 and for indole sulfenylation.21 However, despite the large pool of sulfenylation agents listed above, the difficult activation of the chalcogen centre essentially limits these reagents to the formation of C-S(aryl) bonds. On the other hand, the transfer of alkylsulfenyl groups requires harsher activating conditions and is so far still limited<br>

scholarly journals The renaissance of alkali metabisulfites as SO2 surrogate

SynOpen ◽  
2021 ◽  
Author(s):  
Bhisma Patel ◽  
Ashish Kumar Sahoo ◽  
Anjali Dahiya ◽  
Amitava Rakshit
Keyword(s):  
Organic Chemistry ◽  
Sulfur Dioxide ◽  
Transition Metal ◽  
Visible Light ◽  
Metal Free ◽  
Biological Relevance ◽  
Current Review ◽  
Metal Catalyzed ◽  
Sulfur Containing ◽  
Sulfur Containing Compounds

The upsurge of interest in the development of methodologies for the construction of sulfur-containing compounds via the use of expedient reagents has been established as sustainable tools in organic chemistry. This review focuses on the sulfonylation reactions using inorganic sulfites (Na2S2O5 or K2S2O5) as the sulfur dioxide surrogate. Unlike bis-adduct of DABCO, which is an excellent surrogate of the gaseous SO2, the use of sodium or potassium metabisulfites as SO2 surrogates are equally efficient. The objective of the current review is to bring out the latest collection of sulfonylation reactions using inorganic sulfites. For better understanding, the review is categorized according to the mode of reactions viz., transition metal-catalyzed SO2 insertion, metal-free SO2 insertion, and visible light-mediated SO2 insertion. All the reactions in each of the sections are depicted with selected examples with a pertinent explanation of the proposed mechanism. Nevertheless, based on the biological relevance of sulfonylated compounds the use of inorganic sulfites as the SO2 source in various sulfonylation reactions are needed to be explored.

A Review on Sulfur-Directed C−H Bond Activation

2020 ◽  
Vol 17 ◽  
Author(s):  
Xuchong Tang ◽  
Yingwei Zhao
Keyword(s):  
Transition Metal ◽  
Electron Donor ◽  
Bond Activation ◽  
Bond Formation ◽  
Metal Catalysts ◽  
Transition Metal Catalysts ◽  
Directing Group ◽  
Metal Catalyzed ◽  
Sulfur Containing

: Transition-metal-catalyzed C−H bond activation employing a directing group is becoming a powerful tool to access C−C or C−hetero bond formation. Oxygen and nitrogen atoms are commonly applied as the electron donor for these directing groups. In contrast, there are only few studies on sulfur-containing groups, probably due to their toxicity to transition-metal catalysts. Nowadays a large amount of C−H activation reactions directed by sulfur-containing auxiliary groups have been successfully achieved. Because these groups can be facilely removed or modified in situ or in further steps, they are of great value in creative synthetic strategies. This paper reviews recent advances in the studies using thioether, thiol/thiophenol/disulfide, sulfoxide, and thiocarbonyl as directing groups for intermolecular C−H functionalizations as well as intramolecular oxidative annulations.

Developments in Organocatalyzed C(Ar)- C(Ar) Bond formation Reactions via Single Electron Transfer Mechanism: An Overview

2021 ◽  
Vol 08 ◽  
Author(s):  
Lalit Yadav ◽  
Sandeep Chaudhary
Keyword(s):  
Transition Metal ◽  
Organic Synthesis ◽  
Bond Activation ◽  
Bond Formation ◽  
Cross Coupling ◽  
Coupling Reactions ◽  
Metal Free ◽  
Cross Coupling Reactions ◽  
Transition Metal Catalyzed ◽  
Metal Catalyzed

: The formation of new bonds through C-C bond formation is of utmost importance in the synthesis of biologically privileged scaffolds and therapeutic drugs. In recent years, extensive efforts has been done to improve the intermolecular and intramolecular cross-coupling reaction in the simple, mild, efficient, economical, and eco-friendly manner via transition metal-free or organocatalytic direct C-H bond activation methodology. The traditional crosscoupling era continuously shifted to metal-free, organocatalytic, or metal-free cross-dehydrogenative coupling strategies to fast-track the reactions and diminishing the typical purification processes. Therefore, recent advances on the transitionmetal-free, organocatalytic inter- and intra-molecular cross-coupling reactions have been introduced and discussed in the present article. In view of the reaction mechanism, organocatalytic cross-coupling reactions undergo through the radical pathways, radical anionic intermediate which is completely different from traditional transition metal-catalyzed reactions. The exploration of transition metal-free organocatalyzed cross-couplings for direct C-H arylation of arenes has grown significantly, thereby, improving the formation of a wide range of aryl-aryl /aryl-heteroaryl/ heteroaryl-heteroaryl compounds. In the survey, transition metal-free/organocatalytic cross-coupling reactions showed a higher efficiency under simple and mild conditions than the comparative transition metal-catalyzed cross-coupling reactions. However, the higher regioselectivity and chemoselectivity are still far ahead in organocatalytic cross-coupling reactions due to their specific intrinsic mechanistic pathway. The tuning of many parameters such as oxidative states, ligands coordination, and counter anions, etc., which results in the specific direct C-H functionalization with flexible methodology are missing in the transition metal-free cross-coupling reactions. The highly systematic transition metal-catalyzed chemistry is still playing a dominant role over transition metal-free chemistry in organic synthesis. The organocatalyzed transition-metal-free conditions should be more efficient, chemoselective, and regioselective for further potential development and applications in organic synthesis. For the endless pursuit of sustainable chemistry and green chemistry, such transition-metalfree/organocatalytic reactions should be never ceased. Additional curious attention and interest have been developed so far, and chemists are showing their eagerness and talents to uncover the hidden treasure of green chemistry. In this review article, we highlighted the developments of various transition metal-free/organocatalytic C-H bond activation reactions which further encourages the advancement in the development of sustainable C-C coupling reactions and their further applications towards the synthesis of biologically privileged scaffolds and drug 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>

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.

p-Sulfonic acid calix[n]arene catalyzed synthesis of bioactive heterocycles: A review

2020 ◽  
Vol 24 ◽  
Author(s):  
Bubun Banerjee ◽  
Gurpreet Kaur ◽  
Navdeep Kaur
Keyword(s):  
Supramolecular Chemistry ◽  
Sulfonic Acid ◽  
Catalytic Efficiency ◽  
The Other ◽  
Reaction Conditions ◽  
Metal Free ◽  
Bioactive Scaffolds ◽  
Wide Range ◽  
Efficient Alternative ◽  
Bioactive Heterocycles

: Metal-free organocatalysts are becoming an important tool for the sustainable developments of various bioactive heterocycles. On the other hand, during last two decades, calix[n]arenes have been gaining considerable attention due to their wide range of applicability in the field of supramolecular chemistry. Recently, sulfonic acid functionalized calix[n] arenes are being employed as an efficient alternative catalyst for the synthesis of various bioactive scaffolds. In this review we have summarized the catalytic efficiency of p-sulfonic acid calix[n]arenes for the synthesis of diverse biologically promising scaffolds under various reaction conditions. There is no such review available in the literature showing the catalytic applicability of p-sulfonic acid calix[n]arenes. Therefore, we strongly believe that this review will surely attract those researchers who are interested about this fascinating organocatalyst.

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