scholarly journals Redox-enabled direct stereoconvergent heteroarylation of simple alcohols

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yongbing Liu ◽  
Ran Tao ◽  
Zhi-Keng Lin ◽  
Guoqiang Yang ◽  
Yu Zhao
Keyword(s):  
Catalytic Reduction ◽  
High Yield ◽  
Radical Mechanism ◽  
Waste Generation ◽  
Direct Transformation ◽  
Bond Forming ◽  
Carbon Carbon Bond ◽  
Chiral Phosphoric Acid ◽  
Wide Range ◽  
Leaving Group

AbstractThe direct transformation of racemic feedstock materials to valuable enantiopure compounds is of significant importance for sustainable chemical synthesis. Toward this goal, the radical mechanism has proven uniquely effective in stereoconvergent carbon-carbon bond forming reactions. Here we report a mechanistically distinct redox-enabled strategy for an efficient enantioconvergent coupling of pyrroles with simple racemic secondary alcohols. In such processes, chirality is removed from the substrate via dehydrogenation and reinstalled in the catalytic reduction of a key stabilized cationic intermediate. This strategy provides significant advantage of utilizing simple pyrroles to react with feedstock alcohols without the need for leaving group incorporation. This overall redox-neutral transformation is also highly economical with no additional reagent nor waste generation other than water. In our studies, oxime-derived iridacycle complexes are introduced, which cooperate with a chiral phosphoric acid to enable heteroarylation of alcohols, accessing a wide range of valuable substituted pyrroles in high yield and enantioselectivity.

Nickel-Catalyzed Electronically-Reversed Enantioselective Hydrocarbofunctionalizations of Acrylamides

Synlett ◽  
2021 ◽  
Author(s):  
Lou Shi ◽  
Wei Shu
Keyword(s):  
Nickel Catalyst ◽  
Functional Group ◽  
Optically Active ◽  
Forming Process ◽  
Carbon Bond ◽  
Bond Forming ◽  
Synthetic Strategy ◽  
Carbon Carbon Bond ◽  
Wide Range ◽  
Simple Protocol

Asymmetric hydrocarbofunctionalizations of alkenes has emerged as an efficient synthetic strategy for accessing optically active molecules via carbon-carbon bond-forming process from readily available alkenes and carbo-electrophiles. Herein, we present a summary of the efforts from our group to control the regio- and enantioselectivity of hydrocarbofunctionalizations of electron-deficient alkenes with a nickel catalyst and chiral bisoxazolidine ligand. The reaction undergoes electron-reversed hydrocarbofunctionalizations acrylamides with excellent enantioselectivity. This operationally simple protocol enables the asymmetric hydroalkylation, hydrobenzylation and hydropropargylation of acrylamides. This reaction is useful for preparing a wide range of α-branched chiral amides with broad functional group tolerance.

scholarly journals Recoverable Palladium-Catalyzed Carbon-Carbon Bond Forming Reactions Under Thermomorphic Mode: Stille and Suzuki-Miyaura Reactions

Molecules ◽  
2021 ◽  
Vol 26 (5) ◽  
pp. 1414
Author(s):  
Eskedar Tessema ◽  
Vijayanath Elakkat ◽  
Chiao-Fan Chiu ◽  
Zong-Lin Tsai ◽  
Ka Long Chan ◽  
...  
Keyword(s):  
Electronic Effect ◽  
Aryl Halide ◽  
Phenylboronic Acid ◽  
Gas Chromatography Mass Spectrometry ◽  
High Yield ◽  
Coupling Reactions ◽  
Bond Forming ◽  
Carbon Carbon Bond ◽  
Short Period ◽  
Palladium Catalyzed

The reaction of [PdCl2(CH3CN)2] and bis-4,4’-(RfCH2OCH2)-2,2’-bpy (1a–d), where Rf = n-C11F23 (a), n-C10F21 (b), n-C9F19 (c) and n-C8F17 (d), respectively, in the presence of dichloromethane (CH2Cl2) resulted in the synthesis of Pd complex, [PdCl2[4,4’-bis-(RfCH2OCH2)-2,2’-bpy] (2a–d). The Pd-catalyzed Stille arylations of vinyl tributyltin with aryl halides were selected to demonstrate the feasibility of recycling usage with 2a as the catalyst using NMP (N-methyl-2-pyrrolidone) as the solvent at 120–150 °C. Additionally, recycling and electronic effect studies of 2a–c were also carried out for Suzuki-Miyaura reaction of phenylboronic acid derivatives, 4-X-C6H4-B(OH)2, (X = H or Ph) with aryl halide, 4-Y-C6H4-Z, (Y = CN, H or OCH3; Z = I or Br) in dimethylformamide (DMF) at 135–150 °C. At the end of each cycle, the product mixtures were cooled to lower temperature (e.g., −10 °C), and then catalysts were recovered by decantation with Pd leaching less than 1%. The products were quantified by gas chromatography/mass spectrometry (GC/MS) analysis or by the isolated yield. The complex 2a-catalyzed Stille reaction of aryl iodides with vinyl tributyltin have good recycling results for a total of 8 times, with a high yield within short period of time (1–3 h). Similarly, 2a–c-catalyzed Suzuki-Miyaura reactions also have good recycling results. The electronic effect studies from substituents in both Stille and Suzuki-Miyaura coupling reactions showed that electron withdrawing groups speed up the reaction rate. To our knowledge, this is the first example of recoverable fluorous long-chained Pd-catalyzed Stille reactions under the thermomorphic mode.

Facile Synthesis of a Diverse Library of Mono-3-substituted β-Cyclodextrin Analogues

2018 ◽  
Author(s):  
Kathryn Kellett ◽  
Brendan M. Duggan ◽  
Michael Gilson
Keyword(s):  
High Yield ◽  
Facile Synthesis ◽  
Wide Range

We have described simple, high-yield, protocols, which require only commonly accessible equipment, to synthesize a wide range of β-CD derivatives mono-substituted at the secondary face. These derivatives may be useful in their own right, and they are also scaffolds for further modification, and examples of the far broader array of derivatives that may be accessed by these procedures.

Visible-Light Photosensitized Aryl and Alkyl Decarboxylative Carbon-Heteroatom and Carbon-Carbon Bond Formations

2019 ◽  
Author(s):  
Tuhin Patra ◽  
Satobhisha Mukherjee ◽  
Jiajia Ma ◽  
Felix Strieth-Kalthoff ◽  
Frank Glorius
Keyword(s):  
Energy Transfer ◽  
Visible Light ◽  
Alkyl Radical ◽  
General Strategy ◽  
Alkyl Radicals ◽  
Bond Forming ◽  
Radical Trapping ◽  
Carbon Carbon Bond ◽  
Radical Generation ◽  
Trapping Agent

<sub>A general strategy to access both aryl and alkyl radicals by photosensitized decarboxylation of the corresponding carboxylic acids esters has been developed. An energy transfer mediated homolysis of unsymmetrical sigma-bonds for a concerted fragmentation/decarboxylation process is involved. As a result, an independent aryl/alkyl radical generation step enables a series of key C-X and C-C bond forming reactions by simply changing the radical trapping agent.</sub>

General Cyclopropane Assembly via Enantioselective Redox-Active Carbene Transfer to Aliphatic Olefins

2018 ◽  
Author(s):  
Marc Montesinos-Magraner ◽  
Matteo Costantini ◽  
Rodrigo Ramirez-Contreras ◽  
Michael E. Muratore ◽  
Magnus J. Johansson ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Asymmetric Synthesis ◽  
Chemical Space ◽  
Synthetic Approach ◽  
Asymmetric Cyclopropanation ◽  
Redox Active ◽  
Wide Range ◽  
Leaving Group ◽  
Stereoelectronic Properties ◽  
Carbene Transfer

Asymmetric cyclopropane synthesis currently requires bespoke strategies, methods, substrates and reagents, even when targeting similar compounds. This limits the speed and chemical space available for discovery campaigns. Here we introduce a practical and versatile diazocompound, and we demonstrate its performance in the first unified asymmetric synthesis of functionalized cyclopropanes. We found that the redox-active leaving group in this reagent enhances the reactivity and selectivity of geminal carbene transfer. This effect enabled the asymmetric cyclopropanation of a wide range of olefins including unactivated aliphatic alkenes, enabling the 3-step total synthesis of (–)-dictyopterene A. This unified synthetic approach delivers high enantioselectivities that are independent of the stereoelectronic properties of the functional groups transferred. Our results demonstrate that orthogonally-differentiated diazocompounds are viable and advantageous equivalents of single-carbon chirons<i>.</i>

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