scholarly journals Synthesis of 2-C-Branched Sugars

2021 ◽  
Author(s):  
◽  
Peter William Moore
Keyword(s):  
Allyl Alcohol ◽  
Ring Opening ◽  
Cyclopropane Ring ◽  
Cross Coupling ◽  
Coupling Reactions ◽  
Deuterium Labelling ◽  
Cross Coupling Reactions ◽  
Initial Work ◽  
Acidic Conditions

<p>A range of unnatural carbohydrates (sugars) with an unusual 2-C-bromomethylene branch have been synthesised by reaction of the 1,2-cyclopropanated carbohydrate 52 with different nucleophiles. Initial work to optimise the cyclopropane ring opening in the presence of sodium allyloxide/allyl alcohol provided anomers 140 and 141 in up to 75% yield. Use of sodium thiophenolate/thiophenol provided anomeric thioglycosides 181 and 182 (76% yield, 7:2 ratio), while sodium diethylamide/ diethylamine provided anomeric glycosylamines 183 and 184 (50% yield, 1:1 ratio). Further functionalisation of the 2-C-branch of 141 was performed using various palladium-catalysed cross-coupling reactions, providing a series of products. Reaction of 140 and 141 under acidic conditions caused E-Z isomerisation of the bromoalkene forming a single anomer, 194. Efforts to obtain mechanistic information about the cyclopropane ring opening were made through attempted trapping of a cyclopropene intermediate, deuterium labelling experiments, synthesis of possible stable intermediates and reactions with internal nucleophiles.</p>

scholarly journals Synthesis of 2-C-Branched Sugars

2021 ◽  
Author(s):  
◽  
Peter William Moore
Keyword(s):  
Allyl Alcohol ◽  
Ring Opening ◽  
Cyclopropane Ring ◽  
Cross Coupling ◽  
Coupling Reactions ◽  
Deuterium Labelling ◽  
Cross Coupling Reactions ◽  
Initial Work ◽  
Acidic Conditions

<p>A range of unnatural carbohydrates (sugars) with an unusual 2-C-bromomethylene branch have been synthesised by reaction of the 1,2-cyclopropanated carbohydrate 52 with different nucleophiles. Initial work to optimise the cyclopropane ring opening in the presence of sodium allyloxide/allyl alcohol provided anomers 140 and 141 in up to 75% yield. Use of sodium thiophenolate/thiophenol provided anomeric thioglycosides 181 and 182 (76% yield, 7:2 ratio), while sodium diethylamide/ diethylamine provided anomeric glycosylamines 183 and 184 (50% yield, 1:1 ratio). Further functionalisation of the 2-C-branch of 141 was performed using various palladium-catalysed cross-coupling reactions, providing a series of products. Reaction of 140 and 141 under acidic conditions caused E-Z isomerisation of the bromoalkene forming a single anomer, 194. Efforts to obtain mechanistic information about the cyclopropane ring opening were made through attempted trapping of a cyclopropene intermediate, deuterium labelling experiments, synthesis of possible stable intermediates and reactions with internal nucleophiles.</p>

Pd-Catalyzed Ring-Closing/Ring-Opening Cross Coupling Reactions: Enantioselective Diarylation of Unactivated Olefins

ACS Catalysis ◽  
2021 ◽  
pp. 8942-8947
Author(s):  
Lantao Liu ◽  
Fangyuan Cheng ◽  
Chenxiang Meng ◽  
An-An Zhang ◽  
Mingliang Zhang ◽  
...  
Keyword(s):  
Ring Opening ◽  
Cross Coupling ◽  
Coupling Reactions ◽  
Cross Coupling Reactions

Dual Nickel/Palladium-Catalyzed Reductive Cross-Coupling Reactions Between Two Phenol Derivatives

2020 ◽  
Author(s):  
Baojian Xiong ◽  
Yue Li ◽  
Yin Wei ◽  
Søren Kramer ◽  
Zhong Lian
Keyword(s):  
Functional Group ◽  
Low Cost ◽  
Cross Coupling ◽  
Coupling Reactions ◽  
Phenol Derivatives ◽  
Cross Coupling Reactions ◽  
Palladium Catalyzed ◽  
One Step ◽  
Aryl Tosylates ◽  
Low Sensitivity

Cross-coupling between substrates that can be easily derived from phenols is highly attractive due to the abundance and low cost of phenols. Here, we report a dual nickel/palladium-catalyzed reductive cross-coupling between aryl tosylates and aryl triflates; both substrates can be accessed in just one step from readily available phenols. The reaction has a broad functional group tolerance and substrate scope (>60 examples). Furthermore, it displays low sensitivity to steric effects demonstrated by the synthesis of a 2,2’disubstituted biaryl and a fully substituted aryl product. The widespread presence of phenols in natural products and pharmaceuticals allow for straightforward late-stage functionalization, illustrated with examples such as Ezetimibe and tyrosine. NMR spectroscopy and DFT calculations indicate that the nickel catalyst is responsible for activating the aryl triflate, while the palladium catalyst preferentially reacts with the aryl tosylate.

An Iron-Based Catalyst Enables The Enantioconvergent Synthesis of Chiral 1,1-Diarylalkanes Through a Suzuki-Miyaura Cross-Coupling Reaction

2020 ◽  
Author(s):  
Chet Tyrol ◽  
Nang Yone ◽  
Connor Gallin ◽  
Jeffery Byers
Keyword(s):  
Coupling Reaction ◽  
Cross Coupling ◽  
Coupling Reactions ◽  
Radical Intermediates ◽  
Cross Coupling Reactions ◽  
Cross Coupling Reaction ◽  
Boronic Esters ◽  
Carbon Centered Radical ◽  
Iron Based ◽  
High Yields

By using an iron-based catalyst, access to enantioenriched 1,1-diarylakanes was enabled through an enantioselective Suzuki-Miyaura crosscoupling reaction. The combination of a chiral cyanobis(oxazoline) ligand framework and 1,3,5-trimethoxybenzene additive were essential to afford high yields and enantioselectivities in cross-coupling reactions between unactivated aryl boronic esters and a variety of benzylic chlorides, including challenging ortho-substituted benzylic chloride substrates. Mechanistic investigations implicate a stereoconvergent pathway involving carbon-centered radical intermediates.

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