scholarly journals Development of enantioselective intramolecular N-arylation reactions for the desymmetrization of achiral dinitrogen malonamide derivatives

2021 ◽  
Author(s):  
Lukasz Porosa
Keyword(s):  
Good Yield ◽  
Enantiomeric Excess ◽  
Quantitative Yield

An effective methodology for the enantioselective intramolecular (Buchwald-Hartwig) amidation of prochiral dinitrogen malonamide derivatives has been developed in quantitative yield and good enantioselectivities. The best result was obtained based on an enantiopure (R)-MOP/Pd(OAc)₂ catalytst system with either Cs₂CO₃ or K₃PO₄ in refluxing THF affording the 4-methoxybenzyl substituted diamide derivative, 3-methyl-N, 1-bis(4-methoxbenzyl)-2-oxo-1,2,3,4-tetrahydroquinoline-3-carboxamide, in 99% yield and 75% enantiomeric excess. This example serves as a preliminary example of a desymmetrization of prochiral dinitrogen nucleophiles by preferential N-arylation. The intermolecular version of this reaction proved to be more challenging than its intramolecular counterpart and no coupling products were obtained. Other malonamide derivatives were prepared with a pendant bromovinyl substituent at the αposition and cyclized intramoleculary employing a mild Goldberg reaction to form 5-membered rings in good yield and unknown enantioselectivity.

scholarly journals Development of enantioselective intramolecular N-arylation reactions for the desymmetrization of achiral dinitrogen malonamide derivatives

2021 ◽  
Author(s):  
Lukasz Porosa
Keyword(s):  
Good Yield ◽  
Enantiomeric Excess ◽  
Quantitative Yield

An effective methodology for the enantioselective intramolecular (Buchwald-Hartwig) amidation of prochiral dinitrogen malonamide derivatives has been developed in quantitative yield and good enantioselectivities. The best result was obtained based on an enantiopure (R)-MOP/Pd(OAc)₂ catalytst system with either Cs₂CO₃ or K₃PO₄ in refluxing THF affording the 4-methoxybenzyl substituted diamide derivative, 3-methyl-N, 1-bis(4-methoxbenzyl)-2-oxo-1,2,3,4-tetrahydroquinoline-3-carboxamide, in 99% yield and 75% enantiomeric excess. This example serves as a preliminary example of a desymmetrization of prochiral dinitrogen nucleophiles by preferential N-arylation. The intermolecular version of this reaction proved to be more challenging than its intramolecular counterpart and no coupling products were obtained. Other malonamide derivatives were prepared with a pendant bromovinyl substituent at the αposition and cyclized intramoleculary employing a mild Goldberg reaction to form 5-membered rings in good yield and unknown enantioselectivity.

Syntheses of 1,2-Amino Alcohols and Their Applications for Oxazaborolidine Catalyzed Enantioselective Reduction of Aromatic Ketones

2007 ◽  
Vol 60 (3) ◽  
pp. 196 ◽  
Author(s):  
Namdev S. Vatmurge ◽  
Braja G. Hazra ◽  
Vandana S. Pore
Keyword(s):  
Amino Alcohol ◽  
Good Yield ◽  
Asymmetric Reduction ◽  
Enantiomeric Excess ◽  
Amino Alcohols ◽  
Secondary Alcohols ◽  
Aromatic Ketones ◽  
Enantioselective Reduction ◽  
Aryl Ketones

Six new chiral 1,2-amino alcohol derivatives have been synthesized starting from (1R,2R)-2-amino-1-phenylpropane-1,3-diol. Asymmetric reduction of aryl ketones with in-situ generated oxazaborolidine from these amino alcohol derivatives and BH3·Me2S afforded secondary alcohols with good yield and moderate to high enantiomeric excess.

t-Butyldimethylsilyl ethers of sucrose

1977 ◽  
Vol 30 (3) ◽  
pp. 639 ◽  
Author(s):  
F Franke ◽  
RD Guthrie
Keyword(s):  
Good Yield ◽  
Quantitative Yield ◽  
Hydroxyl Groups ◽  
Carbohydrate Chemistry ◽  
Blocking Group ◽  
Primary Hydroxyl ◽  
Derivatives Of

The usefulness of the t-butyldimethylsilyl group as a blocking group in carbohydrate chemistry has been demonstrated and its selectivity towards primary hydroxyl groups, in the absence of imidazole, shown by preparation of derivatives of methyl α-D-glucopyranoside and sucrose. Methyl α-D-gluco-pyranoside was converted into methyl 6-O-t- butyldimethylsilyl-a-D-glucopyranoside in almost quantitative yield, and sucrose to 6,1?,6?-tri-O-t-butyldimethylsilylsucrose in good yield. In the presence of excess sucrose, a mixture of 6?-O-t- butyldimethylsilyl-, 6,6?-di-O-t-butyldimethylsilyl- and 6,1?,6?-tri-O- t-butyldimethylsilyl-sucroses was formed.

Synthesis of Novel Chiral (Thio)ureas and Their Application as Organocatalysts and Ligands in Asymmetric Synthesis

2008 ◽  
Vol 61 (5) ◽  
pp. 364 ◽  
Author(s):  
Marcos Hernández-Rodríguez ◽  
Claudia Gabriela Avila-Ortiz ◽  
Jorge M. del Campo ◽  
Delia Hernández-Romero ◽  
María J. Rosales-Hoz ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Asymmetric Synthesis ◽  
Carbonyl Group ◽  
Ring Opening ◽  
Enantiomeric Excess ◽  
Quantitative Yield ◽  
Epoxide Ring ◽  
Chiral Auxiliaries ◽  
Epoxide Ring Opening

The synthesis of novel chiral (thio)ureas 1–10 and 14–26 is described. These (thio)ureas incorporate chiral auxiliaries derived from (R)- or (S)-α-phenylethylamine, (R)-phenylglycine, or (1R,2S)-ephedrine. The phenylethyl group in compounds 1–10 and 21–24 adopts a particular orientation in the molecular structure as a consequence of 1,3-allylic strain with the (thio)carbonyl group. Ureas 1–10 were tested as Lewis basic organocatalysts in epoxide ring opening and in aldolic condensation, and it was found that the tetrasubstituted urea (R,R)-2 afforded the best results in terms of reaction yields. (Thio)ureas 20–26 were examined as ligands in the enantioselective diethylzinc addition to benzaldehyde, observing that C2-symmetric chiral urea (R,S,R,S)-20 provides the expected carbinol in nearly quantitative yield and in up to 62% enantiomeric excess.

Room Temperature Flow Electrochemistry as a Means of Retaining the “Memory of Chirality” via Hofer Moest Type Reaction

2020 ◽  
Author(s):  
Tomas Hardwick ◽  
Rossana Cicala ◽  
Nisar Ahmed
Keyword(s):  
Continuous Flow ◽  
Room Temperature ◽  
Biological Activities ◽  
Supporting Electrolyte ◽  
Enantiomeric Excess ◽  
Flow Chemistry ◽  
Batch Processes ◽  
Enabling Technology ◽  
Chiral Compounds ◽  
Memory Of Chirality

<p>Many chiral compounds have become of great interest to the pharmaceutical industry as they possess various biological activities. Concurrently, the concept of “memory of chirality” has been proven as a powerful tool in asymmetric synthesis, while flow chemistry has begun its rise as a new enabling technology to add to the ever increasing arsenal of techniques available to the modern day chemist. Here, we have employed a new simple electrochemical microreactor design to oxidise an L-proline derivative at room temperature in continuous flow. Flow performed in microreactors offers up a number of benefits allowing reactions to be performed in a more convenient and safer manner, and even allow electrochemical reactions to take place without a supporting electrolyte due to a very short interelectrode distance. By the comparison of electrochemical oxidations in batch and flow we have found that continuous flow is able to outperform its batch counterpart, producing a good yield (71%) and a better enantiomeric excess (64%) than batch with a 98% conversion. We have, therefore, provided evidence that continuous flow chemistry has the potential to act as a new enabling technology to replace some aspects of conventional batch processes. </p>

Nickel-Catalyzed Inter- and Intramolecular Carbon-Sulfur Bond Metathesis by Reversible Arylation

2019 ◽  
Author(s):  
Tristan Delcaillau ◽  
Alessandro Bismuto ◽  
Zhong Lian ◽  
Bill Morandi
Keyword(s):  
Good Yield ◽  
Functional Group ◽  
Product Formation ◽  
Single Bond ◽  
Ring Closing Metathesis ◽  
Catalytic Systems ◽  
Metathesis Reactions ◽  
New Applications ◽  
Further Development ◽  
Sulfur Bond

A nickel-catalyzed carbon-sulfur bond metathesis has been developed to access high-value thioethers. 1,2-bis(dicyclohexylphosphino)ethane (dcype) is essential to promote this highly functional group tolerant reaction. Further, synthetically challenging macrocycles could be obtained in good yield in an unusual example of ring-closing metathesis which does not involve alkene bonds. In-depth organometallic studies support a reversible Ni(0)-Ni(II) pathway to product formation. Overall, this work does not only disclose a more sustainable and more functional group tolerant alternative to previous catalytic systems based on Pd, but also presents new applications and mechanistic information which are highly relevant to the further development and application of unusual single bond metathesis reactions.

Enantioselective alpha-Arylation of Benzamides via Synergistic Nickel and Metallaphotoredox Catalysis

2019 ◽  
Author(s):  
John Montgomery ◽  
Alexander W. Rand
Keyword(s):  
Catalytic System ◽  
Functional Group ◽  
Enantiomeric Excess ◽  
New Method ◽  
Aryl Bromides

A new method to access alpha-arylated benzamides has been enabled by metallaphotoredox catalysis. This system allows for non-directed C–H functionalization of N-alkyl benzamides using a dual nickel/iridium catalytic system to form tertiary stereocenters in good enantiomeric excess and moderate yields. This reaction shows excellent functional group compatibility and can be performed using a number of sterically and electronically different aryl bromides and secondary benzamides.

Enantioselective alpha-Arylation of Benzamides via Synergistic Nickel and Metallaphotoredox Catalysis

2019 ◽  
Author(s):  
John Montgomery ◽  
Alexander W. Rand
Keyword(s):  
Catalytic System ◽  
Functional Group ◽  
Enantiomeric Excess ◽  
New Method ◽  
Aryl Bromides

A new method to access alpha-arylated benzamides has been enabled by metallaphotoredox catalysis. This system allows for non-directed C–H functionalization of N-alkyl benzamides using a dual nickel/iridium catalytic system to form tertiary stereocenters in good enantiomeric excess and moderate yields. This reaction shows excellent functional group compatibility and can be performed using a number of sterically and electronically different aryl bromides and secondary benzamides.

Efficient CDI/CH3SO3H -Catalyzed, Microwave-Assisted Synthesis of 2-Substituted Benzothiazoles

2018 ◽  
Vol 16 (1) ◽  
pp. 34-39
Author(s):  
Yao-Wei Li ◽  
Pei-Ming Zhang ◽  
Rui Li ◽  
Yan Bai ◽  
Yu Yu ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Carboxylic Acids ◽  
1H Nmr ◽  
Good Yield ◽  
Microwave Assisted Synthesis ◽  
Synthetic Method ◽  
Benzothiazole Derivatives ◽  
Microwave Assisted ◽  
Highly Effective

CDI combined with CH3SO3H was found to be highly effective for the cyclization of 2-aminothiophenol derivatives with carboxylic acids under MW condition. Fourteen benzothiazole derivatives were synthesized in good yield and their structures were characterized by 1H-NMR, 13CNMR, IR and mass spectrometry. This simple, rapid synthetic method is believed to provide a useful process for the synthesis of 2-substituted benzothiazole compounds.

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