Nature of the ortho effect. XI. Reaction rates of carboxylic acids with diazodiphenylmethane

1975 ◽  
Vol 40 (4) ◽  
pp. 407-411 ◽  
Author(s):  
Marvin Charton
Keyword(s):  
Carboxylic Acids ◽  
Reaction Rates ◽  
Ortho Effect

scholarly journals Rapid Mechanochemical Synthesis of Amides with Uronium-Based Coupling Reagents, a Method for Hexa-amidation of Biotin[6]uril

2020 ◽  
Author(s):  
Tatsiana Dalidovich ◽  
Kamini A. Mishra ◽  
Tatsiana Shalima ◽  
Marina Kudrjašova ◽  
Dzmitry Kananovich ◽  
...  
Keyword(s):  
Carboxylic Acids ◽  
Reaction Rates ◽  
Solid State Reactions ◽  
Sustainable Chemistry ◽  
Fast Reaction ◽  
Amide Bonds ◽  
Amide Coupling ◽  
Phosphate Species ◽  
Acyl Phosphate ◽  
Phenylalanine Methyl Ester

<p>Solid-state reactions using mechanochemical activation have emerged as solvent-free atom-efficient strategies for sustainable chemistry. Herein we report a new mechanochemical approach for the amide coupling of carboxylic acids and amines, mediated by combination of (1-сyano-2-ethoxy-2-oxoethylidenaminooxy)dimethylaminomorpholinocarbenium hexafluorophosphate (COMU) or <i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>′-tetramethylchloroformamidinium hexafluorophosphate (TCFH) and K<sub>2</sub>HPO<sub>4</sub>. The method delivers a range of amides in high 70–96% yields and fast reaction rates. The reaction protocol is mild, maintains the integrity of the adjacent to carbonyl stereocenters, and streamlines isolation procedure for solid amide products. Minimal waste is generated due to the absence of bulk solvent. We show that K<sub>2</sub>HPO<sub>4</sub> plays a dual role, acting as a base and a precursor of reactive acyl phosphate species. Amide bonds from hindered carboxylic acids and low-nucleophilic amines can be assembled within 90 min by using TCFH in combination with K<sub>2</sub>HPO<sub>4</sub> or <i>N</i>-methylimidazole. The developed mechanochemical liquid-assisted amidation protocols were successfully applied to the challenging couplings of all six carboxylate functions of biotin[6]uril macrocycle with phenylalanine methyl ester, resulting in an 80% yield of highly pure hexa-amide-biotin[6]uril. In addition, fast and high-yielding synthesis of peptides and versatile amide compounds can be performed in a safe and environmentally benign manner, as verified by green metrics.<b></b></p>

scholarly journals Rapid Mechanochemical Synthesis of Amides with Uronium-Based Coupling Reagents, a Method for Hexa-amidation of Biotin[6]uril

2020 ◽  
Author(s):  
Tatsiana Dalidovich ◽  
Kamini A. Mishra ◽  
Tatsiana Shalima ◽  
Marina Kudrjašova ◽  
Dzmitry Kananovich ◽  
...  
Keyword(s):  
Carboxylic Acids ◽  
Reaction Rates ◽  
Solid State Reactions ◽  
Sustainable Chemistry ◽  
Fast Reaction ◽  
Amide Bonds ◽  
Amide Coupling ◽  
Phosphate Species ◽  
Acyl Phosphate ◽  
Phenylalanine Methyl Ester

<p>Solid-state reactions using mechanochemical activation have emerged as solvent-free atom-efficient strategies for sustainable chemistry. Herein we report a new mechanochemical approach for the amide coupling of carboxylic acids and amines, mediated by combination of (1-сyano-2-ethoxy-2-oxoethylidenaminooxy)dimethylaminomorpholinocarbenium hexafluorophosphate (COMU) or <i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>′-tetramethylchloroformamidinium hexafluorophosphate (TCFH) and K<sub>2</sub>HPO<sub>4</sub>. The method delivers a range of amides in high 70–96% yields and fast reaction rates. The reaction protocol is mild, maintains the integrity of the adjacent to carbonyl stereocenters, and streamlines isolation procedure for solid amide products. Minimal waste is generated due to the absence of bulk solvent. We show that K<sub>2</sub>HPO<sub>4</sub> plays a dual role, acting as a base and a precursor of reactive acyl phosphate species. Amide bonds from hindered carboxylic acids and low-nucleophilic amines can be assembled within 90 min by using TCFH in combination with K<sub>2</sub>HPO<sub>4</sub> or <i>N</i>-methylimidazole. The developed mechanochemical liquid-assisted amidation protocols were successfully applied to the challenging couplings of all six carboxylate functions of biotin[6]uril macrocycle with phenylalanine methyl ester, resulting in an 80% yield of highly pure hexa-amide-biotin[6]uril. In addition, fast and high-yielding synthesis of peptides and versatile amide compounds can be performed in a safe and environmentally benign manner, as verified by green metrics.<b></b></p>

SEM analysis of the change in the reaction rates with deposit structures in the copper-iron cementation system

1978 ◽  
Vol 36 (1) ◽  
pp. 456-457
Author(s):  
V. Annamalai ◽  
L.E. Murr
Keyword(s):  
Structural Characteristics ◽  
Secondary Electron Emission ◽  
Copper Deposit ◽  
Reaction Rates ◽  
Sem Analysis ◽  
Experimental Conditions ◽  
Major Drawback ◽  
Emission Mode ◽  
Scrap Iron ◽  
Image Position

Economical recovery of copper metal from leach liquors has been carried out by the simple process of cementing copper onto a suitable substrate metal, such as scrap-iron, since the 16th century. The process has, however, a major drawback of consuming more iron than stoichiometrically needed by the reaction.Therefore, many research groups started looking into the process more closely. Though it is accepted that the structural characteristics of the resultant copper deposit cause changes in reaction rates for various experimental conditions, not many systems have been systematically investigated. This paper examines the deposit structures and the kinetic data, and explains the correlations between them.A simple cementation cell along with rotating discs of pure iron (99.9%) were employed in this study to obtain the kinetic results The resultant copper deposits were studied in a Hitachi Perkin-Elmer HHS-2R scanning electron microscope operated at 25kV in the secondary electron emission mode.

Sign in / Sign up

Export Citation Format

Share Document