Oxidations by the “hydrogen peroxide–manganese(IV) complex–carboxylic acid” system. : Part 4. Efficient acid-base switching between catalase and oxygenase activities of a dinuclear manganese(IV) complex in the reaction with H2O2and an alkane

2002 ◽  
Vol 26 (9) ◽  
pp. 1238-1245 ◽  
Author(s):  
Georgiy B. Shul'pin ◽  
Galina V. Nizova ◽  
Yuriy N. Kozlov ◽  
Irina G. Pechenkina
Keyword(s):  
Hydrogen Peroxide ◽  
Carboxylic Acid ◽  
Acid System ◽  
Acid Base ◽  
System Part

Pulse polarographic study of the behaviour of some o,o'-dihydroxyazo-compounds

1989 ◽  
Vol 54 (5) ◽  
pp. 1219-1226 ◽  
Author(s):  
Enric Casassas ◽  
Miquel Esteban ◽  
Santiago Alier
Keyword(s):  
Carboxylic Acid ◽  
Reaction Mechanisms ◽  
Sulphonic Acid ◽  
Base Catalysis ◽  
Polarographic Study ◽  
Acid Base ◽  
Eriochrome Black T ◽  
Naphthoic Acid ◽  
Calcon Carboxylic Acid

The reduction of several o,o'-dihydroxyazo-compounds is studied by means of pulse polarographic techniques (DPP, NPP and RPP). The compounds studied are the following: 2-(2'-hydroxyphenylazo)-phenol (o,o'-dihydroxyazobenzene), 1-(2'-hydroxy-1'-naphthylazo)-2-naphthol-4-sulphonic acid (calcon or Eriochrome Blue Black R), 1-(2'-hydroxy-4'-sulpho-1'-naphthylazo)-2-hydroxy-3-naphthoic acid (calcon carboxylic acid), and 1-(1'-hydroxy-2'-naphthylazo)-6-nitro-2-naphthol-4-sulphonic acid (Eriochrome Black T). Correlations between Ip and Epand experimental variables (pH, T, conc.) and instrumental parameters (dropping time, t, and pulse magnitude, ΔE) are established. Reaction mechanisms formerly proposed are discussed on the basis of the new obtained results, and the ranges are defined where adsorption and/or acid-base catalysis are operative.

scholarly journals Harnessing Chemical Energy for the Activation and Joining of Prebiotic Building Blocks

2019 ◽  
Author(s):  
Ziwei Liu ◽  
Long-Fei Wu ◽  
Jianfeng Xu ◽  
Claudia Bonfio ◽  
David Russell ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Carboxylic Acid ◽  
Peptide Nucleic Acid ◽  
Reactive Intermediates ◽  
Building Blocks ◽  
Acid System ◽  
Rna Oligomers ◽  
Prebiotic Activation ◽  
Simultaneous Activation ◽  
Acid Anhydrides

Simultaneous activation of carboxylates and phosphates provides multiple pathways for the generation of reactive intermediates, including mixed carboxylic acid-phosphoric acid anhydrides, for the synthesis of peptidyl-RNAs, peptides, RNA oligomers and primordial phospholipids. These results indicate that unified prebiotic activation chemistry could have enabled the joining of building blocks in aqueous solution from a common pool and enabled the progression of a system towards higher complexity foreshadowing the modern encapsulated peptide-nucleic acid system

The Theodorakis Synthesis of (–)-Jiadifenolide

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Hydrogen Peroxide ◽  
Carboxylic Acid ◽  
Aldol Condensation ◽  
University Of California ◽  
Oxidative Rearrangement ◽  
Promote Neurite Outgrowth ◽  
Starting Point ◽  
Jones Reagent ◽  
Acid Catalyzed ◽  
The University

There has recently been a great deal of interest in the synthesis of natural products that promote neurite outgrowth. Emmanuel A. Theodorakis of the University of California, San Diego described (Angew. Chem. Int. Ed. 2011, 50, 3672) the preparation of one of the most potent (10 nM) of these, (–)-jiadifenolide 3. Fittingly, a key transformation en route to this highly oxygenated seco-prezizaane was the oxidative rearrangement of 1 to 2. The starting point for the synthesis was the commercially available diketone 4. Allylation followed by addition to 5 gave the prochiral triketone 6. Enantioselective aldol condensation following the Tu/Zhang protocol then delivered the bicyclic enone 7. Alkylation to give 8 proceeded with high diastereoselectivity, perhaps controlled by the steric bulk of the silyloxy group. Exposure of the protected ketone to the McMurry reagent PhNTf2 gave the enol triflate 9, which smoothly carbonylated to the lactone 10. Epoxidation with alkaline hydrogen peroxide followed by oxidation gave the carboxylic acid, which spontaneously opened the epoxide, leading to the bis lactone 1. With 1 in hand, the stage was set for the key oxidative rearrangement to 2. It was envisioned that epoxidation would generate the cis-fused 11, which on oxidation would undergo acid-catalyzed elimination to give 12. The newly freed OH would then be in position to engage the lactone carbonyl, leading to 2. In the event, oxidation of the epoxide with the Dess-Martin reagent required sonication for 2 h. The rearranged lactone, even though it was susceptible to further oxidation, was secured in 38% overall yield from 1. After hydrogenation and protection, preparation of the enol triflate 13 from the congested cyclopentanone necessitated the use of the more reactive Comins reagent. Hydrogenation of the trisubstituted alkene from coupling with Me3Al then required 90 atmospheres of H2 overpressure. Hydroxylation of the lactone 14 with the Davis oxaziridine followed by further oxidation to the ketone with the Jones reagent and deprotection then completed the synthesis of (–)-jiadifenolide 3.

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