Electrochemical Reduction of Pyridine- and Benzene-Substituted <i>n</i>-Alkyl Esters and Thioic <i>S</i>-Esters in Acetonitrile
作者:Richard D. Webster、Alan M. Bond
DOI:10.1021/jo961492u
日期:1997.3.1
Bulk controlled potential electrolysis experiments have been performed on a wide range of n-alkyl-substituted esters and thioic S-esters of pyridine and benzene in dry acetonitrile with tetraalkylammonium salts as the supporting electrolyte. In most cases, the bulk one-electron reduction of oxygen esters results in unstable or semistable radicals being formed that decompose via loss of the alkyl radical to leave the carboxylate anion in high yield (ca. 70-100%). Benzoate and dinicotinate esters are the exception to this where the final decomposition products are numerous and complicated. For the thioic S-esters, two types of decomposition mechanism have been identified as operating depending on the stability of their anion radicals. Thioic S-ester radical anions that are very unstable (lifetimes in the order of several milliseconds) decompose with loss of the thiolate ion to leave a neutral acyl radical that undergoes aromatic substitution reactions with other acyl radicals to form, among other products, gamma-lactones. Thioic S-esters radical anions that are stable for many minutes to hours ultimately decompose via reaction with molecular oxygen to form carboxylate anions.
US5939568A
申请人:——
公开号:US5939568A
公开(公告)日:1999-08-17
[EN] ACCELERATED CATALYSIS OF OLEFINIC EPOXIDATIONS<br/>[FR] CATALYSE ACCELEREE DES EPOXYDATIONS OLEFINIQUES
申请人:——
公开号:WO1998033786A1
公开(公告)日:1998-08-06
[EN] Rhenium-catalyzed epoxidation of olefinic substrates is accelerated by the use of accelerants having a nitrogenous aromatic heterocyclic structure. Use of the accelerants also enables the use of aqueous hydrogen peroxide as an oxidant. To achieve optimum acceleration, the accelerant should have a concentration within a range from 2.0 mole percent to 100 mole percent of the accelerant with respect to 1 mole of the olefinic substrate. Use of the accelerant also results in an increased yield with respect to the conversion of the olefinic substrate to epoxide product. [FR] L'invention se rapporte à l'époxydation de substrats oléfiniques catalysée par le rhénium, qui est accélérée par des accélérateurs à structure hétérocyclique aromatique azotée. En outre, le recours à des accélérateurs permet d'utiliser en tant qu'oxydant le peroxyde d'hydrogène aqueux. Afin d'obtenir une accélération optimale, il faut que la concentration de l'accélérateur soit comprise comprise entre 2,0 et 100 moles d'accélérateur pour cent moles de substrat oléfinique. Le recours à l'accélérateur permet également d'assurer un rendement plus élevé en matière de conversion du substrat oléfinique en produit époxyde.
MnO<sub>2</sub>/TiO<sub>2</sub>catalyzed synthesis of coenzyme pyridoxamine-5′-phosphate analogues: 3-deoxypyridoxamine-5′-phosphate
作者:Sk Jahir Abbas、P. V. R. K. Ramacharyulu、Shyue-Chu Ke
DOI:10.1039/c5ra25779d
日期:——
The highly efficient-selective synthetic route of the pyridoxal-5′-phosphate (vitamin B6, PLP) analogues: C3 substituted deoxy derivatives of pyridoxal (PL), pyridoxal-N-oxide (PLNO), pyridoxamine (PM), pyridoxamine-5′-phosphate (PMP) and pyridoxal-5′-phosphate (PLP), were developed via reduction and followed by selective oxidation in one pot using solid supported nanoparticles. The salient features