An efficient, metal-free, room temperature aromatization of Hantzsch-1,4-dihydropyridines with urea–hydrogen peroxide adduct, catalyzed by molecular iodine
A mild, highly efficient and metal-free synthetic method for aromatization of 1,4-dihydropyridines employing urea–hydrogen peroxide adduct as oxidant catalyzed by 20 mol % of molecular iodine was developed. The reaction was carried out in ethyl acetate at roomtemperature and the products were isolated in high to excellent yields. A plausible free-radical mechanism is proposed based on results obtained
Rapid aromatization of Hantzsch-1,4-DHPswith t-butylhydroperoxide catalysed by iron(III) phthalocyanine chloride is described. The reaction proceeds smoothly at room temperature within 1-35 min and the products of high purity were isolated in excellent yields. To explain the reactivity of this catalytical system plausible mechanism have been proposed to involve formation of high-valent oxoferryl species as in cytochrome P450 itself. (C) 2008 Elsevier Ltd. All rights reserved.
Ring-contraction of hantzsch esters and their derivatives to pyrroles <i>via</i> electrochemical extrusion of ethyl acetate out of aromatic rings
作者:Xu Liu、Chang Liu、Xu Cheng
DOI:10.1039/d1gc00487e
日期:——
ring-contraction of HEs and theirs pyridinederivatives is developed to obtain polysubstituted pyrroles. This process provides an orthogonal utilization of Hantzsch esters for the well-documented application as side chain or hydrogen donors. The formal transformation shows an extrusion of ethyl acetate out of the pyridine ring in a single step. In addition to the novel transformation, we also discovered the Lewis
Oxidative aromatization of 1,4-dihydropyridines and pyrazolines using HbA–H2O2: An efficient biomimetic catalyst system providing metabolites of drug candidates
作者:Atul Kumar、Ram Awatar Maurya、Siddharth Sharma
DOI:10.1016/j.bmcl.2009.05.056
日期:2009.8
Human hemoglobin (HbA) efficiently catalyses the oxidative aromatization of 1,4-dihydropyridines (1,4-DHPs) and pyrazolines with hydrogen peroxide in phosphate buffer. The results of the study reveal that the rates of oxidative aromatization of 1,4-DHPs are substituent dependent. Thus, the present study is very useful in understanding the metabolism of 1,4-DHP drugs in liver by cytochrome P450 and designing novel drugs as well as modifying the existing drugs for better pharmacokinetic profile. (C) 2009 Elsevier Ltd. All rights reserved.