Investigation of electronic effects in the pyridine and pyridine N-oxide rings. Part 4. Kinetics and mechanism of the reaction of diazodiphenylmethane with substituted carboxypyridine and 2-carboxypyridine N-oxides in dimethylformamide
Rate constants for the reactions of 15 substituted carboxypyridines and four substituted 2-carboxy-pyridine N-oxides with diazodiphenylmethane (DDM) in dimethylformamide (DMF) were determined at 30 °C, by the known spectrophotometric method. For comparison, rate constants for the reaction of 12 substituted benzoic acids were determined under the same conditions. Kinetic and thermodynamic parameters
通过已知的分光光度法,在30°C下测定15个取代的羧基吡啶和四个取代的2-羧基吡啶N-氧化物与重氮二苯基甲烷(DDM)在二甲基甲酰胺(DMF)中的反应的速率常数。为了比较,在相同条件下确定12种取代的苯甲酸反应的速率常数。所获得的动力学和热力学参数,连同产物分析,基本上验证了先前提出的在该溶剂中的反应机理。对结果进行了经验性的Hammett处理,结果表明,散布的总体图(ρ= 1.019,log k o = –2.98,r = 0.91,s = 0.22,n从吡啶氮杂基团和N-氧化物基团的相应σ值以及取代基的Hammettσ常数中,通过加法σ常数获得= = 31)。从取代的苯甲酸(ρ= 1.213,log k o = –2.91,r = 0.985,s = 0.12,n = 12),卤素和硝基取代酸(ρ= 1.07, log k o = –2.99,r = 0.998,s = 0.02,n =
Noto, Renato; Buscemi, Silvestre; Consiglio, Giovanni, Journal of Heterocyclic Chemistry, 1981, vol. 18, p. 735 - 738
Bowden, Keith; Ghadir, Khalaf D. F., Journal of the Chemical Society. Perkin transactions II, 1990, # 8, p. 1329 - 1332
作者:Bowden, Keith、Ghadir, Khalaf D. F.
DOI:——
日期:——
Sulfonated nanohydroxyapatite functionalized with 2-aminoethyl dihydrogen phosphate (HAP@AEPH2-SO3H) as a reusable solid acid for direct esterification of carboxylic acids with alcohols
catalyzed direct esterification of carboxylicacids and alcohols with high selectivity toward the formation of esters in good to excellent yields. Our results clearly show that HAP@AEPH2-SO3H can be easily recovered by simple filtration and reused for subsequent five runs without any significant impact on yields of products. The main advantage of this methodology is easy and ecofriendly catalyst preparation
Atom-economic and stereoselective catalytic synthesis of fully substituted enol esters/carbonates of amides in acyclic systems enabled by boron Lewis acid catalysis
strategy for enol ester synthesis. However, the reported examples come with limitations, including the utilization of noble metal catalysts, the control of regio- and Z/E selectivity, and an application in the synthesis of enol carbonates. Herein, a boron Lewis acid-catalyzed intermolecular carboacyloxylation of ynamides with esters to access fully substituted acyclic enol esters in high yield with