Cu(II)-Ion-Catalyzed Solvolysis of N,N-Bis(2-picolyl)ureas in Alcohol Solvents: Evidence for Cleavage Involving Nucleophilic Addition and Strong Assistance of Bis(2-picolyl)amine Leaving Group Departure
| Autor: | R. Stan Brown, Alexei A. Neverov, Mei-Ni Belzile |
|---|---|
| Rok vydání: | 2014 |
| Předmět: |
inorganic chemicals
animal structures Kinetics Alcohol 010402 general chemistry 01 natural sciences Medicinal chemistry Catalysis Inorganic Chemistry chemistry.chemical_compound Urea Organic chemistry Amines Physical and Theoretical Chemistry Nucleophilic addition 010405 organic chemistry Hydrolysis Leaving group 3. Good health 0104 chemical sciences carbohydrates (lipids) enzymes and coenzymes (carbohydrates) chemistry Alcohols Solvents Amine gas treating Solvolysis Copper |
| Zdroj: | Inorganic Chemistry. 53:7916-7925 |
| ISSN: | 1520-510X 0020-1669 |
| Popis: | The kinetics and products for solvolysis of N-p-nitrophenyl-N',N'-bis(pyridin-2-ylmethyl) urea (7a), N-methyl-N-p-nitrophenyl-N',N'-bis(pyridin-2-yl methyl) urea (7b), and N-phenyl-N',N'-bis(pyridin-2-yl-methyl) urea (DPPU) (7c) promoted by Cu(II) ion in methanol and ethanol were studied under (s)(s)pH-controlled conditions at 25 °C. Methanolysis and ethanolysis of these substrates proceeds rapidly at a 1:1 ratio of substrate:metal ion, the half-times for decomposition of the Cu(II):7a complexes being ~150 min in methanol and 15 min in ethanol. In all cases, the reaction products are the Cu(II) complex of bis(2-picolyl)amine and the O-methyl or O-ethyl carbamate of the parent aniline, signifying that the point of cleavage is the bis(2-picolyl)-N-C=O bond. Reactions of the Cu(II):7b complexes in each solvent proceed about 3-5 times slower than their respective Cu(II):7a complexes, excluding an elimination mechanism that proceeds through an isocyanate which subsequently adds alcohol to give the observed products. The reactions also proceed in other solvents, with the order of reactivity ethanolmethanol1-propanol2-propanolacetonitrile (with 0.2% methanol)water spanning a range of 150-fold. The mechanism of the reactions is discussed, and the reactivity and mode of cleavage are compared with that of the M(II)-promoted ethanolytic cleavage of a mono-2-picolyl derivative, N-p-nitrophenyl-N'-(pyridin-2-yl-methyl) urea (4a), which had previously been shown to cleave at the aniline N-C=O bond. The large estimated acceleration of the rate of attack of ethoxide on 7b of at least 2 × 10¹⁶ provided by associating Cu(II) with the departing group in this urea is discussed in terms of a trifunctional role for the metal ion involving Lewis acid activation of the substrate, intramolecular delivery of a Cu(II)-coordinated ethoxide, and metal-ion-assisted leaving group departure. |
| Databáze: | OpenAIRE |
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