- Synthesis of aminopyridines and aminopyridones by cobalt-catalyzed [2+2+2] cycloadditions involving yne-ynamides: Scope, limitations, and mechanistic insights
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An in-depth study of the cobalt-catalyzed [2+2+2] cycloaddition between yne-ynamides and nitriles to afford aminopyridines has been carried out. About 30 nitriles exhibiting a broad range of steric demand and electronic properties have been evaluated, some of which open new perspectives in metal-catalyzed arene formation. In particular, the use of [CpCo(CO)(dmfu)] (dmfu=dimethyl fumarate) as a precatalyst made possible the incorporation of electron-deficient nitriles into the pyridine core. Modification of the substitution pattern at the yne-ynamide allows the regioselectivity to be switched toward 3- or 4-aminopyridines. Application of this synthetic methodology to the construction of the aminopyridone framework using a yne-ynamide and an isocyanate was also briefly examined. DFT computations suggest that 3-aminopyridines are formed by formal [4+2] cycloaddition between the nitrile and the intermediate cobaltacyclopentadiene, whereas 4-aminopyridines arise from an insertion pathway.
- Garcia, Pierre,Evanno, Yannick,George, Pascal,Sevrin, Mireille,Ricci, Gino,Malacria, Max,Aubert, Corinne,Gandon, Vincent
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supporting information; experimental part
p. 4337 - 4344
(2012/05/20)
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- Process for making dialkyl carbonates
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A process for the production of dialkyl carbonates from the reaction of alcohol, for example C1-C3 alcohols, with urea is disclosed wherein the water and ammonium carbamates impurities in the feed are removed in a prereactor. The water is reacted with urea in the feed to produce ammonium carbamate which is decomposed along with the ammonium carbamates originally in the feed to ammonia and carbon dioxide. In addition some of the urea is reacted with the alcohol in the first reactor to produce alkyl carbamate which is a precursor to dialkyl carbonate. Dialkyl carbonates are produced in the second reaction zone. The undesired by-product N-alkyl alkyl carbamates are continuously distilled off from the second reaction zone along with ammonia, alcohol and dialkyl carbonates under the steady state reactor operation. N-alkyl alkyl carbamates can be converted to heterocyclic compounds in a third reaction zone to remove as solids from the system.
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Page/Page column 10; 11
(2008/06/13)
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- Synthesis of 3,5-Disubstituted 1-Amino-1,3,5-triazine-2,4,6-triones (or 1-Aminocyanurates) by Cyclic Transformation of 1,3,4-Oxadiazol-2(3H)-one Derivatives
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The 5-aryl(or methyl)-3-phenylcarbamoyl-3,4-oxadiazol-2(3H)-ones 2, in the presence of sodium hydride in anhydrous dimethylformamide, were transformed into 1-benzamido(or acetamido)-3,5-diphenyl-1,3,5-triazine-2,4,6-trione derivatives 7 in poor yields. Ho
- Chau, Francois,Malanda, Jean-Claude,Milcent, Rene
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p. 1603 - 1606
(2007/10/03)
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