Synthesis of hydroxyquinoline,
A microwave acceleration effect was observed in Zr IV -catalyzed carbamate-urea exchange.
Aliphatic and aromatic aldehydes can be converted to acyl azides by treatment with iodine azide. Williams, Tetrahedron,59, Zirconium IV -catalyzed exchange processes of dialkyl carbonates and carbamates in the presence of amines gave carbamates and ureas using 2-hydroxypyridine HYP and 4-methylhydroxyquinoline MeHYQ as catalytic additives, respectively.
This simple, versatile, one-pot procedure for the synthesis of substituted O-aryl carbamates offers an economical and efficient route to many compounds of interest. The reactivity dramatically depends on the employed solvent, with [bmim]Cl showing the best reactivity.
Subsequent Curtius rearrangement in the presence of tetrabutylammonium bromide and zinc II triflate and trapping of the isocyanate derivative gives the desired product. A smooth and efficient oxidation of isonitriles to isocyanates by DMSO as the oxidant is catalyzed by trifluoroacetic anhydride.
Adler, Synthesis,48, Hydroxamic acids were synthesized from Synthesis of hydroxyquinoline acids and hydroxylamine hydrochloride in the presence of ethyl 2-cyano 4-nitrophenylsulfonyloxyimino acetate 4-NBsOXY.
Sureshbabu, Synthesis, Yoon, Synlett, An efficient, one-pot procedure for the Hofmann rearrangement of aromatic and aliphatic amides provides methyl and benzyl carbamates in high yields in the presence of N-bromoacetamide and lithium hydroxide or lithium methoxide.
Katritzky, Synlett, A variety of amines can be employed successfully, leading to high yields of isolated ureas. The reaction of di-tert-butyl dicarbonate or a Synthesis of hydroxyquinoline and sodium azide with an aromatic carboxylic acid produces the corresponding acyl azide.
N-Substituted carbamoyl chlorides can be formed in situ and subsequently reacted with substituted phenols to avoid the direct manipulation of sensitive reactants. The process is complete in a few minutes, forming dimethyl sulfide as the only byproduct.
The acyl azide undergoes a Curtius rearrangement to form an isocyanate derivative which is trapped either by an alkoxide or by an amine to form the aromatic carbamate or urea. The newly formed isocyanates may be used directly or isolated in high purity by solvent evaporation.
The acyl azide undergoes a Curtius Dating sites eharmony to form an isocyanate derivative which is trapped either by an alkoxide or by an amine to form the aromatic carbamate or urea. This process is experimentally simple and mild, with imidazole and CO2 being the sole stoichiometric byproduct.
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