Abstract:The 2-(alkylcarbonyl)benzoic acids obtained by esterification of phthalic anhydride are converted into azide derivatives: alkyl 2-[(azidocarbonyl)amino]benzoates and to ureas: dialkyl 2,2′-[carbonylbis(azanediyl)]dibenzoates. These transformations were carried out using classical Curtius rearrangement conditions in the presence of diphenylphosphoryl azide (DPPA) in a basic medium, followed by hydrolysis. Subsequently, a final condensation reaction of these urea derivatives enabled us to obtain, for the first t… Show more
“…The Cur- tius rearrangement reaction under the same conditions but without the addition of a small proportion of water made it possible to obtain symmetric ureas in very low yields. 21 Previously, other authors described the detection of symmetric ureas as secondary products of the preparation of carbamates from carboxylic acids with DPPA in the presence of alcohols. 19b,22 As indicated above, the classical addition of amines to isocyanates leads to symmetric or asymmetric ureas.…”
Section: Scheme 1 Preparation Of Ureasmentioning
confidence: 99%
“…The Curtius rearrangement reaction under the same conditions but without the addition of a small proportion of water made it possible to obtain symmetric ureas in very low yields. 21…”
The first method for the direct conversion of carboxylic acids into ureas has been developed. The classical procedures described above for the formation of ureas from carboxylic acids require two steps, preparation of the isocyanate followed by its aminolysis. In this work, arylcarboxylic and arylalkylcarboxylic acids have been transformed into symmetric ureas in a single step using DPPA or sodium azide as nitrogen source. The addition of water (method A) or the presence of solvent water (method B) was essential for the formation of symmetrical ureas from the corresponding carboxylic acids. The corresponding ureas have been obtained in good to excellent yields of 46 to 100%. This procedure was compatible with differ-ent substituents present in the starting carboxylic acid.
“…The Cur- tius rearrangement reaction under the same conditions but without the addition of a small proportion of water made it possible to obtain symmetric ureas in very low yields. 21 Previously, other authors described the detection of symmetric ureas as secondary products of the preparation of carbamates from carboxylic acids with DPPA in the presence of alcohols. 19b,22 As indicated above, the classical addition of amines to isocyanates leads to symmetric or asymmetric ureas.…”
Section: Scheme 1 Preparation Of Ureasmentioning
confidence: 99%
“…The Curtius rearrangement reaction under the same conditions but without the addition of a small proportion of water made it possible to obtain symmetric ureas in very low yields. 21…”
The first method for the direct conversion of carboxylic acids into ureas has been developed. The classical procedures described above for the formation of ureas from carboxylic acids require two steps, preparation of the isocyanate followed by its aminolysis. In this work, arylcarboxylic and arylalkylcarboxylic acids have been transformed into symmetric ureas in a single step using DPPA or sodium azide as nitrogen source. The addition of water (method A) or the presence of solvent water (method B) was essential for the formation of symmetrical ureas from the corresponding carboxylic acids. The corresponding ureas have been obtained in good to excellent yields of 46 to 100%. This procedure was compatible with differ-ent substituents present in the starting carboxylic acid.
Recent advances of diphenyl phosphorazidate (DPPA) as a versatile synthetic reagent was described. It works as an azide anion equivalent, 1,3-dipole, an electrophile, and nitrene. Thus it can be conveniently...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.