Synthesis of New Dialkyl 2,2′-[Carbonylbis(azanediyl)]dibenzoates via Curtius Rearrangement

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 time, the new alkyl derivatives, alkyl 2-[2,4-dioxo-1,2-dihydroquinazolin-3(4H)-yl]benzoates. All the new compounds obtained in satisfactory yields were characterized by 1H and 13C NMR, and by X-ray crystallographic analysis.

New Route to Direct Synthesis of Symmetrical Ureas from Carboxylic Acids

“…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.…”

“…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…”