Iron(iii) catalysed synthesis of unsymmetrical di and trisubstituted ureas – a variation of classical Ritter reaction
作者:Hosamani Basavaprabhu、Vommina V. Sureshbabu
DOI:10.1039/c2ob06916d
日期:——
An application of the classical Ritter reaction for the synthesis of unsymmetrical di and trisubstituted ureas catalyzed by FeCl3 is described. The protocol is of significant interest in view of the easy availability of precursors, mild reaction conditions employed and interestingly its applicability for the alkylation of alcohols capable of forming stable carbocationic intermediates even to the sterically hindered moieties.
Parallel Synthesis of Ureas and Carbamates from Amines and CO<sub>2</sub> under Mild Conditions
作者:Scott L. Peterson、Sabrina M. Stucka、Christopher J. Dinsmore
DOI:10.1021/ol100259j
日期:2010.3.19
A mild and efficient library synthesis technique has been developed for the synthesis of ureas and carbamatesfrom carbamic acids derived from the DBU-catalyzed reaction of amines and gaseous carbondioxide. Carbamic acids derived from primary amines reacted with Mitsunobu reagents to generate isocyanates in situ which were condensed with primary and secondaryamines to afford the desired ureas. Similarly
A fluorous isatoic anhydride and isocyanate are synthesized and used as scavengers for amines in solution-phaseparallelsynthesis of urea, thiourea, and β-hydroxyamine analogs. The resulting fluorous derivatives are readily separated from the reaction mixture by solid-phase extractions (SPE) over FluoroFlash™ cartridges to give products with good purity. The SPE cartridges can be reused.
An easy access to unsymmetrical ureas: a photocatalytic approach to the Lossen rearrangement
作者:Arvind K. Yadav、Vishnu P. Srivastava、Lal Dhar S. Yadav
DOI:10.1039/c4ra03805c
日期:——
synthesis of unsymmetrical ureas from various hydroxamic acids and amines has been developed. Plausibly, the protocol involves visible-light-initiated in situ formation of Vilsmeier–Haack reagent and COBr2 with CBr4 and a catalytic amount of DMF in the presence of Ru(bpy)3Cl2 as a photocatalyst to bring about the Lossenrearrangement at room temperature.