An easy access to unsymmetrical ureas: A photocatalytic approach to the Lossen rearrangement
An efficient and operationally simple method for the 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 Lossen rearrangement at room temperature. the Partner Organisations 2014.
Yadav, Arvind K.,Srivastava, Vishnu P.,Yadav, Lal Dhar S.
p. 24498 - 24503
(2014/07/07)
Iron(III) catalysed synthesis of unsymmetrical di and trisubstituted ureas - A variation of classical Ritter reaction
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. The Royal Society of Chemistry 2012.
Basavaprabhu, Hosamani,Sureshbabu, Vommina V.
p. 2528 - 2533
(2012/04/23)
The efficient synthesis of carbodiimides using a titanium imido complex
An efficient rt synthesis of carbodiimides or ureas from the combination of a titanium imido complex 2 and a range of 12 aryl and aliphatic isocyanates is described. Control experiments suggest that carbodimide formation is via heterocumulene metathesis t
Anderson, James C.,Bou-Moreno, Rafael
experimental part
p. 9182 - 9186
(2011/01/12)
A New Convenient Method for the Synthesis of Symmetrical and Unsymmetrical N,N'-Disubstituted Ureas
A new method is described for the preparation of symmetrically and unsymmetrically disubstituted ureas by aminolysis of bis(4-nitrophenyl) carbonate.The second substitution is slower than the first one, and it is possible to isolate monosubstituted intermediates when equimolar amounts of substrates are used.The reaction of the intermediates with different amines give unsymmetrical derivatives of urea.
Izdebski, Jan,Pawlak, Danuta
p. 423 - 425
(2007/10/02)
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