Unsymmetrical tetra-substituted ureas

An early example of benzotriazole utility was the synthesis of a wide range of unsymmetrical tetra-substituted ureas (4) by reaction of 1,1 -carbonylbis-benzotriazole (2), generated in 90% yield from two equivalents of BtH and phosgene, with secondary amines (Scheme 2). The formation of ureas (4) was achieved in two steps via (3), and high yields were reported for both series of compounds (1997JOC4155). 

Optimal conditions for the synthesis of symmetrically disubstituted or tetra-substituted ureas as well as of unsymmetrically disubstituted or trisubstituted ureas have, however, been developed (see also next Section). 

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See also in sourсe #XX -- [ ]

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