Synthesis of Ureas by Pd-Catalyzed Carbonylation of Amines
process. In both cases, there are still disadvantages to
be overcome, particularly from the standpoint of catalytic
efficiency. Moreover, several procedures are limited to
the preparation of symmetrically substituted ureas, while
in some instances ureas are obtained in a mixture with
different carbonylation products, mainly carbamates
and/or oxamides. Importantly, in several cases the oxida-
tive carbonylation process was carried out using mixtures
of CO and O2 that are within the explosion range of
CO in O2.27
ylation of primary aliphatic or aromatic amines 1 to the
corresponding symmetrically disubstituted ureas 2, with
oxygen as the oxidizing agent, and further extension to
the synthesis of unsymmetrically trisubstituted ureas.
As we have already pointed out in our preliminary
communication,28 the methodology is characterized by
unprecedented catalytic efficiencies for this kind of
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