Early studies of reactions to form C-N bonds involved nucleophilic aromatic
substitution (Scheme 1), reductive amination (Scheme 2) and Ullmann reactions
(Scheme 3). The examples of nucleophilic aromatic substitution and reductive
amination reactions as well as the general scheme of Ullmann reaction are
shown in Schemes 1, 2 and 3. As is observed, each of these has serious
limitations,1-3 such as need for high temperature or pressure, use of strong acids
or reducing agents, and there has always been a need for more versatile
reactions under milder conditions.
HNO3, concd