A practical palladium-catalyzed cascade C-N cross-coupling/Heck reaction of alkenyl bromides with amino-o-bromopyridines is described for a straightforward synthesis of substituted 4-, 5-, 6-, and 7-azaindoles using a Pd2(dba)3/XPhos/t-BuONa system. This procedure consists of the first cascade C-N cross-coupling/Heck approach toward all four azaindole isomers from available aminopyridines. The scope of the reaction was investigated and several alkenyl bromides were used, allowing access to different substituted azaindoles. This protocol was further explored for N-substituted amino-o-bromopyridines.
The aminopyridines are key building blocks in the synthesis of bioactive heterocyclic compounds such as azaindoles and imidazopyridines. The role of metal-catalyzed methods in aminopyridine functionalization, in particular the catalytic systems used, reaction conditions and the influence of aminopyridine substituents on the reaction outcome, is outlined. The review covers different metal-catalyzed reactions developed for C-C and C-N bond formation. One-pot and multicomponent reactions directed towards aminopyridine-
A new family of hypervalent iodine
reagents containing transferable
primary amine groups is described. Benziodoxolone-based reagents were
synthesized on the gram-scale through operationally simple reactions
in up to quantitative yields. These bench-stable solids were characterized
by X-ray analysis and successfully employed in the α-amination
of indanone-based β-ketoesters in up to 83% yield. Mechanistic
studies indicate a substitution mechanism involving an electrophilic
amine.
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