Tri-substituted
pyridines are important scaffolds that can be found
in a plethora of commercially available drugs. A one-pot general method
for the selective synthesis of less explored/challenging patterns
of tri-substituted pyridines is described. Hydroamination of alkynes
with commercially available N-triphenylsilylamine
generates N-silylenamines. These in situ generated N-silylenamines, upon reaction with α,β-unsaturated
carbonyl compounds and subsequent oxidation, furnish 25 examples of
selectively substituted 2,4,5-, 2,3,4-, 3,4,5-, 2,3,5-, and 2,3,6-trisubstituted
pyridines in up to 78% yield. The reaction features high functional
group compatibility providing an expeditious and general approach
for the assembly of selectively substituted tri-substituted pyridine
derivatives. The robustness and practicality of the reaction have
been demonstrated in a gram-scale reaction.