RESUMO
2-Chloro-1-(1-ethoxyvinyl)pyridinium triflate and several other bench-stable N-(1-alkoxyvinyl) 2-halopyridinium triflates have been developed as reagents for the synthesis of valuable 2-aminopyridine scaffolds via unusually mild SNAr substitutions with amine nucleophiles. Advantages of this approach include an operationally simple mix-and-stir procedure at room temperature or mild heat and ambient atmosphere and without the need for transition metal catalysts, coupling reagents, or high-boiling solvents. The stable N-(1-ethoxyvinyl) moiety serves as a dual SNAr-activating group and pyridine N-protecting group that can be cleaved under thermal, acidic, or oxidative conditions. Preliminary results of other nucleophilic substitutions using oxygen-, sulfur-, and carbon-based nucleophiles are also demonstrated.
RESUMO
The novel bench-stable N-quaternized ketene N,O-acetal, C16H19N2O+·CF3O3S-, was synthesized and its structure determined. The title compound is a rare example of a pyridinium ketene hemiaminal for which a crystal structure has been determined, joining the 2-chloro-1-(1-ethyoxyethen-yl)pyridin-1-ium tri-fluoro-methane-sulfonate salt from which it was synthesized. The cationic species of the title compound can be defined by three individually planar fragments assembling into a non-coplanar cation. The phenyl substituent extending from the amino nitro-gen atom and the ethyoxyvinyl substituent extending from the pyridine N atom are oriented on the same side of the mol-ecule and maintain the closest coplanar relationship of the three fragments. Supra-molecular inter-actions are dominated by C-Hâ¯O inter-actions from the cation to the SO3 side of the tri-fluoro-methane-sulfonate anion, forming a two-dimensional substructure.