Experimental and Theoretical Studies on the Tautomerism in 2-Aminopyridines and 2(1H)-Pyridinones: Synthesis of 2-Amino-4-aryl-3-cyano-6-(3,4-dimethoxyphenyl)pyridines and 4-Aryl-3-cyano-6-(3,4-dimethoxyphenyl)-2(1H)-pyridinones

Abstract

Under solvent-free conditions and in one-pot, a series of 2-amino-4-aryl-3-cyano-6-(3,4-dimethoxyphenyl)-pyridines and 4-aryl-3-cyano-6-(3,4-dimethoxyphenyl)-2(1H)-pyridinones were prepared using 3,4-dimethoxyacetophenone, an aldehyde, malononitrile (or ethyl cyanoacetate), and ammonium acetate in the presence of 3-methyl-1-(4-sulfonylbutyl)imidazolium hydrogen sulfate [HO 3 S(CH 2 ) 4 MIM][HSO 4 ] (a Brønsted acidic ionic liquid) as the catalyst in very short reaction time. The preference for the formation of more stable tautomers was consistence with the theoretical calculation using the Gaussian 03 program at the B3LYP hybrid density functional level.

Synthesis of 2-Amino-4,6-diarylnicotinonitriles Using Silica-Bound N-Propyl Triethylenetetramine Sulfamic Acid as a Recyclable Solid Acid Catalyst

“…Chloropropyl silica was prepared according to a previously reported procedure [23]. All of the products were characterized by comparison of their IR, 1 H, and 13 C NMR spectroscopic data and their melting points with the reported values [7][8][9][10][11][12][13][14][15].…”

“…In contrast, straight-forward and efficient one-pot catalytic procedures for the synthesis of 2-amino-3-cyanopyridines under mild conditions are still limited. Most recently, there have been reports describing the synthesis of 2-amino-3cyanopyridines according to a two step synthesis [13] using either a Brönsted acidic ionic liquid at 150 °C [14] or Yb(PFO) 3 in refluxing ethanol [15].…”

Synthesis and Biological Evaluation of Glycosides and Acyclic Nucleosides Derived 2‐Oxonicotinonitriles

“…2‐Pyridones and 2‐thionopyridones are known exists in two tautomeric forms: amide/thioamide and 2‐hydroxypyridine/2‐mercaptopyridinesforms, respectively . In addition to the reaction conditions under which the alkylation of 2‐pyridone/2‐thionopyridone is performed, the distribution ratio of these tautomers is expected to contribute to the N ‐/ O ‐alkylation selectivity under basic conditions.…”

Synthesis and biological evaluation of 2-oxonicotinonitriles and 2-oxonicotinonitrile based nucleoside analogues

“…This was also emphasized by the presence of an 1 H NMR peak at a chemical shift higher than 12 ppm, corresponding to the amide NH. Obtaining the amido tautomer rather than the imido was explained by a recent study showing that the amido tautomer was more stable and hence predominant [20].…”