Madhukar N. Jachak

A new series of 1-alkyl-2-oxo-1,2-dihydro-pyrimidine-5-carboxalic acid amides is described. The reaction of N-((E)-3-(dimethylamino)-2-formylacryloyl) formamidine, an intermediate obtained by Vilsmeier–Haack formylation of acetonitrile with various mono-substituted ureas, provides such compounds in good yields.

A rapid and efficient method for the synthesis of novel dipyrazolo[3,4-b:3′,4′-d]pyridines (DPP) from pyrazolo[3,4-b]pyridine was successfully developed. The DPP derivative was further N-alkylated (6, 8) as well as N-linked with amino acids (13) and their photophysical properties were studied along with N-aryl DPP 4 and observed that the chromophores at C₄ position in the aryl ring changed the absorption and emission λ_max.

A convenient route was successfully developed for the synthesis of novel heterocycles such as spiro-oxazino-quinoline derivatives from 2-aminoquinoline-3-carbonitrile (4) in good yield. The Spiro-quinoline derivatives (6, 8 and 10) were synthesized and further studied for their photophysical properties. Semiempirical molecular orbital calculation (PM3/PM6 for structure) proves to be a suitable tool for the prediction of absorption and fluorescence properties of these compounds.

Magnified image Vilsmeier–Haack formylation of acetonitrile using dimethylformamide and phosphorus oxychloride leading to a novel intermediate, N‐((E)‐3‐(dimethylamino)‐2‐formylacryloyl)formamidine 2 and its utility in the synthesis of pyrimidine‐fused heterocycles such as pyrazolo[1,5‐a]pyrimidines and triazolo[1,5‐a]pyrimidine is reported. J. Heterocyclic Chem., 46, 327 (2009).

Magnified image Several new pyrazolo[3,4‐b]pyridine derivatives were synthesized by one pot cyclocondensation of the components; 5‐amino‐3‐aryl‐1H‐phenylpyrazoles, p‐substituted benzoylacetonitriles and some aldehydes. The condensations were most effective by using ammonium acetate as the base catalyst; triethylamine was also studied as a catalyst.

Magnified image An elegant synthesis of highly fluorescent benzo[h]quinolines have been accomplished from readily available and highly economical 6‐methoxy‐1‐tetralone in high purity and excellent yield.