Studies with Heteroaromatic Amines: the Reaction of Some Heteroaromatic Amines with 1-Substituted 3-Dimethylaminopropanones, Enaminones and Cinnamonitriles†

Abstract

Heteroaromatic amines react with 1-substituted 3-dimethylaminopropanones, with enaminones and with cinnamonitriles to yield azolopyrimidines or azolopyridines.

Synthesis of Some New 6,8‐Disubstituted 7,8‐Dihydropyrimido[2,3:4,3]pyrazolo[1,5‐a]pyrimidines and 6,7,8‐Trisubstituted Pyrimido[2,3:4,3]Pyrazolo[1,5‐a]Pyrimidine Derivatives

“…Spectroscopic analyses revealed that 3-(1-phenylprop-2-enone-3-yl)amino-4-methyl-6-phenylpyrazolo [3,4- [31][32] have also reported an analogous reaction in their papers. The structure of compound 20a was further confirmed from an independent synthesis of compound 20a by the reacting of compound 19a in glacial acetic acid/hydrochloride (1:1) under reflux to afford a product identical in all respects (mp., mixed mp., TLC and spectra) (Scheme II).…”

Studies with enamines: Functionally substituted enamines as aldehyde equivalents in Gewald reaction

“…We have, in the last decade, utilized such functionally substituted enamines extensively as precursors to functionally substituted aromatic compounds 14,15 and heteroaromatic compounds. [16][17][18][19][20] We noted that only a few examples of the use of enamines 3a as precursors to aminothiophenes have been reported. …”

2H-Pyrazol-3-ylamines as precursors for the synthesis of polyfunctionally substituted pyrazolo[1,5-a]pyrimidines

“…3-(2'-chlorophenylazo)-2-ethyl-5-phenyl-pyrazolo[1,5-a] (11). A solution of 5a (1 mmol) and 2 (1 mmol) in pyridine (10 ml) was refluxed for 5 h then left to cool to room temperature , poured onto water and neutralised by diluted hydrochloric acid.…”

“…However, in some cases the only isolable products are the finally formed pyrazolo [1,5-a]pyrimidines. 10,11 In such cases the identification of the exact regioorientation of the reactants could be only established with certainty by X-ray crystal structure determinations. 12 In the past 9 we have described several synthetic approaches to pyrazolo [1,5-a]pyrimidines via reacting α,β-unsaturated nitriles and esters with 3-amino-1H-pyrazoles.…”