Concise routes to pyrazolo[1,5-a]pyridin-3-yl pyridazin-3-ones

Abstract

Cycloaddition of pyridine N-imine with 6-alkyl-4-oxohex-5-ynoates followed by condensation with hydrazine provides concise access to pharmacologically active 6-(pyrazolo[1,5-a]pyridin-3-yl)pyridazinones. For the first time alkynyl heterocycles are also shown to be effective dipolarophiles for pyridine N-imine, and analogous compounds can be accessed directly in modest yields through the reaction of 6-(alkyn-1-yl)pyridazin-3-one derivatives.

Synthesis and Biological Evaluation of Novel σ1 Receptor Ligands for Treating Neuropathic Pain: 6-Hydroxypyridazinones

“…Indeed, the 1-phenyl-1,2-dihydropyridazine-3,6-dione and 6-hydroxy-2-phenylpyridazin-3­(2 H )­one are ambident tautomeric heterocyclic. They are produced via a cyclization of the phenylhydrazine hydrochloride 6 and maleic anhydride 7 in the presence of acetic acid as solvent . In this paper, 6-hydroxy-2-phenylpyridazin-3­(2 H )-one ( 8 ) was prepared in solution of water and hydrochloric acid.…”

Unexpected formation of 2-alkynylpyridines from iodo-selenopyridines by selective activation of C Se over C I bonds

“…These molecules could be applied for the treatment and prevention of abnormal cell proliferation in cancer diseases [1,2]. Additionally, 2-alkynylpyridines represent synthetically relevant intermediates in organic synthesis, because their triple bonds could readily undergo diverse transformations, such as annulation [3], cyclization [4], or 1,3-dipolar cycloaddition [5]. In this context, these compounds contribute to the construction of a large array of heterocyclic frameworks, including azaindoles [6,7], furo [3,4-b]pyridines [8], indolizines [9], isoquinolines [10], aryl-substituted pyridines [11], and N-metallacycles [12].…”

New approach toward the synthesis of deuterated pyrazolo[1,5-a]pyridines and 1,2,4-triazolo[1,5-a]pyridines

“…1,2,4-Triazolo[1,5- a ]pyridines show antifungal [17], antitumor [18], and cytotoxic [19] activities. Both types of heterocyclic cores are readily available from N -aminopyridium salts and related pyridinium- N -imines via 1,3-cycloaddition reaction [20] or intramolecular ring closure [21–24]. The importance of these cores for medical chemistry studies suggests that isotopically labeled pyrazolo[1,5- a ]pyridines and triazolo[1,5- a ]pyridines could be of interest.…”