Synthesis of a new 1,4‐dihydropyridine containing the imidazo[1,5‐α]pyridine nucleus

Abstract

The synthesis of the new dihydropyridine diethyl 1,4‐dihydro‐4‐(imidazo[1,5‐α]pyridin‐8‐yl)‐2,6‐dimethyl‐pyridine‐3,5‐dicarboxylate (1) is described. After many attempts to prepare the key intermediate aldehyde 2a by different approaches, this compound has been obtained in good yields from methyl 2‐cyano‐3‐pyridinecar‐boxylate (10). A three‐step procedure involving reduction to the amine, formylation with concomitant cyclization and reduction of the ester group was used.

Proton NMR Spectroscopy and Magnetic Properties of a Solution-Stable Dicopper(II) Complex Bearing a Single μ-Hydroxo Bridge

“…Synthesis of ( 3-Methylpyridin-2-yl)methylamine Dihydrochloride. The compound was synthesized according to a slightly modification of the procedure reported earlier by Fos et al A 1 g amount of 2-cyano-3-methylamine was dissolved in 200 mL of dry MeOH and hydrogenated with molecular hydrogen in the presence of 1.5 g of 10% Pd on charcoal. After 6 h, the charcoal was filtered off, and 4 mL of concentrated HCl was added to the resulting solution.…”

A New Class of Fused Imidazoles by Intramolecular Nucleophilic ipso-Substitution in 2-Alkylsulfonylimidazoles: Synthesis of 2,3-Dihydroimidazo[2,1-b][1,3]oxazoles

“…Particularly interesting, are fused [1,2-a]imidazoles, which have been reported to have antiulcer, antidepressant, antibacterial and T x A 2 synthase inhibitory activities. [17][18][19][20] Recently, innovative protocols for the synthesis of [1,2-a]-fused imidazoles using intramolecular radical ipso-substitution at the C-2 position have been reported, 21,22 and although many efforts have been devoted to the synthesis of, for instance, imidazo[1,2-a]pyridines, 23 there are no literature reports on the synthesis of imidazo[2,1-b][1,3]oxazoles.Herein, we wish to report our findings on the use for the first time of alkylsulfonyl substituents in electron-rich imidazoles, as effective leaving groups in intramolecular nucleophilic ipso-substitution reactions, and their application toward the preparation of a novel class of fused imidazoles. Thus, when thiouronium salts 1, readily available from the corresponding alkyl halide and thiourea in refluxing ethanol, were allowed to react in MeCN Figure ORTEP plot 27 of the molecular structure of 3a with 50% probability ellipsoids Downloaded by: NYU.…”

“…Particularly interesting, are fused [1,2-a]imidazoles, which have been reported to have antiulcer, antidepressant, antibacterial and T x A 2 synthase inhibitory activities. [17][18][19][20] Recently, innovative protocols for the synthesis of [1,2-a]-fused imidazoles using intramolecular radical ipso-substitution at the C-2 position have been reported, 21,22 and although many efforts have been devoted to the synthesis of, for instance, imidazo [1,2-a]pyridines, 23 there are no literature reports on the synthesis of imidazo [2,1-b] [1,3]oxazoles.…”

“…Thus, when epoxides 16a,b were treated with 2.5 equivalents of 1H-imidazole (18), 1H-1,2,4-triazole (18) or 1H-1,2,4-triazole (19) were employed, only one type of isomers 22a,b and 23a,b were obtained in near quantitative yields; however, under identical conditions, the use of the potassium salts of 1H-tetrazole (20) or benzotriazole (21) In summary, we have shown that the reaction between thiouronium salts of type 1 and a-halocarbonyl compounds 2 under the described conditions efficiently leads to 2-alkylthioimidazoles 3 in good yields. These compounds are useful precursors in the preparation of novel 2,3-dihydroimidazo[2,1-b][1,3] oxazoles 9 by intramolecular nucleophilic displacement of the 2-sulfonyl derivatives 8.…”

Synthesis of Novel 2,3-Dihydroimidazo[2,1-b][1,3]oxazoles Through Intramolecular Nucleophilicipso-Substitution in 2-Alkylsulfonylimidazoles

“…Particularly interesting are fused [1,2-a]imidazoles, which have been reported to have anti-ulcer, anti-depressant, anti-bacterial and T x A 2 synthase inhibitory activities. [18][19][20][21] Successful synthetic approaches toward the synthesis of fused [1,2-a]imidazoles using intramolecular radical ipso-substitution reactions at the C-2 position have been recently disclosed, 22,23 and although many efforts have been directed to the synthesis of, for instance, imidazo [1,2-a]pyridines, 24 very little has been reported about imidazo [2,1-b] [1,3]oxazoles.…”