Approach to the Library of Fused Pyridine-4-carboxylic Acids by Combes-Type Reaction of Acyl Pyruvates and Electron-Rich Amino Heterocycles

Abstract

A library of fused pyridine-4-carboxylic acids (including pyrazolo[3,4-b]pyridines, isoxazolo[5,4-b]pyridines, furo[2,3-b]pyridines, thieno[2,3-b]pyridines, and pyrido[2,3-d]pyrimidines) was generated by Combes-type reaction of acyl pyruvates and electron-rich amino heterocycles followed by hydrolysis of the ester. The library members were also demonstrated to undergo the standard combinatorial transformations including amide coupling and esterification, as well as less common heterocyclizations to 1,2,4-triazoles and 1,2,4-oxadiazoles.

Camphorsulfonic Acid Catalyzed One-Pot Three-Component Reaction for the Synthesis of Fused Quinoline and Benzoquinoline Derivatives

“…Quinolines act as effective ligands in cross-coupling reactions and they also play a crucial role in asymmetric synthesis as a catalyst. , In addition, they are also used as ligands for preparation of OLED complexes and with conjugated polymers acting as chemosensors of metal ions. , Due to their potential biological activity and tremendous applications, chemists have developed various classical methods for the synthesis of quinolines such as the Combes reaction, Skraup reaction, Doebner–von Miller, Conrad–Limpach, and Knorr synthesis which involve the formation of a new C – C bond as shown in (Figure , 1a), whereas, in Pfitzinger and Friedlander reactions, new C – C and C – N bonds were formed as shown in (Figure , 1b). In a traditional approach, there are new strategies that have emerged for the synthesis of quinolines through intramolecular cyclization that involve formation of a new C – N bond (Figure , 1c), N – C bond (Figure , 1d), and new C – C bond through cross-dehydrogenative coupling, − dual oxidative coupling, and oxidative tandem reactions .…”

New carbohydrazide derivatives of 1H-pyrazolo[3,4-b]pyridine and trypanocidal activity

“…Summing up, carbohydrazide compounds (4a -4c) were synthesized by nucleophilic substitution reaction in the C=O group of the 4-carboxylate ester (1-3) (Dias et al 2000, Volochnyuk et al 2010) with unsubstituted hydrazine monohydrate, in yields exceeding 90% (Figure 1). The structural characterization and degrees of purity were analyzed by spectroscopic methods (IR, NMR and HRMS).…”

Synthesis and Biological Activity of New [1,3]Thiazolo[4,5-d]pyridazin-4(5H)-ones

“…4-Furan-2-yl-2,4-dioxobutyric acid methyl ester 11a and 2,4-dioxo-4-thiophen-2-yl-butyric acid methyl ester 11b were synthesized from 2-acetylfuran 5a and 2-acetylthiophene 5b by the reaction with ethyl oxalate in the presence of sodium methylate by method [ 10 , 11 ].…”