Pyrazole-carboxaldehydes as versatile precursors for different pyrazole-substituted heterocyclic systems

Abstract

In the last decade, interest in pyrazole chemistry has grown considerably due to the discovery of fascinating properties demonstrated by a large number of pyrazole derivatives. They occur in a wide range of natural products, dyes, and as scaffolds in a number of drugs and associated pharmaceutical active substances. Substantial attention has been paid to the creation of hybrid molecules in which two heterocycles are bound in a single molecule to enhance their biological effectiveness and overcome drug resistance. In this regard, this review illustrated various methods for the construction of pyrazole-substituted heterocycles and their corresponding fused derivatives using pyrazole carboxaldehydes as effective precursors. The heterocyclic systems mentioned in this review are categorized according to the type of the heterocyclic systems.

Synthesis and characterization of novel biheterocyclic compounds from 3‐alkoxy‐1H‐pyrazole‐4‐carbaldehydes via multicomponent reactions

“…For example, A. Domling's group synthesized 1-(1H-tetrazol-5-yl)imidazo [1,5-a]pyridines via a one-pot reaction of pyridine-2-carboxaldehyde, an amine reactant, isocyanides, and azidotri(methyl)silane [24]. Pyrazole-4-carbaldehydes are very useful building blocks in organic synthesis [25][26][27]. For example, Sivaprasad and Peramal reported the Biginelli coupling reaction of 3-aryl-1-phenyl-1Hpyrazole-4-carbaldehydes with ethyl acetoacetate and urea in the presence of phosphotungstic acid to give 4-(3-aryl-1-phenyl-4-pyrazolyl)-1,2,3,4-tetrahydropyrimidin-2-ones [28].…”

Synthesis of various pyrazole-fused heterocyclic systems using pyrazole-4-carbaldehydes as versatile precursors

“…Very recently, we reviewed the usefulness of pyrazole-4-carbaldehydes as versatile precursors for different pyrazole-substituted heterocyclic systems. 52 Heterocyclic compounds mentioned in this review are arranged based on the size of the heterocyclic ring as well as the position and number of the heteroatoms. 53 reported that heating of 3-aryl-1-phenyl-1H-pyrazol-4-carbaldehydes 1 with ethyl azidoacetate 2 in ethanol followed by heating in toluene at reflux gave pyrrolo [2,3-c]pyrazole derivatives 3a and 3b in 30 and 35% yield, respectively (Scheme 1).…”