New Pyrazole‐ and Benzimidazole‐derived Ligand Systems

Abstract

A series of N‐containing heterocyclic compounds have been synthesized using approaches such as the well‐known Knorr synthesis, and a facile N‐alkylation method. This series of compounds includes pyrazole derivatives, tris(2‐benzimidazolylmethyl)amine derivatives, and “pincer” ligands. Characterization methods include 1H NMR, FT‐IR, CHN analyses, UV‐vis spectroscopy, and fluorimetry, while X‐ray crystal structures are reported for most of the compounds. The crystallographic results affirm a 13C NMR method for isomer assignment of substituted pyrazoles.

Iodonium salts as efficient iodine(iii)-based noncovalent organocatalysts for Knorr-type reactions

“…Knorr-type syntheses 50,51 conventionally proceed under mild conditions even in the absence of a catalyst if amines and carbonyl compounds are employed as the reactants. 52 However, for less nucleophilic hydrazine derivatives, e.g.…”

“… 52 However, for less nucleophilic hydrazine derivatives, e.g. 2-pyridine hydrazines 50 or acyl hydrazides, 53,54 a catalyst is desirable to conduct the reaction under mild conditions. Thus, the reaction of N -acyl hydrazides with 1,3-dicarbonyl compounds, which leads to N -acyl pyrazoles, typically requires an additional activation and is usually conducted in the presence of a Brønsted or a Lewis acid under reflux for several hours.…”

Synthesis, Structures, and Reactivities of Iron Complexes Bearing an Isoindoline‐Based, Polyprotic Pincer‐Type Pyrazole Ligand

“…The target 1,3‐bis(pyrazol‐3‐ylimino)isoindoline ligand 1 as a pyrazole analogue of BPI was obtained by condensation of phthalonitrile and a 3‐aminopyrazole (Scheme 2). [5] The synthesis and crystal structures of 5‐methyl‐ and 5‐phenylpyrazole congeners of 1 have been reported recently [15] but their coordination chemistry was unexplored.…”

Catalytic transformations of glycerol via hydroxyacetone into nitrogen heterocycles of industrial interest

“…Recent literature teems with other examples of simple N-heterocycles whose synthesis are shifting from fossil-based resources towards biomass-derived feedstocks. For example, pyrazoles, traditionally synthesized by the reaction of hydrazines with α,βunsaturated aldehydes or diketones [264,265], ultimately coming from olefins, are also being prepared from sugars [266,267], β-ketoesters and aromatic aldehydes from lignin [268], and 1,3-diols [269], reacting with hydrazine derivatives to yield a diversity of pyrazole derivatives. Industrially, imidazoles are synthesized from the condensation of 1,2-dicarbonyls with ammonia and aldehydes via the Radziszewski reaction [270].…”