Guanidines: from classical approaches to efficient catalytic syntheses

Abstract

From organosuperbases capable of base-catalyzing organic reactions, through versatile 'ligand-sets' for use in coordination chemistry, to fundamental entities in medicinal chemistry, guanidines are amongst the most interesting, attractive, valuable, and versatile organic molecules. Since the discovery of these compounds, synthetic chemists have developed new methodologies that are mainly based on multi-step and stoichiometric reactions. Despite the fact that these methodologies are still being used by the interested scientific and industrial communities, drawbacks such as the poor availability of precursors, low yields, and use and production of undesirable substances highlight the need for safe, simple and efficient syntheses of these entities. This review focuses on the metal-mediated catalytic addition of amines to carbodiimides as an atom-economical alternative to the classical synthesis.

Half‐Sandwich Guanidinate–Osmium(II) Complexes: Synthesis and Application in the Selective Dehydration of Aldoximes

“…Interestingly, the electronic nature of the N-aryl substituents of the guanidinate ligands plays a significant role in both the efficiency and selectivity of the process. Thus, the best results were obtained with complexes 3d-g bearing the strong electron-withdrawing CF 3 and CN groups, which led to the almost quantitative consumption (≥96 % by GC) of the starting (E)-benzaldoxime after only 2 h (entries 4-7). By employing these complexes, the quantity of benzamide formed never exceeded 1 %.…”

“…[2] Notably, some of them have found utility in catalysis (e.g., polymerization of olefins, hydroamination of alkynes), as well as in materials science as precursors for chemical vapor deposition (CVD) and atom layer deposition (ALD) applications. [2] The easy generation of guanidinate mono-and dianions from readily available guanidines, [3] along with their high steric and electronic modulability, have allowed the coordination of these ligands to virtually all transition metals. [2] In this context, we recently reported the preparation of a series of ruthenium(II)-and ruthenium(IV)-guanidinate derivatives (see A and B in Figure 1), which proved were also formed in these reactions.…”

On the Basicity of Organic Bases in Different Media

“…Acids and bases serve as catalysts in a variety of chemical and biochemical transformations, playing a crucial role in the processes of life. Their significance in chemistry is not limited to the disciplines of physical organic and synthetic chemistry but extends to chemical engineering and industrial applications . Also, the fact that almost 80 % of all drugs contain ionisable groups underlines the indispensability of knowing p K a values in medicinal chemistry and understanding the factors that influence them for effective drug design.…”

Micelle‐Enabled One‐Pot Guanidine Synthesis in Water Directly from Isothiocyanate using Hypervalent Iodine(III) Reagents under Mild Conditions

“…Guanidines are important moieties that attract many interests in agricultural and pharmaceutical industry due to their broad spectrum of biological activities . Many therapeutic agents have been constructed from this scaffold such as Cimetidine 1 (treatment of heartburn and peptic ulcers) and Pinacidil 2 (treatment of hypertension) (Scheme ).…”