Direct access to 2-(N-alkylamino)pyrimidines via ruthenium catalyzed tandem multicomponent annulation/N-alkylation

One-Pot Sustainable Synthesis of Highly Substituted Pyrimidines via Acceptorless Dehydrogenative Annulation of Alcohols Using Pincer Ni(II)-NNS Catalysts

We report an efficient and sustainable synthesis of highly substituted pyrimidines promoted by nickel(II)-NNS pincer-type complexes via acceptorless dehydrogenative annulations of readily available alcohols, malononitrile, and guanidine/benzamidine salt under eco-friendly conditions for the first time. Different sets of Ni(II) complexes (C1-C3) encapsulated in NNS pincer-type thiosemicarbazone ligands have been synthesized and authenticated by analytical and spectroscopic (Fourier transform infrared, nuclear magnetic resonance, and high-resolution mass spectrometry) techniques. The solid state three-dimensional structure of a representative complex (C2) has been determined with the aid of single crystal XRD analysis and confirms a square planar architecture around the nickel ion. Further, the well-defined Ni(II) complexes have been employed as efficient catalysts for the fabrication of a wide range of 4-aminopyrimidine-5-carbonitrile derivatives (33 examples) from readily available alcohols with suitable coupling partners such as malononitrile and guanidine/benzamidine under eco-friendly conditions. The current catalytic approach affords maximum yields up to 95% utilizing 3 mol % catalyst loading and water/hydrogen as the only byproduct. A feasible catalytic pathway has been proposed based on the different control experiment reactions, which clearly indicate that the coupling reaction proceeds via aldehyde and benzylidenemalononitrile intermediates. The practicability of the current protocol has been demonstrated by the large-scale synthesis of one of the products, 4-amino-2,6-diphenylpyrimidine-5-carbonitrile, and a short synthesis of a cytosine antifungal analogue.

Transition-Metal Catalyzed Synthesis of Pyrimidines: Recent Advances, Mechanism, Scope and Future Perspectives

Pyrimidine is a pharmacologically important moiety that exhibits diverse biological activities. This review reflects the growing significance of transition metal-catalyzed reactions for the synthesis of pyrimidines (with no discussion being made on the transition metal-catalyzed functionalization of pyrimidines). The effect of different catalysts on the selectivity/yields of pyrimidines and catalyst recyclability (wherever applicable) are described, together with attempts to illustrate the role of the catalyst through mechanisms. Although several methods have been researched for synthesizing this privileged scaffold, there has been a considerable push to expand transition metal-catalyzed, sustainable, efficient and selective synthetic strategies leading to pyrimidines. The aim of the authors with this update (2017-2023) is to drive the designing of new transition metal-mediated protocols for pyrimidine synthesis.

Manganese-Catalyzed Chemoselective Coupling of Secondary Alcohols, Primary Alcohols and Methanol

Herein, we report a manganese-catalyzed three-component coupling of secondary alcohols, primary alcohols and methanol for the synthesis of β,β-methylated/alkylated secondary alcohols. Using our method, a series of 1-arylethanol, benzyl alcohol derivatives, and methanol undergo sequential coupling efficiently to construct assembled alcohols with high chemoselectivity in moderate to good yields. Mechanistic studies suggest that the reaction proceeds via methylation of a benzylated secondary alcohol intermediate to generate the final product.

A DFT Investigation of the Reactivity of Guanidinium Salts in Tandem aza-Michael Addition/Intramolecular Cyclization

A proposed mechanism of the reaction of guanidinium chlorides with dimethyl acetylenedicarboxylate in a tandem aza-Michael addition reaction/intramolecular cyclization was investigated by DFT M06-2X and B3LYP computational approaches. The energies of the products were compared against the G3, M08-HX, M11, and wB97xD data or experimentally obtained product ratios. The structural diversity of the products was interpreted by the concurrent formation of different tautomers formed in situ upon deprotonation with a 2-chlorofumarate anion. A comparison of relative energies of the characteristic stationary points along the examined reaction paths indicated that the initial nucleophilic addition is energetically the most demanding process. The overall reaction is strongly exergonic, as predicted by both methods, which is primarily due to methanol elimination during the intramolecular cyclization step producing cyclic amide structures. Formation of a five-membered ring upon intramolecular cyclization is highly favored for the acyclic guanidine, while optimal product structure for the cyclic guanidines is based on a 1,5,7-triaza [4.3.0]-bicyclononane skeleton. Relative stabilities of the possible products calculated by the employed DFT methods were compared against the experimental product ratio. The best agreement was obtained for the M08-HX approach while the B3LYP approach provided somewhat better results than the M06-2X and M11 methods.

Catalyzed Methods to Synthesize Pyrimidine and Related Heterocyclic Compounds

This review covers articles published in the period from 2010 to mid-2022 on synthetic advances in the formation of pyrimidine and related heterocyclic compounds. Special emphasis has been given to the different types of cycloadditions, taking into account the number of their components and leading to the formation of the pyrimidine ring. Due to the large number of publications on the Biginelli reaction and related reactions, this will be dealt with in a separate review in the near future.

Tandem synthesis of N-methylated tertiary amines via three-component coupling of carbonyl compounds, amines, and methanol

An Ir-catalyzed tandem synthesis of various N-methylated tertiary amines from three-component coupling of carbonyl compounds, amines, and methanol following reductive amination/N-methylation is reported for the first time. A wide array of substrates with tolerance of different functional groups was demonstrated. The protocol was extended to the synthesis of N-methyl containing pharmaceutically important drug molecules. A probable catalytic cycle was proposed based on various control experiments and different analytical techniques such as NMR, IR and ESI-MS.

Cyclometalated (NNC)Ru(II) complex catalyzed β-methylation of alcohols using methanol

Indolyl fragment containing phenanthroline based new ligands and their corresponding Ru(II) complexes were synthesized and fully characterized by various spectroscopic techniques. Catalytic activity of these newly synthesized cyclometalated (NNC)Ru(II) complexes...