Practical way to imidazo[4,5-b] and [4,5-c]pyridine-2-ones via cascade ureidation/palladium-catalyzed cyclization

Iodine-catalyzed oxidative functionalization of purines with (thio)ethers or methylarenes for the synthesis of purin-8-one analogues

An efficient oxidative functionalization of purine-like substrates with (thio)ethers or methylarenes under mild conditions is described. Using I2 as the catalyst, and TBHP as the oxidant, this protocol provides a valuable synthetic tool for the assembly of a wide range of 9-alkyl(benzyl)purin-8-one derivatives with high atom- and step-economy and exceptional functional group tolerance.

Tandem Catalysis: Synthesis of Nitrogen-Containing Heterocycles

In this Review, we consider all the publications since the beginning of the century that describe tandem reactions resulting in the formation of five-membered aromatic nitrogen heterocycles (thiazole, imidazole, indole, tetrazole, triazole, and isoxazole). The contents of this review are organized by taxonomy and type of tandem catalysis. It covers orthogonal, auto-, and assisted tandem catalysis, providing an overview of tandem reactions applied tonitrogen heterocycles reported in the literature up to March 2020. We believe that this compilation of data will provide a necessary starting reference to developthe applications of tandem catalysis in medicinal chemistry.

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

A comprehensive account of recent advances in the synthesis of imidazopyridines, assisted through transition-metal-catalyzed multicomponent reactions, C-H activation/functionalization and coupling reactions are highlighted in this review article. The basic illustration of this review comprises of schemes with concise account of explanatory text. The schemes depict the reaction conditions along with a quick look into the mechanism involved to render a deep understanding of the catalytic role. At some instances optimizations of certain features have been illustrated through tables, i.e., selectivity of catalyst, loading of the catalyst and percentage yield with different substrates. Each of the reported examples has been rigorously analyzed for reacting substrates, reaction conditions and transition metals used as the catalyst. This review will be helpful to the chemists in understanding the challenges associated with the reported methods as well as the future possibilities, both in the choice of substrates and catalysts. This review would be quite appealing to a wider range of organic chemists in academia and industrial R&D sectors working in the field of heterocyclic syntheses. In a nutshell, this review will be a guiding torch to envisage: (i) the role of various transition metals in the domain dedicated towards method development and (ii) for the modifications needed thereof in the R&D sector.

Transition-metal-free C-H amidation and chlorination: synthesis of N/N'-mono-substituted imidazopyridin-2-ones from N-pyridyl-N-hydroxylamine intermediates

Non-symmetric 1,3-substituted imidazopyridin-2-ones are a common structural scaffold found among many biologically active molecules. Herein we report an efficient, mild, and transition-metal free C-H amidation strategy to access such a pyrido-fused cyclic urea framework in good yields and with a broad functional group tolerance.

Acid-Promoted Cascade Reaction of N-(4-Chloroquinolin-3-yl)carbamates with Amines: One-Pot Assembly of Imidazo[4,5-c]quinolin-2-one

An acid-promoted cascade reaction of 4-chloroquinolin-3-yl carbamates with amines is described. This method achieves the formation of two new C-N bonds through an intermolecular amination/intramolecular cyclization reaction sequence. In combination with subsequent Suzuki coupling, this three-component telescopic procedure provides rapid access to various bioactive imidazo[4,5-c]quinolin-2-one derivatives.

Regioselective synthesis of benzimidazolones via cascade C-N coupling of monosubstituted ureas

A direct method for the regioselective construction of benzimidazolones is reported wherein a single palladium catalyst is employed to couple monosubstituted urea substrates with differentially substituted 1,2-dihaloaromatic systems. In this method, the catalyst is able to promote a cascade of two discrete chemoselective C–N bond-forming processes that allows the highly selective and predictable formation of complex heterocycles from simple, readily available starting materials.

Copper- and palladium-catalyzed amidation reactions for the synthesis of substituted imidazo[4,5-c]pyridines

Imidazo[4,5-c]pyridines were synthesized in three steps utilizing a palladium-catalyzed amidation/cyclization strategy. N-Aryl substrates were synthesized using copper-catalyzed amidation of 3-amino-N-Boc-4-chloropyridine. Complementary protocols for the selective chlorination of imidazo[4,5-c]pyridines at the C2 and C7 positions were also developed.