Cu(II)-Promoted Cascade Synthesis of Fused Imidazo-Pyridine-Carbonitriles

Organic Base-Promoted C-N- and C-O-Coupled Domino Cyclization Strategy: Syntheses of Oxazine-6-ones and 4-Pyrimidinols

Oxazine-6-one and 4-pyrimidinol are two important frameworks in pharmaceutical production. Herein, we disclosed a simple, efficient, inexpensive organic base-promoted and additive-stimulated protocol for the syntheses of variably functionalized oxazine-6-ones and 4-pyrimidinols employing acetonitrile solvent under conventional heating conditions using an oil bath through C-N and C-O coupled domino steps. This simple practicable productive protocol utilizes easily producible cheap precursors, namely, benzimidates or benzamidines, with differently substituted dicyano-olefins, and it comprises step economy, robustness, and moisture insensitive conditions affording high yield that avoids the use of transition-metal catalysts, multistep with multicomponent strategy, and harsh reaction conditions involving hazardous chemicals. This method is scalable into gram-scale production with good yield.

Regioselective Access to 1,2,4-Triazole-Fused N-Heterocycle, Pyrrolo[1,2-a][1,2,4]triazolo[5,1-c]pyrazine, via Double Dehydrative Cyclizations

A highly efficient and regioselective approach to a novel 1,2,4-triazole-fused N-heterocyclic scaffold, pyrrolo[1,2-a][1,2,4]triazolo[3,4-c]pyrazine, was established by base-promoted reaction of pyrrole-2-carbonitrile-derived substrate with acyl hydrazide where domino double ring closures comprised of enamine formation, attack on nitrile, and cyclodehydration enabled sequential construction of pyrazine and 1,2,4-triazole ring systems with formation of three C-N bonds.

Visible/solar-light-driven thiyl-radical-triggered synthesis of multi-substituted pyridines

A light-triggered synthesis of thio-functionalized pyridines is demonstrated using γ-ketodinitriles, thiols, and eosin Y as the photocatalyst. The reaction proceeds via the selective attack on one of the cyano groups by an in situ generated thiyl radical. The reaction also proceeds with nearly equal efficiency using direct sunlight. Large-scale synthesis and a few useful synthetic transformations of the substituted pyridines are also performed.

The Renaissance of Organo Nitriles in Organic Synthesis

In the arena of functional group-oriented organic synthesis, the nitrile or cyano functionality is of immense importance. The presence of nucleophilic N -atom, π-coordinating ability of the triple bond, and electrophilic C-center imparts unique and interesting reactivity. Owing to the ability of the nitrile to transform into various other functional groups or intermediates, the chemistry is very rich and diverse. In particular, the involvement of nitrile in numerous organic reactions such as inter- or intramolecular alkyne insertion, [2 + 2 + 2] cycloaddition with alkynes, [3 + 2] cycloaddition with azides, [4 + 2] cycloaddition with diene allow the synthesis of many important carbocycles and heterocycles. Furthermore, the nitrile serves as a directing group in many C-H bond functionalization reactions to introduce diverse functionality and participate as a radical acceptor in radical cascade strategies to obtain a large variety of functional molecules. This review mainly focuses on the reactivity and diverse synthetic application of the nitrile including C-H bond functionalization, alkyne insertion, cycloaddition, and thermal or photochemical cascade strategy. The objective of the current review aims at bringing out the striking collection of various nitrile-triggered organic transformations.