Solvent-free and ‘on-water’ multicomponent assembling of salicylaldehydes, malononitrile and 3-methyl-2-pyrazolin-5-one: A fast and efficient route to the 2-amino-4-(1H-pyrazol-4-yl)-4H-chromene scaffold

A New and an Eco-Friendly Approach for the Construction of Multi-Functionalized Benzenes with Computational Studies

The new path chosen is more appropriate in the context of green chemistry. This research aims to construct 5,6,7,8-tetrahydronaphthalene-1,3-dicarbonitrile (THNDC) and 1,2,3,4-tetrahydroisoquinoline-6,8-dicarbonitrile (THIDC) derivatives via the cyclization of three easily obtainable reactants under an environmentally benign mortar and pestle grinding technique. Notably, the robust route offers an esteemed opportunity for the introduction of multi-substituted benzenes and ensures the good compatibility of bioactive molecules. Furthermore, the synthesized compounds are investigated using docking simulations with two representative drugs (6c and 6e) for target validation. The physicochemical, pharmacokinetic, drug-like properties (ADMET), and therapeutic friendliness characteristics of these synthesized compounds are computed.

One-Pot Solvent-Involved Synthesis of 5-O-Substituted 5H-Chromeno[2,3-b]pyridines

Chromeno[2,3-b]pyridines are substances demanded in medicinal and material chemistry. PASE (pot, atom, and step economy) and in particular one-pot approaches are key green chemistry techniques that are applied for the synthesis of heterocyclic compounds. In this case, the PASE approach was extended with 'component economy', as solvent was used also as reactant (solvent-involved reaction). This approach was adopted for the one-pot synthesis of previously unknown O-substituted 5-alkoxy-5H-chromeno[2,3-b]pyridines via two-step transformation, namely the reaction of salicylaldehydes and malononitrile dimer, with the subsequent addition of alcohol. The mechanistic studies revealed the possibility of concurrent reaction. The studies aided in optimizing the reaction conditions for the best yields (77-93%). Thus, the one-pot reaction proceeds efficient and quickly, and the work-up procedure (only simple filtering) is very convenient. The structure of synthesized chromeno[2,3-b]pyridines was confirmed by 2D NMR spectroscopy.

Catalyst-Solvent System for PASE Approach to Hydroxyquinolinone-Substituted Chromeno[2,3-b]pyridines Its Quantum Chemical Study and Investigation of Reaction Mechanism

The Pot, Atom, and Step Economy (PASE) approach is based on the Pot economy principle and unites it with the Atom and Step Economy strategies; it ensures high efficiency, simplicity and low waste formation. The PASE approach is widely used in multicomponent chemistry. This approach was adopted for the synthesis of previously unknown hydroxyquinolinone substituted chromeno[2,3-b]pyridines via reaction of salicylaldehydes, malononitrile dimer and hydroxyquinolinone. It was shown that an ethanol-pyridine combination is more beneficial than other inorganic or organic catalysts. Quantum chemical studies showed that chromeno[2,3-b]pyridines has potential for corrosion inhibition. Real time ¹H NMR monitoring was used for the investigation of reaction mechanism and 2-((2H-chromen-3-yl)methylene)malononitrile was defined as a key intermediate in the reaction.

A fast and efficient ‘on-solvent’ cascade assembling of salicylaldehydes and dimethylbarbituric acid into 5-(1,3-dimethyl-2,4-dioxo-1,3,4,5-tetrahydro-2H-chromeno[2,3-d]pyrimidin-5-yl)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-triones

A fast (15 min) and efficient cascade reaction of salicylaldehydes and 1,3-dimethylbarbituric acid in the presence ofp-TsOH as a catalyst furnishes substituted 5-(1,3-dimethyl-2,4-dioxo-1,3,4,5-tetrahydro-2H-chromeno[2,3-d]pyrimidin-5-yl)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-triones1a–h, containing both chromeno[2,3-d]pyrimidine and hexahydropyrimidine-2,4,6-trione pharmacologically active fragments, in 95–99% yields. This new procedure is characterized by the use of inexpensive reagents and a simple workup.

Multicomponent mechanochemical synthesis

Historically, the use of mechanochemical methods in synthesis has been almost negligible, but their perception by the synthetic community has changed in recent years and they are on their way to becoming mainstream. However, the hybridization of mechanochemical synthesis with methodologies designed to increase synthetic efficiency by allowing the generation of several bonds in a single operation has taken off only recently, but it already constitutes a very promising approach to sustainable chemistry. In this context, we provide in this Perspective a critical summary and discussion of the main known synthetic methods based on mechanochemical multicomponent reactions.

Pot, atom and step-economic (PASE) synthesis of medicinally relevant spiro[oxindole-3,4′-pyrano[4,3-b]pyran] scaffold

Fast (3 min) pot, atom and step economics (PASE) potassium fluoride catalyzed multicomponent reaction of isatins, malononitrile and 4-hydroxy-6-methyl-2H-pyran-2-one results in efficient formation of substituted spirooxindole-3,4′-pyrano[4,3-b]pyrans in 92–96% yields. The developed ‘on-solvent’ approach to the substituted spirooxindole-3,4′-pyrano[4,3-b]pyrans – the pharmacologically perspective substances with known antiviral, antileishmanial, anticonvulsant and anti-HIV activities – is beneficial from the viewpoint of diversity-oriented large-scale processes and represents fast and environmentally benign synthetic concept for the multicomponent reactions strategy.