Methodology of «green» Chemistry in the Synthesis of Substituted 2-Aminopyranes (Pyridine) -3-Carbonitrile

Abstract

Numerous studies in the chemistry of heterocyclic compounds today are devoted to solving environmental and economic problems (environmental pollution, irrational use of natural re-sources, etc.). This mini-review summarizes and analyzes the literature data of the last 10 years (2011-2021) on the «green» synthesis of structurally similar 2-aminopyrans (pyridine) -3-carboni-triles (polysubstituted, annelated with different types of articulation of rings, spirocyclic) contain-ing in the heteroring, substituent groups (functional analogs), identical in nature (CN, NH2) and position (at C2 -C3), are similar in production methods, formation routes. The main «green» ap-proach to the synthesis of 2-aminopyran (pyridine)-3-carbonitriles is multicomponent condensa-tion during thermal, ultrasonic, microwave activation, and electrolysis. Reagents in the synthesis of 2-aminopyran-3-carbonitriles are malononitrile, (di) carbonyl compounds (aromatic, alicyclic, aliphatic), phenols, hydroxynaphthols, in the case of 2-aminopyridine-3-carbonitriles -malonodi-nitrile, carbonyl compounds, aminating agents (ammonium acetate, aromatic and heterocyclic amines). Numerous studies devoted to the search for catalysts that can replace toxic catalysts (ali-phatic, heterocyclic amines), which are used repeatedly with the same effectiveness. Promising cat-alysts that meet these requirements have been found -nano-, nanomagnetic, organic, solid hetero-geneous catalysts (based on silicon oxide, titanium oxide, graphene). Much attention is paid to the selection of environmentally friendly solvents, available, cheap (water, ethanol), the use of ionic liquids. Electrochemical synthesis is recognized as «green» because toxic catalysts are replaced by electric current. A series of electrosynthesis reactions of annelated, spiro-fused, polyheteroatomi-cheterosystems obtained in the nanoscale range is presented. A large number of publications over the past decade have shown that the methodology of «green» chemistry provides a low-step, effi-cient, low-waste pathway for the synthesis of substituted 2-aminopyran (pyridine) -3-carbonitriles, which corresponds to the PASE (Pot-Atom-Step-Econiomic) principle. It should be noted that this path is not devoid of disadvantages, such as the use of expensive catalysts and complex hardware design. From a huge number of publications over the last decade on the synthesis of 2-aminopyran (pyridine) -3-carbonitriles, only those concerning the use of the methodology of «green» chemistry, the most significant and informative (21 publications) were selected.