Current Green Chemistry - Volume 5, Issue 1, 2018

Due to an increasing pressure on the chemical society to consider environmental aspects of chemical production, the development of sustainable methodologies has been in the focus of research for years. Ionic Liquids (ILs) have numerous favorable properties: outstanding chemical, thermal and electrochemical stability, non-flammability, negligible volatility, excellent solvation ability and great variability of cation-anion pairs and structure that render them useful materials in green reactions. In pharmaceutics, they may find wide application in the synthesis, extraction and purification of bioactive compounds or may serve as pharmaceutical ingredients themselves. The review focusses on the use of ILs in the synthesis of pharmaceutically active compounds as reaction media, catalyst or catalyst support. ILs can be the efficient solvents as they are known to stabilize reactive intermediates, besides, they facilitate catalyst reuse in e. g. transition metal-catalyzed reactions. Acidic or basic ILs may serve as recyclable catalysts themselves. Other representatives may contain functional groups enabling their application as organocatalysts. Immobilization of catalytically active species on a Supported Ionic Liquid Phase (SILP) as solid material may further enhance catalytic efficiency. The review shows examples for the application of the methodologies mentioned above in the synthesis of biologically active molecules.

Nitrogen-containing heteroaromatics are commonly found in biologically active natural products, pharmaceuticals, agrochemicals, and functional materials. Naturally, this has resulted in such heterocycles being popular synthetic targets for many research groups around the world with numerous methodologies developed for their formation. The preparation of nitrogen-containing heteroaromatics by using various one-pot strategies has lately become more popular due to the increased focus on minimizing waste and cutting back on experimental operations. This review will highlight some of the most recent one-pot strategies used in order to assemble nitrogen containing heteroaromatics with particular emphasis on methodologies leading to the preparation of pyrroles, pyridines, indoles, quinolone, isoquinoline, and imidazo[1,2-a]pyridine.

A mild, efficient and environmentally benign method is adopted in the synthesis of aryl bis(heterocyclyl)methanes in water over mesoporous zirconium phosphate. The catalyst has been prepared following surfactant templated EISA (Evaporation Induced Self Assembly) method. The catalytic applications of mesoporous zirconium phosphate have been limited in organic multicomponent synthesis. It involves the condensation of various aromatic aldehydes with different active heterocycles like 4-hydroxycoumarin, pyrazolones and indole affording the corresponding product in high yield within a short time. The catalyst was reused several times without much change in the activity.

Biomass conversion strategies have been taking hold of the scientific community agenda in the evolution of renewable chemical and energy industries. Nonetheless, biomass conversion yet presents challenges due to its structural complexity and high reactivity of the oxygen functionalities. This review aims to point out the main encountered difficulties in the conversion of plant-derived feedstocks and by-products/waste, with a focus on catalytic approaches and efforts of the NanoVal research group into contributing to a potential future bio-based economy.

Microwave (MW) irradiation has had a positive impact also on organophosphorus chemistry. This is demonstrated in this minireview via the synthesis of phosphinates from phosphinic acids. The scope and limitations of the use of the MW technique, along with the modeling of the distribution of the beneficial effect of the local overheatings and the prediction of the acceleration is discussed. All these are possible on the basis of the energetics calculated for a selected esterification by quantum chemical methods. The model reaction of this study is the esterification of 1-hydroxy-3-methyl-3- phospholene 1-oxide with butanol.