Current Green Chemistry - Volume 5, Issue 3, 2018

Thermosetting resins take an important position in the polymer field, while they rely on limited and rapidly depleting fossil resources. Vanillin is currently the only industrialized bio-based monomer with benzene ring from renewable and abundant lignin. In this paper, the need for developing vanillin-derived thermosets as well as a summary of research progress is presented. Vanillinderived thermosets are divided into several categories including epoxy resins, benzoxazines, phenolic resins, methacrylates and other thermosets. Synthetic routes and the properties of the vanillin-derived thermosets are described. Finally, conclusions and outlooks are highlighted.

Natural product modified organocatalysts have gained attention due to their environmentally benign and biodegradable nature and as a result, these are now becoming powerful tools for the construction of simple to complex molecules with new concepts and designs. In the recent past, Camphorsulfonic Acid (CSA) has gained considerable attention as an efficient organocatalyst for the synthesis of various organic scaffolds with potential pharmacological interest. Camphorsulfonic acid (or Reychler’s acid) is inexpensive, commercially available, stable, non-toxic, reusable organocatalyst which can catalyze a variety of organic transformations such as many multi-component reactions, organic named reactions and the synthesis of various biologically promising heterocyclic compounds. The present review summarizes the camphorsulfonic acid-catalyzed synthesis of bioactive heterocycles reported so far.

Nowadays, Green Analytical Chemistry (GAC) idea is of high importance, with impact on the rapid growth in the sample preparation area with special emphasis on sample preparation simplification, miniaturization and automation. Due to the fact that GAC is of high importance today, this study is focused on the evaluation of green sample preparation techniques for organic compounds. It is well known that sample preparation is considered a crucial part of analytical procedures, particularly in samples characterized by complex matrices composition. The parameter of “greenness” is as important as selectivity in order to avoid using harmful organic solvents in sustainable extraction techniques. These solvents can generate hazardous, toxic waste while consuming large resources volume, thus, developing new, eco-friendly and benign solvents which would meet technological and economic demands is perhaps the most popular aspects of Green Chemistry. Some examples of these “green” solvents are given in this work. In addition, several new miniaturized extraction techniques are described. Here you can highlight Solid Phase Microextraction (SPME) and Liquid Phase Microextraction (LPME). However, the best option would be to use direct methods of analysis, where sample preparation is not required. The given study also shows the possibilities and limitations of using Eco-Scale and GAPI tools for the assessment of the green character of selected analytical procedures. Both tools were applied to assess 9 different analytical procedures and both showed similar results presented in a different manner.

Background: Bis(indolyl)methane, indole and their derivatives are known as vital intermediates in the pharmaceutical chemistry and organic synthesis which exhibits a range of physiological properties. Bis(indolyl)methanes are found in cruciferous plants and are well known to promote beneficial estrogen metabolism and induce apoptosis in human cancer cells. Bis(indolyl)methanes have received much attention in recent years. A major source of waste in the (fine) chemicals industry is derived from the widespread use of liquid mineral acids (HF, H2SO4) and a variety of Lewis acids. They cannot be easily recycled and generally end up as waste containing large amounts of inorganic salts. Their widespread replacement by recyclable solid acids such as malic acid, tartaric acid and malonic acid etc., which are naturally occurring, would afford a dramatic reduction in waste. Thus there is need to find out green protocols for the synthesis of bioactive molecules. Objective: To develop green protocol for the synthesis of bisindolylmethane derivatives. Methods: Bisindolylmethane derivatives were synthesized in 85-95 % by using ultrasonication technique in presence of malic acid as an organocatalyst in water as a green solvent at ambient reaction condition. Results: We have demonstrated that malic acid can be used as a benign organocatalyst for organic transformations with high efficacy and excellent reusability. Conclusion: In conclusion, we have developed ultrasonically assisted malic acid catalyzed metal free green protocol for the bis(indolyl)methanes under homogenous conditions. The notable advantages of this method are the use of water as a green solvent, efficient eco-friendly and inexpensive catalyst, ambient temperature and high reusability of the catalyst. Therefore, this protocol can be a promising alternative to the use of Lewis and mineral acid catalysed organic reactions. Further studies of exploiting the efficiency of naturally occurring acids as a green catalyst in synthesis of various heterocyclic compounds are in progress.

Synthesis of polyphosphoesters was accomplished under microwave irradiation by direct esterification or transesterification of phosphonic compounds (acids or esters) in reaction with polyethylene glycol having different molar masses. The polyphosphoesters were characterized by IR and 1H-NMR spectral data. Gel Permeation Chromatography (GPC) with an Evaporative Light Scattering Detector was used to determine the molar weights. The highest molecular weight was ∼8000.

Room temperature ionic liquids 1−butyl−3−methylimidazolium bromide, 1−butyl−3−methylimidazolium hexafluorophosphate, 1−butyl−3−methylimidazolium tetrafluoroborate, N−butylpyridinium bromide, N−butylpyridinium hexafluorophosphate, N−butylpyridinium tetrafluoroborate, and sponge ionic liquids N−cetylpyridinium bromide and N−cetylpyridinium tetrafluoroborate have been used as solvents and working catalysts for the synthesis of 2−amino−4−arylthiazole compounds. All the final compounds were characterized using FT−IR, NMR (1H and 13C), and mass spectral studies, while thermal stability and the corrected melting temperature of the synthesized compounds along with sponge ionic liquids was verified by performing thermal gravimetric analysis and differential scanning calorimetric analysis. Special emphasis has been laid to comprehend the mechanism of the catalytic action of ionic liquids alone as well as in the presence of organic solvents such as dimethyl sulfoxide, and ethanol.