Deep Eutectic Solvents as Convenient Media for Synthesis of Novel Coumarinyl Schiff Bases and Their QSAR Studies

Abstract

Deep eutectic solvents, as green and environmentally friendly media, were utilized in the synthesis of novel coumarinyl Schiff bases. Novel derivatives were synthesized from 2-((4-methyl-2-oxo-2H-chromen-7-yl)oxy)acetohydrazide and corresponding aldehyde in choline chloride:malonic acid (1:1) based deep eutectic solvent. In these reactions, deep eutectic solvent acted as a solvent and catalyst as well. Novel Schiff bases were synthesized in high yields (65–75%) with no need for further purification, and their structures were confirmed by mass spectra, 1H and 13C NMR. Furthermore, their antioxidant activity was determined and compared to antioxidant activity of previously synthesized derivatives, thus investigating their structure–activity relationship utilizing quantitative structure-activity relationship QSAR studies. Calculation of molecular descriptors has been performed by DRAGON software. The best QSAR model (Rtr = 0.636; Rext = 0.709) obtained with three descriptors (MATS3m, Mor22u, Hy) implies that the pairs of atoms higher mass at the path length 3, three-dimensional arrangement of atoms at scattering parameter s = 21 Å−1, and higher number of hydrophilic groups (-OH, -NH) enhanced antioxidant activity. Electrostatic potential surface of the most active compounds showed possible regions for donation of electrons to 1,1-diphenyl-2-picryhydrazyl (DPPH) radicals.

QSAR Analysis for Antioxidant Activity of Dipicolinic Acid Derivatives

“…That implies that higher number hydrogens attached to the oxygen, nitrogen or sulphur atoms, positively influences on antioxidant activity, such as secondary nitrogen atoms in thiosemicarbazides (28)(29)(30)(31)(32)(33). This supports our recent findings that enhanced value of hydrophilic factor, which is related with number of -OH, -NH 2 , and >NH groups in molecule, is favourable for antioxidant activity of coumarinyl Schiff bases [35]. Also, it corresponds with previously statement about negative influence of enhanced number of tertial nitrogen atoms on antioxidant activity.…”

Biorenewable Deep Eutectic Solvent for Selective and Scalable Conversion of Furfural into Cyclopentenone Derivatives

“…The observed ability of DES to rapidly form the imine functionality when furfural is treated with a primary amine ( Table 2 , entries 11, 12) prompted us to exploit the reactivity of the free primary amino group in compound 1C . On the other hand, the synthesis of Schiff bases in DESs is also a well-known reaction [ 54 , 55 , 56 , 57 , 58 ]. Moreover, the protection and/or modification of the amino function of amino acids [ 59 , 60 , 61 , 62 , 63 ] are one of the most important issues in the synthesis of biologically active compounds and particularly in the synthesis of peptidomimetics [ 64 , 65 , 66 , 67 , 68 , 69 ].…”

Purification of motor fuels by means of extraction using deep eutectic solvent based on choline chloride and glycerol

“…By selecting a hydrogen bond donor or acceptor, one can directly affect the properties of DESs . Owing to their good properties, DESs have been applied in different research fields such as electrochemistry, catalytic reactions, materials preparation, molecular purification, etc., as well as in the production of environmentally friendly liquid fuels.…”