Faculty Publications
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Item Condensation of malononitrile with salicylaldehydes and o-aminobenzaldehydes revisited: Solvent and catalyst free synthesis of 4H-chromenes and quinolines(Royal Society of Chemistry, 2012) Bhat, S.I.; Choudhury, A.R.; Trivedi, D.R.The reaction of malononitrile with salicylaldehyde under solvent and catalyst free conditions was re-investigated using mechanochemical mixing, thermal heating and a direct crystallization process. The resulting condensation product by all three types of molecular activation, was found to be (2-amino-3-cyano-4H-chromene-4-yl)malononitrile, which is not the previously reported benzofuran-2-carbonitrile. The structure of the resulting chromene derivative was confirmed by FT-IR, MS, 1H, 13C NMR and single crystal and powder X-ray diffraction. The reaction pathway under neat conditions (mechanochemical mixing) at ambient temperature was monitored by IR spectral measurements. The versatility of the current green protocol was examined through the reaction of eleven derivatives of o-hydroxybenzaldehyde with malononitrile to obtain 2-amino-3-cyano-4H-chromene derivatives. In addition, malononitrile was further reacted with o-aminobenzaldehydes under neat conditions to yield quinoline derivatives. © 2012 The Royal Society of Chemistry.Item Synthesis and characterization of thiophene-based donor-acceptor type polyimide and polyazomethines for optical limiting applications(2013) Vishnumurthy, K.A.; Sunitha, M.S.; Vasudeva Adhikari, A.V.In this communication we describe the design and synthesis of four new conjugated polymers (P1-P4) based on 3,4-ditetradecyloxythiophene. The required diamine monomer was prepared by a unique catalyst-free reduction process using hydrazine hydrate. The structures of the intermediates and polymers were established by FTIR, 1H NMR spectroscopy. Molecular weights of polymers were determined by gel permeation chromatographic (GPC) method. Their electrochemical properties were investigated by cyclic voltammetry and linear optical properties were determined by UV-Visible absorption and fluorescence emission spectroscopic techniques. Further, their nonlinear optical properties were evaluated by Z-scan technique using Nd:YAG laser. These polymers showed strong optical limiting behavior with two-photon absorption (2PA) coefficients of the order of 10-10 m/W, which are comparable to that of good optical limiting materials reported in the literature. Also, it has been observed that the optical nonlinearity enhanced with the increase in donor-acceptor strength of the polymer backbone. © 2012 Springer-Verlag.Item Fast and efficient synthesis of N-substituted ?-aminobutyric acids by grinding at room temperature(Springer Verlag, 2013) Bhat, S.I.; Trivedi, D.R.Green chemistry is gaining increasing interest due to the growing awareness of the chemical community for sustainable development. Green chemistry solutions include synthesis without solvent and catalyst because many solvents and catalysts are toxic and expensive. Herein, we report the solvent and catalyst free method for the synthesis of N-substituted derivatives of ?-aminobutyric acid by direct aza-Michael addition of amines to crotonic acid. The protocol involves simple mixing or grinding the reactants at room temperature. The ?-amino acid derivatives were obtained in 82-100 % yield with a short reaction time without any tedious workup procedures. Our findings thus reveal a promising alternative to previously used procedures. © 2013 Springer-Verlag Berlin Heidelberg.