Browsing by Author "Choudhury, A.R."

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Condensation of malononitrile with salicylaldehydes and o-aminobenzaldehydes revisited: Solvent and catalyst free synthesis of 4H-chromenes and quinolines
(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.
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.
Dialect Recognition System Using Excitation Source Features
(Institute of Electrical and Electronics Engineers Inc., 2018) Choudhury, A.R.; Chittaragi, N.B.; Koolagudi, S.G.
This paper focuses on building an automatic dialect recognition system using excitation source features. Every spoken unit represents the unique articulatory configuration of the excitation source and the vocal tract system. This paper emphasis on exploring source information to capture dialectal cues over vocal tract information. Epochs representing the instants of maximum excitation of the vocal tract at the closure are used as source features. Additionally, strength and slope of epochs and instantaneous frequency features are extracted from zero frequency filtered signal. Further, 13 cepstral coefficients are derived from the LP residual to prepare feature vector. Two dialect datasets such as Kannada dataset with five prominent dialects and English dataset with nine dialects are used for evaluation of the significances explored features. Classification experiments are conducted with support vector machines designed with sequential minimal optimization (SMO-SVM) function. Performances are analyzed individually and in combinations. Obtained results have exhibited the existence of dialect information at excitation source information and complementary cues at vocal tract system. Â© 2018 IEEE.