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R R Rajawinslin - One of the best experts on this subject based on the ideXlab platform.
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n bromosuccinimide mediated thiocyanation of cyclohexene fused isoxazoline n oxides
Asian Journal of Organic Chemistry, 2016Co-Authors: Sachin S Ichake, R R Rajawinslin, Veerababurao Kavala, Bharath Kumar Villuri, Hueiting YangAbstract:An efficient, metal-free, NBS-mediated thiocyanation protocol has been developed for the synthesis of (6-(hydroxyimino)-2-thiocyanatocyclohex-1-en-1-yl)(phenyl)methanone derivatives from cyclohexene-fused isoxazoline N-oxides under mild conditions. This rapid, one-pot transformation is achieved in acetonitrile, and provides access to diverse SCN-containing compounds beaRing a wide range of functional groups in good to excellent yields. Moreover, an SCN containing product was further utilized for the synthesis of Cyclohexanone Ring-fused isothiazole derivatives.
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selectfluor mediated one pot synthesis of Cyclohexanone Ring fused isoxazole derivatives
ChemInform, 2015Co-Authors: R R Rajawinslin, Mustafa J Raihan, Donala Janreddy, Veerababurao Kavala, Mei Ling Chen, Chiu Hui HeAbstract:The one-pot, two-step conversion of isoxazoline-N-oxides (I) to title compounds (II) is described.
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selectfluor mediated one pot synthesis of Cyclohexanone Ring fused isoxazole derivatives
Tetrahedron, 2014Co-Authors: R R Rajawinslin, Mustafa J Raihan, Donala Janreddy, Veerababurao Kavala, Mei Ling Chen, Chiu Hui HeAbstract:Abstract A Selectfluor and base mediated protocol for the synthesis of Cyclohexanone Ring fused isoxazole derivatives from isoxazoline N-oxides has been successfully developed. This rapid, one-pot, two-step transformation is achieved in acetonitrile, through nitroso intermediate followed by hydration, defluorination and N–O coupling in the presence of triethylamine. The scope and mechanism of the protocol have been demonstrated.
Wenwei Lin - One of the best experts on this subject based on the ideXlab platform.
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expanding the scope of primary amine catalysis stereoselective synthesis of indanedione fused 2 6 disubstituted trans spiroCyclohexanones
Journal of Organic Chemistry, 2016Co-Authors: Madhusudhan G Reddy, Kai Hong Hsieh, Chia Jui Lee, Utpal Das, Wenwei LinAbstract:A cinchona-alkaloid-derived chiral primary-amine-catalyzed enantioselective method for the synthesis of the thermodynamically less stable indanedione-fused 2,6-trans-disubstituted spiroCyclohexanones is demonstrated. Both the enantiomeric forms of the trans isomer are obtained in excellent yields and enantioselectivities. Furthermore, one of the enantiopure trans-spiranes beaRing an additional α-substitution on the Cyclohexanone Ring was then epimerized into its thermodynamically stable cis counterpart, with little loss of enantioselectivity to demonstrate the feasibility of such a transformation. Mechanistic investigations revealed two competing pathways, a concerted Diels–Alder reaction and a stepwise Michael addition, for the formation of corresponding products.
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Expanding the Scope of Primary Amine Catalysis: Stereoselective Synthesis of Indanedione-Fused 2,6-Disubstituted trans-SpiroCyclohexanones
2016Co-Authors: Madhusudhan G Reddy, Kai Hong Hsieh, Chia Jui Lee, Utpal Das, Wenwei LinAbstract:A cinchona-alkaloid-derived chiral primary-amine-catalyzed enantioselective method for the synthesis of the thermodynamically less stable indanedione-fused 2,6-trans-disubstituted spiroCyclohexanones is demonstrated. Both the enantiomeric forms of the trans isomer are obtained in excellent yields and enantioselectivities. Furthermore, one of the enantiopure trans-spiranes beaRing an additional α-substitution on the Cyclohexanone Ring was then epimerized into its thermodynamically stable cis counterpart, with little loss of enantioselectivity to demonstrate the feasibility of such a transformation. Mechanistic investigations revealed two competing pathways, a concerted Diels–Alder reaction and a stepwise Michael addition, for the formation of corresponding products
Veerababurao Kavala - One of the best experts on this subject based on the ideXlab platform.
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n bromosuccinimide mediated thiocyanation of cyclohexene fused isoxazoline n oxides
Asian Journal of Organic Chemistry, 2016Co-Authors: Sachin S Ichake, R R Rajawinslin, Veerababurao Kavala, Bharath Kumar Villuri, Hueiting YangAbstract:An efficient, metal-free, NBS-mediated thiocyanation protocol has been developed for the synthesis of (6-(hydroxyimino)-2-thiocyanatocyclohex-1-en-1-yl)(phenyl)methanone derivatives from cyclohexene-fused isoxazoline N-oxides under mild conditions. This rapid, one-pot transformation is achieved in acetonitrile, and provides access to diverse SCN-containing compounds beaRing a wide range of functional groups in good to excellent yields. Moreover, an SCN containing product was further utilized for the synthesis of Cyclohexanone Ring-fused isothiazole derivatives.
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selectfluor mediated one pot synthesis of Cyclohexanone Ring fused isoxazole derivatives
ChemInform, 2015Co-Authors: R R Rajawinslin, Mustafa J Raihan, Donala Janreddy, Veerababurao Kavala, Mei Ling Chen, Chiu Hui HeAbstract:The one-pot, two-step conversion of isoxazoline-N-oxides (I) to title compounds (II) is described.
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selectfluor mediated one pot synthesis of Cyclohexanone Ring fused isoxazole derivatives
Tetrahedron, 2014Co-Authors: R R Rajawinslin, Mustafa J Raihan, Donala Janreddy, Veerababurao Kavala, Mei Ling Chen, Chiu Hui HeAbstract:Abstract A Selectfluor and base mediated protocol for the synthesis of Cyclohexanone Ring fused isoxazole derivatives from isoxazoline N-oxides has been successfully developed. This rapid, one-pot, two-step transformation is achieved in acetonitrile, through nitroso intermediate followed by hydration, defluorination and N–O coupling in the presence of triethylamine. The scope and mechanism of the protocol have been demonstrated.
I. Hubert Joe - One of the best experts on this subject based on the ideXlab platform.
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Molecular structure and vibrational spectra of 2,6-bis(benzylidene)Cyclohexanone: a density functional theoretical study.
Spectrochimica acta. Part A Molecular and biomolecular spectroscopy, 2010Co-Authors: D. Sajan, K. Udaya Lakshmi, Yusuf Erdogdu, I. Hubert JoeAbstract:Abstract The near-infrared Fourier transform (NIR-FT) Raman and Fourier transform infrared (FT-IR) spectral analyses of 2,6-bis(benzylidene)Cyclohexanone (BBC) molecule, a potential drugs for the treatment of P388 leukemia cells, were carried out along with density functional computations. The optimized geometry of BBC using density functional theory shows that the energetically favored chair conformation is not observed for central Cyclohexanone Ring and is found to possess a nearly ‘half chair’ conformation and shows less expansion of the angles and more rotation about the bonds. The existence of intramolecular C–H⋯O improper, blue-shifted hydrogen bond was investigated by means of the NBO analysis. The loweRing of carbonyl stretching vibration can be attributed to the mesomeric effect and the π-orbital conjugation induced by the unsaturation in the α-carbon atoms and co-planarity of the (–CH C–(C O)–C CH–) group.
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NBO analysis and vibrational spectra of 2,6-bis(p-methyl benzylidene Cyclohexanone) using density functional theory.
Spectrochimica acta. Part A Molecular and biomolecular spectroscopy, 2009Co-Authors: L. Padmaja, C. Ravikumar, M. Amalanathan, I. Hubert JoeAbstract:Abstract Vibrational analysis of the 2,6-bis(p-methyl benzylidene Cyclohexanone) [PMBC] compound was carried out by using NIR FT-Raman and FT-IR spectroscopic techniques. The equilibrium geometry, various bonding features and harmonic vibrational frequencies of PMBC have been investigated with the help of B3LYP/6-31G(d) density functional theory method. The optimized geometry clearly demonstrates Cyclohexanone Ring chair conformation is changed into half-chair conformation. The shortening of C–H bond length and blue shifting of the CH stretching wavenumber suggest the existence of improper weak C–H⋯O hydrogen bonding, which is confirmed by the natural bond orbital analysis. The Mulliken population analysis on atomic charges and the HOMO–LUMO energy are also calculated.
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Vibrational spectral analysis of 2,6 Bis (p-methoxy benzylidene) Cyclohexanone using density functional theory
Journal of Computational Methods in Sciences and Engineering, 2008Co-Authors: J. Binoy, A. Amal Raj, R. Reghunathan, I. Hubert Joe, V. S. JayakumarAbstract:The geometry optimization and the computation of vibrational wavenumbers have been carried out for 2,6 Bis (p-methoxy benzylidene) Cyclohexanone using density functional theory at B3LYP/6-31G(d) level. The optimized geometry reveals that the central Cyclohexanone Ring possesses a nearly 'half chair' conformation. The steric interaction causes the twisting of phenyl Rings and the twisting of both Ph1 and Ph2 are energetically favored by 6.66 kJ mol$^{-1}$ and 6.86 kJ mol$^{-1}$ respectively. The relaxed PES scan studies have been conducted to expose the changes in the geometrical parameters caused by Ring twisting. The stretching vibrational modes involving aromatic hydrogen atoms participating in steric interaction have been observed to possess higher vibrational wavenumbers. The unusual loweRing of C=O stretching vibrational wavenumber has been noticed, attributable to the mesomeric interaction of the group -CH=C-(C=O)-C=CH-. The methylene groups involving steric interaction have been found to possess different spectral behavior compared to free CH$_{2}$ groups. The computed geometry and vibrational spectrum of Cyclohexanone at B3LYP/6-31G(d) level have been used to analyze, the spectral distinction between chaired Cyclohexanone and half chaired central Cyclohexanone Ring in BMBC and also the bond angle effect and conjugation effects on carbonyl stretching modes.
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Quantum Chemical Computations and Spectral Investigation of 2, 6-Bis (P-Methyl Benzylidene Cyclohexanone)
AIP Conference Proceedings, 2008Co-Authors: M. Amalanathan, V. S. Jayakumar, C. Ravikumar, L. Padmaja, I. Hubert JoeAbstract:Cyclohexanone is s a non polar solvent, Cyclohexanone and its derivatives having numerous applications in the pharmaceutical and agrochemical industries. The vibrational analysis of the 2, 6‐bis (p‐methyl benzylidene Cyclohexanone) compound was carried out by using NIR FT‐Raman and FT‐IR spectroscopy. Ab initio molecular computation was performed at HF/6‐31G(d) level to derive equilibrium geometry, vibrational wavenumbers, intensities and first hyperpolarizability. Cyclohexanone Ring chair form is change into half chair is due to overlap of II‐orbitals from the optimized structure and the non bonded hydrogen shows the steric repulsion. The experimental wavenumbers are very close to the spectral data.
Walter Thiel - One of the best experts on this subject based on the ideXlab platform.
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quantum mechanical molecular mechanical study on the enantioselectivity of the enzymatic baeyer villiger reaction of 4 hydroxyCyclohexanone
Journal of Physical Chemistry B, 2013Co-Authors: Iakov Polyak, Manfred T Reetz, Walter ThielAbstract:We report a combined quantum mechanical/molecular mechanical (QM/MM) study of the effect of mutations of the Phe434 residue in the active site of Cyclohexanone monooxygenase (CHMO) on its enantioselectivity toward 4-hydroxyCyclohexanone. In terms of our previously established model of the enzymatic Baeyer–Villiger reaction, enantioselectivity is governed by the preference toward the equatorial ((S)-selectivity) or axial ((R)-selectivity) conformation of the substituent at the C4 carbon atom of the Cyclohexanone Ring in the Criegee intermediate and the subsequent rate-limiting transition state for migration (TS2). We assess the enantiopreference by locating all relevant TS2 structures at the QM/MM level. In the wild-type enzyme we find that the axial conformation is energetically slightly more stable, thus leading to a small excess of (R)-product. In the Phe434Ser mutant, there is a hydrogen bond between the serine side chain and the equatorial substrate hydroxyl group that is retained duRing the whole rea...
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Quantum Mechanical/Molecular Mechanical Study on the Enantioselectivity of the Enzymatic Baeyer–Villiger Reaction of 4-HydroxyCyclohexanone
The journal of physical chemistry. B, 2013Co-Authors: Iakov Polyak, Manfred T Reetz, Walter ThielAbstract:We report a combined quantum mechanical/molecular mechanical (QM/MM) study of the effect of mutations of the Phe434 residue in the active site of Cyclohexanone monooxygenase (CHMO) on its enantioselectivity toward 4-hydroxyCyclohexanone. In terms of our previously established model of the enzymatic Baeyer–Villiger reaction, enantioselectivity is governed by the preference toward the equatorial ((S)-selectivity) or axial ((R)-selectivity) conformation of the substituent at the C4 carbon atom of the Cyclohexanone Ring in the Criegee intermediate and the subsequent rate-limiting transition state for migration (TS2). We assess the enantiopreference by locating all relevant TS2 structures at the QM/MM level. In the wild-type enzyme we find that the axial conformation is energetically slightly more stable, thus leading to a small excess of (R)-product. In the Phe434Ser mutant, there is a hydrogen bond between the serine side chain and the equatorial substrate hydroxyl group that is retained duRing the whole rea...
