The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
P K Dubey - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of tetrahedral diarylheptanoid ent-diospongin A and epimer-diospongin B by employing Julia–Kocienski olefination
Tetrahedron Letters, 2014Co-Authors: Suresh Babu Meruva, Vilas H. Dahanukar, Ramamohan Mekala, T.v. Pratap, Akula Raghunadh, U. K. Syam Kumar, P K DubeyAbstract:Total synthesis of ent-diospongin A and epimer-diospongin B has been accomplished in good yield with high optical purity. The key steps of diospongin synthesis involve Julia–Kocienski olefination, Weinreb amide formation, Grignard Reaction, reduction, acetonide deprotection, Lewis acid catalyzed cyclization, and Wacker oxidation.
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synthesis of tetrahedral diarylheptanoid ent diospongin a and epimer diospongin b by employing julia kocienski olefination
Tetrahedron Letters, 2014Co-Authors: Vilas H. Dahanukar, Ramamohan Mekala, T.v. Pratap, Suresh Babu Meruva, Akula Raghunadh, Raghavendra K Rao, U Syam K Kumar, P K DubeyAbstract:Total synthesis of ent-diospongin A and epimer-diospongin B has been accomplished in good yield with high optical purity. The key steps of diospongin synthesis involve Julia–Kocienski olefination, Weinreb amide formation, Grignard Reaction, reduction, acetonide deprotection, Lewis acid catalyzed cyclization, and Wacker oxidation.
Suresh Babu Meruva - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of tetrahedral diarylheptanoid ent-diospongin A and epimer-diospongin B by employing Julia–Kocienski olefination
Tetrahedron Letters, 2014Co-Authors: Suresh Babu Meruva, Vilas H. Dahanukar, Ramamohan Mekala, T.v. Pratap, Akula Raghunadh, U. K. Syam Kumar, P K DubeyAbstract:Total synthesis of ent-diospongin A and epimer-diospongin B has been accomplished in good yield with high optical purity. The key steps of diospongin synthesis involve Julia–Kocienski olefination, Weinreb amide formation, Grignard Reaction, reduction, acetonide deprotection, Lewis acid catalyzed cyclization, and Wacker oxidation.
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synthesis of tetrahedral diarylheptanoid ent diospongin a and epimer diospongin b by employing julia kocienski olefination
Tetrahedron Letters, 2014Co-Authors: Vilas H. Dahanukar, Ramamohan Mekala, T.v. Pratap, Suresh Babu Meruva, Akula Raghunadh, Raghavendra K Rao, U Syam K Kumar, P K DubeyAbstract:Total synthesis of ent-diospongin A and epimer-diospongin B has been accomplished in good yield with high optical purity. The key steps of diospongin synthesis involve Julia–Kocienski olefination, Weinreb amide formation, Grignard Reaction, reduction, acetonide deprotection, Lewis acid catalyzed cyclization, and Wacker oxidation.
Stephen Maldonado - One of the best experts on this subject based on the ideXlab platform.
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Wet chemical functionalization of III-V semiconductor surfaces: Alkylation of gallium arsenide and gallium nitride by a Grignard Reaction sequence
Langmuir : the ACS journal of surfaces and colloids, 2012Co-Authors: Sabrina L. Peczonczyk, Jhindan Mukherjee, Azhar I. Carim, Stephen MaldonadoAbstract:Crystalline gallium arsenide (GaAs) (111)A and gallium nitride (GaN) (0001) surfaces have been functionalized with alkyl groups via a sequential wet chemical chlorine activation, Grignard Reaction process. For GaAs(111)A, etching in HCl in diethyl ether effected both oxide removal and surface-bound Cl. X-ray photoelectron (XP) spectra demonstrated selective surface chlorination after exposure to 2 M HCl in diethyl ether for freshly etched GaAs(111)A but not GaAs(111)B surfaces. GaN(0001) surfaces exposed to PCl5 in chlorobenzene showed reproducible XP spectroscopic evidence for Cl-termination. The Cl-activated GaAs(111)A and GaN(0001) surfaces were both reactive toward alkyl Grignard reagents, with pronounced decreases in detectable Cl signal as measured by XP spectroscopy. Sessile contact angle measurements between water and GaAs(111)A interfaces after various levels of treatment showed that GaAs(111)A surfaces became significantly more hydrophobic following Reaction with CnH2n–1MgCl (n = 1, 2, 4, 8, 14,...
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Wet Chemical Functionalization of III–V Semiconductor Surfaces: Alkylation of Gallium Arsenide and Gallium Nitride by a Grignard Reaction Sequence
2012Co-Authors: Sabrina L. Peczonczyk, Jhindan Mukherjee, Azhar I. Carim, Stephen MaldonadoAbstract:Crystalline gallium arsenide (GaAs) (111)A and gallium nitride (GaN) (0001) surfaces have been functionalized with alkyl groups via a sequential wet chemical chlorine activation, Grignard Reaction process. For GaAs(111)A, etching in HCl in diethyl ether effected both oxide removal and surface-bound Cl. X-ray photoelectron (XP) spectra demonstrated selective surface chlorination after exposure to 2 M HCl in diethyl ether for freshly etched GaAs(111)A but not GaAs(111)B surfaces. GaN(0001) surfaces exposed to PCl5 in chlorobenzene showed reproducible XP spectroscopic evidence for Cl-termination. The Cl-activated GaAs(111)A and GaN(0001) surfaces were both reactive toward alkyl Grignard reagents, with pronounced decreases in detectable Cl signal as measured by XP spectroscopy. Sessile contact angle measurements between water and GaAs(111)A interfaces after various levels of treatment showed that GaAs(111)A surfaces became significantly more hydrophobic following Reaction with CnH2n–1MgCl (n = 1, 2, 4, 8, 14, 18). High-resolution As 3d XP spectra taken at various times during prolonged direct exposure to ambient lab air indicated that the resistance of GaAs(111)A to surface oxidation was greatly enhanced after Reaction with Grignard reagents. GaAs(111)A surfaces terminated with C18H37 groups were also used in Schottky heterojunctions with Hg. These heterojunctions exhibited better stability over repeated cycling than heterojunctions based on GaAs(111)A modified with C18H37S groups. Raman spectra were separately collected that suggested electronic passivation by surficial Ga–C bonds at GaAs(111)A. Specifically, GaAs(111)A surfaces reacted with alkyl Grignard reagents exhibited Raman signatures comparable to those of samples treated with 10% Na2S in tert-butanol. For GaN(0001), high-resolution C 1s spectra exhibited the characteristic low binding energy shoulder demonstrative of surface Ga–C bonds following Reaction with CH3MgCl. In addition, 4-fluorophenyl groups were attached and detected after Reaction with C6H4FMgBr, further confirming the susceptibility of Cl-terminated GaN(0001) to surface alkylation. However, the measured hydrophobicities of alkyl-terminated GaAs(111)A and GaN(0001) were markedly distinct, indicating differences in the resultant surface layers. The results presented here, in conjunction with previous studies on GaP, show that atop Ga atoms at these crystallographically related surfaces can be deliberately functionalized and protected through Ga–C surface bonds that do not involve thiol/sulfide chemistry or gas-phase pretreatments
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wet chemical functionalization of iii v semiconductor surfaces alkylation of gallium phosphide using a Grignard Reaction sequence
Langmuir, 2010Co-Authors: Jhindan Mukherjee, Sabrina L. Peczonczyk, Stephen MaldonadoAbstract:Single-crystalline gallium phosphide (GaP) surfaces have been functionalized with alkyl groups via a sequential Cl-activation, Grignard Reaction process. X-ray photoelectron (XP) spectra of freshly etched GaP(111)A surfaces demonstrated reproducible signals for surficial Cl after treatment with PCl(5) in chlorobenzene. The measured Cl content consistently corresponded to approximately a monolayer of coverage on GaP(111)A. In contrast, GaP(111)B surfaces treated with the same PCl(5) solution under the same conditions exhibited macroscale roughening and yielded XP spectra that showed irreproducible Cl surface content often below the limit of detection of the spectrometer. The Cl-activated GaP(111)A surfaces were reactive toward alkyl Grignard reagents. Sessile contact angle measurements between water and GaP(111)A after various levels of treatment showed that GaP(111)A surfaces became significantly more hydrophobic following Reaction with either CH(3)MgCl or C(18)H(37)MgCl. GaP(111)A surfaces reacted with C(18)H(37)MgCl demonstrated wetting properties consistent with surfaces modified with a dense layer of long alkyl chains. High-resolution C 1s XP spectra indicated that the carbonaceous species at GaP(111)A surfaces treated with Grignard reagents could not be ascribed solely to adventitious carbon. A shoulder in the C 1s XP spectra occurred at slightly lower binding energies for these samples, commensurate with the formation of Ga-C bonds. High-resolution P 2p XP spectra taken at various times during prolonged direct exposure to ambient laboratory air indicated that the resistance of GaP(111)A to surface oxidation was greatly enhanced after surface modification with alkyl groups. GaP(111)A samples that had been functionalized with C(18)H(37)- groups exhibited less than 0.1 nm of surface oxide after 7 weeks of continuous exposure to ambient air. GaP(111)A surfaces terminated with C(18)H(37)- groups were also used as platforms in Schottky heterojunctions with Hg. In comparison to freshly etched GaP(111)A, the alkyl-terminated GaP(111)A samples yielded current-voltage responses that were in accord with metal-insulator-semiconductor devices and indicated that this Reaction strategy could be used to alter rates of heterogeneous charge transfer controllably. The wet chemical surface functionalization strategy described herein does not involve thiol/sulfide chemistry or gas-phase pretreatments and represents a new synthetic methodology for controlling the interfacial properties of GaP and related Ga-based III-V semiconductors.
Harshali S. Khatod - One of the best experts on this subject based on the ideXlab platform.
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Application of Unusual Grignard Reaction for the Stereoselective Synthesis of Antidepressant Drug (R)-(–)-Venlafaxine
Synthesis, 2016Co-Authors: Subhash P. Chavan, Harshali S. KhatodAbstract:An enantioselective synthesis of antidepressant drug (R)-(–)-venlafaxine is accomplished as an application of recently explored unusual Grignard Reaction. An innovative method for the generation of chirality at extremely reactive benzylic center along with determination of absolute stereochemistry has been discussed. The key steps involved in the synthesis include Sharpless asymmetric dihydroxylation for the induction of chirality and an unusual Grignard Reaction.
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exploration of the diastereoselectivity in an unusual Grignard Reaction and its application towards the synthesis of styryl lactones 7 epi goniodiol and 8 epi goniodiol
RSC Advances, 2016Co-Authors: Subhash P. Chavan, Harshali S. Khatod, Kumar VankaAbstract:An unusual diastereoselective Grignard Reaction is explored, where the Grignard reagents are derived from 1,n-dihaloalkanes. A steric bias due to the presence of a quaternary centre adjacent to the acetonide ester at the benzylic position is responsible for the formation of an intramolecularly reduced product in almost quantitative yield. This steric hindrance is responsible for the diastereoselectivity observed with a variety of aromatic as well as aliphatic esters. The unusual Grignard Reaction furnishes long chain secondary alcohols possessing a terminal olefin, which are synthetically important intermediates. As an application of this method, the diastereoselective synthesis of styryl lactones viz. 7-epi-(+)-goniodiol (29) and 8-epi-(−)-goniodiol (30) has been achieved.
Chaojun Li - One of the best experts on this subject based on the ideXlab platform.
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transition metal free one pot synthesis of biaryls from Grignard reagents and substituted cyclohexanones
ChemInform, 2013Co-Authors: Feng Zhou, Marcoliver Simon, Chaojun LiAbstract:The new sequence to construct biaryls includes Grignard Reaction, dehydration, and oxidative aromatization affording products in a one-pot fashion is developed.
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transition metal free one pot synthesis of biaryls from Grignard reagents and substituted cyclohexanones
Chemistry: A European Journal, 2013Co-Authors: Feng Zhou, Marcoliver Simon, Chaojun LiAbstract:: A new strategy for the construction of biaryls by a transition-metal-free process is presented. A sequence of a Grignard Reaction, dehydration, and oxidative aromatization affords the desired products in a one-pot fashion.
