The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform
Bernd Goldfuss - One of the best experts on this subject based on the ideXlab platform.
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enantiopure methyl and Phenyllithium mixed carb anionic anisyl fencholate aggregates
Organometallics, 2019Co-Authors: Vanessa Grote, Jorgmartin Neudorfl, Bernd GoldfussAbstract:Methyl- and Phenyllithium aggregates with enantiopure anisyl fencholate units form after reaction of organolithium reagent with (+)-anisyl fenchol in hydrocarbon and some ethereal solvents. These carbanionic aggregates are characterized by X-ray crystal analyses and exhibit both 3:1 stoichiometry and distorted cubic Li4O3C1 cores, in which three lithium ions coordinate the carbanion (i.e., methylide or phenylide). These three lithium ions define a Lewis acidic surface (Li3), binding the carbanion and expanding with the steric demand of the carbanion (i.e., from Me: 2.62 A2, over n-Bu: 2.65 A2 (previous work) to Ph: 2.79 A2). Methylation and phenylation reactions of various prochiral aldehydes employing these methyllithium and Phenyllithium aggregates yield alcohols with up to 44% ee. To rationalize the formation of the mixed (carb-)anionic aggregates, aggregate formation energies, describing co-condensations of RLi (R = Me, Ph, n-Bu) and lithium fencholates, are computed for the 3:1 and 2:2 stoichiometrie...
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Enantiopure Methyl- and Phenyllithium: Mixed (Carb-)Anionic Anisyl Fencholate-Aggregates
2019Co-Authors: Vanessa Grote, Jörg-martin Neudörfl, Bernd GoldfussAbstract:Methyl- and Phenyllithium aggregates with enantiopure anisyl fencholate units form after reaction of organolithium reagent with (+)-anisyl fenchol in hydrocarbon and some ethereal solvents. These carbanionic aggregates are characterized by X-ray crystal analyses and exhibit both 3:1 stoichiometry and distorted cubic Li4O3C1 cores, in which three lithium ions coordinate the carbanion (i.e., methylide or phenylide). These three lithium ions define a Lewis acidic surface (Li3), binding the carbanion and expanding with the steric demand of the carbanion (i.e., from Me: 2.62 Å2, over n-Bu: 2.65 Å2 (previous work) to Ph: 2.79 Å2). Methylation and phenylation reactions of various prochiral aldehydes employing these methyllithium and Phenyllithium aggregates yield alcohols with up to 44% ee. To rationalize the formation of the mixed (carb-)anionic aggregates, aggregate formation energies, describing co-condensations of RLi (R = Me, Ph, n-Bu) and lithium fencholates, are computed for the 3:1 and 2:2 stoichiometries. These computed aggregate formation energies point to preferences for 3:1 over 2:2 aggregates, as it is also apparent from experimental aggregate formations, confirmed by X-ray crystal analyses. In close analogy to the X-ray crystal structures, the computed Li3 surfaces increase with increasing steric demand of the carbanions. The chiral, mixed (carb-)anionic RLi-fencholate aggregates hence adapt to different carbanion sized and arise not only with small (Me) or primary carbanions (n-Bu) but even with the larger secondary phenyl anion
Michael L Mckee - One of the best experts on this subject based on the ideXlab platform.
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density functional calculations of methyllithium t butyllithium and Phenyllithium oligomers effect of hyperconjugation on conformation
Journal of Physical Chemistry A, 2001Co-Authors: Ohyun Kwon, Michael L MckeeAbstract:Oligomers of methyllithium and tert-butyllithium (RnLin, n = 1−4; R = Me, t-Bu) as well as Phenyllithium (PhnLin, n = 1,4) have been studied by using density functional theory (DFT). Possible conformers of methyllithium and tert-butyllithium oligomers were optimized at the B3LYP/6-31+G* level, and relative energies were evaluated at the B3LYP/6-311+G(2d,p)+ZPC//B3LYP/6-31+G* level. Optimized geometric parameters of MeLi and t-BuLi tetramers are in good agreement with available experimental and previous computational results. Atomic charges from natural population analysis (NPA) indicate that Li−C bonds show dominant ionic character for methyl, tert-butyl, and Phenyllithium oligomers. Comparison of atomic charges among the oligomers indicates that lithium charges are almost independent of the size of the oligomer or the identity of the ligand. NBO second-order perturbation energy analyses for the Td geometries of methyllithium and tert-butyllithium tetramers indicate that the hyperconjugative interaction (...
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density functional calculations of methyllithium t butyllithium and Phenyllithium oligomers effect of hyperconjugation on conformation
Journal of Physical Chemistry A, 2001Co-Authors: Ohyun Kwon, Fatma Sevin And, Michael L MckeeAbstract:Oligomers of methyllithium and tert-butyllithium (RnLin, n = 1−4; R = Me, t-Bu) as well as Phenyllithium (PhnLin, n = 1,4) have been studied by using density functional theory (DFT). Possible confo...
Vanessa Grote - One of the best experts on this subject based on the ideXlab platform.
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enantiopure methyl and Phenyllithium mixed carb anionic anisyl fencholate aggregates
Organometallics, 2019Co-Authors: Vanessa Grote, Jorgmartin Neudorfl, Bernd GoldfussAbstract:Methyl- and Phenyllithium aggregates with enantiopure anisyl fencholate units form after reaction of organolithium reagent with (+)-anisyl fenchol in hydrocarbon and some ethereal solvents. These carbanionic aggregates are characterized by X-ray crystal analyses and exhibit both 3:1 stoichiometry and distorted cubic Li4O3C1 cores, in which three lithium ions coordinate the carbanion (i.e., methylide or phenylide). These three lithium ions define a Lewis acidic surface (Li3), binding the carbanion and expanding with the steric demand of the carbanion (i.e., from Me: 2.62 A2, over n-Bu: 2.65 A2 (previous work) to Ph: 2.79 A2). Methylation and phenylation reactions of various prochiral aldehydes employing these methyllithium and Phenyllithium aggregates yield alcohols with up to 44% ee. To rationalize the formation of the mixed (carb-)anionic aggregates, aggregate formation energies, describing co-condensations of RLi (R = Me, Ph, n-Bu) and lithium fencholates, are computed for the 3:1 and 2:2 stoichiometrie...
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Enantiopure Methyl- and Phenyllithium: Mixed (Carb-)Anionic Anisyl Fencholate-Aggregates
2019Co-Authors: Vanessa Grote, Jörg-martin Neudörfl, Bernd GoldfussAbstract:Methyl- and Phenyllithium aggregates with enantiopure anisyl fencholate units form after reaction of organolithium reagent with (+)-anisyl fenchol in hydrocarbon and some ethereal solvents. These carbanionic aggregates are characterized by X-ray crystal analyses and exhibit both 3:1 stoichiometry and distorted cubic Li4O3C1 cores, in which three lithium ions coordinate the carbanion (i.e., methylide or phenylide). These three lithium ions define a Lewis acidic surface (Li3), binding the carbanion and expanding with the steric demand of the carbanion (i.e., from Me: 2.62 Å2, over n-Bu: 2.65 Å2 (previous work) to Ph: 2.79 Å2). Methylation and phenylation reactions of various prochiral aldehydes employing these methyllithium and Phenyllithium aggregates yield alcohols with up to 44% ee. To rationalize the formation of the mixed (carb-)anionic aggregates, aggregate formation energies, describing co-condensations of RLi (R = Me, Ph, n-Bu) and lithium fencholates, are computed for the 3:1 and 2:2 stoichiometries. These computed aggregate formation energies point to preferences for 3:1 over 2:2 aggregates, as it is also apparent from experimental aggregate formations, confirmed by X-ray crystal analyses. In close analogy to the X-ray crystal structures, the computed Li3 surfaces increase with increasing steric demand of the carbanions. The chiral, mixed (carb-)anionic RLi-fencholate aggregates hence adapt to different carbanion sized and arise not only with small (Me) or primary carbanions (n-Bu) but even with the larger secondary phenyl anion
Ohyun Kwon - One of the best experts on this subject based on the ideXlab platform.
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density functional calculations of methyllithium t butyllithium and Phenyllithium oligomers effect of hyperconjugation on conformation
Journal of Physical Chemistry A, 2001Co-Authors: Ohyun Kwon, Michael L MckeeAbstract:Oligomers of methyllithium and tert-butyllithium (RnLin, n = 1−4; R = Me, t-Bu) as well as Phenyllithium (PhnLin, n = 1,4) have been studied by using density functional theory (DFT). Possible conformers of methyllithium and tert-butyllithium oligomers were optimized at the B3LYP/6-31+G* level, and relative energies were evaluated at the B3LYP/6-311+G(2d,p)+ZPC//B3LYP/6-31+G* level. Optimized geometric parameters of MeLi and t-BuLi tetramers are in good agreement with available experimental and previous computational results. Atomic charges from natural population analysis (NPA) indicate that Li−C bonds show dominant ionic character for methyl, tert-butyl, and Phenyllithium oligomers. Comparison of atomic charges among the oligomers indicates that lithium charges are almost independent of the size of the oligomer or the identity of the ligand. NBO second-order perturbation energy analyses for the Td geometries of methyllithium and tert-butyllithium tetramers indicate that the hyperconjugative interaction (...
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density functional calculations of methyllithium t butyllithium and Phenyllithium oligomers effect of hyperconjugation on conformation
Journal of Physical Chemistry A, 2001Co-Authors: Ohyun Kwon, Fatma Sevin And, Michael L MckeeAbstract:Oligomers of methyllithium and tert-butyllithium (RnLin, n = 1−4; R = Me, t-Bu) as well as Phenyllithium (PhnLin, n = 1,4) have been studied by using density functional theory (DFT). Possible confo...
Jorgmartin Neudorfl - One of the best experts on this subject based on the ideXlab platform.
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enantiopure methyl and Phenyllithium mixed carb anionic anisyl fencholate aggregates
Organometallics, 2019Co-Authors: Vanessa Grote, Jorgmartin Neudorfl, Bernd GoldfussAbstract:Methyl- and Phenyllithium aggregates with enantiopure anisyl fencholate units form after reaction of organolithium reagent with (+)-anisyl fenchol in hydrocarbon and some ethereal solvents. These carbanionic aggregates are characterized by X-ray crystal analyses and exhibit both 3:1 stoichiometry and distorted cubic Li4O3C1 cores, in which three lithium ions coordinate the carbanion (i.e., methylide or phenylide). These three lithium ions define a Lewis acidic surface (Li3), binding the carbanion and expanding with the steric demand of the carbanion (i.e., from Me: 2.62 A2, over n-Bu: 2.65 A2 (previous work) to Ph: 2.79 A2). Methylation and phenylation reactions of various prochiral aldehydes employing these methyllithium and Phenyllithium aggregates yield alcohols with up to 44% ee. To rationalize the formation of the mixed (carb-)anionic aggregates, aggregate formation energies, describing co-condensations of RLi (R = Me, Ph, n-Bu) and lithium fencholates, are computed for the 3:1 and 2:2 stoichiometrie...