Nucleophilicity—Periodic Trends and Connection to Basicity

Uggerud, Einar

doi:10.1002/chem.200500639

Cited by 71 publications

(78 citation statements)

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“…As already indicated by the insensitivity of the MCA values as a function of the underlying geometry there are little differences between the geometrical parameters collected in Table 2 3 and PH 3 are relevant to a larger data set was tested for the systems shown in Table 3. These now include strong, anionic nucleophiles such as NH 2 2 and OH 2 as well as weakly nucleophilic neutral systems such as HF and HCl. As a consequence the experimentally measured MCA values for these systems span a range of more than 1100 kJ/mol.…”

Section: Resultsmentioning

confidence: 99%

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Assessment of theoretical methods for the calculation of methyl cation affinities

et al. 2007

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The methyl cation affinity (MCA; 298 K) of a variety of neutral and anionic bases has been examined computationally with a wide variety of theoretical methods. These include high-level composite procedures such as W1, G3, G3B3, and G2, conventional ab initio methods such as CCSD(T) and MP2, as well as a selection of density functional theory (DFT) methods. Experimental results for a variety of small model systems are well reproduced with practically all these methods, and the performance of DFT based methods are far superior in comparison to their MP2 analogs for these small models. For larger model, systems including motifs frequently encountered in organocatalysts, the performance deteriorates somewhat for DFT methods, while it improves significantly for MP2, rendering the former methods unreliable for common organic bases. Thus, MP2 calculations performed in combination with basis sets such as 6-31+G(2d, p) or larger, appear to offer a practical and reliable approach to compute MCAs of organic bases.

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Section: Resultsmentioning

confidence: 99%

“…The performance of compound methods such as G2 6,7 or G2 (1) 8 has been found to be quite satisfactory, 2 despite the fact that these methods may not be ideally suited for larger systems.…”

Section: Introductionmentioning

confidence: 96%

Assessment of theoretical methods for the calculation of methyl cation affinities

et al. 2007

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“…[5] Thus, compound 3 corresponds to a condition in which the introduction of electropositive "nucleophile" and "nucleofuge", both being the SiMe 3 radical, alters the topography of the potential energy surface (PES). However, such PES topographies are quite common for P, S, or Si, which are well known to form stable pentacoordinate compounds.…”

Section: Introductionmentioning

confidence: 99%

Stable Pentacoordinate Carbocations: Structure and Bonding

Fernández

Uggerud

Frenking

2007

Chemistry A European J

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We report that only elements more electropositive than carbon (Group 13, 14, and Be) form stable symmetrical HnE--CH3--EHn + structures (E=Group 1, 2, 13, or 14 element) with a planar CH3 group symmetrically bonded to two EHn moieties, in analogy with prototypical SN2 transition structures. Analysis of the bonding situation of these pentacoordinate carbon molecules was studied by means of an energy decomposition analysis (EDA) of the interaction energy. This shows that HnE--CH3--EHn + molecules can be viewed as being composed of one CH3 group that is sigma-covalently bonded to two EHn groups forming a three-center, two-electron bond.

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“…6), is consistent with this latter mechanism, given that nucleophilicity generally mirrors basicity in aprotic solvents. 17 …”

Section: Resultsmentioning

confidence: 99%

Mitsunobu mischief: neighbor-directed histidine N(τ)-alkylation provides access to peptides containing selectively functionalized imidazolium heterocycles

Qian

Burke

2015

Org. Biomol. Chem.

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There are few methodologies that yield peptides containing His residues with selective N(π), N(π)-bis-alkylated imidazole rings. We have found that, under certain conditions, on-resin Mitsunobu coupling of alcohols with peptides having a N(π)-alkylated His residue results in selective and high-yield alkylation of the imidazole N(π) nitrogen. The reaction requires the presence of a proximal phosphoric, carboxylic or sulfonic acid, and proceeds through an apparent intramolecular mechanism involving Mitsunobu intermediates. These transformations have particular application to phosphopeptides, where “charge masking” of one phosphoryl anionic charge by the cationic histidine imidazolium ion is now possible. This chemistry opens selective access to peptides containing differentially functionalized imidazolium heterocycles, which provide access to new classes of peptides and peptide mimetics.

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Nucleophilicity—Periodic Trends and Connection to Basicity

Cited by 71 publications

References 71 publications

Assessment of theoretical methods for the calculation of methyl cation affinities

Assessment of theoretical methods for the calculation of methyl cation affinities

Stable Pentacoordinate Carbocations: Structure and Bonding

Mitsunobu mischief: neighbor-directed histidine N(τ)-alkylation provides access to peptides containing selectively functionalized imidazolium heterocycles

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