Methyl transfers. 14. Nucleophilic catalysis of nucleophilic substitution

McCortney, Bridget A.; Jacobson, Barry M.; Vreeke, M.; Lewis, Edward S.

doi:10.1021/ja00165a046

Cited by 27 publications

(13 citation statements)

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“…Interestingly, there was no significant difference in DS Et3N among the products ofentries 3and5-7, demonstrating that the highest DS 0.58 could be achieved with at the lowest TEA/AGU (20 equiv. per AGU, 80°C, 24 h).Since iodide is superior to bromide as a leaving group, we added sodium iodide (5 equiv./AGU) during the reaction of 6-bromo-6-deoxycurdlan with triethylamine under the same reaction conditions, in order to generate the 6-iodo product in situ in hopes of capture by TEA as it was generated, potentially affording higher DS Et3N (McCortney, Jacobson, Vreeke & Lewis, 1990). Based on (Fig.…”

Section: Resultsmentioning

confidence: 99%

Regioselective synthesis of cationic 6-deoxy-6-(N,N,N-trialkylammonio)curdlan derivatives

Zhang

Liu

Edgar

2016

Carbohydrate Polymers

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Curdlan, a bioactive β-1,3-glucan, is of intense interest for pharmaceutical and biomedical applications. Cationic derivatives of curdlan and other polysaccharides are especially attractive for their potential to interact in controlled fashion with proteins, among many other possible applications, but relatively few methods exist for their synthesis. Herein we report a regioselective method for preparation of cationic, water-soluble 6-(N,N,N-trialkylammonio)-6-deoxycurdlan salts by reaction of 6-bromo-6-deoxycurdlan and its 2,4-O-diesters with trialkylamines. Dimethyl sulfoxide was identified as the optimal solvent for this nucleophilic displacement to produce cationic curdlan derivatives (80 °C, 24h), providing maximum degree of triethylammonium substitution (DS) of 0.89, exclusively at the C-6 position. 6-Bromo-6-deoxycurdlan was also reacted with heterocyclic amines such as pyridine and imidazole, providing ammonium-substituted curdlan derivatives with substantial DS (0.66 and 0.86, respectively). The new combination of regioselective Furuhata bromination and bromine displacement under optimized conditions with tertiary amines provides access to quaternized curdlan derivatives that possess high, permanent positive charge and are readily water-soluble, properties that indicate potential application promise including for mucoadhesion, permeation enhancement, and delivery of genes and anionic drugs. Regioselectivity and DS of those curdlan ammonium derivatives were quantified by means of (1)H NMR, (13)C NMR and FTIR spectroscopic methods and by elemental analysis.

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Section: Resultsmentioning

confidence: 99%

Regioselective synthesis of cationic 6-deoxy-6-(N,N,N-trialkylammonio)curdlan derivatives

Zhang

Liu

Edgar

2016

Carbohydrate Polymers

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“…This consideration led us to target the orthophenylene derivative [1] 2 + ,w hich features two Lewisa cidic antimony sites predisposedt oi nteract withi ncoming nucleophiles. Distibonium salts [1][OTf] 2 and [1][BF 4 ] 2 could be conveniently generated by treatment of o-phenylene-bis(diphenylstibine) [10] [11] and [Ph 3 MeSb][BF 4 ], [12] which have both been previously described.…”

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confidence: 99%

Promoting the Hydrosilylation of Benzaldehyde by Using a Dicationic Antimony‐Based Lewis Acid: Evidence for the Double Electrophilic Activation of the Carbonyl Substrate

Hirai

Cho

Gabbaı̈

2016

Chemistry A European J

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The concomitant activation of carbonyl substrates by two Lewis acids has been investigated by using [1,2-(Ph2 MeSb)2 C6 H4 ](2+) ([1](2+) ), an antimony-based bidentate Lewis acid obtained by methylation of the corresponding distibine. Unlike the simple stibonium cation [Ph3 MeSb](+) , dication [1](2+) efficiently catalyzes the hydrosilylation of benzaldehyde under mild conditions. The catalytic activity of this dication is correlated to its ability to doubly activate the carbonyl functionality of the organic substrate. This view is supported by the isolation of [1-μ2 -DMF][OTf]2 , an adduct, in which the DMF oxygen atom bridges the two antimony centers.

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“…The isolation of products was Table 1 Activation (G a ) and total (DG z ) free energies for the demethylation of the SMe 2 group in metallacarboranes [(9-SMe 2 -7, 8 THF (2 ml) was added to a mixture of 1a or 1b (0.10 mmol) and CpTl (32 mg, 0.12 mmol), and the reaction was stirred overnight. The reaction mixture was filtered, the solvent was removed in vacuo and the residue was chromatographed on SiO 2 with CH 2 Cl 2 / petroleum ether mixture (2:1).…”

Section: Generalmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…However, the nucleophilic demethylation of SMe 2 group by halide ions is well known in organic chemistry [7]. For example, I À catalyzes exchange of methyl between two dialkyl sulfides [8].Herein, we report room-temperature reactions of (h-9-SMe 2 -7,8-Me 2 -7,8-C 2 B 9 H 8 )MBr 2 (1a,b; Scheme 1) 1 with CpTl, which are accompanied by demethylation of the SMe 2 group. Demethylation of this group in cationic metallacarboranes by free halide anions was studied both experimentally and theoretically.…”

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Demethylation of the SMe 2 substituent in cationic metallacarboranes. Halide anion influence

Vinogradov

Nelyubina

Loginov

et al. 2015

Journal of Organometallic Chemistry

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Methyl transfers. 14. Nucleophilic catalysis of nucleophilic substitution

Cited by 27 publications

References 1 publication

Regioselective synthesis of cationic 6-deoxy-6-(N,N,N-trialkylammonio)curdlan derivatives

Regioselective synthesis of cationic 6-deoxy-6-(N,N,N-trialkylammonio)curdlan derivatives

Promoting the Hydrosilylation of Benzaldehyde by Using a Dicationic Antimony‐Based Lewis Acid: Evidence for the Double Electrophilic Activation of the Carbonyl Substrate

Demethylation of the SMe 2 substituent in cationic metallacarboranes. Halide anion influence

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