Flüssiges Schwefeldioxid als Lewis‐acides Solvens für die Alkylierung und Alkoxyalkylierung von Allylsilanen

Mayr, Herbert; Gorath, Gorden; Bauer, Bernhard

doi:10.1002/ange.19941060716

Cited by 4 publications

(1 citation statement)

References 19 publications

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“…Since sulfur dioxide is known to be an electron pair acceptor that can be employed as a Lewis acidic solvent, a strong solvation of Cl - by SO 2 was expected. It was not surprising therefore that solutions of 2a -Cl (δ + N  C H Ph 8.92, Table ) and 2a -AlCl 4 (δ + N  C H Ph 8.84) in liquid sulfur dioxide exhibit almost identical 1 H NMR spectra: The chemical shifts correspond to those of free ions.…”

Section: Resultsmentioning

confidence: 99%

NMR Spectroscopic Evidence for the Structure of Iminium Ion Pairs

et al. 1997

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The NMR spectroscopic investigation of solutions of the iminium ions Me2N+C(H)Cl (1 + ), Me2N+ C(H)Ph (2a + ), and Et2N+CH2 (3 + ) in aprotic solvents shows that the replacement of the weakly nucleophilic counterions SbCl6 -, AlCl4 -, BF4 -, or CF3SO3 - by halide ions (I-, Br-, Cl-) causes a deshielding of the proton at the iminium carbon atom (Δδmax = +2.8 for 2a + in CD2Cl2) while the chemical shifts of all other 1H and 13C nuclei remain almost unaffected. The solvent dependence of these effects, 14N NMR investigations, and ab initio MO calculations suggest that iminium halides form CH···Y- hydrogen bonds (Y = Cl, Br, and I) and thus exist as contact ion pairs in acetonitrile, chloroform, dichloromethane, and dimethyl sulfoxide solutions. In liquid sulfur dioxide, specific anion−cation interactions cannot be observed due to the superior solvation of the anions by SO2.

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Section: Resultsmentioning

confidence: 99%

NMR Spectroscopic Evidence for the Structure of Iminium Ion Pairs

et al. 1997

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Sulfonic Acid‐Functionalized Ionic Liquids as Metal‐Free, Efficient and Reusable Catalysts for Direct Amination of Alcohols

Han

Yang

et al. 2012

Adv Synth Catal

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A series of sulfonic acid‐functionalized (SO3H‐functionalized) ionic liquids was synthesized and used as metal‐free, highly selective and efficient catalysts for the direct amination of alcohols. Notably, the activities of the series of SO3H‐functionalized ionic liquids were compared and a 92% isolated yield was obtained using 3‐tetradecyl‐1‐(butyl‐4‐ sulfonyl)imidazolium trifluoromethanesulfonate ([BsTdIM][OTf]) as the catalyst. Importantly, the catalytic system has wide substrate scope including benzylic, allyl, propargylic, aliphatic alcohols with sulfonamide, amide, carbamate, aromatic amine and N‐heterocyclic compounds. Interestingly, the system was also suitable for a multi‐gram scale direct amination of alcohols. Additionally, the reusable nature of [BsTdIM][OTf] makes this protocol more attractive and avoids the disposal and neutralization of acidic catalysts. Moreover, preliminary experiments indicated that this reaction should proceed via an SN1 pathway.

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ChemInform Abstract: Liquid Sulfur Dioxide as a Lewis‐Acidic Solvent for the Alkylation and Alkoxyalkylation of Allylsilanes.

1994

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Liquid Sulfur Dioxide as a Lewis-Acidic Solvent for the Alkylation and Alkoxyalkylation of Allylsilanes. -The investigations of alkylation reactions with alkyl chlorides suggest that only compounds with high SN1 reactivities such as (VIII) are reactive under these conditions. The use of liq. SO2 as solvent can replace metal halides as Lewis acids.-(MAYR, H.; GORATH, G.; BAUER, B.; Angew. Chem. 106 (1994) 7, 793-794; Inst. Org.

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Flüssiges Schwefeldioxid als Lewis‐acides Solvens für die Alkylierung und Alkoxyalkylierung von Allylsilanen

Cited by 4 publications

References 19 publications

NMR Spectroscopic Evidence for the Structure of Iminium Ion Pairs

NMR Spectroscopic Evidence for the Structure of Iminium Ion Pairs

Sulfonic Acid‐Functionalized Ionic Liquids as Metal‐Free, Efficient and Reusable Catalysts for Direct Amination of Alcohols

ChemInform Abstract: Liquid Sulfur Dioxide as a Lewis‐Acidic Solvent for the Alkylation and Alkoxyalkylation of Allylsilanes.

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