- Preparation, Structure and Vibrational Spectrum of the Dimethylmethyleniminium Ion, including the Role of Cationic Polymers in its Formation
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Crystalline X (1X, where X = Br or I) results from the reaction of N,N,N',N'-tetramethylmethylenediamine with CH2Br2 or CH2I2 at room temperature.The structure of 1Br has been determined by X-ray crystallography.The crystals are orthorhombic, a = 6.262(2) Angstroem, b = 7.428(3) Angstroem, c = 5.651(2) Angstroem, z = 2, space group Pmmn.The final R = 0.037 for 484 observed reflections.The dimethylmethyleniminium cation, 1, has crystallographically imposed mm2 symmetry, with the C=N bond distance 1.263(5) Angstroem, C-N bond distance 1.474(4) Angstroem and CH3-N-CH3 angle 114.4(4) deg.The Raman spectrum of 1, investigated as the bromide and iodide salts, and supplemented by IR data for (1)2SnBr6, has been fully assigned with the aid of ab initio calculations using the 3-21G** basis at the SCF and MP2 levels.Isotopic labelling experiments which generate (+) from CD2I2 have been used in conjuction with NMR and Raman measurements to investigate the reactions leading to the iminium salt.The intermediate (+) and a cationic polymer (n+) are implicated in the reactions which form the basis of the synthesis of I.
- Clark, George R.,Shaw, Graeme L.,Surman, Peter W. J.,Taylor, Michael J.,Steele, Derek
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- Kinetic evidence for a novel, Grob-like substitution/fragmentation mechanism for the reaction of nucleophiles with trialkylammoniomethyl halides
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Kinetic evidence is presented in favor of a concerted, bimolecular mechanism for the unusual nucleophilic substitution/fragmentation reactions of iodide ion with (halomethyl)trimethylammonium salts. The relative reactivities of allyl, ethyl and methyl groups for this Grob-like reaction are also determined. Activation parameters are presented for the thermal reactions of 1-iodo-N,N,N-trimethylmethaniminium iodide (log A = 8.7. Ea = 19.0 kcal mol-1) and 1-iodo-N-allyl-N,N-dimethylmethaniminium iodide (log A = 14.6, Ea = 25.7 kcal mol-1) in acetonitrile, the latter reaction having an observed second order rate constant 39 times larger than the former at 70 °C. The results are compared with the classic data of Hughes, Ingold and Conant for SN2 reactions of alkyl halides.
- Fletcher, Michelle O.,Zhang, Li,Vu, Quyen,Dolbier Jr., William R.
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- A Simple and Highly Diastereoselective One-Pot Synthesis of Mannich-Bases
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A convenient one-pot procedure for the synthesis of β-amino ketones 5 from economical shelf reagents is described. Iminium salts 3 are generated in virtually quantitative yields from secondary amines 1 and aldehydes 2 mediated by NaI/Me3SiCl/NEt3. Subsequently, the salts 3 are used for the in situ aminoalkylation of enamines 4. The method provides the Mannich bases 5 in high yields and excellent diastereoselectivities (>96 % ds). It can also be applied for the aminoalkylation of other nucleophiles such as imines or electron-rich aromatic compounds.
- Arend, Michael,Risch, Nikolaus
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p. 974 - 976
(2007/10/03)
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- The synthesis of primary, secondary and tertiary aminomethyltetrathiafulvalenes
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The title compounds have been prepared in one or two steps, either formyltetrathiafulvalene or tetrathiafulvalenyllithium as starting materials.
- Fabre, Jean-Marc,Garin, Javier,Uriel, Santiago
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p. 3983 - 3990
(2007/10/02)
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- Carbon-Carbon Bond Formation by the Use of Chloroiodomethane as a C1 Unit. III. A Convenient Synthesis of the Mannich Base from Enol Silyl Ether by a Combination of Chloroiodomethane and N,N,N',N'-Tetramethylmethanediamine
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The Mannich dimethylaminomethylation of carbonyl compounds is conveniently carried out via enol trimethylsilyl ethers by a combination of chloroiodomethane (CH2ClI) and N,N,N',N'-tetramethylmethanediamine (TMMD) in DMSO as the solvent at ambient temperatute.The mechanism of the transformation is discussed on the basis of product analysis and 1H NMR spectral studies.The reagent system CH2ClI/TMMD also provides a convenient route to the Eschenmoser's salt ().
- Miyano, Sotaro,Hokari, Hiroshi,Hashimoto, Harukichi
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p. 534 - 539
(2007/10/02)
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- SUBSTITUTION OF THE ANION IN AMMONIUM AND PHOSPHONIUM CHLORIDES BY THE ACTION OF ELECTROPHILIC AGENTS
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N,N-Dialkylmethaniminium iodides were obtained by the reactions of N,N-dialkylmethaniminium chlorides with methyl iodide.The reactions of ammonium and phosphonium chlorides with triethyloxonium tetrafluoroborate, dimethyl sulfate, methyl tosylate, and methyl iodide take place with substitution of the chloride ion by the BF4-, CH3SO3O-, p-CH3C6H4SO3- or I- ions.Substitution of the chloride ion of phosphonium salts by the iodide ion can be realized by the action of trimethyliodosilane.
- Kukhar', V. P.,Pasternak, V. I.,Shevchenko, I. V.,Shevchenko, M. V.,Marchenko, A. P.,Makovetskii, Yu. P.
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p. 161 - 166
(2007/10/02)
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