- Vapor generation of inorganic anionic species after aqueous phase alkylation with trialkyloxonium tetrafluoroborates
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Aqueous phase reaction of trialkyloxonium tetrafluoroborates, R 3O+BF4- (R=Me, Et) has been tested in the alkylation of simple inorganic anionic substrates such as halogen ions, cyanide, thiocyanate, sulphide an
- D'Ulivo, Alessandro,Pagliano, Enea,Onor, Massimo,Pitzalis, Emanuela,Zamboni, Roberto
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experimental part
p. 6399 - 6406
(2010/04/06)
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- Transformation of tertiary amines into alkylating reagents by treatment with 2-chloro-4,6-dimethoxy-1,3,5-triazine. A synthetic application of side-reaction accompanying coupling by means of 4-(4,6-dimethoxy-[1,3,5] triazin-2-yl)-4-methyl-morpholin-4-ium chloride (DMTMM)
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Mild reaction conditions are described for the preparation of a number of alkyl chlorides and 2-dialkyl(aryl)amino-4,6-dirnethoxy-1,3,5-triazines by dealkylation of quaternary triazinylammonium chlorides formed as reactive intermediates in reaction of tertiary amines with 2-chloro-4,6-dimethoxy-1,3,5- triazine. The high selectivity of substitution was observed within the reactivity order of the alkyl groups: benzyl ～ allyl > methyl > n-alkyl. Studies on dealkylation of S-(-)-J-dimethyl-(1-phenylethyl)amine to R-(+)-1-chloro-1-phenylethane revealed that reaction proceeded with an inversion of configuration on the carbon atom as may be expected for SN2 type substitution. The scope of reaction was extended by exchange of anion in quaternary triazinylammonium chlorides with 1-, SCN-, C6H5O-, CH3COO- followed by N-dealkylation step.
- Kolesinska,Kaminski
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experimental part
p. 2115 - 2123
(2009/04/07)
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- Polymer-supported thiocyanate as new, versatile and efficient polymeric reagent for conversion of alkyl halides to corresponding alkyl thiocyanates under mild conditions
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Crosslinked poly(N-methyl-4-vinylpyridinium)thiocyanate [P 4-Me]SCN (II) is prepared easily and is used as a new polymeric reagent for synthesis of alkyl thiocyanates from alkyl halides under mild and nonaqueous conditions. The used polymeric reagent usually can be removing quantitatively and be regenerated.
- Zarchi, Mohammad Ali Karimi
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p. 1299 - 1302
(2008/02/13)
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- NOVEL REACTIONS OF PENTACOORDINATE PHOSPHORUS SYSTEMS DERIVED FROM PYROCATECHOL
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Monocyclic chlorophosphoranes 1 and 2 have been used as models for investigations of nucleophilic displacement reactions at the pentacoordinate phosphorus atom.The chlorine ligands of 1 and 2 can be exchanged by nucleophiles under very mild conditions.Synthesis of the pentacoordinate phosphorus systems 4 and 5 via the reactions of 1 and 2 with a variety of nucleophiles is demonstrated.Special attention is paid to the reactions of chlorophosphoranes with such nucleophiles as organic phosphorus acids and thiocyanates.
- Skowronska, A.,Burski, J.,Krawczyk, E.,Pakulski, M.
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p. 119 - 126
(2007/10/02)
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- Nucleophilic Substitution Factors. 1. Coplanar vs. Orthogonal Bimolecular Substitution at a Benzylic Carbon. X-ray Structure of 2-Isobutyl-1,3-dihydrobenzothiophenium Perchlorate
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A stereoelectronic effect in bimolecular nucleophilic substitution at a benzylic center has been observed in the rates of reaction of thiourea in dimethyl-d6 sulfoxide with a series of sulfonium perchlorates with differing degrees of constraint in the orientation of the reacting C-S+ bond with respect to the plane of the aromatic ring.The substrates and their relative rates (at 37 deg C, unless otherwise noted) are as follows: (a, highly constrained) 2-ethyl-1,3-dihydrobenzothiophenium perchlorate (4b), 1,00, and 2-isobutyl-1,3-dihydrobenzothiophenium perchlorate (4c), 2.8; (b, partly constrained) 2-ethyl-3,4-dihydro-1H-2-benzothiopyranium perchlorate (7), 45 (at 82 deg C); (c, unconstrained) S,S-dibenzyl-S-ethylsulfonium perchlorate (5b), 8.1*103.An (8*103-fold rate difference was also observed between S,S-dibenzyl-S-ethylsulfonium terafluoroborate (5a) and 2-ethyl-1,3-dihydrobenzothiophenium tetrafluoroborate (4a) with potassium thiocyanate-18-crown-6 in acetonitrile-d3.Analysis of these rate differences, taken with inspection of molecular models which show that the observed rate differences are not adequately accounted for by simple nonbonding or angle strain effects, clearly indicates a dihedral angle dependent factor consistent with ?-overlap between p-orbitals on the aromatic ring and the carbon atom undergoing substitution.The "orbital-overlap factor" is estimated to increase the reactivity of the benzylic center in 5b (4*103-fold relative to that of the corresponding ethyl group (in 21).A single-crystal X-ray analysis on 4c showed the salt crystallizes in space group P21/n, unit cell dimensions a = 17.382 (1) Angstroem, b = 9.1731(6) Angstroem, c = 8.7828 (3) Angstroem, and β = 91.7 (2) deg, with Z = 4.On the basis of 2054 unique data with F2 > 2?, full matrix refinement converged at R = 0.044 for 232 variables.There is a dihedral angle of 3.8 deg between the C2,S,C9 plane and the plane of the aromatic ring consistent with the observed low reactivity of the benzylic center and the present analysis.The entropies of activation for benzylic substitution of the cyclic and acyclic substrates (4b, 4c, and 5b) with thiourea in Me2SO-d6 are very similar (-12 +/- 1 cal mol-1 K-1), in contrast to the great ΔS(excit.) difference reported for an analogous α-carbonyl system by Bartlett and Trachtenberg; the origin of this difference is discussed.
- King, J. F.,Tsang, T. Y.,Abdel-Malik, M. M.,Payne, N. C.
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p. 3224 - 3232
(2007/10/02)
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- SYNTHESIS OF ISOTHIOCYANATOPHOSPHORANES AND ISOTHIOCYANATOPHOSPHONIUM SALTS VIA OXIDATIVE ADDITION OF THIOCYANOGEN AND LIGAND SUBSTITUTION. NOVEL REAGENTS FOR CONVERTING HYDROXY GROUPS INTO THIOCYANATE AND ISOTHIOCYANATE FUNCTIONS UNDER MILD CONDITIONS
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The oxidative addition of thiocyanogen to triphenilphosphine has been investigated by (31)P NMR spectroscopy showing the formation of the isothiocyanatophosphonium salt 8.The analogous reaction between thiocyanogen and alkyl o-phenylene phosphites 7 leads to diisothiocyanatophosphoranes 9.The same products were prepared via ligand substitution from the corresponding chlorophosphonium salt 12 and alkyldichloro-o-phenylene phosphoranes 13 by the action of potassium thiocyanate in the presence of 18-crown-6-ether or more conveniently using lead thiocyanate.The phosphonium salt 8 and phosphoranes 9 were employed as convenient novel reagents for converting hydroxy groups into thiocyanate and isothiocyanate function with high stereoselectivity under very mild conditions.The efficient synthesis of acylisothiocyanates RCONCS,R2P(O)NCS and R2P(S)NCS via addition of thiocyanogen to mixed anhydrides is of special interest.
- Burski, J.,Kieszkowski, J.,Michalski, J.,Pakulski, M.,Skowronska, A.
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p. 4175 - 4182
(2007/10/02)
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- Dithioallophanic Acids : Interaction of Carbon Oxysulphide with S-Benzyl-N-phenyl/methylisothiocarbamide in Presence of Alkyl Halides
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Interaction of carbon oxysulphide with S-benzyl-N-phenyl/methylisothiocarbamide in acetone/benzene in the presence of benzyl chloride affords benzyl thiocyanate, dibenzyl dithiocarbonate, S-benzyl-N-phenyl/methylthiocarbamate and S-benzyl-1-phenyl/methylamidino-3-phenyl/methylisothiocarbamide hydrochloride.The intermediate alkyl ester of the corresponding N-γ-substituted-β-S-benzyldithioallophanic acid could not be isolated.The mechanism for the formation of these products from the intermediate dithioallophanic acid has been rationalised.
- Dravid, R. N.,Chande, M. S.
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p. 498 - 500
(2007/10/02)
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