- Reduction of thiokols in the system hydrazine hydrate-base as a new route to alkanedithiols
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A new procedure for preparative synthesis of alkanedithiols from simple commercially available products is based on reduction of the S-S bond in appropriate polyalkylene disulfides (thiokols) in the system hydrazine hydrate-base. Thiokols were prepared by reaction of dihaloalkanes with Na2S2 or K2S2 generated from elemental sulfur and alkali in aqueous hydrazine hydrate. Reaction of 1,2-dibromocyclohexane with sodium or potassium disulfide yields bis(2-bromocyclohexyl) sulfide as the only product.
- Alekminskaya,Russavskaya,Korchevin,Deryagina,Trofimov
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p. 732 - 737
(2007/10/03)
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- Chlorination of aromatic compounds and catalysts therefor
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A process for the chlorination of an aromatic compound of the following formula (A) : wherein RAis H or C1to C12alkyl, cycloalkyl, aryl, alkaryl, aralkyl or carboxyalkyl, the or each RBindependently is selected from H, C1-C4alkyl (especially methyl), C1-C4haloalkyl or polyhaloalkyl, e.g. C1-C4perfluoroalkyl, C1-C4alkoxy, C5-C12aryl (e.g. phenyl), alkaryl or aralkyl, or halogen, n is an integer which is 0, 1 or 2, and the or each RB, if present, may independently be attached at the ortho or the meta position (preferably at the meta-position), which process comprises reacting (preferably in homogeneous liquid phase below 35°C) the aromatic compound (which is preferably phenol) with a chlorinating agent (preferably sulphuryl chloride) in the presence of a sulphur-containing catalyst, optionally also in the presence of a Lewis acid co-catalyst, characterised in that the sulphur-containing catalyst is a compound according to the following formula (I) or formula (II) : in which: each of X1, X2, and X3is independently selected from the group consisting of: S, SO, SO2; R1is selected from the group consisting of: optionally substituted straight or branched chain alkyl or alkanediyl having from 2 to 20 carbon atoms, optionally substituted straight or branched chain alkaryl or aralkyl having from 5 to 20 carbon atoms, and optionally substituted aryl having from 5 to 20 carbon atoms; R2is an optionally substituted straight or branched chain alkyl or alkanediyl group having from 1 to 20 carbon atoms; R3and R4are each independently selected from the group consisting of: H, optionally substituted straight or branched chain alkyl or alkanediyl having from 1 to 20 carbon atoms, optionally substituted straight or branched chain alkaryl or aralkyl having from 5 to 20 carbon atoms, and optionally substituted aryl having from 5 to 20 carbon atoms; R5is an optionally substituted straight or branched chain alkylene, arylene, alkarylene or arylalkylene group having from 1 to 20 carbon atoms; wherein in the above definitions of R1, R2, R3, R4and R5the optional substituents may be independently selected from the following: halogen (e.g. F, Cl), hydroxy, amino, cyano, nitro, C1-C4alkyl, C1-C4haloalkyl e.g. C1-C4perfluoroalkyl, C1-C4alkoxy, C1-C4alkoxycarbonyl.
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- New synthesis of unsymmetrical dithia compounds
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1,2-Dithiacycloalkanes undergo nucleophilic ring-opening with organolithium reagents; the intermediates can be treated with electrophiles to provide unsymmetrical dithia compounds in high yields.
- Smith, Keith,Tzimas, Michael
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p. 2381 - 2382
(2007/10/02)
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- Dimethylcarbonat als Methylierungsmittel unter phasen-transfer-katalytischen Bedingungen
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Dimethyl carbonate (as well as diethyl, diallyl, dibenzyl carbonate and ethane-1,2-diyl carbonate) in the presence of potassium carbonate and 18-crown-6 (or Aliqual 336) is a versatile, cheap, and safer reagent for the methylation of a variety of organic substrates.
- Lissel, Manfred,Schmidt, Stefan,Neumann, Beate
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p. 382 - 383
(2007/10/02)
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