- REACTIONS OF HALOGEN FLUORIDES. XIII. NEW POSSIBILITIES FOR OXIDATIVE NUCLEOPHILIC FLUORINATION OF BROMINE-SUBSTITUTED ESTERS BY THE HEXACHLOROMELAMINE-HYDROGEN FLUORIDE SYSTEM
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Primary, secondary, and tertiary bromine atoms in bromine-substituted esters, including the bromine atoms of the CBr2 group at the α position to the ester group, are substituted effectively by a bromine atom in the hexachloromelamine-liquid hydrogen fluoride system under normal conditions.New methods were developed for the production of alkyl and fluoroalkyl 2,3-dihalogeno-2-fluoropropionates, which are key compounds in the synthesis of α-fluoroacrylates.
- Chuvatkin, N. N.,Panteleeva, I. Yu.,Kurskii, Yu. A.,Boguslavskaya, L. S.
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p. 1450 - 1456
(2007/10/02)
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- SYNTHESIS AND ENZYMATIC CLEAVAGE OF D,L-3-FLUOROALANINE
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The action of bromine trifluoride on methyl 2,3-dibromopropionate in the presence of stannic chloride gives a high yield of methyl 2-bromo-3-fluoropropionate.Under the conditions of phase-transfer catalysis the product gave a 3-fluoro-2-azido ester, and reduction of the latter with hydrogen in the presence of Pd/C gave 3-fluoroalanine methyl ester.Enzymatic cleavage of N-BOC-3-fluoro-D,L-alanine methyl ester with papain took place stereospecifically, and N-BOC-3-fluoro-L-alanine was isolated with an almost quantitative yield.
- Gerus, I. I.,Yagupol'skii, Yu. L.,Kukhar, V. P.,Boguslavskaya, L. S.,Chuvatkin, N. N.,et al.
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p. 465 - 468
(2007/10/02)
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- REACTIONS OF HALOGEN FLUORIDES XII. REACTION OF BROMINE TRIFLUORIDE WITH BROMINE-CONTAINING ESTERS. A NEW METHOD FOR THE SYNTHESIS OF FLUOROALKYL 2-FLUOROACRYLATES
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Being weak Lewis bases, esters reduce the reactivity of bromine trifluoride in the substitutive fluorination of organic bromine derivatives.For this reason the rate of the reaction of bromine trifluoride with bromine-containing esters depends not only on the electronic characteristics of the substituents at the reaction center but also on the basicity of the ester.As a rule, the selectivity of the reaction increases with increase in the basicity of the ester.The reaction of bromine trifluoride or chlorine monofluoride with fluoroalkyl 2,3-dibromopropionates can be used successfully for the synthesis of monomers (fluoroalkyl 2-fluoroacrylates).
- Kartashov, A. V.,Chuvatkin, N. N.,Boguslavskaya, L. S.
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p. 2243 - 2248
(2007/10/02)
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- REACTIONS OF HALOGEN FLUORIDES. VII. FLUORINATION OF UNSATURATED COMPOUNDS WITH BROMINE TRIFLUORIDE AND AN EQUIMOLAR MIXTURE OF BROMINE TRIFLUORIDE WITH MOLECULAR BROMINE
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The reactions of bromine trifluoride and an equimolar mixture of bromine trifluoride and bromine with halogen-substituted alkenes and methyl α-substituted acrylates were investigated.With sufficient dilution of the substrate by Freon 113 (20-25:1) it is possible to obtain the bromofluoro and difluoro adducts with good yiels.The best results (overall yields of fluorination products 80-83percent) were obtained with alkenes containing a halogen at the multiple bond; in the case of more reactive substrates the reaction becomes nonpreparative.The bromofluorination of E- and Z-1,2-dichloroethylenes and E- and Z-1,3-dichloropropenes with pure bromine trifluoride is antistereospecific.The bromofluorination of E- and Z-1,2-dichloroethylenes by the BrF3-Br2 system gives a mixture of diastereomeric bromofluoro adducts as a result of isomerization of the initial olefins in the presence of the bromine.The formation of the difluorides of the halogenated olefins is nonstereospecific and is accompanied by migration of the halogens.
- Boguslavskaya, L. S.,Chuvatkin, N. N.,Kartashov, A. V.,Ternovskoi, L. A.
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p. 230 - 236
(2007/10/02)
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- Boron Trifluoride Promoted Reaction of Alkyl Hypohalites with Alkenes. A New Synthesis of Fluoro Halides
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The reactions of the following alkenes with alkyl hypohalites and boron trifluoride (BF3) were investigated: cyclohexene (3), 1-hexene (8), trans-1,2-dichloroethylene (15), methyl acrylate (18), methyl crotonate (25), methyl isocrotonate (29), butadiene (33), methyl vinyl ketone (42), and styrene (45).Reactions of these alkenes with methyl hypochlorite (1) and BF3 in dichloromethane give fluoro chloride adducts as well as methoxy chlorides with the percentage of fluoro chlorides varying from 75percent for 29 to 8percent for 45.Fluoro bromide adducts are obtained with methyl hypobromite (2).Reactions with the tert-butyl hypohalites and BF3 also give fluoride incorporation.The percentage of fluoride incorporation with 1 or 2 is significantly greater in carbon tetrachloride than in dichloromethane.
- Heasley, Victor L.,Gipe, Robert K.,Martin, Jody L.,Wiese, Harry C.,Oakes, Melanie L.,Shellhamer, Dale F.
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p. 3195 - 3199
(2007/10/02)
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- REACTIONS OF CHLORINE MONOFLUORIDE. REGIOSPECIFICITY AND STEREOCHEMISTRY OF THE SUBSTITUTION OF BROMINE ATOMS BY FLUORINE IN HALOGEN-SUBSTITUTED ALKANES AND ESTERS
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Under mild conditions without catalysts chlorine monofluoride substitutes bromine atoms for fluorine in bromine-substituted alkanes and esters.Electron-donating substituents promote the substitution reaction.The following sequence is observed in the reactivity of the bromine atoms at the carbon: tertiary > secondary > primary.Halogen atoms (Cl, F) at a carbon containing a bromine also promotes substitution of the latter by fluorine.The reactivity of the bromine atoms decreases in the following order: CCl2Br(CClFBr) > CHClBr(CHFBr) > CH2Br.An alkoxycarbonyl group at a carbon containing bromine prevents substitution.In a number of cases substitutive fluorination is accompanied by skeletal rearrangements and by migration of chlorine atoms.The stereochemistry of substitutive fluorination was studied for the case of the reaction of erythro- and threo-1-bromo-2-fluoro-1,2-dichloroethanes and 1,2-dibromo-1,3-dichloropropanes with chlorine monofluoride.The probable mechanism of the reaction is discussed.
- Boguslavskaya, L. S.,Chuvatkin, N. N.,Panteleeva, I. Yu.,Ternovskoi, L. A.
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p. 814 - 820
(2007/10/02)
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