Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/30—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group
  • C07C67/317—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group by splitting-off hydrogen or functional groups; by hydrogenolysis of functional groups

Definitions

• the invention relates to a process for the preparation of compounds having a CHF2 C (O) or CHFC (O) group by hydrodehalogenation, preferably
• Hydrodechlorination from corresponding bromine, iodine or chlorine compounds preferably from compounds with a CCIF2 C (O) or CCIFC (O) group.
• the object of the present invention is to provide an improved process for the preparation of compounds having a CHF2C (O) or CHFC (O) group, in particular corresponding ester or diester compounds. This object is achieved by the method according to the invention.
• the process according to the invention provides for the preparation of compounds having a CF n HC (O) group from a CF n XC (O) group and zinc in the presence of an alcohol as a proton source, where n is 1 or 2 and X is bromine, iodine or preferably chlorine, where X is replaced by hydrogen, excluding compounds which are substituted by X both in the ⁇ -position and in the ⁇ -position.
• This also includes compounds with an (O) CCHFC (O) group which are produced from a compound with an (O) CCCIFC (O) group.
• X is exchanged for hydrogen; therefore, those compounds with two (or more) X substituents which result in the exchange of X for hydrogen as well as for an alkoxy radical (derived from alcohol present) are not encompassed by the invention.
• compounds with two or more CF n HC (O) groups can also be made from compounds with two or more CF n XC (O) groups.
• the alcohol serves as a proton source for the reaction; it can also be used in excess and then also serves as a solvent.
• the respective product compound can also be added as a solvent.
• Dimethylformamide or other carboxylic acid amides are preferably not contained in the reaction mixture.
• a preferred embodiment of the process according to the invention is characterized in that compounds with one or two CF n HC (0) groups are prepared from a compound with one or two CF n XC (O) groups, where n and X have the abovementioned meaning , Compounds having one or two CF n HC (O) groups are preferably prepared from a compound having one or two CF n CIC (0) groups.
• R 1 stands for F; for C1-C5 alkyl; or for C1-C5-alkyl which is substituted by at least 1 fluorine atom; and R 2 represents C1-C5 alkyl; or for C1-C5-alkyl which is substituted by at least 1 fluorine atom. It is also preferred to make a diester of
• R 3 OC (O) CFHC (O) OR 3 , wherein R 3 is C1-C5-alkyl; or for C1-C5-alkyl which is substituted by at least 1 fluorine atom.
• Preferred starting compounds are the respective chlorine-substituted compounds.
• R 1 very particularly preferably represents F or C1-C3, which is partially fluorinated or perfluorinated.
• R 2 and R 3 are preferably methyl, ethyl, n-propyl or i-propyl.
• R 1 preferably represents F or CF 3 .
• the alcohol used as the proton source suitably corresponds to the radical R 2 or R 3 .
• the ester is prepared in situ from the corresponding acid chloride and alcohol.
• the alcohol is not only a source of protons, but also serves to esterify the acid chloride. Accordingly, more alcohol has to be used. However, since the alcohol is expediently used in excess as a solvent, this is not a problem.
• the non-protic solvent used is preferably at least predominantly the product to be produced, e.g. the ester or diester with one or more CHF2C (O) or CHFC (O) groups.
• Nitriles are preferably not included as a solvent.
• carboxylic acid amides such as DMF are also preferably not used as solvents.
• 0.9 to 2.1 equivalents of zinc are preferably used per chlorine atom to be exchanged. It is preferred to use about 1.1 to 2 zinc atoms per chlorine atom; a stoichiometric excess of zinc has proven to be advantageous.
• the temperature at which the reaction between bromine-, iodine- or chlorine-containing starting compound, zinc and alcohol is carried out is advantageously between 50 ° C. and the boiling point of the corresponding alcohol.
• the isolation can be done according to conventional methods.
• Another object of the invention is the azeotrope of methyl difluoroacetate and methanol, which in the reaction of methyl chlorodifluoroacetate, Zinc and methanol can be distilled.
• This azeotrope can be used, for example, as a solvent or cleaning agent.
• the advantage is that it can be purified by redistillation without changing its composition.
• it can also be added to the reaction mixture of zinc and methyl chlorodifluoroacetate and, if appropriate, methanol.
• the amount of methanol serving as the proton source can be reduced; if necessary, the methanol required as a proton source can be omitted entirely.
• the azeotrope then serves as a solvent and - because of the methanol contained - as a proton source.
• the process according to the invention has the advantage that high yields and high selectivities are achieved. Solvents like DMF are also more difficult to dispose of.
• Example 1 Preparation of difluoroacetic acid methyl ester from chlorodifluoroacetic acid methyl ester and zinc
• CDFAMe methyl chlorodifluoroacetate
• CDFAEt chlorodifluoroethyl ester
• CDFACI chlorodifluoroacetyl chloride

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

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Publications (1)

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• 2004
  • 2004-03-08 EP EP04005507A patent/EP1574496A1/de not_active Withdrawn
• 2005
  • 2005-02-04 EP EP05707195A patent/EP1725513A1/de not_active Withdrawn
  • 2005-02-04 US US10/591,877 patent/US20070191632A1/en not_active Abandoned
  • 2005-02-04 JP JP2007502209A patent/JP2007527874A/ja not_active Abandoned
  • 2005-02-04 CN CNA200580007262XA patent/CN1930113A/zh active Pending
  • 2005-02-04 WO PCT/EP2005/001123 patent/WO2005085173A1/de not_active Ceased
  • 2005-02-25 TW TW094105758A patent/TW200538431A/zh unknown

Non-Patent Citations (6)

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