24.
    发明专利
    未知

    公开(公告)号:DE3719622A1

    公开(公告)日:1988-12-29

    申请号:DE3719622

    申请日:1987-06-12

    Applicant: BASF AG

    Abstract: Alkyl gamma -halotiglates of the general formula I (I) where X is Cl or Br and R2 is alkyl of 1 to 3 carbon atoms, having a high E isomer content, are prepared by a process in which (a) the corresponding 2-methyl-but-3-enoate of the general formula II (II) is reacted with chlorine or bromine in the absence of a solvent and (b) the resulting 2-methyl-3,4-dihalobutyrate of the general formula III (III) is dehydrohalogenated by reaction with a solution of an alkali metal hydroxide in an alcohol R2OH, where R2 has the stated meaning, or in a mixture of water and an alcohol R2OH, and the products are further processed to give O,O-dialkyl- gamma -phosphonotiglates of the general formula IV (IV) where R1 is alkyl of 1 to 4 carbon atoms and R2 is alkyl of 1 to 3 carbon atoms, preferably ethyl, by reaction with a trialkyl phosphite and thermal isomerization. The process gives C5 building blocks which are extremely interesting for polyene chemistry, the said building blocks being obtained in good yields and essentially in the form of the required E isomers.

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