Process for the catalytic dealkoxylation of 1,1,3-trialkoxy-2-me

Details Process for the catalytic dealkoxylation of 1,1,3-trialkoxy-2-me Process for the catalytic dealkoxylation of 1,1,3-trialkoxy-2-me

1998-05-12

1999-11-23

Kumar, Shailendra

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

568594, 568600, 568672, 568687, 568591, 562238, C07C 4128

Patent

active

059903600

ABSTRACT:
A novel process for the manufacture of a .gamma.-halotiglic aldehyde HalH.sub.2 C-CH.dbd.C(CH.sub.3)-CHO [I], wherein Hal signifies chlorine or bromine, comprises haloalkoxylating a 1-alkoxy-2-methyl-1,3-butadiene H.sub.2 C.dbd.CH-C (CH.sub.3).dbd.CH-OR.sup.1 [II], wherein R.sup.1 signifies C.sub.1-4 -alkyl, using a particular halogenating agent in a C.sub.1-4 -alkanol (R.sup.2 OH) and hydrolyzing the thus-obtained .gamma.-halotiglic aldehyde dialkyl acetal HalH.sub.2 C-CH.dbd.C(CH.sub.3)-CH (OR.sup.1)(OR.sup.2) [III] to the desired .gamma.-chloro- or .gamma.-bromotiglic aldehyde I. The halogenating agent used in this process is selected from an alkali metal hypochlorite, an alkali metal hypobromite, an alkaline earth metal hypochlorite, an alkaline earth metal hypobromite, tert.butyl hypochlorite, N-bromoacetamide, 1.3-dichloro-5,5-dimethylhydantoin and 1,3-dibromo-5,5-dimethylhydantoin. Further aspects of the present invention are the use of the thus manufactured .gamma.-halotiglic aldehyde for the production of .gamma.-acetoxy-tiglic aldehyde or of a Wittig aldehyde halide Hal-Ph.sub.3 P.sup.+ CH.sub.2 -CH.dbd.C(CH.sub.3)-CHO [VII], wherein Hal signifies chlorine or bromine and Ph a process for the catalytic dealkoxylation of the 1,1,3-trialkoxy-2-methyl-butane CH.sub.3 -CH(ORl)-CH(CH.sub.3)-CH(OR.sup.1).sub.2 [VI] to the corresponding 1-alkoxy-2-methyl-1,3-butadiene II in the gas phase using an aluminium silicate of medium specific surface as the catalyst. The products I, .gamma.-acetoxy-tiglic aldehyde and VII are known, important intermediates for the production of various apocarotenoids and diapocarotenoids as well as of Vitamin A.

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