Process for the production of tetronic acid alkyl esters
AssigneeLonza Ltd.
InventorJoachim Lenzner
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Abstract
A new process for the production of tetronic acid alkyl esters of the general formula: ##STR1## starting from 4-haloacetoacetic acid alkyl esters of the general formula: ##STR2## The 4-haloacetoacetic acid alkyl esters of general formula II are converted in a first step with a dialkylsulfite of the general formula: (RO).sub.2 S.dbd.O III in the presence of a strong acid into a 4-halo-3-alkoxy-but-2E-enoic acid alkyl ester of the general formula: ##STR3## The latter is cyclized in a second step with a formate and a strong acid to the end product according to formula I.
Claims17
A process for the production of a tetronic acid alkyl esters of formula:
- ##STR10## wherein R is a C.sub.1 -C.sub.6 -alkyl group, comprising, in a first step, converting a 4-halo-acetoacetic acid alkyl ester of formula:
- ##STR11## wherein X is chlorine or bromine and R.sub.1 is a C.sub.1 -C.sub.6 -alkyl group, with a dialkylsulfite of formula:
- (RO).sub.2 S.dbd.O III
- wherein R has the above-mentioned meaning, into the corresponding intermediately formed ketal ester, converting the corresponding intermediately-formed ketal ester in the presence of a strong acid into a 4-halo-3-alkoxy-but-2E-enoic acid alkyl ester of formula:
- ##STR12## wherein X, R and R.sub.1 have the above-mentioned meanings, and then cyclizing in a second step, the 4-halo-3-alkoxy-but-2E-enoic acid alkyl ester with a formate and a strong acid to the tetronic acid alkyl ester of formula I.
Dependencies are inferred from the claim text.