MULTISTAGE PROCESS FOR PREPARING ALKALI METAL SALTS OF SPECIFIC 4-HYDROXY-2-OXO-2,5-DIHYDROFURAN-3-CARBOXYLIC ESTERS

摘要

The present invention relates to a multi-stage method for preparing alkali metal salts of specific 4-hydroxy-2-oxo-2,5-dihydrofuran-3-carboxylic esters of the formula (I),;;in which M and R1 are as defined in the description,

which proceeds from malonic ester and does not require isolation of intermediates.

主权项

1. Method for preparing an alkali metal salt of a 4-hydroxy-2-oxo-2,5-dihydrofuran-3-carboxylic ester of formula (I) comprising: (i): reacting a malonic ester of formula (II) with an alcoholic alkali metal hydroxide solution to give the corresponding malonic ester mono-alkali metal salt of formula (III) (ii): reacting a malonic ester monoalkali metal salt of formula (III) from (i) with a chloroacetic ester of formula (IV) in the presence of at least one phase transfer catalyst to give a compound of formula (V) wherein the phase transfer catalyst is an organic ammonium or phosphonium salt, (iii): reacting a compound of formula (V) by addition of an alkali metal alkoxide of formula (VI)
M′OR3  (VI) in a ring closure reaction as a result of which the alkali metal salt of 4-hydroxy-2-oxo-2,5-dihydrofuran-3-carboxylic ester of formula (I) is produced, where in said formulae (I) to (VI) R1, R2 and R3 are each independently C1-C12-alkyl; M and M′ are each independently an alkali metal in a corresponding oxidation state.