Process for preparing alkyl-4-oxotetrahydrofuran-2-carboxylate

1 . A method for preparing a compound of general formula (I)

in which

R 1 is (C 1 -C 4 ) alkyl,

the method comprising:

reacting a compound of general formula (II)

in which

R 2 is (C 1 -C 4 ) alkyl,

with a compound of general formula (III)

in which R 1 is as defined above,

in the presence of MO—Z in an alcohol Z—OH,

in which

M is an alkali metal ion and

Z is (C 1 -C 4 ) alkyl, not including t-butyl;

forming, in a cyclization reaction, a cyclization product of general formula (IV)

in which R 1 is as defined for formula (I); and

reacting, under non-hydrolytic conditions, the cyclization products in a dealkoxycarbonylation reaction to form the compound of general formula (I).

2 . The method according to claim 1 , wherein:

R 1 is ethyl or methyl,

R 2 is ethyl or methyl,

M is sodium or potassium, and

Z is ethyl or methyl.

3 . The method according to claim 2 , wherein:

R 1 is methyl,

R 2 is methyl,

M is sodium, and

Z is methyl.

4 . The method according to claim 1 , wherein, in addition to the cyclization product having the general formula (IV), intermediates (V) and (VI) also form

in which R 1 is as defined for formula (I) and R 2 is as defined for formula (II), wherein the intermediates (V) and (VI) react further to form the compound of formula (IV).

5 . The method according to claim 1 , wherein the alcohol Z—OH is removed by distillation during the cyclization reaction.

6 . The method according to claim 1 , wherein the cyclization is carried out at a temperature of from 15 to 70° C.

7 . The method according to claim 6 , wherein the cyclization reaction is carried out at a temperature of from 40 to 60° C.

8 . The method according to claim 1 , wherein the cyclization reaction is conducted in the presence of at least one solvent selected from the group consisting of anisole, THF, toluene, xylene and Me-THF.

9 . The method according to claim 8 , wherein the solvent further comprises Z—OH, where Z is (C 1 -C 4 ) alkyl, not including t-butyl.

10 . The method according to claim 8 , wherein the solvent used for the cyclization reaction is an anhydrous solvent.

11 . The method according to claim 1 , characterized in that further comprising metering in the MO—Z in Z—OH.

12 . The method according to claim 1 , further comprising adding NaOMethyl to the cyclization reaction.

13 . The method according to claim 1 , further comprising adding a reagent/solvent to the dealkoxycarbonylation reaction, wherein the reagent/solvent is acetic acid or consists of a mixture of acetic acid and trifluoroacetic acid.

14 . The method according to claim 4 , wherein:

R 1 is ethyl or methyl,

R 2 is ethyl or methyl,

M is sodium or potassium, and

Z is ethyl or methyl.

15 . The method according to claim 14 , wherein:

R 1 is methyl,

R 2 is methyl,

M is sodium, and

Z is methyl.

16 . The method according to claim 5 , wherein:

R 1 is ethyl or methyl,

R 2 is ethyl or methyl,

M is sodium or potassium, and

Z is ethyl or methyl.

17 . The method according to claim 16 , wherein:

R 1 is methyl,

R 2 is methyl,

M is sodium, and

Z is methyl.

18 . The method according to claim 7 , wherein:

R 1 is ethyl or methyl,

R 2 is ethyl or methyl,

M is sodium or potassium, and

Z is ethyl or methyl.

19 . The method according to claim 18 , wherein:

R 1 is methyl,

R 2 is methyl,

M is sodium, and

Z is methyl.

20 . The method according to claim 9 , wherein:

R 1 is methyl,

R 2 is methyl,

M is sodium, and

Z is methyl.