Method for producing 4-aminobut-2-enolides

1. A process for preparing an 4-aminobut-2-enolide of formula (I)

in which

A is pyrid-2-yl or pyrid-4-yl or is pyrid-3-yl which is optionally 6-substituted by fluorine, chlorine, bromine, methyl, trifluoromethyl or trifluoromethoxy, or is a

 radical

in which

X is halogen, alkyl or haloalkyl, and

Y is halogen, alkyl, haloalkyl, haloalkoxy, azido or cyano, and

R 1 is alkyl, haloalkyl, alkenyl, haloalkenyl, alkynyl, cycloalkyl, cycloalkylalkyl, halocycloalkyl, alkoxy, alkoxyalkyl, halocycloalkylalkyl or arylalkyl,

comprising reacting a 4-haloacetoacetic ester of formula (II)

in which

R 2 is C 1 -C 12 -alkyl, C 5 -C 8 -aryl or arylalkyl, and

Hal is Cl, Br or I,

in the presence of a solvent at a temperature of from −20° C. to 60° C.,

a) with an amine of formula (IIIa)

in which R 1 is as defined above,

to give a compound of formula (IVa)

followed by

removing the solvent by distillation or under reduced pressure in a temperature range of from 20° C. to 35° C.,

thermally cyclizing the compound of formula (IVa) in the presence of a solvent at a temperature of from 40° C. to 150° C. to give a compound of formula (Va)

isolating the compound of formula (Va) by crystallization or removal of solvent, and reacting the compound of formula (Va) with a compound of the formula (VIa)

A-CH 2 -E  (VIa)

where A is as defined above and E is a leaving group selected from the group consisting of chlorine, bromine, iodine, mesylate, tosylate, or SO 2 CH 3 ,

to give compound (I);

or

b) with an amine of formula (IIIb)

H 2 N-CH 2 -A  (IIIb)

in which A is as defined above,

to give a compound of formula (IVb)

followed by

removing the solvent by distillation or under reduced pressure in a temperature range of from 20° C. to 35° C.,

thermally cyclizing the compound of formula (IVb) in the presence of a solvent at a temperature of from 40° C. to 150° C. to give a compound of formula (Vb)

isolating the compound of formula (Vb) by crystallization or removal of solvent, and reacting the compound of formula (Vb) with a compound of formula (VIb)

R 1 -E  (VIb)

where R 1 is as defined above and E is a leaving group selected from the group consisting of chlorine, bromine, iodine, mesylate, tosylate, or SO 2 CH 3 ,

to give compound (I).

2. A process according to claim 1 wherein the reaction of the compound of formula (Va) with the compound of formula (VIa) or the reaction of the compound of formula (Vb) with the compound of formula (VIb) is carried out in the presence of a base.

3. A process according to claim 2 wherein the base is sodium hydroxide or potassium hydroxide.