Patent ID: 8283502

Claim:
A process for the preparation of a compound of formula or mirror image wherein R 1 is selected from the group consisting of hydrogen, C 1-6 -alkyl and (C 1-6 -alkoxy) carbonyl, any alkyl or alkoxy optionally being substituted with one or more halogen atoms, R 2 is selected from the group consisting of aryl, aralkyl, C 1-6 -alkyl and (1′—R 3 )—C 3-6 -cycloalkyl wherein R 3 is hydrogen, methyl or ethyl, any of said aryl, aralkyl, alkyl is optionally substituted with one or more halogen atoms, and A is selected from the group consisting of C 1-20 -alkyl, C 3-6 -cycloalkyl, aryl and aralkyl, any of said cycloalkyl, aryl and aralkyl is optionally annellated to one or more further 5 to 7 membered carbocyclic or heterocyclic rings, and/or any of said alkyl, cycloalkyl, aryl and aralkyl is optionally substituted with one or more halogen atoms, cyano, C 1-6 -alkyl, C 3-6 -cycloalkyl, —NR 4 R 5 , —SR 6 and/or —OR 7 , and wherein said alkyl and cycloalkyl substituent attached to A is optionally substituted with one or more halogen atoms, and wherein R 4 and R 5 independently are hydrogen or C 1-6 -alkyl, or wherein R 4 is hydrogen and R 5 is C 2-7 -acyl or (C 1-6 -alkoxy)carbonyl, wherein each acyl and alkoxy in R 5 is optionally substituted with one or more halogen atoms, or wherein R 4 and R 5 together with the nitrogen atom form a 5 to 7 membered heterocyclic ring, or wherein R 4 and R 5 together are ═CH-aryl, the aryl moiety optionally being substituted with one or more halogen atoms, —NH 2 , —NH(C 1-6 -alkyl), —N(C 1-6 -alkyl) 2 or C 1-6 -alkyl, or R 4 and R 5 together are ═CH—N(C 1-6 -alkyl) 2 , and wherein R 6 is C 1-6 -alkyl, optionally substituted with one or more halogen atoms, and wherein R 7 is hydrogen or C 1-6 -alkyl, optionally substituted with one or more halogen atoms, or wherein A and R 1 together form a 5 to 7 membered carbocyclic or heterocyclic rings, optionally substituted with one or more halogen atoms, cyano, C 1-6 -alkyl, C 3-6 -cycloalkyl, —NR 4 R 5 , —SR 6 and/or —OR 7 , wherein R 3 , R 4 , R 5 , R 6 and R 7 are as defined above, said process comprising the steps of (i) preparing a mixture of a zinc(II) catalyst, an initial amount of the compound of formula I in a molar ratio to the zinc(II) catalyst from 0.1:1 to 2:1, and optionally a further chiral auxiliary in a molar ratio to the zinc(II) catalyst of 0.1:1 to 3:1, and (ii) adding to said mixture (a) a compound of formula wherein A and R 1 are as defined above, and (b) a base, and (c) a compound of formula wherein R 2 is as defined above, at a temperature from −78 to 30° C., and (iii) heating the mixture obtained in step (ii) to 10 to 50° C. until completion of the reaction, to obtain the compound of formula I.