| abstract |
A process for the preparation of a compound of formula (I) and of a acid salt (T) wherein R 1 is selected from the group consisting of alkyl, aryl, cycloalkyl, heteroalkyl, heteroaryl and heterocycloalkyl, R 2 and R 3 , are, independently of each other, selected from the group consisting of alkyl, aryl, cycloalkyl, heteroalkyl, heteroaryl and heterocycloalkyl, R 4 , R 5 , R 6 and R 7 , are independently of each other, selected from the group consisting of H, alkyl, aryl, cycloalkyl, heteroalkyl, heteroaryl and heterocycloalkyl, and wherein the acid salt is a 2,3-Ditoluoyl tartaric acid salt, 2,3-Dibenzoyl tartaric acid salt, 2,3-Dianisoyl tartaric acid salt, 2,3-Dibenzoyl tartaric acid mono(dimethylamide) salt or a mixture of two or more thereof, wherein the tartaric acid salt (T) of the compound of formula (I) contains at least 90 % by weight of the tartaric salt of the compound of formula (Ia) based on the total weight of the acid salt of the compound of formula (I). |