| abstract |
A process for the preparation of compounds of formula I ** see formula ** in which R1, R2 and R3 are each independently of the other hydrogen or C1-C4 alkyl, comprising a) reacting a compound of formula II * * see formula ** in which R 2, R 2 and R 3 are as defined for formula I and X is bromine or chlorine, with a compound of formula III ** see formula ** in which R4 is hydrogen or C1-C4 alkyl, in the presence of a base and catalytic amounts of at least one compound of palladium complex, to form a compound of formula IV ** see formula ** in which R 1, R 2 and R 3 as defined for formula I and R 4 it is as defined for formula III; and b) converting that compound, using a reducing agent, into the compound of formula I. |