Patent ID: 7514584

Claim:
A process for the preparation of a compound of formula I wherein R 1 , R 2 and R 3 are each independently of the others hydrogen or methyl, which comprises a) reaction of a compound of formula II wherein R 1 , R 2 and R 3 are as defined for formula I, either a1) with triphenylphosphine dibromide or triphenylphosphine dichloride or a2) with RSO 2 Cl, wherein R is C 1 -C 4 alkyl, C 1 -C 4 fluoroalkyl, benzyl, phenyl, nitrophenyl, halophenyl or C 1 -C 6 alkylphenyl, in the presence of a base, to form a compound of formula III wherein X is OSO 2 R, wherein R is C 1 -C 4 alkyl, C 1 -C 4 fluoroalkyl, benzyl, phenyl, nitrophenyl, halophenyl or C 1 -C 6 alkylphenyl, or is bromine or chlorine and R 1 , R 2 and R 3 are as defined for formula I; and b) reaction of that compound in the presence of a base to form a compound of formula IV wherein R 1 , R 2 and R 3 are as defined for formula 1; and c) conversion of that compound in the presence of a reducing agent into a compound of formula I.