Patent ID: 6894164

Claim:
A process for preparing phthalazines of formula and salts thereof wherein Py represents a 2, 3 or 4-pyridinyl group optionally substituted by one or more substituents selected from halogen, nitro, cyano, oxo and carboxy: R and R1, which may be the same or different between them, represent hydrogen, C 1 -C 6 alkyl or a group OR 2 wherein R 2 represents a linear or branched C 1 -C 6 alkyl, a C 4 -C 7 cycloalkyl or a C 1 -C 6 polyfluoroalkyl; is a single or double bond; Y represents two hydrogen atoms or a group ═O when is a single bond, or when is a double bond Y is hydrogen, cyano, (C 1 -C 4 )-alkoxycarbonyl, amido, optionally sustituted aryl or heterocyclyl, (C 1 -C 8 )-alkyl, (C 1 -C 8 )-cyclylamino; W is absent when is a double bond or, when is a single bond, it represents a) hydrogen; b) (C 1 -C 6 )-alkyl optionally substituted by aryl, heterocyclyl or by a group COR 5 wherein R 5 is hydroxy, (C 1 -C 4 )-alkoxy or hydroxyamino; c) —COR 6 wherein R 6 is hydrogen, aryl, aryl-(C 1 -C 6 )-alkyl, optionally alkylated or monohydroxylated amino, hydroxy, (C 1 -C 4 )-alkoxy, carboxy, (C 1 -C 4 )-alkoxycarbonyl, or (C 1 -C 4 )-alkyl optionally substituted by a heterocycle; d) (C 1 -C 4 )-alkylsulfonyl; which comprises the preparation of an intermediate of formula I wherein R, R 1 and Py have the above reported meanings and the bond indicates both the isomers E and Z; wherein said process comprises reacting a compound of formula II wherein R and R 1 have the meanings above reported; with an aldehyde of formula Py-CHO (III) wherein Py has the above reported meaning; by heating of the mixture of the compounds of formula II and III in the presence of an anhydride and optionally in admixture with a suitable solvent, to form the intermediate of formula I and subsequently reacting the intermediate of formula I with hydrazine monohydrate to form a phthalazine of formula IV.