Prepn of anti-psychotic pyrimidinone - which is 3-(2-(4-(6-fluoro- 1,2-benzisoxazol 3-yl)piperidino) ethyl)-2-methyl- 6,7,8,9-tetra- hydro-4H-pyrido (1,2-a) pyrimidin-4-one

Prepn. of 3-(2-(4-(6-fluoro-1,2 -benzisoxazol-3-yl) piperidino)ethyl) -2-methyl-6,7,8,9- tetrahydro-4h-pyrido -(1,2-a) pyrimidin-4-one. (I) comprises reacting a cpd. of formula ZCH2CH2L with 4-(2,4-difluoro benzoyl)piperidine to give 3-(2-(4-(2,4- difluorobenzoyl) piperidin)-ethyl) -2-methyl-6,7,8,9- tetrahydro-4H-pyrido (1,2-a) pyrimidin-4-one, which is reacted with hydroxylamine hydrochloride to give the corresp. oxime 3-(2-(4-(1-(2,4- difluorophenyl)-1- (hydroximino)methyl) piperidin)ethyl) -2-methyl-6,7,8,9- tetrahydro-4H-pyrido (1,2-a)pyrimidin-4-one which is cyclised under basic conditions to give (I). PROCEDIMIENTO PARA LA OBTENCION DE 3-[2- [4-(6-FLUORO-1, 2-BENZISOXAZOL-3-IL) PIPERIDI-NO] ETIL] -2-6,7,8,9-TETRAHIDRO-4H-PIRIDO [1,2-A] PIRIMIDIN-4-ONA. EL PROCEDIMIENTO CONSISTE EN HACER REACCIONAR UN COMPUESTO DE FORMULA Z-CHSI2 SC CHBS2 SC-L, DONDE Z ES EL RADICAL 2-METIL-4-OXO-6,7,8,9-TETRAHIDRO-4H-PIRIDO [1,2-ALPIRIMIDIN-3-ILO Y L UN GRUPO SALIENTE COMO HALOGENO O UN ALQUIL O ARILSULFONILO, CON LA 4-(2,4-DIFLUOROBENZOIL) PIPERIDINA, PARA DAR LA 3-[2- [(2,4-DIFLUOROBENZOIL) PIPERIDINI] ETIL]-2-METIL-6,7,8,9-TETRAHIDRO-4H-PIRIDO- [1,2-A] PIRIMIDIN-4-ONA, QUE POR REACCION CON HIDROCLORURO DE HIDROXILAMINA DA LA CORRESPONDIENTE OXIMA 3-[2- [4-(2, 4-DIFLORUOFENIL)-1-(HIDROXIMINO) METIL] PIPERIDINI] ETIL]-2-METIL-6,7,8,9-TETRAHIDRO-4H-PIRIDO [1,2-A] PIRIMIDIN-4-ONA, LA CUAL SECICLA EN CONDICIONES BASICAS A LA 3-[2-[4- (6-FLUORO-1, 2-BENZISOXAZOL-3-IL) PIPERIDINO) ETIL]-2-METIL-6,7,8,9-TETRAHIDRO-4H-PIRIDO [1, 2-A] PIRIMIDIN-4-ONA. SE OBTIENE EL COMPUESTO 3-[2- [4- (6-FLUORO-1, 2-PIRIDO [1,2-A] PIRIMIDIN-4-ONA, DE FORMULA I. DICHO COMPUESTO TIENE APLICACIONES FARMACEUTICAS POR SUS PROPIEDADES ANTISICOTICAS. Procedure for obtaining 3-[2-[4-(6-fluoro-1,2-benzisoxazol-3-yl)piperidin]ethyl]-2-methyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidin-4-one.The procedure consists in reacting a compound with formula Z-CH2-CH2-L, where Z is the 2-methyl-4-oxo-6,7,8,9- tetrahydro-4H-pyrido[1,2-alpyrimidin-3-yl and L a salient group such as halogen or an alkyl or aryl sulfonyl, with 4-(2,4-difluorobenzoyl) piperidin, to obtain 3-[2-[4-(2,4-difluorobenzoyl) piperidin]ethyl]-2-methyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidin-4-one, which by reaction with hydroxylamine hydrochloride gives the corresponding 3-[2-[4-[1-(2,4-difluorophenyl)-1-(hydroxamine) methyl] piperidin] ethyl]-2-methyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-alpyrimidin-4-one oxime, which is cyclised in bas