Pyrimidine derivatives

Pyrimidine derivatives of the formula I in which =A-B= denotes =CH-CH= or =N-CR =, Alk denotes an alkylene group having 2-4 C atoms, R denotes H, dialkylaminoalkyl, carboxyalkyl, alkoxycarbonylalkyl, carbamoylalkyl, N-alkylcarbamoylalkyl or N,N-dialkylcarbamoylalkyl, Y denotes CH or N, Z denotes a bond or -CO-, Ar denotes a phenyl, thienyl or pyridyl group which is unsubstituted or mono- or polysubstituted by alkyl, alkoxy, F, Cl, Br, I and/or CF3 and R denotes H, alkyl, alkoxy or alkylthio, in which the alkyl, alkoxy and alkylthio groups in each case contain 1-4 C atoms, and their salts exhibit hypotensive properties.