Process for preparing quinazolin-4-one derivatives

A process for preparing a quinazolin- 4-one derivative, the process comprising reacting, in the presence of a base, a trialkylsilyl halide with a compound represented by the formula ##STR26## wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are the same or different and each represent a hydrogen atom, a lower alkyl group, a halogen atom, a nitro group, a lower alkoxy group, a cyano group, an N-lower alkylcarbamoyl group, a lower alkoxycarbonyl group, a lower alkanoyloxy group or a halogen-substituted lower alkyl group;

• R.sup.5 is a phenyl group which may have 1 to 3 substituents each selected from a lower alkyl group, a lower alkoxy group or a halogen atom, a lower alkyl group, a phenyl-lower alkyl group which may have a halogen atom as a substituent on the phenyl ring, a lower alkenyl group, a lower alkoxy-lower alkyl group or a lower alkynyl group;
• R.sup.6 is a lower alkyl group, a halogen-substituted lower alkyl group, a lower alkoxycarbonyl group or a phenyl group which may have, as a substituent, a lower alkyl group or a group of the formula ##STR27## wherein A is an oxygen atom or a single bond, Z is a lower alkylene group, R.sup.7 is a lower alkyl group and R.sup.8 is a lower alkoxy group, a phenyl group or a phenyl-lower alkoxy group which may have a halogen atom on the phenyl ring;
• to produce the quinazolin-4-one derivative being represented by the formula ##STR28## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are as defined above.