A process for producing a quinazolin-4-one compound having the formula:
[wherein R
1
, R
2
, R
3
and R
4
each represents a group not participating in the below-mentioned reaction, and R
1
, R
2
, R
3
and R
4
can be combined together to form a ring] which comprises reacting an anthranilic acid derivative having the formula:
[wherein R
5
is a hydrogen atom or a hydrocarbyl group] with a formic acid derivative in the presence of an ammonium carboxylate.