NEW MATERIAL:A fluorine-containing benzoazine shown by formula II (X is O or NH; Y is CO or SO2; Rf is fluorine-containing alkyl).

EXAMPLE: 2-Trifluoromethyl-2H-1,3-benzoxazin-4(3H)-one.

USE: A hypotensive diuretic or a precursor thereof.

PREPARATION: A pressure reaction tube is charged with water, an ether and silica gel fine powder, a compound shown by formula III is condensed in the reaction tube and reaction is carried out at 100°C for 12hr to give a compound shown by formula I. Then, this compound is reacted with a compound shown by formula IV (Y is CO when X is O or Y is SO2 when Y is NH) under reflux in dioxane. Consequently, firstly OH or NH2 nuceophilically attacks the α-position and decarbonation and dehydration occur to give a compound shown by formula V.