PURPOSE: To readily convert 2-hydroxyalkylaminoacylaminobenzophenones to tricyclic benzodiazepins useful for sleeping medicines, etc., without using a complicate purification method, a reagent difficult to handle or expensive facility by heating the benzophenone derivatives in a specific organic solvent in the presence of boric acid and an aminoalcohol.

CONSTITUTION: 2-Hydroxyalkylaminoacylaminobenzophenone of formula I (R and R" each is a halogen, methyl or nitro; R' is H or lower alkyl; n is ≥2) is heated in an inert organic solvent having 70-130°C boiling point (e.g. benzene), in the presence of boric acid and an aminoalcohol having the same structure as the hydroxyalkylamino group to convert the benzophenones to a tricyclic benzodiazepins of formula II.