Synthesis and antifungal activity of some new quinazoline and benzoxazinone derivatives.

The hitherto unknown 2-isopropyl-6,8-dibromo-4H-3,1-benzoxazin-4-one (2) was subjected to condensation with either primary or secondary amines affording the benzamide derivatives (3-7), while with alcohols in presence of the base, corresponding esters were obtained (8 and 9). Acylation of the hydrazide (12) or its cyclized form (13) gave (14-17). The quinazolinone derivative (18) was obtained either when (12) was reacted with nitrous acid or via fusion of (2) with ammonium acetate. The thione (20) which was obtained via reaction of (18) with Lawesson's reagent, was subjected to either alkylation yielding (21-25) or desulphurization with primary amines affording (26 and 27). Treatment of (18) as well as (20) with a chlorinating agent provided (29, 30) and (28, 29) mixtures, respectively. Ten of our compounds were examined against Sclerotium cepivorum as well as Botrytis allii on PDA media. These compounds showed a significant reduction of mycelial growth and scleratia number of these fungi which cause the white rot and neck rot diseases of onion.