G. Kumaran et Gh. Kulkarni, A ONE-STEP SYNTHETIC ROUTE TO N-SUBSTITUTED BENZOXAZINES AND QUIAZOLINEDIONES, Indian journal of chemistry. Sect. B: organic chemistry, including medical chemistry, 33(9), 1994, pp. 877-880
A mild convenient one pot synthesis of 3-alkyl-2, 3-dihydro-2, 4-dioxo
/2-oxo-4-hydroxy-4H-1, 3-benzoxazines (3a-e) and (5a-e) is described,
starting from salicylic acid (1) and salicylaldehyde (4) respectively
by reaction with ethyl N-alkyl carbamates (2a-e) in the presence of PO
Cl3-ZnCl2. Anthranilic acid (6) on reaction with (2a-c) using same rea
gents furnish N-alkyl-2-amino-4H-3, 1-benzoxazine-4-ones (7a-c) and 3-
alkyl-2, 4-(1H,3H)-quinazolinediones (8a-c).