The reactions of maleic anhydrides 1 (R = H. o-Cl, p-Cl, 3,4-Cl2, p-F. p-MeO) with Me3SiN3 gave mixts. of isomeric 4- and 5-aryl-2H-1,3-(3H)- oxazine-2,6-diones 11 and 111 after hydrolysis with 11 predominating. The yield of 111 is greatest from 1 (R =o-Cl) and substantial for other arylmaleic anhydrides, indicating increased importance of steric effects in these reactions. Chem. Abstr. Vol. 84 105513g.