A method for preparing a fused oxazinone is disclosed in which (1) a carboxylic acid is contacted with a sulfonyl chloride in the presence of an optionally substituted pyridine compound, the nominal mole ratio of sulfonyl chloride to carboxylic acid being from about 0.75 to 1.5; (2) the mixture prepared in (1) is contacted with an ortho-amino aromatic carboxylic acid in the presence of an optionally substituted pyridine compound, the nominal mole ratio of the ortho-amino aromatic carboxylic acid to carboxylic acid charged in (1) being from about 0.8 to 1.2; and (3) additional sulfonyl chloride is added to the mixture prepared in (2), the nominal mole ratio of additional sulfonyl chloride added in (3) to carboxylic acid charged in (1) being at least about 0.5. Also disclosed is a method for preparing a compound of Formula III, using a compound of Formula 1a that is characterized by preparing the fused oxazinone of Formula 1a by the method above, using a compound of the formula LS(O).sub.2Cl as the sulfonyl chloride, a compound of Formula 2' as the carboxylic acid, and a compound of Formula 5' as the ortho-amino aromatic carboxylic acid (FORMULA 1a) (FORMULA III) (FORMULA 2') (FORMULA 5') wherein L, X, Y and R.sup.1 through R.sup.9 are as defined in the disclosure ##STR00001##