Patent ID: 7012151

Claim:
A process for preparing an alkyl 4-alkanoylamino-3-alkyl-5-nitrobenzoate of the formula I wherein R 1 is H or C 1-6 -alkyl; R 2 is H or C 1-6 -alkyl; R 3 is H; and R 4 is H or C 1-5 -alkyl-carbonyl, or R 3 and R 4 together form a succinyl, glutaryl or adipinyl group, which process comprises the following steps: (a) dissolving an alkyl 4-alkanoylamino-3-alkyl-benzoate of the formula II wherein R 1 , R 2 , R 3 and R 4 are as hereinbefore defined, at a temperature that is less than 10° C., in a solvent mixture comprising 1.5-2.5 mol of sulphuric acid, 1.5-2.5 mol of nitric acid and 2-6 mol of water per mol of the alkyl 4-alkanoylamino-3-alkyl-benzoate of formula II and, (b) at a temperature between −20 and +10° C., nitrating the compound of formula II by adding to the mixture produced by step (a) 6-10 mol of nitric acid per mol of the alkyl 4-alkanoylamino-3-alkyl-benzoate of formula II, to yield the compound of formula I.