Patent ID: 7534812

Claim:
A process for preparing a compound of formula 1, wherein: R 1 , R 2 and R 3 are independently C 1-6 -alkyl, C 2-6 -alkenyl, C 2-6 -alkynyl or aryl; and R 4 is H, OC 1-6 -alkyl, Oaryl, OH, C 1-6 -alkyl, halogen, CN or NO 2 ; comprising the steps of: a) treating an acrylic acid compound of formula 4 with an HBr solution to form a mixture and reacting the mixture with a compound of formula 5 in the presence of aluminum chloride to form a compound of formula 3; b) optionally converting the compound of formula 3 produced in step a) into an acid halide or an anhydride; c) treating the compound of formula 3, or the acid halide or anhydride thereof, with a Lewis acid followed by reacting the compound of formula 3 with a C 1-6 -alkyl nitrite to form a compound of formula 2; and d) reacting the compound of formula 2 in the presence of a base with a sulfonic acid halide, saponifying followed by hydrolyzing to form the compound of formula 1, wherein R 1 -R 4 of compounds of formulas 2-5 are as defined above.