Patent ID: 8362273

Claim:
A process for preparing compounds of the formula I in which R 1 , R 2 , R 3 , R 3a , R 4 and R 5 are each independently hydrogen, branched or unbranched C 1 -C 8 -alkyl, C 2 -C 8 -alkenyl or C 3 -C 8 -alkynyl; C 3 -C 8 -cycloalkyl, aryl or heteroaryl, wherein aryl or heteroaryl are unsubstituted or optionally comprising one or more substituents independently of one another selected from the group consisting of halogen, hydroxy, amino, mercapto, C 1 -C 8 -alkyl, C 1 -C 4 -alkoxy, C 1 -C 4 -alkylthio, C 1 -C 4 -alkylamino, C 1 -C 4 -haloalkyl, C 1 -C 4 -haloalkoxy, C 1 -C 4 -haloalkylthio, C 3 -C 8 -cycloalkyl, alkenyl, aryl, carbonitrile, carboxylic ester and aldehyde; R 6 , R 7 are each independently C 1 -C 8 -alkyl or C 3 -C 8 -cycloalkyl; comprising (i) alkylating a compound of the formula (III) to form a compound of formula (II) wherein A is halogen, p-toluenesulfonate, methanesulfonate, trifluoromethanesulfonate or A 01 SO 4 , in which A 01 is C 1 -C 8 -alkyl or C 3 -C 8 -cycloalkyl; wherein the alkylating step is carried out at a pressure below 300 bar; and (ii) hydrolysing the compound of the formula (II) with water in the presence of a base.