Patent ID: 7141681

Claim:
A process for preparing a compound of general formula (I), wherein R 1 is a C 1 –C 8 -alkyl, C 6 –C 10 -aryl-C 1 –C 4 -alkyl or C 3 –C 8 -cycloalkyl-C 1 –C 4 -alkyl group, and R 2 is a C 1 –C 8 -alkyl group, comprising: reacting a) a ketone of formula (II) wherein R 1 and R 2 are as hereinbefore defined, with an acetoacetate in the presence of a strong base and b) cyclising the resulting compound of formula (IV) wherein R 3 denotes a C 1 –C 4 -alkyl or benzyl group, by means of a base, wherein a compound of formula II is continuously mixed and reacted with an acetoacetate in the form of its dianion in a microreactor, and subsequently isolating the product compound of the general formula (I).