| 摘要 |
A process for the preparation of a compound of formula (I) or a salt thereof wherein R is an amino, nitro or -NHCOR<SUB>1 </SUB>group, wherein R<SUB>1 </SUB>is C<SUB>1</SUB>-C<SUB>6 </SUB>alkyl or phenyl optionally substituted by a -O-(CH<SUB>2</SUB>)<SUB>n</SUB>-phenyl group, wherein n is an integer of 1 to 6; comprising reacting a compound of formula (II) or a salt thereof, both as the individual isomer and as an isomeric mixture, wherein R is as defined above; with a dehydrating agent, if necessary in the presence of an organic solvent, and optionally in the presence of a basic agent; and, if desired, converting a compound of formula (I) to another compound of formula (I) or a salt thereof.
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