| http://www.w3.org/ns/prov#value | - The intermediate compound of formula (III) is preferably prepared in situ without isolation by reacting a compound of formula ##STR11## in which R is an ester group, preferably C1-4 alkyl, with N-methylpiperazine, by heating to a temperature of between 30??? C. and 120??? C., for example about 100??? C., in a suitable solvent such as for example anisole, and employing TiCl4 as catalyst.
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