Process for the preparation of a n-alkylated bipyrazoleanthrone
AssigneeCiba-Geigy Corporation
InventorRainer Hildebrand
Life of this patent
Estimating the term…
Abstract
A N-alkylated 2,2'-bipyrazoleanthrone of formula ##STR1## wherein R is C.sub.1 -C.sub.8 alkyl, is prepared by dimerising a 1,9-pyrazoleanthrone of formula ##STR2## in the presence of an alkali metal hydroxide and an alkanol of 1 to 5 carbon atoms and at elevated temperature, and reacting the resultant intermediate of formula ##STR3## wherein Me is an alkali metal cation, with an alkyl halide which introduces the alkyl radical R, in the molar ratio 1:2, and in the presence of an alkylene glycol or a C.sub.1 -C.sub.4 alkyl ether thereof as catalyst. The N-aklylated bipyrazoleanthrone is suitable for use as a vat dye.
Claims9
A process for the preparation of a N-alkylated 2,2'-bipyrazoleanthrone of formula ##STR8## wherein R is C.sub.1 -C.sub.8 alkyl, which process comprises dimerising a 1,9-pyrazoleanthrone of formula ##STR9## in the presence of an alkali metal hydroxide and an alkanol of 1 to 5 carbon atoms and at elevated temperature, and reacting the resultant intermediate of formula ##STR10## wherein Me is an alkali metal cation, with an alkyl halide which introduces the alkyl radical R, in the molar ratio 1:2, and in the presence of an alkylene glycol or a C.sub.1 -C.sub.4 alkyl ether thereof as catalyst.
Dependencies are inferred from the claim text.