New dyestuffs for polyester fibres—synthesis and comparative tinctorial behaviour of 3‐alkyl‐4‐arylhydrazono‐N1‐picolinoyl‐2‐pyrazolin‐5‐ones and their isomeric pyrid‐3‐ and ‐4‐yl analogues

The condensation reaction of pyridine‐carboxylic acid hydrazides IIa‐d with ethyl butanoylacetate was selectively used to synthesize new azo‐disperse dyes embodying a pyrazolone moiety with a view to evaluating and comparing their dyeing performance on synthetic polymer fibres. Fastness properties of these dyes were of a generally good order, particularly for those of nicotinoyl derivatives VIIIa‐h. Comparison of the promising tinctorial properties (%R, K/S function and Tristimulus values) of the latter products with that of the corresponding oxygenated analogues Xa‐h revealed the advantages of using the former colourants as azo‐disperse dyes for the used polyester fibre.