Electrophilic substitution in n-aryl-2-pyrazolines: Reactions with 1,3-dithioles

Dyes that absorb at 525–580 nm were obtained by the reaction of derivatives of 1,3-dithiolium iodide (or perchlorate) with 1-phenyl-3,5-di-R-2-pyrazolines, N,N-dimethylaniline, and benzaldehyde N-methylphenylhydrazone. It was demonstrated by alternative synthesis that the reaction takes place in the para position of the N-phenyl group. Dyes can be obtained in two steps from 2-dimethylamino-1,3-dithioles and activated aromatic compounds with subsequent oxidation of the intermediate leuco compounds with air oxygen.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1245–1250, September, 1981.