Azo dyes with absorption bands in the near infrared
Abstract
The first examples of monoazo dyes absorbing in the near infrared (up to 806 nm in dimethyl sulphoxide) have been prepared from 2-(4-amino-2-acetylaminophenylazo)-4-chloro-5-formylthiazoles by condensing the formyl group with suitably electronegative active methylene compounds under base catalysed conditions.