The amidomethylation and bromination of Fischer's base.The preparation of some new polymethine dyes

The amidomethylation of Fischer's base (1,3,3-trimethyl-2- methyleneindoline) with N-hydroxy-methylphthalimide gives, as the main product, the 5-phthalimidomethyl derivative (4). This compound has been converted into its parent amine (5) from which a N-chloroacetyl derivative (6) was readily obtained. Fischer's base reacted with one equivalent of dibromoisocyanuric acid to give the 5-bromo derivative (7) and with two equivalents to give the 5,6-dibromo derivative (8). All five substituted Fischer's bases have been used to prepare representative polymethine dyes, the ultraviolet spectral and lightfastness (on wool) properties of which are described. Dyes containing one bromine atom impart particularly brilliant shades to wool. A dye containing the N-chloro-acetamidomethyl substituent proved to be fibre-reactive.