Synthesis Of Oxalylamino-substituted Indoaniline Dyes

Thermal dye sublimation transfer is a recording mode. A dye-donor element is provided with a dye layer containing sublimable dyes, which has heat transferability. The dye-donor element is connected to a receiver sheet or receiver element and can select a pattern information signal. It is heated through thermal printing head with many juxtaposed heating-generating resistors, the sublimable dyes are transferred from the dye-donor element to the receiver and a pattern is formed finally.The dyes used for thermal sublimation transfer are normally disperse dyes with moderate molecular weight and thermal sublimability. The yellow dye and magenta dye can be filtrated from the commercial disperse dyes, respectively. However, there is no suitable blue commercial sublimable dye to choose because of its deep color. As a result, the blue sublimable dye needs to be designed and synthesized.Oxalylamino-substituted indoaniline dyes were a type of blue thermal sublimation dyes which were developed and applied in recent years. In this paper, a series of oxalylamino substituted indoaniline dyes were synthesized to filtrate out the appropriate blue dyes for thermal sublimation transfer. Firstly, Oxalyl chloride monoester was synthesized from oxalyl chloride and different alcohols, which reacted with o-aminophenol to obtain alkyl 2-((2-hydroxyphenyl)amino)-2-oxoacetate, and then condensed with p-aminodimethylaniline hydrochloride. The process was optimized, and yield of oxidation-step was from 47.6 to 58.6%. The melting points of compounds were from 64 to 141℃. Secondary, N-(2-hydroxy-phenyl)benzamide was synthesized from benzoyl chloride and o-aminophenol, which condensed with p-aminodimethylaniline hydrochloride to obtain N-(3-((4-(dimethylamino)-phenyl)imino)-6-oxocyclohexa-1,4-dien-1-yl)benzamide.Melting point and ultraviolet absorption of the designed dyes were also determined. The results showed the melting point decreased with increasing of carbon number of branched chain. The change of compound structure had little effect on the maximum wavelength of ultraviolet absorption, which ranged from 609 nm to 614 nm in ethyl acetate solution.