A convenient, novel, and metal-free method for the synthesis of 4,4′-diaminotriarylmethanes (DTMs) is described. This process is based on a one-pot condensation of benzylamines with N,N-dimethylaniline derivatives using 4,6-dihydroxysalicylic acid as a co-oxidant and N-iodosuccinimide as an oxidant. To the best of our knowledge, the present method provides the first reported synthesis of DTMs from benzylamines via oxidative C–N bond cleavage and subsequent double C–C bond formations. The obtained DTMs were then easily converted into a series of blue dyes upon treatment with tetrachloro-1,4-benzoquinone (chloranil). Although the production of triarylmethane dyes tends to require the use of toxic heavy metals, the present method is advantageous in that it is a metal-free and straightforward process.

中文翻译：

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无金属的蓝染料合成：在水杨酸作为助氧化剂的条件下，苄胺和N，N-二甲基苯胺的氧化偶联生成4,4'-二氨基三芳基甲烷

描述了一种方便，新颖且无金属的合成4,4'-二氨基三芳基甲烷（DTM）的方法。该方法基于苄胺与N，N-二甲基苯胺衍生物的一锅缩合，使用4,6-二羟基水杨酸作为助氧化剂，N-碘代琥珀酰亚胺作为氧化剂。据我们所知，本方法首次报道了通过氧化C-N键断裂和随后的双C-C键形成从苄胺合成DTM的方法。然后，在用四氯-1,4-苯醌（氯腈）处理后，将获得的DTM轻松转化为一系列蓝色染料。尽管三芳基甲烷染料的生产倾向于需要使用有毒的重金属，但是本方法的优点在于它是无金属且简单的方法。