NIR chromophores from small acetylenic building blocks: a Diels–Alder approach to octaalkynylphthalocyanines
作者:Rüdiger Faust、Frieder Mitzel
DOI:10.1039/b006114j
日期:——
Two new routes to cross-conjugated 3,4-dimethylenehexa-1,5-diynes, both starting from dialkynyl 1,2-diones, have been devised. Whereas triisopropylsilyl-protected diketones could be diolefinated in a bis-Wittig reaction with methylenetriphenylphosphorane, their aryl-terminated congeners had to be subjected to the conditions of the Peterson olefination (trimethylsilylmethylmagnesium chloride and subsequent dehydration of the resulting diol with thionyl chloride). The reactivity of the diethynylbutadienes towards standard dienophiles was found to be low and alternative thermal reactions compete with [4Â +Â 2] cycloadditions. However, dicyanoacetylene was shown to be an effective cycloaddition partner leading, after aromatisation, to the corresponding dicyanodiethynylbenzenes. These were cyclotetramerised with magnesium butanolate in butanol to furnish octaalkynylphthalocyanines, thereby completing a concise, three-step synthesis of these NIR chromophores of relevance to photodynamic forms of therapy.
研究人员设计了两条新的路线,从 1,2 二炔基二酮出发,制备交叉共轭的 3,4-二亚甲基六-1,5-二炔。三异丙基硅烷保护的二酮类化合物可以在与亚甲基三苯基膦的双维蒂希反应中进行二烯化反应,而其芳基封端的同系物则必须在彼得森烯化反应的条件下进行(三甲基硅甲基氯化镁,然后用亚硫酰氯对生成的二元醇进行脱水)。研究发现,二炔丁二烯与标准亲二烯的反应活性较低,替代热反应与[4Â +Â 2]环加成反应存在竞争。不过,二氰基乙炔被证明是一种有效的环加成伙伴,经过芳香化后可生成相应的二氰基二炔基苯。这些化合物在丁醇中与丁酸镁发生环四聚反应,生成八烷基炔基酞菁,从而完成了与光动力疗法相关的近红外发色团的简明三步合成。