具有叶绿素基本碳架的二氢卟吩类衍生物的Gewald反应研究

以脱镁叶绿酸-a甲酯1为起始原料，选择硝酸铊为氧化剂对其3-位乙烯基进行氧化，以78％的产率得到缩醛氧化产物2，通过在乙酸中的回流，G 步完成3-位缩醛的解除和13^2-位甲氧甲酰基的消去，以67％的收率形成3-甲酰甲基焦脱镁叶绿酸-a甲酯3．经亲电取代反应在20-位上引进硝基而生成硝化二氢卟吩醛4，然后，在碱性条件下与元素硫和丙二腈进行Gewald反应，完成3-位噻吩基取代的焦脱镁叶绿酸-a甲酯5；而在相同反应条件下的E-环羰基的Gewald反应仅给出氧化产物．同时，对C3-五元杂环的形成过程进行了探讨，并且提出了可能的反应机理．所得新化合物的化学结构经IR，1HNMR及元素分析予以确定．

Gewald Reaction of Chlorine Derivatives with the Basic Skeleton of Chlorophyll

Methyl pyropheophorbide-a 1 is used as starting material and oxidized into chlorine acetal 2 in the yield of 78% by the oxidation for C3-vinyl group with thallium(III) nitrate.The removing for acetal group and carbomethoxyl group are carried out in one step by refluxing in acetic acid to give 3-formylmethyl-3-devinyl pyropheophorbide-a 3 in 67%.The nitro-group is introduced into 20-meso position by electrophilic substitution to produce nitrified chlorin aldehyde 4.Under alkaline condition the Gewald reaction of 4 with malononitrile and sulfur accomplish the synthesis of chlorine 5 substituted with thiophene ring at 3-position,the same Gewald reaction with carbonyl linked with E-ring just give oxidiazed products.The forming processes of five-membered heterocyclic ring is discussed and the reaction mechanisms are tentatively proposed.The structures of all new compounds are assigned based on the data from IR,1HNMR,MS and elemental analysis.