Porphyrins with exocyclic rings. Part 12. Synthesis of meso,β-butano- and meso,β-pentanoporphyrins from cycloalka[b]pyrroles
作者:Jolie A. Bastian、Timothy D. Lash
DOI:10.1016/s0040-4020(98)00327-5
日期:1998.6
Knorr-type condensations with cycloheptanone or cyclooctanone, respectively. Treatment with lead tetraacetate in dichloromethane afforded the labile ω-acetates 8 and subsequent acid catalyzed condensation with α-unsubstituted pyrrole-2-carboxylates yielded the related pyrrolylcycloalka[b]pyrroles 29 and 30. The α-unsubstituted pyrroles 14 and 23 were prepared by condensing α,β-unsubstituted ketones, or their
具有b面稠合的七元或八元碳环的吡咯5分别通过与环庚酮或环庚酮的克诺尔缩合反应以高收率制备。在二氯甲烷中用四乙酸铅处理得到不稳定的ω-乙酸酯8,随后酸催化与α-未取代的吡咯-2-羧酸酯的缩合反应,产生了相关的吡咯基环烷基[b]吡咯29和30。α-未取代的吡咯14和23的制备方法是:在DBU存在下,将N,甲苯磺酰基苄基乙酸酯与α,β-未取代的酮或其β-乙酰氧基羰基前体缩合,然后用POCl 3脱水。-吡啶和碱催化消除对甲苯磺酸。将二吡咯二苄基酯29和30在10%Pd-C上氢解,得到相应的二羧酸。在改良的MacDonald“ 2 + 2”条件下,酸与二甲酰基二吡咯基甲烷33的缩合反应得到一系列带有7或8元环外环的四个环烷卟啉4a-d。尽管以良好的产率分离出内消旋的β-丁卟啉4a和4b,但相关的内消旋的β-五杂卟啉4c和4d的结果却较差。。有人提出,八元碳环会扭曲开环四吡咯中间体的几何形状,这种有害影响导致所观察到的较低收率。