Porphyrins with exocyclic rings. Part 3. A reassessment on the utility of cyclopenta[b]pyrroles in the synthesis of porphyrin molecular fossils. Preparation of three type II porphyrins related to deoxophylloerythroetioporphyrin (DPEP).
作者:Timothy D. Lash、James J. Catarello
DOI:10.1016/s0040-4020(01)85734-3
日期:1993.1
cyclopenta[b]pyrroles in porphyrin synthesis has been reinvestigated. A 6-oxocyclopenta[b]pyrrole 18 was prepared by cyclization of the propanoyl chloride sidechain of an α-unsubstituted pyrrole 17d in the presence of tin(IV) chloride. Subsequent reduction with sodium borohydride afforded the corresponding 6-hydroxy compound 10 and further acid catalyzed condensation with α-unsubstituted pyrroles 11a and
环戊并[b]吡咯在卟啉合成中的效用已被重新研究。通过在氯化锡(IV)存在下将α-未取代的吡咯17d的丙酰氯侧链环化来制备6-氧代环戊[b]吡咯18。随后用硼氢化钠还原得到相应的6-羟基化合物10,并与α-未取代的吡咯11a和11b进行进一步的酸催化缩合,以优异的产率得到了新型的6-吡咯基环戊[b]吡咯22a和22b。尝试制备脱氧叶绿素铁卟啉(DPEP; 2),这是一种广泛的沉积卟啉分子化石,使用三茂铁-a,c-比拉二烯路线从这些二吡咯中间体得到的结果是不成功的。然而,使用麦克唐纳缩合法成功地进行了三种相关的内消旋β-乙基卟啉的合成,收率中等至良好。在中间开链四吡咯的环戊烯环稠合位点保留sp 3杂化碳桥在大环形成过程中似乎至关重要,因为这会减少外围取代基和碳环之间的空间排斥。