Calix pyrrole expanded

While interesting neutral alternatives to the unsaturated expanded porphyrin derivatives, calix[n] pyrroles (n = 4, 5, 6, 8) are relatively limited in their scope for anion binding because of the constraints of the cavity size. Nevertheless pyrroles linked by an sp3 hybridised carbon atom are of considerable interest because of their resemblance to the anti-cancer agents the prodigiosins (Section 4.2.4), moreover pyrrole anion-receptor chemistry is synthetically versatile and hence a range of acyclic pyrroles and hybrid amidopyrroles such as 4.50-4.52 have been developed, particularly by the groups of... 

Sessler and coworkers have prepared fluorinated calix[4]pyrroles (97 = 1) and expanded calixpyrroles (98 n = 2-5) by the condensation of 3,4-difluoropyrrole with acetone under acid catalysis (Fig. 3.47). The fluorinated dipyrrolylqumoxaline 99 was also synthesized from 3,4-difluoropyrrole. These were studied as neutral anion receptors that had higher affinity and greater selectivity relative to their nonfluorinated congeners. 

FIGURE 3.47 Fluorinated calix[4]pyrroles and expanded calixpyrroles and a fluorinated dipyrroly Iquinoxaline. 

Recently Cafeo, Kohnke and co-workers have continued work on expanded caUxpyrroles and have reported the anion-binding properties of two calix[2]benzo[4]pyrroles 51a and 51b [69]. 

Sessler. J.L. Anzenbacher, P., Jr. Shrives. J.A. Jursikova, 38. K. Lynch, V. Marquez, M. Direct synthesis of expanded fluorinated calix[/r]pyrroles Decafluorocalix[5]pyrrole... 

Sessler and coworkers expanded the calix[4]pyrrole binding cavity by employing bipyrrole in place of pyrrole, yielding new calixpyrrole analogs such as calix[n]bipyrroles" (n = 3, 4), a calix[2]bipyrrole[2]furan, and a calix[2]bipyr-role[2]thiophene. The carbazole moiety was also an attractive linker to include as the fluorescent nature of... 

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