Macrotricyclic quaternary ammonium salts

A relative of the latter class of compounds are the macrotricyclic quaternary ammonium salts which have been reported by Schmidtchen. The bridges may contain either methylenes or ethyleneoxy units and the nitrogens are quaternarized. The underlying principle is to provide a cavity suitable for solvating or at least trapping anions. Schmidtchen presents evidence which suggests the formation of halide inclusion complexes. The synthesis of these molecules is accomplished along more or less traditional lines Such a species is illustrated above as compound 19. 

In other sections in this chapter, we have referred to a variety of macropolycyclic structures which are more elaborate than the simple three-stranded bicyclic cryptands. This includes bridged double-macrocycles " , in-out bicyclic amines and the macrotricyclic quaternary ammonium salts of Schmidtchen. In addition to these, there are two other types of compounds which deserve special note. The first of these is a stacked twin-ring cryptand, but it is a hybrid molecule rather than a double-cryptand . The species shown below as 20 is a crowned porphyrin, and was designed to provide a pair of metal cation binding sites similar to those which might be available in natural biological systems . 

In yet another study the thiazolium ring was attached to a macrotricyclic quaternary ammonium ion 9, bearing several positive charges to determine if rate accelerations of pyruvate decarboxylation could be observed46. Such rate accelerations could indeed be observed, especially for phenylpyruvic acid as a substrate. In addition, lumiflavin-3-acetic acid as a potential oxidant of the intermediate (see the oxidative decarboxylation pathway in Scheme 1) was shown to be reduced by the pyruvic acid analog in the presence of DBU in ethanol and the macrotricyclic quaternary ammonium salt. 

Inclusion of anions in macrotricyclic quaternary ammonium salts, F. P. Schmidtchen, Angew. Chem. Int. Ed. Engl., 1977, 89, 720. 

E. II Rate Effects Shown by Macrotricyclic Quaternary Ammonium Salts. 117... 

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