1,3-Alternate calix arene, reaction with

The intermediate compound 7 is identified in the H-NMR spectrum by resonances at 5 4.18 CH2) and 7.35 (Ni 2)- Compound 8 has the amine resonance at 6 8.43, which is identifiable by its exchange reaction with D2O. The latter method via the cyanomethoxy intermediate can be used to prepare partially substituted calixarenes, since the addition of chloroacetonitrile to calix[4]arene can be used to selectively substitute the two alternate positions on the lower rim (Equation 8). 

Alternatively, the Sn2 nucleophilic substitution reaction between alcohols (phenols) and organic halides under basic conditions is the classical Williamson ether synthesis. Recently, it was found that water-soluble calix[n]arenes (n = 4, 6, 8) containing trimethylammonium groups on the upper rim (e.g., calix[4]arene 5.2) were inverse phase-transfer catalysts for alkylation of alcohols and phenols with alkyl halides in aqueous NaOH solution to give the corresponding alkylated products in good-to-high yields.56... 

Copper-mediated coupling reactions of / -iodocalixarenes with phthalimide followed by hydrazinolysis should be mentioned as an alternative and independent strategy to obtain p-aminocalixarenes . The carbazole-substituted derivatives 50 (Figure 8) were obtained similarly by Ulhnan coupling . CMPO derivatives (51c), urea compounds (51b), available also via the isocyanates (51a), may be mentioned additionally. Mono- (52) and diimides with acidic functions pointing towards the cavity, and the calix[6]arene-based acetylcholine esterase mimic (53) are more sophisticated examples. 

The influence of the conformation of the calix[6]arene macrocycle was also found in the reactivities of both isomers. While both 16a and 16b reacted with mCPBA to produce the corresponding seleninic acids 17a and 17b, respectively (Scheme 11.8), they showed different reactivities toward a thiol. Although the cone isomer 16a reacted with an excess of 1-butanethiol at room temperature to give selenenyl sulfide 18a, the 1,2,3-alternate isomer 16b underwent no reaction even at 50°C (Scheme 11.9). 

Calix[n]arenes with two mcto-substituted phenolic units in opposite positions may be chiral (Cj symmetry) or achiral Cs symmetry). Addition reactions to 1,3-di-quinone derivatives, in analogy to Equation 3, give a mixture of both isomers, from which for one example the C2 isomer 30 was isolated. The C2 isomer is formed in a more rational way according to Equation 7 with 20% yield in the cyclization step [38]. However the five-step synthesis of the dinuclear precursor means that this, too, is not a very attractive alternative. 

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