The Influences Of Substituents On The Formylations Of Calixarenes On The Upper Rims And The Constructions Of Calixarene-based Nanotubes

Substituent effects, including inductive effect, conjugation effect, hyperconjugation effect,field effect and steric effect, are the generic term for electronic effects and steric effect causedby groups or atoms of the molecules. Substituent effects related to many aspects of organicchemistry, including the physical properties, pH, reactivity of the organic compounds and theorganic reaction types, speed, region selectivity, and products. In calixarene chemistry,substituent effects can be used not only to synthesize host molecules with special structuresand properties by selective modification of calixarenes, but to control the self-assembly ofcalixarenes by changing the types, spatial location, orientation of the substituents. In thispaper, the effects of substituents on the formylations of calixarene and thiacalixarene on theupper rim and the constructions of calixarene nanotubes were studied.In chapter one, the structural characteristics and modifications of calixarenes wereintroduced. The differences of functionalizations of calixarene and thiacalixarene wereexpounded, especially that of the formylation reactions. The effects of substituents on thelower rim and bridging groups in the formylation reactions of calixarens were analyzed andsummarized. In the end, the nanotubes formed by the self-assembly of calixarenes werereviewed. And the effect of substituents in nanotube assembly was analyzed. In light of theabove introduction, the design strategies of this thesis are outlined.In chapter two, the influences of steric effects of substituents on the formylations ofcalixarenes were studied. The steric hinderance of the upper rims of calixarene derivatives indifferent conformations, which were synthesized by introduing propyl or isopropyl groups tothe lower rims, was greatly different due to the different sizes and orientations of substituents.Compared with isopropoxy calixarenes, the steric hinderance effect of propoxy calixarenes ismuch weaker. Therefore, tetrapropoxy compounds in all conformations could be smoothlytransformed into the corresponding tetraformyl derivatives and no alkyl group wasdealkylated. For the tetraisopropoxy calixarenes, with the increase of steric hinderance,1,3-alternate conformer gave exhaustively formylated product with no alkyl groupdealkylating; partial cone conformer gave the tetraformylated proximal A,B-diether in1,3-alternate conformation; and cone conformer led to triformylated derivatives accompaniedby the selective dealkylations of three or two diametrical alkyl groups.In chapter three, the selective formylations of thiacalix[4]arene on the upper rim werestudied. Influenced by the orientation effect of S atoms, thiacalixarene always give metasubstitutions. The selective syntheses of formylated thiacalix[4]arenes on the para positionswere successfully achieved by controlling the types and numbers of the substituents towardthe OH groups of the phenol rings. Di-and triformylated thiacalix[4]arenes were obtained byformylation of partially propyl-or benzoyl-substituted thiacalix[4]arenes. Prolonged reactiontimes resulted in the hydrolysis of one of the benzoyl groups of dibenzoxythiacalix[4]arene togive a triformylated product. Inspired by this, Complete para-formylation was successfullyachieved by formylation and dealkylation of tetraisopropoxythiacalix[4]arene conformers in one step.In chapter four, a series of calix[4]arene derivatives bearing carboxyl groups directly onthe upper rims were synthesized by the oxidation of formylated calix[4]arenes. If the phenolrings of the calixarenes were substituted by OR groups or formyl groups, affected by theelectronic effects of substituents, the reactivity of the rings would decrease, and only formylgroups would be oxidized. However, if the phenol rings were not substituted on either rim, therings itselves would be oxidized. Influenced by the number and orientations of carboxylgroups, in order to obtain completely oxidized products, in the oxidation process oftetraformylated calixarenes in1,3-alternate conformation, DMSO must be added to increasethe solubility of the products.In chapter five, the effects of substituents on the constructions of calixarene nanotubeswere studied. The nanotubes formed by the stacking of the calixarene cavities cann’t beobtained by using formylated calix[4]arenes due to the absence of strong hydrogen-bondinggroups. The formylated calix[4]arenes, of which the lower rims were substituted by propylgroups, tended to form dimers under interactions of CH-π and π-π stacking. And thenanotubes were constructed under stacking interactions in a triple helix form. When the lowerrim of calixarene was substituted by benzoxy groups, the cavity of the calixarene would beccupied by the inwardly orientated phenol rings and the dimer could not form. In the solidstate, dibenzoxycalix[4]arene diformyl derivative formed a hexamer ring under π-πinteractions. Nanotube was formed by the stacking of the hexamer rings. In the self-assemblyof calix[4]arene derivatives bearing carboxyl groups only on one side, one-dimensional chainarchitectures were constrcted. The1,3-alternate calix[4]arene derivatives bearing carboxylgroups on either side, in different crystallization medium, always form nanotubes by thestacking of the calixarene cavities.