Cyclotriveratrylene dimers

Cyclotriveratrylene was first prepared by Gertrude Robinson in 1915 (Scheme 7.2). Robinson was interested in following up earlier work on the synthesis of anthracene derivatives and concluded that her product (empirical formula, C7H10O2, was 2,3,6,7-tetramethoxy-9,10-dihydroanthracene (7.43), the dimer of the intermediate veratryl cation (7.42). During the 1950s, CTV was again reformulated erroneously as a hexamer (7.44) and it was not until 1963 that the onset of a variety of modern techniques established a trimeric formula. 

Cyclotriveratrylenes are made by the condensation of veratrole with formaldehyde and were a curiosity when they were first prepared by Robinson in 1915 [47], At the time she believed the compound to be a dimer, 2,3,6,7-tetramethoxy-9,10-dihydroxyanthracene. The reason for this was that the composition of the original compound was determined by elemental analysis. This technique determines the percentage of hydrogen and carbon in the sample which would be identical for a dimer, trimer or any other cyclic product with the same proportion of carbon to... 

For the construction of the cryptophanes depicted in Fig. 3, two different synthetic routes have been employed (Fig. 4). With reference to method (a), a suitably substituted benzyl alcohol is first converted to a C3-cyclotriveratrylene, to which three chains ending with benzyl alcoholic groups are attached and eventually cyclized intramolecularly in this reaction, the first cap serves as a template to direct the trimerization [14]. In a second, shorter route (b), a benzyl alcohol is first transformed into a dimer , which under suitable conditions trimerizes to a cryptophane in this reaction, six carbon-carbon bonds have to be created in a single sequence [24]. 

For the first time we report the synthesis of macrocycles like calixpyrrole, cyclotriveratrylene (CTV), cyclotetraveratrylene (CTTV), porphyrine ete over molecular sieve as a catalyst. Calixpyrroles are synthesized from pyrrole and a ketone like acetone over MCM-41 under reflux conditions using suitable solvent. In case of MCM-41 cyclic calixpyrroles were obtained. On the other hand due to shape selectivity in case of Y zeolite linear di-, tri- and tetra- polypyrroles were obtained and cyclic tetramers were not observed. The mechanism of the synthesis of calixpyrrole is either by the dimerization of dimer with simultaneous cyclization to cyclic tetramer or cyclization of linear tetramer via recoil phenomenon. 

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