Nagabandi Srinivas

28-O-04-Synthesis of macrocycles using molecular sieve catalysts

Publisher Summary This chapter describes the synthesis of macrocycles (calixpyrrole, cyclotriveratrylene (CTV), cyclotetraveratrylene (CTTV), and porphyrine) using molecular sieve catalysts. 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 are obtained. On the other hand, because of the shape selectivity in case of Y zeolite linear di-, tri-, and tetra-polypyrroles are obtained, and cyclic tetramers are not observed. The mechanism of the synthesis of calixpyrrole is either by the dimerization of dimer with simultaneous cyclization to cyclic tetramer or by the cyclization of linear tetramer through recoil phenomenon.