Porosity and acidity of molecular sieve Al-MCM-41 (ca. 30 A pore diameter) plays a crucial role in the synthesis of novel calix(4)pyrroles; for the first time, Al-MCM-41 has been used as a solid acid catalyst to produce a number of calix(4)pyrroles with good selectivity ad yields where zeolite HY (ca. 7.6 A pore diameter) yields mainly the linear chain dimer and no cyclic products.
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