Estudo de reaccoes catalisadas por zeolitos

Zeolitic catalysts have been used instead of Lewis acids as catalysts in Friedel-Crafts reactions of resin acids (dealkylations and acylations) and in the protection of aldehydes by acetylation. Dealkylation reaction of methyl dehydroabietate 5a was been carried out using several zeolites (Y, Beta, ZSM-5 and Mordenite) instead of the commonly used catalyst aluminium trichloride. In the acylation reaction of methyl cis-deisopropyledehydroabietate 11 and methyl trans-deisopropyldehydroabietate 10 several acylating systems (acylating agent plus solvent) have been tested with zeolites Y and Beta. High yields were obtained in the dealkylation case of 5a in the selective synthesis of methyl trans-deisopropyldehydroabietate isomer 10 upon the use of zeolites Y and Beta instead of classic catalysts. On the contrary, no acylated products were obtained in the acylation reaction of 10 and 11. Interpretation of results has been achieved considering the structures of compounds 10 and 11 analysed by software for molecular modelisation. Aldehyde protection by acetylation has been carried using zeolites Y, Beta, ZSM-5 and Mordenite. Zeolites Y and Beta show the greatest initial activities. Acetylation of aromatic and aliphatic aldehydes using zeolite Y has been studied. The observed selectivity on the 1,1-diacetate of each aldehyde is high (ca. 100%) with some decrease in the case of aliphatic aldedhydes (ca. 85%)Available from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1200 Lisboa / FCT - Fundação para o Ciência e a TecnologiaSIGLEPTPortuga