resumo
Catalytic efficiency of tetrabutylammonium salts of sandwich tungstophosphates B-alpha-[M-4(H2O)(2)(PW9O34)(2)](n-), M = Co-II, Mn-II, Fe-III was studied in the oxidation of (R)-(+)-limonene, geraniol, linalool, linalyl acetate, carveol, and cis-cyclooctene with hydrogen peroxide, in acetonitrile. Oxidation of (R)-(+)-limonene gave limonene-1,2-diol as main product. Epoxidation of linalool takes place preferentially at the more substituted 6,7-double bond, the corresponding 6,7-epoxide reacting further, yielding furano- and pyrano-oxides, via intramolecular cyclization. Oxidation of linalyl acetate occurred preferentially at the more substituted 6,7-double bond for Mn-4(PW9)(2), affording 6,7-epoxide at 82% selectivity. Linalyl acetate 1,2-epoxide was the major product with 51% and 77% selectivity for Co-4(PW9)(2) and Fe-4(PW9)(2), respectively. Oxidation of carveol occurred with very good conversions in the presence of Mn-4(PW9)(2), Co-4(PW9)(2) and Fe-4(PW9)(2), yielding carvone and carveol 1,2-epoxide in similar amounts. Oxidation of cis-cyclooctene gave only the epoxide, while oxidation of geraniol at room temperature afforded 2,3-epoxygeraniol as the major product. (C) 2016 Elsevier B.V. All rights reserved.
palavras-chave
METAL-SUBSTITUTED POLYOXOTUNGSTATES; KEGGIN-TYPE POLYOXOTUNGSTATES; HIGH-VALENT MANGANESE; SELECTIVE OXIDATION; LIMONENE EPOXIDATION; COMPLEX HETEROPOLYTUNGSTATES; HETEROGENEOUS PERFORMANCE; CRYSTAL-STRUCTURE; ACTIVE CATALYSTS; ALKENE OXIDATION
categoria
Chemistry
autores
Santos, ICMS; Gamelas, JAF; Duarte, TAG; Simoes, MMQ; Neves, MGPMS; Cavaleiro, JAS; Cavaleiro, AMV
nossos autores
Ana Maria Vieira Silva Viana Cavaleiro
Professor Catedrático
Isabel Cristina Maia da Silva Santos Vieira
Investigador Júnior
José António Ferreira Gamelas
Bolseiro de pós-Doutoramentoagradecimentos
Thanks are due to FCT/MEC for the financial support to QOPNA (FCT UID/QUI/00062/2013) and CICECO (FCT UID/CTM/50011/2013), through national founds and where applicable co-financed by the FEDER, within the PT2020 Partnership Agreement.