Co(salen)/SBA-15 catalysed oxidation of a β-O-4 phenolic dimer under microwave irradiation

The microwave-assisted oxidative degradation of a lignin model phenolic dimer [1-(4-hydroxy-3-methoxyphenoxy)-2-(2-methoxyphenoxy)-propane-1,3-diol, 1] catalysed by Co(salen)/SBA-15 is reported. The investigated model compound 1 was prepared through a multistep synthesis and characterized by H-1,C-13 NMR, and GC-MS studies. The catalyst was prepared by immobilizing [N.N'-bis(salicylidene)ethane-1,2-diaminato]Cobalt(11), Co(salen) complex onto the periodic mesopore channels of siliceous SBA-15. The activity of the Co(salen)/SBA-15 was investigated in the oxidation of 1 in the presence of hydrogen peroxide as oxidant, both under microwave irradiation and conventional heating. The phenolic dimer was selectively oxidized to 2-methoxy phenol with very high TON under microwave activation conditions. Comparatively, reactions run under conventional heating led to oligomerisation of the dimer and resulted in a mixture of products. (C) 2011 Elsevier B.V. All rights reserved.