Oxygenation of 4-tert-butylcatechol catalysed by a manganese(II) complex: implications for extradiol catechol dioxygenases |
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Authors: | Shaikh Nizamuddin Panja Anangamohan Banerjee Pradyot Ali Mahammad |
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Institution: | (1) Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Kolkata, 700 032, India;(2) Department of Chemistry, Jadavpur University, Kolkata, 700 032, India |
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Abstract: | An N donor tetradentate manganese complex, MnII(bispicen)Cl2] (A) bispicen = N,N -bis(2-pyridylmethyl)-1,2-ethanediamine)] catalyses the oxidative cleavage of 4-tert-butylcatechol (1) in the presence of O2. The oxygenated products were isolated by t.l.c. and column chromatography and characterised by 1H-, 13C-n.m.r., DEPT, i.r. and u.v.–vis. spectroscopy. The oxygenated products as well as other spectral evidence suggest that the oxygenation occurs via a 4-tert-butylsemiquinone bound complex, MnII(bispicen)(4-sq)]+ (4-sq = 4-tert-butylsemiquinone). 1H-n.m.r. spectroscopy suggests that the oxygenation follows multiple pathways. Isolation of the products suggests that the oxygenations proceed in an extradiol fashion and a probable mechanism is suggested. Some intradiol cleaved products have also been detected. E.s.r. spectroscopy suggests that manganese(II) is ultimately converted into the manganese(IV) species. |
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