Transition metal-diene complexes in organic synthesis. I. Highly selective oxidations of cyclohexadieneiron tricarbonyl complexes: synthesis of 4b,8a-dihydro-3-carbazolones and the first total synthesis of carbazomycin A.
The cyclohexadiene iron complex I (R = H) prepd. from tricarbonyl(h5-cyclohexadienylium)iron tetrafluoroborate and 2,3,4-Me2(MeO)C6H2NH2, underwent oxidative cyclization with highly active MnO2 to give 4-deoxycarbazomycin B (II R = H). The structure of the carbazole complex III, obtained from I (R = H) and FeCl3, was detd. by x-ray anal. A total synthesis of carbazomycin (II, R = MeO) was achieved starting from 2,3-Me2C6H3OH via complex I (R = MeO).
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