Manganese(III) acetate mediated radical reactions leading to araliopsine and related quinoline alkaloids

Tricyclic quinoline alkaloids, including araliopsine 2, can be prepared in 'one-pot' by reaction of 4-hydroxy-1-methyl-2(1H)quinoline 5 or 2,4-quinoli nediol 31 with manganese(III) acetate in the presence of a variety of elect ron-rich alkenes. The reaction mechanism involves an initial intermolecular radical addition reaction followed by radical oxidation and cyclisation st eps. Both angular and linear tricyclic alkaloids can be formed and the regi oselectivity of the cyclisation is shown to depend on whether alkyl or aryl groups are attached to the alkene. (C) 2001 Elsevier Science Ltd. All righ ts reserved.