PALLADIUM-INDUCED INTRAMOLECULAR PYRIDINE-ALLYL COUPLING REACTIONS - FORMATION OF N-BRIDGEHEAD HETEROCYCLES WITH A STABLE C-N BOND

In the presence of stoichiometric amounts of bis(acetonitrile) dichlor opalladium(II) the ortho-alkenylpyridines 2-but-3'-en-1'-ylpyridine (1 ), 2-pent-5'-en-1'-ylpyridine (2), 2-hex-5'-en-1'-ylpyridine (3), 2-he pt-6'-en-1'-ylpyridine (4) and 2-methyl-6-pent-4'-en-1'-ylpyridine (5) led to a mixture of coordination compounds such as 2-alken-1'-ylpyrid ine-kappa N:kappa(2)C-dichloropalladium(II) and bis(2-alken-1'-ylpyrid ine-kappa N)-dichloropalladium(II) together with 2-pent-4-ene-1',3'diy lpyridine-kappa N:kappa(3)C-chloropalladium(II) and 2-hex-4-en-1',3'-d iylpyridine-kappa N:kappa 3C-chloropalladium(II) in the case of 2 and 3 respectively. The latter were quantitatively demetallated in the pre sence of an excess of triphenylphosphane to yield tris(triphenylphosph ane)palladium(0), 2-vinyl-2,3-dihydroindolizinium chloride and 2-prop- 1'-en-1-'yl-2,3-dihydroindolizinium chloride, respectively, by a regio selective addition of the pyridine unit onto the more congested termin al carbon atom of the allyl fragment.