Asymmetric Mizoroki-Heck reactions: generation of quaternary stereocenters and cascade cyclizations

Mizoroki-Heck reaction constitutes an effective method for the formation of quaternary stereocenters. This reaction has been applied to functionalized 2-alkenylpyrroles as substrates in which the b-elimination is blocked by a methyl substituent. 10,10-Disubstituted pyrrolo[1,2-b]isoquinolines can be obtained using different palladium catalysts and chiral bidentate phosphanes as ligands, although with low enantioselectivities. In some cases, competition between Mizoroki-Heck reaction and C-H direct arylation reaction on the pyrrole nucleus has also been observed for this type of polyfunctionalized substrates. Finally, we have shown that quaternary stereocenters can be generated using chiral phosphane ligands as (R)-BINAP, through a cascade polyene cyclization. This procedure has been successfully applied to the construction of tetracyclic framework of Lycorine class of Amaryllidaceae alkaloids