Regio- and stereoselective addition of allylmetal reagents to pyridinium-pi and quinolinium-pi complexes.

[reaction: see text] Regio- and stereoselective allylation of pyridinium and quinolinium salts was performed by the addition of allylindium and allyltributyltin reagents toward intermediary cation-pi complexes. The reaction with allylindium and allyltributyltin reagents afforded a 1,2-adduct, whereas the addition of a prenylindium reagent gave a 1,4-adduct with good regio- and stereoselectivities. X-ray structural analysis, 1H NMR studies, and DFT calculations elucidated the intermediary cation-pi complex formation with face-to-face orientation.