Highly Enantioselective Nickel-Catalyzed Intramolecular Hydroalkenylation of N- and O‑Tethered 1,6-Dienes To Form Six-Membered Heterocycles

A highly
enantioselective nickel-catalyzed intramolecular hydroalkenylation
of N- or O-tethered 1,6-dienes was developed by using monodentate
chiral spiro phosphoramidite ligands. The reaction provides an efficient
and straightforward method for preparing very useful six-membered
N- and O-heterocycles with high regioselectivity as well as excellent
stereoselectivity from easily accessible starting materials under
mild reaction conditions. The chiral spiro nickel catalyst developed
in this study represents one of the few catalysts for highly enantioselective
cyclization of unconjugated dienes.