Enantioselective synthesis of pyrrolidine-, piperidine-, and azepane-type N-heterocycles with α-alkenyl substitution: the CpRu-catalyzed dehydrative intramolecular N-allylation approach.

A cationic CpRu complex of chiral picolinic acid derivatives [(R)- or (S)-Cl-Naph-PyCOOCH(2)CH═CH(2)] catalyzes asymmetric intramolecular dehydrative N-allylation of N-substituted ω-amino- and -aminocarbonyl allylic alcohols with a substrate/catalyst ratio of up to 2000 to give α-alkenyl pyrrolidine-, piperidine-, and azepane-type N-heterocycles with an enantiomer ratio of up to >99:1. The wide range of applicable N-substitutions, including Boc, Cbz, Ac, Bz, acryloyl, crotonoyl, formyl, and Ts, significantly facilitates further manipulation toward natural product synthesis.