Diastereoselective Cyclization of 1,5-Dienes with the C−H Bond of Pyridine Catalyzed by a Cationic Mono(phosphinoamide) Alkyl Scandium Complex

Carbocyclization of unconjugated dienes mediated by organometallics is an important reaction for synthesis of a variety of carbocyclic derivatives, but a direct annulation of dienes with an inert CH bond of substrate has remained unexplored up to date. We here reported a series of novel rare-earth dialkyl complexes bearing a phosphinoamide anion for the first time and demonstrated that the combination of a mono(phosphinoamido)-ligated scandium dialkyl complex with B(C6F5)3 could serve as an excellent catalyst for the cis-selective cyclization of 1,5-dienes together with ortho-C(sp2)H addition of pyridines, which afforded a new family of pyridyl-functionalized 1,3-disubstituted cyclopentane derivatives containing monocyclic, bicyclic, spirocyclic, or heterocyclic skeletons in moderate to excellent yields with high diastereoselectivity (cis : trans up to 99 : 1).