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

The carbocyclization of non‐conjugated dienes mediated by organometallics is an important reaction for the synthesis of a variety of carbocyclic derivatives, but the direct annulation of dienes with an inert C−H bond of a substrate has remained unexplored to date. We herein report a series of novel rare‐earth dialkyl complexes bearing a phosphinoamide anion and demonstrate that the combination of a mono(phosphinoamido)‐ligated scandium dialkyl complex with B(C 6 F 5 ) 3 results in an excellent catalyst for the cis ‐selective cyclization of 1,5‐dienes with the ortho ‐C(sp 2 )−H bond of pyridines to afford a new family of pyridyl‐functionalized 1,3‐disubstituted cyclopentane derivatives containing monocyclic, bicyclic, spirocyclic, and heterocyclic skeletons in moderate to excellent yields with high diastereoselectivities ( cis / trans up to 99:1).