Pyrrolidine and Piperidine Formation via Copper(II) Carboxylate-Promoted Intramolecular Carboamination of Unactivated Olefins: Diastereoselectivity and Mechanism

An expanded substrate scope and in-depth analysis of the reaction mechanism of the copper(II) carboxylate-promoted intramolecular carboamination of unactivated alkenes is described. This method provides access
to N-functionalized pyrrolidines and piperidines. Both aromatic and aliphatic γ- and δ-alkenyl
N-arylsulfonamides undergo the oxidative cyclization reaction efficiently. N-Benzoyl-2-allylaniline also
underwent the oxidative cyclization. The terminal olefin substrates examined were more reactive than
those with internal olefins, and the latter terminated in elimination rather than carbon−carbon bond
formation. The efficiency of the reaction was enhanced by the use of more organic soluble copper(II)
carboxylate salts, copper(II) neodecanoate in particular. The reaction times were reduced by the use of
microwave heating. High levels of diastereoselectivity were observed in the synthesis of 2,5-disubstituted
pyrrolidines, wherein the cis substitution pattern predominates. The mechanism of the reaction is discussed
in the context of the observed reactivity and in comparison to analogous reactions promoted by other
reagents and conditions. Our evidence supports a mechanism wherein the N−C bond is formed via
intramolecular syn aminocupration and the C−C bond is formed via intramolecular addition of a primary
carbon radical to an aromatic ring.