title: N-Heterocyclic Carbene Catalyzed [4 + 2] Annulation Reactions with in Situ Generated Heterocyclic ortho-Quinodimethanes.
abstract: An efficient strategy for the in situ generation of heterocyclic ortho-quinodimethanes (oQDMs) from 2-methyl-heteroarene-3-carboxylic esters by N-heterocyclic carbene (NHC) catalysis is disclosed. These heterocyclic oQDMs undergo highly enantioselective [4 + 2] annulation reactions with isatin-derived ketimines to afford optically pure heteroarene-fused δ-lactams bearing a quaternary stereogenic center. The main features of this reaction include challenging direct C(sp(3))-H bond functionalizations, excellent enantioselectivities, readily available starting materials, mild reaction conditions, high efficiency, and operational simplicity.
authors.affiliation: Department of Chemistry, Zhejiang Sci-Tech University , Hangzhou 310018, PR China.
authors.forename: Jianfeng
authors.initials: J
authors.lastname: Xu
authors.affiliation: Department of Chemistry, Zhejiang Sci-Tech University , Hangzhou 310018, PR China.
authors.forename: Shiru
authors.initials: S
authors.lastname: Yuan
authors.affiliation: Department of Chemistry, Zhejiang Sci-Tech University , Hangzhou 310018, PR China.
authors.forename: Maozhong
authors.initials: M
authors.lastname: Miao