title: N-heterocyclic carbene-catalyzed enantioselective annulation of indolin-3-ones with bromoenals.
abstract: N-Heterocyclic carbene-catalyzed reactions of indolin-3-ones with 2-bromoenals opened an asymmetric access to 3,4-dihydropyrano[3,2-b]indol-2(5 H)-ones in good yields and with good to excellent enantioselectivities. This protocol tolerates a broad substrate scope. In addition, a possible mechanism for the annulation reaction is presented.
authors.affiliation: Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen (Germany), Fax: (+49) 0241-80-92127.
authors.forename: Qijian
authors.initials: Q
authors.lastname: Ni
authors.forename: Xiaoxiao
authors.initials: X
authors.lastname: Song
authors.forename: Gerhard
authors.initials: G
authors.lastname: Raabe
authors.forename: Dieter
authors.initials: D
authors.lastname: Enders
keywords: N-heterocyclic carbenes; annulation; asymmetric synthesis; dihydropyranoindol-2-ones; organocatalysis