title: Medium-Ring Nitrogen Heterocycles through Migratory Ring Expansion of Metalated Ureas.
abstract: Simple benzo-fused nitrogen heterocycles (indolines, tetrahydroquinolines, and their homologues) undergo migratory ring expansion through deprotonation of their benzylic urea derivatives with lithium diisopropylamide (LDA) in the presence of N,N'-dimethylpropylideneurea (DMPU). The products of the reactions are benzodiazepines, benzodiazocines, and their homologues, with ring sizes of 8-12. The reactions tolerate a range of substituent patterns and types, and may exhibit enantiospecificity or diastereoselectivity. Considerable complexity is rapidly generated in an efficient synthesis of these otherwise difficult-to-obtain medium-ring nitrogen heterocycles.
authors.affiliation: School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
authors.forename: Jessica E
authors.initials: JE
authors.lastname: Hall
authors.affiliation: School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
authors.forename: Johnathan V
authors.initials: JV
authors.lastname: Matlock
authors.affiliation: School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
authors.forename: John W
authors.initials: JW
authors.lastname: Ward
authors.affiliation: School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
authors.forename: Katharine V
authors.initials: KV
authors.lastname: Gray
authors.affiliation: School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK. j.clayden@bristol.ac.uk.
authors.forename: Jonathan
authors.identifier: 0000-0001-5080-9535
authors.initials: J
authors.lastname: Clayden
keywords: heterocycles; indolines; organolithium; ring expansion; tetrahydroquinolines