title: Tandem 1,4-addition reactions with benzene and alkylated benzenes promoted by pentaammineosmium(II).
abstract: Electrophiles such as dimethoxymethane and 3-penten-2-one react with the complex [Os(NH(3))(5)(eta(2)-benzene)](2+) in the presence of triflic acid to form metastable benzenium intermediates. These benzenium intermediates further react with carbon nucleophiles including silyl ketene acetals, (silyloxy)alkenes, and phenyllithium in an overall tandem 1,4-addition sequence. The metal fragment controls the relative stereo- and regiochemistry for both electrophilic and nucleophilic addition steps. Upon oxidative demetalation with silver triflate, cis-1,4 cyclohexadienes are formed in yields ranging from 16 to 82%. This methodology can also be used to dearomatize toluene and ortho- and meta-xylene with unexpectedly high regio- and stereocontrol.
authors.affiliation: Department of Chemistry, University of Virginia, Charlottesville, Virginia 22901, USA.
authors.forename: Fei
authors.initials: F
authors.lastname: Ding
authors.forename: Michael E
authors.initials: ME
authors.lastname: Kopach
authors.forename: Michal
authors.initials: M
authors.lastname: Sabat
authors.forename: W Dean
authors.initials: WD
authors.lastname: Harman
mesh_terms: D001554:Benzene / Q000737:chemistry*; D001555:Benzene Derivatives / Q000737:chemistry*; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry*; D009992:Osmium / Q000737:chemistry*
chemical_list: D001555:Benzene Derivatives; D009942:Organometallic Compounds; C470328:pentaammineosmium(II); D009992:Osmium; D001554:Benzene