title: γ-Selective cross-coupling of allylic silanolate salts with aromatic bromides using trialkylphosphonium tetrafluoroborate salts prepared directly from phosphine•borane adducts.
abstract: The γ-selective, palladium-catalyzed cross-coupling of sodium (Z)-2-butenyldiethylsilanolate with a variety of aromatic bromides is reported. The protocol provides high yields (73-94%) and site selectivity (γ/α, 25:1 → > 99:1) in the coupling of electron-rich, electron-poor, sterically hindered, and heteroaromatic bromides. The use of a configurationally homogeneous (Z)-silanolate, nontransferable ethyl groups, and a sterically bulky trialkylphosphonium tetrafluoroborate salt (t-BuCy(2)PH(+)BF(4)(-)) prepared directly from the corresponding air-stable phosphine•borane adduct are critical to the success of the method.
authors.affiliation: Roger Adams Laboratory, Department of Chemistry, University of Illinois, 600 South Mathews Avenue, Urbana, Illinois 61801, USA. sdenmark@illinois.edu
authors.forename: Scott E
authors.initials: SE
authors.lastname: Denmark
authors.forename: Nathan S
authors.initials: NS
authors.lastname: Werner
mesh_terms: D001880:Boranes / Q000737:chemistry*; D001881:Borates; D001888:Boric Acids / Q000737:chemistry*; D006842:Hydrocarbons, Brominated / Q000737:chemistry*; D015394:Molecular Structure; D009943:Organophosphorus Compounds / Q000737:chemistry*; D010720:Phosphines / Q000737:chemistry*; D012492:Salts / Q000737:chemistry; D012821:Silanes / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D001880:Boranes; D001881:Borates; D001888:Boric Acids; D006842:Hydrocarbons, Brominated; D009943:Organophosphorus Compounds; D010720:Phosphines; D012492:Salts; D012821:Silanes; C044646:phosphine; C098759:fluoroboric acid