title: Bulky alkylphosphines with neopentyl substituents as ligands in the amination of aryl bromides and chlorides.
abstract: Di(tert-butyl)neopentylphosphine (DTBNpP) in combination with palladium sources provided catalysts with comparable or better activity for the Hartwig-Buchwald amination of aryl bromides than tri(tert-butyl)phosphine (TTBP) under mild conditions. DTBNpP also provided effective catalysts for amination reactions of aryl chlorides at elevated temperatures. Further replacement of tert-butyl groups with neopentyl substituents resulted in less effective ligands for amination reactions. Computationally derived cone angles showed that replacement of a tert-butyl group with a neopentyl group significantly increased the cone angle of the phosphine. The larger cone angle of DTBNpP than TTBP appears to correlate with the higher activity of catalysts derived from DTBNpP in the amination of aryl bromides. TTBP is a stronger electron donor than DTBNpP, which may explain the higher activity for TTBP-derived catalysts toward aryl chlorides.
authors.affiliation: Department of Chemistry, University of Alabama, Box 870336, Tuscaloosa, AL 35487-0336, USA.
authors.forename: Lensey L
authors.initials: LL
authors.lastname: Hill
authors.forename: Lucas R
authors.initials: LR
authors.lastname: Moore
authors.forename: Rongcai
authors.initials: R
authors.lastname: Huang
authors.forename: Raluca
authors.initials: R
authors.lastname: Craciun
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Vincent
authors.forename: David A
authors.initials: DA
authors.lastname: Dixon
authors.forename: Joe
authors.initials: J
authors.lastname: Chou
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Woltermann
authors.forename: Kevin H
authors.initials: KH
authors.lastname: Shaughnessy
mesh_terms: D000586:Amination; D006842:Hydrocarbons, Brominated / Q000138:chemical synthesis* / Q000737:chemistry; D006843:Hydrocarbons, Chlorinated / Q000138:chemical synthesis* / Q000737:chemistry; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D010720:Phosphines / Q000737:chemistry*; D013237:Stereoisomerism; D013997:Time Factors
chemical_list: D006842:Hydrocarbons, Brominated; D006843:Hydrocarbons, Chlorinated; D008024:Ligands; D009942:Organometallic Compounds; D010720:Phosphines; D010165:Palladium