.sigma.-Sulfurane chemistry. Effect of substituents on the coupling reactions

Ferrocene Bis(phosphonite)s: Synthesis and Characterization of a Novel Class of Sterically Congested Ligands1

“…The ferrocenylbis(phosphonite) 6 was evaluated as a ligand for C-C bond formation (Suzuki reaction) following the experimental protocol of Buchwald. 24,25 3-Trifluoromethyl-1,1′-biphenyl 26 was formed in 90% isolated yield by reaction of 3-(trifluoromethyl)phenylboronic acid with bromobenzene using the catalyst formed in situ from 6 and palladium(II) acetate (eq 3).…”

Sulfur(IV)‐Mediated Unsymmetrical Heterocycle Cross‐Couplings

“…[11] CÀC ligand coupling was believed to be a major decomposition pathway. Extensive mechanistic studies by Trost [12] and Oae [13] established that the trigonal bipyramidal geometries of sulfuranes allowed ligands to be placed at a dihedral angle of approximately 908, thereby facilitating ligand coupling through reductive elimination. [14] A series of studies emanating from the Furukawa and Oae group [15,16] demonstrated that addition of organometallic nucleophiles to sulfoxides led to the formation of ligand coupling products via oxy-sulfurane intermediates (see Sup-porting Information for historical summary of sulfur mediated couplings).…”

Synthesis of Bis-heteroaryls Using Grignard Reagents and Pyridylsulfonium Salts

“…Ligand coupling at −78 °C gave bis-heteroaryl 25 in 40% yield, whereas poorer results were obtained at both rt (not isolated) and 45 °C (35%). The formation of 6,6′-bis­(trifluoromethyl)-2,2′-bipyridine was noted, which is the first time we have observed evidence for ligand exchange with our sulfurane chemistry. At 45 °C, the pyridine–toluene product of a competing coupling reaction was observed also.…”