title: Development of Chiral Bis-hydrazone Ligands for the Enantioselective Cross-Coupling Reactions of Aryldimethylsilanolates.
abstract: A palladium-catalyzed, enantioselective, aryl-aryl cross-coupling reaction using 1-naphthyldimethylsilanolates and chiral bis-hydrazone ligands has been developed. A family of glyoxal bis-hydrazone ligands containing various 2,5-diarylpyrrolidine groups was prepared to evaluate the influence of ligand structure on the rate and enantioselectivity of the cross-coupling. New synthetic routes to the 1-amino-2,5-diarylpyrrolidines were developed to enable the structure/reactivity-selectivity studies. Role reversal experiments of aryldimethylsilanolates and aryl bromides result in biaryl products with the same configuration and similar enantioselectivities implying that reductive elimination is the stereodetermining step. The origin of stereoselectivity is rationalized through computational modeling of diarylpalldium(II) complex which occurs through a conrotatory motion for the two aryl groups undergoing C-C bond formation.
authors.affiliation: †Roger Adams Laboratory, Department of Chemistry, University of Illinois, Urbana, Illinois 61801, United States.
authors.forename: Scott E
authors.initials: SE
authors.lastname: Denmark
authors.affiliation: †Roger Adams Laboratory, Department of Chemistry, University of Illinois, Urbana, Illinois 61801, United States.
authors.forename: Wen-Tau T
authors.initials: WT
authors.lastname: Chang
authors.affiliation: ‡Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States.
authors.forename: K N
authors.initials: KN
authors.lastname: Houk
authors.affiliation: ‡Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States.
authors.forename: Peng
authors.initials: P
authors.lastname: Liu
mesh_terms: D002384:Catalysis; D006835:Hydrazones / Q000138:chemical synthesis* / Q000737:chemistry; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry; D010165:Palladium / Q000737:chemistry; D012821:Silanes / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D006835:Hydrazones; D008024:Ligands; D009942:Organometallic Compounds; D012821:Silanes; D010165:Palladium