title: Homoleptic zincate-promoted room-temperature halogen-metal exchange of bromopyridines.
abstract: Homoleptic lithium tri- and tetraalkyl zincates were reacted with a set of bromopyridines. Efficient and chemoselective bromine-metal exchanges were realized at room temperature with a substoichiometric amount of nBu(4)ZnLi(2)·TMEDA reagent (1/3 equiv; TMEDA=N,N,N',N'-tetramethylethylenediamine). This reactivity contrasted with that of tBu(4)ZnLi(2)·TMEDA, which was inefficient below one equivalent. DFT calculations allowed us to rationalize the formation of N···Li stabilized polypyridyl zincates in the reaction. The one-pot difunctionalization of dibromopyridines was also realized using the reagent stoichiometrically. The direct creation of C-Zn bonds in bromopyridines enabled us to perform efficient Negishi-type cross-couplings.
authors.affiliation: SOR, SRSMC, Nancy Université, CNRS, Boulevard des Aiguillettes, 54506 Vandoeuvre-Lès-Nancy, France.
authors.forename: Nguyet Trang Thanh
authors.initials: NT
authors.lastname: Chau
authors.forename: Maxime
authors.initials: M
authors.lastname: Meyer
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Komagawa
authors.forename: Floris
authors.initials: F
authors.lastname: Chevallier
authors.forename: Yves
authors.initials: Y
authors.lastname: Fort
authors.forename: Masanobu
authors.initials: M
authors.lastname: Uchiyama
authors.forename: Florence
authors.initials: F
authors.lastname: Mongin
authors.forename: Philippe C
authors.initials: PC
authors.lastname: Gros
mesh_terms: D020650:Combinatorial Chemistry Techniques; D006842:Hydrocarbons, Brominated / Q000737:chemistry*; D008094:Lithium / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D013696:Temperature; D015032:Zinc / Q000737:chemistry*
chemical_list: D006842:Hydrocarbons, Brominated; D009942:Organometallic Compounds; D011725:Pyridines; D008094:Lithium; D015032:Zinc