title: Deprotonative metalation of functionalized aromatics using mixed lithium-cadmium, lithium-indium, and lithium-zinc species.
abstract: In situ mixtures of CdCl(2)TMEDA (0.5 equiv; TMEDA = N,N,N',N'-tetramethylethylenediamine) or InCl(3) (0.33 equiv) with [Li(tmp)] (tmp = 2,2,6,6-tetramethylpiperidino; 1.5 or 1.3 equiv, respectively) were compared with the previously described mixture of ZnCl(2)TMEDA (0.5 equiv) and [Li(tmp)] (1.5 equiv) for their ability to deprotonate anisole, benzothiazole, and pyrimidine. [(tmp)(3)CdLi] proved to be the best base when used in tetrahydrofuran at room temperature, as demonstrated by subsequent trapping with iodine. The Cd-Li base then proved suitable for the metalation of a large range of aromatics including benzenes bearing reactive functional groups (CONEt(2), CO(2)Me, CN, COPh) or heavy halogens (Br, I), and heterocycles (from the furan, thiophene, pyrrole, oxazole, thiazole, pyridine, and diazine series). Five-membered heterocycles benefiting from doubly activated positions were similarly dideprotonated at room temperature. The aromatic lithium cadmates thus obtained were involved in palladium-catalyzed cross-coupling reactions or simply quenched with acid chlorides.
authors.affiliation: Chimie et Photonique Moléculaires, UMR 6510 CNRS-Université de Rennes 1, Bâtiment 10A, Case 1003, Campus Scientifique de Beaulieu, 35042 Rennes Cedex, France.
authors.forename: Katia
authors.initials: K
authors.lastname: Snégaroff
authors.forename: Jean-Martial
authors.initials: JM
authors.lastname: L'Helgoual'ch
authors.forename: Ghenia
authors.initials: G
authors.lastname: Bentabed-Ababsa
authors.forename: Tan Tai
authors.initials: TT
authors.lastname: Nguyen
authors.forename: Floris
authors.initials: F
authors.lastname: Chevallier
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Yonehara
authors.forename: Masanobu
authors.initials: M
authors.lastname: Uchiyama
authors.forename: Aïcha
authors.initials: A
authors.lastname: Derdour
authors.forename: Florence
authors.initials: F
authors.lastname: Mongin