19099-54-8Relevant articles and documents
Generation of Organozinc Reagents by Nickel Diazadiene Complex Catalyzed Zinc Insertion into Aryl Sulfonates
Klein, Philippe,Lechner, Vivien Denise,Schimmel, Tanja,Hintermann, Lukas
supporting information, p. 176 - 180 (2019/12/11)
The generation of arylzinc reagents (ArZnX) by direct insertion of zinc into the C?X bond of ArX electrophiles has typically been restricted to iodides and bromides. The insertions of zinc dust into the C?O bonds of various aryl sulfonates (tosylates, mesylates, triflates, sulfamates), or into the C?X bonds of other moderate electrophiles (X=Cl, SMe) are catalyzed by a simple NiCl2–1,4-diazadiene catalyst system, in which 1,4-diazadiene (DAD) stands for diacetyl diimines, phenanthroline, bipyridine and related ligands. Catalytic zincation in DMF or NMP solution at room temperature now provides arylzinc sulfonates, which undergo typical catalytic cross-coupling or electrophilic substitution reactions.
Mechanism and selectivity in nickel-catalyzed cross-electrophile coupling of aryl halides with alkyl halides
Biswas, Soumik,Weix, Daniel J.
supporting information, p. 16192 - 16197 (2013/11/19)
The direct cross-coupling of two different electrophiles, such as an aryl halide with an alkyl halide, offers many advantages over conventional cross-coupling methods that require a carbon nucleophile. Despite its promise as a versatile synthetic strategy, a limited understanding of the mechanism and origin of cross selectivity has hindered progress in reaction development and design. Herein, we shed light on the mechanism for the nickel-catalyzed cross-electrophile coupling of aryl halides with alkyl halides and demonstrate that the selectivity arises from an unusual catalytic cycle that combines both polar and radical steps to form the new C-C bond.
Revealing a second transmetalation step in the Negishi coupling and its competition with reductive elimination: Improvement in the interpretation of the mechanism of biaryl syntheses
Liu, Qiang,Lan, Yu,Liu, Jing,Li, Gang,Wu, Yun-Dong,Lei, Aiwen
supporting information; experimental part, p. 10201 - 10210 (2009/12/08)
This paper presents an experimental and theoretical investigation of the Pd-catalyzed Negishi coupling reaction and reveals a novel second transmetalation reaction between an Ar1-Pd-Ar2 species and the organozinc reagent Ar2-ZnX. Understanding of this second step reveals how homocoupling and dehalogenation products are formed. Thus, the second transmetalation generates Ar2PdAr2 and Ar 1ZnCl, which upon reductive elimination and hydrolysis, respectively, give the homocoupling product Ar2-Ar2 and the dehalogenation product Ar1H. The ratio of the cross-coupling product Ar1-Ar2 and the homocoupling product Ar 2-Ar2 is determined by competition between the second transmetalation and reductive elimination steps. This mechanism is further supported by density functional theoretical calculations. Calculations on a series of reactions suggest a strategy in controlling the selectivity of cross-coupling and homocoupling pathways, which we have experimentally verified.