Suzuki−Miyaura, α-Ketone Arylation and Dehalogenation Reactions Catalyzed by a Versatile N-Heterocyclic Carbene−Palladacycle Complex

Abstract

[reaction: see text] The activity of the complex (IPr)PdCl(eta2-N,C-C12H7NMe2), 1 [IPr = (N,N'-bis(2,6-diisopropylphenyl)imidazol)-2-ylidene], in the Suzuki-Miyaura cross-coupling reaction involving unactivated aryl chlorides and triflates with arylboronic acids at room temperature in technical grade 2-propanol is described. These conditions allow for the synthesis of di- and tri-ortho-substituted biaryls in very short reaction times. This complex also displays very high activity for alpha-ketone arylation and dehalogenation reactions of activated and unactivated aryl chlorides.

Aus der Sicht des Synthetikers: Palladiumkomplexe N‐heterocyclischer Carbene als Katalysatoren für Kreuzkupplungen

“…[123] Der Austausch von Chlorid gegen Isopropoxid (aus iPrOH und KOtBu) mit anschließender b-Hydrideliminierung überführt [(IPr)Pd(OAc) 2 ] (79) und den IPr-Palladacyclus 140 in ein Palladiumhydrid, das dann eine reduktive Eliminierung zu [(IPr)Pd 0 ] eingeht. [112,141] Für 140 ist bei Suzuki-Miyaura-Reaktionen auch ein alternativer Aktivierungsmechanismus möglich, der für Palladacyclus-Phosphan-Addukte beschrieben wurde. [118] ist die Bindungsenergie zwischen Pyridinligand und Pd 0 geringer als zwischen Pyridinligand und Pd II .…”

“…Unter den Kreuzkupplungen ist die Arylierung von Enolaten [206] [120,130,141,207,208] Die p-Allyl-PalladiumchloridKomplexe von IPr (166), SIPr (147), IMes (145), IAd (149) und ItBu (148, Schema 44) erbrachten bei der Arylierung von Propiophenon mit Chlorbenzol bei 79 8C zwar sämtlich über 90 % Umsatz, dennoch gelten weiterhin die Komplexe mit IPr-oder SIPr-Liganden als die besten Präkatalysatoren. [208] Das Aren konnte für diese Reaktion viele funktionelle Gruppen tragen (jedoch keine Nitril-und Aldehydgruppen), [207] 3 ] erzeugt.…”

Preparation of Pd-Diimine@SBA-15 and Its Catalytic Performance for the Suzuki Coupling Reaction

“…When the amount of catalyst was increased to 60 mg (1 mol % Pd), aryl chlorides became applicable substrates (Table 3, entries 11 and 12); for instance, 20% yield was obtained for the coupling of activated (electron-deficient) 4-nitrochlorobenzene and phenylboronic acid (Table 3, entry 12). Based on the research results above, the possible mechanism of the Suzuki coupling reaction of aryl halide and phenylboronic acid over Pd-diimine@SBA-15 can be described as Scheme 2 [32,40]. In Scheme 2, there are three main stages in the mechanism of the Suzuki cross-coupling reaction over Pd-diimine@SBA-15: the oxidative addition of substrate, transmetalation, and reductive elimination to produce the final product, in which the catalytic cycle of Pd(0)/Pd(II) occurred.…”

“…Suzuki coupling reactions of various aryl halides (X) and phenylboronic acid over Pddiimine@SBA-15catalyst (a). Based on the research results above, the possible mechanism of the Suzuki coupling reaction of aryl halide and phenylboronic acid over Pd-diimine@SBA-15 can be described as Scheme 2 [32,40]. In Scheme 2, there are three main stages in the mechanism of the Suzuki cross-coupling reaction over Pd-diimine@SBA-15:…”

“…Based on the research results above, the possible mechanism of the Suzuki coupling reaction of aryl halide and phenylboronic acid over Pd-diimine@SBA-15 can be described as Scheme 2 [32,40]. In Based on the research results above, the possible mechanism of the Suzuki coupling reaction of aryl halide and phenylboronic acid over Pd-diimine@SBA-15 can be described as Scheme 2 [32,40]. In Scheme 2, there are three main stages in the mechanism of the Suzuki cross-coupling reaction over Pd-diimine@SBA-15: the oxidative addition of substrate, transmetalation, and reductive elimination to produce the final product, in which the catalytic cycle of Pd(0)/Pd(II) occurred.…”