Well-Defined, Air-Stable (NHC)Pd(Allyl)Cl (NHC = N-Heterocyclic Carbene) Catalysts for the Arylation of Ketones

Abstract

A number of palladium-N-heterocyclic carbene (NHC) complexes were found to be active catalysts for the arylation of ketones. A large number of substrates, both aryl halides and ketones, are compatible with the reaction conditions. The ketone arylation reactions are achieved with low catalyst loading in short reaction times using aryl chlorides and triflates as reactive partners. [reaction: see text]

Palladium Complexes of N‐Heterocyclic Carbenes as Catalysts for Cross‐Coupling Reactions—A Synthetic Chemist's Perspective

“…An array of functionalized alkanes (200)(201)(202)(203)(204), including the chiral terpene-derived ketone 204, as well as sterically hindered biaryls (206)(207)(208) or heteroaromatic molecules (209)(210)(211) were obtained in high yields. Increasing the proportion of the polar solvent (THF/NMP or DMI to 1:2 or 1:3) and/or the temperature to 60 8C was necessary for high yields when challenging substrate combinations were used.…”

“…[120,130,141,207,208] Even though the p-allylpalladium chloride complexes of IPr (166), SIPr (147), IMes (145), IAd (149), and ItBu (148, Scheme 44) all showed conversions greater than 90 % in the arylation of propiophenone with chlorobenzene at 70 8C, the IPr or SIPr complexes were the precatalysts of choice. [208] A variety of functional groups (with the exception of nitrile and aldehyde) [207] were tolerated on the arene moiety, and sterically hindered or heterocyclic substrates also gave moderate to high yields. Aryl-alkyl, dialkyl, and cyclic ketones all proved suitable.…”

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

“…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.…”

“…[208] Das Aren konnte für diese Reaktion viele funktionelle Gruppen tragen (jedoch keine Nitril-und Aldehydgruppen), [207] 3 ] erzeugt. [209] Wäh-rend tert-Butylacetat und Propionat glatt mit einer Reihe von Arylbromiden reagierten, ergab Methylisobutyrat nur schlechte Ausbeuten.…”

Enantioselective α‐Arylation of Cyclic Ketones Catalyzed by a Combination of an Unmodified Cinchona Alkaloid and a Palladium Complex

“…[14] Thus, in order to block active sites on the Pd, the (SIPr)PdA C H T U N G T R E N N U N G (allyl)Cl complex (6) was prepared, which liberates an active NHCPd(0) species under basic conditions. [15] This complex was subjected as Pd source to our standard conditions (Table 4). Without any addition of quinine the reaction proceeded quickly within 90 min and a yield of 48% was obtained.…”