1361395-95-0Relevant academic research and scientific papers
Pd-catalyzed carbonylative α-arylation of aryl bromides: Scope and mechanistic studies
Nielsen, Dennis U.,Lescot, Camille,Gogsig, Thomas M.,Lindhardt, Anders T.,Skrydstrup, Troels
supporting information, p. 17926 - 17938 (2014/01/17)
Reaction conditions for the three-component synthesis of aryl 1,3-diketones are reported applying the palladium-catalyzed carbonylative α-arylation of ketones with aryl bromides. The optimal conditions were found by using a catalytic system derived from [Pd(dba)2] (dba=dibenzylideneacetone) as the palladium source and 1,3-bis(diphenylphosphino)propane (DPPP) as the bidentate ligand. These transformations were run in the two-chamber reactor, COware, applying only 1.5 equivalents of carbon monoxide generated from the CO-releasing compound, 9-methylfluorene-9-carbonyl chloride (COgen). The methodology proved adaptable to a wide variety of aryl and heteroaryl bromides leading to a diverse range of aryl 1,3-diketones. A mechanistic investigation of this transformation relying on 31P and 13C NMR spectroscopy was undertaken to determine the possible catalytic pathway. Our results revealed that the combination of [Pd(dba)2] and DPPP was only reactive towards 4-bromoanisole in the presence of the sodium enolate of propiophenone suggesting that a [Pd(dppp)(enolate)] anion was initially generated before the oxidative-addition step. Subsequent CO insertion into an [Pd(Ar)(dppp)(enolate)] species provided the 1,3-diketone. These results indicate that a catalytic cycle, different from the classical carbonylation mechanism proposed by Heck, is operating. To investigate the effect of the dba ligand, the Pd0 precursor, [Pd(η3-1-PhC 3H4)(η5-C5H5)], was examined. In the presence of DPPP, and in contrast to [Pd(dba)2], its oxidative addition with 4-bromoanisole occurred smoothly providing the [PdBr(Ar)(dppp)] complex. After treatment with CO, the acyl complex [Pd(CO)Br(Ar)(dppp)] was generated, however, its treatment with the sodium enolate led exclusively to the acylated enol in high yield. Nevertheless, the carbonylative α-arylation of 4-bromoanisole with either catalytic or stoichiometric [Pd(η3-1-PhC3H4) (η5-C5H5)] over a short reaction time, led to the 1,3-diketone product. Because none of the acylated enol was detected, this implied that a similar mechanistic pathway is operating as that observed for the same transformation with [Pd(dba)2] as the Pd source. CO-operation is the key! The first palladium-catalyzed carbonylative α-arylation of aryl bromides is described. A wide array of different aryl 1,3-diketones can be isolated in good-to-excellent yields using only stoichiometric amounts of CO (see scheme). A mechanistic study is presented that suggests the need for enolate coordination prior to oxidative addition when [Pd(dba)2] is employed as the precatalyst. Copyright
Palladium-catalyzed carbonylative α-arylation for accessing 1,3-diketones
Gogsig, Thomas M.,Taaning, Rolf H.,Lindhardt, Anders T.,Skrydstrup, Troels
supporting information; experimental part, p. 798 - 801 (2012/03/09)
With a hint of CO: The first Pd-catalyzed carbonylative α-arylations of simple ketones with carbon monoxide is presented for the direct synthesis of 1,3-diketones (see scheme). The method uses only stoichiometric amounts of CO, and hence allows for the si
