14588-08-0Relevant articles and documents
Lightly fluorous [Pd(OAc)2{P(C6H4-p-SiMe2CH2CH2C6F13)3}2] in the methoxycarbonylation of styrene: Formation, performance and stability of the catalyst system
de Pater, Jeroen J.M.,Deelman, Berth-Jan,Elsevier, Cornelis J.,van Koten, Gerard
, p. 334 - 340 (2006)
The fluorous palladium(II) complex, [Pd(OAc)2{P(C6H4-p-SiMe2CH2CH2C6F13)3}2], has been prepared and characterized. Its application in the catalytic methoxycarbonylation of styrene in an MeOH/CF3C6H5 mixture (1/1 v/v) has been explored and its activity was compared to that of [Pd(OAc)2(PPh3)2]. The fluorous complex showed a lower activity but a significantly higher selectivity towards the branched product. Investigation of both the conversion-versus-time and i:n ratio-versus-time profiles showed an unusual behaviour in the case of the fluorous complex, which has been ascribed to the formation of a dinuclear species for the fluorous complex.
The ubiquitous cross-coupling catalyst system 'Pd(OAc)2'/2PPh3 forms a unique dinuclear PdI complex: An important entry point into catalytically competent cyclic Pd3 clusters
Scott, Neil W. J.,Ford, Mark J.,Schotes, Christoph,Parker, Rachel R.,Whitwood, Adrian C.,Fairlamb, Ian J. S.
, p. 7898 - 7906 (2019/09/06)
Palladium(ii) acetate 'Pd(OAc)2'/nPPh3 is a ubiquitous precatalyst system for cross-coupling reactions. It is widely accepted that reduction of in situ generated trans-[Pd(OAc)2(PPh3)2] affords [Pd0(PPh3)n] and/or [Pd0(PPh3)2(OAc)]- species which undergo oxidative addition reactions with organohalides-the first committed step in cross-coupling catalytic cycles. In this paper we report for the first time that reaction of Pd3(OAc)6 with 6 equivalents of PPh3 (i.e. a Pd/PPh3 ratio of 1?:?2) affords a novel dinuclear PdI complex [Pd2(μ-PPh2)(μ2-OAc)(PPh3)2] as the major product, the elusive species resisting characterization until now. While unstable, the dinuclear PdI complex reacts with CH2Cl2, p-fluoroiodobenzene or 2-bromopyridine to afford Pd3 cluster complexes containing bridging halide ligands, i.e. [Pd3(X)(PPh2)2(PPh3)3]X, carrying an overall 4/3 oxidation state (at Pd). Use of 2-bromopyridine was critical in understanding that a putative 14-electron mononuclear 'PdII(R)(X)(PPh3)' is released on forming [Pd3(X)(PPh2)2(PPh3)3]X clusters from [Pd2(μ-PPh2)(μ2-OAc)(PPh3)2]. Altering the Pd/PPh3 ratio to 1?:?4 forms Pd0(PPh3)3 quantitatively. In an exemplar Suzuki-Miyaura cross-coupling reaction, the importance of the 'Pd(OAc)2'/nPPh3 ratio is demonstrated; catalytic efficacy is significantly enhanced when n = 2. Employing 'Pd(OAc)2'/PPh3 in a 1?:?2 ratio leads to the generation of [Pd2(μ-PPh2)(μ2-OAc)(PPh3)2] which upon reaction with organohalides (i.e. substrate) forms a reactive Pd3 cluster species. These higher nuclearity species are the cross-coupling catalyst species, when employing a 'Pd(OAc)2'/PPh3 of 1?:?2, for which there are profound implications for understanding downstream product selectivities and chemo-, regio- and stereoselectivities, particularly when employing PPh3 as the ligand.
Novel imidazole based heterocycles
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Page/Page column 18; 20; 22-23, (2008/12/08)
The present invention is directed to novel imidazopyrazine compounds useful as kinase inhibitors and as such would be useful in treating certain conditions and diseases, especially inflammatory conditions and diseases and proliferative disorders and conditions, for example, cancers.
