Well-Defined Air-Stable Palladium HASPO Complexes for Efficient Kumada-Corriu Cross-Couplings of (Hetero)Aryl or Alkenyl Tosylates
作者:Lutz Ackermann、Anant R. Kapdi、Sabine Fenner、Christoph Kornhaaß、Carola Schulzke
DOI:10.1002/chem.201002386
日期:2011.3.1
Palladium complexes of representative heteroatom‐substituted secondary phosphine oxide (HASPO) preligands were synthesized and fully characterized, including X‐ray crystal structure analysis. Importantly, these well‐defined complexes served as highly efficientcatalysts for Kumada–Corriu cross‐couplingreactions of aryl, alkenyl, and even heteroaryl tosylates. Particularly, an air‐stable catalyst derived
代表的钯络合物ħ etero一汤姆取代小号econdary p hosphine ø西德(HASPO)preligands合成并充分表征,包括X射线晶体结构分析。重要的是,这些定义明确的络合物可作为Kumada-Corriu芳基,烯基乃至杂芳基甲苯磺酸酯交叉偶联反应的高效催化剂。特别是,由廉价的PinP(O)H衍生的空气稳定型催化剂显示出极高的催化效力,这导致在极低的反应条件下,在足够宽泛的反应条件下,低催化剂负载下的交叉偶联。
Photocatalysis of oligo(p-phenylenes): photoreductive production of hydrogen and ethanol in aqueous triethylamine
Oligo(p-phenylenes) (OPP-n), p-terphenyl (OPP-3) to p-sexiphenyl (OPP-6), catalyze water-reductive H2 formation and reduction of concomitantly formed acetaldehyde to ethanol upon irradiation of heterogeneous suspensions in aqueous organic solution in the presence of triethylamine (TEA) and RuCl3. Colloidal Ru0 is photoformed in situ to work as an electron relay. The activity of OPP-n increases with the number of phenylene units except for the cases of OPP-3 and of the alkylated derivatives, where the net photocatalytic activities are higher, mainly due to the effective homogeneous catalysis, since their solubilities in the solvents employed are significantly larger. The homogeneous photocatalysis of OPP-3 leads not only to H2 evolution but also to effective formation of ethanol in the absence of colloidal Ru0, being accompanied by photo-Birch reduction of OPP-3. Dynamics studies of OPP-3 reveal that photocatalysis should be initiated by formation of the excited singlet state of OPP-3 (1OPP-3*), which is reductively quenched by TEA at a rate controlled by diffusion to produce the OPP-3 radical anion (OPP-3.-) and the TEA radical cation (TEA.+). From laser flash photolysis and pulse radiolysis experiments, it is concluded that electron transfer from OPP-3.- leads to effective reduction of water to H2 catalyzed by Ru0 colloid. Furthermore, it is confirmed that OPP-3.- gives electrons directly to acetaldehyde without any electron relays like colloidal metals, resulting in the formation of ethanol. During photocatalysis, OPP-3 itself undergoes photo-Birch reduction to some extent.
Gold(I)-Catalyzed Tandem C−H and C−C Activation (Cleavage)
作者:Min Jiang、Le-Ping Liu、Min Shi、Yuxue Li
DOI:10.1021/ol902593f
日期:2010.1.1
(Cyclopropylidenecyclohexyl)benzene derivatives, a kind of methylenecyclopropane (MCP) containing a cyclohexyl group, can undergo an interesting tandem intramolecular C−H and C−C bond activation through dehydrogenated rearrangement in the presence of AuPPh3Cl/AgOTf by transferring three hydrogen atoms from cyclohexane to cyclopropane, affording the corresponding biaryl derivatives in moderate to good