A novel copper-catalyzedaerobicoxidative C(NOH)–C(alkyl) bond cleavage reaction of aryl/aralkyl/vinyl ketones for the synthesis of aromatic/acrylic acids is described. A series of ketones having aryl/aralkyl/vinyl at the one end and methyl to any higher alkyl at the other end can be selectively cleaved and converted into the corresponding acids via oxime intermediates.
Highly regioselective vinylation of electron-rich olefins by bromo- as well as chlorostyrenes is effected by palladium catalysis with either mono- or bidentate phosphines in a molecular solvent, with no need for halide scavengers, ionic liquids, or ionic additives. The use of the hemilabile 1,3-bis(diphenylphosphino)propane monoxide (dpppO) as a ligand led to faster reactions of more challenging 2-substituted
When appropriate reaction conditions are used, very high yields of (E)-1-arylalk-1-en-3-one derivatives can be obtained by palladium-catalysed reactions of alk-1-en-3-ones with aryl bromides. The tetraphosphine cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane in combination with [Pd(C3H5)Cl]2 was found to be a very efficient catalyst for this reaction. In general, higher reaction rates were observed with electron-poor aryl bromides, but the electron-rich aryl bromides 1-bromo-4-(dimethylamino)benzene and 4-bromoanisole also led to the arylated enones in high yields. Even with sterically very congested aryl bromides such as 9-bromoanthracene, 1-bromo-2,4,6-trimethylbenzene or 1-bromo-2,4,6-triisopropylbenzene, the expected (E)-1-arylalk-1-en-3-ones were obtained in moderate to good yields. These enones appear to be unstable under the reaction conditions, and the addition of a small amount of hydroquinone to the reaction mixture was found to be crucial, especially for the vinylation of electron-deficient aryl bromides. A variety of alk-1-en-3-ones has been employed, and better results in terms of substrate/catalyst ratios were obtained when oct-1-en-3-one or hex-1-en-3-one was used than when but-1-en-3-one or pent-1-en-3-one was used. It should be noted that several reactions can be performed with as little as 0.1-0.001 mol% catalyst.
Cationic Rhodium(I)/Bisphosphane Complex-Catalyzed Isomerization of Secondary Propargylic Alcohols to α,β-Enones
作者:Ken Tanaka、Takeaki Shoji、Masao Hirano
DOI:10.1002/ejoc.200700071
日期:2007.6
alcohols to α,β-enones. A kinetic resolution of secondary propargylic alcohols proceeded with moderate selectivity with [Rh((R)-BINAP)]OTf as a catalyst. Mechanistic studies revealed that the isomerization proceeds through intramolecular 1,3- and 1,2-hydrogen migration pathways. The isomerization of propargylic diol derivatives was also investigated, which revealed that 1,4-diketones, furans, and α,β-enones
Dual ligand-promoted palladium-catalyzed nondirected C–H alkenylation of aryl ethers
作者:Biao Yin、Manlin Fu、Lei Wang、Jiang Liu、Qing Zhu
DOI:10.1039/d0cc00940g
日期:——
DirectC-H functionalization of aryl ethers remains challenging owing to their low reactivity and selectivity. Herein, a novel strategy for nondirected C-Halkenylation of aryl ethers promoted by a dual ligand catalyst was demonstrated. This catalytic system readily achieved the highly efficient alkenylation of alkyl aryl ethers (anisole, phenetole, n-propyl phenyl ether, n-butyl phenyl ether and benzyl