- Efficient synthesis of alkyl aryl ketones & ketals via palladium-catalyzed regioselective arylation of vinyl ethers
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The combination of Pd(OAc)2 with 1,3-bis(diphenylphosphino) propane (dppp) in ethylene glycol constitutes a high-performance catalytic system for highly regioselective arylation of a range of electron-rich vinyl ethers by aryl bromides to provide, upon hydrolysis, alkyl aryl ketones and cyclic ketals in good yields with up to 3.75 × 105 TON and 15625 h-1 TOF.
- Liu, Mingcui,Hyder, Zeynab,Sun, Yawei,Tang, Weijun,Xu, Lijin,Xiao, Jianliang
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supporting information; experimental part
p. 2012 - 2015
(2010/07/04)
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- Oxygen and base-free oxidative heck reactions of arylboronic acids with olefins
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A mild and efficient protocol for palladium-catalyzed oxidative Heck reactions of arylboronic acids with both electron-rich and -deficient olefins is described. In contrast to the normal oxidative Heck coupling, this new method works in the absence of a base, oxygen, or other external oxidants. With a wide variety of substrates tolerated, the method broadens the scope of palladium-catalyzed coupling reactions. Copyright
- Ruan, Jiwu,Li, Xinming,Saidi, Ourida,Xiao, Jianliang
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p. 2424 - 2425
(2008/09/18)
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- Hydrogen-bond-directed catalysis: Faster, regioselective and cleaner heck arylation of electron-rich olefins in alcohols
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A general method for the regioselective Heck reaction of electronrich olefins is presented. Fast, highly regioselective Pd-catalysed α-arylation of electron-rich olefins, vinyl ethers (1a-d), hydroxyl vinyl ethers (1e,f), enamides (1g,h) and a substituted vinyl ether (1i) has been accomplished with a diverse range of aryl bromides (2a-r), for the first time, in cheap, green and easily available alcohols with no need for any halide scavengers or salt additives. The reaction proceeds with high efficiency, leading exclusively to the a-products, in 2-propanol and particularly in ethylene glycol. In the latter, the arylation can be catalysed at a palladium loading of 0.1 mol% and finish in as short a time as 0.5 h. The remarkable performance of the alcohol solvents in promoting a regiocontrol is attributed to their hydrogen-bond- donating capability, which is believed to facilitate the dissociation of halide anions from PdII, and hence, the generation of a key ionic Pd II-olefin intermediate responsible for the a product. This belief is further strengthened by the study of a benchmark arylation reaction in 21 different solvents. The study revealed that exclusive α-regioselective arylation takes place in almost all of the protic solvents, and there is a rough correlation between the α-arylation rates and the solvent parameter ETN. The method is simpler, cleaner and more general than those established thus far.
- Hyder, Zeynab,Ruan, Jiwu,Xiao, Jianliang
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experimental part
p. 5555 - 5566
(2009/06/17)
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- Ionic liquid-promoted, highly regioselective Heck arylation of electron-rich olefins by aryl halides
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Palladium-catalyzed regioselective Heck arylation of the electron-rich olefins, vinyl ethers 1a-d, enamides 1e-g, and allyltrimethylsilane 1h, has been accomplished in imidazolium ionic liquids with a wide range of aryl bromides and iodides instead of the commonly used, but commercially unavailable and expensive, aryl triflates. The reaction proceeded with high efficiency and remarkable regioselectivity without the need for costly or toxic halide scavengers, leading exclusively to substitution by aryl groups of diverse electronic and steric properties at the olefinic carbon α to the heteroatom of 1a-g and β to the heteroatom of 1h. In contrast, the arylation reaction in molecular solvents led to mixtures of regioisomers under similar conditions. Several lines of evidence point to the unique regiocontrol stemming from the ionic environment provided by the ionic liquid that alters the reaction pathway. The chemistry provides a simple, effective method for preparing branched, arylated olefins and contributes to the extension of Heck reaction to a wider range of substrates.
- Mo, Jun,Xu, Lijin,Xiao, Jianliang
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p. 751 - 760
(2007/10/03)
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