56750-84-6Relevant academic research and scientific papers
Effect of hydrogen bonding on ligand substitution and its implication for the Heck reaction
Ruan, Jiwu,Iggo, Jonathan A.,Xiao, Jianliang
, p. 150 - 155 (2019)
Simple hydrogen-bond donating ammonium cations are found to hydrogen-bond with the halo ligand of a key intermediate in the Heck reaction, [Pd(diphosphine)PhBr], and promote the substitution of the halide by a phosphine ligand. Furthermore, upon introduction of a hydorgne bond donor (HBD), the palladium intermediate reacts with an electron-rich olefin to afford the expected Heck product, whereas no reaction was observed without the HBD. These observations support the hypothesis that HBDs accelerate the Heck α-arylation via facilitating halide dissociation from palladium and thereby the ionic pathway.
Ligand-free reusable palladium-catalyzed heck-type coupling reactions of hypervalent iodine reagents under mild conditions
Qu, Xiaoming,Sun, Peng,Li, Tingyi,Mao, Jincheng
supporting information; experimental part, p. 1061 - 1066 (2011/07/09)
Highly effective palladium-catalyzed Heck-type couplings of hypervalent iodine reagents are reported for the first time. It is noteworthy that such reactions could be carried out in the absence of ligand at 40 °C and the catalytic system could be easily reused for five times. Copyright
Ligandless, anionic, arylpalladium halide intermediates in the heck reaction
Carrow, Brad P.,Hartwig, John F.
supporting information; experimental part, p. 79 - 81 (2010/03/25)
(Chemical Equation Presented) We report the isolation and reactivity of a series of "ligandless," anionic arylpalladium complexes of the general structure [Pd(Ar)Br2]22- by the reaction of (tBu3P)Pd(Ar)(Br) and bromide. These anionic complexes insert olefins at room temperature, and these fast insertions indicate that the anionic complexes are kinetically competent to be intermediates in Heck-Mizoroki reactions conducted under "ligandless" conditions (lacking added dative ligand). Kinetic studies showed that the anionic complexes insert olefins much faster than the corresponding neutral, P(t-Bu)3-ligated complexes. Addition of halide to the reaction of the neutral complex (tBu 3P)Pd(Ar)(Br) and styrene led to a significant rate acceleration, suggesting that the anionic complex forms rapidly and reversibly in situ from the neutral species prior to migratory insertion. These data, along with studies on the regioselectivity for reaction of aryl halides with butyl vinyl ether in the presence of the different starting catalysts, are consistent with the intermediacy of the same anionic, arylpalladium intermediates in Heck reactions catalyzed by palladium complexes containing bulky trialkylphosphine ligands as in reactions conducted under ligandless conditions.
Efficient synthesis of alkyl aryl ketones & ketals via palladium-catalyzed regioselective arylation of vinyl ethers
Liu, Mingcui,Hyder, Zeynab,Sun, Yawei,Tang, Weijun,Xu, Lijin,Xiao, Jianliang
supporting information; experimental part, p. 2012 - 2015 (2010/07/04)
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.
Hydrogen-bonding-promoted oxidative addition and regioselective arylation of olefins with aryl chlorides
Ruan, Jiwu,Iggo, Jonathan A.,Berry, Neil G.,Xiao, Jianliang
supporting information; experimental part, p. 16689 - 16699 (2011/02/23)
The first, general, and highly efficient catalytic system that allows a wide range of activated and unactivated aryl chlorides to couple regioselectively with olefins has been developed. The Heck arylation reaction is likely to be controlled by the oxidative addition of ArCl to Pd(0). Hence, an electron-rich diphosphine, 4-MeO-dppp, was introduced to facilitate the catalysis. Solvent choice is critical, however; only sluggish arylation is observed in DMF or DMSO, whereas the reaction proceeds well in ethylene glycol at 0.1-1 mol % catalyst loadings, displaying excellent regioselectivity. Mechanistic evidence supports that the arylation is turnover-limited by the oxidative addition step and, most importantly, that the oxidative addition is accelerated by ethylene glycol, most likely via hydrogen bonding to the chloride at the transition state as shown by DFT calculations. Ethylene glycol thus plays a double role in the arylation, facilitating oxidative addition and promoting the subsequent dissociation of chloride from Pd(II) to give a cationic Pd(II)-olefin species, which is key to the regioselectivity observed.
Regio- And stereoselective intermolecular hydroalkoxylation of alkynes catalysed by cationic gold(I) complexes
Corma, Avelino,Ruiz, Violeta R.,Leyva-Perez, Antonio,Sabater, Maria J.
scheme or table, p. 1701 - 1710 (2010/10/04)
Vinyl ethers and ketals are obtained from the reaction of phenylacetylene derivatives and dimethyl acetylenedicarboxylate (DMAD) with alcohols in good yields and levels of stereoselectivity by using cationic gold(I)-phosphine complexes as catalysts. By choosing the appropriate phosphine, the selective formation of the Z or the E isomer of the vinyl ether can be tuned, and the undesired formation of the ketal can be controlled. The isomerisation of fumarates (Z-isomer) to maleates (E-isomer) is a gold-catalysed process that can be conducted in onepot. When using polyols, 5-membered cyclic ketals are easily isolated by extraction with hexane and the gold complex can be reused.
Hydrogen-bond-directed catalysis: Faster, regioselective and cleaner heck arylation of electron-rich olefins in alcohols
Hyder, Zeynab,Ruan, Jiwu,Xiao, Jianliang
experimental part, p. 5555 - 5566 (2009/06/17)
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.
Oxygen and base-free oxidative heck reactions of arylboronic acids with olefins
Ruan, Jiwu,Li, Xinming,Saidi, Ourida,Xiao, Jianliang
, p. 2424 - 2425 (2008/09/18)
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
Rationally designed pincer-type heck catalysts bearing aminophosphine substituents: PdIV intermediates and palladium nanoparticles
Bolliger, Jeanne L.,Blacque, Olivier,Frech, Christian M.
experimental part, p. 7969 - 7977 (2009/09/08)
The aminophosphine-based pincer complexes [C6H 3-2,6-{XP(piperidinyl)2}2Pd(Cl)] (X = NH 1; X = O 2) are readily prepared from cheap starting materials by sequential addition of 1,1′,1″-phosphinetriyltripiperidine and 1,3-diaminobenzene or resorcinol to solutions of [Pd(cod)(Cl)2] (cod = cyclooctadiene) in toluene under N2 in "one pot". Compounds 1 and 2 proved to be excellent Heck catalysts and allow the quantitative coupling of several electronically deactivated and sterically hindered aryl bromides with various olefins as coupling partners at 140°C within very short reaction times and low catalyst loadings. Increased reaction temperatures also enable the efficient coupling of olefins with electronically deactivated and sterically hindered aryl chlorides in the presence of only 0.01 mol% of catalyst. The mechanistic studies performed rule out that homogeneous Pd0 complexes are the catalytically active forms of 1 and 2. On the other hand, the involvement of palladium nanoparticles in the catalytic cycle received strong experimental support. Even though pincer-type PdIV intermediates derived from 1 (and 2) are not involved in the catalytic cycle of the Heck reaction, their general existence as reactive intermediates (for example, in other reactions) cannot be excluded. On the contrary, they were shown to be thermally accessible. Compounds 1 and 2 show a smooth halide exchange with bromobenzene to yield their bromo derivatives in DMF at 100°C. Experimental observations revealed that the halide exchange most probably proceeded via pincer-type PdIV intermediates. DFT calculations support this hypothesis and indicated that aminophosphine-based pincer-type PdIV intermediates are generally to be considered as reactive intermediates in reactions with aryl halides performed at elevated temperatures.
