56750-84-6Relevant articles and documents
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.
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.
