34939-28-1Relevant articles and documents
Palladium assisted alkylation-insertion reactions of chiral ene-carbamates
Laidig,Hegedus
, p. 527 - 532 (1995)
Palladium(II) complexes of chiral ene-carbamate 2 underwent efficient, stereoselective alkylation by malonate carbanions having pendent unsaturated side chains. The resulting σ-alkylpalladium(II) complexes underwent efficient insertion of carbon monoxide to produce esters. Insertion of the pendent unsaturated groups was less efficient, and led to mixtures of insertion products with little stereoselectivity.
Asymmetric allylic substitution reactions with a xylophos-Pd catalyst
Pamies, Oscar,Ruiz, Aurora,Net, Gemma,Claver, Carmen,Kalchhauser, Hermann,Widhalm, Michael
, p. 1173 - 1179 (2000)
The chiral diphosphine ligand xylophos (1) was tested as an auxiliary in palladium catalyzed allylic substitution reactions. Whereas its activity was found to be generally good only in the case of 1,3-diphenylprop-2-en-1-yl acetate, a fair level of asymmetric induction was achieved with sodium dimethyl malonate (83% ee) and benzylamine (66% ee) as nucleophiles.
Bis(aminophosphine)-nickel complexes as efficient catalysts for alkylation of allylic acetates with stabilized nucleophiles
Bricout, Herve,Carpentier, Jean-Francois,Mortreux, Andre
, p. 6105 - 6108 (1996)
The alkylation of a variety of allylic acetates with dimethyl malonate catalysed by nickel-diphosphine complexes is reported. It is shown that in most cases bis(aminophosphine) type ligands lead to much more efficient catalysts than dppb and other usual d
Memory effects in palladium-catalyzed allylic alkylations of 2-cyclohexen-1-yl acetate
Svensen, Nina,Fristrup, Peter,Tanner, David,Norrby, Per-Ola
, p. 2631 - 2640 (2007)
The objective of this work was to characterize the enantiospecificity of the allylic alkylation of enantioenriched 2-cyclohexen-1-yl acetate with the enolate ion of dimethyl malonate catalyzed by unsymmetrical palladium catalysts. The precatalysts employe
Carbamate-based P,O-ligands for asymmetric allylic alkylations
Pálv?lgyi, ádám Márk,Schnürch, Michael,Bica-Schr?der, Katharina
, (2020/05/18)
Herein we report the design and successful catalytic application of modified Trost-ligands in asymmetric allylic alkylation (AAA) reactions. A small set of carbamate-monophosphine P,O-ligands has been prepared in a straightforward two-step synthetic procedure. After optimization of the reaction conditions, high catalytic activities and excellent enantioselectivity up to >99% have been attained.
Catalytic Hydroetherification of Unactivated Alkenes Enabled by Proton-Coupled Electron Transfer
Knowles, Robert R.,Metrano, Anthony J.,Tsuchiya, Yuto,Tsui, Elaine
supporting information, p. 11845 - 11849 (2020/05/22)
We report a catalytic, light-driven method for the intramolecular hydroetherification of unactivated alkenols to furnish cyclic ether products. These reactions occur under visible-light irradiation in the presence of an IrIII-based photoredox catalyst, a Br?nsted base catalyst, and a hydrogen-atom transfer (HAT) co-catalyst. Reactive alkoxy radicals are proposed as key intermediates, generated by direct homolytic activation of alcohol O?H bonds through a proton-coupled electron-transfer mechanism. This method exhibits a broad substrate scope and high functional-group tolerance, and it accommodates a diverse range of alkene substitution patterns. Results demonstrating the extension of this catalytic system to carboetherification reactions are also presented.
An improved class of phosphite-oxazoline ligands for Pd-catalyzed allylic substitution reactions
Biosca, Maria,Salto, Joan,Magre, Marc,Norrby, Per-Ola,Pamies, Oscar,Dieguez, Montserrat
, p. 6033 - 6048 (2019/07/19)
A method for generation of Pd/phosphite-oxazoline catalysts containing an alkyl backbone chain has been successfully applied to Pd-catalyzed allylic substitution reactions. By carefully selecting the substituents at both the alkyl backbone chain and the oxazoline of the ligand, as well as the configuration of the biaryl phosphite group, high activities (TOF > 8000 mol substrate × (mol Pd × h)?1) and excellent enantioselectivities (ee's up to 99%) have been achieved for many hindered and unhindered substrates with a wide range of C-, O-, and N-nucleophiles (73 substitution products in total). Moreover, DFT and NMR studies of the key Pd-allyl complexes allowed us to better understand the origin of the excellent enantioselectivities observed experimentally. The useful application of the Pd/phosphite-oxazoline catalysts was demonstrated by the syntheses of many chiral carbobicycles, with multiples stereocenters, by simple sequential reactions involving Pd-allylic substitution and either 1,6-enyne cyclization or Pauson?Khand enyne cyclization.
A readily accessible and modular carbohydrate-derived thioether/selenoether-phosphite ligand library for Pd-catalyzed asymmetric allylic substitutions
Margalef, Jèssica,Borràs, Carlota,Alegre, Sabina,Pàmies, Oscar,Diéguez, Montserrat
supporting information, p. 12632 - 12643 (2019/08/26)
A large library of thioether/selenoether-phosphite ligands have been tested in the Pd-catalyzed asymmetric allylic substitution reaction. The presented ligands are derived from cheap and available carbohydrates and they are air-stable solids and easy to handle. Their highly modular nature has made it possible to achieve excellent enantioselectivities in the substitution of a range of hindered and unhindered substrates (ees up to 99% and 91%, respectively). In addition, twelve C-, N- and O-nucleophiles can be efficiently introduced, independently of their nature. Among the whole library, ligands that contain an additional chiral centre in the alkyl backbone chain next to the phosphite group and an enantiopure biaryl phosphite group provided the best enantioselectivities. In general, there is a cooperative effect between these two chiral elements, and therefore, a matched combination between them is necessary to achieve the highest enantioselectivities. However, in the case of cyclic substrates, this cooperative effect is less pronounced and advantageously, both enantiomers of the product can be obtained by setting up the desired configuration of the biaryl phosphite group. Studies of the key Pd-π-allyl intermediates allowed us to better understand the enantioselectivities obtained experimentally.
Ligand's electronegativity controls the sense of enantioselectivity in BIFOP-X palladium-catalyzed allylic alkylations
Brüllingen, Eric,Neud?rfl, J?rg-Martin,Goldfuss, Bernd
supporting information, p. 15743 - 15753 (2019/10/19)
Palladium-catalyzed allylic alkylations of sodium dimethyl malonate with 1,3-diphenylallyl acetate, employing BIFOP-H (biphenylbisfencholphosphite) and analogue (i.e. BIFOP-X, X = D, Cl, CN, N3) ligands, all yield (S)-enantiomeric products, while alkylations to cyclohexenyl acetate yield the (R)-enantiomeric C-C coupling product (up to 91% yield, 70% ee). The fluoro derivative BIFOP-F however, "switches" the sense of enantioselectivity, yielding the (R)-enantiomer for 1,3-diphenylallyl acetate and the (S)-enantiomer for the cyclohexenyl acetate (up to 92% yield, 67% ee). Computational analyses of transition structures (M06-2X-D3/def2-TZVP//B3LYP-D3(BJ)/def2-SVP) for these Pd-catalyzed allylic alkylations reproduce the experimental preference of BIFOP-H (and analogue BIFOP-X ligands) for (R)- or (S)-enantiomeric products of 1,3-diphenylallyl or cyclohexenyl acetate, respectively. The "F-switch" of the sense of enantioselectivity from BIFOP-H to BIFOP-F is also apparent computationally and is found (NBO-analyses) to originate from lp(Pd) → σ?(P-O) or lp(Pd) → σ?(P-F) hyperconjugations. The higher electronegativity of F vs. H in BIFOP-X hence controls the sense of enantioselectivity of this Pd-catalyzed allylic alkylation.
A protic ionic liquid as an atom economical solution for palladium catalyzed asymmetric allylic alkylation
Guerrero-Ríos, Itzel,Ortiz-Ramírez, Alfonso H.,Van Leeuwen, Piet W. N. M.,Martin, Erika
, p. 3739 - 3744 (2018/03/21)
The asymmetric allylic alkylation of rac-1,3-diphenyl-3-acetoxyprop-1-ene (I) catalysed by palladium and diverse phosphorus containing ligands [(S)-BINAP, (R,R)-Chiraphite and (R,R)-Et-Duphos] in an ionic liquid [HDBU][OAc] was successfully performed, ach
