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.
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
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.
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.
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.
