Use of zinc enolate, free from other metals, in enantioselective palladium-catalyzed allylic alkylation

Zinc enolate, free from other metal cations directly prepared from malonate and diethylzinc, was proven to be an excellent nucleophile for enantioselective palladium-catalyzed allylic alkylation, particularly for the allylic cation bearing aromatic rings at the 1- and 3-positions.     

Ir-catalyzed asymmetric allylic alkylation using chiral diaminophosphine oxides: DIAPHOXs. Formal enantioselective synthesis of (−)-paroxetine

An Ir-catalyzed asymmetric allylic alkylation using chiral diaminophosphine oxide is described. Asymmetric allylic alkylation of terminal allylic carbonates proceeded using 5 mol % of Ir catalyst, 5 mol % of DIAPHOX 1i, 10 mol % of NaPF₆, 10 mol % of LiOAc, and N,O-bis(trimethylsilyl)acetamide (BSA), affording the corresponding branched products in excellent yield and in up to 95% ee. The developed catalytic asymmetric reaction was successfully applied to a formal enantioselective synthesis of (−)-paroxetine.     

Enantioselective allylic thioetherification: the effect of phosphoric Acid diester on iridium-catalyzed enantioconvergent transformations

You'll take the high road and I'll take the low road: Enantioenriched allylic thioethers have been synthesized from chiral racemic allylic alcohols. The combination of an Ir-(P,alkene) complex and dibutyl phosphoric acid are required to attain high selectivities. Mechanistic studies uncover an enantioconvergent transformation in which substrate enantiomers react along different pathways to give the same product (see scheme; cod=1,5-cyclooctadiene).     

Planar chiral alkenylferrocene phosphanes: Preparation, structural characterisation and catalytic use in asymmetric allylic alkylation

Planar chiral alkenylferrocene phosphanes, viz. (S_p)-[Fe(η⁵-C₅H₃-1-PPh₂-2-CHCR₂)(η⁵-C₅H₅)] (R = H, (S_p)-2; Ph, (S_p)-5) and (S_p)-[Fe(η⁵-C₅H₃-1-PPh₂-2-(E)-CHCHR)(η⁵-C₅H₅)] (R = Ph, (S_p)-3; C(O)CH₃, (S_p)-6; and CO₂CH₂CH₃, (S_p)-7) have been prepared by alkenylation of (S_p)-2-(diphenylphosphanyl)ferrocenecarboxaldehyde and tested as ligands for enantioselective palladium-catalysed allylic alkylation of 1,3-diphenyprop-2-en-1-yl acetate with dimethyl malonate. All phosphanylalkenes formed active catalysts. However, the induced enantioselectivity was only poor to moderate [12-43% ee after 20 h at room temperature], with the ee’s and configuration of the preferred product strongly depending on the ligand structure. The catalytic results have been related to solution properties (NMR, ESI MS) and the solid-state structural data (X-ray diffraction) of [Pd(η³-1,3-Ph₂C₃H₃){(S_p)-2-η²:κP}]ClO₄ ((S_p)-12), which represent a model of the plausible reaction intermediate.     

Effective synthesis of bicyclodienes via palladium-catalyzed asymmetric allylic alkylation and ruthenium-catalyzed cycloisomerization

[n.3.0]Bicycles (n = 3–6) can be synthesized using palladium-catalyzed asymmetric allylic alkylation followed by ruthenium-catalyzed cycloisomerization. New types of triarylphosphino-1,2-diaminooxazoline ligands show the same high levels of enantioselectivity observed with Trost ligand when employed in Pd-catalyzed allylic alkylation reactions. The enyne products of these allylic alkylation reactions were further elaborated using a Ru-catalyzed redox isomerization process, for which a mechanism is proposed.     

Stereoselective synthesis of substituted 1,2-ethylenediaziridines and their use as ligands in palladium-catalyzed asymmetric allylic alkylation

The double addition of organometallic reagents to fused oxazino-oxazines prepared from glyoxal and (S)-phenylglycinol afforded C₂- or C₁-symmetric 1,2-ethylenebis(β-aminoalcohols), depending on the nature of the organometallic reagent. This route was modified by the use of (S)-valinol and phenylglyoxal as starting materials, and by reduction of the oxazino-oxazines by diborane. Cyclization of the β-aminoalcohol moieties gave 1,2-ethylenediaziridines bearing one substituent/stereocenter on the ring carbon and one, two or no substituents/stereocenters in the ethylene tether. These bis(aziridines) were used as ligands in the Pd-catalyzed allylic alkylation of dimethyl malonate. It was established that the substituent(s) in the carbon tether and the configuration of the corresponding stereocenters have limited influence on the enantioselectivity.     

Asymmetric synthesis of all-carbon quaternary spirocycles via a catalytic enantioselective allylic alkylation strategy

Rapid access to enantioenriched spirocycles possessing a 1,4-dicarbonyl moiety spanning an all-carbon quaternary stereogenic spirocenter was achieved using a masked bromomethyl vinyl ketone reagent. The developed protocol entails an enantioselective palladium-catalyzed allylic alkylation reaction followed by a one-pot unmasking/RCM sequence that provides access to the spirocyclic compounds in good yields and selectivities.     

Palladium-catalyzed asymmetric allylic alkylation of acyclic ketones for synthesis of 2,2-disubsituted pyrrolidine derivatives

Palladium-catalyzed asymmetric allylic alkylation of acyclic ketones represents a significant challenge in organic synthesis. We report herein that the synthesis of chiral 2,2-disubsituted pyrrolidines from acyclic ketones has been accomplished by using catalytic asymmetric method in the presence of Pd(dba)₂ and (R)-binap ligand. Theses reactions occur between allyl methyl carbonate and unstabilized acyclic lithium enolates to provide the products in moderate to good enantioselectivity (up to 81% ee).