Palladium-Catalyzed Asymmetric Allylic Substitution Reactions Using New Chiral Phosphinite−Oxazoline Ligands Derived from d-Glucosamine

Abstract

Novel 2-alkyl- or 2-aryl-4,5-(4,6-O-benzylidene-3-O-(diphenylphosphino)-1,2-dideoxy-α-d-glucopyrano)-[2,1-d]-2-oxazolines (5a−f) have been prepared from d-glucosamine hydrochloride. They work effectively as chiral ligands and provide a high level of enantiomeric excess in palladium-catalyzed allylic alkylation and amination reactions. The allylic alkylation of 1,3-diphenyl-3-acetoxyprop-1-ene with dimethyl malonate proceeds smoothly in the presence of 0.25 mol % [Pd(η3-C3H5)Cl]2 and the chiral ligand 5a having the smallest substituent on oxazoline at 0 °C within 6 h to furnish the highest enantiomeric excess (96% ee). The ligand 5a is also effective for the Pd-catalyzed amination of ethyl 1,3-diphenylprop-2-enyl carbonate, leading to the corresponding allylic amine in 94% ee. The full scope and limitations using ligands 5a − f in the allylic substitution reactions are described.

Glucose ferrocenyl-oxazolines: Coordination behavior toward [Pd(η3-allyl)Cl]2 studied by ESI-MS

“…In a second step the corresponding mono or bisamides were converted into the oxazolines by a ring closing reaction in the presence of a Lewis acid. In accordance to literature, SnCl 4 was found to be the most suitable reagent for the oxaz- oline syntheses [31,32]. The reactions were carried out in dry CH 2 Cl 2 at room temperature.…”

Screening of a Modular Sugar‐Based Phosphite–Oxazoline Ligand Library in Asymmetric Pd‐Catalyzed Heck Reactions

“…Oxazoline alcohols 3-6 are easily prepared on a large scale from d-glucosamine. [7] All the ligands were stable during purification on neutral alumina under an atmosphere of argon and were isolated as white solids. They are stable at room temperature and very stable to hydrolysis.…”

“…Compounds 3-6 were prepared by previously described methods. [7] Phosphorochloridites were prepared as previously described. [12] Ligands L1 a-c, L1 e, L2 a, L3 a, L4 a have been previously synthesised.…”

Palladium-Catalyzed Enantioselective Allylic Substitution

“…17) [92]. They have also adapted their work on P-P ligands L29, based on previous work by Uemura [93,94]. Near perfect enantioselectivity was achieved with L54 [95].…”