Abstract
A series of simple heteroarylidene malonate-type bis(oxazoline) ligands 4 and 5 were applied to the Palladium-catalyzed allylic alkylation reaction, and the ligand 4a bearing a phenyl group afforded excellent enantioselectivity (up to 96% ee) for the allylic alkylation product. Other substrates were also examined, giving the allylic alkylated products in high yield but with poor ee values.
Highlights
Palladium-catalyzed asymmetric allylic substitution is a versatile, widely used process in organic synthesis for the enantioselective formation of C–C and C-heteroatom bonds
Examples of N,N-chelating ligands for catalytic allylic alkylation are abundant they are less common than other types of ligands
In order to expand the potential of the ligands 4 and 5 with thiophene or furan units, we applied them in the palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2propen-1-yl acetate with dimethyl malonate, which is commonly used as a model reaction for evaluation of chiral catalysts in much of the literature
Summary
Palladium-catalyzed asymmetric allylic substitution is a versatile, widely used process in organic synthesis for the enantioselective formation of C–C and C-heteroatom bonds. Most of the efficient chiral ligands developed for this reaction are mixed bidentate donor ligands with P–N chelating mode [5,7]. Examples of N,N-chelating ligands for catalytic allylic alkylation are abundant they are less common than other types of ligands. During the past two decades, chiral bis(oxazolines) (BOX), as a class of typical N,N-bidentate ligand, are among the most widely studied ligands in catalytic asymmetric synthesis. Some bis(oxazolines) have been applied to the palladium-catalyzed allylic alkylation and demonstrated high enantioselectivity [8,9,10,11,12,13,14,15]
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