Jackson, Mark; O’Broin, Calvin Quince; Muller-Bunz, Helge; Guiry, Patrick J. published the artcile< Enantioselective synthesis of sterically hindered α-allyl-α-aryl oxindoles via palladium-catalysed decarboxylative asymmetric allylic alkylation>, Category: chiral-phosphine-ligands, the main research area is enantioselective synthesis allyl aryl oxindole; palladium catalyst decarboxylative asym allylic alkylation.
The highly enantioselective synthesis of sterically hindered α-allyl-α-aryl oxindoles possessing an all-carbon quaternary stereocenter at the oxindole 3-position was developed. The key step in the synthetic route employed was a novel one-pot, two-step synthesis of α-aryl-β-amido allyl ester substituted oxindoles in good yields of 41-75% (13 examples) by interception of an unstable allyl ester intermediate through reaction with aryllead triacetate reagents. Pd-Catalyzed decarboxylative asym. allylic alkylation (DAAA) was optimized with 2,4,6-trimethoxyphenyl as the aryl-containing substrate. A screen of chiral P,N- and P,P-based ligands showed that the ANDEN-Ph Trost ligand was the most effective, affording the corresponding α-allyl-α-aryl oxindole product in 96% yield and 99% ee. A substrate scope of a further 12 α-aryl-β-amido allyl ester substituted oxindoles showed that products containing bulky di-ortho-methoxy substituted arenes and naphthyl groups were formed in high ee’s (94-98%), whereas those lacking this substitution pattern were formed in more moderate levels of enantioselectivities (56-63% ee). Surprisingly, the 2,6-dimethylphenyl-substituted substrate afforded the O-allylated product in contrast to the expected C-allylated product. A crystal structure was obtained of the 2,4,6-trimethoxyphenyl-substituted α-allyl-α-aryl oxindole product which enabled us to identify the absolute stereochem. of the quaternary stereocenter formed. A plausible explanation to rationalize the sense of enantioselection observed in these DAAA transformations is also proposed.
Organic & Biomolecular Chemistry published new progress about Allylic alkylation, stereoselective. 152140-65-3 belongs to class chiral-phosphine-ligands, and the molecular formula is C54H42N2O2P2, Category: chiral-phosphine-ligands.
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Phosphine ligand,
Chiral phosphine ligands in asymmetric synthesis. Molecular structure and absolute configuration of (1,5-cyclooctadiene)-(2S,3S)-2,3-bis(diphenylphosphino)butanerhodium(I) perchlorate tetrahydrofuran solvate