223449-58-9Relevant academic research and scientific papers
Palladium-catalyzed enantioselective allylic substitution in the presence of monodentate furanoside phosphoramidites
Majdecki, Maciej,Jurczak, Janusz,Bauer, Tomasz
, p. 799 - 807 (2015)
A library of monodentate furanoside phosphoramidites, easily synthesized from inexpensive D-xylose and optically pure 1,1-bi-2-naphthol (BINOL), was used as ligands for the palladium-catalyzed allylic alkylation and amination. The matched pair was formed from D-xylose-derivatives and (S)-BINOL. The asymmetric induction depends strongly on the substituent at the C5 of the carbohydrate backbone; both bulky 5-O-pivaloyl and 5-deoxy derivatives gave excellent results, whereas ligands with trityl protection at position C5 induced low ee values with reversal of configuration. The solvent used for the addition is also of great importance with highest enantioselectivities observed in diethyl ether. The best results for both alkylation and amination, up to 98-99 ee, were obtained for sterically demanding allylic acetates. Single is better: New carbohydrate ligands bearing a single 1,1-bi-2-naphthol (BINOL)-derived phosphoramidite moiety are developed and successfully applied to the palladium-catalyzed asymmetric allylic substitution. The enantioselectivities are equal or better than those obtained for similar systems containing two BINOL moieties and reach up to 99 ee.
A d -Camphor-Based Schiff Base as a Highly Efficient N,P Ligand for Enantioselective Palladium-Catalyzed Allylic Substitutions
Liu, Qiao-Ling,Chen, Weifeng,Jiang, Qun-Ying,Bai, Xing-Feng,Li, Zhifang,Xu, Zheng,Xu, Li-Wen
, p. 1495 - 1499 (2016/05/02)
New Schiff bases derived from chiral d-camphor were determined to be effective phosphine ligands for the asymmetric palladium-catalyzed allylic alkylation of activated methylene compounds, the allylic etherification of alcohols, and the allylic amination of primary amines or secondary amines, in which the corresponding products with various functional groups were achieved in good yields with excellent enantioselectivities (up to >99 % ee). Remarkably, the palladium catalyst derived from Schiff base L2 afforded the highest level of enantioselectivity reported to date for allylic substitution reactions, including allylic etherification and allylic amination, which revealed the privileged role of d-camphor-derived Schiff bases in palladium-catalyzed allylic substitution reactions.
Changing the palladium coordination to phosphinoimidazolines with a remote triazole substituent
De La Fuente, Veronica,Marcos, Rocio,Cambeiro, Xacobe C.,Castillon, Sergio,Claver, Carmen,Pericas, Miquel A.
supporting information; experimental part, p. 3255 - 3261 (2012/01/17)
Phosphinoimidazoline (PHIM) ligands bearing a triazolylmethyl substituent at the sp3 nitrogen atom in the imidazoline ring lead to highly improved enantioselectivity (up to 99% ee) in allylic substitution reactions with respect to analogous ligands with substituents lacking the triazole unit. NMR and theoretical studies support a shift in the coordination mode of the PHIM ligand to palladium, triggered by a very favourable interaction with the triazole unit. Copyright
Towards continuous flow, highly enantioselective allylic animation: ligand design, optimization and supporting
Popa, Dana,Marcos, Rocio,Sayalero, Sonia,Vidal-Ferran, Anton,Pericas, Miquel A.
experimental part, p. 1539 - 1556 (2011/02/26)
A family of enantiopure diphenylphosphinooxazolines (PHOX) containing in their structures a sterically tunable alkoxymethyl group (-CH2OR) has been optimized for the palladium-catalyzed asymmetric allylic amination. The optimal catalyst (R=CH3), depicting very high catalytic activity and broad scope applicability, has been further modified to include an ω-alkynyloxy substituent of variable length for polymer supporting via click chemistry, and has been anchored onto slightly cross-linked azidomethyl poly(styrene). The length of a polymethylene chain connecting the PHOX unit with the 1,2,3-triazole linker has been optimized, and the first polymer-supported PHOX ligands for the highly enantioselective allylic amination have been prepared in this manner. Conditions for catalyst recovery and reuse in microwave-promoted amination reactions have been established, and the system has been finally adapted to continuous flow operation.
