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|Title:||Asymmetric synthesis and coordination chemistry of bidentate P-stereogenic phosphines containing ester and thionoester functionalities|
|Source:||Qin, Y., Lang, H., Vittal, J.J., Tan, G.-K., Selvaratnam, S., White, A.J.P., Williams, D.J., Leung, P.-H. (2003-09-15). Asymmetric synthesis and coordination chemistry of bidentate P-stereogenic phosphines containing ester and thionoester functionalities. Organometallics 22 (19) : 3944-3950. ScholarBank@NUS Repository. https://doi.org/10.1021/om0303855|
|Abstract:||The asymmetric syntheses of ester- and thionoester-substituted P-stereogenic phosphines have been achieved between 3,4-dimethyl-1-phenylphosphole (DMPP) and dieneophiles, methyl acrylate and o-ethyl-(E)-2-butenethioate, respectively, in the presence of the enantiomerically pure ortho-palladated (1-(dimethylamino)ethyl)naphthalene as the chiral template. The exo and endo reaction pathways could be controlled stereoselectively by manipulating the number of accessible coordination sites on the chiral palladium template. Both methyl acrylate and o-ethyl-(E)-2-butenethioate underwent intramolecular exo-cycloaddition on the palladium template to form the corresponding P-stereogenic exo-phosphanorbornenes as P-O and P-S bidentate chelates, respectively. When the ester-substituted P-O bidentate template complex was treated with an aqueous solution of sodium chloride under mild reaction conditions, the Pd-O bond was displaced chemoselectively by the chloride ion, but the phosphanorbornene remained coordinated on palladium as a monodentate ligand via its phosphorus donor atom. A similar aqueous treatment of the thionoester-substituted P-S bidentate did not cleave the Pd-S bond but resulted in the rapid hydrolysis of the C(S)-OEt bond to give a new thioester P-S metal chelate. In the intermolecular endo-cycloaddition pathway, only methyl acrylate coupled with DMPP to give a pair of separable ester-substituted endo-cycloadducts. The thionoester-substituted dienophile o-ethyl-(E)-2-butenethioate was not reactive toward the endo-cycloaddition reaction.|
|Appears in Collections:||Staff Publications|
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