155184-90-0Relevant academic research and scientific papers
A new optically active monodentate phosphine ligand, (R)-(+)-3-diphenylphosphino-3'-methoxy-4,4'-biphenanthryl (MOP-phen): Preparation and use for palladium-catalyzed asymmetric reduction of allylic esters with formic acid
Hayashi,Iwamura,Uozumi,Matsumoto,Ozawa
, p. 526 - 532 (1994)
(R)-(+)-3-Diphenylphosphino-3'-methoxy-4,4'-biphenanthryl (MOP-phen, 8) was prepared starting with (-)-3,3'-dihydroxy-4,4'-biphenanthryl. The absolute configuration of (+)-8 was determined to be R by X-ray crystal structure analysis of its π-allylpalladium complex. The monodentate optically active phosphine 8 was found to be a more enantioselective ligand than (R)-(+)-2-diphenylphosphino-2'-methoxy- 1,1'-binaphthyl (MOP, 1a) for palladium-catalyzed asymmetric reduction of allylic esters with formic acid giving optically active olefins of up to 85% ee.
Enantioselective synthesis of allylboronates bearing a tertiary or quaternary B-substituted stereogenic carbon by NHC-Cu-catalyzed substitution reactions
Guzman-Martinez, Aikomari,Hoveyda, Amir H.
supporting information; scheme or table, p. 10634 - 10637 (2010/11/05)
Allylic substitutions that afford α-substituted allylboronates bearing B-substituted tertiary or quaternary carbon stereogenic centers are presented. C-B bond-forming reactions, catalyzed by chiral bidentate Cu-NHC complexes, are performed in the presence of commercially available bis(pinacolato)diboron. Transformations proceed in high yield (up to >98%) and site selectivity (>98% SN2′), and in up to >99:1 enantiomer ratio. Trans- or cis-disubstituted alkenes can be used; alkyl- (linear as well as branched) and aryl-trisubstituted allylic carbonates serve as effective substrates. Allylboronates that bear a quaternary carbon center are air-stable and can be easily purified by silica gel chromatography; in contrast, secondary allylboronates cannot be purified in the same manner and are significantly less stable. Oxidation of the enantiomerically enriched products furnishes secondary or tertiary allylic alcohols, valuable small molecules that cannot be easily obtained in high enantiomeric purity by alternative synthesis or kinetic resolution approaches.
Palladium-catalyzed asymmetric reduction of racemic allylic esters with formic acid: Effects of phosphine ligands on isomerization of π- allylpalladium intermediates and enantioselectivity
Kawatsura, Motoi,Uozumi, Yasuhiro,Ogasawara, Masamichi,Hayashi, Tamio
, p. 2247 - 2257 (2007/10/03)
A new MOP ligand (lb), (R)-(+)-2-(bis(3- trifluoromethylphenyl)phosphino)-2'-methoxy-1,1'-binaphthyl, was found to be more enantioselective than other MOP ligands for the palladium-catalyzed asymmetric reduction of α,α-disubstituted allylic esters with formic acid. The reduction of DL-2-(1-naphthyl)-3-buten-2-yl benzoate gave 3-(1-naphthyl)- 1-butene of 90% ee. The higher enantioselectivity of lb is ascribed to fast syn-anti isomerization of π-allylpalladium intermediates formed by oxidative addition of allylic ester to a palladium(0) species. The rate of syn-anti isomerization was measured by the magnetization saturation transfer in 1H NMR. (C) 2000 Elsevier Science Ltd.
