Asymmetric cross-coupling of racemic α-bromo esters with aryl Grignard reagents catalyzed by cyclopropane-based bisoxazolines cobalt complexes. Issue 14 (15th August 2016)

• Record Type: Journal Article
• Authors: Liu, Feipeng; Bian, Qinghua; Mao, Jianyou; Gao, Zidong; Liu, Dan; Liu, Shikuo; Wang, Xueyang; Wang, Yu; Wang, Min; Zhong, Jiangchun
• Is Part Of: Tetrahedron, asymmetry. Volume 27:Issue 14/15(2016)
• Page Start: 663
• Page End: 669
• Publication Date: 2016-08-15
• Subjects: Asymmetry (Chemistry) -- Periodicals; 547.005
• DOI: 10.1016/j.tetasy.2016.05.010
• Languages: English
• ISSNs: 0957-4166

Abstract

Graphical abstract: Abstract: Four new cyclopropane-based bisoxazolines were synthesized and applied to cobalt-catalyzed cross-coupling reactions between racemic α-bromo esters and aryl Grignard reagents. The reaction afforded a series of chiral α-arylalkanoic esters with high yields and good enantioselectivities (up to 93% yield, 92:8 er). This research focuses on the cross-coupling between racemic α-bromopropanoate and p -isobutylphenyl Grignard reagent's which provides ibuprofen ester efficiently. Furthermore, ibuprofen ester 7e was transformed into ( S )-ibuprofen (99:1 er) via hydrolysis and recrystallization. Abstract : (4 S, 4′ S )-2, 2′-((1 S, 2 R )-3, 3-Dimethylcyclopropane-1, 2-diyl)bis(4-ethyl-4, 5-dihydrooxazole): C15 H24 N2 O2 [ α ]D 20 = −107.8 ( c 1.13, CHCl3 ) Source of chirality: ( S )-2-aminobutan-1-ol Absolute configuration: (4 S, 4′ S ) Abstract : (4 S, 4′ S )-2, 2′-((1 S, 2 R )-3, 3-Dimethylcyclopropane-1, 2-diyl)bis(4-isobutyl-4, 5-dihydrooxazole): C19 H32 N2 O2 [ α ]D 20 = −141.6 ( c 1.22, CHCl3 ) Source of chirality: ( S )-2-amino-4-methylpentan-1-ol Absolute configuration: (4 S, 4′ S ) Abstract : (4 S, 4′ S )-2, 2′-((1 S, 2 R )-3, 3-Dimethylcyclopropane-1, 2-diyl)bis(4- sec -butyl)-4, 5-dihydrooxazole): C19 H32 N2 O2 [ α ]D 20 = −125.4 ( c 1.11, CHCl3 ) Source of chirality: (2 S )-2-amino-3-methylpentan-1-ol Absolute configuration: (4 S, 4′ S ) Abstract : (4 S, 4′ S )-2, 2′-((1 S, 2 R )-3, 3-Dimethylcyclopropane-1, 2-diyl)bis(4-phenethyl-4, 5-dihydrooxazole): C27 H32 N2 O2 [ α ]D 20 = −134.8 ( c 1.36, CHCl3 ) Source of chirality: ( S )-2-amino-4-phenylbutan-1-ol Absolute configuration: (4 S, 4′ S ) Abstract : ( S )-2-(4-Isobutylphenyl)propanoic acid [( S )-ibuprofen]: C13 H18 O2 Er = 99:1 [ α ]D 20 = +52.3 ( c 1.0, CHCl3 ) Source of chirality: Ligand 2b Absolute configuration: ( S )