- Applications of planar-chiral heterocycles in enantioselective catalysis: Cu(I)/bisazaferrocene-catalyzed asymmetric ring expansion of oxetanes to tetrahydrofurans
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A planar-chiral, C2-symmetric bisazaferrocene ligand is shown to control the stereochemistry of Cu(I)-catalyzed ring expansions of oxetanes to tetrahydrofurans.
- Lo, Michael M.-C.,Fu, Gregory C.
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p. 2621 - 2634
(2007/10/03)
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- Enantiospecific ring expansion of oxetanes: Stereoselective synthesis of tetrahydrofurans
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Enantiospecific ring expansion of oxetanes to tetrahydrofurans with diazoacetic acid ester was found to be catalyzed by the copper complex of (7R,7′R)-7,7′-di(1-tert-butyldimethylsiloxy-1-methylethyl)-6, 6′,7,7′-tetrahydro-5H,5′H-2,2′-bi-1,1′-pyrindine (4). For example, the reaction of (R)-2-phenyloxetane of 89% ee and tert-butyl diazoacetate with Cu-4 complex as a catalyst provided (2S,3R)-tert-butyl 3-phenyltetrahydrofuran-2-carboxylate of 92% ee as a major product, while that of (S)-2-phenyloxetane of 85% ee provided (2S,3S)-tert-butyl 3-phenyltetrahydrofuran-2-carboxylate of 93% ee as a major one.
- Ito, Katsuji,Yoshitake, Miwa,Katsuki, Tsutomu
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p. 305 - 317
(2007/10/02)
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- Asymmetric Carbene C-O Insertion Using Optically Active Bipyridine-Copper Complex as a Catalyst. Ring Expansion of Oxetanes to Tetrahydrofurans
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Copper complex of (7R,7R')-di(1-t-butyldimethylsiloxy-1-methylethyl)-6,6',7,7'-tetrahydro-5H,5'H-2,2'-bi-1,1'-pyridine (3) was found to be an effective catalyst for asymmetric carbene insertion reaction into the C-O bond of oxetanes.For example, the react
- Ito, Katsuji,Katsuki, Tsutomu
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p. 1857 - 1860
(2007/10/02)
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