- Catalytic asymmetric methallylation and propargylation of aldehydes with bis(((S)-binaphthoxy)(isopropoxy)titanium) oxide
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New and highly efficient enantioselective methallylation and propargylation of achiral aldehydes with methallyltributyltin and allenyltributyltin, respectively, can be achieved with high enantioselectivity under the influence of chiral bis(((S)-binaphthoxy)(isopropoxy)titanium) oxide as catalyst.
- Konishi, Shunsuke,Hanawa, Hideo,Maruoka, Keiji
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- Highly stereoselective kinetic resolution of α-allenic alcohols: An enzymatic approach
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A highly efficient lipase AK-catalyzed direct kinetic resolution of a variety of α-allenic alcohols was developed. With the complementary to previous studies, the current reaction system is effective on a broad range of substituents (R1) at C(1), such as alkyl, aryl, alkenyl, and alkynyl groups. The Jones-Burgess empirical model was modified to interpret the reversed selectivity during the acetylation of secondary alcohol. The methyl group at C(2) of allenic alcohols implied a small structural adjustment in the catalytic triad of lipase AK, representing a potential direction for future site-directed mutagenesis.
- Li, Wenhua,Lin, Zuming,Chen, Long,Tian, Xuechao,Wang, Yan,Huang, Sha-Hua,Hong, Ran
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supporting information
p. 603 - 606
(2016/01/20)
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- Studies on the synthesis of durhamycin A: Stereoselective synthesis of a model aglycone
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(Chemical Equation Presented) A stereoselective synthesis of the model aglycone corresponding to the anti-HIV aureolic acids durhamycins A (1) and B (2) is described.
- Pragani, Rajan,Roush, William R.
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supporting information; experimental part
p. 4613 - 4616
(2009/05/27)
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- Catalytic enantioselective allenylation reactions of aldehydes with tethered bis(8-quinolinolato) (TBOx) chromium complex
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The utility of the new class of chiral ligand, tethered bis(8-quinolinol) (TBOxH), is further explored. Its chromium complex, TBOxCr(III)Cl, effectively catalyzes the asymmetric allenylation reactions of various aldehydes at room temperature with high yie
- Xia, Guoyao,Yamamoto, Hisashi
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p. 496 - 497
(2007/10/03)
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- Catalytic asymmetric allylation of aldehydes and related reactions with bis(((S)-binaphthoxy)(isopropoxy)titanium) oxide as a μ-oxo-type chiral Lewis acid
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A new, chiral bis-TiIV of type 3 has been designed and can be utilized for strong activation of aldehyde carbonyls, thereby allowing a new catalytic enantioselective allylation of aldehydes with allyltributyltin. The chiral bis-TiIV catalyst (S,S)-3 can be readily prepared either by treatment of bis(triisopropoxy)titanium oxide with (S)-BINOL or by treatment of ((S)-binaphthoxy)isopropoxytitanium chloride with silver(I) oxide. Treatment of hydrocinnamaldehyde with allyltributyltin under the influence of chiral bis-TiIV oxide (S,S)-3 generated in situ (10 mol%) in CH 2Cl2 afforded an allylation product in 84% yield and with 99% ee. This asymmetric allylation with non-racemic bis-TiIV oxide 3 and partially resolved (S)-BINOL shows a positive nonlinear effect in correlation of the enantiopurity of the allylation product with the ee of the (S)-BINOL. Chiral bis-TiIV oxide (S,S)-3 can also be utilized for related reactions such as asymmetric methallylation and propargylation of aldehydes with high enantioselectivity. This asymmetric approach provides a very useful way of obtaining high reactivity and selectivity through the simple introduction of the M-O-M unit into the design of chiral Lewis acid catalysts.
- Hanawa, Hideo,Uraguchi, Daisuke,Konishi, Shunsuke,Hashimoto, Takuya,Maruoka, Keiji
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p. 4405 - 4413
(2007/10/03)
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- Catalytic asymmetric allenylation: Regulation of the equilibrium between propargyl- and allenylstannanes during the catalytic process
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Achiral substrates 1 and 2 can be regioselectively converted into chiral allenyl alcohols 3 through the title reaction [Eq. (1)] with the synergetic reagent iPrSBEt2 and a chiral Ti(IV) catalyst. The dramatic regioselectivity originates from the regulation of the equilibrium between propargyl- and allenylstannanes during the catalytic process.
- Yu, Chan-Mo,Yoon, Sook-Kyung,Baek, Kwangwoo,Lee, Jae-Young
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p. 2392 - 2395
(2007/10/03)
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