- Catalytic Enantioselective Direct Aldol Addition of Aryl Ketones to α-Fluorinated Ketones
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The catalytic enantioselective synthesis of α-fluorinated chiral tertiary alcohols from (hetero)aryl methyl ketones is described. The use of a bifunctional iminophosphorane (BIMP) superbase was found to facilitate direct aldol addition by providing the strong Br?nsted basicity required for rapid aryl enolate formation. The new synthetic protocol is easy to perform and tolerates a broad range of functionalities and heterocycles with high enantioselectivity (up to >99:1 e.r.). Multi-gram scalability has been demonstrated along with catalyst recovery and recycling. 1H NMR studies identified a 1400-fold rate enhancement under BIMP catalysis, compared to the prior state-of-the-art catalytic system. The utility of the aldol products has been highlighted with the synthesis of various enantioenriched building blocks and heterocycles, including 1,3-aminoalcohol, 1,3-diol, oxetane, and isoxazoline derivatives.
- Barber, David M.,Dixon, Darren J.,Thomson, Connor J.
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supporting information
p. 5359 - 5364
(2020/02/28)
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- A three-alkyl (α - alkoxy vinyl) tin synthetic method (by machine translation)
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The invention relates to a three-alkyl (α - alkoxy vinyl) tin synthetic method, is characterized in that the under the protection of nitrogen, the fatty alcohol alkali metal compound, tetramethyl ethylene diamine is dissolved in the hexane, adds by drops positively BuLi hexane solution, then the α - alkoxy vinyl ether dissolved in tetrahydrofuran, in dropping into the mixture, then cooled to - 78 °C; three alkyl tin chloride dissolved with anhydrous in tetrahydrofuran, at this temperature drop in the mixed solution is added, TLC detection reaction, after the reaction is completed in under ice bath adds full and ammonium chloride aqueous solution quenching reaction, the above-mentioned solution is filtered, the filtrate liquid, collecting the organic phase, combined with the organic phase, the organic phase and then sequentially for washing and saturated salt water washing, then filtering the concentrated job to three alkyl (- alkoxy vinyl) tin of the crude product. The invention has the operation is relatively safe, convenient and can be large-scale the advantage of reduced cost. (by machine translation)
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Paragraph 0016; 0017
(2017/01/02)
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- A one-pot diazotation-fluorodediazoniation reaction and fluorine gas for the production of fluoronaphthyridines
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Several synthetic routes to 7-fluoro-2-methoxy-8-methyl-1,5-naphthyridine (1) are presented, and their suitability for scale-up is discussed. The way of introducing the fluorine atom is crucial. Early routes start from commercially available fluorinated building blocks or employ F+ reagents like SelectFluor and delivered up to 70 kg of 7-fluoro-2-methoxy-1,5-naphthyridine (18). To prepare for larger scales, the focus turned to the use of HF or elemental fluorine, both one of the cheapest sources of fluorine. The first method, a one-pot diazotation-fluorodediazoniation with 6-methoxy-1,5- naphthyridin-3-amine (9) in HF gave the fluorinated naphthyridine 18 in high yield and purity without isolation of the unstable diazonium salt, the latter being a severe drawback of the related Balz-Schiemann protocol. The second method relies on the use of fluorine gas for a surprisingly selective ortho-fluorination of 6-methoxy-1,5-naphthyridin-4-ol (10).
- Abele, Stefan,Schmidt, Gunther,Fleming, Matthew J.,Steiner, Heinz
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p. 993 - 1001
(2014/10/15)
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- Ruthenium-catalysed hydrogenation of alkynylstannanes with migration of the stannyl group
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Molecular hydrogen adds to aliphatic and aromatic alkynylstannanes in the presence of a ruthenium catalyst, pushing the stannyl group to the adjacent carbon atom to give α-substituted vinylstannanes. This is the first achievement of hydrogenation of alkynylstannanes, which is applicable also to the deuteration affording precursors for an important class of deuterium-labeled compounds. Copyright
- Shirakawa, Eiji,Morita, Ryotaro,Tsuchimoto, Teruhisa,Kawakami, Yusuke
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p. 13614 - 13615
(2007/10/03)
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