- Synthesis of Ynolates via Double Deprotonation of Nonbrominated Esters
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Herein, we report a double deprotonation method used for the preparation of ynolates starting from nonbrominated 2,6-di-tert-butylphenyl esters. The current method is superior to the previously described double lithium/halogen exchange approach because easily accessible starting materials are used. This method will be especially useful for preparation of ynolates bearing functional groups in organic synthesis.
- Sun, Jun,Yoshiiwa, Toshiya,Iwata, Takayuki,Shindo, Mitsuru
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supporting information
p. 6585 - 6588
(2019/09/30)
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- Scandium trifluoromethanesulfonate as an extremely active Lewis acid catalyst in acylation of alcohols with acid anhydrides and mixed anhydrides
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Scandium trifluoromethanesulfonate (triflate), which is commercially available, is a practical and useful Lewis acid catalyst for acylation of alcohols with acid anhydrides or the esterification of alcohols by carboxylic acids in the presence of p-nitrobenzoic anhydrides. The remarkably high catalytic activity of scandium triflate can be used for assisting the acylation by acid anhydrides of not only primary alcohols but also sterically-hindered secondary or tertiary alcohols. The method presented is especially effective for selective macrolactonization of ω-hydroxy carboxylic acids.
- Ishihara, Kazuaki,Kubota, Manabu,Kurihara, Hideki,Yamamoto, Hisashi
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p. 4560 - 4567
(2007/10/03)
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- Acylation and Esterification of the Aryloxide Ligand in . Crystal Structures of , Hbhmap and O=C(dbmp)But (Hdbmp = 2,6-di-tert-butyl-4-methylphenol, Hbhmap = 3-tert-butyl-2-hydroxy-5-methylacetophenone)
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The reaction of (Hdbmp = 2,6-di-tert-butyl-4-methylphenol) with O=C(Cl)Me leads to acylation of one of the dbmp ligands and affords 1 (Hbhmap = 3-tert-butyl-2-hydroxy-5-methylacetophenone).Hydrolysis of 1 yields uncomplex
- Power, Michael B.,Bott, Simon G.,Bishop, Elizabeth J.,Tierce, Kelli D.,Atwood, Jerry L.,Barron, Andrew R.
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p. 241 - 247
(2007/10/02)
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- ACYCLIC STEREOSELECTION-13; ARYL ESTERS: REAGENTS FOR THREO-ALDOLIZATION
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Preformed Li enolates of hindered aryl esters condense with aldehydes to give predominantly threo aldols.The method has been explored with esters 3 (DMP propionate), 4 (BHT propionate), 5 (DBHA propionate).DMP propionate reacts with benzaldehyde and α-unbranched aliphatic aldehydes to give threo:erythro ratios of about 6.5:1.However, with α-branched aliphatic aldehydes, ester 3 gives only threo-aldols.BHT propionate and DBHA propionate give only threo-aldols with all aldehydes studied.The DMP aldols may be converted into β-hydroxy acids by simple hydrolysis with KOH in aqueous methanol.BHT aldols cannot be hydrolyzed without retroaldolization.However, these aldols can be reduced to diastereomerically pure 1,3-diols.The DBHA aldols can converted into β-hydroxy acids by a method involving oxidation with ceric ammonium nitrate (CAN) in aqueous acetonitrile.Threo-selectivity is also seen in the condensations of DMP butyrate (15), DBHA butyrate (16), DMP pentenoate (17), and BHT pentenoate (18).The approach has been utilized in a stereoselective synthesis of racemic methyl corynomycolate.
- Heathcock, Clayton H.,Pirrung, Michael C.,Montgomery, Stephen H.,Lampe, John
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p. 4087 - 4095
(2007/10/02)
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- Acyclic Stereoselection. 9. Stereochemistry of the Addition of Lithium Enolates to α-Alkoxy Aldehydes
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The stereochemistry of addition of lithium enolates derived from esters and ketones to the α-alkoxy aldehydes 1-5 has been investigated.In all cases, the predominant product is that predicted by application of Felkin's model for asymmetric induction and by assuming the alkoxy group to be the "large" group.The Cram cyclic model for asymmetric induction is not followed.Stereostructures have been assigned by a combination of conversion to products of known stereostructure, 13C and 1H NMR correlations, and single-crystal X-ray analysis.
- Heathcock, Clayton H.,Young, Steven D.,Hagen, James P.,Pirrung, Michael C.,White, Charles T.,VanDerveer, Don
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p. 3846 - 3856
(2007/10/02)
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