- Neighboring group participation in Lewis acid-promoted [3 + 4] and [3 + 5] annulations. The synthesis of oxabicyclo[3.n.1]alkan-3-ones
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Lewis acids are employed as catalysts in the annulation of 1,4- and 1,5-dicarbonyl dielectrophiles with bis(trimethylsilyl) end ethers of β-diketones and β-keto esters. A variety of 2-(alkoxycarbonyl)-m-oxabicyclo[3.n.1]alkan-3-ones can be constructed by this process in which two new carbon-carbon bonds are generated. Unusually high regiocontrol is observed, and good to excellent stereochemical control can be achieved at virtually every position on the new carbocycles. Intramolecular neighboring group participation is proposed to explain the unusually high selectivities attained in the annulation reaction.
- Molander, Gary A.,Camera, Kimberly O.
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- New method for asymmetrically synthesizing natural product (-)-Euscapholide isomer
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The invention relates to a new method for asymmetrically synthesizing a natural product (-)-Euscapholide isomer. The method comprises the following steps: carrying out methoxybenzyl group protection on (R)-3-hydroxymethyl butyrate used as an initial raw material, reducing by using diisobutylaluminium hydride, carrying out a Mukaiyama aldol reaction, reducing by using sodium borohydride, carrying out ring closure under acidic conditions, eliminating hydroxyl groups, and deprotecting to complete asymmetric total synthesis of the target molecule 1. The method has the advantages of novel and reasonable synthesis route design, cheap and easily available raw material, simple operating process, mild reaction conditions, efficient completion of the asymmetric total synthesis of the Euscapholide isomer with two chiral centers, and single product configuration.
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- Hauser-Heck: Efficient Synthesis of γ-Aryl-β-ketoesters en Route to Substituted Naphthalenes
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γ-Aryl-β-ketoesters can be prepared in one step from aryl bromides and bis(trimethylsilyl) enol ethers using catalytic amounts of Pd(dba)2/t-Bu3P and stoichiometric amounts of Bu3SnF. The wide range of γ-(hetero)aryl-β-ketoesters that can be obtained illustrate the scope and limitations of this novel Hauser-Heck combination. γ-Aryl-β-ketoesters with a 1,3-dioxane acetal in the ortho position can easily be transformed into the hydroxy naphthoate in very good yield. Aqueous formic acid at 65 °C provides optimal conditions for this deprotective aromatization.
- Wagner, Frederic,Harms, Klaus,Koert, Ulrich
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supporting information
p. 5670 - 5673
(2015/12/08)
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- Total synthesis of (±)-bisabosqual A
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The synthesis of the novel squalene synthase inhibitor, bisabosqual A, was completed in 14 steps (longest linear sequence) from commercially available starting materials. The doubly convergent route employs a tandem 5-exo, 6-exo radical cyclization as the
- Am Ende, Christopher W.,Zhou, Zhou,Parker, Kathlyn A.
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supporting information
p. 582 - 585
(2013/03/13)
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- Stereospecific synthesis of thienamycin from penicillin
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A stereospecific conversion of penicillin to thienamycin, using diisopropylamine borane and magnesium trifluoroacetate to prepare the hydroxyethyl side chain and acetoacetate dianion equivalent disilylethyl to prepare the β-ketoester side chain.
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- THERMAL 1,5-REARRANGEMENT OF A SILYL GROUP FROM OXYGEN TO CARBON
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Trialkylsilyl ethers of 1,1-dioxygenated butadienes, substituted at position 3 by electron releasing substituents, undergo thermal rearrangement with 1,5-migration of the silyl group from oxygen to carbon.
- Anderson, Gerard,Cameron, Donald W.,Feutrill, Geoffrey I.,Read, Roger W.
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p. 4347 - 4348
(2007/10/02)
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