Permethylated β-Cyclodextrin as Chiral Solvating Agent for the NMR Assignment of the Absolute Configuration of Chiral Trisubstituted Allenes
Permethylated β-cyclodextrin is a convenient chiral solvating agent (CSA) for the determination by NMR of the enantiomeric purities of chiral trisubstituted allenes and of their absolute configuration.All the allene proton resonance are deshielded, and this effect is stronger for the (S)-enantiomer of the allene than for the (R)-enantiomer.
Uccello-Barretta, Gloria,Balzano, Federica,Caporusso, Anna Maria,Iodice, Antonietta,Salvadori, Piero
Negishi Coupling for Highly Selective Syntheses of Allenes via Ligand Effect and Mechanistic Study via SAESI-MS/MS
β-H elimination is an intrinsic problem in transition metal-catalyzed reactions. We describe herein an interesting ligand effect for Et2Zn acting as either ethyl provider or H provider, respectively: by applying SPhos or Gorlos-Phos as the liga
Stereoselective synthesis of chiral 3-aryl-1-alkynes from bromoallenes and heterocuprates
The synthesis of chiral 3-aryl-1-alkynes 3 via cross-coupling of 3-alkyl- and 3,3-dialkyl-1-bromo-1,2-dienes 1 and arylbromocuprates (RCuBr)MgBr-LiBr 2 was examined. With phenylcopper reagents and its para-substituted derivatives, as well as with 2-naphth
Caporusso, Anna Maria,Zampieri, Alessia,Aronica, Laura Antonella,Banti, Donatella
p. 1902 - 1910
(2007/10/03)
Direct Determination of the Enantiomeric Purity of Chiral Trisubstituted Allenes by Using Permethylated Cyclodextrin as a Chiral Solvating Agent
The heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TRIMEB) has been successfully used as convenient chiral solvating agent to determine the enantiomeric composition of chiral trisubstituted allenes by 1H NMR spectroscopy: the analysis of the effect of the molar ration TRIMEB/allene, temperature, and nature of the solvent allowed us to optimize the experimental conditions to enhance the separation between the signals of the two enantiomers of each allene.
Uccello-Barretta, Gloria,Balzano, Federica,Caporusso, Anna Maria,Salvadori, Piero
p. 836 - 839
(2007/10/02)
REACTIONS OF 3-ALKYL- AND 3,3-DIALKYL-1-BROMOALLENES WITH ORGANOCUPRATES: EFFECTS OF THE NATURE OF THE CUPRATE REAGENT ON THE REGIO- AND STEREOSELECTIVITY
Organocuprates induce 1,3- and direct substitution in 3-alkyl- and 3,3-dialkyl-1-bromo-1,2-dienes leading respectively to either terminal acetylenes or allenic hydrocarbons.The nature of the cuprate exerts a prominent role in determining both the regio- and the stereochemistry of these reactions.
Caporusso, Anna Maria,Polizzi, Carmela,Lardicci, Luciano
p. 6073 - 6076
(2007/10/02)
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