Electric Literature of 19132-06-0, As an important bridge between the micro and macro material world, chemistry is one of the main methods and means for humans to understand and transform the material world.Mentioned the application of 19132-06-0,(2S,3S)-Butane-2,3-diol.
Mechanistic Studies of Diastereoselective Cyclopropanation via Homochiral Ketals. 1. Dioxolane Structural Effects
Compounds structurally related to 2-cyclohexen-1-one 1,4-di-O-benzyl-L-threitol ketal were prepared and subjected to the Simmons-Smith cyclopropanation.From these experiments a mechanistic model for diastereoselective cyclopropanation of common ring systems (five-, six-, and seven-membered) has been formulated.Diastereoselectivity is thought to result from preferential chelation of the Simmons-Smith reagent at the least sterically hindered lone pair of electrons on the dioxolane oxygen proximal to the alkene.It is found that the presence of oxygen atoms in the dioxolane appendages provide sites for competitive chelation of the reagent, which can antagonize the diastereoselection due to chelation at dioxolane oxygen.That chelation by dioxolane oxygen does occur and is responsible for diastereoselectivity is inferred from studies with a hydrocarbon model system.Surprisingly, both dioxolane appendages are shown to be necessary for optimum diastereoselection since, under the conditions of the Simmons-Smith cyclopropanation, 2-cycloalken-1-one ethylene ketals are reversibly ring opened to zwitterionic intermediates.
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Reference£º
Synthesis and Crystal Structure of a Chiral?C3-Symmetric Oxygen Tripodal Ligand and Its Applications to Asymmetric Catalysis,
Chiral lanthanide(III) complexes of sulphur¨Cnitrogen¨Coxygen ligand derived from aminothiourea and sodium?D-camphor-¦Â-sulfonate