The reaction of lithium trialkylalkynylborates with oxiranes : γ-Hydroxyketone synthesis and stereoselective preparation of trisubstituted ethylenes |
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Authors: | M Naruse K Utimoto H Nozaki |
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Institution: | Department of Industrial Chemistry, Kyoto University, Kyoto, Japan |
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Abstract: | Lithium trialkylalkynylborates (1) react with oxiranes (2) to give non-isolable intermediates 3 which subsequently afford either γ-hydroxyketones 5, trisubstituted ethylenes of homoallylic alcohol type 6 or a tetrasubstituted ethylene 7 upon appropriate treatment with NaOH/H2O2, AcOH or NaOH/I2, respectively. The reaction of oxiranes with 1 proceeds in high regioselectivity and the resulting homoallylic alcohols 6 are of nearly 100% (E) configuration. A straight chain γ-hydroxyketone 16 is obtained in the reaction of methyloxirane with the ate-complex (1), which has been prepared from lithium acetylide ethylenediamine complex and trihexylborane. |
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