Efficient Syntheses of Substituted Carbazoles and Cyclopent[b]indoles from 1-Methyl-3-(benzotriazol-1-ylmethyl)indole |
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Authors: | Katritzky Alan R Zhang Guifen Xie Linghong Ghiviriga Ion |
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Institution: | Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200. |
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Abstract: | 1-Methyl-3-(benzotriazol-1-ylmethyl)indole (1) undergoes lithiation and 1,4-addition with a variety of alpha,beta-unsaturated ketones and aldehydes. Subsequent treatment with an acidic resin in refluxing 1,4-dioxane causes intramolecular cyclization followed by aromatization to furnish a wide range of 1,3-di-, 2,3-di-, and 1,2,3-trisubstituted carbazoles 6a-j and 8 in moderate to excellent yields. NMR study is described to discriminate between structures of types 6 and 8 on the basis of (1)H-(13)C long-range correlation. Treatment of 1 with styrenes in the presence of zinc bromide results in formal 3 + 2] cycloaddition to give cyclopentb]indoles 14a-c in good yields. When 1 is first lithiated and reacts with electrophiles, the resulting alkylation products undergo similar 3 + 2] additions with styrenes to give 1-functionalized cyclopentb]indoles 15 and 16with a high degree of stereoselectivity. |
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