title: Efficient Syntheses of Substituted Carbazoles and Cyclopent[b]indoles from 1-Methyl-3-(benzotriazol-1-ylmethyl)indole.
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 cyclopent[b]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 cyclopent[b]indoles 15 and 16with a high degree of stereoselectivity.
authors.affiliation: Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200.
authors.forename: Alan R.
authors.initials: AR
authors.lastname: Katritzky
authors.forename: Guifen
authors.initials: G
authors.lastname: Zhang
authors.forename: Linghong
authors.initials: L
authors.lastname: Xie
authors.forename: Ion
authors.initials: I
authors.lastname: Ghiviriga