title: N-alkenyl indoles as useful intermediates for alkaloid synthesis.
abstract: A mild cross-coupling reaction to access several N-alkenyl-substituted indoles has been developed. The coupling procedure involves treating a NH-indole with various alkenyl bromides using a combination of 10 mol % of copper(I) iodide and 20 mol % of ethylenediamine as the catalyst in dioxane at 110 °C in the presence of K(3)PO(4) as the base. When treated with acid, these unique enamines produce a dimeric product derived from a preferred protonation reaction at the enamine π-bond. A cationic cyclization reaction of the readily available 2-(2-(1H-indol-1-yl)allyl)cyclopentanol was utilized to construct tetracyclic indole derivatives with a quaternary stereocenter attached to the C(2)-position of the indole ring. An alternative strategy for selective functionalization at the C(2)-position of a N-alkenyl-substituted indole derivative that was also studied involves a radical cyclization of a xanthate derivative. The work described provides an attractive route to the tetracyclic core of some vinca alkaloids, including the tetrahydroisoquinocarbazole RS-2135.
authors: Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA.
authors: Hao
authors: H
authors: Li
authors: Nawong
authors: N
authors: Boonnak
authors: Albert
authors: A
authors: Padwa
mesh_terms: D000470:Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry; D000475:Alkenes / Q000737:chemistry*; D002384:Catalysis; D003300:Copper / Q000737:chemistry; D003432:Cross-Linking Reagents / Q000737:chemistry; D003500:Cyclization; D006576:Heterocyclic Compounds, 4 or More Rings / Q000138:chemical synthesis* / Q000737:chemistry; D007211:Indoles / Q000737:chemistry*; D015394:Molecular Structure; D013237:Stereoisomerism; D014748:Vinca Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D000470:Alkaloids; D000475:Alkenes; D003432:Cross-Linking Reagents; D006576:Heterocyclic Compounds, 4 or More Rings; D007211:Indoles; D014748:Vinca Alkaloids; D003300:Copper