Brønsted acid mediated alkenylation and copper-catalyzed aerobic oxidative ring expansion/intramolecular electrophilic substitution of indoles with propargyl alcohols: a novel one-pot approach to cyclopenta[c]quinolines.
Copper-catalyzed oxidative ring-expansion/intramolecular electrophilic substitution of 3-dienylindoles leading to cyclopenta[c]quinolines and 3-indenylindoles under aerobic conditions is described. The precursors, 3-dienylindoles, are formed via Friedel-Crafts alkenylation followed by isomerization reactions of 2-substituted indoles with tertiary propargyl alcohols under Brønsted acid mediation. The methyl (sp(3)-C) group present in the propargyl alcohol becomes a part of a six-membered ring in the final ring-expansion products, the cyclopenta[c]quinolines which are fluorescence active. Based on these observations, a novel one-pot strategy for ring expansion from indole to cyclopenta[c]quinoline is discovered.
School of Chemistry, University of Hyderabad, Hyderabad-500046, Telangana, India.
G
G
Gangadhararao
School of Chemistry, University of Hyderabad, Hyderabad-500046, Telangana, India.
Anasuyamma
A
Uruvakilli
School of Chemistry, University of Hyderabad, Hyderabad-500046, Telangana, India.
K C Kumara
KC
Swamy
D000480:Alkynes / Q000737:chemistry*; D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D003500:Cyclization; D006575:Heterocyclic Compounds, 3-Ring / Q000138:chemical synthesis* / Q000737:chemistry; D007211:Indoles / Q000737:chemistry*; D015394:Molecular Structure; D010084:Oxidation-Reduction; D020005:Propanols / Q000737:chemistry*; D011804:Quinolines / Q000138:chemical synthesis* / Q000737:chemistry
D000480:Alkynes; D006575:Heterocyclic Compounds, 3-Ring; D007211:Indoles; D020005:Propanols; D011804:Quinolines; D003300:Copper; C028255:propargyl alcohol