Synlett 2010(9): 1389-1393  
DOI: 10.1055/s-0029-1219819
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Copper(II) Acetate Promoted Intramolecular Carboamination of Alkenes: An Efficient Synthesis of Pentacyclic Sultams

K. C. Majumdar*, Abu Taher, Raj Kumar Nandi
Department of Chemistry, University of Kalyani, Kalyani 741235, West Bengal, India
e-Mail: kcm_ku@yahoo.co.in;
Further Information

Publication History

Received 5 January 2010
Publication Date:
09 April 2010 (online)

Abstract

Copper(II) acetate promoted intramolecular carboamination reactions of 5-allyl-N-sulfonylated coumarins and quinolones have been described. The hitherto unreported pentacyclic sultams, obtained by the oxidative cyclization in high yields, are potential intermediates in the synthesis of nitrogen-containing heterocyclic compounds.

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Procedure for the Preparation of Compound 7a
A mixture of compound 5a (100 mg, 0.272 mmol), Cu(OAc)2 (148 mg, 0.815 mmol), and Cs2CO3 (89 mg, 0.272 mmol) in MeCN (7 mL) was heated in a sealed tube for 7 h. After completion of the reaction, the reaction mixture was cooled and filtered through Celite. The solvent was distilled off. The resulting crude product was purified by column chromatography over silica gel (60-120 mesh) using PE-EtOAc (50:50) mixture as eluent to give compound 7a. Yield 82%, colorless solid; mp 276 ˚C. IR (KBr): νmax = 1592, 1663, 2923 cm. ¹H NMR (500 MHz, CDCl3): δ = 1.31 (t, J = 7.1 Hz, 3 H), 3.08-3.16 (m, 2 H), 3.49 (dd, J = 9.2, 15.9 Hz, 1 H), 3.75 (dd, J = 5.9, 15.7 Hz, 1 H), 4.28 (q, J = 7.1 Hz, 2 H), 5.07-5.13 (m, 1 H), 6.68 (d, J = 9.5 Hz, 1 H), 7.20 (d, J = 9.0 Hz, 1 H), 7.32 (d, J = 7.5 Hz, 1 H), 7.36 (t, J = 7.5 Hz, 1 H), 7.46 (d, J = 9.5 Hz, 1 H), 7.48 (t, J = 7.5 Hz, 1 H), 7.76 (d, J = 9.1 Hz, 1 H), 7.83 (d, J = 7.5 Hz, 1 H) ppm. ¹³C NMR (100 MHz, CDCl3): δ = 12.7, 33.1, 34.5, 37.6, 61.7, 114.1, 117.3, 119.6, 122.8, 124.3, 127.6, 127.9, 129.7, 132.8, 134.2, 134.4, 136.3, 137.0, 138.5, 161.2 ppm. HRMS: m/z calcd for C20H18N2O3S [M + Na]+: 389.0936; found: 389.0936.