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Synlett 2008(18): 2851-2855  
DOI: 10.1055/s-0028-1083502
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Synthesis of Cyclic Sulfonamides via Pd-Catalyzed Intramolecular Coupling Reaction: An Expedient Approach to Polycyclic Sultams

K. C. Majumdar*, Shovan Mondal, Nirupam De
Department of Chemistry, University of Kalyani, Kalyani 741235, WB, India
Fax: +91(33)25828282; e-Mail: kcm_ku@yahoo.co.in;
Further Information

Publication History

Received 7 July 2008
Publication Date:
15 October 2008 (online)

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Abstract

A divergent synthetic approach to polycyclic sultams utilizing intramolecular ligand-free intramolecular coupling reaction is described.

Key words

sulfonamide drugs - sultams - ligand-free cross-coupling reaction - palladium acetate

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Compound 3a: white solid, mp 133-134 ˚C; yield 95%. IR (KBr): 1342, 1160 cm-¹. ¹H NMR (400 MHz, CDCl3): δ = 2.45 (s, 3 H), 4.50 (s, 4 H,), 6.99 (t, 2 H, J = 7.8 Hz), 7.13 (t, 2 H, J = 8.4 Hz), 7.33 (t, 6 H, J = 8.4 Hz), 7.73 (d, 2 H, J = 8.2 Hz). ¹³C NMR (75 MHz, CDCl3): δ = 21.4, 52.2, 123.2, 127.1, 127.2, 128.8, 129.7, 130.0, 132.4, 134.7, 136.4, 143.5. HRMS: m/z calcd for C21H19Br2NO2S: 529.9335 [M + Na], 531.9381 [M + 2 + Na], 533.9339 [M + 4 + Na]; found: 529.9401 [M + Na], 531.9401 [M + 2 + Na], 533.9401 [M + 4 + Na].

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General Procedure for the Synthesis of Compounds 7a-f by the Intramolecular Coupling Reaction A mixture of 3a (200 mg, 0.39 mmol), TBAB (153 mg, 0.47 mmol), and dry KOAc (106 mg, 1.08 mmol) was taken up in anhyd DMF (5 mL) under a nitrogen atmosphere. Palladium acetate (9 mg, 0.039 mmol) was added, and the reaction mixture was stirred at 120 ˚C for 10 h. The reaction mixture was cooled and H2O (25 mL) was added. The aqueous layer was extracted with EtOAc (3 × 30 mL), and the organic layer was washed with H2O (2 × 40 mL) followed by brine (30 mL). The organic layer was dried (Na2SO4), and the solvent was removed in vacuo. The crude product was purified by silica gel column chromatography using EtOAc-PE (1:9) to afford the product 7a. The other substrates 3b-f were similarly treated to give products 7b-f.
Compound 7a: white solid, mp 241-242 ˚C; yield 85%. IR (KBr): 1462, 1317, 1149 cm-¹. ¹H NMR (400 MHz, CDCl3): δ = 2.52 (s, 3 H), 3.86 (d, 1 H, J = 15.1 Hz), 4.11-4.19 (q, 2 H, J = 11.8 Hz), 4.45 (d, 1 H, J = 15.1 Hz), 7.34-7.37 (m, 1 H), 7.39-7.44 (m, 2 H), 7.49-7.54 (m, 3 H), 7.57-7.62 (m, 3 H), 8.25 (d, 1 H, J = 8.2 Hz). ¹³C NMR (75 MHz, CDCl3): δ = 21.5, 48.6, 49.2, 127.3, 127.4, 127.6, 128.5, 128.8, 129.0, 129.2, 129.7, 130.9, 133.7, 134.6, 136.2, 137.5, 139.5, 141.2, 144.9. HRMS: m/z calcd for C21H17NO2S: 370.0878 [M + Na]; found: 370.0878 [M + Na].

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The CCDC reference number for the CIF file of compound 7a: CCDC-693638.