Synlett 2010(9): 1407-1411  
DOI: 10.1055/s-0029-1219825
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Molecular Iodine Mediated Intramolecular Cyclization: An Efficient Method for the Synthesis of Benzoxepine Derivatives

K. C. Majumdar*, Biswajit Sinha, Inul Ansary, Santanu Chakravorty
Department of Chemistry, University of Kalyani, Kalyani 741235, West Bengal, India
e-Mail: kcm_ku@yahoo.co.in ;
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Publikationsverlauf

Received 15 March 2010
Publikationsdatum:
13. April 2010 (online)

Abstract

A simple, efficient and cost effective method for a divergent synthesis of benzoxepine derivatives using a hitherto unreported, highly regioselective, tandem iodocyclization procedure is described.

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Compound 4a: A mixture of compound 3a (100 mg, 0.39 mmol), I2 (100 mg, 0.39 mmol), and anhyd NaHCO3 (33 mg, 0.39 mmol) was stirred in anhyd MeCN (10 mL) at r.t. for 6 h. Then CH2Cl2 (50 mL) was added to the reaction mixture and the organic phase was taken and washed successively with 10% aq sodium thiosulfate (20 mL), H2O (20 mL), brine (20 mL) and dried (Na2SO4). The solvent was removed under reduced pressure and the crude product thus obtained was purified by silica gel (230-400 mesh) column chroma-tography (petroleum ether-EtOAc, 97:3) to give the colorless gummy product 4a. Yield: 55%; IR (neat): 1710, 2927, 3066 cm; ¹H NMR (400 MHz, CDCl3): δ = 1.29 (s, 9 H), 2.21 (s, 3 H), 3.42 (d, J = 1.6 Hz, 1 H), 4.52 (d, J = 1.6 Hz, 1 H), 4.69 (s, 2 H), 6.78 (d, J = 8.8 Hz, 1 H), 7.18-7.20 (m, 2 H), 7.30 (dd, J = 8.4, 2.4 Hz, 1 H); ¹³C NMR (100 MHz, CDCl3): δ = 24.8, 31.4, 34.3, 54.3, 63.2, 74.4, 82.1, 98.5, 111.7, 122.1, 123.6, 126.3, 144.8, 153.5, 204.6. HRMS: m/z [M + K]+ calcd for C17H20I2O2: 548.9190; found: 548.9190.