Synlett 2007(20): 3198-3200  
DOI: 10.1055/s-2007-992376
LETTER
© Georg Thieme Verlag Stuttgart · New York

Dimethyldioxirane Oxidation of 2-Silyloxypyrroles: An Efficient Regiocontrolled Synthesis of 5-Hydroxy-3-pyrrolin-2-ones

John Boukouvalas*, Yufang Xiao, Yun-Xing Cheng, Richard P. Loach
Département de Chimie, Université Laval, Quebec City, QC, G1K 7P4, Canada
Fax: +1(418)6567916; e-Mail: john.boukouvalas@chm.ulaval.ca;
Further Information

Publication History

Received 16 August 2007
Publication Date:
21 November 2007 (online)

Abstract

A new method for the synthesis of 5-hydroxy-3-pyrrolin-2-ones is reported. Conversion of N-Boc-3-pyrrolin-2-ones into 2-triisopropylsilyloxypyrroles and ensuing oxidation with dimethyldioxirane provides the corresponding N-Boc-5-hydroxy-3-pyrrolin-2-ones in high yields.

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Typical Procedure: To a solution of 4a (732 mg, 4.0 mmol) in anhyd CH2Cl2 (5 mL) were added 2,6-lutidine (1.290 g, 12.0 mmol) and TIPSOTf (1.232 g, 4.54 mmol) under nitrogen at r.t. After stirring for 30 min, the solvent was evaporated and the residue was purified by flash chromatog-raphy on silica gel (hexanes-EtOAc, 95:5) to give 5a (1.263 g, 93%) as a colorless oil. For smaller-scale reactions, purification was carried out by chromatography on basic silica gel.11c
Data for 5a: 1H NMR (300 MHz, CDCl3): δ = 1.10 (d, J = 7.2 Hz, 18 H), 1.25 (hept, J = 7.2 Hz, 3 H), 1.54 (s, 9 H), 5.21 (dd, J = 1.7, 3.6 Hz, 1 H), 5.86 (dd, J = 1.7, 3.6 Hz, 1 H), 6.67 (t, J = 3.6 Hz, 1 H). 13C NMR (75 MHz, CDCl3): δ = 12.4, 17.9, 27.8, 82.4, 91.7, 107.6, 112.5, 143.6, 148.1. HRMS: m/z calcd for C18H33NO3Si: 339.2230; found: 339.2233.

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Typical Procedure: To a solution of 5a (339 mg, 1.0 mmol) in anhyd CH2Cl2 (5 mL) at -78 °C was added dropwise a solution of DMDO (0.055 M in acetone, 20 mL, 1.1 equiv) and the reaction mixture was stirred for 1 h at -78 °C. The volatiles were evaporated and the residue was dissolved in acetone (10 mL). After addition of H2O (7 mL) and Amberlyst-15 (ca. 100 mg), the reaction mixture was stirred for 1 h at r.t. The mixture was filtered, the filtrate was extracted with Et2O (3 × 10 mL) and the combined organic layers were dried over anhyd MgSO4. After evaporation of the volatiles, the residue was purified by flash chromatog-raphy on silica gel (hexanes-EtOAc, 7:3) to furnish 6a (187 mg, 94%) as a white solid (mp 100-101 °C). 1H NMR (300 MHz, CDCl3): δ = 1.54 (s, 9 H), 4.32 (br d, J = 4.8 Hz, 1 H), 5.96 (br m, 1 H), 6.07 (d, J = 6.4 Hz, 1 H), 7.02 (dd, J = 4.8, 6.4 Hz, 1 H). 13C NMR (75 MHz, CDCl3): δ = 28.0, 82.0, 83.8, 128.3, 146.3, 149.9, 166.4. Anal. Calcd for C9H13NO4: C, 54.26; H, 6.58; N, 7.03. Found: C, 54.62; H, 6.53; N, 7.00.

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Data for 6f: mp 62-64 °C. 1H NMR (300 MHz, CDCl3): δ = 1.53 (s, 9 H), 1.54 (br s, 3 H), 1.63 (br s, 3 H), 2.74 (dd, J = 6.8, 14.5 Hz, 1 H), 2.90 (dd, J = 8.3, 14.5 Hz, 1 H), 4.42 (br s, 1 H), 4.86 (dd, J = 6.8, 8.3 Hz, 1 H), 6.03 (d, J = 6.0 Hz, 1 H), 7.00 (d, J = 6.0 Hz, 1 H). 13C NMR (75 MHz, CDCl3): δ = 17.8, 25.7, 27.8, 36.5, 83.7, 92.6, 116.2, 126.6, 136.4, 145.3, 150.3 (2 × C), 166.6. Anal. Calcd for C14H21NO4: C, 62.90; H, 7.92; N, 5.24. Found: C, 62.84; H, 7.87; N, 5.16.

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Data for 8: colorless oil. 1H NMR (300 MHz, CDCl3): δ = 1.27 (t, J = 7.0 Hz, 3 H), 1.45 (s, 9 H), 2.00 (s, 3 H), 4.20 (q, J = 7.0 Hz, 2 H), 6.78 (d, J = 11.7 Hz, 1 H), 6.91 (dd, J = 11.7, 11.7 Hz, 1 H), 7.69 (br s, 1 H), 8.11 (d, J = 11.7 Hz, 1 H). 13C NMR (75 MHz, CDCl3): δ = 12.6, 14.1, 27.8, 60.8, 82.6, 123.6, 132.3, 135.3, 137.3, 150.3, 165.5, 167.8. HRMS: m/z [M + H+] calcd for C14H22NO5: 284.1498; found: 284.1502.