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Synlett 2006(7): 1100-1104  
DOI: 10.1055/s-2006-939692
LETTER
© Georg Thieme Verlag Stuttgart · New York

Selenoxides as Catalysts for Epoxidation and Baeyer-Villiger Oxidation with Hydrogen Peroxide

Margaret A. Goodman, Michael R. Detty*
Department of Chemistry, University at Buffalo, The State University of New York, 627 Natural Sciences Complex, North Campus, Buffalo, New York 14260, USA
Fax: +1(716)6456963; e-Mail: mdetty@buffalo.edu;
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Publication History

Received 14 February 2006
Publication Date:
24 April 2006 (online)

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Abstract

Aryl benzyl selenoxides are catalysts for the epoxidation of various olefinic substrates and the Baeyer-Villiger oxidation of aldehydes and ketones with H2O2 in CH2Cl2 at 2.5 mol% catalyst. Benzyl 3,5-bis(trifluoromethyl)phenyl selenoxide (4) was the most effective catalyst while 2-(dimethylamino)phenyl benzyl selen­oxide was the least. Mono-, di-, and trisubstituted alkenes were ­epoxidized and adamantanone, cyclohexanone, and 3,4,5-trimethoxybenzaldehyde underwent Baeyer-Villiger oxidation using 4 and H2O2. Competition studies showed that epoxidation reactions were faster than Baeyer-Villiger oxidations although the selectivity varied only from 1.3:1 to 4.6:1.

Key words

catalysis - epoxidations - esters - oxidations - selenoxide

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Hydrogen peroxide (8.8 M, 0.225 mL, 2.0 mmol) was added to 1.0 mmol of cis-cyclooctene and 0.05 mmol of selenoxide in 2 mL of CH2Cl2. The progress of the reaction at 296 ± 1 K was monitored by determining the cis-cylooctene:6 ratio using 1H NMR spectroscopy from aliquots withdrawn from the reaction mixtures.

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Selenoxide 4 (0.05 mmol, 2.5 mol%), alkene (2 mmol) or carbonyl compound (2 mmol), and H2O2 (8.8 M, 0.45 mL, 4.0 mmol) were stirred in CH2Cl2 (2 mL) at 296 K. The progress of reaction was followed by 1H NMR spectroscopy of aliquots withdrawn at various time points. Upon completion, reaction mixtures were poured into 10 mL of H2O and products were extracted with CH2Cl2. Products were purified via chromatography of SiO2 eluted with CH2Cl2.

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Compound 6: 1H NMR (400 MHz, CDCl3): δ = 2.91 (d, 2 H, J = 8 Hz), 2.15 (d, 2 H, J = 11.6 Hz), 1.27-1.60 (m, 10 H). 13C NMR (125 MHz, CDCl3): δ = 55.35, 26.58, 26.37, 25.59.
Compound 7: 1H NMR (400 MHz, CDCl3): δ = 7.24-7.34 (m, 5 H), 3.57 (s, 1 H), 3.04 (q, 1 H, J = 5.0 Hz), 1.44 (d, 3 H, J = 5.0 Hz). 13C NMR (125 MHz, CDCl3): δ = 137.60, 128.30, 127.90, 125.40, 59.42, 58.93, 17.80.
Compound 8: 1H NMR (500 MHz, CDCl3): δ = 2.75 (t, 1 H, J = 7.5 Hz), 1.24-1.52 (m, 12 H), 0.91 (t, 3 H, J = 6.5 Hz). 13C NMR (125 MHz, CDCl3): δ = 64.58, 58.48, 28.42, 28.25, 24.61, 22.34, 18.42, 13.78.
Compound 9: 1H NMR (500 MHz, CDCl3): δ = 1.84-1.91 (m, 2 H), 1.63-1.69 (m, 2 H), 1.38-1.44 (m, 2 H), 1.30 (s, 3 H), 1.16-1.26 (m, 2 H). 13C NMR (125 MHz, CDCl3): δ = 59.15, 32.57, 29.40, 24.26, 23.52, 19.56, 19.18.
Compound 10: 1H NMR (500 MHz, CDCl3): δ = 2.66 (t, 2 H, J = 5.0 Hz), 1.35-1.54 (m, 12 H), 0.93 (t, 6 H, J = 7.0 Hz). 13C NMR (125 MHz, CDCl3): δ = 58.53, 31.78, 28.12, 22.46, 13.92.
Compound 13: 1H NMR (400 MHz, CDCl3): δ = 8.17 (s, 1 H), 6.28 (s, 2 H), 3.71 (s, 9 H). 13C NMR (125 MHz, CDCl3): δ = 159.20, 153.20, 145.60, 135.70, 98.32, 60.36, 55.72.
Compound 14: 1H NMR (400 MHz, CDCl3): δ = 4.25 (t, 2 H, J = 4.6 Hz), 2.66 (t, 2 H, J = 5.2 Hz), 1.59-1.66 (m, 4 H), 1.40-1.50 (m, 2 H). 13C NMR (75 MHz, CDCl3): δ = 175.90, 69.22, 34.66, 29.18, 27.42, 25.40.

Compound 15: 1H NMR (400 MHz, CDCl3): δ = 4.40 (t, 1 H, J = 3.0 Hz), 2.97 (t, 1 H, J = 5.4 Hz), 1.67-2.04 (m, 12 H). 13C NMR (75 MHz, CDCl3): δ = 178.3, 72.61, 40.71, 35.15, 33.09, 30.35, 25.23.

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H2O2 (8.8 M, 0.225 mL, 2.0 mmol) was added to 1.0 mmol of 12 and 0.05 mmol of selenoxide (5.0 mol% relative to 12) in 2 mL CH2Cl2.

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H2O2 (8.8 M, 0.225 mL, 2.0 mmol) or MCPBA (2.0 mmol, no catalyst), 2.0 mmol of 1-methylcyclohexene, 2.0 mmol of aldehyde 12 or cyclohexanone, and 0.05 mmol of selenoxide were stirred in 2 mL of CDCl3. The reactions were stirred for 24 h and the product mixtures were examined directly by 1H NMR spectroscopy. In each reaction, the product/starting material ratio was approximately 1:1. Ratios are the average of duplicate runs.