Synlett 2013; 24(11): 1438-1442
DOI: 10.1055/s-0033-1338856
letter
© Georg Thieme Verlag Stuttgart · New York

Convenient and Eco-Friendly Method for the Conversion of Benzylic Alcohols into Aldehydes, Ketones, and Carboxylic Acids Using NaOCl without any Additives in 1,2-Dimethoxyethane

Naohiro Fukuda
Chemical Development Laboratories, CMC Center, Takeda Pharmaceutical Company Limited, 2-17-85, Jusohonmachi, Yodogawa-ku, Osaka, 532-8686, Japan   Fax: +81(6)63006251   Email: tomomi.ikemoto@takeda.com
,
Takeshi Kajiwara
Chemical Development Laboratories, CMC Center, Takeda Pharmaceutical Company Limited, 2-17-85, Jusohonmachi, Yodogawa-ku, Osaka, 532-8686, Japan   Fax: +81(6)63006251   Email: tomomi.ikemoto@takeda.com
,
Tomoaki Katou
Chemical Development Laboratories, CMC Center, Takeda Pharmaceutical Company Limited, 2-17-85, Jusohonmachi, Yodogawa-ku, Osaka, 532-8686, Japan   Fax: +81(6)63006251   Email: tomomi.ikemoto@takeda.com
,
Keisuke Majima
Chemical Development Laboratories, CMC Center, Takeda Pharmaceutical Company Limited, 2-17-85, Jusohonmachi, Yodogawa-ku, Osaka, 532-8686, Japan   Fax: +81(6)63006251   Email: tomomi.ikemoto@takeda.com
,
Tomomi Ikemoto*
Chemical Development Laboratories, CMC Center, Takeda Pharmaceutical Company Limited, 2-17-85, Jusohonmachi, Yodogawa-ku, Osaka, 532-8686, Japan   Fax: +81(6)63006251   Email: tomomi.ikemoto@takeda.com
› Author Affiliations
Further Information

Publication History

Received: 28 March 2013

Accepted after revision: 25 April 2013

Publication Date:
10 June 2013 (online)


Abstract

Oxidation of benzylic alcohols to aldehydes, ketones, and carboxylic acids using NaOCl in 1,2-dimethoxyethane without any additives has been developed. 4-Methylbenzyl alcohol and diphenyl methanol were converted into the corresponding aldehyde and ketone in 97% and 92% yield, respectively. Furthermore, 4-­nitrobenzyl alcohol was directly converted into the corresponding carboxylic acid in 99% yield.

 
  • References and Notes

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  • 13 Morton D, Cole-Hamilton DJ. J. Chem. Soc., Chem. Commun. 1987; 248
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  • 17 Stevens RV, Chapman KT. Tetrahedron Lett. 1982; 23: 4647
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  • 21 General Procedure A mixture of 1a (10 g, 54.3 mmol) and DME (100 mL) was stirring at 20–30 °C, and 10% (w/w) NaOCl (72.7 g, 97.7 mmol; Wako Pure Chemical Industries, Ltd.) was gradually added to the mixture at 20–25 °C. The reaction was continued for 4 h while keeping the temperature at 20–25 °C. After the reaction was completed, 5% aq Na2S2O3 (50 mL) and toluene (50 mL) were added to the reaction mixture, and the mixture was stirred for 20 min. The organic layer was collected, washed with 1 N NaOH (50 mL) followed by H2O (50 mL), and concentrated. To the concentrate was added i-PrOH (50 mL), and the mixture was heated to 35–45 °C. H2O (25 mL) and seed crystals of 2a (10 mg) were added to the mixture to initiate crystallization. Additional H2O (125 mL) was added dropwise for over 1 h, and then the mixture was stirred at 35–45 °C, 20–25 °C, and 0–10 °C, for over 1 h at each. The resultant crystals were collected by filtration, washed with H2O (50 mL), and dried under reduced pressure at 50 °C to provide 2a as white crystals (8.93 g, 90.3%). 1H NMR (500 MHz, CDCl3): δ = 7.35–7.50 (m, 3 H), 7.58–7.64 (m, 2 H), 7.69–7.75 (m, 2 H), 7.88–7.95 (m, 2 H), 10.03 (s, 1 H). 13C NMR (125 MHz, CDCl3): δ = 127.4, 127.7, 128.5, 129.0, 130.3, 135.3, 139.7, 147.2, 191.9.
  • 22 Conditions: 2.3 or 2.4 equiv of NaOCl were used for these reactions because the oxidations of some substrates with 1.8 equiv of NaOCl required longer reaction time.
  • 23 The Procedure for Oxidation to Carboxylic Acid To a solution of 1f (1.00 g, 6.53 mmol) in DME (20 mL) was added 10% aq NaOCl (11.67 g, 15.67 mmol) at r.t. The mixture was stirred at r.t. for 4 h before adding 10% Na2SO3 (10 mL). The mixture was adjusted to pH 3.5 with 6 M HCl and extracted with EtOAc (20 mL). The aqueous layer was extracted again with EtOAc (10 mL), and the combined organic extract was washed with H2O (10 mL) before being concentrated under reduced pressure. EtOAc (4 mL) and n-heptane (4 mL) were added at r.t., then the solids were collected by filtration and washed with n-heptane (3 mL) to afford 3f (1.01 g, 93%). 1H NMR (500 MHz, DMSO-d 6): δ = 8.18 (d, J = 8.8 Hz, 2 H), 8.33 (d, J = 8.8 Hz, 2 H), 13.68 (br s, 1 H). 13C NMR (125 MHz, DMSO-d 6): δ = 123.6, 130.6, 136.4, 150.0, 165.7.
  • 24 The Procedure for Oxidation of 1o A mixture of 1o (500 mg, 2.74 mmol) and DME (10 mL) was stirred at r.t. and then 10% aq NaOCl (4.90 g, 6.59 mmol) was gradually added to the mixture. Stirring of the mixture was continued at r.t. for 4 h. Then 10% aq Na2SO3 (5 mL) was added to the mixture, and stirring was continued for 5 min. EtOAc (20 mL) and H2O (10 mL) were added to the mixture. Quantitative analysis of the organic layer by HPLC showed the yield of 2o to be 100%, and then the organic layer was concentrated, and the residue was purified by column chromatography on silica gel using n-hexane–EtOAc (10:1) as eluent to provide the desired ketone 2o (492 mg, 99%). 1H NMR (500 MHz, CDCl3): δ = 7.17–7.27 (m, 2 H), 7.35–7.47 (m, 4 H), 7.54–7.63 (m, 2 H). 13C NMR (125 MHz, CDCl3): δ = 120.3, 124.2, 129.0, 134.1, 134.6, 144.3, 193.7.