Sodium Hypochlorite Pentahydrate (NaOCl·5H₂O) Crystals as an Extra­ordinary Oxidant for Primary and Secondary Alcohols

Abstract

Sodium hypochlorite pentahydrate crystals containing less free sodium hydroxide and sodium chloride have been developed as an improved oxidant. Primary and secondary alcohols have been oxidized to the corresponding aldehydes and ketones with ­NaOCl·5H₂O in the presence of TEMPO/Bu₄NHSO₄. This new oxidation method does not require pH adjustment and is applicable to sterically hindered secondary alcohols.

Key words

sodium hypochlorite pentahydrate - TEMPO - 1-Me-AZADO

• References and Notes

• 1 Anelli PL, Biffi C, Montanari F, Quici S. J. Org. Chem. 1987; 52: 2559
• 2a Shibuya M, Tomizawa M, Suzuki I, Iwabuchi Y. J. Am. Chem. Soc. 2006; 128: 8412
• 2b Iwabuchi Y. J. Synth. Org. Chem. Jpn. 2008; 66: 1076
• 3 Asawa T, Tuneizumi T, Iwasaki Y. JP 4211130, 2008
• 4 Typical Experiment for the Oxidation of 2-Octanol (1) NaOCl·5H₂O crystals (2.0 g, 12.2 mmol) were added in one portion to a mixture of Bu₄NHSO₄ (0.17 g, 0.50 mmol), TEMPO (21 mg, 0.13 mmol), and 1 (1.30 g, 10.0 mmol) in CH₂Cl₂ (10 mL) at 5 °C. After 15 min, GC monitoring showed that 1 had been consumed. The reaction was stopped after 0.5 h by quenching with aq sat. Na₂SO₃ solution (20 mL). The organic layer was separated, and the aqueous layer was extracted with CH₂Cl₂ (30 mL). The combined organic layers were washed with H₂O (30 mL), dried over Na₂SO₄, and concentrated to give 2 as colorless oil (1.27 g, crude yield of 99.2%, GC analysis showed the product to be 96.8% pure). A 0.42 g portion of the crude 2 was purified by bulb-to-bulb distillation (6 kPa, 120–130 °C) to afford pure 2 (0.40 g, 95%). GC–MS analysis gave identical results to those of an authentic sample.
• 5 Oxidation of l-Menthol NaOCl·5H₂O (658.0 mg, 4 mmol) was added in one portion to a mixture of Bu₄NHSO₄ (44.5 mg, 0.131 mmol), TEMPO (3.4 mg, 0.022 mmol), and l-menthol (391.5 mg, 2.5 mmol) in CH₂Cl₂ (8 mL) at 15 °C. The mixture was stirred at 15 °C for 2.25 h, and then the reaction was quenched by treatment with sat. aq Na₂SO₃ solution (5 mL). The aqueous layer was extracted with CH₂Cl₂ (3 × 10 mL). The combined organic layers were washed with sat. brine, dried over anhydrous Na₂SO₄, and concentrated to give l-menthone as a colorless oil (475.7 mg), which was purified by column chromatography on silica gel to give pure l-menthone (355.3 mg, 92%). [α]_D ²⁵ –28.1 (c 0.0156, EtOH) {lit.⁶ [α]_D –28.6}. ¹H NMR (400 MHz, CDCl₃): δ = 2.35 (ddd, J = 13.1, 3.6, 2.3 Hz, 1 H), 2.18–1.80 (m, 6 H), 1.43–1.29 (m, 2 H), 1.01 (d, J = 6.4 Hz, 3 H), 0.91 (d, J = 6.8 Hz, 3 H), 0.85 (d, J = 6.8 Hz, 3 H). See ref. 7.
• 6 Timshina AV. Russian J. Org. Chem. 2008; 44: 1043
• 7 Iwabuchi Y, Hayashi M. WO 2012008228, 2012