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Environmentally-Friendly Oxidation
In recent years, organic synthesis has improved to the point of being environmentally-friendly. Many excellent methodologies have been devised for green chemistry and environmentally-friendly manufacturing. Oxidation reactions employing atmospheric oxygen or molecular oxygen as an oxidant is one of the methodologies of green chemistry. The earth is filled with air, and about 20% of air is oxygen. If oxygen could be utilized as the oxidant, this would provide a method that is not only economically prudent, but also environmentally clean. However, the oxidation capability of atmospheric oxygen and molecular oxygen is not powerful enough when used alone. Therefore, there is much active R&D underway to make improvements in the oxidation capability with the presence of transition metal complex catalysts and radical producing catalysts.1)
For example, Markó and co-workers have reported that tetrapropylammonium perruthenate (TPAP) can be used for the oxidation of alcohols to aldehydes and ketones using molecular oxygen as the oxidant.2)
Similarly, Uemura and co-workers have demonstrated that palladium(II) diacetate is also a catalyst for the same type of oxidations.3)
Katsuki and co-workers reported the oxidation method of alcohols using (nitrosyl) Ru-Salen complex as a catalyst.4) This catalyst is activated by photo-irradiation and can be used to oxidize primary alcohols to aldehydes selectively.
Fukuzumi and co-workers reported the oxygenation using 9-aromatic substituted acridinium derivatives as effective electron-transfer photocatalysts.5)
Ishii and his group have reported a catalytic carbon radical formation method using N-hydroxyphthalimide (NHPI).6) In this method, the hydrogen atom of the hydroxyimino group in NHPI is pulled off by molecular oxygen, thereby producing a phthalimide N-oxyl (PINO) radical. The PINO radical then pulls hydrogen atoms from carbon-hydrogen bonds such as alkanes and alcohols to furnish the corresponding carbon radicals. The resulting carbon radicals readily react with diff erent types of molecules, thereby producing oxygen-containing compounds such as carboxylic acids under an oxygen atmosphere.
A porous metal-organic framework (MOF) (porous coordination polymers (PCP)) pre-ELM-11 is also utilized as a catalyst in organic synthesis for molecular oxygen-derived oxidation.7)
For example, Markó and co-workers have reported that tetrapropylammonium perruthenate (TPAP) can be used for the oxidation of alcohols to aldehydes and ketones using molecular oxygen as the oxidant.2)
Similarly, Uemura and co-workers have demonstrated that palladium(II) diacetate is also a catalyst for the same type of oxidations.3)
Katsuki and co-workers reported the oxidation method of alcohols using (nitrosyl) Ru-Salen complex as a catalyst.4) This catalyst is activated by photo-irradiation and can be used to oxidize primary alcohols to aldehydes selectively.
Fukuzumi and co-workers reported the oxygenation using 9-aromatic substituted acridinium derivatives as effective electron-transfer photocatalysts.5)
Ishii and his group have reported a catalytic carbon radical formation method using N-hydroxyphthalimide (NHPI).6) In this method, the hydrogen atom of the hydroxyimino group in NHPI is pulled off by molecular oxygen, thereby producing a phthalimide N-oxyl (PINO) radical. The PINO radical then pulls hydrogen atoms from carbon-hydrogen bonds such as alkanes and alcohols to furnish the corresponding carbon radicals. The resulting carbon radicals readily react with diff erent types of molecules, thereby producing oxygen-containing compounds such as carboxylic acids under an oxygen atmosphere.
A porous metal-organic framework (MOF) (porous coordination polymers (PCP)) pre-ELM-11 is also utilized as a catalyst in organic synthesis for molecular oxygen-derived oxidation.7)
References
- 1)a) Review：C. N. Cornell, M. S. Sigman, in Activation of Small Molecules: Organometallic and Bioinorganic Perspectives, ed. by W. B. Tolman, Wiley-VCH, Weinheim, 2006, pp.159-186.
- b) T. Punniyamurthy, S. Velusamy, J. Iqbal, Chem. Rev. 2005, 105, 2329.
- c) I. W. C. E. Arends, R. A. Sheldon, in Modern Oxidation Methods, ed. by J.-E. Bäckwall, Wiley-VCH, Weinheim, 2004, pp.83-118.
- b) T. Punniyamurthy, S. Velusamy, J. Iqbal, Chem. Rev. 2005, 105, 2329.
- 2)I. E. Marko', P. R. Giles, M. Tsukazaki, I. Chelle'-Regnaut, C. J. Urch, S. M. Brown, J. Am. Chem. Soc. 1997, 119, 12661.
- 3)T. Nishimura, T. Onoue, K. Ohe, S. Uemura, Tetrahedron Lett. 1998, 39, 6011.
- 4)a) A. Miyata, M. Murakami, R. Irie, T. Katsuki, Tetrahedron Lett. 2001, 42, 7067.
- 5)a) S. Fukuzumi, H. Kotani, K. Ohkubo, S. Ogo, N. V. Tkachenko, H. Lemmetyinen, J. Am. Chem. Soc. 2004, 126, 1600.
- 6)a) Y. Ishii, T. Iwahama, S. Sakaguchi, K. Nakayama, Y. Nishiyama, J. Org. Chem. 1996, 61, 4520.
- 7)a) T. Arai, H. Takasugi, T. Sato, H. Noguchi, H. Kanoh, K. Kaneko, A. Yanagisawa, Chem. Lett. 2005, 34, 1590.