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1.8.2 Ruthenium (Ru)
Ruthenium is a rare transition metal and its atomic number is 44. It is comparatively less reactive metal. The common oxidation states of ruthenium are +2, +3 and +4. Ruthenium at +8 oxidation state is strong oxidizing agent.
1.8.2.1 Oxidation of Alcohols
A variety of ruthenium catalysts have been used for the oxidation of alcohols to give carbonyl compounds. Among them, a quaternary ammonium salt of perruthenate (n-Pr4N)RuO4 (TPAP) is one of the most useful catalysts (Scheme 5). Other catalysts such as RuCl2(PPh3)3, RuCl3 and K2RuO4 are also effective for this functional group transformation.
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Scheme 5 |
S. V. Ley, J. Norman, Encyclopedia of Reagents for Organic Synthesis, JohnWiley and Sons, Inc., L. A. Paquette, Ed., New York, 1995, 7, 4827. |
Examples:
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H. Miyaoka, M. Yamanishi, Y. Kajiwara, Y. Yamada, J. Org. Chem. 2003, 68, 3476. |
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L. A. Paquette, H.-J. Kang, C. S. Ra, J. Am. Chem. Soc. 1992, 114, 7387. |