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TEMPO/HCl/NaNO 2 Catalyst: A Transition‐Metal‐Free Approach to Efficient Aerobic Oxidation of Alcohols to Aldehydes and Ketones Under Mild Conditions
Author(s) -
Wang Xinliang,
Liu Renhua,
Jin Yu,
Liang Xinmiao
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200701818
Subject(s) - alcohol oxidation , catalysis , chemistry , alcohol , mass spectrometry , redox , catalytic oxidation , hydrochloric acid , electrospray ionization , transition metal , radical , molecular oxygen , photochemistry , organic chemistry , inorganic chemistry , chromatography
Hydrochloric acid, a very inexpensive and readily available inorganic acid, has been found to cooperate exquisitely with NaNO 2 /TEMPO in catalyzing the molecular‐oxygen‐driven oxidation of a broad range of alcohol substrates to the corresponding aldehydes and ketones. This transition‐metal‐free catalytic oxidative conversion is novel and represents an interesting alternative route to the corresponding carbonyl compounds to the metal‐catalyzed aerobic oxidation of alcohols. The reaction is highly selective with respect to the desired product when carried out at room temperature in air at atmospheric pressure. Notably, the use of very inexpensive NaNO 2 and HCl in combination with TEMPO for this highly selective aerobic oxidation of alcohols in air at ambient temperature makes the reaction operationally and economically very attractive. The results of mechanistic studies, performed with the aid of electrospray ionization mass spectrometry (ESI‐MS), are presented and discussed. TEMPO, TEMPOH, and TEMPO + were observed in the redox cycle by means of ESI‐MS. On the basis of these observations, a mechanism is proposed that may provide an insight into the newly developed aerobic alcohol oxidation.