Expeditious oxidation of alcohols to carbonyl compounds using iron(III) nitrate

An efficient and solvent-free protocol for the oxidation of alcohols to corresponding carbonyl compounds using iron(III) nitrate nonahydrate has been developed. ! 2007 Elsevier Ltd. All rights reserved. The oxidation of alcohols to the corresponding carbonyl compounds is one of the most important transformations in organic synthesis. There are numerous methods available in the literature and the development of new selective oxidative protocols is still considered a challenge. This void was filled, in part, by using a set of clay-supported metal nitrate salts such as iron(III) nitrate supported on clay, clayfen, and on zeolites, zeofen, which are known for various applications including oxidation of alcohols. The main drawbacks of clayfen and other related solid supported metal nitrate salts in oxidative transformations are the use of large excess of solvents, reflux reaction conditions, longer reaction times, high ratio of reagent to substrate, and the generation of solid waste (40–50 g/mol). Varma and Dahiya were able to eliminate solvents from these oxidations by employing microwave heating which also helped to reduce the reaction time from hours to seconds. In our continued quest for the development of environmentally friendly alternatives, we sought to develop an improved methodology which minimizes the use of any solvent or support and requires a low catalyst/substrate ratio. Herein, we describe this facile approach for the oxidation of secondary aliphatic, alicyclic, and benzylic alcohols (Scheme 1). Numerous reports have been described for the enhanced oxidative potential of metal nitrates on various mineral oxide supports. We decided to investigate the proper control reactions in the absence of any solvent or support. In order to render these oxidations economically more viable and simpler, we focused our attention on iron(III) nitrate nonahydrate which is abundant, cheap, and relatively nontoxic. Benzyl alcohol was used as a model compound to evaluate the oxidative potential of