Selective Solvent-free Oxidation with Clayfen

3 Selective Solvent-free Oxidation with Clayfen 

A ground mixture of iron(III) nitrate and HZSM-5 zeolite, termed zeofen , has also been used both, in dichloromethane solution and in solid state under MW irradiation conditions [101]. It has been suggested that the zeolite aids the reproducibility of the reaction but any other aluminosilicate support would probably be equally effective. Recent studies point out attractive alternatives that do not employ any of the solid supports in such oxidations with nitrate salts [102]. 

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Selective and Solvent-Free Oxidation with Clayfen... 

A facile method for the oxidation of alcohols to carbonyl compounds has been reported by Varma et al. using montmorillonite K 10 clay-supported iron(III) nitrate (clayfen) under solvent-free conditions [100], This MW-expedited reaction presumably proceeds via the intermediacy of nitrosonium ions. Interestingly, no carboxylic acids are formed in the oxidation of primary alcohols. The simple solvent-free experimental procedure involves mixing of neat substrates with clayfen and a brief exposure of the reaction mixture to irradiation in a MW oven for 15-60 s. This rapid, ma-nipulatively simple, inexpensive and selective procedure avoids the use of excess solvents and toxic oxidants (Scheme 6.30) [100]. Solid state use of clayfen has afforded higher yields and the amounts used are half of that used by Laszlo et al. [17,19]. 

Scheme 6.30 Solvent-free selective oxidation of alcohols with clayfen.

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