Clayfen reagent

In a small beaker oxime (10 mmol) and freshly prepared clayfen reagent (6.6 mmol of iron(III) nitrate) were mixed together to make an intimate mixture. The beaker was placed in a household microwave oven for the specified time. The residue was washed with CH2C12 (10 mL) and filtered. The filtrate was evaporated to dryness to afford the corresponding carbonyl compound. 

Laszlo introduced an oxidative cleavage of dithioacetals by their clayfen (4) and claycop reagents under mild conditions with excellent yields [46, 47]. These reagents are convenient sources of the nitrosonium ion NO+, a soft reactive Lewis acid species, well adapted for attack of the soft sulfur atom. 

Ferric nitrate/KlO Bentonite (Clayfen). )C=S — )C=0.1 This transformation is possible with this reagent, but yields are high (60-100%) only with diaryl ketones. 

Ferric nitrate/KlO bentonite clay (Clayfen). The reagent is prepared by addition of the clay to Fe(N03)3 in acetone followed by evaporation of the solvent at temperatures below 50°. Warning An unstable reagent is formed at higher temperatures.1... 

Although it is possible to obtain the acetone solvate of anhydrous iron(III) nitrate, this oil decomposes in a vigorous exothermic reaction. However, it is possible to stabilize the oil by impregnation on the KIO acidic montmorillonite. The name clayfen has been given to the resulting reagent. ... 

The scope of the Ritter reaction can also be extended by avoiding strong acid as the carbenium ion initiator. In at least one case it is possible to omit this reagent entirely because of the facility of 5 1 reaction. Thus, reflux of r-butyl bromide in acetonitrile or propionitrile for 24 h led to formation of A -f-butylamide products. Less commonly used initiators have included cation exchange resins and clayfen. In this latter case, the clay-supported iron(III) nitrate is believed to give rise to nitrosonium ions, which react with the alkyl halide substrate to produce a carbenium ion. Yields of amide from this technique are generally modest (21-35%). 

Clays or modified clays have also been used to prepare supported reagents, although at present only on a laboratory scale [16,24,25,34,55]. For example, the nitration of phenols is normally performed with mixtures of nitric and sulfuric acids, with only modest overall yields (ca 60 %) and formation of the meta isomer and by-products of polynitration, together with the normal ortho- and para-substituted derivatives. The clay-supported Fe(N03)3 (Clayfen) not only improves the overall yield in the nitration of phenol (up to ca 90 %), but is also very active... 

A rapid microwave oxidation protocol for the oxidation of alcohol to carbonyl compound has been reported by Varma (2001). Different types of oxidizing reagents have been used with microwave irradiations. Alcohols were converted into corresponding carbonyl compounds in the presence of montmorillonite KIO clay-sup-ported iron (111) nitrate (Clayfen), Oxone-alumina, IBD-alumina, 35% MnO doped silica, CrO,-alumina or CuSO-alumina under microwave irradiation and solvent-free conditions in few minutes (0.25-3.5 min). 

The first part of this article specifically deals with representative laboratoiy applications to fine chemistry of clearly identified, unaltered KIO, excluding its modified forms (cation-exchanged, doped by salt deposition, pillared, etc.) and industrial uses in bulk. This illustrative medley shows the prowess of KIO as a strong Brpnsted acidic catalyst. The second part deals with cation-exchanged (mainly Fe ") montmorillonite. Clayfen and claycop, versatile stoichiometric reagents obtained by metal nitrate deposition on KIO, are used in oxidation and nitration reactions. They are treated under Iron(III) Nitrate-KlO Montrrufrillonite Clay and Copperfll) Nitrate-KlO Bentonite Clay. 

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