Iron nitrate clay-supported

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]. 

Reaction of 6-formyl-5,7,8,9-tetrahydro-ll//-pyrido[2,l-b]quinazolin-ll-one (135) with Clayfen [K-10 montmorillonite clay supported iron(III) nitrate] in boiling methylene chloride for 2.5 h gave a mixture of 6,6-dinitro-6,7,8,9-tetrahydro (136) and 6-formyl-8,9-dihydro-ll//-pyrido[2,l-6]-quinazolin-ll-ones (137) (90JOC6198). 

When nitration of phenols is performed with clay-supported iron(III) nitrate at room temperature, exclusively o- and p-nitrophenols are formed. No meta nitration occurs. With mera-substituted phenols, one of the ortho positions is favored with respect to the other (Scheme 8). ... 

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%). 

A rapid MW oxidation protocol for the oxidation of alcohols to carbonyl compounds has been reported by Vanna et al. using montmorillonite KIO clay-supported iron(III) nitrate (clayfen) (Scheme 7). The simple solvent-free experimental procedure involves mixing of neat substrates... 

A. Cornells and P. Laszlo, Clay-Supported Copper (II) and Iron (III) Nitrates Novel Multi-Purpose Reagents for Organic Synthesis, Synthesis, 1985, 909. 

Cornells, A. and Laszlo, P. 1985. Clay-supported copper(II) and iron(III) nitrates Novel multipurpose reagents for organic synthesis. Synthesis. 1985(10) 909-918. 

Pyridinium chlorochromate adsorbed on alumina offers advantages over PCC alone in the oxidation of acid-sensitive molecules.For example, citronellol is oxidized to citronellal in 90% yield by the supported reagent, whereas PCC gives pulegone. Clay-supported iron(lll) nitrate is reported to oxidize secondary alcohols in good yield."... 

Scheme 4.3 Oxidation of alcohols by iron(lll) nitrate supported on clay (clayfen).

Monosubstituted hydrazines and hydrazides are converted into azides by a variety of nitrosating agents. The mildest reagent appears to be dinitrogen tetroxide, which can be used below 0 C in acetonitrile to convert benzoylhydrazine, p-toluenesulfonylhydrazine and 4-nitrobenzoylhydrazine, among others, into the corresponding azides in high yield. Another mild method involves the use of iron(lll) nitrate supported on clay. These reactions probably proceed by way of transient N-nitroso compounds (Scheme 19). 

Deprotection of trimethylsilyl ether has also been accomplished (88-100%) on KIO clay [47] or oxidative cleavage (70-95%) in the presence of clay and iron(III) nitrate [48]. Another oxidative deprotection of trimethylsilyl ethers using supported potassium ferrate, K2pe04 and MW has been reported [49]. 

Activation. KIO clay may be used crude, or after simple thermal activation. Its acidic properties are boosted by cation exchange (i.e. by iron(III) or zinc(II) ) or by deposition of Lewis acids, such as zinc(II) or iron(III) chloride (i.e. clayzic and clayfec ). In addition, KIO is a support of choice for reacting salts, for example nitrates of thallium(III), iron(III) ( clayfen ), or copper(II) ( claycop ). Multifarious modifications (with a commensurate number of brand names) result in a surprisingly wide range of applications coupled with the frequent imprecise identification of the clay (KIO or one of its possible substitutes mentioned above), they turn KIO into a Proteus impossible to grab and to trace exhaustively in the literature. 

---