Clayfen

Clay-supported ferric nitrate (Clayfen) or clay-supported cupric nitrate (Claycop), pentane, rt, 60-97% yield. ... 

Cl2, ammonium nitrate on Clayfen, Oxone on wet alumina, silver nitrate and iodine,2,3-dichloro-5,6-dicyano -1,4-benzoquinone (DDQ) in acetonitrile... 

Bakke et al. (1982) have shown how montmorillonite catalyses chlorination and nitration of toluene nitration leads to 56 % para and 41 % ortho derivative compared to approximately 40 % para and 60 % ortho derivatives in the absence of the catalyst. Montmorillonite clays have an acidity comparable to nitric acid / sulphuric acid mixtures and the use of iron-exchanged material (Clayfen) gives a remarkable improvement in the para, ortho ratio in the nitration of phenols. The nitration of estrones, which is relevant in making various estrogenic drugs, can be improved in a remarkable way by using molecular engineered layer structures (MELS), while a reduction in the cost by a factor of six has been indicated. With a Clayfen type catalyst, it seems possible to manipulate the para, ortho ratio drastically for a variety of substrates and this should be useful in the manufacture of fine chemicals. In principle, such catalysts may approach biomimetic chemistry our ability to predict selectivity is very limited. 

The direct conversion of styrene to P-nitrostyrene using clay doped with nitrate salts has been reported. Styrene and clayfen (iron nitrate on clay) or clayan (ammonium nitrate on clay) are mixed well and then heated at 100-110 °C in solid state to give P-nitrostyrene in 68% yield.551 A more simple one-pot synthesis of P-nitrostyrene from styrene has been reported P-nitrostyrene is prepared in 47% yield on treatment of styrene with CuO HBF4,12, andNaN02 in MeCN at room temperature.55b... 

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

Scheme 6.14 Transformation of thiocarbonyl derivatives of flavonoids with clayfen and clayan.

Selective 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.

Solid-state synthesis of /J-nitrostyrenes has been reported by Varma et al. in a process that uses readily available styrene and its substituted derivatives and inexpensive clay-supported nitrate salts, clayfen and clayan (Scheme 6.50) [170], In a simple experiment, admixed styrene with clayfen or clayan is irradiated in a MW oven (-100-110 °C, 3 min) or heated in an oil bath (-100-110 °C, 15 min). For clayan intermittent heating is recommended with 30-s intervals to maintain the temperature below 60-70 °C. Remarkably, the reaction proceeds only in solid state and leads to the formation of polymeric products in organic solvent. 

So lassen sich Phenole unter extrem milden Bedingungen und einfacher Aufarbeitung mit clayfen in Tetrahydrofuran, Diethylether oder Toluol regioselektiv (keine meta-Nitro-phenole) in die cntsprechenden ortho- bzw. para-Nitro-phenole uberfuhren2 ... 

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). 

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. 

Claycop was prepared in a similar manner [47] and, unlike clayfen, showed no loss of reactivity on standing in an open box. 

The dithioacetal (0.01 mol) was stirred for a few hours at room temperature with clayfen (4) (10.4 g, 11 mmol of ferric nitrate) or with claycop (12.1 g, 20 mmol of copper nitrate) in toluene, n-pentane or, preferably, dichloromethane (120ml). Evolution of nitrogen oxides occurred rapidly. Stirring was maintained until gas evolution ceased. The clay was then filtered off and washed twice with portions (50 ml) of the solvent. The resulting pale-yellow or slightly green solution was filtered through a small quantity of neutral aluminium oxide and the solvent was evaporated under vacuum. In the case of dithiane and dithiolane derivatives, this afforded the pure carbonyl compound in excellent yield. 

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. 

Keywords alcohol, clayfen, microwave irradiation, ketone, aldehyde... 

Clayfen (0.125 g) was thoroughly mixed with neat benzoin lc (0.106 g, 0.5 mmol) in the solid state using a vortex mixer and the material was placed in an alumina bath inside the microwave oven and irradiated. Upon completion of the reaction, monitored on TLC (hexane-AcOEt, 10 1, v/v), the product 2c was extracted into methylene chloride. That the effect is not purely thermal is supported by the fact that this reaction could be completed in 18 h in an oil bath at a comparable temperature of 65 °C. 

Keywords sulfide, clayfen, iron(III) nitrate, microwave irradiation, sulfoxide... 

Clayfen (1.0 g) is thoroughly mixed with the sulfide (2 mmol) in a test tube. The reaction mixture is placed in an alumina bath inside the microwave oven and is irradiated for the stipulated time. On completion of the reaction, monitored by TLC, the products were extracted with CH2C12 (3x10 mL). The solvent was removed on a rotary evaporator and the crude product, thus obtained, was charged on a silica gel column. The fractions eluted by chloroform-hexane (1 1) provided sulfone and final elution in chloroform afforded pure sulfoxide. 

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