Claycop oxidants

The oxidation has also been accomplished with Claycop (montmorillonite K-10 clay supported cupric nitrate). The reaction of 96 to 102 was complete in 1.5-7 h with 81-93% yields. The time can be reduced to 5-10 minutes using ultrasound with minimal effect on yields. The major limitation of this protocol was the observation that only R = aryl gave product. Oxidation of 4-alkyl substituents was inert to these conditions with recovery of starting 96. 

Copper(II) nitrate immobilized on K 10 clay (claycop)-hydrogen peroxide system is an effective oxidant for a variety of substrates and provides excellent yields (Scheme 6.31) [104] wherein the maintenance of pH of the reaction mixture is not required. 

Scheme 6.31 Oxidation reactions with claycop and hydrogen peroxide.

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. 

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. 

Oxidation of 1,4-dihydropyridines. Clay-supported Fe(NO,).i or Cu(NO,) (Clay-cop) oxidizes 1,4-dihydropyridines to pyridines at 25". Reactions are generally slower with Claycop than with Clayfen, but yields are usually higher. 

Clark oxygen electrode 977, 979 Claycop, use in nitration 633 Cluster formation 929 Clustering energies, gas-phase 224 CMPO derivatives 1406 Co-antioxidants 892 Cobalt-amine complexes, as oxidation catalysts 1199, 1201, 1205, 1206, 1209, 1211... 

Copper nitrate on montmorillonite (Claycop) has been used with acetic anhydride to nitrate chlorobenzene in 100% yield, giving 13 85 orthdpara isomers.249 When an iron oxide pillared clay was used, 94% para-isomer was obtained.250 Claycop and its iron analogue have been used to oxidize a pyrazoline to a pyrazole (6.47) in 64-97% yields.251... 

I 8 Organic Synthesis Using Microwaves and Supported Reagents 8.2.4.4 Oxidations with Claycop-Hydrogen Peroxide... 

Ri = CeHs. P-NO2C6H4 Rj = H. CeHj R3 = H, Br, CN, NHz. COOH Scheme 8.48. Oxidation reactions with Claycop and hydrogen peroxide. 

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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