Claycop reagent

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 reported improvement in yields and selectivities in both mono- and poly-nitration of aromatic compounds using Claycop with acetic anhydride (and if necessary nitric acid) in tetrachloromethane has been investigated.28 The reagent system is found to be modestly catalytic and regioselective in the mononitration of toluene but is neither catalytic nor regioselective in the nitration of 2-nitrotoluene. 

Laszlo and co-workers[11,25-271 developed a reagent known as claycop, which is Cu(NC>3)2 supported on acidic montmorillonite clay, that selectively nitrates toluene using nitric acid, and acetic anhydride as water trapping reagent (Menke conditions). The reaction conditions required to obtain high selectivity of the para-isomer... 

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

Copper(II) nitrate impregnated on K 10 clay (claycop)-hydrogen p xide system is an effective reagent for the oxidation of a variety of substrates (55) and provides excellent yields of products (Scheme 11) wherein the maintenance of pH of the reaction mixture is not required. 

Aromatization of Hantzsch dihydropyridines to pyridines can be effected by the solid-supported reagent "Claycop" (cupric nitrate on montmorillonite). The reaction is strongly accelerated by sonication, but no change in the selectivity occurs. The method is successful only when an aryl group substitutes the 4-position.202 No mechanism is proposed, although the authors mention that nitric acid or nitronium or nitrosonium ions could be involved (Fig. 36). 

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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