Copper nitrate-Montmorillonite

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... 

To elevate p-selectivity in nitration of toluene is another important task. Commercial production of p-nitrotoluene up to now leads with twofold amount to the unwanted o-isomer. This stems from the statistical percentage of o m p nitration (63 3 34). Delaude et al. (1993) enumerate such a relative distribution of the unpaired electron densities in the toluene cation-radical—ipso 1/3, ortho 1/12, meta 1/12, and para 1/3. As seen, the para position is the one favored for nitration by the attack of NO (or NO2 ) radical. A procednre was described (Delande et al. 1993) that used montmorillonite clay supported copper (cupric) nitrate (claycop) in the presence of acetic anhydride (to remove excess humidity) and with carbon tetrachloride as a medinm, at room temperature. Nitrotoluene was isolated almost quantitatively with 23 1 76 ratio of ortho/meta/para mononitrotoluene. 

Novel reagents consisting of metallic nitrates impregnated on montmorillonite have been introduced in aromatic nitration. With clay-supported copper(II) nitrate in the presence of acetic anhydride it is possible to nitrate toluene quantitatively with a high para preference (79% para, 20% ortho, 1% meta). Also, good para selectivities have been found on nitration of some other aromatic hydrocarbons with copper(II) nitrate on clay. Halobenzenes are mononitrated with clay-supported copper(II) nitrate in the presence of acetic anhydride. Compared to other methods high para ortho ratios are obtained under these conditions. ... 

The 1,4-dihydropyridines produced in this approach, carrying conjugating substituents at each /3-position, are stable, and can be easily isolated before dehydrogenation classically the oxidation has been achieved with nitric acid, or nitrous acid, but other oxidants such as cerium(IV) ammonium nitrate, copper(II) nitrate on montmorillonite, and manganese dioxide on bentonite also all achieve this objective smoothly. ... 

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