Montmorillonite K10 clay

It has been shown by Varma et al. [61] that reaction of primary and secondary amines with aldehydes and ketones is substantially accelerated by microwaves under solvent-free conditions in the presence of montmorillonite K10 clay, affording high yields of imines and enamines (Eq. 10). 

Rh(COD)(PPh3)2]BF4 has been shown to be a good catalyst for reductive ami-nation of acetone with 4-anilino-aniline to give the commercial product 3-IPPD. In laboratory-scale comparative experiments, this catalyst - both in homogeneous phase or immobilized on Montmorillonite K10 clay - was found to be superior to the commercially applied Pt/C catalyst (Scheme 15.11) [80]. 

Acidic clay catalysts can also be used in alkylation with alcohols 98 The main advantages of these catalysts are the reduced amount necessary to carry out alkylation compared with conventional Friedel-Crafts halides, possible regeneration, and good yields. Natural montmorillonite (K10 clay) doped with transition metal cations was shown to be an effective catalyst 200... 

A microwave-assisted Fischer indole synthesis under solvent-free conditions with Montmorillonite K10 clay modified with zinc chloride was employed in a key step of the synthesis of analogues of the cytostatic natural product, Sempervirine (Scheme 3.6)8. A dedicated laboratory microwave synthesizer was utilised. 

A protocol for the rapid oxidation of alcohols to carbonyl compounds has been reported with montmorillonite K10 clay-supported iron(III) nitrate (clayfen). The simple solvent-free experimental procedure involved mixing of neat substrates with clayfen, followed by microwave irradiation for 15-60 s [44]. The use of clayfen mixed with iron(III) nitrate on clay as an oxidant afforded higher yields (Scheme 4) and was more efficient, since the... 

A solvent-free reductive amination of carbonyl compounds using sodium borohydride supported on moist montmorillonite K10 clay also was facilitated by microwave irradiation (Scheme 8) [54]. Clay served the dual purpose of a Lewis acid and provided water from its interlayers to enhance the reducing ability of NaBH4. 

Heating a variety of phenols with isoprene under pressure in the presence of a zeolite catalyst affords chromans in good yield <1998S301>. Likewise, the synthesis of 2,2-dimethylchromans can be achieved via Montmorillonite K10 clay catalyzed condensation of substituted phenols with prenyl bromide <2004SL2028>. 

Rak, V. S., and Y. I. Tarasevich. 1982. Ion-exchange sorption of a-amino acids by montmorillonite with a divalent cation in the exchange complex. Teoreticheskaya i Eksperimentalnaya Khimiya 18 166-174. (in Chemical Abstracts, Vol. 96, 223829k). Ramchandani, R. K., B. S. Uphade, M. P. Vinod, R. D. Wakhankar, V. R. Choudhary, and A. Sudalai. 1997. Pd-Cu-exchanged montmorillonite K10 clay An efficient and reusable heterogeneous catalyst for vinylation of aryl halides. Chem. Commun. 2071-2072. 

Three component condensation of N,N -dimethyl urea, paraformaldehyde and primary amines using montmorillonite K10 clay in dry media under microwave irradiation (MWI) lead to the formation of triazones whereas condensation of dimethyl urea and paraformaldehyde supported on montmorillonite KIO using MWI gave 4-oxo-oxadiazinone (Scheme 82)7 ... 

Montmorillonite clays are layered silicates montmorillonite K-10 is a specially manufactured acidic catalyst (Montmorillonite K10, [1318-93-0] A. Comelis, P. Laszlo, M. W. Zettler in eEROS Encyclopedia of Reagents for Organic Synthesis, L. A. Paquette, Ed., John Wiley and Sons, Inc., online reference available at http //www.intersciene.wiley.com)... 

Ail equimolar mixture (10 mmol) of benzylidenemethylamine 1 (1.19 g) and acetylacetone 2a (1 g) was adsorbed onto montmorillonite K10 (5 g) and allowed to stand at room temperature for 3 days. The mixture was extracted with CH2C12, the clay separated by filtration and the solvent evaporated under reduced pressure. Pure compound 3 could be isolated by short-path distillation (81% yield). The equimolar mixture of enamino ketone 3 and alkene 4a (5 mmol) was allowed to stand at room temperature for a suitable time. Washing with suitable solvent afforded the pure solid product 5. 

KIO is often confused, both in name and in use, with other clay-based acidic catalysts (KSF, KlOF, Girdler catalyst, acid treated or H" "-exchanged montmorillonite or clay, etc.) that can be effectively interchanged for K10 in some applications. Between the 1930s and the 1960s, such acid-treated montmorillonites were common industrial catalysts, especially in petroleum processing, but have now been superseded by zeolites. 

Alumina, silica, clays, and zeolites are increasingly used as acidic or basic supports [26], Cycloaddition reactions often require Lewis-acid catalysts if good yields are to be obtained. Clay and doped silica gel catalysts have emerged as useful alternatives to the use of Lewis acids. Cycloaddition offuran (5) under solvent-free conditions, catalyzed by K10 montmorillonite, results in a decrease in the reaction time the endo-exo relationship is no different that obtained by use of classical heating (Scheme 9.2) [27]. 

K2Fe04, K10 montmorillonite clay (1° benzylic and allylic 2° alkyl)... 

Aluminas, silicas, clays, zeolites or graphite can be selected as acidic, basic or neutral supports, depending on the type of reactions. Alumina alone can act as a base towards a acid compounds but if a strong base is necessary, KF on alumina can ionize carbon acids up to pKa = 35. On the other hand, montmorillonites (clays) such as K10 or KSF offer acidities very comparable to strong mineral acids (e.g., nitric and sulfuric acids, respectively). Reactions are simply performed by mixing reagents and a mineral support in the absence of any organic solvent followed by microwave irradiation [52]. 

In the literature, different commercial montmorillonites are used, especially for catalytic purposes (KSF or K10 montmorillonites). They are usually acid-treated clays, montmorillonite content of which is rather low. Our x-ray diffraction studies show 44% Ca-montmorillonite content of K10 montmorillonite, and 53% Na-montmorillonite content of KSF montmorillonite the CEC of KSF montmorillonite was found to be 30 meq/100 g by the ammonium acetate method (Richards 1957). A similar value has been given by Abollino et al. (2003). So, in a strict clay science sense, they cannot be considered as montmorillonite. Naturally, this causes no problems in organic chemistry when the main objective is the catalysis of a given reaction. 

Nonpoisonous and non hydrolyzable neodymium chloride has been used on clay for the same reaction, giving 80% selectivity where X = Cl and R = H.243 There was no loss in activity after 5000 turnovers. Zinc chloride on K10 montmorillonite can also be used with reagents in the vapor phase (6.44).244... 

Reactions on clay catalysts show some selectivity by size and shape. Aluminum montmorillonite was used to rearrange phenyl ethers (6.45).246 The bulkier 7ert-butyl group led to only the para product. Allylation of aromatic compounds with octenols (6.46) gave only the unbranched isomer.247 Aniline can be ethylated with ethanol to give 86% TV-ethylaniline and 14% TVW-diethylaniline in 52% conversion with K10 montmorillonite with, or without, vanadium oxide at 400°C.248... 

One of the important catalytic processes based on shape selectivity is the alkylation of biphenyl with propene (Reaction 4). Pinnavaia et al. have shown that mesoporous clays such as K10 and alumina-pillared montmorillonite are more selective than homogeneous acid catalysts, although not as... 

The optimum loading for a high surface area mesoporous silica is about 1.5 mmol g-1, twice as high as that for the acid-treated montmorillonite clay K10. The former catalyst is also a little more active and selective towards monoalkylation, although K10 is a less expensive support material. 

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