Synthesis montmorillonite

The kinetics of PAA, synthesized from 4,4 -oxydianiline and pyromellitic dianhydride, solid-state imidization both in filler absence and with addition of 2 phr Na+-montmorillonite was studied [1], The nanofiller was treated by solution of P-phenylenediamine in HC1 and then washed by de-ionized water to ensure a complete removal of chloride ions. The conversion (imidization) degree Q was determined as a function of reaction duration t with the aid of Fourier transformation of IR-spectra bands 726 and 1014 cm 1. The samples for FTIR study were obtained by spin-coating of PAA/Na+-montmorillonite mixture solution in N,N-dimethylacetamide on KBr disks, which then were dried in vacuum for 48 h at 303 K. It was shown, that the used in paper [1] method gives exfoliated nanocomposites. The other details of nanocomposites polyimid/Na+-montmorillonite synthesis and study in paper [1] were adduced. The solid-state imidization process was made at four temperatures 7) 423, 473, 503 and 523 K. 

WAXS indicated the possible full exfoliation of the montmorillonite in the polyethylene. No TEM pictures were provided. The tensile strength of the polyethylene increased from approximately 29.8 MPa for the pure polymer to approximately 33.6 MPa for a 2.8 wt. % montmorillonite content in the polyethylene. The disadvantage of this approach is the necessity to utilize solvents for the polyethylene-montmorillonite synthesis. 

E. C. Taylor and C.-S. Chiang, Synthesis, 467 (1977). Montmorillonite clay is activated Al203/Si02/H20. 

Newer catalysts for the PK synthesis include montmorillonite clays,... 

A solvent-free strategy for the synthesis of thiazoles involved mixing of thioamides with a-tosyloxy ketones in a clay-catalyzed reaction (Scheme 7). The typical procedure entailed mixing of thioamides and in situ produced a-tosyloxy ketones with montmorillonite K-10 clay in an open glass container. The reaction mixture was irradiated in a microwave oven for 2-5 min with intermittent irradiation and the product was extracted into ethyl acetate to afford 2-substituted thiazoles in 88-96% yields [8]. 

The synthesis of imidazoles is another reaction where the assistance of microwaves has been intensely investigated. Apart from the first synthesis described since 1995 [40-42], recently a combinatorial synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles has been described on inorganic solid support imder solvent-free conditions [43]. Different aldehydes and 1,2 dicarbonyl compounds 42 (mainly benzil and analogues) were reacted in the presence of ammonium acetate to give the trisubstituted ring 43. When a primary amine was added to the mixture, the tetrasubstituted imidazoles were obtained (Scheme 13). The reaction was done by adsorption of the reagent on a solid support, such as silica gel, alumina, montmorillonite KIO, bentonite or alumina followed by microwave irradiation for 20 min in an open vial (multimode reactor). The authors observed that when a non-acid support was used, addition of acetic acid was necessary to obtain good yields of the products. 

For the synthesis of coumarins, the Pechmann reaction [145] is one of the most popular synthetic routes. As the reaction is conventionally carried out at high temperature, two microwave-assisted versions have been recently described. Besson and co-workers described the cyclocondensation of different m-amino phenols 226 with /1-ketoesters 227 on graphite/montmorillonite KIO support (Scheme 83). The use of graphite was crucial in the development of the reaction conditions. In fact, microwave irradiation of the reagents using different conditions gave poor results in terms of yields and purity. The optimized conditions, using a monomode microwave system, employed... 

Bigi F, Chesini L, Maggi R, Sartori G (1999) Montmorillonite KSF as an inorganic, water stable, and reusable catalyst for the knoevenagel synthesis of coumarin-3-carboxylic acids. J Org Chem 64 1033-1035... 

Biswas GK, Basu K, Barua AK, Bhattacharyya P (1992) Montmorillonite clay as condensing agent in Pechmann reaction for the synthesis of coumarin derivatives. Indian J Chem 31B 628-628... 

Armin Weiss (1981) presented some results of experimental work using mont-morillonite, he was able to show that the complete information present in a matrix is passed on to the daughter layers. In principle, the intercalating synthesis of a new layer of montmorillonite from the nutrient solution can be compared to the replication of a DNA chain. The distance between the layers is of great importance in these experiments and acts as a performance-limiting factor. 

The first indication of a possible connection between geological processes occurring at the boundaries between tectonic plates of the mid-oceanic ridges and the biogenesis problem was provided by J. B. Corliss (1981). He considered the hydrothermal conditions to be ideal reactors for abiotic synthesis these ideal conditions were the water temperature gradients, the pH, and the concentrations of solutes in the hot springs. The presence of certain minerals which could act as catalysts, such as montmorillonite, clay minerals, iron oxide, sulphides etc., was also very important. The initial model presented for the hydrothermal synthesis of biomolecules (Corliss, 1981) was modified, particularly by Russell (1989) and Wachtershauser (see Sect. 7.3). 

Biswas, M. and Sinha Ray, SRecent Progress in Synthesis and Evaluation of Polymer-Montmorillonite Nanocomposites. Vol. 155, pp. 167-221. 

A milder Clauson-Kaas pyrrole synthesis was reported that alleviated the need for acid or heat <06TL799>. The innovation involved the hydrolysis of 2,5-dimethoxytetrahydrofuran giving 2,5-dihydroxytetrahydrofuran. The latter was converted into pyrroles by treatment with primary amines in an acetate buffer. The Clauson-Kaas pyrrole synthesis was studied utilizing a K-10 montmorillonite acid catalyst and microwave irradiation <06OPP495>. Mild reaction conditions (cat. p-TsOH) allowed for the preparation of pyrrole-3-carboxaldehydes from 2,5-dimethoxytetrahydrofuran-3-carboxaldehydes <06S1494>. 

J.-C. Florent and C. Monneret, Stereocontrolled route to 3-amino-2,3,6-trideoxy-hexopyranoses. K-10 Montmorillonite as a glycosidation reagent for acosaminide synthesis, J. Chem. Soc., Chem. Commun. (1987) 1171-1172. 

K. Ikeda, Y. Ueno, S. Kitani, R. Nishino, and M. Sato, Ferrier glycosylation reaction catalyzed by Bi(OTf)3-Montmorillonite K-10 Efficient synthesis of 3,4-unsaturated sialic acid derivatives, Synlett (2008) 1027-1030. 

A simple montmorillonite K 10 clay surface is one among numerous acidic supports that have been explored for the Beckmann rearrangement of oximes (Scheme 6.27) [54]. However, the conditions are not adaptable for the aldoximes that are readily dehydrated to the corresponding nitriles under solventless conditions. Zinc chloride has been used in the above rearrangement for benzaldehyde and 2-hydroxyacetophe-none, the later being adapted for the synthesis of benzoxazoles. 

A solvent-free synthesis of flavones has been achieved that simply involves the MW irradiation of o-hydroxydibenzoylmethanes adsorbed on montmorillonite K 10 clay for 1-1.5 min. A rapid and exclusive formation of cyclized flavones occurs in good yields (Scheme 6.41) [140], The intramolecular Michael addition of o-hydroxy-... 

Addition of a solid acid catalyst such as Montmorillonite K10 increased the yield significantly under the action of either thermal heating (64%) or MW irradiation (66%) [52 c]. Under the latter conditions the reaction time was reduced. Comparable results were obtained for the synthesis of aminocoumarins 39-42 (Tab. 7.3) [53]. 

A rapid one-pot synthesis of imidazo-[l,2-a]-pyridines, pyrazines and pyrimidines was described in 1999 by Varma et al. [50], who used recyclable montmorillonite clay Kio under solvent-free conditions and microwave irradiation (Scheme 8.32). 

An Iranian group described the synthesis of some [l,3,4]thiadiazolo[2,3-c][l,2,4]triazinones 88 <2002PS2399> and in the course of the synthetic pathway the dihydro derivative 87 was first obtained. These authors found that microwave irradiation of 87 on montmorillonite in the presence of nitrobenzene allowed to accomplish the final oxidative step and yielded the fully conjugated end-product in good yields (50-62%). The reaction as proceeding was interpreted by electron transfer to 89 caused by the microwave irradiation followed by the formation of the intermediate radical 90. 

Yet more improvements in the synthesis of chlorocyclophosphazenes have appeared. Yields in the PC15-NH4C1 reaction are increased by the use of heavy-metal salts as catalysts,93 but similar results may also be achieved by the use of acid-treated montmorillonite clay.94 The use of surfactants can also improve yields of cyclic products.95... 

Y. Kojima, A. Usuki, M. Kawasumi, A. Okada, T. Kurauchi, 0. Kamigaito, Synthesis of nylon 6-clay hybrid by montmorillonite intercalated with e-caprolactam, Journal of Polymer Science Part A Polymer Chemistry, vol. 31, pp. 983-986,1993. 

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