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Two new heterocycles (IV) and (VII) are prepared in three steps using a montmorillonite K-10-catalyzed intramolecular Friedel—Crafts cyclization as key reaction.

Nitration of benzocyclobutene (1) using acetyl nitrate, generated in situ by a continuous process, in the presence of montmorillonite K 10 clay gives 3-nitrobicyclo[4.2.0]octa-1,3,5-triene (2) in 60% yield which is a two-fold increase over the known methods.

Irradiation of 4-aryl-4-alkylhex-5-en-2-ones (e.g. 1a) or 5-aryl-4-alkylhex-5-en-2-ones (e.g. 2a) adsorbed on montmorillonite K-10 in a commercial microwave oven furnishes the multialkylated naphthalenes (e.g. 3).

This paper reports a simple method for the preparation of isopropylidene carbohydrates using clay as a catalyst. Treatment of various monosaccharides and/or ribonucleosides with acetone in the presence of clay such as a montmorillonite K 10 (K 10) under mild reaction conditions gave isopropylidene carbohydrates (1–7) in good yields.

The reactions of primary and secondary amines with aldehydes and ketones, respectively, are accelerated by microwaves under solvent-free conditions in the presence of montmorillonite K 10 clay to afford a high yield synthesis of imines and enamines.

Montmorillonite K-10 and KSF catalyse the acetylation of alcohols, thiols, phenols and amines with acetic anhydride in excellent yield.

Highly practical aryl C-glycosidations of unprotected 1-OMe and 1-OH sugars with phenol and naphthol derivatives were effectively realized using montmorillonite K-10 as an environmentally compatible solid acid in CHCl 3 or H 2 O.

A solvent-free reductive amination of carbonyl compounds by wet montmorillonite K 10 clay supported sodium borohydride is described; microwave irradiation facilitates the procedure.

A manipulatively simple and rapid method for the synthesis of flavones is described via a solid-state dehydrative cyclization of o-hydroxydibenzoylmethanes on a clay surface using microwaves.

Selective and easy synthesis of acylals in dry media using montmorillonite K-10 clay in an Erlenmeyer flask under microwave activation in remarkably reduced reaction time is described.

A simple and selective oxidation of alcohols to carbonyl compounds on clay supported ammonium chlorochromate under solventless conditions is expedited by microwave irradiation.

A simple, elegant and one-pot synthesis of 3,4-dihydro-4-phenylcoumarins, 4-phenylcoumarins and their derivatives by making use of solid support, montmorillonite K-10 clay in conjunction with microwave irradiation is described.

A variety of porphyrins and pyrromethanes are prepared using Montmorillonite clay mixed with a variety of acids (p-TsOH, BF3 Et2O).The ease of use of the naturally occurring clay as a co-catalyst makes it an attractive reagent for use in synthesis.

Aryl-substituted α,β-difluoroallyl alcohols 1 were readily hydrolyzed in the presence of a catalytic amount of montmorillonite K 10 (clay) in hexane at reflux temperature for 1 h to give the corresponding (Z)-α-fluoro-β-aryl-substituted acrylaldehydes 2 in good yields.

N-Sulfonylimines are prepared expeditiously in a one-pot solventless operation by microwave thermolysis of aldehydes and sulfonamides in the presence of benign reagents, calcium carbonate and montmorillonite K 10 clay.

A variety of alcohols were oxidized to the corresponding carbonyl compounds by reaction of ammonium chlorochromate adsorbed on montmorillonite K-10 in dichloromethane at room temperature in excellent yields.

Novel stereocontrolled glycosidations of 3,4-di-O-protected olivoses and alcohols using a heterogeneous and environmentally benign solid acid, montmorillonite K-10, have been developed. The glycosidations of the 3-O-Ac-4-O-TBS-olivose (4) and various alcohols using montmorillonite K-10 in CH2Cl2 at 25 °C exclusively gave the corresponding α-olivosides in high yields. On the other hand, the corresponding β-olivosides were predominately obtained by the glycosidations of the 3-O-TBS-4-O-Ac-olivose (5) and various alcohols under similar conditions.

In the presence of montmorillonite K-10 4,4-dialkylcholest-5-enes undergo backbone rearrangement to give (20R)- and (20S)-4,4-dialkyl-5β,14β-dimethyl-18,19-dinor-8α,9β,10α-cholest-13(17)-enes in high yields.

A rapid one-pot synthesis of imidazo[1,2-a] annulated pyridines, pyrazines and pyrimidines is described that occurs in the presence of recyclable montmorillonite K 10 clay under solvent-free conditions using microwave irradiation.

Carboxylic acids are regenerated from their corresponding substituted allyl esters by Montmorillonite K-10 using microwave irradiation under solvent free conditions to afford enhanced yields and reduced reaction times compared to thermal conditions.

Tetrahydropyranyl ethers were rapidly and selectively oxidized to the corresponding carbonyl compounds by clay supported ammonium chlorochromate under solvent free conditions using microwaves.

Potassium ferrate supported onto montmorillonite K-10 was found to deprotect trimethylsilyl ethers oxidatively to the corresponding carbonyl compounds in non-aqueous conditions.

The addition of thiols and thiobenzoic acids onto olefins proceeded regioselectively in a Markovnikov manner in the presence of Montmorillonite K 10 (Mont K 10) clay as the catalyst to afford thioethers and thiocarboxylic S-esters, while high selectivity to anti-Markovnikov products was realized in the absence of any catalyst. Treatment of the esters with Lawesson's reagent provided the corresponding dithiocarboxylic esters in high yields.

A variety of acetals and ketals were oxidatively deprotected to their parent compounds using potassium ferrate(VI) supported on montmorillonite K-10 under non-aqueous conditions.

An environmentally benign and highly stereoselective β-glucopyranosylation without neighboring group participation has been developed employing benzyl-protected glucopyranosyl diethyl phosphite as a glycosyl donor and montmorillonite K-10 as an activator.

The oxidation of hydrobenzoins to the corresponding benzils was carried out in excellent yield by ammonium chlorochromate (ACC) supported on montmorillonite K10 in CH2Cl2 at room temperature under ultrasound irradiation.

The isomerization of terpinolene oxide (1) in the presence of montmorillonite K-10 catalyst was studied. High selectivity of Karahanaenone [(2), 2, 2, 5-trimethy1-4-cyclohepten-1-one, isolated yield 82 %] was attained by the simple solid-liquid phase heterogeneous reaction.

It has been found that SbCl 3 supported on montmorillonite K-10 is an efficient and reusable catalyst for Friedel–Crafts alkylation of nitrogen heterocycles such as indoles and pyrroles with epoxides. The reaction gives the corresponding C-alkylated derivatives in good to excellent yields with a high regioselectivity.

Microwave-assisted and thermal condensations of aromatic and aliphatic aldehydes with β-naphthol adsorbed onto montmorillonite K-10 were conducted in a one-pot procedure leading to the formation of a variety of xanthene derivatives. Under microwave irradiation, reactions completed within 4–6 min. The procedure is applicable to both aromatic and aliphatic aldehydes, and the catalyst was recycled and reused efficiently in later reactions.

Montmorillonite K-10 catalyzed efficiently the Knoevenagel condensation of carbonyl compounds with malonitrile and ethylcyanoacetate in dry media under microwave irradiation.

9 pages, 3 tables, 1 scheme.-- Supporting information (26 pages) available at: http://www.wiley-vch.de/contents/jc_2046/2007/o200700296_s.pdf

In the present paper, a series of substituted 1,3,4-oxadiazoles have been synthesized by three different methods i.e. conventional heating, microwave irradiation method 1 and microwave irradiation method 2. Conventional heating, microwave irradiation method 1 and microwave irradiation method 2 were compared in terms percent yield, reaction time, percent atom economy and environment quotient (eco-friendly). The results showed that microwave irradiation method 2 was remarkably greener and ecofriendly than microwave irradiation method 1 and conventional heating. Derivatives of 1,3,4-oxadiazoles were characterized on the basis of IR, 1H NMR and Mass spectral data and the structures of the synthesized compounds were confirmed. All compounds were screened for their in vitro antibacterial, antitubercular and antifungal activity. However the results indicated that the synthesized compounds have less activity with reference to their respective standards.

A series of naphthalene, indene, and 6aH-benzo[c]fluorene derivatives are synthesized by intramolecular rearrangement of vinylidenecyclopropanes using a heterogeneous solid acid catalyst, montmorillonite K-10, under mild reaction conditions in good to excellent yields. The solid acidic catalyst, montmorillonite K-10, can be recovered and reused.