Montmorillonite K10 Research Articles

Highly dispersed Ni-Ce catalyst over clay montmorillonite K10 in low-temperature CO2 methanation

The Carbon Capture and Utilization (CCU) option can be an efficient solution for CO2 emission mitigation. To this end, we have investigated the carbon dioxide methanation at low temperatures. Highly active, selective, stable, low-cost catalysts are required for energy and carbon balance benefits. Supported nickel-based catalysts result as the most studied and promising candidates showing a good compromise between performance and low preparation costs. The catalyst design role is key to obtaining the best performance, requiring many experiments and optimisation procedures. Herein, the enhanced Montmorillonite MK10-supported Ni(0)Ce(III) catalyst, prepared by consecutive hydrothermal and electrostatic adsorption methods followed by reduction under hydrogen flow, was used in batch CO2 methanation, exhibiting 76 % of CO2 conversion with 100 % CH4 selectivity after 3 h. The catalytic system reveals very high robustness preserving the same activity and selectivity for at least 5 reaction cycles if compared with γ-Al2O3-supported Ni(0)Ce(III) catalyst, the latter showing the same activity but only in the first cycle. EDX, XPS, SEM, TPD, TPR, and BET characterisation techniques were used to elucidate and evaluate the potential synergistic effect of the active metal centre-promoter-support interfaces, highlighting their role in the activity and robustness of the catalyst, comparing the same effect using different alumina and silicate solid supports. The effects of the reaction conditions on the methane yield and selectivity were also evaluated.

Advancing the design of heterogeneous catalyst: Copper-montmorillonite for regioselective alkyne hydroamination

Transition metal catalysts supported on natural materials offer promising avenues for sustainable organic synthesis. In this study, we present the synthesis, characterisation, and catalytic performance of copper nanoparticles supported on montmorillonite K10 (CuMK10) as a heterogeneous catalyst for hydroamination reactions. CuMK10, synthesised through a robust and established nanoparticle synthesis methodology, demonstrates remarkable catalytic efficiency and selectivity in the synthesis of imines via hydroamination of terminal alkynes. The catalyst exhibits exceptional regioselectivity, predominantly yielding Markovnikov products, demonstrating its potential as a versatile tool in organic synthesis. Moreover, CuMK10 shows favourable reusability, offering economic benefits and practical utility due to its ease of recovery and reuse. Comprehensive structural and mechanistic studies provide insights into the catalyst's performance, paving the way for the development of efficient and environmentally benign catalytic systems.

Unusual Cascade Reactions of 8-Acetoxy-6-hydroxymethyllimonene with Salicylic Aldehydes: Diverse Oxygen Heterocycles from Common Precursors.

Chiral oxygen-containing heterocyclic compounds are of great interest for the development of pharmaceuticals. Monoterpenes and their derivatives are naturally abundant precursors of novel synthetic chiral oxygen-containing heterocyclic compounds. In this study, acid catalyzed reactions of salicylic aldehydes with (-)-8-acetoxy-6-hydroxymethyllimonene, readily accessible from α-pinene, leads to the formation of chiral polycyclic products of various structural types. Three of the six isolated chiral heterocyclic products obtained from salicylic aldehyde contain previously unknown polycyclic ring types. Having carried out the reaction in the presence of Brønsted or Lewis acids (Amberlyst 15, trifluoromethanesulfonic acid, trifluoroacetic acid and boron trifluoride etherate) or aluminosilicates (montmorillonite K10, halloysite nanotubes), we found that the nature of products depends on the catalyst as well as the reaction conditions (reaction time, reactant ratio, presence or absence of solvent). Detailed mechanistic insight on the complex cascade reactions for product formation is provided with extensive experimental and quantum mechanical computational studies.

Interaction of Curing and Soaking on Collapse Potential of Nanoclay-Treated Soil

This study examines the combined impact of pre-test curing and soaking periods on the soil's resistance to collapse those results from treating gypseous sand with varying amounts of nanoclay. The soil comes from the Iraqi city of Najaf. The soil sample is mainly sand. The nanoclay named "Montmorillonite K10" is used, and it is non-toxic. The tests are performed with a computerized Oedometer. The collapse potential is estimated according to a single Oedometer test (SOT), where the specimens are initially dry and then soaked under a stress level of 200 kPa. Four data sets related to the percentages of 0, 3, 6, and 12% nanoclay are used. Each data set comprises three groups of pre-tests for curing duration and different soaking durations. All experiments have a constant initial dry density of 1.64 g/cm3, water moisture of 3%, and gypsum content of 29%. The findings of this study show that the collapse potential (CP) of natural soil specimens decreases as the pre-test curing time increases. Generally, there is a decrease in CP due to adding the nanoclay and 6% of the nanoclay exhibited the highest reduction in CP. Also, there is an increase in the pre-test curing for the nanoclay-treated soil specimens, which leads to an increase in the CP related to the no-curing state.

Preparation and characterization of clay hybrid adsorbents for the removal of paracetamol from model wastewater: A comparative study

Paracetamol, an emerging contaminant, in low concentration (ng/L to mg/L), is discharged as a pharmaceutical residue from wastewater plants into water bodies, endangering flora, fauna, and human health through bioaccumulation. Various adsorbents like titania (S1), silica (S2), titania and silica clay composites (S3 and S4) and montmorillonite K10, (S5) were tried for paracetamol uptake in a model wastewater system. All adsorbents were prepared by a sol-gel route at room temperature and were characterized by Fourier Transform Infra-Red, X-ray diffractometer, Scanning Electron Microscope, and Brunauer-Emmett Teller for the nature of functional groups, structure, and specific surface area. The silica clay composite (S4) showed a mesoporous network with an average pore diameter of 3.5 nm, leading to 74% removal of PCT in fifteen minutes of batch adsorption run time. A pseudo second order kinetic model was found fit for S4 with no formation of PCT metabolite as residue as observed from UV spectra. The maximum adsorption capacity of S4 was 1.86 mg/g of the silica clay composite material.

Montmorillonite K10 clay promoted one-pot pseudo-five-component synthesis of 5-cyano-6-(phenylthio)-2-((1-phenylvinyl)imino)-4- aryl(or heteroaryl)-2H-pyran-3-carboxylic acid derivatives and their potential cytotoxic activity

Montmorillonite K10 clay promoted one-pot pseudo-five-component synthesis of 5-cyano-6-(phenylthio)-2-((1-phenylvinyl)imino)-4- aryl(or heteroaryl)-2H-pyran-3-carboxylic acid derivatives and their potential cytotoxic activity

Montmorillonite K10-induced decomposition of methyl N-phenylcarbamate to phenylisocyanate and its prospect for recovering isocyanates from polyurethanes

The significant growth of the production and use of flexible polyurethane (PU) foam causes increased waste accumulation, thereby creating a demand for the recycling of PU. While upgrading PU materials to recycled polyols has been studied in detail, the recovery of diisocyanates is a longstanding challenge. Montmorillonite K10 (MK10) has been proposed as a catalyst to convert carbamates into isocyanates, but its prospects are unclear. Here, the MK10-catalyzed decomposition of methyl phenylcarbamate (MPC) into phenylisocyanate (PI) and the side product N,N’-diphenylurea (DPU) has been studied as a model reaction for the decomposition of PU foam and the potential recovery of PI. The effects of the amount of catalyst, the temperature, and the solvent were investigated by HPLC analyses. Kinetic analysis revealed that the uncatalyzed rate of the MPC decomposition is much lower than the catalyzed rate, indicating that the thermally driven decomposition is negligible. Our results, involving both experimental kinetic studies and models of the kinetics, show that, while MK10 effectively catalyzes the decomposition of MPC, it also causes the formation of aniline, which reacts with PI to form DPU. As a result, large amounts of MK10 favor DPU and prevent the selective formation of PI, and yields of PI >30 % were never observed. Likely, the OH groups of MK10 form covalent bonds with PI, causing a deficiency in the mole balance. Overall, MK10 is unsuited to provide high yields of isocyanates.

Breaking through the pH Limitation of Fe1-xS Nanozymes Using Component-Modulated Coupled Nanoclay.

Overcoming the intrinsic low activity of most peroxidase mimics under neutral pH is crucial but still extremely challenging for the detection of disease markers in biological samples. Here, we chose nanoclay (i.e., montmorillonite K10, MK10) as a carrier to modulate the structure of Fe1-xS nanozyme components through an interfacial modulation strategy, aiming at breaking the neutral pH limitation of Fe1-xS. MK10 with abundant hydroxyl groups on its surface acts as a carrier to increase the ratio of Fe(II) and S(II-) content in surface Fe1-xS. We verify that Fe(II)-promoted surface hydroxyl radical generation and S(II-)-promoted regeneration of Fe(II) play key roles in endowing peroxidase-like activity to Fe1-xS at neutral pH. As expected, Fe1-xS/MK10 exhibited 11-fold higher Vmax and 52-fold higher catalytic efficiency than bare Fe1-xS. As a proof of concept, the sensor constructed based on Fe1-xS/MK10 achieved colorimetric detection of xanthine under neutral conditions with a linear range of 5-300 μM and a limit of detection of 2.49 μM. Finally, we achieved highly sensitive detection of xanthine in serum using the constructed biosensor. Our contribution is the novel use of a nanoclay-mediated interfacial modulation strategy for boosting the peroxidase-mimicking activity and breaking the pH limitation, which contributes to the in situ detection of disease markers by nanozymes under physiological conditions.

Synthesis of ethyl furfuryl ether via etherification of furfuryl alcohol with ethanol over montmorillonite K10.

Ethyl furfuryl ether (EFE), which is synthesized via etherification of furfuryl alcohol (FFalc) with ethanol over Brønsted acid catalysts, is used as an additive in gasoline to reduce its consumption and CO2 emission. In this work, we demonstrate that the performance of this synthesis route can be improved by using commercially available, low-cost, and environmentally friendly montmorillonite K10, which produces EFE in a relatively high yield of 45.3% and a FFalc conversion of 94.2% at a low reaction temperature of 393 K within 1 h. Other commercially available clay minerals showing Brønsted acidity, namely, kaolinite and halloysite, were also used in the etherification reaction under identical conditions. The catalytic performance followed the order of montmorillonite K10 > halloysite > kaolinite, which is consistent with that of the Brønsted acidities determined via acid-base titration. The spent montmorillonite K10 showed a catalytic performance comparable to that of the fresh catalyst after calcination.

Sustainable pathways to oxicams via heterogeneous biosourced catalysts - Recyclable and reusable materials

The current study highlights the synthesis of Zn-enriched biosourced catalysts (BIOCATs) obtained from ryegrass (Lolium perenne L.) cultivated on contaminated soils located in the North of France (Noyelles-Godault and Auby, Hauts-de-France). These cultures were located on brownfield land, next to two former industrial sites where the zinc and lead metallurgists Metaleurop and Nyrstar were installed. Physical and morphological properties of BIOCATs were compared to heterogeneous catalysts (CATs) prepared from commercial zinc chloride and montmorillonite K10. The catalysts were thermally activated (120 °C, 280 °C or 500 °C). BIOCATs have been further compared to CATs and different commercial metal chlorides in terms of efficiency in the synthesis of anti-inflammatory agents, Piroxicam and Meloxicam, both of them being involved in the inhibition of cyclooxygenases (COX) and being the main ingredients of the Feldene® and Mobic® drugs, respectively. BIOCAT-assisted synthesis resulted in the best reaction yields (84% and 78%, respectively) among all the tested catalysts. The results indicated that ryegrass provides appropriate quantity of biomass and can be considered as a bio-ore resource to improve green metrics in an environmental context involving clean and green technologies. Furthermore, the Zn/Cd and Zn/Pb ratios obtained in the ashes of ryegrass shoots were in general comprised between 153 and 202. This result demonstrated the excellent selectivity of ryegrass for zinc at the expense of the more problematic Cd and Pb, which are carcinogenic, mutagenic and reprotoxic. Future efforts are now needed to use BIOCATs in the synthesis of other high value-added molecules.

Montmorillonite K10 clay accelerated green protocol for the pseudo-five-component synthesis of substituted imidazo[1,2-a]pyridines

An array of conjugated Imidazo[1,2-a]pyridines were synthesized via a one-pot, pseudo-five-component reaction incorporating aryl aldehydes, malononitrile, thiophenol or phenol, and acetophenone or acetyl derivatives stimulated by Montmorillonite K10 clay as an eco-friendly catalyst. The entire procedure involves the formation of two new rings, three C–N bonds, two C-C bonds, and one C–X bond. This strategy enables quick green access to functionally multifaceted imidazo[1,2-a]pyridine analogues while highlighting good yields, pure products, an expedient reaction condition, and the reusability of the catalyst up to two cycles. All of the synthesized compounds were characterized through 1H,13C NMR, mass spectrometry, and infrared spectroscopy techniques.

Effect of montmorillonite K10 clay on RNA structure and function

One of the earliest living systems was likely based on RNA (“the RNA world”). Mineral surfaces have been postulated to be an important environment for the prebiotic chemistry of RNA. In addition to adsorbing RNA and thus potentially reducing the chance of parasitic takeover through limited diffusion, minerals have been shown to promote a range of processes related to the emergence of life, including RNA polymerization, peptide bond formation, and self-assembly of vesicles. In addition, self-cleaving ribozymes have been shown to retain activity when adsorbed to the clay mineral montmorillonite. However, simulation studies suggest that adsorption to minerals is likely to interfere with RNA folding and, thus, function. To further evaluate the plausibility of a mineral-adsorbed RNA world, here we studied the effect of the synthetic clay montmorillonite K10 on the malachite green RNA aptamer, including binding of the clay to malachite green and RNA, as well as on the formation of secondary structures in model RNA and DNA oligonucleotides. We evaluated the fluorescence of the aptamer complex, adsorption to the mineral, melting curves, Förster resonance energy transfer interactions, and 1H-NMR signals to study the folding and functionality of these nucleic acids. Our results indicate that while some base pairings are unperturbed, the overall folding and binding of the malachite green aptamer are substantially disrupted by montmorillonite. These findings suggest that minerals would constrain the structures, and possibly the functions, available to an adsorbed RNA world.

Montmorillonite K10 Clay Accelerated One‐Pot Multicomponent Synthesis of Substituted 2‐Amino‐3,5‐dicarbonitrile‐6‐phenylsulfanylpyridines: Experimental and Theoretical Investigation

Abstract2‐Amino‐3,5‐dicarbonitrile‐6‐phenylsulfanylpyridines occupy a prominent place among the physiologically and biologically active scaffolds owing to their therapeutic applications in the treatment of Parkinson's disease, asthma, urinary incontinence, kidney disease, the Hepatitis B infections, Creutzfeldt–Jacob disease, cancer, hypoxia/ischemia and epilepsy. A one‐pot, multicomponent condensation of aldehydes, malononitrile, and thiophenol catalyzed by Montmorillonite K10 clay afforded 2‐amino‐3,5‐dicarbonitrile‐6‐phenylsulfanylpyridines in good to excellent yields. All the products could be well characterized on the basis of spectral studies. The catalyst could be recycled three times without affecting the yields and even in the fourth recycling of the catalyst, the yield decreases marginally. This approach manifests environmentally benign feasibility in contexts of enhanced yields, milder conditions, short reaction times, and reusability of the catalyst. A theoretical study of a synthesized compound at the B3LYP/6–31 + G (d) level is additionally reported. Following the computation of the fundamental vibrational wavenumbers and intensities, it became evident that the observed and calculated wavenumbers were in perfect accord. Employing the same DFT level, Frontier molecular orbital (HOMO‐LUMO) energies, global reactivity descriptors, and molecular electrostatic potential were estimated for assessing the reactivity and possible sites for electrophilic and nucleophilic molecules. The outcomes prove that the compound exhibits significant kinetic stability.

Montmorillonite Catalyzed Synthesis of Novel Steroid Dimers.

The reactions of sterols (androst-5-en-3β-ol-17-one, diosgenin, and cholesterol) and their tosylates with hydroquinone aimed at the synthesis of O,O-1,4-phenylene-linked steroid dimers were studied. The reaction course strongly depended on the conditions used. The study has shown that the major reaction products are the elimination products and unusual steroid dimers resulting from the nucleophilic attack of the hydroquinone C2 carbon atom on the steroid C3 position, followed by an intramolecular addition to the C5-C6 double bond. A different reaction course was observed when montmorillonite K10 was used as a catalyst. The reaction of androst-5-en-3β-ol-17-one under the promotion of this catalyst afforded the O,O-1,4-phenylene-linked steroid dimer in addition to the disteroidal ether. The formation of the latter compound was suppressed by using 3-tosylate as a substrate instead of the free sterol. The reactions of androst-5-en-3β-ol-17-one tosylate and cholesteryl tosylate with hydroquinone catalyzed by montmorillonite K10 carried out under optimized conditions afforded the desired dimers in 31% and 67% yield, respectively.

Comparative Analysis of Bio- and Chemo-Catalysts for the Synthesis of Flavour Compound Hexanal from Linoleic Acid

Hexanal, hexenal, nonenal and their corresponding alcohols are used as green notes in the fragrance and flavour industry. The production of bio-based hexanal starts from linoleic acid, which can be obtained from sunflower or safflower oil. The biocatalytic process utilizes C13-specific lipoxygenase (LOX) for hydroperoxidation and consecutive splitting with hydroperoxide lyase (HPL). In this study, we investigated the chemical splitting of the LOX product 13-HPODE in comparison to HPL catalysis. In addition, 13-HPODE was synthesized using enriched linoleic acid from safflower oil. Varying amounts of soybean flour suspension as a source of LOX yielded up to 60% HPODE with a regioselectivity of 92% towards 13-HPODE. Using low-toxicity Lewis acids like AlCl3 and ZrCl4, cleavage of the produced 13-HPODE was possible. A maximum hexanal yield of 22.9% was reached with AlCl3 under mild reaction conditions, though product degradation was an interfering process. Comparative trials with N-terminal truncated HPL from papaya revealed hexanal recovery within a comparable range. Additionally, we successfully demonstrated the viability of Hock rearrangement of 13-HPODE through heterogeneous catalysts. Notably, Beta zeolite and Montmorillonite K10 exhibited a turnover frequency (TOF) on par with common heterogeneous catalysts employed in industrial processes.

Organo-modified Montmorillonite-based adsorbents for selective removal of Iron(II) from aqueous solutions

The use of clays for the adsorption of contaminants from water has gained significant attention in recent decades. Clays and their modified forms have been extensively studied for their ability to adsorb both inorganic and organic pollutants. The purpose of this study is to investigate the use of montmorillonite (k10), local montmorillonite (MMT-Na), and their 1,10-phenanthroline modified forms (k10-phen and MMT-phen) for the adsorption of iron(II) ions. Adsorption of iron(II) on k10 and MMT-Na has been observed to be physical; however, adsorption on k10-phen is chemical. Nevertheless, iron (II) adsorption on MMT-phen combines physical and chemical adsorption. To characterize all these clays, X-ray diffraction (XRD), Infrared spectroscopy (IR), thermogravimetric analysis (TGA), and BET nitrogen adsorption–desorption isotherm were performed. In order to determine the specific surface area of the clays, the BET and methylene blue methods were used, and both ways were quite similar. A cation exchange capacity (CEC) of 39 meq/100 g for k10 and 85 meq/100 g for MMT-Na is calculated. To optimize the Fe(II) adsorption on clays, pH, clay mass, and contact time were studied. The adsorption isotherms were analyzed using linear and nonlinear Langmuir, Freundlich, Dubinin-Radushkevich, Sips, and Toth isotherms. A study of adsorption kinetics was conducted using linear, nonlinear, and differential pseudo first and second orders. An Elovich model has been applied to the obtained data about chemisorption character. Boyd and Weber& Morris's intraparticle diffusions have also been examined. Upon adsorption of Fe(II) on all clays, the standard free energies were negative, confirming the spontaneous nature of the adsorption process. As a result of the endothermic nature of the adsorption, the enthalpies are positive. In the presence of other cations, k10-phen and MMT-phen demonstrated the most excellent selectivity in uptaking Fe(II).

Engineered polymer–clay–copper oxides catalyst for the oxidation and reduction of organic molecules: synergy of degradation and instinctive interface stability by polymer self-healing function

Although many applications of clay–polymer composites have been suggested in recent years, their potential use in water treatment processes has received relatively little attention. This study reports the synthesis, characterization, and application of supramolecular polymer–montmorillonite clay–copper oxide (MPC) as an efficient catalyst for the degradation of rhodamine B (RB), a model organic molecule (OM). MPC was synthesized by incorporating branched polyethyleneimine (PEI) into layered montmorillonite K10 (MK10) through a simple wet impregnation method, followed by the incorporation of a copper precursor and direct reduction of the metal precursor. The resulting MPC was characterized using ATR-FTIR, SEM-EDS, TEM, BJH, XRD, and SAXS. The results confirmed the incorporation of PEI and nano-copper oxides into MK10. The MPC chemically degraded RB (>99% at 5 mg L−1, pH 7) in the aqueous phase (10 mL), and the degradation followed a pseudo-second-order kinetic model with a high correlation coefficient. The synthesized MPC degraded RB (7 h) in the presence of H2O2 and adsorbed RB (>98%) without H2O2. The completeness of RB degradation was validated using liquid–liquid extraction and solid–liquid phase extraction of the aqueous phase and solid MPC after the degradation reaction, respectively. The degradation proceeded through reactive active species (hydroxide radical, •OH), which remained in the solution and are active for 72 h or more. This indicates that the synthesized MPC can degrade trace amounts of RB in larger aqueous volumes. PEI exhibited self-healing behavior (network remodeling) after by mechanical or chemical stress to the PEI/PEI-Cu species during RB degradation, which included the re-formation of RnN–Cu oxides as well as the synergistic effect of charge transfer/recombination between N, Cu, and other reactive species in the reaction mixtures. The post-degradation characterization of MPC confirmed that MPC could be reused for more than five cycles without the loss of copper species. The high catalytic performance of MPC towards the other four organic pollutants in the aqueous phase indicates that MPC is a promising environmental catalyst.

Kinetic and Chemical Effects of Clays and Other Fillers in the Preparation of Epoxy–Vinyl Ether Composites Using Radical-Induced Cationic Frontal Polymerization

Addition of fillers to formulations can generate composites with improved mechanical properties and lower the overall cost through a reduction of chemicals needed. In this study, fillers were added to resin systems consisting of epoxies and vinyl ethers that frontally polymerized through a radical-induced cationic frontal polymerization (RICFP) mechanism. Different clays, along with inert fumed silica, were added to increase the viscosity and reduce the convection, results of which did not follow many trends present in free-radical frontal polymerization. The clays were found to reduce the front velocity of RICFP systems overall compared to systems with only fumed silica. It is hypothesized that chemical effects and water content produce this reduction when clays are added to the cationic system. Mechanical and thermal properties of composites were studied, along with filler dispersion in the cured material. Drying the clays in an oven increased the front velocity. Comparing thermally insulating wood flour to thermally conducting carbon fibers, we observed that the carbon fibers resulted in an increase in front velocity, while the wood flour reduced the front velocity. Finally, it was shown that acid-treated montmorillonite K10 polymerizes RICFP systems containing vinyl ether even in the absence of an initiator, resulting in a short pot life.

Effects of the Inclusion of Ce and Ni Species on Ti for Modification of K10-Clay by Sol-Gel and their Use as Catalysts in the Liquid-Phase Esterification Systems

AbstractThe modification of montmorillonite with metallic species affects directly its crystalline structure, texture, porosity, and surface. The interaction of the metallic molecules with the clay matrix, derived from the modification pathway and the characteristics of the adsorbate, modifies the physicochemical properties of montmorillonite, enabling the creation of materials with varied characteristics to be used both as catalysts and adsorbents. Small amounts of metallic species can confer various structural and physicochemical characteristics on the same montmorillonite matrix, depending on the metal incorporated. The objective of the present study was to create an acid-base catalyst based on montmorillonite K10 (K10 Mnt), modified with Ti, Ce, and Ni, for the catalytic esterification of acetic acid and penta-1-ol. K10-Mnt was modified using particles of Ti and of Ti modified with Ce and Ni. The effect of the inclusion of Ti and modified Ti species on the transformation of the physicochemical properties of the K10 Mnt and their contributions to the catalytic esterification syntheses were investigated. Samples were characterized by scanning electron microscopy coupled to an energy-dispersive X-ray spectroscopy system (SEM-EDS), powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), physisorption of N2 at 77 K (BET and BJH), and thermogravimetric analysis (TGA-DTGA). Finally, the original and modified K10 Mnt samples were tested for their catalytic esterification of acetic acid and penta-1-ol in the liquid phase.

Azomethine ylide [3 + 2]-cycloaddition of 3-alkylidene-7-aza-2-indolone: Synthesis of 3,3′-dispiropyrrolidine- and 3,3′-dispiropyrrolizidine bis 7-aza-2-oxindoles

32 AY CA reactions of 3-alkylidene-7-aza-2-indalone with acyclic and cyclic AY’s generated in situ from 7-azaisatin/isatin and sarcosine/proline in the presence of Montmorillonite k10 clay afforded highly functionalized 3, 3′-dispiropyrrolidine- and 3,3′-dispiropyrrolizidine bis 7-aza and 2-oxindole in excellent yield. The structure of the representative cycloadducts was established by single-crystal XRD. A plausible reaction mechanism is provided. Significantly the final product forms with newly formed two quaternary spiro carbons and two stereogenic centers simultaneously.