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In the field of green chemistry, micellar catalysis plays a central role for organic solvent replacement. Micelles ensure the solubilization or dispersion of catalyst and organic substrates in water imparting unique features in terms of chemo-, regio- and stereoselectivity. For metal-catalyzed reactions, a more robust approach for catalyst recycling consists in the synthesis of so-called metallosurfactants, in which a hydrophilic metal–containing headgroup is endowed with a hydrophobic ponytail, leading in water to the formation of metallomicelles. This fast-growing field of research is critically reviewed in this contribution, describing new trends and classifying the literature since 2017 based on the nature of the newly formed bond. Particular emphasis is reported on the specific features of metallosurfactants in terms of activities, selectivities and recyclability of the self-assembling catalysts.

The use of readily prepared bisphosphonic acids obtained in few steps through a thio-Michael addition of commercially available thiols on tetraethyl vinylidenebisphosphonate enables the straightforward surface modification of amorphous mesoporous zirconia nanoparticles. Simple stirring of the zirconia nanoparticles in a buffered aqueous solution of the proper bisphosphonic acid leads to the surface functionalization of the nanoparticles with different kinds of functional groups, charge and hydrophobic properties. Formation of both chemisorbed and physisorbed layers of the bisphosphonic acid take place, observing after extensive washing a grafting density of 1.1 molecules/nm2 with negligible release in neutral or acidic pH conditions, demonstrating stronger loading compared to monophosphonate derivatives. The modified nanoparticles were characterized by IR, XPS, ζ-potential analysis to investigate the loading of the bisphosphonic acid, FE-SEM to investigate the size and morphologies of the nanoparticles and 31 P and 1 H MAS NMR to investigate the coordination motif of the phosphonate units on the surface. All these analytical techniques demonstrated the strong affinity of the bisphosphonic moiety for the Zr(IV) metal centers. The functionalization with bisphosphonic acids represents a straightforward covalent approach for tailoring the superficial properties of zirconia nanoparticles, much straightforward compared the classic use of trisalkoxysilane or trichlorosilane reagents typically employed for the functionalization of silica and metal oxide nanoparticles. Extension of the use of bisphosphonates to other metal oxide nanoparticles is advisable.

In recent years, the issue of coral bleaching has led to restrictions in some tropical locations (i.e., Palau, Hawaii, etc.) on the use of some organic UV sunscreen filters, such as oxybenzone and ethyl hexyl methoxycinnamate. In contrast, ZnO is considered safe for marine environments and thus is often used without considering its photocatalytic and oxidative activities related to the generation of O2•− and HO•. Moreover, ZnO needs to be used in combination with other filters to reach higher protection factors. Thus, the study of its interaction with formulations and with organic filters is important in sunscreen technology for the development of safer by-design products. In this work, the photocatalytic activity of zinc oxides with different surface areas (30, 25 and 9 m2/g) and their interaction with selected organic sunscreen filters were investigated. In particular, the ZnO photocatalytic kinetics were studied following the photodegradation of Acid Blue 9 (AB9) observing a first-order reaction with a chemical regime. Our evaluations of the selective inhibitions by hvb+ and HO• demonstrated a substantial predominance of the hydroxide radicals in the expression of the photocatalysis, a trend that was also confirmed by the irradiation of ZnO in an ethanolic solution. Indeed, the formulations containing both ZnO and organic filters defined as “safe” for coral reefs (i.e., Diethylamino Hydroxybenzoyl Hexyl Benzoate, DHHB, and Ethylhexyl Triazone, EHT) showed a non-negligible photocatalytic oxidation and thus the combination was underlined as safe to use.

The hexameric resorcin[4]arene capsule as a self-assembled organocatalyst promotes a series of reactions like the water elimination from 1,1-diphenylethanol, the isomerization of α-pinene and β-pinene preferentially to limonene and minor amounts of camphene, and the carbonyl-ene Prins cyclization of (S)-citronellal preferentially to isopulegol. The role of the supramolecular catalyst consists in promoting the protonation of the substrates leading to the formation of cationic intermediates that are stabilized within the cavity with consequent peculiar features in terms of acceleration and product selectivity. In all cases the catalytic activity displayed by the hexameric capsule is remarkable if compared to many other strong Brønsted or Lewis acids

In this contribution, we report about the synthesis, the aggregation properties and their application in cross-coupling catalysis of two new designer surfactants comprising a rigid hydrophobic portion based on β-sitosterol directly linked by an etheric bond to methyl polyoxoethylene chains. The proposed amphiphilic compounds represent a minimalistic approach with respect to the Lipshutz's third generation designer surfactant Nok. The amphiphiles displayed improved chemical stability, shorter synthesis, and good properties in Pd-catalyzed cross-coupling reactions in water under mild conditions, as compared with other neutral commercially available surfactants.

Replacement of organic solvents, in particular chlorinated, aromatic, and polar aprotic ones, is an emerging issue that can find a solution in the development of catalytic reactions in water. Nature performs a multitude of chemical transformations in water under mild conditions mediated by enzymes. In particular the nanoconfinement effects of the enzymes ensure high activity and impressive stereoselectivities. Micellar catalysis is nowadays a real alternative approach to catalysis in traditional organic media, enabling good activity under mild conditions, with the advantage of possible catalyst and micellar medium recycling. Micellar media emerged also as good nano-environments for stereoselective reactions, with many examples of chemical transformations mediated by metal and organo-catalysts for which improvements of stereoselectivity were observed with respect to the same reaction under homogeneous conditions in traditional organic solvents. More specifically, both the catalytically active site and the micelles provided by the surfactant can contribute to the asymmetric induction, partially resembling what known in terms of stereoselectivity imparted by the active site of enzymes and metallo-enzymes.

The hexameric resorcin[4]arene capsule as a self-assembled organocatalyst promotes a series of reactions like the carbonyl–ene cyclization of (S)-citronellal preferentially to isopulegol, the water elimination from 1,1-diphenylethanol, the isomerization of α-pinene and β-pinene preferentially to limonene and minor amounts of camphene. The role of the supramolecular catalyst consists in promoting the protonation of the substrates leading to the formation of cationic intermediates that are stabilized within the cavity with consequent peculiar features in terms of acceleration and product selectivity. In all cases the catalytic activity displayed by the hexameric capsule is remarkable if compared to many other strong Brønsted or Lewis acids.

Surfactant is a special kind of amphiphilic compound composed of water-loving and hating parts. The remarkable physical properties like interfacial tension, wettability, emulsifying and dispersing ability make the surfactant accessible for numerous applications from laboratory to commercial products. In recent years, the commercial applications of surfactant have led to greater relevance on account of the environmental concerns and market pressures of this compound. The utility of surfactants in global market increases steadily since its formulation with several beneficial aspects in pharmaceutical, detergent, cosmetic, paint, food science, gas hydrate, nanotechnology, petroleum recovery, bioremediation, chemical transformation and drug delivery. This review briefly discusses the applied aspect of surfactants in diverse area as well as catalytic effect of micelle in organic reactions from the recent literature survey. The trend of increasing use of bioderived surfactants in the modern field of research is also considered in this report. The recent advancement of surfactant-based organic transformations has been emphasized with the role of surfactant aggregates in course of different organic reactions.

The synthesis of a conjugate molecule between an unusual red-fluorescent diketopyrrolopyrrole (DPP) unit and a bis-phosphonate (BP) precursor by a click-chemistry strategy to target bone tissue and monitor the interaction is reported. After thorough investigation, conjugation through a triazole unit between a γ-azido rather than a β-azido BP and an alkyne-functionalized DPP fluorophore group turned out to be the winning strategy. Visualization of the DPP-BP conjugate on osteoclasts and specific antiresorption activity were successfully demonstrated.

Herein we present the synthesis of β-mono and β-bis-substituted vinylidenebisphosphonate esters bearing a carboxylic ester moiety to be used as building blocks for further functionalizations. Reactions of these new bisphosphonate scaffolds through hydrogenation of the unsaturated CC bond and through metal mediated addition of aryl boronic acids and indoles provide a wide range of new bisphosphonate products as potential leads to contrast osteoporosis.

Drug delivery systems have been a milestone in medical research in the last twenty years, still representing a key aspect of innovation and evolution in pharmacokinetics and pharmacodynamics. Among several proposed solutions, inorganic mesoporous materials could be a promising vehicle. Their specific chemical-physical properties make them ideal candidates for the adsorption and loading of active pharmaceutical ingredients (API). Recently, mesoporous zirconia nanoparticles (MZNs) have been described as a novel drug delivery system due to their high surface area and biocompatibility. In this work, we investigated the loading and release efficiencies of a wide range of API on MZNs characterized by suitable pore volume and versatility, focusing on the integrity of the released drugs investigated through solution NMR and ESI-MS techniques. In order to explore the potentialities of MZNs for biomedical applications, we selected ibuprofen, N-acetyl- l -cysteine, vancomycin, gentamicin, nitrofurantoin, and indomethacin as benchmark API characterized by a wide range of polarity, molecular weight and presence of different functional groups. MZNs showed to efficiently load and release most of the API investigated. Long time loadings were also investigated observing that, after more than three months, no side reaction occurred on the released drugs except for intrinsically more labile API like NTF and NAC. MZNs ensured high inertness towards a wide range of functional groups such as aliphatic and aromatic amides, acetals of sugar residues as well as several chiral moieties bearing tertiary stereocenters.

The total syntheses of three C37 methyl-alkenones with different degrees of unsaturation and of their 13C-labelled analogues from commercially available starting materials are presented herein for the first time. These molecules are important to improve the reliability of the measurements and reconstructions of the sea surface temperature and salinity.

The use of water as a solvent for chemical transformations and catalysis is not only a counter-intuitive original approach with respect to catalysis in traditional media, but thanks to micellar catalysis and the recent development of new designer surfactants, it is becoming an important real benchtop alternative to the employment of organic solvents. Micellar catalysis has received new focus thanks to the recent introduction of the so-called designer surfactants by the group of Lipshutz as surfactants specifically designed and tested for catalysis in water. In particular, the advent of the benchmark TPGS-750-M has really revolutionized chemical synthesis and catalysis in aqueous media, leading also to important positive outcomes suitable for industrial scale applications. The present contribution covers the preparation and the applications in chemical transformations and catalysis of very recent new designer surfactants. These are readily available and economic amphiphiles, mostly prepared from renewable resources, that are specifically designed and tested for catalytic reactions in water. In particular, different neutral designer surfactants are covered and critically classified and discussed.

We report the synthesis and preliminary evaluation of (1S,2S,4R)-7,7-dimethyl-1-phenylbicyclo[2.2.1]heptan-2-ol 1a, which was obtained in 3 steps from inexpensive starting materials, as a chiral auxiliary. The potential for asymmetric induction was investigated by carrying out aza-Diels-Alder reactions with cyclopentadiene and imine derivatives of 1a from (R)-(+)-1-phenylethylamine, (S)-(−)-1-phenylethylamine and benzylamine. The results showed marked exo selectivity and good diastereoisomeric excess when 1a was combined with (R)-(+)-1-phenylethylamine. These results are comparable with those reported using (−)-8-phenylmenthol, suggesting that 1a can represent an economically viable alternative to current chiral auxiliaries.

In the field of nanomaterials, multifunctional nanosystems play a prominent role in many applications as new magnetically recoverable catalysts, information processing, fuel cells, efficient bio/na...

C 3-Symmetric tris-benzyl-O-substituted hexahydroxytriphenylene (HHTP) was prepared through selective ring opening with DIBAL-H in 48% yield (38% from HHTP in a two-step synthesis) avoiding the use of noxious, expensive and limited market availability reagents, with complete recovery of the undesired Cs co-product that is quantitatively recovered and converted back into HHTP. The C3-symmetric triphenylene product was further functionalized through substitution, deprotection and Mannich condensation reactions affording a series of C3-symmetric functionalized scaffolds in good yields for supramolecular applications.

Unconventional life forms based on membranes able to self-assemble in hydrocarbons instead of water might in principle exist in the hydrocarbon-rich environments on Earth and in the methane lakes of Saturn's moon, Titan. This reversed paradigm for life would require that these membranes should be constituted of “reverse” surfactants. We here describe the synthesis of reverse amphiphilic molecules with a geometry similar to conventional surfactants but with an opposite topological configuration: lipophilic heads and lipophobic tails. Their self-assembly in cyclohexane was studied by 1H 2D DOSY-NMR and SAXS. We present experimental evidence of the self-assembly of these reverse surfactants to yield typical micelles in a hydrocarbon solvent.

Micellar media in water provide a simple and efficient environment to favor the double bond isomerization of terminal alkenes catalyzed by the cationic half-sandwich complex 1 at 95 °C. The micellar medium favors both catalyst dissolution in water by means of ion-pairing with the preferred anionic surfactants as well as substrate dissolution thus favoring its conversion into products.

Over the past few years, micellar catalysis with transition metal complexes has become a major tool in the hands of synthetic organic chemists and an important ‘green’ technology as it allows the use of water as the reaction medium. The range of reactions in which micellar media can be successfully used is already very wide. The use of micelles can improve the yield, selectivity at all levels (chemo-, regio-, enantio-), reaction conditions, product separation, and catalyst recycling. The surfactant choice is a key issue that, for specific cases, can be optimized with especially designed surfactants and metallo-surfactants. Practical examples provide some metrics demonstrating that micellar catalysis can indeed reduce the E-factor and, in the industrial practice, also improve yields, decrease energy consumption, shorten cycle times, and ultimately production costs. In short, catalysis in micellar media is much ahead of a mere green chemistry promise and can already be considered a profitable industrial opportunity.

The synthesis of pillar[5]arenes from p-dialkoxybenzene and formaldehyde in the presence of iron(III) chloride and tetramethylammonium chloride under mild reaction conditions was investigated in detail. For the first time, the presence of linear intermediate oligomers and their conversion into pillar[6]arenes was demonstrated. Incorporation experiments were carried out using methoxy- and ethoxy-functionalized pillar[5]arenes that were reacted respectively with 1,4-diethoxy- and 1,4-dimethoxybenzene, observing the formation of the corresponding co-pillar[6]arene derivatives, PMe[5]Et[1] and PEt[5]Me[1]. An experiment in which methoxy- and ethoxy-functionalized pillar[5]arenes were reacted together led to the major formation of scrambled P[5] derivatives characterized by a bell shape distribution of ethoxy and methoxy aromatic units. Co-Pillar[6]arenes P[6] were also detected by ESI-MS in minor amounts with a similar symmetrical distribution of substituents that allowed the proposal of multiple cleavage events occurring on the same macrocyclic ring forming in solution a series of smaller fragments, whose recombination leads to the observed product distribution of P[5] and P[6] derivatives.

C3-symmetric pyridine containing tris-benzyl-O-substituted hexahydroxytriphenylene derivatives were prepared and used in combination with square-planar Pd(II) and Pt(II) complexes for the self-assembly of molecular cages in solution. The formation of a trigonal bipyramid M3L2 cage was demonstrated by multinuclear NMR analyses and pseudo 2D DOSY experiments and supported by semi-empirical calculations.

An alternative approach is reported for the synthesis of methyl ester protected bisphosphonate building blocks, such as methylene bisphosphonate, vinylidenebisphosphonate and aryl substituted prochiral vinylidenebisphosphonates, that cannot be obtained directly from dimethyl phosphite and dichloromethane.

An efficient metal-free organocatalytic activation of hydrogen peroxide (H2O2) towards thioethers leading to the corresponding sulfoxides in high yields at room temperature within hours was promoted by the hexameric capsule formed by the self-assembly of resorcin[4]arene units. The capsule plays a dual role of activating the oxidant through hydrogen bonding and favouring the oxidation reaction inside the cavity. Inactivation of the supramolecular organocatalyst was observed by using competitive ammonium guests, mimicking the inactivation of enzymes by competitive inhibitors.

The isomerization of epoxides to the corresponding carbonyl compounds is efficiently catalyzed by the supramolecular organic nano-capsule formed by the self-assembly of six resorcin[4]arene units. The capsule provides a combination of weak Bronsted acidity and a suitable nano-environment that favors the metal-free isomerization reaction.

The combination of a Bronsted acid catalyst and a supramolecular organic capsule formed by the self-assembly of six resorcin[4]arene units efficiently promotes the mild hydration of aromatic alkynes to their corresponding ketones. The capsule provides a suitable nanoenvironment that favors protonation of the substrate and addition of water.

We report a facile, inexpensive, and green method for the preparation of Pd nanoparticles in aqueous medium stabilized by anionic sulfonated surfactants sodium 1-dodecanesulfonate 1a, sodium dodecylbenzenesulfonate 1b, dioctyl sulfosuccinate sodium salt 1c, and poly(ethylene glycol) 4-nonylphenyl-3-sulfopropyl ether potassium salt 1d simply obtained by stirring aqueous solutions of Pd(OAc)2 with the commercial anionic surfactants further treated under hydrogen atmosphere for variable amounts of time. The aqueous Pd nanoparticle solutions were tested in the selective hydrogenation reactions of aryl-alcohols, -aldehydes, and -ketones, leading to complete conversion to the deoxygenated products even in the absence of strong Bronsted acids in the reduction of aromatic aldehydes and ketones, in the controlled semihydrogenation of alkynes leading to alkenes, and in the efficient hydrodechlorination of aromatic substrates. In all cases, the micellar media were crucial for stabilizing the metal nanoparticles, dis...

Micellar media in water provide a simple and efficient environment favoring the multi-component synthesis of 1,2,3-triazoles from organic bromides, sodium azide and terminal alkynes in the presence of [Cu(IMes)Cl] 1 catalyst at room temperature within a few hours. The micellar medium favors both the in situ formation of the organic azide and its metal promoted cycloaddition with the alkyne.

Diazoacetate esters proved to be suitable neutral guests for the self-assembled resorcin[4]arene hexameric capsule. The hydrogen-bonded supramolecular host catalyzed the 1,3-dipolar cycloaddition reaction between diazoacetate esters and electron-poor alkenes such as acrolein, acrylonitrile, predominantly trans-crotonaldehyde, trans-2-hexenal, methyl, and butyl acrylate, which led to the corresponding 4,5-dihydro-1H-pyrazole derivatives. The cycloaddition reaction occurred within the cavity of the capsule. In fact, substantial inhibition of the catalytic activity was observed by employing tetraethylammonium tetrafluoroborate characterized by greater affinity for the hexameric capsule as a competitive guest; its presence inhibited access of the substrates. The 1,3-dipolar cycloaddition reaction between diazoacetate esters and acrylate esters of different lengths showed a significant degree of substrate selectivity owing to the encapsulation of the reagents before the cycloaddition reaction.

The synthesis of a new class of epoxide derivatives from prochiral vinylidene bisphosphonate (VBP) precursors is reported using hydrogen peroxide as the terminal oxidant. The reaction is carried out using a series of possible organic catalysts having a basic character, the best results being observed using quinine and sparteine. These catalysts not only provide from good to excellent epoxide yields with a large variety of VBPs but also interesting enantioselectivities in the 67-96% ee range at least in the case of the Ph and m-MeO-Ph VBP derivatives opening the way to a number of chiral anti-osteoporosis potentially active pharmaceutical ingredients.

The synthesis of a new class of epoxide derivatives from prochiral vinylidene bisphosphonate (VBP) precursors is reported using hydrogen peroxide as the terminal oxidant. The reaction is carried out using a series of possible organic activators having a basic character, with the best results being observed using quinine and sparteine. These activators not only provide from good to excellent epoxide yields with a large variety of VBPs, but also interesting enantioselectivities in the 67%–96% ee range, at least in the case of the Ph and m-MeO–Ph VBP derivatives, opening the way to a number of chiral anti-osteoporosis potentially active pharmaceutical ingredients.

A hundred-fold substrate selectivity was observed in the competitive chemoselective hydrogenation of seven α,β-unsaturated aldehydes from C4 to C10 in water with palladium nanoparticles stabilized by sodium dodecyl sulfonate as the surfactant. The medium makes the longer lipophilic substrates hundreds of times more reactive than the shorter more hydrophilic ones, whereas in an organic medium almost no difference is observed.

Significant substrate selectivity was observed in the competitive Heck coupling reaction, between iodoaryl substrates and five acrylate esters from methyl to lauryl with Pd(OAc)2 in water, under cationic micellar conditions. While in organic medium the shorter acrylate reacts faster than the longer ones, the opposite trend is observed in the micellar medium because the latter hosts the longer, lipophilic substrates much better than the shorter ones.

The synthesis of enantiopure (+)-benzotricamphor syn-5, an important chiral C3-symmetric rigid building block for supramolecular applications, was studied in detail to reduce the number of steps and to increase the diastereoselectivity and overall yield. The new synthetic procedure allowed larger amounts of syn-5 to be obtained and used for the preparation of new derivatives, such as the corresponding tris-trifluoromethanesulfonate syn-12, which was efficiently transformed into (+)-benzotribornenetrinitrile syn-1 and (+)-benzotribornenetris(ethynyl-4-pyridine) syn-2. The previously reported (+)-benzotricamphortrioxime syn-6 was transformed into tris-nitrile syn-3 by Beckman reaction. Compounds syn-1-3 were employed as multidentate ligands for silver(I) and platinum(II) centres in apolar solvents. The linear coordination geometry of Ag(I) and square-planar geometry of cis-chelated Pt(II) in combination with the chiral tripodal ligands syn-1-3 led to the formation of chiral enantiopure capsules with M3 L2 stoichiometry, as confirmed by 2D NMR NOESY and DOSY experiments as well as ESI mass spectrometry.