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Alternative energy technologies are greatly hindered by significant limitations in materials science. From low activity to poor stability, and from mineral scarcity to high cost, the current materials are not able to cope with the significant challenges of clean energy technologies. However, recent advances in the preparation of nanomaterials, porous solids, and nanostructured solids are providing hope in the race for a better, cleaner energy production. The present contribution critically reviews the development and role of mesoporosity in a wide range of technologies, as this provides for critical improvements in accessibility, the dispersion of the active phase and a higher surface area. Relevant examples of the development of mesoporosity by a wide range of techniques are provided, including the preparation of hierarchical structures with pore systems in different scale ranges. Mesoporosity plays a significant role in catalysis, especially in the most challenging processes where bulky molecules, like those obtained from biomass or highly unreactive species, such as CO2 should be transformed into most valuable products. Furthermore, mesoporous materials also play a significant role as electrodes in fuel and solar cells and in thermoelectric devices, technologies which are benefiting from improved accessibility and a better dispersion of materials with controlled porosity.

Due to their unique properties, in recent years, ionic liquids (ILs) have been largely investigated in the field of analytical chemistry. Particularly during the last sixteen years, they have been successfully applied in the chromatographic and electrophoretic analysis of value-added compounds extracted from biomass. Considering the growing interest in the use of ILs in this field, this critical review provides a comprehensive overview on the improvements achieved using ILs as constituents of mobile or stationary phases in analytical techniques, namely in capillary electrophoresis and its different modes, in high performance liquid chromatography, and in gas chromatography, for the separation and analysis of natural compounds. The impact of the IL chemical structure and the influence of secondary parameters, such as the IL concentration, temperature, pH, voltage and analysis time (when applied), are also critically addressed regarding the achieved separation improvements. Major conclusions on the role of ILs in the separation mechanisms and the performance of these techniques in terms of efficiency, resolution and selectivity are provided. Based on a critical analysis of all published results, some target-oriented ILs are suggested. Finally, current drawbacks and future challenges in the field are highlighted. In particular, the design and use of more benign and effective ILs as well as the development of integrated (and thus more sustainable) extraction-separation processes using IL aqueous solutions are suggested within a green chemistry perspective.

A four-step one-pot procedure involving generation of α-bromo aluminum acetals, their subsequent radical cyclization followed by oxidation of the resulting cyclic aluminum acetals and base promoted double bond migration is developed to convert α-bromoesters derived from propargylic alcohols to butenolides.

Process intensification by using well-defined solid catalysts able to perform one-pot multistep reactions is one of the open fronts in heterogeneous catalysis. This is even more relevant if new, more efficient synthesis routes are open. Herein, a gold catalyst was used to synthesize benzimidazoylquinoxalines compounds by two efficient and selective novel methods in a multistep one-pot methodology. The first method involved the synthesis of benzimidazoylquinoxaline compounds with the same substituents in both heterocycles through oxidation–cyclization of glycerol with o-phenylenediamine derivatives, whereas the second one allowed the synthesis of benzimidazoylquinoxalines compounds with different substituents in each aromatic ring through coupling of o-phenylenediamine derivatives with glyceraldehyde in a first stage to produce the benzimidazol compound as an intermediate, followed by an oxidation–cyclization with another o-phenylenediamine compound in a second stage. Both stages were performed by using gold nanoparticles supported on nanoparticulated ceria (Au/CeO2) as the catalyst and air as the oxidant, in absence of any homogeneous reagent. A reaction mechanism has been proposed.

The photoreactivity of allyl benzoates, containing an electron-rich double bond, has been explored by irradiation at 305 nm in different solvents. Solvent addition products arising from an insertion of the alpha H–C bonds of THF, dioxane, and i-PrOH to the allylic double bond was realized. The observed reactivity depended on reaction conditions and substitution pattern of the substrate. A DFT study on this unusual reaction was performed allowing the formulation of two mechanistic pathways.

Bismuth(III) salts are currently considered efficient and “ecofriendly” reagents and catalysts for the development of new applications in organic synthesis. The preparation of bismuth(III) triflate and its analogues is reviewed as well as some of their applications to the synthesis of bulk chemicals via electrophilic addition and cyclization reactions. The use of bismuth(III) salts in the development of new chemical processes involving steroids and terpenes as substrates is also discussed.

This is the first report of the rearrangement of 1,2,4-oxadiazole with saturated C—C—O side chains and an unusual example of an irreversible rearrangement that allows the formation of nonaromatic heterocycles.

Highly substituted 4,4′-biimidazoles were synthesized, in good to excellent yields, through a multicomponent imidazole ring synthesis by using imidazol-4-yl-ethane-1,2-diones as starting materials. The obtained compounds were preliminarily tested as chromogenic and fluorescent sensors for heavy metals.

Two novel thermal rearrangements are presented: the addition of allylamine (II) to oxadiazoles proceeds via ring-opening followed by cycloaddition.

The reaction must be carried out under nitrogen atmosphere in deoxygenated solvent to prevent the oxidation of the imidazole products.

The hydrazinolysis of the oxadiazoles under optimized conditions allows a general synthesis of functionalized aminotriazole products which are of interest due to the biological activity of the heterocyclic system.

A new variation on the Boulton-Katritzky reaction is reported, namely, involving use of a CNC side chain. A novel Montmorillonite-K10 catalyzed nonreductive transamination of a 3-benzoyl-1,2,4-oxadiazole afforded a 3-(alpha-aminobenzyl)-1,2,4-oxadiazole, which was condensed with benzaldehydes to afford the corresponding imines. In the presence of strong base, these imines underwent Boulton-Katritzky-type rearrangement to afford novel 4(5)-acylaminoimidazoles.

Some mechanistic investigations on the photochemical behaviour of 1,2,4-oxadiazoles are reported. Irradiation of 3-benzoylamino-5-methyl-1,2,4-oxadiazole at λ= 254 nm in methanol involves excitation of the benzoylamino group chromophore to a triplet state species and induces a 6π electrocyclic closure to a tricyclic intermediate. On the other hand, irradiation of 3-acetylamino-5-phenyl-1,2,4-oxadiazole at λ= 254 nm involves excitation of a 5-phenyl-substituted oxadiazole chromophore which leads to the photolysis of the ring O–N bond in a singlet state species. Furthermore, irradiation of some selected 5-phenyl substituted oxadiazoles in the presence of a triplet sensitizer produces an excited triplet state species which collapses in a ring closure reaction involving the C5-phenyl moiety.

The photochemical behaviour of some substituted aldehyde thiosemicarbazones 1a-k has been investigated in methanol at 254 nm. Thiosemicarbazones of glyoxil methyl ester 1a-f cyclized to furnish the 3-thioxo- 1,2,4-triazin-5-one 2 ring system. The remaining thiosemicarbazones 1g-j gave 1,2,4-triazoline 4 derivatives.

A series of 2-aryloxycarbonylthiophene-3-sulfonamides were synthesized and evaluated to determine their antagonistic activity at the endothelin receptors. N-(4-chloro-3-methyl-5-isoxazolyl)-2-[(3,4-methylenedioxy)phenoxycarbonyl]thiophene-3-sulfonamide was identified as a highly selective, potent (IC 50 = 8.3 nM) and low molecular weight nonpeptide antagonist.

The synthesis and structural characterization of several benzylic derivatives of 3-exo-hydroxy-1,8-cineole is described. The new compounds show antimicrobial activity against Cladosporium cucumerinum, Staphylococcus aureus, Mycobacterium smegmatis, Pseudomonas aeruginosa, and Candida albicans.

The photochemistry of some 5-aryl-3-methoxy- (or 5-aryl-3-phenyl-) 1,2,4-oxadiazoles irradiated in the presence of different sensitizers [such as diphenylacetylene (DAC), 9,10-diphenylanthracene (DAN), or triphenylene (TPH)] or ground-state donors such as triethylamine (TEA) has been investigated. Intermediates arising from breaking of the ring O-N bond develop both into quinazolin-4-ones (by a heterocyclization reaction involving the aryl at the C-5 of the oxadiazole nucleus) and into open-chain products (corresponding to a reduction at the ring O-N bond), in different ratios depending on their structures and photoreaction conditions. A reasonable explanation considers sensitization by photoinduced electron transfer either from the sensitizer in its excited state to the oxadiazole in its ground state or from the electron donor reagent (TEA) to the excited oxadiazole; in both cases an oxadiazole radical anion is formed as a key species from which breaking of the ring O-N bond takes place. Reduction potentials of representative oxadiazoles confirm this hypothesis. Possible applications in the synthesis of variously substituted quinazolin-4-ones are recognized.

Irradiation of 2-methyl-4-phenyl- substituted benzaldehyde thiosemicarbazones led with good yields to the corresponding Δ2-1,2,4-triazoline-5-thione derivatives through the formation of stable 1,2,4-triazolidine-5-thione intermediates. The relative quantum yields of photocyclization at 313 nm were analysed by means of the Hammett equation and ρ values determined. We interpreted the results in terms of the mechanism of photocyclization of 2-methyl-4-phenyl-substituted benzaldehyde thiosemicarbazones.

The ring-photoisomerization of 3-amino- and 3-methylamino-5-phenyl-1,2,4-oxadiazoles into the corresponding 2-amino- and 2-methylamino-5-phenyl-1,3,4-oxadiazoles has been reinvestigated by examining the effect of a base on the photoreaction. On irradiating at λ = 254 nm in methanol, yields of the ring-photoisomers were found to be significantly enhanced by the addition of triethylamine (TEA) in the photoreaction medium. By contrast, irradiation of the 3-amino-5-phenyloxadiazole in acetonitrile containing TEA gave an almost complete photoreduction into benzoylguanidine, while few percent of the ring photoisomer were detected. Furthermore, the pyrene-sensitized photolysis of 3-amino-5-phenyloxadiazole in acetonitrile containing triethylamine also gave benzoylguanidine but no traces of the ring photoisomer.

A photochemical methodology for the synthesis of 3-amino- (or 3- N -substituted amino) 5-pentafluorophenyl-1,2,4-oxadiazoles is reported. Irradiation of 3-pentafluorobenzoylamino-4-methyl-1,2,5-oxadiazole (Furazan) at 254 nm in methanol and in the presence of ammonia, primary or secondary aliphatic amines produces 3-amino-, 3-( N -alkylamino)-, 3-( N , N -dialkylamino)-5-pentafluorophenyl-1,2,4-oxadiazoles. The photoreaction follows the fragmentation pattern of the furazan ring with the extrusion of acetonitrile and the formation of a counterpart fragment which the nitrogen nucleophile will capture. Depending on the nature of the reagent, displacement of a fluoride anion at the C(5)-pentafluorophenyl moiety of the first-formed oxadiazoles by the nitrogen nucleophile and/or the solvent also takes place. By the same photochemical approach, the synthesis of the 3-methoxy-5-pentafluorophenyl-1,2,4-oxadiazole is also described.

Irradiation of the nor-diterpene atractyligenin at λ =254 nm in methanol gave, on one hand, the decarboxylation product, and provided, on the other hand, the transformation of the C-20 angular methyl into a methylene-carbomethoxy group. A photochemical pathway involving formation of C-19/C-20 bond is suggested.

A number of novel 3',4'-fused dioxolane and dioxane sordarin derivatives were synthesised for structure-activity relationship studies. Many of these derivatives exhibit high activity against Candida spp. and Cryptococcus neoformans.

Starting from a 3,5-dihydroxyheptanoic acid derivative, a new synthesis of pyrrole statins that contain a double bond on the dihydroxyacid chain has been developed. Key steps are N-acylamino acid enamide formation through enamine trapping with aromatic acyl chlorides and subsequent munchnone cycloaddition with activated acetylenes.

During the last few years, biodegradable polymers have been developed to replace petrochemical polymers. Until now, research devoted to these polymers essentially focused on their biodegradability. There is now a need to bear out their nontoxicity. To verify this, the biodegradation must be carried out in accelerated laboratory tests which allow the metabolites and residues to be recovered. To reproduce the natural conditions (compost, field) as closely as possible, degradation experiments must be run on solid-state substrates. We review studies of aerobic degradation in solid-state substrates. This article focuses in particular on the environmental, physical, and chemical parameters (such as substrate nature, moisture, temperature, C/N ratio, and pH) that influence biodegradation kinetics. This study also aims at finding the solid substrate most adapted to residues and metabolite recovery. The most significant parameters would appear to be the substrate type, moisture content, and temperature. Inert substrates such as vermiculite are well suited to residue extraction. This review also opens the field to new research aimed at optimizing conditions for aerobic solid-state biodegradation and at recovering the metabolites and residues of this degradation process.

In this review recent uses of the inexpensive and commercially available bismuth(III) salts in organic chemistry will be highlighted. Their application to the development of new processes or synthetic routes that lead to compounds of pharmaceutical interest will be matter of discussion. It will focus on bismuth(III) salt-mediated reactions involving the preparation of non-heterocyclic compounds such as aliphatics and alicyclics, monocyclic and polycyclic aromatics, amino acids and peptides, terpenes and steroids.

The thermal rearrangement of N-1,2,4-oxadiazol-3-yl-hydrazones into 1,2,4-triazole derivatives is reported. This represents the first example of a three-atom side-chain rearrangement involving an NNC sequence linked at the C(3) of the oxadiazole. The reactions carried out under solvent-free conditions produced good to high yields of the final products.

Fluoroalkylated 2-ylamino-imidazoles have been synthesized by reaction of 3-amino-5-phenyl-1,2,4-oxadiazole with fluorinated β-dicarbonyl compounds and subsequent base-induced Boulton–Katritzky Rearrangement (BKR) of the isolated β-enaminocarbonyl intermediate. Alternatively, one-pot reactions performed in the presence of Montmorillonite K10 favoured the condensation at the 3-amino moiety of the oxadiazole and, in some cases, allowed the direct synthesis of 2-benzoylamino-imidazoles. Hydrolysis of 2-benzoylamino-imidazoles easily yielded fluorinated 2-amino-imidazoles targets.