The use of copper(0) nanoparticles in the transfer semihydrogenation of alkynes has been investig... more The use of copper(0) nanoparticles in the transfer semihydrogenation of alkynes has been investigated as a lead-free alternative to Lindlar catalysts. A stereo-selective methodology for the hydrogenation of internal alkynes to the corresponding (Z)-alkenes in high isolated yields (86% average) has been developed. This green and sustainable transfer hydrogenation protocol relies on non-noble copper nanoparticles for reduction of both electron-rich and electron-deficient, aliphatic-substituted and aromaticsubstituted internal alkynes. Polyols, such as ethylene glycol and glycerol, have been proven to act as hydrogen sources, and excellent stereo-and chemoselectivity have been observed. Enabling technologies, such as microwave and ultrasound irradiation are shown to enhance heat and mass transfer, whether used alone or in combination, resulting in a decrease in reaction time from hours to minutes.
See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published art... more See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles. Figure 2. MW resonator flow concept obtained by combining monoand multimode technologies. Reproduced with permission from ref 22.
The aim of this review is to provide an overview of green protocols for the organic synthesis of ... more The aim of this review is to provide an overview of green protocols for the organic synthesis of heterocycles via 1,3-dipolar cycloaddition. Particular attention has been devoted to the use of green solvents; reactions performed in ionic liquids, fluorinated solvents and water have been included. Also explored are several protocols that make use of catalyst-free reaction conditions, the use of microwave irradiation and activation by light exposure. Improvements over commonly used organic solvents will be underlined in order to highlight environmental protection aspects and enhancements in regio-and stereo-selectivity.
The impressive chemico-physical effects observed in sonochemistry are a result of cavitation, as ... more The impressive chemico-physical effects observed in sonochemistry are a result of cavitation, as ultrasonic and hydrodynamic cavitation does not interact with matter at the atomic and molecular levels. Bubble collapse leads to the quasi-adiabatic heating of the vapour inside bubbles, giving rise to local hot spots in the fluid. Cavitation thus transforms a mechanical energy into high kinetic energy, which is released in very short bursts that are exploited for green process intensification. This paper reviews relevant applications of hydrodynamic and acoustic cavitation with the aim of highlighting the particular advantages that these phenomena offer to the intensification of green chemical processes. Emulsification, biodiesel preparation, wastewater decontamination, organic synthesis, enzymatic catalysis and extractions are discussed among others. As a comparison, hydrodynamic cavitation technique is more advantageous in dealing with process intensification at large-scale, as well as the enhancement of mass transfer and heat transfer, while ultrasonic cavitation technique is more convenient to operate, easier to control in the studies at lab-scale, and exhibits more efficient in producing active free radicals and inducing the cleavage of volatile compounds.
Mechanochemically promoted reduction of nitro and azido derivatives may be successfully performed... more Mechanochemically promoted reduction of nitro and azido derivatives may be successfully performed in stainless steel jars without catalyst addition.
A ppm-level Pd/Boemite catalyst has been prepared over 3-mm alumina beads and used for the select... more A ppm-level Pd/Boemite catalyst has been prepared over 3-mm alumina beads and used for the selective hydrogenation of alkynes in a continuous-flow reactor with two modes: closed-loop and flow-through. The...
The development of alternative, green solvents is an important and ongoing challenge. Our latest ... more The development of alternative, green solvents is an important and ongoing challenge. Our latest contribution to the field is the use of γ-valerolactone in aminocarbonylative coupling reactions for the clean synthesis of several 4(3H)-quinazolinones under microwave irradiation. The palladium-catalyzed, four-component carbonylative coupling reactions of o-iodoanilines, trimethyl orthoformate and a variety of amines have been carried out under CO pressure (2.5 bar). This protocol was found to be highly efficient and selective for 4(3H)-quinazolinones, which were isolated in good yields in the presence of two different, recyclable Pd catalysts which were prepared under ultrasound irradiation; a novel lead-free Pd/Boehmite catalyst and a β-cyclodextrin - cross linked Pd catalyst.
The impressive pharmacological properties shown by a number of coumarins have led to extraordinar... more The impressive pharmacological properties shown by a number of coumarins have led to extraordinarily large emphasis being placed on the design of more efficient and greener synthetic procedures to produce them.
The tosyl group (Ts) on 6 I-O-(p-toluenesulfonyl)--cyclodextrin has been substituted with haloge... more The tosyl group (Ts) on 6 I-O-(p-toluenesulfonyl)--cyclodextrin has been substituted with halogenides, nitrogen and sulfur nucleophiles under mechanochemical conditions and the reaction has been investigated in this work. The preparation of mono-substituted cyclodextrin (CD) derivatives, such as azido-, thioureido-, iodo-and thioethers, is shown to be more advantageous in a planetary ball mill (BM) than classic solution methods. All BM reactions
ABSTRACTSynthetic chemists are paying ever more attention to enabling technologies as a means to ... more ABSTRACTSynthetic chemists are paying ever more attention to enabling technologies as a means to opening the paths towards the double goal of achieving high efficiency and meeting green criteria. Non-conventional techniques that create unique environments which promote selective modification have been investigated by many as part of the search for more highly efficient synthetic derivatization of cyclodextrins (CD). A few optimized microwave-assisted protocols have so far been developed for the preparation of selective per-alkylated aminocyclodextrin. In this work, a series of β-CD derivatives, whose primary hydroxyls were all replaced by amino groups, has efficiently been synthesized from per-(6-iodo-6-deoxy)-β-CD via nucleophilic substitution with amines under microwave irradiation in closed vessel (N2 pressure). The reduction of per-(6-azido-6-deoxy)-β-CD to per-(6-amino-6-deoxy)-β-CD via catalytic hydrogenation has also been successfully carried out under dielectric heating.
Nowadays the application of cyclodextrin-assisted molecular encapsulation in foods offers many ad... more Nowadays the application of cyclodextrin-assisted molecular encapsulation in foods offers many advantages. Cyclodextrins, their derivatives and their cross-linked polymers can all improve the quality of food in storage, remove specific components and stabilize and increase the presence of components that are important for a healthy diet. The application of cyclodextrins and their complexes in packaging materials can help not only transport of previously nontransportable foods, but may also prevent, or at least decelerate, the spread of microbial infections. The number of publications, particularly analytical papers, on this matter is constantly increasing. Although the application of modern analytical methods and equipment allows for the quantitation of previously subjectively characterized parameters, bio-sensory methods are still important. The application of cyclodextrins in the nutraceutical industry has many advantages; however, some side effects connected with the inclusion complexation ability of these carbohydrates should lead scientists to study cases on an individual basis. Recent developments in the major fields of cyclodextrin related food research are herein summarized.
The ball-mill-based mechanochemical activation of metallic copper powder facilitates solvent-free... more The ball-mill-based mechanochemical activation of metallic copper powder facilitates solvent-free alkyne-azide click reactions (CuAAC). All parameters that affect reaction rate (i.e., milling time, revolutions/min, size and milling ball number) have been optimized. This new, efficient, facile and eco-friendly procedure has been tested on a number of different substrates and in all cases afforded the corresponding 1,4-disubstituted 1,2,3-triazole derivatives in high yields and purities. The final compounds were isolated in almost quantitative overall yields after simple filtration, making this procedure facile and rapid. The optimized CuAAC protocol was efficiently applied even with bulky functionalized β-cyclodextrins (β-CD) and scaled-up to 10 g of isolated product.
The modification and characterization of porous particles and matrices using cyclodextrins (CD) h... more The modification and characterization of porous particles and matrices using cyclodextrins (CD) has attracted a large amount of interest in recent years. In fact, CDs are at the heart of this study which aims to graft β-CD onto silica particles by means of efficient protocols and nonconventional energy sources. In particular, the use of microwave irradiation, benign reaction media and a solvent-free planetary ball mill has provided a high degree of grafting. The inclusive properties of β-CD grafted silica were tested with phenolphthalein and its sorption capacity with 2 methyl orange and both tests confirmed the efficiency of the grafting protocols. Samples were extensively characterized by TGA, elemental analysis, IR, BET and HRTEM. The green protocols herein reported can facilitate access to functionalized silica and pave the way to its use in novel applications.
The functionalization of single-walled carbon nanotubes (SWCNTs) via microwave-assisted grafting ... more The functionalization of single-walled carbon nanotubes (SWCNTs) via microwave-assisted grafting reactions enables efficient multidecoration in a single step.
Bridged cyclodextrin dimers and trimers, in which respectively two and three hydrophobic cavities... more Bridged cyclodextrin dimers and trimers, in which respectively two and three hydrophobic cavities lie in close proximity, display much higher binding affinities and molecular selectivities than do parent cyclodextrins (CDs). By joining βCD units with links inserted at different positions (2-2', 3-2', 6-2' or 6-2'-6'') and interposing spacers of different lengths and shapes, multicavity structures can be synthesized that are precisely tailored to fit specific guest molecules. This enzyme-mimicking strategy can also be used to generate stable supramolecular adducts. A series of CD dimers and trimers was prepared in good yields by carrying out the critical synthetic steps under power ultrasound (US) or microwave (MW) irradiation. Starting from CD azide and acetylenic derivatives we exploited an efficient MW-promoted Huisgen 1,3dipolar cycloaddition in the presence of Cu(I) salts. The resulting bridged CD derivatives gave stable adducts with magnetic-resonance-imaging contrast agents (MRI CAs) containing gadolinium(III) chelates. These inclusion complexes were found to be 2 to 3 orders of magnitude more stable than those formed by βCD and to be endowed with high relaxivity values.
substituted 6 I-VII -O-t-butyldimethylsilyl(TBDMS)-3 I-VII -O-ethyl-2 I-VII -O-methyl-cyclodextr... more substituted 6 I-VII -O-t-butyldimethylsilyl(TBDMS)-3 I-VII -O-ethyl-2 I-VII -O-methyl-cyclodextrin (MeEt-CD) and 6 I-VII -O-TBDMS-2 I-VII -O-ethyl-3 I-VII -O-methyl--cyclodextrin (EtMe-CD) were synthesised to evaluate the role of the substitution pattern in positions 2 and 3 on the enantioselectivity, in particular in view of their application to routine analysis in fast enantioselective gas chromatography (Es-GC). The chromatographic properties and enantioselectivities of the new derivatives were tested by separating the enantiomers of a series of medium-to-high volatility racemates in the flavour and fragrance field, and compared to those of the corresponding symmetrically substituted 6 I-VII -O-TBDMS-2 I-VII ,3 I-VII -O-methyl--CD (MeMe-CD) and 6 I-VII -O-TBDMS-2 I-VII ,3 I-VII -O-ethyl--CD (EtEt-CD), and were then applied to analysis of real-world essential oil (e.o.) samples. A new synthetic process including the sonochemical approach to obtain synthetic reproducibility and significant yields of the per-substituted derivatives with acceptable reaction times was developed. The results show that asymmetrically substituted methyl/ethyl CDs compared to the methyl or ethyl symmetrical derivatives in general provide better enantioselectivity in terms of both enantiomer resolution and number of separated chiral compounds, and show how the substitution pattern in positions 2 and 3 of the CD ring can influence the separation. Moreover, these new CD derivatives with better enantioselectivity are also shown to be very useful in routine analysis for the exhaustive control of samples containing several chiral characterizing markers in a single run.
The synthetic procedure and the characterization of the new amino derivatives of poly(oxa-pphenyl... more The synthetic procedure and the characterization of the new amino derivatives of poly(oxa-pphenylene-3,3-phtalido-p-phenylene-oxa-p-phenilene-oxyphenylene) (PEEK-WC) with various average degrees of substitution, is reported. The amino PEEK-WC was extensively characterised by using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis, differential scanning calorimeter, scanning electron microscopy, Elemental analyses, NMR, and viscosity meas-urements. The amino PEEK-WC shows different solubility in some solvents in comparison with the parent polymer, good thermal stability and is able to form membrane by means of the phase inversion technique. Amino PEEK-WC results to be quite reactive and can lead to further modification. V
The use of copper(0) nanoparticles in the transfer semihydrogenation of alkynes has been investig... more The use of copper(0) nanoparticles in the transfer semihydrogenation of alkynes has been investigated as a lead-free alternative to Lindlar catalysts. A stereo-selective methodology for the hydrogenation of internal alkynes to the corresponding (Z)-alkenes in high isolated yields (86% average) has been developed. This green and sustainable transfer hydrogenation protocol relies on non-noble copper nanoparticles for reduction of both electron-rich and electron-deficient, aliphatic-substituted and aromaticsubstituted internal alkynes. Polyols, such as ethylene glycol and glycerol, have been proven to act as hydrogen sources, and excellent stereo-and chemoselectivity have been observed. Enabling technologies, such as microwave and ultrasound irradiation are shown to enhance heat and mass transfer, whether used alone or in combination, resulting in a decrease in reaction time from hours to minutes.
See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published art... more See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles. Figure 2. MW resonator flow concept obtained by combining monoand multimode technologies. Reproduced with permission from ref 22.
The aim of this review is to provide an overview of green protocols for the organic synthesis of ... more The aim of this review is to provide an overview of green protocols for the organic synthesis of heterocycles via 1,3-dipolar cycloaddition. Particular attention has been devoted to the use of green solvents; reactions performed in ionic liquids, fluorinated solvents and water have been included. Also explored are several protocols that make use of catalyst-free reaction conditions, the use of microwave irradiation and activation by light exposure. Improvements over commonly used organic solvents will be underlined in order to highlight environmental protection aspects and enhancements in regio-and stereo-selectivity.
The impressive chemico-physical effects observed in sonochemistry are a result of cavitation, as ... more The impressive chemico-physical effects observed in sonochemistry are a result of cavitation, as ultrasonic and hydrodynamic cavitation does not interact with matter at the atomic and molecular levels. Bubble collapse leads to the quasi-adiabatic heating of the vapour inside bubbles, giving rise to local hot spots in the fluid. Cavitation thus transforms a mechanical energy into high kinetic energy, which is released in very short bursts that are exploited for green process intensification. This paper reviews relevant applications of hydrodynamic and acoustic cavitation with the aim of highlighting the particular advantages that these phenomena offer to the intensification of green chemical processes. Emulsification, biodiesel preparation, wastewater decontamination, organic synthesis, enzymatic catalysis and extractions are discussed among others. As a comparison, hydrodynamic cavitation technique is more advantageous in dealing with process intensification at large-scale, as well as the enhancement of mass transfer and heat transfer, while ultrasonic cavitation technique is more convenient to operate, easier to control in the studies at lab-scale, and exhibits more efficient in producing active free radicals and inducing the cleavage of volatile compounds.
Mechanochemically promoted reduction of nitro and azido derivatives may be successfully performed... more Mechanochemically promoted reduction of nitro and azido derivatives may be successfully performed in stainless steel jars without catalyst addition.
A ppm-level Pd/Boemite catalyst has been prepared over 3-mm alumina beads and used for the select... more A ppm-level Pd/Boemite catalyst has been prepared over 3-mm alumina beads and used for the selective hydrogenation of alkynes in a continuous-flow reactor with two modes: closed-loop and flow-through. The...
The development of alternative, green solvents is an important and ongoing challenge. Our latest ... more The development of alternative, green solvents is an important and ongoing challenge. Our latest contribution to the field is the use of γ-valerolactone in aminocarbonylative coupling reactions for the clean synthesis of several 4(3H)-quinazolinones under microwave irradiation. The palladium-catalyzed, four-component carbonylative coupling reactions of o-iodoanilines, trimethyl orthoformate and a variety of amines have been carried out under CO pressure (2.5 bar). This protocol was found to be highly efficient and selective for 4(3H)-quinazolinones, which were isolated in good yields in the presence of two different, recyclable Pd catalysts which were prepared under ultrasound irradiation; a novel lead-free Pd/Boehmite catalyst and a β-cyclodextrin - cross linked Pd catalyst.
The impressive pharmacological properties shown by a number of coumarins have led to extraordinar... more The impressive pharmacological properties shown by a number of coumarins have led to extraordinarily large emphasis being placed on the design of more efficient and greener synthetic procedures to produce them.
The tosyl group (Ts) on 6 I-O-(p-toluenesulfonyl)--cyclodextrin has been substituted with haloge... more The tosyl group (Ts) on 6 I-O-(p-toluenesulfonyl)--cyclodextrin has been substituted with halogenides, nitrogen and sulfur nucleophiles under mechanochemical conditions and the reaction has been investigated in this work. The preparation of mono-substituted cyclodextrin (CD) derivatives, such as azido-, thioureido-, iodo-and thioethers, is shown to be more advantageous in a planetary ball mill (BM) than classic solution methods. All BM reactions
ABSTRACTSynthetic chemists are paying ever more attention to enabling technologies as a means to ... more ABSTRACTSynthetic chemists are paying ever more attention to enabling technologies as a means to opening the paths towards the double goal of achieving high efficiency and meeting green criteria. Non-conventional techniques that create unique environments which promote selective modification have been investigated by many as part of the search for more highly efficient synthetic derivatization of cyclodextrins (CD). A few optimized microwave-assisted protocols have so far been developed for the preparation of selective per-alkylated aminocyclodextrin. In this work, a series of β-CD derivatives, whose primary hydroxyls were all replaced by amino groups, has efficiently been synthesized from per-(6-iodo-6-deoxy)-β-CD via nucleophilic substitution with amines under microwave irradiation in closed vessel (N2 pressure). The reduction of per-(6-azido-6-deoxy)-β-CD to per-(6-amino-6-deoxy)-β-CD via catalytic hydrogenation has also been successfully carried out under dielectric heating.
Nowadays the application of cyclodextrin-assisted molecular encapsulation in foods offers many ad... more Nowadays the application of cyclodextrin-assisted molecular encapsulation in foods offers many advantages. Cyclodextrins, their derivatives and their cross-linked polymers can all improve the quality of food in storage, remove specific components and stabilize and increase the presence of components that are important for a healthy diet. The application of cyclodextrins and their complexes in packaging materials can help not only transport of previously nontransportable foods, but may also prevent, or at least decelerate, the spread of microbial infections. The number of publications, particularly analytical papers, on this matter is constantly increasing. Although the application of modern analytical methods and equipment allows for the quantitation of previously subjectively characterized parameters, bio-sensory methods are still important. The application of cyclodextrins in the nutraceutical industry has many advantages; however, some side effects connected with the inclusion complexation ability of these carbohydrates should lead scientists to study cases on an individual basis. Recent developments in the major fields of cyclodextrin related food research are herein summarized.
The ball-mill-based mechanochemical activation of metallic copper powder facilitates solvent-free... more The ball-mill-based mechanochemical activation of metallic copper powder facilitates solvent-free alkyne-azide click reactions (CuAAC). All parameters that affect reaction rate (i.e., milling time, revolutions/min, size and milling ball number) have been optimized. This new, efficient, facile and eco-friendly procedure has been tested on a number of different substrates and in all cases afforded the corresponding 1,4-disubstituted 1,2,3-triazole derivatives in high yields and purities. The final compounds were isolated in almost quantitative overall yields after simple filtration, making this procedure facile and rapid. The optimized CuAAC protocol was efficiently applied even with bulky functionalized β-cyclodextrins (β-CD) and scaled-up to 10 g of isolated product.
The modification and characterization of porous particles and matrices using cyclodextrins (CD) h... more The modification and characterization of porous particles and matrices using cyclodextrins (CD) has attracted a large amount of interest in recent years. In fact, CDs are at the heart of this study which aims to graft β-CD onto silica particles by means of efficient protocols and nonconventional energy sources. In particular, the use of microwave irradiation, benign reaction media and a solvent-free planetary ball mill has provided a high degree of grafting. The inclusive properties of β-CD grafted silica were tested with phenolphthalein and its sorption capacity with 2 methyl orange and both tests confirmed the efficiency of the grafting protocols. Samples were extensively characterized by TGA, elemental analysis, IR, BET and HRTEM. The green protocols herein reported can facilitate access to functionalized silica and pave the way to its use in novel applications.
The functionalization of single-walled carbon nanotubes (SWCNTs) via microwave-assisted grafting ... more The functionalization of single-walled carbon nanotubes (SWCNTs) via microwave-assisted grafting reactions enables efficient multidecoration in a single step.
Bridged cyclodextrin dimers and trimers, in which respectively two and three hydrophobic cavities... more Bridged cyclodextrin dimers and trimers, in which respectively two and three hydrophobic cavities lie in close proximity, display much higher binding affinities and molecular selectivities than do parent cyclodextrins (CDs). By joining βCD units with links inserted at different positions (2-2', 3-2', 6-2' or 6-2'-6'') and interposing spacers of different lengths and shapes, multicavity structures can be synthesized that are precisely tailored to fit specific guest molecules. This enzyme-mimicking strategy can also be used to generate stable supramolecular adducts. A series of CD dimers and trimers was prepared in good yields by carrying out the critical synthetic steps under power ultrasound (US) or microwave (MW) irradiation. Starting from CD azide and acetylenic derivatives we exploited an efficient MW-promoted Huisgen 1,3dipolar cycloaddition in the presence of Cu(I) salts. The resulting bridged CD derivatives gave stable adducts with magnetic-resonance-imaging contrast agents (MRI CAs) containing gadolinium(III) chelates. These inclusion complexes were found to be 2 to 3 orders of magnitude more stable than those formed by βCD and to be endowed with high relaxivity values.
substituted 6 I-VII -O-t-butyldimethylsilyl(TBDMS)-3 I-VII -O-ethyl-2 I-VII -O-methyl-cyclodextr... more substituted 6 I-VII -O-t-butyldimethylsilyl(TBDMS)-3 I-VII -O-ethyl-2 I-VII -O-methyl-cyclodextrin (MeEt-CD) and 6 I-VII -O-TBDMS-2 I-VII -O-ethyl-3 I-VII -O-methyl--cyclodextrin (EtMe-CD) were synthesised to evaluate the role of the substitution pattern in positions 2 and 3 on the enantioselectivity, in particular in view of their application to routine analysis in fast enantioselective gas chromatography (Es-GC). The chromatographic properties and enantioselectivities of the new derivatives were tested by separating the enantiomers of a series of medium-to-high volatility racemates in the flavour and fragrance field, and compared to those of the corresponding symmetrically substituted 6 I-VII -O-TBDMS-2 I-VII ,3 I-VII -O-methyl--CD (MeMe-CD) and 6 I-VII -O-TBDMS-2 I-VII ,3 I-VII -O-ethyl--CD (EtEt-CD), and were then applied to analysis of real-world essential oil (e.o.) samples. A new synthetic process including the sonochemical approach to obtain synthetic reproducibility and significant yields of the per-substituted derivatives with acceptable reaction times was developed. The results show that asymmetrically substituted methyl/ethyl CDs compared to the methyl or ethyl symmetrical derivatives in general provide better enantioselectivity in terms of both enantiomer resolution and number of separated chiral compounds, and show how the substitution pattern in positions 2 and 3 of the CD ring can influence the separation. Moreover, these new CD derivatives with better enantioselectivity are also shown to be very useful in routine analysis for the exhaustive control of samples containing several chiral characterizing markers in a single run.
The synthetic procedure and the characterization of the new amino derivatives of poly(oxa-pphenyl... more The synthetic procedure and the characterization of the new amino derivatives of poly(oxa-pphenylene-3,3-phtalido-p-phenylene-oxa-p-phenilene-oxyphenylene) (PEEK-WC) with various average degrees of substitution, is reported. The amino PEEK-WC was extensively characterised by using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis, differential scanning calorimeter, scanning electron microscopy, Elemental analyses, NMR, and viscosity meas-urements. The amino PEEK-WC shows different solubility in some solvents in comparison with the parent polymer, good thermal stability and is able to form membrane by means of the phase inversion technique. Amino PEEK-WC results to be quite reactive and can lead to further modification. V
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