Since their initial appearance in the scientific literature, the terms "green" and "sustainable" have been increasingly used and are nowadays ubiquitously present in the terminology of several research areas. Very generally, green chemistry may be considered as the scientific and economical context in which academia, industry and government are attempting to converge their efforts for the development of a sustainable civilization. Novel chemistry and innovative technologies are needed for the development of future, sustainable, chemical production. To reach this goal, both fundamental research, as well as the ability to translate the innovation into real world applications, should be combined. This Thematic Series collects original research and review articles, where an obviously limited but highly exemplificative portion of the broad field of green chemistry is described.
See also the Thematic Series:
Sustainable catalysis
Graphical Abstract
Scheme 1: The transesterification of diethyl oxalate (DEO) with phenol catalyzed by MoO3/SiO2.
Scheme 2: Transesterification of a triglyceride (TG) with DMC for biodiesel production using KOH as the base ...
Scheme 3: Top: Green methylation of phosphines and amines by dimethyl carbonate (Q = N, P). Bottom: anion met...
Figure 1: Structures of some representative SILs and PILs systems. MCF is a silica-based mesostructured mater...
Scheme 4: Synthesis of the acid polymeric IL. EGDMA: ethylene glycol dimethacrylate.
Scheme 5: The transesterification of sec-butyl acetate with MeOH catalyzed by some acidic imidazolium ILs.
Figure 2: Representative examples of ionic liquids for biodiesel production.
Scheme 6: Top: phosgenation of methanol; middle: EniChem and Ube processes; bottom: Asahi process for the pro...
Scheme 7: The transesterification in the synthesis of organic carbonates.
Scheme 8: The transesterification of DMC with alcohols and diols.
Scheme 9: Transesterification of glycerol with DMC in the presence of 1-n-butyl-3-methylimidazolium-2-carboxy...
Scheme 10: Synthesis of the BMIM-2-CO2 catalyst from butylimidazole and DMC.
Scheme 11: Plausible cooperative (nucleophilic–electrophilic) mechanism for the transesterification of glycero...
Scheme 12: Synthesis of diazabicyclo[5.4.0]undec-7-ene-based ionic liquids.
Scheme 13: Synthesis of the DABCO–DMC ionic liquid.
Scheme 14: Cooperative mechanism of ionic liquid-catalyzed glycidol production.
Scheme 15: [TMA][OH]-catalyzed synthesis of glycidol (GD) from glycerol and dimethyl carbonate [46].
Scheme 16: [BMIM]OH-catalyzed synthesis of DPC from DMC and 1-pentanol.
Figure 3: Representative examples of ionic liquids for biodiesel production.
Figure 4: Acyclic non-symmetrical organic carbonates synthetized with 1-(trimethoxysilyl)propyl-3-methylimida...
Scheme 17: A simplified reaction mechanism for DMC production.
Scheme 18: [P8881][MeOCO2] metathesis with acetic acid and phenol.
Figure 5: Examples of carbonates obtained through transesterification using phosphonium salts as catalysts.
Scheme 19: Examples of carbonates obtained from different bio-based diols using [P8881][CH3OCO2] as catalyst.
Scheme 20: Ambiphilic catalysis for transesterification reactions in the presence of carbonate phosphonium sal...
Graphical Abstract
Scheme 1: The Sonogashira reaction.
Figure 1: Cyrene vs. DMF – selected physical properties [31,32].
Figure 2: Aldol products 4a and 4b and single crystal X-ray structure of 4b.
Scheme 2: Cyrene-based Sonogashira cross-coupling: Substrate scope. Isolated yields. aYield using DMF as solv...
Scheme 3: Cacchi-type annulation of o-amino/hydroxy iodoarenes. Isolated yields. aYield using DMF as solvent.
Graphical Abstract
Scheme 1: Synthesis of menthol.
Scheme 2: Synthesis of para-menthane-3,8-diol.
Scheme 3: Synthesis of para-menthane diester derivatives.
Figure 1: PMD conversion using stoichiometric quantities of acetic anhydride.
Figure 2: Product distribution as a function of time.
Figure 3: Product distribution as a function of time.
Figure 4: Effect of molar ratio in product distribution.
Scheme 4: Synthesis of para-menthane mono-ester derivatives.
Graphical Abstract
Figure 1: Formation of 5-HMF from D-glucose or D-fructose followed by oxidation to 2,5-DFF.
Scheme 1: Protonation of 5-HMF (1a) and 2,5-DFF (2) leading to cationic species A, B, C, D.
Figure 2: X-ray crystal structure of compounds 5a (a), and 5c (b) (ORTEP diagrams, ellipsoid contour of proba...
Graphical Abstract
Scheme 1: Synthesis of levulinic acid from ligno-cellulosic feedstocks and its principal uses to access fine ...
Figure 1: Anchoring methodologies: a) impregnation; b) covalent binding.
Figure 2: Activity of the supported sulfonic acid catalyst within the first six cycles. Reaction conditions: ...
Graphical Abstract
Scheme 1: Distribution of products in the Diels–Alder reaction between cyclopentadiene and p-benzoquinone.
Figure 1: Conversion in the DAR catalysed by silica Beta zeolites and Aerosil.
Figure 2: Effect of Lewis and Brønsted acid sites in the conversion (a) and selectivity (b) of the DAR.
Figure 3: Effect of pore size in the conversion (a) and selectivity (b) of the DAR.
Figure 4: Comparison of conversion (a) and selectivity (b) of the DAR catalysed by Al-Beta zeolite and MCM-41....
Figure 5: Comparison of conversion (a) and selectivity (b) of the DAR catalysed extra-large pore 3D zeolites.
Figure 6: Effect of the Si/Al ratio in the conversion (a) and selectivity (b) of the DAR.
Figure 7: Effect of the reutilization of the catalysts in the conversion (a) and selectivity (b) of the DAR.
Graphical Abstract
Figure 1: Regioselectivity of the arylation of 3-substituted thiophenes.
Scheme 1: Blocking groups allowing regioselective C5-arylation of thiophenes.
Scheme 2: Reactivity of 2-bromothiophene with aryl bromides.
Scheme 3: Reactivity of 2-bromo-3-methylthiophene with (hetero)aryl bromides.
Scheme 4: Reactivity of 3-substituted 2-bromothiophenes with aryl bromides.
Scheme 5: 5-Heteroarylation of 2-aryl-5-bromothiophenes.
Scheme 6: 2-Heteroarylation of 2-bromo-3-methylthiophene.
Scheme 7: 5-Arylation of 2,3-disubstituted thiophenes.
Scheme 8: 5-Arylation of 2-aryl-5-bromothiophenes.
Scheme 9: Deprotection of 2-aryl-5-bromothiophene 14.
Graphical Abstract
Scheme 1: Polycyclic scaffolds derived from [3 + 2] adducts 2.
Figure 1: Heterocyclic fragments in bioactive compounds.
Figure 2: One-pot double [3 + 2] cycloadditions and denitrogenation for product 7 under the optimized reactio...
Figure 3: X-ray structure of 7h.
Scheme 2: Proposed mechanism for the 2nd [3 + 2] cycloaddition and denitrogenation.
Figure 4: [5 + 1] Annulation for tetrahydroquinazolines 1.
Graphical Abstract
Figure 1: Chemical structures of bioactive substrates and their partition in subsets.
Scheme 1: Solvent-free and catalyst-free MW-assisted acetylation protocol.
Figure 2: MW-assisted acetylation T-program for different subset of substrates.
Figure 3: LCHRMS (m/z, [M + Na]+ and [M − H]− only for entry F) spectrum of O-acetylated quercetin (reaction ...
Graphical Abstract
Figure 1: The DOE “Top 10” report [2].
Figure 2: Chemical structure of isosorbide and its epimers isomannide and isoidide.
Scheme 1: Conversion of D-sorbitol to isosorbide via twofold dehydration reaction.
Scheme 2: Possible reaction mechanism for the conversion of D-sorbitol to isosorbide.
Scheme 3: Methoxycarbonylation of isosorbide via DMC chemistry.
Scheme 4: Isosorbide homo- and co-polycarbonate via melt polycondensation.
Scheme 5: Synthesis of DMI via DMC chemistry.
Scheme 6: Comparison of the reactivity of isosorbide with other secondary alcohols in methylation reaction. R...
Figure 3: Chemical structure of isosorbide and its epimers isomannide and isoidide.
Graphical Abstract
Figure 1: Chromatographic peak of a compound eluted at a retention volume VR with a width ω.
Scheme 1: Reactions used as examples. (Substrates and products, all the reagents are not shown).
Figure 2:
Variation of with x for reaction b (Scheme 1).
Figure 3: Comparison between calculated and experimental values of MIChr for the reactions of Scheme 1.
Figure 4:
Variation of (N = 35) with Rf for the reactions of Scheme 1.
Graphical Abstract
Scheme 1: Synthesis of per-6-derivatized CDs. Ball milling conditions: 1500 steel balls of 1 mm diameter and ...
Graphical Abstract
Scheme 1: Formation of the benzimidazole core.
Scheme 2: Proposed mechanism for the formation of 1,2-disubstituted benzimidazoles b and 2-substituted benzim...
Figure 1: ESP maps and charge density on carbonylic oxygen atoms for the studied aldehydes obtained at the BP...
Graphical Abstract
Figure 1: Possible two-component couplings for various monocyclic rings frequently encountered in organic mol...
Figure 2: Possible three-component couplings for various monocyclic rings frequently encountered in organic m...
Figure 3: Possible four-component couplings for various monocyclic rings frequently encountered in organic mo...
Figure 4: Permutations of two-component coupling patterns for synthesizing the cyclohexanone ring. Synthesis ...
Figure 5: Permutations of two-component coupling patterns for synthesizing the cyclohexanone ring overlayed w...
Scheme 1: Conjectured syntheses of cyclohexanone via [5 + 1] strategies.
Scheme 2: Conjectured syntheses of cyclohexanone via [4 + 2] strategies.
Scheme 3: Conjectured syntheses of cyclohexanone via [3 + 3] strategies.
Figure 6: Permutations of three-component coupling patterns for synthesizing the cyclohexanone ring. Synthesi...
Figure 7: Permutations of three-component coupling patterns for synthesizing the pyrazole ring via [2 + 2 + 1...
Scheme 4: Literature method for constructing the pyrazole ring via the A4 [2 + 2 + 1] strategy.
Scheme 5: Literature methods for constructing the pyrazole ring via the A5 [2 + 2 + 1] strategy.
Scheme 6: Literature methods for constructing the pyrazole ring via the A1 [2 + 2 + 1] strategy.
Scheme 7: Literature methods for constructing the pyrazole ring via the B4 [3 + 1 + 1] strategy.
Figure 8: Intrinsic green performance of documented pyrazole syntheses according to [2 + 2 + 1] and [3 + 1 + ...
Scheme 8: Conjectured reactions for constructing the pyrazole ring via the A2 and A3 [2 + 2 + 1] strategies.
Scheme 9: Conjectured reactions for constructing the pyrazole ring via the B1, B2, B3, and B4 [3 + 1 + 1] str...
Figure 9: Permutations of three-component coupling patterns for synthesizing the Biginelli ring adduct. Synth...
Scheme 10: Reported syntheses of the Biginelli adduct via the traditional [3 + 2 + 1] mapping strategy.
Scheme 11: Reported syntheses of the Biginelli adduct via new [3 + 2 + 1] mapping strategies.
Scheme 12: Reported syntheses of the Biginelli adduct via a new [2 + 2 + 1 + 1] mapping strategy.
Scheme 13: Conjectured syntheses of the Biginelli adduct via new [2 + 2 + 2] mapping strategies.
Scheme 14: Conjectured syntheses of the Biginelli adduct via new [3 + 2 + 1] mapping strategies.
Figure 10: Intrinsic green performance of documented Biginelli adduct syntheses according to [3 + 2 + 1] three...
Figure 11: Intrinsic green performance of newly conjectured Biginelli adduct syntheses according to [4 + 1 + 1...
Graphical Abstract
Figure 1: Chemical structures of parylene N, parylene C, and parylene D.
Figure 2: Chemical structures of [2.2]paracyclophane and 4,7,12,15-tetrachloro[2.2]paracyclophane.
Scheme 1: Synthesis of substituted (4-methylbenzyl)trimethylammonium bromides from substituted (4-methylbenzy...
Graphical Abstract
Scheme 1: Prototypical Wittig reaction involving in situ phosphonium salt and phosphonium ylide formation.
Scheme 2: Bu3As-catalyzed Wittig-type reactions.
Scheme 3: Ph3As-catalyzed Wittig-type reactions using Fe(TCP)Cl and ethyl diazoacetate for arsonium ylide gen...
Figure 1: Recyclable polymer-supported arsine for catalytic Wittig-type reactions.
Scheme 4: Bu2Te-catalyzed Wittig-type reactions.
Scheme 5: Polymer-supported telluride catalyst cycling.
Scheme 6: Stable and odourless telluronium salt pre-catalyst for Wittig-type reactions.
Scheme 7: Phosphine-catalyzed Wittig reactions.
Figure 2: Various phosphine oxides used as pre-catalysts.
Scheme 8: Enantioselective catalytic Wittig reaction reported by Werner.
Scheme 9: Base-free catalytic Wittig reactions reported by Werner.
Scheme 10: Catalytic Wittig reactions reported by Lin.
Scheme 11: Catalytic Wittig reactions reported by Plietker.
Scheme 12: Prototypical aza-Wittig reaction involving in situ iminophosphorane formation.
Scheme 13: First catalytic aza-Wittig reaction reported by Campbell.
Scheme 14: Intramolecular catalytic aza-Wittig reactions reported by Marsden.
Scheme 15: Catalytic aza-Wittig reactions in 1,4-benzodiazepin-5-one synthesis.
Scheme 16: Catalytic aza-Wittig reactions in benzimidazole synthesis.
Scheme 17: Phosphine-catalyzed Staudinger and aza-Wittig reactions.
Scheme 18: Catalytic aza-Wittig reactions in 4(3H)-quinazolinone synthesis.
Scheme 19: Catalytic aza-Wittig reactions of in situ generated carboxylic acid anhydrides.
Scheme 20: Phosphine-catalyzed diaza-Wittig reactions.
Graphical Abstract
Scheme 1: Continuous flow reduction of 4-nitrobenzophenone using a 0.5 mL PTFE flow reactor.
Scheme 2: Continuous flow reduction of aromatic nitro compounds.
Scheme 3: Continuous-flow reduction of aliphatic nitro compounds.
Scheme 4: Synthesis of 2-(4’-chlrophenyl)aniline (4) with a 5 mL flow reactor.
Scheme 5: Synthesis of intermediate 6, a direct precursor of the drug baclofen.
Scheme 6: Continuous-flow reduction of 1a and in-line extraction.
Graphical Abstract
Scheme 1: L-Proline-promoted stereoselective aldol reaction in DES.
Figure 1: Experimental set-up I: test tube (d = 0.5 cm); flow 1 mL/min; DES (1.5 mL); L-proline/DES = 130 mg/...
Scheme 2: Aldol reaction under continuous flow conditions in DESs.
Graphical Abstract
Figure 1: Overview of the structures of the alcohols 1a–i used in the present work.
Figure 2: Structures of thiols 2a–f used in the present work.
Figure 3: Structures of thioethers 3a–p synthesized.
Figure 4: Product distribution during reaction of 5b and 2a over a solid acid catalyst.
Figure 5: Product distribution during reaction of 1c and 2e.
Scheme 1: Racemization of (R)-1-phenylethanol during the reaction with benzylmercaptan (2a) in the presence o...
Scheme 2: Reaction of cinnamyl alcohol 1i and benzylmercaptan (2a).
Figure 6: Recyclability test of SiAl 0.6 catalyst in the reaction of 1a and 2a.
Graphical Abstract
Figure 1: Electron-transfer initiated activation of α-diketones (background) and present study.
Scheme 1: Proposed dianionic pathway for the cross-benzoin-like reaction of benzils 1 with aldehydes 2 under ...
Scheme 2: Trapping experiment.
Figure 2: Conversion of the 1a/2a coupling in microreactor R5 operated for 150 h at 50 °C.
Graphical Abstract
Scheme 1: PEG-assisted grinding strategy for the preparation of 3,5-disubstituted hydantoins.
Graphical Abstract
Figure 1: Microreactor technologies and flow chemistry for a sustainable chemistry.
Scheme 1: A flow microreactor system for the generation and trapping of highly unstable carbamoyllithium spec...
Scheme 2: Flow synthesis of functionalized α-ketoamides.
Scheme 3: Reactions of benzyllithiums.
Scheme 4: Trapping of benzyllithiums bearing carbonyl groups enabled by a flow microreactor. (Adapted with pe...
Scheme 5: External trapping of chloromethyllithium in a flow microreactor system.
Scheme 6: Scope for the direct tert-butoxycarbonylation using a flow microreactor system.
Scheme 7: Control of anionic Fries rearrangement reactions by using submillisecond residence time. (Adapted w...
Figure 2: Chip microreactor (CMR) fabricated with six layers of polyimide films. (Reproduced with permission ...
Scheme 8: Flow microreactor system for lithiation, borylation, Suzuki–Miyaura coupling and selected examples ...
Scheme 9: Experimental setup for the flow synthesis of 2-fluorobi(hetero)aryls by directed lithiation, zincat...
Scheme 10: Experimental setup for the coupling of fluoro-substituted pyridines. (Adapted with permission from [53]...
Scheme 11: Continuous flow process setup for the preparation of 11 (Reproduced with permission from [54], copyrigh...
Scheme 12: Continuous-flow photocatalytic oxidation of thiols to disulfides.
Scheme 13: Trifluoromethylation by continuous-flow photoredox catalysis.
Scheme 14: Flow photochemical synthesis of 6(5H)-phenanthridiones from 2-chlorobenzamides.
Scheme 15: Synthesis of biaryls 14a–g under photochemical flow conditions.
Scheme 16: Flow oxidation of hydrazones to diazo compounds.
Scheme 17: Synthetic use of flow-generated diazo compounds.
Scheme 18: Ley’s flow approach for the generation of diazo compounds.
Scheme 19: Iterative strategy for the sequential coupling of diazo compounds.
Scheme 20: Integrated synthesis of Bakuchiol precursor via flow-generated diazo compounds.
Scheme 21: Kappe’s continuous-flow reduction of olefines with diimide.
Scheme 22: Multi-injection setup for the reduction of artemisinic acid.
Scheme 23: Flow reactor system for multistep synthesis of (S)-rolipram. Pumps are labelled a, b, c, d and e; L...
Figure 3: Reconfigurable modules and flowcharts for API synthesis. (Reproduced with permission from [85], copyrig...
Figure 4: Reconfigurable system for continuous production and formulation of APIs. (Reproduced with permissio...
Graphical Abstract
Figure 1: Biologically relevant selanyl-1,2,3-triazoles.
Scheme 1: General scheme of the reaction.
Scheme 2: Comparative study of the conventional conditions and ultrasound irradiation. Conditions A: Reaction...
Scheme 3: Reaction of 2-azidophenyl phenyl selenide 1a with activated ketones 2f–k.
Graphical Abstract
Scheme 1: Ring opening of L-LA in the presence of cyclodextrins.
Figure 1: (a) ELSD chromatogram of crude β-CD-LA reaction mixture and (b) MALDI–MS spectrum of fraction f5.
Figure 2: MALDI–MS spectra of the fractionated α-, β- and γ-CD-LA products – fractions precipitated in THF: (...
Figure 3: MALDI–MS spectra of the fractionated α-, β- and γ-CD-LA products – fractions soluble in THF: (a) α-...
Figure 4: 1H NMR spectrum of fractions precipitated in THF of (A) α-CD-LA, (B) β-CD-LA and (C) γ-CD-LA.
Figure 5: 13C NMR spectra of (A) β-CD-LA F2 fraction and (B) β-CD-LA F1 fraction.
Figure 6: DEPT135-NMR experiment of (A) β-CD-LA F2 fraction and (B) β-CD-LA F1 fraction.
Graphical Abstract
Figure 1: N2 isotherms of (a) RGO, (b) Fe/RGO, and (c) Co/RGO.
Figure 2: SEM images of (a and b) RGO, (c) 1% Fe/RGO, and (d) 1% Co/RGO.
Figure 3: TEM micrographs at different magnifications of (a and b) RGO, (c and d) 1% Fe/RGO, and (e and f) 1%...
Figure 4: Powder XRD patterns of RGO supported Fe and Co NPs.
Figure 5: IR spectra of 1% Fe/RGO and 1% Co/RGO catalysts collected by using diffuse reflectance infrared tra...