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Search for "tutorial review" in Full Text gives 6 result(s) in Beilstein Journal of Organic Chemistry.
Photoswitches beyond azobenzene: a beginner’s guide
- Michela Marcon,
- Christoph Haag and
- Burkhard König
Beilstein J. Org. Chem. 2025, 21, 1808–1853, doi:10.3762/bjoc.21.143
- may be overwhelming: azobenzene is undoubtedly the most famous due to its easy synthesis and the extensively studied properties. However, there are several photoswitch classes beyond azobenzene with interesting properties that can be tailored to meet one’s needs. In this tutorial review, we aim to
- ; synthesis of photoswitches; switching mechanisms; tutorial review; Introduction Photophysical properties and switching mechanism Key learning points Switching mechanisms and the change in properties. Overview of the major classes of photoswitches beyond azobenzenes. Main synthetic pathways for their
Graphical Abstract
Figure 1: Energy diagram of a two-state photoswitch. Figure 1 was redrawn from [2].
Figure 2: Example of the absorption spectra of the isomers of a photoswitch with most efficient irradiation w...
Scheme 1: Photoswitch classes described in this review.
Figure 3: Azoheteroarenes.
Scheme 2: E–Z Isomerisation (top) and mechanisms of thermal Z–E isomerisation (bottom).
Scheme 3: Rotation mechanism favoured by the electron displacement in push–pull systems. Selected examples of...
Figure 4: A) T-shaped and twisted Z-isomers determine the thermal stability and the Z–E-PSS (selected example...
Figure 5: Effect of di-ortho-substitution on thermal half-life and PSS.
Figure 6: Selected thermal lifetimes of azoindoles in different solvents and concentrations. aConcentration o...
Figure 7: Aryliminopyrazoles: N-pyrazoles (top) and N-phenyl (bottom).
Scheme 4: Synthesis of symmetrical heteroarenes through oxidation (A), reduction (B), and the Bayer–Mills rea...
Scheme 5: Synthesis of diazonium salt (A); different strategies of azo-coupling: with a nucleophilic ring (B)...
Scheme 6: Synthesis of arylazothiazoles 25 (A) and heteroaryltriazoles 28 (B).
Scheme 7: Synthesis of heteroarylimines 31a,b [36-38].
Figure 8: Push–pull non-ionic azo dye developed by Velasco and co-workers [45].
Scheme 8: Azopyridine reported by Herges and co-workers [46].
Scheme 9: Photoinduced phase transitioning azobispyrazoles [47].
Figure 9: Diazocines.
Scheme 10: Isomers, conformers and enantiomers of diazocine.
Scheme 11: Partial overlap of the ππ* band with electron-donating substituents and effect on the PSS. Scheme 11 was ada...
Figure 10: Main properties of diazocines with different bridges. aMeasured in n-hexane [56]. bMeasured in THF. cMe...
Scheme 12: Synthesis of symmetric diazocines.
Scheme 13: Synthesis of asymmetric diazocines.
Scheme 14: Synthesis of O- and S-heterodiazocines.
Scheme 15: Synthesis of N-heterodiazocines.
Scheme 16: Puromycin diazocine photoswitch [60].
Figure 11: Indigoids.
Figure 12: The main representatives of the indigoid photoswitch class.
Scheme 17: Deactivation process that prevents Z-isomerisation of indigo.
Figure 13: Stable Z-indigo derivative synthesised by Wyman and Zenhäusern [67].
Figure 14: Selected examples of indigos with aliphatic and aromatic substituents [68]. Dashed box: proposed π–π in...
Scheme 18: Resonance structures of indigo and thioindigo involving the phenyl ring.
Scheme 19: Possible deactivation mechanism for 4,4'-dihydroxythioindigo [76].
Scheme 20: Effect of different heteroaryl rings on the stability and the photophysical properties of hemiindig...
Figure 15: Thermal half-lives of red-shifted hemithioindigos in toluene [79]. aMeasured in toluene-d8.
Scheme 21: Structures of pyrrole [81] and imidazole hemithioindigo [64].
Figure 16: Examples of fully substituted double bond hemithioindigo (left), oxidised hemithioindigos (centre),...
Scheme 22: Structure of iminothioindoxyl 72 (top) and acylated phenyliminoindolinone photoswitch 73 (bottom). ...
Scheme 23: (top) Transition states of iminothioindoxyl 72. The planar transition state is associated with a lo...
Scheme 24: Baeyer–Drewsen synthesis of indigo (top) and N-functionalisation strategies (bottom).
Scheme 25: Synthesis of hemiindigo.
Scheme 26: Synthesis of hemithioindigo and iminothioindoxyl.
Scheme 27: Synthesis of double-bond-substituted hemithioindigos.
Scheme 28: Synthesis of phenyliminoindolinone.
Scheme 29: Hemithioindigo molecular motor [85].
Figure 17: Arylhydrazones.
Scheme 30: Switching of arylhydrazones. Note: The definitions of stator and rotor are arbitrary.
Scheme 31: Photo- and acidochromism of pyridine-based phenylhydrazones.
Scheme 32: A) E–Z thermal inversion of a thermally stable push–pull hydrazone [109]. B) Rotation mechanism favoured...
Scheme 33: Effect of planarisation on the half-life.
Scheme 34: The longest thermally stable hydrazone switches reported so far (left). Modulation of thermal half-...
Figure 18: Dependency of t1/2 on concentration and hypothesised aggregation-induced isomerisation.
Figure 19: Structure–property relationship of acylhydrazones.
Scheme 35: Synthesis of arylhydrazones.
Scheme 36: Synthesis of acylhydrazones.
Scheme 37: Photoswitchable fluorophore by Aprahamian et al. [115].
Scheme 38: The four-state photoswitch synthesised by the Cigáň group [116].
Figure 20: Diarylethenes.
Scheme 39: Isomerisation and oxidation pathway of E-stilbene to phenanthrene.
Scheme 40: Strategies adapted to avoid E–Z isomerisation and oxidation.
Scheme 41: Molecular orbitals and mechanism of electrocyclisation for a 6π system.
Figure 21: Aromatic stabilisation energy correlated with the thermal stability of the diarylethenes [127,129].
Figure 22: Half-lives of diarylethenes with increasing electron-withdrawing groups [128,129].
Scheme 42: Photochemical degradation pathway promoted by electron-donating groups [130].
Figure 23: The diarylethenes studied by Hanazawa et al. [134]. Increased rigidity leads to bathochromic shift.
Scheme 43: The dithienylethene synthesised by Nakatani's group [135].
Scheme 44: Synthesis of perfluoroalkylated diarylethenes.
Scheme 45: Synthesis of 139 and 142 via McMurry coupling.
Scheme 46: Synthesis of symmetrical derivatives 145 via Suzuki–Miyaura coupling.
Scheme 47: Synthesis of acyclic 148, malonic anhydride 149, and maleimide derivatives 154.
Figure 24: Gramicidin S (top left) and two of the modified diarylethene derivatives: first generation (bottom ...
Scheme 48: Pyridoxal 5'-phosphate and its reaction with an amino acid (top). The analogous dithienylethene der...
Figure 25: Fulgides.
Scheme 49: The three isomers of fulgides.
Scheme 50: Thermal and photochemical side products of unsubstituted fulgide [150].
Figure 26: Maximum absorption λc of the closed isomer compared with the nature of the aromatic ring and the su...
Scheme 51: Possible rearrangement of the excited state of 5-dimethylaminoindolylfulgide [153].
Figure 27: Quantum yields of ring closure (ΦE→C) and E–Z isomerisation (ΦE→Z) correlated with the increasing s...
Scheme 52: Active (Eα) and inactive (Eβ) conformers (left) and the bicyclic sterically blocked fulgide 169 (ri...
Scheme 53: Quantum yield of ring-opening (ΦC→E) and E–Z isomerisation (ΦE→Z) for different substitution patter...
Scheme 54: Stobbe condensation pathway for the synthesis of fulgides 179, fulgimides 181 and fulgenates 178.
Scheme 55: Alternative synthesis of fulgides through Pd-catalysed carbonylation.
Scheme 56: Optimised synthesis of fulgimides [166].
Scheme 57: Photoswitchable FRET with a fulgimide photoswitch [167].
Scheme 58: Three-state fulgimide strategy by Slanina's group.
Figure 28: Spiropyrans.
Scheme 59: Photochemical (left) and thermal (right) ring-opening mechanisms for an exemplary spiropyran with a...
Figure 29: Eight possible isomers of the open merocyanine according to the E/Z configurations of the bonds hig...
Scheme 60: pH-Controlled photoisomerisation between the closed spiropyran 191-SP and the open E-merocyanine 19...
Scheme 61: Behaviour of spiropyran in water buffer according to Andréasson and co-workers [180]. 192-SP in an aqueo...
Scheme 62: (left box) Proposed mechanism of basic hydrolysis of MC [184]. (right box) Introduction of electron-dona...
Scheme 63: Photochemical interconversion of naphthopyran 194 (top) and spirooxazine 195 (bottom) photoswitches...
Scheme 64: Synthesis of spiropyrans and spirooxazines 198 and the dicondensation by-product 199.
Scheme 65: Alternative synthesis of spiropyrans and spirooxazines with indolenylium salt 200.
Scheme 66: Synthesis of 4’-substituted spiropyrans 203 by condensation of an acylated methylene indoline 201 w...
Scheme 67: Synthesis of spironaphthopyrans 210 by acid-catalysed condensation of naphthols and diarylpropargyl...
Scheme 68: Photoswitchable surface wettability [194].
Figure 30: Some guiding principles for the choice of the most suitable photoswitch. Note that this guide is ve...
Heterogeneous photocatalysis in flow chemical reactors
- Christopher G. Thomson,
- Ai-Lan Lee and
- Filipe Vilela
Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125
Graphical Abstract
Figure 1: A) Bar chart of the publications per year for the topics “Photocatalysis” (49,662 instances) and “P...
Figure 2: A) Professor Giacomo Ciamician and Dr. Paolo Silber on their roof laboratory at the University of B...
Scheme 1: PRC trifluoromethylation of N-methylpyrrole (1) using hazardous gaseous CF3I safely in a flow react...
Figure 3: A) Unit cells of the three most common crystal structures of TiO2: rutile, brookite, and anatase. R...
Figure 4: Illustration of the key semiconductor photocatalysis events: 1) A photon with a frequency exceeding...
Figure 5: Photocatalytic splitting of water by oxygen vacancies on a TiO2(110) surface. Reprinted with permis...
Figure 6: Proposed adsorption modes of A) benzene, B) chlorobenzene, C) toluene, D) phenol, E) anisole, and F...
Figure 7: Structures of the sulfonate-containing organic dyes RB5 (3) and MX-5B (4) and the adsorption isothe...
Figure 8: Idealised triclinic unit cell of a g-C3N4 type polymer, displaying possible hopping transport scena...
Figure 9: Idealised structure of a perfect g-C3N4 sheet. The central unit highlighted in red represents one t...
Figure 10: Timeline of the key processes of charge transport following the photoexcitation of g-C3N4, leading ...
Scheme 2: Photocatalytic bifunctionalisation of heteroarenes using mpg-C3N4, with the selected examples 5 and ...
Figure 11: A) Structure of four linear conjugated polymer photocatalysts for hydrogen evolution, displaying th...
Figure 12: Graphical representation of the common methods used to immobilise molecular photocatalysts (PC) ont...
Figure 13: Wireless light emitter-supported TiO2 (TiO2@WLE) HPCat spheres powered by resonant inductive coupli...
Figure 14: Graphical representation of zinc–perylene diimide (Zn-PDI) supramolecular assembly photocatalysis v...
Scheme 3: Upconversion of NIR photons to the UV frequency by NaYF4:Yb,Tm nanocrystals sequentially coated wit...
Figure 15: Types of reactors employed in heterogeneous photocatalysis in flow. A) Fixed bed reactors and the s...
Figure 16: Electrochemical potential of common semiconductor, transition metal, and organic dye-based photocat...
Scheme 4: Possible mechanisms of an immobilised molecular photoredox catalyst by oxidative or reductive quenc...
Scheme 5: Scheme of the CMB-C3N4 photocatalytic decarboxylative fluorination of aryloxyacetic acids, with the...
Scheme 6: Scheme of the g-C3N4 photocatalytic desilylative coupling reaction in flow and proposed mechanism [208].
Scheme 7: Proposed mechanism of the radical cyclisation of unsaturated alkyl 2-bromo-1,3-dicarbonyl compounds...
Scheme 8: N-alkylation of benzylamine and schematic of the TiO2-coated microfluidic device [213].
Scheme 9: Proposed mechanism of the Pt@TiO2 photocatalytic deaminitive cyclisation of ʟ-lysine (23) to ʟ-pipe...
Scheme 10: A) Proposed mechanism for the photocatalytic oxidation of phenylboronic acid (24). B) Photos and SE...
Scheme 11: Proposed mechanism for the DA-CMP3 photocatalytic aza-Henry reaction performed in a continuous flow...
Scheme 12: Proposed mechanism for the formation of the cyclic product 32 by TiO2-NC HPCats in a slurry flow re...
Scheme 13: Reaction scheme for the photocatalytic synthesis of homo and hetero disulfides in flow and scope of...
Scheme 14: Reaction scheme for the MoOx/TiO2 HPCat oxidation of cyclohexane (34) to benzene. The graph shows t...
Scheme 15: Proposed mechanism of the TiO2 HPC heteroarene C–H functionalisation via aryl radicals generated fr...
Scheme 16: Scheme of the oxidative coupling of benzylamines with the HOTT-HATN HPCat and selected examples of ...
Scheme 17: Photocatalysis oxidation of benzyl alcohol (40) to benzaldehyde (41) in a microflow reactor coated ...
Figure 17: Mechanisms of Dexter and Forster energy transfer.
Scheme 18: Continuous flow process for the isomerisation of alkenes with an ionic liquid-immobilised photocata...
Scheme 19: Singlet oxygen synthetic step in the total synthesis of canataxpropellane [265].
Scheme 20: Scheme and proposed mechanism of the singlet oxygen photosensitisation by CMP_X HPCats, with the st...
Scheme 21: Structures of CMP HPCat materials applied by Vilela and co-workers for the singlet oxygen photosens...
Scheme 22: Polyvinylchloride resin-supported TDCPP photosensitisers applied for singlet oxygen photosensitisat...
Scheme 23: Structure of the ionically immobilised TPP photosensitiser on amberlyst-15 ion exchange resins (TPP...
Scheme 24: Photosensitised singlet oxygen oxidation of citronellol (46) in scCO2, with automatic phase separat...
Scheme 25: Schematic of PS-Est-BDP-Cl2 being applied for singlet oxygen photosensitisation in flow. A) Pseudo-...
Scheme 26: Reaction scheme of the singlet oxygen oxidation of furoic acid (54) using a 3D-printed microfluidic...
Figure 18: A) Photocatalytic bactericidal mechanism by ROS oxidative cleavage of membrane lipids (R = H, amino...
Figure 19: A) Suggested mechanisms for the aqueous pollutant degradation by TiO2 in a slurry flow reactor [284-287]. B)...
Figure 20: Schematic of the flow system used for the degradation of aqueous oxytetracycline (56) solutions [215]. M...
Scheme 27: Degradation of a salicylic acid (57) solution by a coupled solar photoelectro-Fenton (SPEF) process...
Figure 21: A) Schematic flow diagram using the TiO2-coated NETmix microfluidic device for an efficient mass tr...
Copper-catalyzed enantioselective conjugate addition of organometallic reagents to challenging Michael acceptors
- Delphine Pichon,
- Jennifer Morvan,
- Christophe Crévisy and
- Marc Mauduit
Beilstein J. Org. Chem. 2020, 16, 212–232, doi:10.3762/bjoc.16.24
- reagents to these challenging Michael acceptors, with excellent regio- and enantioselectivity. Furthermore, thanks to their easy derivatization, the resulting chiral conjugated products could be converted into various natural products. The aim of this tutorial review is to summarize recent advances
- -acyloxazolidinones, N-acylpyrrolidinones, amides, and N-acylpyrroles have been scarcely investigated in Cu ECA despite their usefulness for postfunctionalizations. This tutorial review aims to describe the early examples and recent advances in copper-catalyzed asymmetric conjugate additions of dialkylzinc, Grignard
Graphical Abstract
Scheme 1: Competitive side reactions in the Cu ECA of organometallic reagents to α,β-unsaturated aldehydes.
Scheme 2: Cu-catalyzed ECA of α,β-unsaturated aldehydes with phosphoramidite- (a) and phosphine-based ligands...
Scheme 3: One-pot Cu-catalyzed ECA/organocatalyzed α-substitution of enals.
Scheme 4: Combination of copper and amino catalysis for enantioselective β-functionalizations of enals.
Scheme 5: Optimized conditions for the Cu ECAs of R2Zn, RMgBr, and AlMe3 with α,β-unsaturated aldehydes.
Scheme 6: CuECA of Grignard reagents to α,β-unsaturated thioesters and their application in the asymmetric to...
Scheme 7: Improved Cu ECA of Grignard reagents to α,β-unsaturated thioesters, and their application in the as...
Scheme 8: Catalytic enantioselective synthesis of vicinal dialkyl arrays via Cu ECA of Grignard reagents to γ...
Scheme 9: 1,6-Cu ECA of MeMgBr to α,β,γ,δ-bisunsaturated thioesters: an iterative approach to deoxypropionate...
Scheme 10: Tandem Cu ECA/intramolecular enolate trapping involving 4-chloro-α,β-unsaturated thioester 22.
Scheme 11: Cu ECA of Grignard reagents to 3-boronyl α,β-unsaturated thioesters.
Scheme 12: Cu ECA of alkylzirconium reagents to α,β-unsaturated thioesters.
Scheme 13: Conversion of acylimidazoles into aldehydes, ketones, acids, esters, amides, and amines.
Scheme 14: Cu ECA of dimethyl malonate to α,β-unsaturated acylimidazole 31 with triazacyclophane-based ligand ...
Scheme 15: Cu/L13-catalyzed ECA of alkylboranes to α,β-unsaturated acylimidazoles.
Scheme 16: Cu/hydroxyalkyl-NHC-catalyzed ECA of dimethylzinc to α,β-unsaturated acylimidazoles.
Scheme 17: Stereocontrolled synthesis of 3,5,7-all-syn and anti,anti-stereotriads via iterative Cu ECAs.
Scheme 18: Stereocontrolled synthesis of anti,syn- and anti,anti-3,5,7-(Me,OR,Me) units via iterative Cu ECA/B...
Scheme 19: Cu-catalyzed ECA of dialkylzinc reagents to α,β-unsaturated N-acyloxazolidinones.
Scheme 20: Cu/phosphoramidite L16-catalyzed ECA of dialkylzincs to α,β-unsaturated N-acyl-2-pyrrolidinones.
Scheme 21: Cu/(R,S)-Josiphos (L9)-catalyzed ECA of Grignard reagents to α,β-unsaturated amides.
Scheme 22: Cu/Josiphos (L9)-catalyzed ECA of Grignard reagents to polyunsaturated amides.
Scheme 23: Cu-catalyzed ECA of trimethylaluminium to N-acylpyrrole derivatives.
A tutorial review of stereoretentive olefin metathesis based on ruthenium dithiolate catalysts
- Daniel S. Müller,
- Olivier Baslé and
- Marc Mauduit
Beilstein J. Org. Chem. 2018, 14, 2999–3010, doi:10.3762/bjoc.14.279
- within the past years. This unique catalyst class is able to kinetically produce both Z- and E-alkenes in high stereochemical purity (typically >95:5) starting from stereochemically pure Z- or E-alkenes. The aim of this tutorial review is to organize the reported information concerning ruthenium
Graphical Abstract
Scheme 1: Synthesis of first Ru-dithiolate metathesis catalysts.
Figure 1: Most efficient Ru-dithiolate catalysts for stereoretentive olefin metathesis with Z- and E-alkenes ...
Figure 2: Selected examples of sterically or electronically modified ruthenium dithiolate complexes.
Figure 3: Model for stereoretentive metathesis proposed by Pederson and Grubbs [3].
Figure 4: Decrease in the benzylidene signal over time upon reaction with (E)-2-hexenyl acetate.
Scheme 2: Selected applications, part 1.
Scheme 3: Selected applications, part 2.
Figure 5: Catalyst loading required for different types of metathesis reactions.
Scheme 4: Proposed catalyst decomposition pathway occurring via attack of the electron-rich sulfide into meth...
Scheme 5: In situ methylene capping strategy for stereoretentive metathesis.
Scheme 6: Stereoretentive cross-metathesis with (Z)-butene (Z-25) as in situ methylene capping agent; selecte...
Scheme 7: Cross metathesis with Z- and E-trisubstituted allylic alcohols.
Scheme 8: In situ synthesis of Ru-3 and application thereof in the cross-metathesis of 12 and 50.
Figure 6: Examples of biologically active and fragrance molecules synthesized by stereoretentive metathesis.
Mechanochemistry of nucleosides, nucleotides and related materials
- Olga Eguaogie,
- Joseph S. Vyle,
- Patrick F. Conlon,
- Manuela A. Gîlea and
- Yipei Liang
Beilstein J. Org. Chem. 2018, 14, 955–970, doi:10.3762/bjoc.14.81
- mechanochemistry upon biological chemistry and specifically the selective degradation of biopolymers which enables biochemically active materials to be isolated from cell grindates – most notably in Buchner’s laboratory [14] – appears not to have been considered. A recent tutorial review by Andersen and Mack [15
Graphical Abstract
Figure 1: Examples of equipment used to perform mechanochemistry on nucleoside and nucleotide substrates (not...
Figure 2: Ganciclovir.
Scheme 1: Nucleoside tritylation effected by hand grinding in a heated mortar and pestle.
Scheme 2: Persilylation of ribonucleoside hydroxy groups (and in situ acylation of cytidine) in a MBM.
Scheme 3: Nucleoside amine and carboxylic acid Boc protection using an improvised attritor-type mill.
Scheme 4: Nucleobase Boc protection via transient silylation using an improvised attritor-type mill.
Scheme 5: Chemoselective N-acylation of an aminonucleoside using LAG in a MBM.
Scheme 6: Azide–alkyne cycloaddition reactions performed in a copper vessel in a MBM.
Figure 3: a) Custom-machined copper vessel and zirconia balls used to perform CuAAC reactions (showing: upper...
Scheme 7: Thiolate displacement reactions of nucleoside derivatives in a MBM.
Scheme 8: Selenocyanate displacement reactions of nucleoside derivatives in a MBM.
Scheme 9: Nucleobase glycosidation reactions and subsequent deacetylation performed in a MBM.
Scheme 10: Regioselective phosphorylation of nicotinamide riboside in a MBM.
Scheme 11: Preparation of nucleoside phosphoramidites in a MBM using ionic liquid-stabilised chlorophosphorami...
Scheme 12: Preparation of a nucleoside phosphite triester using LAG in a MBM.
Scheme 13: Internucleoside phosphate coupling linkages in a MBM.
Scheme 14: Preparation of ADPR analogues using in a MBM.
Scheme 15: Synthesis of pyrophosphorothiolate-linked dinucleoside cap analogues in a MBM to effect hydrolytic ...
Figure 4: Early low temperature mechanised ball mill as described by Mudd et al. – adapted from reference [78].
Scheme 16: Co-crystal grinding of alkylated nucleobases in an amalgam mill (N.B. no frequency was recorded in ...
Figure 5: Materials used to prepare a smectic phase.
Figure 6: Structures of 5-fluorouracil (5FU) and nucleoside analogue prodrugs subject to mechanochemical co-c...
Scheme 17: Preparation of DNA-SWNT complex in a MBM.
Temperature measurements with two different IR sensors in a continuous-flow microwave heated system
- Jonas Rydfjord,
- Fredrik Svensson,
- Magnus Fagrell,
- Jonas Sävmarker,
- Måns Thulin and
- Mats Larhed
Beilstein J. Org. Chem. 2013, 9, 2079–2087, doi:10.3762/bjoc.9.244
- ][15][16]. In contrast, microwave transparent fiber optic probes can be used for correct temperature measurements. In a recent tutorial review Kappe highlighted the difficulties of temperature monitoring under microwave heating [16]. We recently described the concept of a nonresonant microwave
Graphical Abstract
Figure 1: Instrument setup.
Figure 2: (a) Setup of system with temperature measurement by IR sensor 1. (b) Illustration of temperature me...
Figure 3: Average absolute errors in measurements for IR sensor 1 (left) and IR sensor 2 (right) plotted agai...
Figure 4: Heating profiles for IR sensor 1 (top) and IR sensor 2 (bottom) when heating isopropanol at a flow ...
Figure 5: IR sensor 1, NMP, 1 mL/min.
