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Search for "arene activation" in Full Text gives 3 result(s) in Beilstein Journal of Organic Chemistry.
Arene activation via π-bond localization: concepts and opportunities
- Paul Meiners,
- Julian J. Melder and
- Tobias Morack
Beilstein J. Org. Chem. 2026, 22, 257–273, doi:10.3762/bjoc.22.19
- in synthetic chemistry. In this review, we delineate the potential of π-bond localization within the aromatic framework as a general strategy for arene activation and dearomatization. Four distinct approaches are discussed, encompassing localization of the arene π-bonds through small-ring annelation
- highlighted. Collectively, these concepts create a roadmap for the development of new strategies that harness π-bond localization to expand the synthetic utility of aromatic compounds. Keywords: arene activation; arene functionalization; dearomatization; metal–arene π-complexes; strained molecules
- arene activation through π-bond localization (Figure 2B). While most examples remain limited to stoichiometric studies probing the structural and reactivity consequences of perturbing aromatic stability, they collectively unveil a rich and largely untapped conceptual space that continues to simmer
Graphical Abstract
Figure 1: Aromatic molecules as the foundation of modern molecular chemistry.
Figure 2: Arenes as springboards to three-dimensional chemical space and strategies toward arene activation v...
Figure 3: Structure and synthetic utilization of strained arenes; NICS: nucleus independent chemical shifts [26-28].
Figure 4: Bonding and reactivity of η2-coordinated aromatic systems [44,46].
Figure 5: Illustrative selection of η2-coordinating dearomatization agents; MeIm: N-methylimidazole, NHE: nor...
Figure 6: Preparation, lability and most stable linkage isomers of pentaammineosmium(II) complexes.
Scheme 1: Heteroatom-directed reactions of η2-arene complexes [45,50].
Figure 7: Latent functionality through transient metal binding.
Figure 8: Selective hydrogenation of η2-coordinated benzene to cyclohexene under ambient conditions [53,54].
Scheme 2: Synthesis and utilization of enantioenrichted Mo(η2-arene) complexes in enantioselective synthesis [55]....
Scheme 3: Synthesis of trisubstituted cyclohexenes from phenyl sulfones enabled by tungsten-mediated dearomat...
Scheme 4: Diels–Alder reactions of η2-arene complexes with alkenes and alkynes; NMM: N-methylmaleimide [64,65].
Scheme 5: Binding characteristics and pioneering examples of isolable η3-benzyl complexes.
Figure 9: Divergent functionalization of benzyl electrophiles leveraging η3-benzyl complexes toward benzylic ...
Scheme 6: p-Selective allylation of benzyl chlorides with allylstannanes and subsequent synthetic expansion o...
Figure 10: Strategies for para- and ortho-selective arene functionalization/dearomatization via η3-benzyl comp...
Scheme 7: Substrate-dependent ortho- and para-selective dearomatization of naphthyl chlorides and leveraging ...
Figure 11: η4-Arene coordination as an underexplored but promising pathway for arene activation [96,98-100].
Photoredox catalysis harvesting multiple photon or electrochemical energies
- Mattia Lepori,
- Simon Schmid and
- Joshua P. Barham
Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81
Graphical Abstract
Figure 1: Oxidative and reductive activations of organic compounds harvesting photoredox catalysis.
Figure 2: General catalytic cycles of radical ion conPET (left) and radical ion e-PRC (right).
Figure 3: “Beginner’s guide”: comparison between advantages, capacities, and prospectives of conPET and PEC.
Figure 4: A) conPET reductive dehalogenation of aryl halides with PDI. B) Reductive C–H arylation with pyrrol...
Figure 5: A) Chromoselective mono- and disubstitution or polybrominated pyrimidines with pyrroles. B) Sequent...
Figure 6: A) Synthesis of pyrrolo[1,2-a]quinolines. B) Synthesis of ullazines.
Figure 7: A) Reductive phosphorylation of aryl halides via conPET. B) Selected examples from the substrate sc...
Figure 8: A) Reductive dehalogenation of aryl halides via conPET and selected examples from the substrate sco...
Figure 9: A) Reductive C–H arylation of aryl halides via conPET (top) and selected examples from the substrat...
Figure 10: A) Reductive hydrodehalogenation of aryl halides with Mes-Acr-BF4. B) Selected examples from the su...
Figure 11: A) Reductive hydrodechlorination of aryl chlorides with 4-DPAIPN. B) Proposed formation of CO2•−. C...
Figure 12: A) Reductive conPET borylation with 3CzEPAIPN (top) and selected examples from the substrate scope ...
Figure 13: Scale-up of conPET phosphorylation with 3CzEPAIPN.
Figure 14: A) Borylation of 1d. B) Characteristics and structure of PC1 with green and red parts showing the l...
Figure 15: A) Reductive C–H arylation scope with polysulfide conPET (top) and selected examples from the subst...
Figure 16: Scale-up of A) C–H arylation and B) dehaloborylation with polysulfide photocatalysis in continuous-...
Figure 17: A) Formation of [Ir1]0 and [Ir2]0 upon PET between [Ir1]+ and Et3N. B) Mechanism of multi-photon ta...
Figure 18: A) Reductive hydrodehalogenation of aryl halides via multi-photon tandem photocatalysis. B) Selecte...
Figure 19: A) Carbonylative amidation of aryl halides in continuous flow. B) Selected examples from the substr...
Figure 20: A) General scheme for reductive (RQ) and oxidative quenching (OQ) protocols using [FeIII(btz)3](PF6)...
Figure 21: A) Carbonylative amidation of alkyl iodides with [IrIII(ppy)2(dtbbpy)]PF6. B) Selected examples fro...
Figure 22: A) Carboxylative C–N bond cleavage in cyclic amines. B) Selected examples from the substrate scope....
Figure 23: A) Formal reduction of alkenes to alkanes via transfer hydrogenation. B) Selected examples from the...
Figure 24: A) Birch-type reduction of benzenes with PMP-BPI. B) Selected examples from the substrate scope (sc...
Figure 25: Proposed mechanism of the OH− mediated conPET Birch-type reduction of benzene via generation of sol...
Figure 26: Reductive detosylation of N-tosylated amides with Mes-Acr-BF4. B) Selected examples from the substr...
Figure 27: A) Reductive detosylation of N-tosyl amides by dual PRC. B) Selected examples from the substrate sc...
Figure 28: A) Mechanism of the dual PRC based on PET between [Cu(dap)2]+ and DCA. B) Mechanism of the dual PRC...
Figure 29: A) N–O bond cleavage in Weinreb amides with anthracene. B) N–O bond cleavage in Weinreb amides rely...
Figure 30: A) Pentafluorosulfanylation and fluoride elimination. B) Mechanism of the pentafluorosulfanylation ...
Figure 31: A) α-Alkoxypentafluorosulfanylation (top) and selected examples from the substrate scope (bottom). ...
Figure 32: A) Oxidative amination of arenes with azoles catalyzed by N-Ph PTZ. B) Selected examples from the s...
Figure 33: A) C(sp3)–H bond activation by HAT via chloride oxidation by *N-Ph PTZ•+. B) Proposed mechanism for...
Figure 34: A) Recycling e-PRC C–H azolation of electron-rich arenes with pyrazoles using Mes-Acr+ as a photoca...
Figure 35: A) Radical ion e-PRC direct oxidation of unactivated arenes using TAC+ as an electro-activated phot...
Figure 36: A) Radical ion e-PRC direct oxidation of unactivated arenes using TPA as an electro-activated photo...
Figure 37: Proposed mechanism (top) and mode of preassembly (bottom).
Figure 38: A) Possible preassemblies of reactive (left) vs unreactive (right) arenes. B) Calculated spin densi...
Figure 39: A) Recycling e-PRC C(sp2 )–H acetoxylation of arenes using DDQ as a photocatalyst. B) Proposed cata...
Figure 40: Gram scale hydroxylation of benzene in a recirculated flow setup.
Figure 41: A) Radical ion e-PRC vicinal diamination of alkylarenes using TAC+ as an electro-activated photocat...
Figure 42: A) Sequential oxygenation of multiple adjacent C–H bonds under radical ion e-PRC using TAC+ as an e...
Figure 43: A) Enantioselective recycling e-PRC cyanation of benzylic C–H bonds using ADQS as photocatalyst. B)...
Figure 44: Proposed tandem mechanism by Xu and co-workers.
Figure 45: A) Enantioselective recycling e-PRC decarboxylative cyanation using Cu(acac)2, Ce(OTf)3 and a box l...
Figure 46: A) Enantioselective recycling e-PRC benzylic cyanation using Cu(MeCN)4BF4, box ligand and anthraqui...
Figure 47: A) Radical ion e-PRC acetoxyhydroxylation of aryl olefins using TAC+ as an electro-activated photoc...
Figure 48: Selected examples from the substrate scope.
Figure 49: Photoelectrochemical acetoxyhydroxylation in a recirculated flow setup.
Figure 50: A) Radical ion e-PRC aminooxygenation of aryl olefins using TAC+ as an electro-activated photocatal...
Figure 51: A) Recycling e-PRC C–H alkylation of heteroarenes with organic trifluoroborates using Mes-Acr+ as p...
Figure 52: A) Recycling e-PRC decarboxylative C–H alkylation of heteroarenes using CeCl3·7H2O as catalyst. B) ...
Figure 53: A) Recycling e-PRC decarboxylative C–H alkylation of heteroarenes using Fe(NH4)2(SO4)2·6H2O as cata...
Figure 54: A) Recycling e-PRC C–H alkylation of heteroarenes with alkyl oxalates and 4CzIPN as photocatalyst. ...
Figure 55: A) Recycling e-PRC decarboxylative C–H carbamoylation of heteroarenes using 4CzIPN as photocatalyst...
Figure 56: A) Photoelectrochemical HAT-mediated hydrocarbon activation via the chlorine radical. B) Proposed m...
Figure 57: A) Selected examples from the substrate scope. B) Gram and decagram scale semi-continuous flow PEC ...
Figure 58: A) Photoelectrochemical HAT-mediated dehydrogenative coupling of benzothiazoles with aliphatic C–H ...
Figure 59: A) Photoelectrochemical HAT activation of ethers using electro-activated TAC+ as photocatalyst. B) ...
Figure 60: Selected examples from the substrate scope.
Figure 61: A) Photoelectrochemical HAT-mediated synthesis of alkylated benzimidazo-fused isoquinolinones using...
Figure 62: A) Decoupled photoelectrochemical cerium-catalyzed oxydichlorination of alkynes using CeCl3 as cata...
Figure 63: Proposed decoupled photoelectrochemical mechanism.
Figure 64: A) Decoupled photoelectrochemical ring-opening bromination of tertiary cycloalkanols using MgBr2 as...
Figure 65: A) Recycling e-PRC ring-opening functionalization of cycloalkanols using CeCl3 as catalyst. B) Prop...
Figure 66: Selected examples from the substrate scope of the PEC ring-opening functionalization.
Figure 67: A) Radical ion e-PRC reduction of chloro- and bromoarenes using DCA as catalyst and various accepto...
Figure 68: A) Screening of different phthalimide derivatives as catalyst for the e-PRC reduction of aryl halid...
Figure 69: Screening of different organic catalysts for the e-PRC reduction of trialkylanilium salts.
Figure 70: A) e-PRC reduction of phosphonated phenols and anilinium salts. B) Selected examples from the subst...
Figure 71: A) ConPET and e-PRC reduction of 4-bromobenzonitrile using a naphthalene diimide (NDI) precatalyst ...
Figure 72: A) Radical ion e-PRC reduction of phosphinated aliphatic alcohols with n-BuO-NpMI as catalyst. B) C...
Figure 73: Selected examples from the substrate scope.
Figure 74: A) Recycling e-PRC reductive dimerization of benzylic chlorides using a [Cu2] catalyst. B) Proposed...
Figure 75: A) Decoupled photoelectrochemical C–H alkylation of heteroarenes through deamination of Katritzky s...
Figure 76: Proposed mechanism by Chen and co-workers.
True and masked three-coordinate T-shaped platinum(II) intermediates
- Manuel A. Ortuño,
- Salvador Conejero and
- Agustí Lledós
Beilstein J. Org. Chem. 2013, 9, 1352–1382, doi:10.3762/bjoc.9.153
Graphical Abstract
Figure 1: Qualitative orbital diagram for a d8 metal in ML4 square-planar and ML3 T-shaped complexes.
Figure 2: Walsh diagram for the d-block of a d8 ML3 complex upon bending of one L–M–L angle.
Figure 3: Neutral Y-shaped Pt complex Y1 [15]. Angles are given in degrees.
Figure 4: General classification of T-shaped Pt(II) structures according to the fourth coordination site.
Figure 5: Hydride, boryl and borylene true T-shaped Pt(II) complexes.
Figure 6: NHC-based true T-shaped Pt(II) complexes.
Figure 7: Phosphine-based agostic T-shaped Pt(II) complexes. Compounds in brackets correspond with hydrido–al...
Figure 8: Phenylpyridine and NHC-based agostic T-shaped Pt(II) complexes.
Figure 9: Counteranion coordination in T-shaped Pt(II) complexes.
Figure 10: Phosphine-based solvento Pt(II) complexes.
Figure 11: Nitrogen-based solvento Pt(II) complexes.
Figure 12: Pincer-based solvento Pt(II) complexes.
Figure 13: Structure of the QM/MM optimized cisplatin–protein adduct [94].
Figure 14: NMR coupling constants used for the characterization of three-coordinate Pt(II) species.
Figure 15: The chemical formula of the complexes discussed in Table 2.
Scheme 1: Halogen abstraction from 1.
Scheme 2: Halogen abstraction from 2 forming the dicationic complex T3 [22].
Scheme 3: Hydrogenation of complexes A5a and A5b [39].
Scheme 4: Hydrogenation of complexes 3 and A5c [40].
Scheme 5: Intermolecular C–H bond activation from T5a [28].
Scheme 6: Protonation of complexes 4 [35,36].
Scheme 7: Cyclometalation of 5 [43].
Scheme 8: Protonation of 6.
Scheme 9: Reductive elimination of ethane from 7.
Scheme 10: Reductive elimination of methane from six-coordinate Pt(IV) complexes.
Scheme 11: Proposed dissociative mechanism for the fluxional motion of dmphen in [Pt(Me)(dmphen)(PR3)]+ comple...
Figure 16: Feasible interactions for unsaturated intermediates 11b (left) and 12b (right) during fluxional mot...
Scheme 12: Halogen abstraction from 13a,b and subsequent cyclometalation to yield complexes A5a,b [39].
Scheme 13: Proposed mechanism for the acid-catalyzed cyclometalation of 14 via intermediate 15 [41].
Scheme 14: Proposed mechanism for the formation of 19 [102].
Scheme 15: Cyclometalation of 20 via thioether dissociation [117].
Figure 17: Gibbs energy profile (in chloroform solvent) for the cyclometalation of 23 [120].
Scheme 16: Coordination of tmtu to 29 and subsequent C–H bond activation via three-coordinate species 31 and 32...
Scheme 17: Cyclometalation process of NHC-based Pt(II) complexes [28,44].
Scheme 18: Cyclometalation process of complex A9 [43].
Scheme 19: “Rollover” reaction of 38 and subsequent oligomerization [123].
Scheme 20: Proposed mechanism for the formation of cyclometalated species 44 [124].
Scheme 21: Self-assembling process of 45 by “rollover” reaction [126].
Scheme 22: “Rollover” reaction of A9. Energies (solvent) in kcal mol−1 [127].
Scheme 23: Proposed mechanisms for the “rollover” cyclometalation of 52 in gas-phase ion-molecule reactions [128].
Scheme 24: β-H elimination and 1,2-insertion equilibrium involving A1d and the subsequent generation of 57 [35].
Scheme 25: Proposed mechanism for thermolysis of 7b and 7c in benzene-d6 and cyclohexane-d12 solvents [101].
Scheme 26: β-H elimination process of A11a [28].
Scheme 27: Intermolecular C–H bond activation from 62 [95].
Scheme 28: Reductive elimination of methane from 65 followed by CD3CN coordination or C–D bond-activation proc...
Figure 18: DFT-optimized structures describing the κ2 (69, left) and κ3 (69’, right) coordination modes of [Pt...
Scheme 29: Intermolecular arene C–H bond activation from NHC-based complexes [28].
Figure 19: Energy profiles (in benzene solvent) for the benzene C–H bond activation from A11a, A11b, T5a and T...
Scheme 30: Intermolecular arene C–H bond activation from PNP-based complex 71 [12].
Scheme 31: Intermolecular C–H bond-activation by gas-phase ion-molecule reactions of 74 [7,142].
Scheme 32: Dihydrogen activation through complexes A5a, A5b [39], A5c [40] and S1a [54].
Scheme 33: Dihydrogen activation through complexes A7 and 16 [41]. For a: see Scheme 13.
Scheme 34: Br2 and I2 bond activations through complexes A11a and T5a [143].
Scheme 35: Detection and isolation of the Pt(III) complex 81a [143].
Scheme 36: Cl2 bond activation through complexes 82 and 83 [144].
Scheme 37: cis–trans Isomerization mechanism of the solvento Pt(II) complexes S5 [2,61].
Figure 20: Energy profiles for the isomerization of complexes [Pt(R)(PMe3)2(NCMe)]+ where R means Me (85a, red...
Figure 21: DFT-optimized structure of intermediate 86 [62]. Bond distances in angstrom and angles in degrees.
Scheme 38: Proposed dissociative ligand-substitution mechanism of cis-[Pt(R)2S2] complexes (87) [117].
Scheme 39: Proposed mechanisms for the ligand substitution of the dinuclear species 91 [146].
