Visible light-mediated intermolecular [2 + 2] photocycloaddition of 1-aryl-2-nitroethenes and olefins

Mohr, Lisa-Marie; Bauer, Andreas; Jandl, Christian; Bach, Thorsten

doi:10.1039/c9ob01146c

Cited by 13 publications

(9 citation statements)

References 51 publications

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“…The intrinsic lifetime of the eniminium triplet is short ( τ <50 ns, vide supra), which in turn would require the olefin at the given concentration (0.9 m ) to react with a rate constant k >2×10 7 m −1 s −1 to ensure a high degree (>50 %) of triplet quenching. As seen in many examples, the inefficient trapping of a short‐lived triplet by an olefin significantly contributes to low quantum yields.…”

Section: Resultsmentioning

confidence: 99%

Triplet Energy Transfer from Ruthenium Complexes to Chiral Eniminium Ions: Enantioselective Synthesis of Cyclobutanecarbaldehydes by [2+2] Photocycloaddition

et al. 2020

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Chiral eniminium salts, prepared from α,β‐unsaturated aldehydes and a chiral proline derived secondary amine, underwent, upon irradiation with visible light, a ruthenium‐catalyzed (2.5 mol %) intermolecular [2+2] photocycloaddition to olefins, which after hydrolysis led to chiral cyclobutanecarbaldehydes (17 examples, 49–74 % yield), with high diastereo‐ and enantioselectivities. Ru(bpz)3(PF6)2 was utilized as the ruthenium catalyst and laser flash photolysis studies show that the catalyst operates exclusively by triplet‐energy transfer (sensitization). A catalytic system was devised with a chiral secondary amine co‐catalyst. In the catalytic reactions, Ru(bpy)3(PF6)2 was employed, and laser flash photolysis experiments suggest it undergoes both electron and energy transfer. However, experimental evidence supports the hypothesis that energy transfer is the only productive quenching mechanism. Control experiments using Ir(ppy)3 showed no catalysis for the intermolecular [2+2] photocycloaddition of an eniminium ion.

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Section: Resultsmentioning

confidence: 99%

Triplet Energy Transfer from Ruthenium Complexes to Chiral Eniminium Ions: Enantioselective Synthesis of Cyclobutanecarbaldehydes by [2+2] Photocycloaddition

et al. 2020

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show abstract

“…The intrinsic lifetime of the eniminium triplet is short (t < 50 ns, vide supra), which in turn would require the olefin at the given concentration (0.9 m) to react with a rate constant k > 2 10 7 m À1 s À1 to ensure a high degree (> 50 %) of triplet quenching. As seen in many examples, [29,30] the inefficient trapping of a short-lived triplet by an olefin significantly contributes to low quantum yields.…”

Section: Angewandte Chemiementioning

confidence: 99%

Triplet Energy Transfer from Ruthenium Complexes to Chiral Eniminium Ions: Enantioselective Synthesis of Cyclobutanecarbaldehydes by [2+2] Photocycloaddition

et al. 2020

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Chiral eniminium salts, prepared from a,b-unsaturated aldehydes and a chiral proline derived secondary amine, underwent, upon irradiation with visible light, a rutheniumcatalyzed (2.5 mol %) intermolecular [2+2] photocycloaddition to olefins, which after hydrolysis led to chiral cyclobutanecarbaldehydes (17 examples, 49-74 % yield), with high diastereo-and enantioselectivities. Ru(bpz) 3 (PF 6 ) 2 was utilized as the ruthenium catalyst and laser flash photolysis studies show that the catalyst operates exclusively by triplet-energy transfer (sensitization). A catalytic system was devised with a chiral secondary amine co-catalyst. In the catalytic reactions, Ru(bpy) 3 (PF 6 ) 2 was employed, and laser flash photolysis experiments suggest it undergoes both electron and energy transfer. However, experimental evidence supports the hypothesis that energy transfer is the only productive quenching mechanism. Control experiments using Ir(ppy) 3 showed no catalysis for the intermolecular [2+2] photocycloaddition of an eniminium ion.

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“…15 Moreover, the excited-state oxidation potential of 1a is -2.59 V 12c and the reduction potential of oxygen to hydrogen peroxide is +0.65 V (vs. SCE), 12c which are supportive of the fact that the oxidation of indole by oxygen is feasible to generate indolyl radical cation I and superoxide radical anion. It may be noted that the excited-state reduction potential of -nitrostyrene (2a) is +1.90 V, 16 hence its interaction with oxygen is far less likely.…”

Section: Letter Syn Lettmentioning

confidence: 99%

Visible-Light-Enabled Aerobic Denitrative C3-Alkenylation of Indoles with β-Nitrostyrenes

Chawla

Kapoor²,

Yadav

2020

Synlett

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Herein, we unveil the first visible-light-mediated alkenylation reaction of indoles. The reaction follows a denitrative radical pathway where β-nitrostyrenes have been utilized as the alkene precursors for the C3-styrenylation of indoles under visible-light irradiation to afford biologically and synthetically important 3-alkenylindoles. High regioselectivity, absence of any photocatalyst, metal, external oxidant, acid or base, and the use of visible light and air as inexpensive clean reagents are the key highlights of the developed method.

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Visible light-mediated intermolecular [2 + 2] photocycloaddition of 1-aryl-2-nitroethenes and olefins

Abstract: 1-Aryl-4-nitrocyclobutanes were selectively prepared by intermolecular [2 + 2] photocycloaddition reactions from 1-aryl-2-nitroethenes upon irradiation with visible light (λ = 419 nm or λ = 424 nm).

Cited by 13 publications

References 51 publications

Triplet Energy Transfer from Ruthenium Complexes to Chiral Eniminium Ions: Enantioselective Synthesis of Cyclobutanecarbaldehydes by [2+2] Photocycloaddition

Triplet Energy Transfer from Ruthenium Complexes to Chiral Eniminium Ions: Enantioselective Synthesis of Cyclobutanecarbaldehydes by [2+2] Photocycloaddition

Triplet Energy Transfer from Ruthenium Complexes to Chiral Eniminium Ions: Enantioselective Synthesis of Cyclobutanecarbaldehydes by [2+2] Photocycloaddition

Visible-Light-Enabled Aerobic Denitrative C3-Alkenylation of Indoles with β-Nitrostyrenes

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