Studies of sulfonyl radicals. 4. Flash photolysis of aromatic sulfones

Thoi, Ho Huu; Ito, Osamu; Iino, Masashi

doi:10.1021/j100492a014

Cited by 29 publications

(2 citation statements)

References 4 publications

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“…The ESR spectrum of the polysulfone showed typical signals for carbon-centered and sulfonyl radicals . Alkene isomerizations 1 → 4 were also induced upon UV irradiation or heating (80−120 °C) of 1 in the presence of a catalytic amount of (PhSO 2 ) 2 (diphenyldisulfone) . Both the polysulfone- and diphenyldisulfone-catalyzed alkene isomerizations followed zeroth-order rate laws and were inhibited by radical scavenging agents.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of the Diphenyldisulfone-Catalyzed Isomerization of Alkenes. Origin of the Chemoselectivity: Experimental and Quantum Chemistry Studies

et al. 2006

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Polysulfone- and diphenyldisulfone-catalyzed alkene isomerizations are much faster for 2-alkyl-1-alkenes than for linear, terminal alkenes. The mechanism of these reactions has been investigated experimentally for the isomerization of methylidenecyclopentane into 1-methylcyclopentene, and theoretically [CCSD(T)/6-311++G(d,p)//B3LYP/6-311++G(d,p) calculations] for the reactions of propene and 2-methylpropene with a methanesulfonyl radical, MeSO2*. On heating, polysulfones and (PhSO2)2 equilibrate with sulfonyl radicals, RSO2*. The latter abstract allylic hydrogen atoms in one-step processes giving allylic radical/RSO2H pairs that recombine within the solvent cage producing the corresponding isomerized alkene and RSO2*. The sulfinic acid, RSO2H, can diffuse out from the solvent cage (H/D exchange with MeOD,D2O) and reduce an allyl radical. Calculations did not support other possible mechanisms such as hydrogen exchange between alkenes, electron transfer, or addition/elimination process. Kinetic deuterium isotopic effects measured for the (PhSO2)2-catalyzed isomerization of methylidenecyclopentane and deuterated analogues and calculated for the H abstraction from 2-methylpropene and deuterated analogues by CH3SO2* are consistent also with the one-step hydrogen transfer mechanism. The high chemoselectivity for this reaction is not governed by an exothermicity difference but by a difference in ionization energies of the alkenes. Calculations for CH3SO2* + propene and CH3SO2* + 2-methylpropene show a charge transfer of 0.34 and 0.38 electron, respectively, from the alkenes to the sulfonyl radical in the transition states of these hydrogen abstractions.

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Section: Introductionmentioning

confidence: 99%

Mechanism of the Diphenyldisulfone-Catalyzed Isomerization of Alkenes. Origin of the Chemoselectivity: Experimental and Quantum Chemistry Studies

et al. 2006

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“…To gain insights in these steps, we performed laser flash photolysis (LFP) analyses. Interestingly, under 355 nm direct excitation of 2, we observed the development of a transient absorption centred at 410 nm (Figure 3c and S35 left in the Supporting Information), mainly associated with the tosyl radical 10 44,45 . In the absence of other reagents, this species decays to the baseline within a few s, due to radical recombination.…”

Section: Resultsmentioning

confidence: 94%

Radical strain-release photocatalysis for the synthesis of azetidines

Rodríguez,

Corti,

Rizzo

et al. 2024

Preprint

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The increasing popularity of four-member rings in drug discovery programs has vastly widen the research in synthetic chemistry, guiding the community to progress and reinvent old strategies for their crafting. Recently, the strain-release concept has been effectively used to build complex architectures. However, in contrast to the tens of described strategies accessing small carbocyclic derivatives, azetidine synthesis remains severely underdeveloped. Here, we report a mild visible-light-driven method to access densely functionalised azetidines by subjecting azabicyclo[1.1.0]butanes (ABBs) to radical strain-release (RSR) photocatalysis. We investigated the mechanism of this process using a combination of spectroscopic and optical techniques, and density functional theory (DFT) calculations. The chemistry is orchestrated by the activity of a novel organic photosensitiser, that governs the key energy-transfer process with diverse types of sulfonylimine precursors. The formed radical intermediates are intercepted by the ABB through an RSR process, leading access to azetidines in high chemical yields in a single operation. The power and generality of this photocatalytic method is demonstrated for various azetidine targets, including derivatives of Celecoxib and Naproxen.

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Photoinduced Radical Cyclization of 1,6‐Diynes: Rapid Access to Highly Substituted Carbocyclic and Heterocyclic Compounds

2023

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We have developed photoinduced sulfonyl radical-triggered cyclization of 1,6-dynes without metals, oxidants, or additives. During the reaction, three new bonds are formed (À SO 2 À C, CÀ C, and CÀ I/CÀ SeÀ ) under mild conditions, with excellent selectivity. The conversion is temporally and atomically economical and is easy to handle even on a gram scale. Detailed mechanistic studies showed that the reaction proceeds via a radical pathway. Subsequent synthetic transformations of the new products produced various substituted compounds. Importantly, we observed an unprecedented and selective CÀ C single bond cleavage with boronic acid insertion under Suzuki reaction conditions.

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Studies of sulfonyl radicals. 4. Flash photolysis of aromatic sulfones

Cited by 29 publications

References 4 publications

Mechanism of the Diphenyldisulfone-Catalyzed Isomerization of Alkenes. Origin of the Chemoselectivity: Experimental and Quantum Chemistry Studies

Mechanism of the Diphenyldisulfone-Catalyzed Isomerization of Alkenes. Origin of the Chemoselectivity: Experimental and Quantum Chemistry Studies

Radical strain-release photocatalysis for the synthesis of azetidines

Photoinduced Radical Cyclization of 1,6‐Diynes: Rapid Access to Highly Substituted Carbocyclic and Heterocyclic Compounds

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