Novel [4 + 2] Cycloaddition between Thiobenzophenone and Aryl-Substituted Alkenes via Photoinduced Electron Transfer

Argüello, Juan E.; Pérez‐Ruiz, Raúl; Miranda, Miguel A.

doi:10.1021/ol7014384

Cited by 21 publications

(17 citation statements)

References 23 publications

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“…Thiobenzophenones have also been utilized in similar [4+2] transformations with pyrylium and thiapyrylium salts as catalysts. 272,273 Miranda and coworkers have researched the mechanism of the imino Diels-Alder transformations using a combination of laser flash photolysis and DFT calculations. It was determined that the mechanism likely involves single-electron oxidation of the alkene component first, as 53 (54.5), and potassium trifluoroborates (54.7).…”

Section: Triaryl Oxopyrylium Salts: Photophysical and Electrochemicalmentioning

confidence: 99%

Organic Photoredox Catalysis

2016

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In this review, we highlight the use of organic photoredox catalysts in a myriad of synthetic transformations with a range of applications. This overview is arranged by catalyst class where the photophysics and electrochemical characteristics of each is discussed to underscore the differences and advantages to each type of single electron redox agent. We highlight both net reductive and oxidative as well as redox neutral transformations that can be accomplished using purely organic photoredox-active catalysts. An overview of the basic photophysics and electron transfer theory is presented in order to provide a comprehensive guide for employing this class of catalysts in photoredox manifolds.

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Section: Triaryl Oxopyrylium Salts: Photophysical and Electrochemicalmentioning

confidence: 99%

Organic Photoredox Catalysis

2016

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“…This is not the case for the H-bond-"off" system, where a transient bond is observed in Fig. 4b between sulfur and a carbon atom in cyclopentadiene 28,29 . This implies that the formation of the second C-C bond has to overcome an additional energy barrier in the H-bond-"off" system due to an interaction between sulfur and cyclopentadiene.…”

Section: Resultsmentioning

confidence: 89%

On the Role of Hydrogen Bond Strength and Charge Transfer of a Diels-Alder Reaction On-Water: Semiempirical and Free Energy Calculations.

Henao

Gohar²,

Whilhelm³

et al. 2021

Preprint

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Accelerated chemistry at the interface with water has received increasing attention. The mechanisms behind the enhanced reactivity On-Water are not yet clear. In this work we use a Langevin scheme in the spirit of second generation Car-Parrinello to accelerate the second-order density functional Tight-Binding (DFTB2) method in order to investigate the free energy of two Diels-Alder reaction On-Water: the cycloaddition between cyclopentadiene and ethyl cinnamate or thionocinnamate. The only difference between the reactants is the substitution of a carbonyl oxygen for a thiocarbonyl sulfur, making possible the distinction between them as strong and weak hydrogen-bond acceptors. We find a different mechanism for the reaction during the transition states and uncover the role of hydrogen bonds along with the reaction path. Our results suggest that acceleration of Diels-Alder reactions do not arise from an increased number of hydrogen bonds at the transition state and charge transfer plays a significant role. However, the presence of water and hydrogen-bonds is determinant for the catalysis of these reactions.

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“…The CT process from 2a to 1 was negligible (0.04 e), indicating a nonpolar character of the TS GS and supporting the large activation energy associated with this reaction at the GS. 19 Radical Cationic [4 + 2] Cycloaddition Reaction Between 1 and 2a-c. Experimentally, 8 both the RCs of thiobenzophenone and the alkenes are generated by photosensitized electron transfer; these intermediates could in principle react further, following a concerted or a stepwise [4 + 2] cycloaddition mechanism. An exhaustive exploration of the PES for the RC version of the reaction between 1 and 2a-c showed that the process actually occurs through a stepwise mechanism.…”

Section: Resultsmentioning

confidence: 99%

“…8 The scope of this reaction was investigated by using different types of electron-withdrawing or electron-releasing (ER) substituents. The mechanism was experimentally investigated by means of laser flash photolysis; it was found to involve formation of radical cations (RCs), which would react further in a concerted or stepwise fashion.…”

Section: Introductionmentioning

confidence: 99%

DFT Study on the Molecular Mechanism of the [4 + 2] Cycloaddition between Thiobenzophenone and Arylalkenes via Radical Cations

et al. 2009

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The mechanistic aspects of the radical cationic version of the [4 + 2] cycloaddition between thiobenzophenone 1 and three aryl-substituted alkenes 2a-c have been studied using DFT methods at the UB3LYP/6-31G* level of theory. In the ground state, the Diels-Alder reaction follows an asynchronous concerted mechanism; the large activation energy associated with bond formation prevents this process. After generation of the radical cation (RC), formation of a molecular complex (MC) between 1 and 2a-c initiates a stepwise mechanism, with attack of the sulfur atom of 1 to the aryl-conjugated position of 2a-c. Subsequent ring closure is the rate-determining step of these cycloadditions. Methoxy or dimethylamino substitution at the aryl group, while stabilizing the corresponding RC, results in a less exothermic formation of MC and a significant increase of the cycloaddition barrier.

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Novel [4 + 2] Cycloaddition between Thiobenzophenone and Aryl-Substituted Alkenes via Photoinduced Electron Transfer

Cited by 21 publications

References 23 publications

Organic Photoredox Catalysis

Organic Photoredox Catalysis

On the Role of Hydrogen Bond Strength and Charge Transfer of a Diels-Alder Reaction On-Water: Semiempirical and Free Energy Calculations.

DFT Study on the Molecular Mechanism of the [4 + 2] Cycloaddition between Thiobenzophenone and Arylalkenes via Radical Cations

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