On the Mechanism of Oxetan Formation in the Photocycloaddition of <i>p</i>-Benzoquinone to Alkenes

Bunce, Nigel J.; Hadley, Mary

doi:10.1139/v75-461

“…The oxidation products of HQ do undergo further reactions under prolonged illumination,35 as well as 1.4-addition and cycloaddition reactions. 44,45 Thus there may be a number of species formed under these conditions.…”

Section: Discussionmentioning

confidence: 99%

Spin trapping and electron spin resonance detection of radical intermediates in the photodecomposition of water at titanium dioxide particulate systems

Jaeger

¹

,

Bard²

1979

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“…This trend can be explained by the increased allylic strain between the exocyclic R group and the equatorial proton at the position 2 of the ring. The lack of selectivity for acyclic [24] and macrocyclic substrates was explained in terms of a balance between charge density and steric effects, although the steric factors appear to have a stronger impact.…”

Section: [2+2]‐heterocycloadditions Via Direct Irradiation Of the Car...mentioning

confidence: 99%

Mechanisms and Synthetic Strategies in Visible Light‐Driven [2+2]‐Heterocycloadditions

Franceschi

¹

,

Cuadros

²

,

Goti

³

et al. 2023

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The synthesis of four membered heterocycles usually requires multi-step procedures and prefunctionalized reactants. A straightforward alternative is the photochemical [2+2]-heterocycloaddition between an alkene and a carbonyl derivative, conventionally based on the photoexcitation of this latter. However, this approach is limited by the absorption profile of the carbonyl, requiring in most of the cases the use of high-energy UV-light, that often results in undesired side reactions and/or the degradation of the reaction components. The development of new and milder visible light-driven [2+2]-heterocycloadditions is, therefore, highly desirable. In this Review, we highlight the most relevant achievements in the development of [2+2]-heterocycloadditions promoted by visible light, with a particular emphasis on the involved reaction mechanisms. The open challenges will also be discussed, suggesting new possible evolutions, and stimulating new methodological developments in the field. Mechanisms for Visible Light [2+2]-Hetero-CycloadditionsA prerequisite for visible light [2+2]-heterocycloadditions is the presence of a photoactive species able to absorb light

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“…[24,27] They questioned the generally accepted triplet mechanism, as they observed quenching of the reaction using singlet-state quenchers. [24] According to their observation, they proposed a PET from a singlet CT exciplex 17, with subsequent formation of the singlet diradicals 18 and 19, and ring closure to the oxetane products 15 and 16 (Figure 5a). The authors observed that the dimension of the cycle of the alkene has a strong impact on the regioselectivity of the process (Figure 5b).…”

Section: Quinonesmentioning

confidence: 99%

“…In fact, the product degradation was prevented while preserving the efficiency of the process. [24] In 1993, Ciufolini et al reported the photocycloaddition between 1,4-benzoquinones 13 and trisubstituted electronrich olefins 14 using an Ar-ion laser as a visible light source (Scheme 4). [25] The authors observed a high regioselectivity when using exocyclic olefins (products 15 b and 15 c), while poor selectivity was observed with acyclic olefins (product 15 a).…”

Section: Quinonesmentioning

confidence: 99%

Mechanisms and Synthetic Strategies in Visible Light‐Driven [2+2]‐Heterocycloadditions

Franceschi

¹

,

Cuadros

²

,

Goti

³

et al. 2023

View full text Add to dashboard Cite

The synthesis of four membered heterocycles usually requires multi-step procedures and prefunctionalized reactants. A straightforward alternative is the photochemical [2+2]-heterocycloaddition between an alkene and a carbonyl derivative, conventionally based on the photoexcitation of this latter. However, this approach is limited by the absorption profile of the carbonyl, requiring in most of the cases the use of high-energy UV-light, that often results in undesired side reactions and/or the degradation of the reaction components. The development of new and milder visible light-driven [2+2]-heterocycloadditions is, therefore, highly desirable. In this Review, we highlight the most relevant achievements in the development of [2+2]-heterocycloadditions promoted by visible light, with a particular emphasis on the involved reaction mechanisms. The open challenges will also be discussed, suggesting new possible evolutions, and stimulating new methodological developments in the field. Mechanisms for Visible Light [2+2]-Hetero-CycloadditionsA prerequisite for visible light [2+2]-heterocycloadditions is the presence of a photoactive species able to absorb light

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On the Mechanism of Oxetan Formation in the Photocycloaddition of p-Benzoquinone to Alkenes

Cited by 26 publications

References 7 publications

Spin trapping and electron spin resonance detection of radical intermediates in the photodecomposition of water at titanium dioxide particulate systems

Spin trapping and electron spin resonance detection of radical intermediates in the photodecomposition of water at titanium dioxide particulate systems

Mechanisms and Synthetic Strategies in Visible Light‐Driven [2+2]‐Heterocycloadditions

Mechanisms and Synthetic Strategies in Visible Light‐Driven [2+2]‐Heterocycloadditions

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