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Photocatalyst size controls electron and energy transfer: selectable E / Z isomer synthesis via C – F alkenylation † † Electronic supplementary information (ESI) available. See DOI: 10.1039/c6sc02422j

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ABSTRACT

Photocatalytic alkene synthesis can involve electron and energy transfer processes. The structure of the photocatalyst can be used to control the rate of the energy transfer, providing a mechanistic handle over the two processes. Jointly considering catalyst volume and emissive energy provides a highly sensitive strategy for predicting which mechanistic pathway will dominate. This model was developed en route to a photocatalytic Caryl–F alkenylation reaction of alkynes and highly-fluorinated arenes as partners. By judicious choice of photocatalyst, access to E- or Z-olefins was accomplished, even in the case of synthetically challenging trisubstituted alkenes. The generality and transferability of this model was tested by evaluating established photocatalytic reactions, resulting in shortened reaction times and access to complimentary Z-cinnamylamines in the photocatalytic [2 + 2] and C–H vinylation of amines, respectively. These results show that taking into account the size of the photocatalyst provides predictive ability and control in photochemical quenching events.

No MeSH data available.


Working mechanism.
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sch2: Working mechanism.

Mentions: Our current understanding is shown in Scheme 2. In which absorption of a photon gives rise to an excited state catalyst, PC*. In the absence of an isomerizable group, PC* may enter the electron transfer cycle. In which oxidative or reductive quenching may be at work depending on photocatalyst and substrate choice.3b Ultimately, in the case of perfluoroarenes, electron transfer to the perfluoroarene ArFn leads to fluoride extrusion and formation of a multifluorinated aryl radical, ArFn–1.


Photocatalyst size controls electron and energy transfer: selectable E / Z isomer synthesis via C – F alkenylation † † Electronic supplementary information (ESI) available. See DOI: 10.1039/c6sc02422j
Working mechanism.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5134729&req=5

sch2: Working mechanism.
Mentions: Our current understanding is shown in Scheme 2. In which absorption of a photon gives rise to an excited state catalyst, PC*. In the absence of an isomerizable group, PC* may enter the electron transfer cycle. In which oxidative or reductive quenching may be at work depending on photocatalyst and substrate choice.3b Ultimately, in the case of perfluoroarenes, electron transfer to the perfluoroarene ArFn leads to fluoride extrusion and formation of a multifluorinated aryl radical, ArFn–1.

View Article: PubMed Central - PubMed

ABSTRACT

Photocatalytic alkene synthesis can involve electron and energy transfer processes. The structure of the photocatalyst can be used to control the rate of the energy transfer, providing a mechanistic handle over the two processes. Jointly considering catalyst volume and emissive energy provides a highly sensitive strategy for predicting which mechanistic pathway will dominate. This model was developed en route to a photocatalytic Caryl–F alkenylation reaction of alkynes and highly-fluorinated arenes as partners. By judicious choice of photocatalyst, access to E- or Z-olefins was accomplished, even in the case of synthetically challenging trisubstituted alkenes. The generality and transferability of this model was tested by evaluating established photocatalytic reactions, resulting in shortened reaction times and access to complimentary Z-cinnamylamines in the photocatalytic [2 + 2] and C–H vinylation of amines, respectively. These results show that taking into account the size of the photocatalyst provides predictive ability and control in photochemical quenching events.

No MeSH data available.