Reaction of Triarylphosphine Radical Cations Generated from Photoinduced Electron Transfer in the Presence of Oxygen

Yasui, Shinro; Tojo, Sachiko; Majima, Tetsuro

doi:10.1021/jo049032l

Cited by 57 publications

(31 citation statements)

References 39 publications

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“…are particularly noteworthy, as phosphoniumyl radicals (R3P• + ) have been at the forefront of phosphorus centred radical chemistry. [14][15][16] They have been suggested as intermediates in the oxidation of phosphines to their respective oxides, 17,18 and most recently in FLP chemistry. 19 However, this initiation step seems unlikely, as the rate of reaction was observed to decrease in a more polar solvent (benzonitrile).…”

Section: S72 -Initiation Without a Radical Initiatormentioning

confidence: 99%

Dealkanative Main Group Couplings across the peri-Gap

et al. 2017

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Here, we highlight the ability of peri-substitution chemistry to promote a series of unique P-P/P-As coupling reactions, which proceed with concomitant C-H bond formation. This dealkanative reactivity represents an interesting and unexpected expansion to the established family of main-group dehydrocoupling reactions. These transformations are exceptionally clean, proceeding essentially quantitatively at relatively low temperatures (70-140 °C), with 100% diastereoselectivity in the products. The reaction appears to be radical in nature, with the addition of small quantities of a radical initiator (azobis(isobutyronitrile)) increasing the rate dramatically, as well as altering the apparent order of reaction. DFT calculations suggest that the reaction involves dissociation of a phosphorus centered radical (stabilized by the peri-backbone) to the P-P coupled product and a free propyl radical, which carries the chain. This unusual reaction demonstrates the powerful effect that geometric constraints, in this case a rigid scaffold, can have on the reactivity of main group species, an area of research that is gaining increasing prominence in recent years.

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Section: S72 -Initiation Without a Radical Initiatormentioning

confidence: 99%

Dealkanative Main Group Couplings across the peri-Gap

et al. 2017

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“…Radical coupling between 1 ●+ and O 2 ●− followed by collapse of the resulting zwitterion intermediate is a possibility to give 2 . However, if this is the case , the observed rate would follow second‐order kinetics because the concentrations of 1 ●+ and O 2 ●− are the same, which is against our observation shown by Equation …”

Section: Discussionmentioning

confidence: 99%

³¹P NMR spectroscopic analysis on photooxidation of 1,n‐bis(diphenylphosphino)alkanes with the aid of DFT calculations

Yasui

Yamazaki

2020

J of Physical Organic Chem

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The chloroform‐d solution of diphosphine, 1,n‐bis(diphenylphosphino)alkane (Ph2P(CH2)nPPh2; n = 1‐6), was photolyzed with light from a xenon lamp in air. The progress of the reaction was followed by 31P NMR spectroscopy. The observed spectral change showed that the diphosphine is initially oxidized to diphosphine monoxide, Ph2P(═O)(CH2)nPPh2, which is further oxidized to diphosphine dioxide, Ph2P(═O)(CH2)nP(═O)Ph2. The oxidation of the diphosphine to the diphosphine monoxide took place according to first‐order kinetics with respect to the concentration of the diphosphine, the first‐order rate constant, kobs, being larger with increasing number of the methylene units in the spacer. The observation in kinetics is interpreted based on the conformation of the diphosphine radical cation intermediate initially generated by electron transfer from the photoexcited diphosphine to oxygen. Density functional theory (DFT) calculations predict that the diphosphine radical cation takes “folded” conformation where two phosphorus atoms are arranged closely to each other. The “folded” conformer of the diphosphine radical cation results from electrostatic interaction of these two phosphorus atoms. This conformer explains the observed dependency of kobs on the length of the spacer in the diphosphine.

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“…[6] The generation of 1 •+ is interpreted as follows: upon the laser flash at 266 nm, 1 is excited to its singlet excited state 1 1*, which, either directly from this state or after intersystem crossing to its triplet state, undergoes electron transfer (ET) to O 2 . [7] The ET generates a radical ion pair, 1…”

Section: Reaction Pathwaysmentioning

confidence: 99%

Combination of LFP-TRIR spectroscopy and DFT computation as a tool to determine the intermediate during the photooxidation of triarylphosphine

Yasui

Badal

Kobayashi

et al. 2014

J. Phys. Org. Chem.

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Laser flash photolysis-time-resolved infrared spectroscopy (LFP-TRIR) was performed on an acetonitrile or dichloromethane solution of triarylphosphines, Ar 3 P, in air. A transient spectrum consisting of several absorption bands appeared in the region of 1050-1300 cm À1 on the TRIR on a microsecond timescale, which disappeared on a millisecond timescale. To identify the observed transient intermediate, the IR spectra of possible intermediates of the photoreaction were simulated by theoretical calculations based on density functional theory (DFT). The IR spectrum simulated for the phosphine peroxidic radical cation, Ar 3 P + OO• , well predicted the observed IR spectrum, showing that Ar 3 P + OO• is formed as a transient intermediate upon the LFP of Ar 3 P in air.

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Reaction of Triarylphosphine Radical Cations Generated from Photoinduced Electron Transfer in the Presence of Oxygen

Cited by 57 publications

References 39 publications

Dealkanative Main Group Couplings across the peri-Gap

Dealkanative Main Group Couplings across the peri-Gap

³¹P NMR spectroscopic analysis on photooxidation of 1,n‐bis(diphenylphosphino)alkanes with the aid of DFT calculations

Combination of LFP-TRIR spectroscopy and DFT computation as a tool to determine the intermediate during the photooxidation of triarylphosphine

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Reaction of Triarylphosphine Radical Cations Generated from Photoinduced Electron Transfer in the Presence of Oxygen

Cited by 57 publications

References 39 publications

Dealkanative Main Group Couplings across the peri-Gap

Dealkanative Main Group Couplings across the peri-Gap

31P NMR spectroscopic analysis on photooxidation of 1,n‐bis(diphenylphosphino)alkanes with the aid of DFT calculations

Combination of LFP-TRIR spectroscopy and DFT computation as a tool to determine the intermediate during the photooxidation of triarylphosphine

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³¹P NMR spectroscopic analysis on photooxidation of 1,n‐bis(diphenylphosphino)alkanes with the aid of DFT calculations