“…The 31 P NMR data also show evidence for the phosphorane 4 (−49.6 ppm) (Figure S4) in which the phosphorus atom is covalently bound to five oxygen atoms. Similar negative chemical shifts have been observed for other phosphoranes …”
Section: Resultssupporting
confidence: 87%
“…Similar negative chemical shifts have been observed for other phosphoranes. 12 The appearance of trimethylphosphate [(MeO) 3 PO] is a consequence of the phosphorane 4 decomposition via aryl migration, a side reaction leading to ketene. Based on the literature of ketenes, 11 cleavage of phosphorane 4 is expected to lead to (p-MeC 6 H 4 ) 2 CCO, (MeO) 3 PO, and byproducts, although we did not analyze these downstream reactions.…”
Section: ■ Resultsmentioning
confidence: 99%
“…For example, benzils bind to tubulin proteins in a similar manner as stilbenes, such as combretastatin A-4 . Furthermore, diones have been shown to be important in chelation reactions with phosphites , and have been used in the synthesis of phosphoranes. , Diones such as 4,4′-dimethylbenzil 1 and monocarbonyl compounds have been used as photosensitizers in photooxidation reactions − but not in the terms of dione conformational binding and photosensitization as we describe here. Indeed, the dual functionality of diones for photosensitization and subsequent binding has not been previously explored.…”
Few photosensitizers function in both light and dark
processes
as they usually have no function when the lights are turned off. We
hypothesized that light and dark mechanisms in an α-diketone
will be decoupled by dihedral rotation in a conformation-dependent
binding process. Successful decoupling of these two functions is now
shown. Namely, anti- and syn-skewed
conformations of 4,4′-dimethylbenzil promote photosensitized
alkoxy radical production, whereas the syn conformation
promotes a binding shutoff reaction with trimethyl phosphite. Less
rotation of the diketone is better suited to the photosensitizing
function since phosphite binding arises through the syn conformer of lower stability. The dual function seen here with the
α-diketone is generally not available to sensitizers of limited
conformational flexibility, such as porphyrins, phthalocyanines, and
fullerenes.
“…The 31 P NMR data also show evidence for the phosphorane 4 (−49.6 ppm) (Figure S4) in which the phosphorus atom is covalently bound to five oxygen atoms. Similar negative chemical shifts have been observed for other phosphoranes …”
Section: Resultssupporting
confidence: 87%
“…Similar negative chemical shifts have been observed for other phosphoranes. 12 The appearance of trimethylphosphate [(MeO) 3 PO] is a consequence of the phosphorane 4 decomposition via aryl migration, a side reaction leading to ketene. Based on the literature of ketenes, 11 cleavage of phosphorane 4 is expected to lead to (p-MeC 6 H 4 ) 2 CCO, (MeO) 3 PO, and byproducts, although we did not analyze these downstream reactions.…”
Section: ■ Resultsmentioning
confidence: 99%
“…For example, benzils bind to tubulin proteins in a similar manner as stilbenes, such as combretastatin A-4 . Furthermore, diones have been shown to be important in chelation reactions with phosphites , and have been used in the synthesis of phosphoranes. , Diones such as 4,4′-dimethylbenzil 1 and monocarbonyl compounds have been used as photosensitizers in photooxidation reactions − but not in the terms of dione conformational binding and photosensitization as we describe here. Indeed, the dual functionality of diones for photosensitization and subsequent binding has not been previously explored.…”
Few photosensitizers function in both light and dark
processes
as they usually have no function when the lights are turned off. We
hypothesized that light and dark mechanisms in an α-diketone
will be decoupled by dihedral rotation in a conformation-dependent
binding process. Successful decoupling of these two functions is now
shown. Namely, anti- and syn-skewed
conformations of 4,4′-dimethylbenzil promote photosensitized
alkoxy radical production, whereas the syn conformation
promotes a binding shutoff reaction with trimethyl phosphite. Less
rotation of the diketone is better suited to the photosensitizing
function since phosphite binding arises through the syn conformer of lower stability. The dual function seen here with the
α-diketone is generally not available to sensitizers of limited
conformational flexibility, such as porphyrins, phthalocyanines, and
fullerenes.
“…The source of triaryl phosphate was examined, in which the chelation of the phosphite relies on the conversion of the trans ‐dione 1 to the reactive syn ‐ or syn‐ skewed ‐ dione 1 conformer. [ 12 ] The results in path B supplement others [ 13–16 ] and our [ 12 ] previous work on phosphite chelation of diones and the NMR detection of the transient dioxaphosphole. Conceivable by‐products are also α‐hydroxyvinyl phosphates, but were not detected by NMR.…”
With interests in alkoxy radical formation on natural and artificial surfaces, a physical‐organic study was carried out with a Hammett series of triaryl phosphites (p‐MeO, H, p‐F, and p‐Cl) to trap adsorbed alkoxy radicals on silica nanoparticles. A mechanism which involves PhC (Me)2O• and EtO• trapping in a cumylethyl peroxide sensitized homolysis reaction is consistent with the results. The p‐F phosphite was able to indirectly monitor the alkoxy radical formation, and 31P NMR readily enabled this exploration, but other phosphites of the series such as the p‐MeO phosphite were limited by hydrolysis reactions catalyzed by surface silanol groups. Fluorinated silica nanoparticles helped to suppress the hydrolysis reaction although adventitious water also plays a role in hindering efficient capture of the alkoxy radicals by the phosphite traps.
“…The Wittig reaction of α-dicarbonyl compounds 17 (R 1 = R 2 = H, Me, Ph, 2-furyl) with methylene(triphenyl)phosphoranes 107 (R = Et, Ph, CN, COMe, COPh, COOMe, COOEt) affords the alkene formation at only one of the two possible carbonyl groups − to produce ( Z )- and ( E )-isomeric adducts 108 . , …”
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