Autoxidation und Wasserstoffperoxid‐Oxidation von 2,4,6‐Triphenyl‐λ³‐phosphorin

Abstract

2,4,6-Tripheiiyl-'h~-pliosphorin (1) wird in Benzol laiigsani durch dcn darin gelosten Luftsauerstoff oxidiert. Zwei kristallisicrtc Oxidationsprodukte wurden isoliert. Die tieferschmelzende Verbindung ist 4,4'-Dioxyhis(J-hydroxy-l-oxo-2,4,6-triphenyl-As-l-phospha-2,5-cyclohcxadicn) (2). Alkylierung mit Triathyloxonium-tetrafluoroborat liefert die drei stereoisomeren Phosphinsaureester 4€,E, 4€,Z und 4Z,2, deren Spaltung mit Zink und Eisessig zwei stereoisomere Hydroxyphosphinsaurc-athylester 5 E und Z ergibt. Die sterische Zuordnung gelang mit Hilfe der IH-NMR-Spektren.Wasserstoffperoxid-Oxidation von 1 liefert I-Hydroxy-l-ox0-2,4,6-triphenyl-h~-l-phospha-2,4-cyclohexadiene (3). Mit Triathyloxonium-tetrafluoroborat entsteht das auch auf anderem Wege aus 1 zuginglkhe J,1 -Diathoxy-2,4,6-triphenyl-i.-5-phosphorin (6) neben I-Athoxy-6-athyl-1-oxo-2,4,6-triphenyl-A~-l-phospha-2,4-cyclohexadien (13). Autoxidation and Hydrogen Peroxide Oxidation of 2,4,6-Triphenyl-X3-phosphorin2,4,6-Triphenyl-A3-phosphorin (1) is slowly oxidized in benzene solution by dissolvcd oxygen. Two crystalline oxidation products "ere isolated. The structure of the lower melting substance is 4,4'-dioxybis(l-hydroxy-l-oxo-2,4,6-triphenyl-h~-l-phospha-2,5-cyclohexadiene) (2). Alkylation with triethyloxonium tetrafluoroborate leads to three stereoisomeric phosphinates 4E,E, 4E,Z, 4Z,2, which by reduction with zinc in acetic acid yield two stereoisomeric ethyl hydroxyphosphinates 5E and 2. Steric assignment was made on the basis of the 1H n. m. r. data. Hydrogen peroxide oxidation of 1 yields J-liydroxy-l-oxo-2,4,6-tr~phenyl-h~-l-phospha-2,4-cyclohexadiene (3). Treatment with triethyloxonium tetrafluoroborate yields 1,l-dicthoxy-2,4,6-triphenyl-As-phosphorin (6) which was also prepared by another synthetic route and J-ethoxy-6-ethyl-] -oxo-2,4,6-triphcnyl-)~~-1-phospha-2,4-cyclohexadiene (13). Eildung und Eigenschaften der Dioxybis(phosphinsaure) 22,4,6-Triphenyl-)&phosphorin (1) und audere arylierte As-Phosphorine werden langsam an der Luft oxidiert. LBBt man eine Losung von 1 in Benzol, das relativ vie1 Sauerstoff lost, etwa 1 Woche im Dunkeln stehen, dann scheiden sich Kristalle vom Schmp. 165" aus. Eine zweite Verbindung vom Schmp. 225" liiI3t sich beim Einengen aus der Benzol-Losung isolierenl). Wahrend die Struktur der hoherschmelzenden Verbindung mit der Summenformel C46H3603P2 noch nicht sicher ist, konnte die der tieferschmelzenden Verbindung jetzt in allen Einzelheiten aufgeklart werden. Abweichend von unserer fruheren Feststellung1) enthalt die Summenformel ein 0-Atom

Atom Swapping on Aromatic Rings: Conversion from Phosphinine Pincer Metal Complexes to Metallabenzenes Triggered by O2 Oxidation

“…Finally, the dimerization of the metaphosphite moiety afforded iridabenzene 5 (step d) [20] . With regards to step a, the treatment of phosphinine with hydrogen peroxide or oxygen gas is known to afford the corresponding λ 5 ‐phosphinine derivatives [21] . Regarding step b, reactions involving the oxidative addition of a C−P bond have been reported [22] .…”

“…gen peroxide or oxygen gas is known to afford the corresponding λ 5 -phosphinine derivatives. [21] Regarding step b, reactions involving the oxidative addition of a CÀ P bond have been reported. [22] For the rhodium complex 4, oxidation of the phosphinine ring (step a) proceeded similar to the iridium complex 3 to afford intermediate I Rh .…”

Atom Swapping on Aromatic Rings: Conversion from Phosphinine Pincer Metal Complexes to Metallabenzenes Triggered by O2 Oxidation

“…Chemie gen peroxide or oxygen gas is known to afford the corresponding λ 5 -phosphinine derivatives. [21] Regarding step b, reactions involving the oxidative addition of a CÀ P bond have been reported. [22] For the rhodium complex 4, oxidation of the phosphinine ring (step a) proceeded similar to the iridium complex 3 to afford intermediate I Rh .…”

Elimination reactions in 1,4-diphosphinine chemistry: mixed-valence intermediates and 1,1- vs. 1,4-elimination pathways

“…2–4 A plethora of functionalisation facets are known to date, ranging from 1,4-addition reactions to give II or III , 5–7 or 1,1-oxidations furnishing phosphoranes ( IV ) or phosphane oxides ( V ). 8–10 Research on phosphinines remains very active, 11,12 and a very interesting example of water addition was published by Müller in 2024 13 (Chart 1, bottom): pyridinyl-substituted VI reacted reversibly with H 2 O to form VII , but applying vacuum returned VI at ambient temperature.…”

“…[2][3][4] A plethora of functionalisation facets are known to date, ranging from 1,4-addition reactions to give II or III, [5][6][7] or 1,1-oxidations furnishing phosphoranes (IV) or phosphane oxides (V). [8][9][10] Research on phosphinines remains very active, 11,12 14 the first isolation of a 1,4-diphosphinine was not achieved until 2017 when Streubel et al synthesised a tricyclic, imidazole-2-thione-fused derivative (IX, Chart 2). 15 Since then, the scope of fused five-membered heterocycles has expanded, i.e., incorporating 1,3-thiazole-and 1,3-dithiole-2thiones 16,17 as well as different substitutions in C 2 -position, i.e., selones, 18 TTF-motifs 19 and a 2-phenylimidazolium-fused example, the latter was reported by Ghadwal et al 20 Several different reactivity studies on 1,4-diphosphinines IX have been performed, such as [4 + 2]-cycloaddition [21][22][23] and 1,4-addition reactions, 16,22 the latter yielding σ 3 λ 3 -1,4-dihydro-1,4-diphosphinine structural motifs.…”