Ionic-Type Reactivity of 1,3-Dibora-2,4-diphosphoniocyclobutane-1,3-diyls: Regio- and Stereoselective Addition of Hydracids

Fuks, Gad; Saffon, Nathalie; Maron, Laurent; Bertrand, Guy; Bourissou, Didier

doi:10.1021/ja903746p

Cited by 34 publications

(28 citation statements)

References 110 publications

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“…[19] The chemistry of the planar singlet diradicaloids has been extensively studied using the extremelyl ong-lived singlet 2,2-dialkoxypropane-1,3-diyls pl-1 DR5 (Ar = Ph, X = OMe; l max at % 570 nm, [20] and the diradicaloidso fh eterocyclic systems. [21][22][23][24][25][26][27][28][29] In this study ac urious absorption band with l max at % 450 nm was found together with the planar singlet diradical pl-1 DR6 with l max at % 580 nm during the photochemical denitrogenation of AZ6 [30] bearing stericallyh indering substituents Ar (= dimethoxyphenyl) and X( = OCH 2 Ph). Based on product analyses, spectroscopic observations, and high-levelc omputational studies, the absorption signal at % 450 nm was assigned to the third isomer in the homolysis, that is, the puckered singlet diradicaloid puc-1 DR6 (Scheme 2).…”

Section: Introductionmentioning

confidence: 85%

A Puckered Singlet Cyclopentane‐1,3‐diyl: Detection of the Third Isomer in Homolysis

Hatano

Abe

et al. 2016

Chemistry A European J

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In the photochemical denitrogenation of 1,4-diaryl-2,3-diazabicyclo[2.2.1]heptane (AZ6) bearing sterically hindered substituents, a curious new absorption band at about 450 nm was observed under low-temperature matrix conditions, together with the previously well-characterized planar singlet diradical pl-(1) DR6 with λmax =≈580 nm. The 450 nm species was electron paramagnetic resonance (EPR)-silent. Instead of generating the planar diradical pl-(1) DR6 and the precursor azoalkane AZ6 upon warming, the ring-closed bicyclo[2.1.0]pentane derivative SB6, that is, the AZ6 denitrogenation product was identified. Based on product analysis, low-temperature spectroscopic observations, high-level quantum-mechanical computations, viscosity effect, and laser-flash photolysis, the puckered singlet diradicaloid puc-(1) DR6 was assigned to the new 450 nm absorption. The latter was detected experimentally at the same time as the planar singlet diradical pl-(1) DR6. Sterically demanding substituents as well as viscosity impediments were essential for the detection of the experimentally hitherto unknown puckered singlet cyclopentane-1,3-diyl diradicaloid puc-(1) DR6, that is, the third isomer in homolysis. The present findings should stimulate future work on the mechanistically fascinating stereoselectivity documented in the formation of bicyclo[2.1.0]pentanes during the 2,3-diazabicyclo[2.2.1]heptane denitrogenation.

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Section: Introductionmentioning

confidence: 85%

A Puckered Singlet Cyclopentane‐1,3‐diyl: Detection of the Third Isomer in Homolysis

Hatano

Abe

et al. 2016

Chemistry A European J

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“…The 2 J PP constant of 13 (31.6 Hz) is smaller than that of the 1λ 5 ,3λ 5 -diphosphete system. The 19 F NMR spectrum showed a resonance accompanying spin−spin coupling with the skeletal phosphorus atoms at δ F = −31.1, which is lower than that observed with 1λ 5 ,3λ 5 -diphosphetes. Although the reaction mechanism has not been verified, it is plausible that the intermediary 1λ 5 ,3λ 5 -diphosphete is protonated, 13 and subsequently the P−H proton is removed.…”

Section: Inorganic Chemistrymentioning

confidence: 54%

Chemical Detection of Hydrogen Fluoride by the Phosphorus Congener of Cyclobutane-1,3-diyl

2015

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Heteroaryl-substituted air-tolerant 2,4-bis(2,4,6-tri-t-butylphenyl)-1,3-diphosphacyclobutane-2,4-diyls in the open-shell singlet state were synthesized by a sterically promoted regioselective S(N)Ar process. Here we demonstrate that these diyls are effective for capturing hydrogen fluoride (HF) generated by intermediary base-coordinated HF and amine-stabilized HF reagents. The hydrofluorination reaction predominantly occurred on the λ(3)σ(3)-phosphorus atoms to afford the energetically disfavored 1λ(5),3λ(5)-diphosphete. The positively charged t-butyl-substituted phosphorus atom trapped the fluoride anion, and the subsequent protonation was controlled by the steric effect. X-ray crystallographic analysis and an Atoms in Molecule study of the air-stable 1λ(5),3λ(5)-diphosphete bearing P-H and P-F bonds revealed that the delocalized ylidic linkages in the four-membered ring were almost identical, in contrast to the nonsymmetrically substituted 2,4-bis(2,4,6-tri-t-butylphenyl)-1,3-diphosphacyclobutane-2,4-diyl. Hydrofluorination efficiently induced a remarkable exchange of visible photoabsorption. The charge-transfer-type transition from highest occupied molecular orbital to lowest unoccupied molecular orbital was highly tuned, which is advantageous for the facile identification of HF. In contrast to hitherto known trapping reagents for HF based on cleavage of the H-F bond, several hydrofluorinated P-heterocycles were reconverted into the 1,3-diphosphacyclobutane-2,4-diyl by treatment with sodium hydride. However, in the hydrofluorination of the benzoyl-substituted 1,3-diphosphacyclobutane-2,4-diyl, fluorination and protonation occurred at the t-butyl-substituted phosphorus atom and the skeletal carbon atom, respectively, and the energetically preferable 1λ(5),3λ(3)-dihydrodiphosphete was isolated as a purple-blue crystalline compound. These findings are promising not only for the practical detection of HF but also for the development of fluorine technology based on the chemistry of phosphorus heterocycles.

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“…5 Implicitly, biradicals are highly reactive species, which allows a rich follow-up chemistry. [6][7][8][9][10][11] The term biradicaloids used throughout this paper refers to a subset of biradicals with two radical centers interacting significantly. 12…”

Section: Introductionmentioning

confidence: 99%

Tunable Cyclopentane-1,3-diyls Generated by Insertion of Isonitriles into Diphosphadiazanediyls

2015

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Diphosphadiazanediyl ([P(μ-NTer)]2, 1) is known to readily react with small molecules bearing multiple bonds to give [2.1.1]bicyclic species. On the contrary, in the reaction of isonitriles with 1, planar five-membered heterocycles (3) with biradical character are formed by insertion of the carbon atom into one P-N bond. Under irradiation, heterocyclic biradicaloids 3 are shown to generate housane-type [2.1.0]bicyclopentanes by transannular bond formation. However, these housane species thermally equilibrate, reforming the open-shell singlet cyclopentanediyl. The biradical character of 3 indicates high reactivity which is further demonstrated in the activation of small molecules bearing multiple bonds leading to [2.2.1]bicyclic heterocycles. Depending on the substituent of the isonitrile, the reaction with a second equivalent of isonitrile is also observed for smaller substituents. By employing suitable diisonitriles, even the catenation of two open-shell singlet cyclopentane-1,3-diyls is achieved. CASSCF(6,6) computations revealed biradical character for 3 ranging between 26 and 27%.

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Ionic-Type Reactivity of 1,3-Dibora-2,4-diphosphoniocyclobutane-1,3-diyls: Regio- and Stereoselective Addition of Hydracids

Cited by 34 publications

References 110 publications

A Puckered Singlet Cyclopentane‐1,3‐diyl: Detection of the Third Isomer in Homolysis

A Puckered Singlet Cyclopentane‐1,3‐diyl: Detection of the Third Isomer in Homolysis

Chemical Detection of Hydrogen Fluoride by the Phosphorus Congener of Cyclobutane-1,3-diyl

Tunable Cyclopentane-1,3-diyls Generated by Insertion of Isonitriles into Diphosphadiazanediyls

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