Triplet Sensitized Photolysis of a Vinyl Azide: Direct Detection of a Triplet Vinyl Azide and Nitrene

Rajam, Sridhar; Jadhav, Abhijit V.; Li, Qian; Sarkar, Sujan K.; Singh, Pradeep; Rohr, Ahleah; Pace, Tamara C. S.; Li, Rui; Krause, Jeanette A.; Bohne, Cornelia; Ault, Bruce S.; Guđmundsdóttir, Anna D.

doi:10.1021/jo501898p

Cited by 21 publications

(25 citation statements)

References 44 publications

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“…The calculated singlet triplet energy gap for vinylnitrene 2 is similar to those we have previously calculated for the vinylnitrenes shown in Scheme . Thus, the energy gap between the singlet and triplet configurations is not what controls the reactivity of vinylnitrenes at cryogenic temperatures.…”

Section: Discussionsupporting

confidence: 83%

“…As highlighted above, triplet vinylnitrenes have significant 1,3‐biradical character, which makes their vinyl bonds flexible. Furthermore, the calculated rotational barrier for the vinyl bond in vinylnitrene 2 is somewhat smaller than those we have reported for several triplet vinylnitrenes with α‐methyl groups (Scheme ) . The α‐phenyl group lowers the rotational barrier for vinylnitrene 2 because as the radicals centered on the nitrogen and carbon atoms rotate out of conjugation, the radical centered on the nitrogen atom is stabilized by conjugation with the α‐phenyl group.…”

Section: Discussioncontrasting

confidence: 52%

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Photolysis of 3,5‐diphenylisoxazole in argon matrices

Sriyarathne

Sarkar

Hatano

et al. 2016

J of Physical Organic Chem

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Broadband irradiation of 3,5‐diphenylisoxazole 1 in an argon matrix results in formation of azirine 3. Further irradiation of the matrix reduces the amount of azirine 3 with concurrent formation of ylide 4. Thus, it is theorized that the conversion of isoxazole 1 to azirine 3 goes through a triplet vinylnitrene 2 that does not intersystem cross to ketenimine 6. Hence, the reactivity of triplet vinylnitrene 2 is different from similar vinylnitrene intermediates with α‐methyl substituents that intersystem cross to form corresponding ketenimines. Density functional theory calculations support the notion that the conjugation of the α‐phenyl group to the vinylnitrene moiety in vinylnitrene 2 renders it more flexible than vinylnitrenes with α‐methyl substituents, and therefore, vinylnitrene 2 intersystem crosses to azirine 3, rather than ketenimine 6. Copyright © 2016 John Wiley & Sons, Ltd.

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Section: Discussionsupporting

confidence: 83%

Section: Discussioncontrasting

confidence: 52%

Photolysis of 3,5‐diphenylisoxazole in argon matrices

Sriyarathne

Sarkar

Hatano

et al. 2016

J of Physical Organic Chem

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“…26,61,[64][65][66] The triplet vinylnitrenes were observed in recent experiments. 24,66,[98][99][100] In contrast, the n → π * excitation of the imine chromophore, promoted at shorter wavelengths, should result in the C 2 -C 3 bond cleavage and produce the nitrile ylide intermediate through an internal conversion to a vibrationally hot ground state. As shown in Figure 2(b), the isomerization from the nitrile ylide to oxazole owns a lower barrier (ca.…”

Section: Mechanistic Aspectmentioning

confidence: 99%

Photoinduced reactions of both 2-formyl-2H-azirine and isoxazole: A theoretical study based on electronic structure calculations and nonadiabatic dynamics simulations

Cao

2015

The Journal of Chemical Physics

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In the present work, the combined electronic structure calculations and dynamics simulations have been performed to explore photocleavages of 2-formyl-2H-azirine and isoxazole in the gas phase and the subsequent rearrangement reactions. The carbonyl n → π(*) transition induces a cleavage of the C-N single bond of 2-formyl-2H-azirine to yield β-formylvinylnitrene in open-shell singlet state. However, the n → π(*) excitation of the imine chromophore results in a cleavage of the C-C single bond, producing a nitrile ylide intermediate through an internal conversion to the ground state. β-formylvinylnitrene and nitrile ylide with the carbonyl group are easily transformed into 2-formyl-2H-azirine and oxazole, respectively. The N-O bond cleavages on both S1((1)ππ(*)) and S2((1)nNπ(*)) of isoxazole are ultrafast processes, and they give products of 2-formyl-2H-azirine, 3-formylketenimine, HCN + CHCHO, and HCO + CHCHN. Both 2H-azirines and ketenimines were suggested to be formed from the triplet vinylnitrenes by intersystem crossing in the previous studies. However, our calculations show that the singlet β-formylvinylnitrene is responsible for the formation of 2-formyl-2H-azirine and 3-formylketenimine, and the singlet vinylnitrenes can play a key role in the photoinduced reactions of both 2H-azirines and isoxazoles.

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“…16 Recently, we established that the triplet sensitization of a vinyl azide can be used to form a vinylnitrene intermediate. 17 As vinyl azides are more versatile precursors than azirine or isoxazole derivatives, they enable the formation of a wide variety of vinylnitrenes with different and complex structures.…”

Section: ■ Introductionmentioning

confidence: 99%

Direct Detection of a Triplet Vinylnitrene, 1,4-Naphthoquinone-2-ylnitrene, in Solution and Cryogenic Matrices

et al. 2015

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The photolysis of 2-azido-1,4-naphthoquinone (1) in argon matrices at 8 K results in the corresponding triplet vinylnitrene (3)2, which was detected directly by IR spectroscopy. Vinylnitrene (3)2 is stable in argon matrices but forms 2-cyanoindane-1,3-dione (3) upon further irradiation. Similarly, the irradiation of azide 1 in 2-methyltetrahydrofuran (MTHF) matrices at 5 K resulted in the ESR spectrum of vinylnitrene (3)2, which is stable up to at least 100 K. The zero-field splitting parameters for nitrene (3)2, D/hc = 0.7292 cm(-1) and E/hc = 0.0048 cm(-1), verify that it has significant 1,3-biradical character. Vinylnitrene (3)2 (λmax ∼ 460 nm, τ = 22 μs) is also observed directly in solution at ambient temperature with laser flash photolysis of 1. Density functional theory (DFT) calculations support the characterization of vinylnitrene (3)2 and the proposed mechanism for its formation. Because vinylnitrene (3)2 is relatively stable, it has potential use as a building-block for high-spin assemblies.

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Triplet Sensitized Photolysis of a Vinyl Azide: Direct Detection of a Triplet Vinyl Azide and Nitrene

Cited by 21 publications

References 44 publications

Photolysis of 3,5‐diphenylisoxazole in argon matrices

Photolysis of 3,5‐diphenylisoxazole in argon matrices

Photoinduced reactions of both 2-formyl-2H-azirine and isoxazole: A theoretical study based on electronic structure calculations and nonadiabatic dynamics simulations

Direct Detection of a Triplet Vinylnitrene, 1,4-Naphthoquinone-2-ylnitrene, in Solution and Cryogenic Matrices

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