Photochemistry of 2-(1-Naphthyl)-2H-azirines in Matrixes and in Solutions:  Wavelength-Dependent C−C and C−N Bond Cleavage of the Azirine Ring

Abstract

The photochemistry of 3-methyl-2-(1-naphthyl)-2H-azirine (1a) was investigated by the direct observation of reactive intermediates in matrixes at 10 K and by the characterization of reaction products in solutions. As already reported, the photolysis of the azirine 1a with the short-wavelength light (>300 nm) caused the C-C bond cleavage of the 2H-azirine ring to produce the nitrile ylide 2. However, the products derived from the C-N bond cleavage were exclusively obtained in the irradiation of 1a with the long-wavelength light (366 nm) both in matrixes and in solutions. When 1a was irradiated in the presence of O(2) with the long-wavelength light, acetonitrile oxide (6) was produced through the capture of the biradical 4 generated by the C-N bond cleavage of 1a with O(2). An introduction of a nitro group into the naphthyl ring of 1a resulted in an acceleration of the decomposition in the long-wavelength irradiation and an extension of the wavelength region where the products derived from the C-N bond cleavage were selectively obtained. On the basis of molecular orbital calculations with the INDO/S method, the reason for the wavelength-dependent selective C-C and C-N bond cleavage of the azirine ring of 1a is discussed.

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

“…[15][16][17][18][19][20] However, photochemical cleavage of the C-N single bond was observed in some 2H-azirine derivatives that have an electron-withdrawing substitution at the C 2 atom of the azirine ring. [21][22][23] In fact, the preference of the C-C over C-N photocleavage depends on the nature of substituents and their positions in the azirine ring, besides the applied wavelength. 24,25 With respect to the C-N single bond photocleavage, it has been proposed to proceed by a mechanism involving triplet intermediates that were formed through an intersystem crossing from an excited singlet state.…”

“…24,25 With respect to the C-N single bond photocleavage, it has been proposed to proceed by a mechanism involving triplet intermediates that were formed through an intersystem crossing from an excited singlet state. [21][22][23][24][25][26] Our previous calculation, however, showed that the C-N single a) Author to whom correspondence should be addressed. Electronic mail:…”

Vinylnitrene Formation from 3,5-Diphenyl-isoxazole and 3-Benzoyl-2-phenylazirine

“…We were, however, not able to isolate any photoproducts that result from trapping the triplet vinylnitrene with oxygen, whereas Murata et al have previously reported that the vinylnitrene depicted in Scheme 2 can be trapped with molecular oxygen to form stable compounds. 19 In this study, we used laser flash photolysis to demonstrate that both isoxazole 1 and azirine 2 can serve as precursors for triplet vinylnitrene 4. As expected, vinylnitrene 4 is short-lived and decays by intersystem crossing to reform 1 and 2.…”

λ‐Orthogonal Pericyclic Macromolecular Photoligation

“…These photoactive groups were then attached to surfaces. [13] All the above studies either successfully establish the photo-triggered attachment of molecules onto surfaces, the release of small molecules from surfaces by irradiation, or the decomposition of photoactive molecules into smaller fragments. [11] Franking et al demonstrated the wavelength-dependent (254 nm vs. 350 nm) photochemical grafting of a set of alkenes onto single-crystal TiO 2 samples.…”