- Photolysis of α-azidoacetophenones: Direct detection of triplet alkyl nitrenes in solution
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We report the first detection of triplet alkyl nitrenes in fluid solution by laser flash photolysis of α-azido acetophenone derivatives, 1. Azides 1 contain an intramolecular triplet sensitizer, which ensures formation of the triplet alkyl nitrene by bypassing the singlet nitrene intermediate. At room temperature, azides 1 cleave to form benzoyl and methyl azide radicals in competition with triplet energy transfer to form triplet alkyl nitrene. The major photoproduct 3 arises from interception of the triplet alkyl nitrene with benzoyl radicals. The triplet alkyl nitrene intermediates are also trapped with molecular oxygen to yield the corresponding 2-nitrophenylethanone. Laser flash photolysis of 1 reveals that the triplet alkyl nitrenes have absorption around 300 nm. The triplet alkyl nitrenes were further characterized by obtaining their UV and IR spectra in argon matrices. 13C and 15N isotope labeling studies allowed us to characterize the C-N stretch of the nitrene intermediate at 1201 cm-1.
- Singh, Pradeep N. D.,Mandel, Sarah M.,Robinson, Rachel M.,Zhu, Zhendong,Franz, Roberto,Ault, Bruce S.,Gudmundsdottir, Anna D.
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p. 7951 - 7960
(2007/10/03)
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- Photolysis of α-azidoacetophenones: Trapping of triplet alkyl nitrenes in solution
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(Matrix presented) Selective excitation of the ketone chromophore in α-azidoacetophenones, 1, leads to intramolecular triplet energy transfer to the azido group, which forms the corresponding triplet alkyl nitrene, 2. Azides 1 also undergo α-cleavage to form benzoyl and methyl azido radicals in competition with nitrene formation. Thus the major photoproduct, 2-benzoylamino-1-phenylethanone, 3, comes from trapping of 2 with a benzoyl radical. This appears to be the first observation of bimolecular trapping of triplet alkyl nitrenes in solution.
- Mandel, Sarah M.,Bauer, Jeanette A. Krause,Gudmundsdottir, Anna D.
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p. 523 - 526
(2007/10/03)
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