- Competing Pathways in the Phototransposition of Pyrazoles
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Cyano-substituted pyrazoles transpose photochemically into imidazoles by two concurrent paths: (a) 1,5-interchange, probably by 2,5-bonding to a diazabicyclopentene which isomerises by nitrogen 'walk' before rearomatisation, and (b) 2,3-interchange, probably via an intermediate azirine; in sharp contrast, 1,5-dimethyl-3-trifluoromethylpyrazole phototransposes exclusively by the former path.
- Barltrop, John A.,Day, A. Colin,Mack, Arthur G.,Shahrisa, Aziz,Wakamatsu, Shigeru
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- PHOTOCHEMICAL CONVERSION OF PYRAZOLES TO ENAMINONITRILES AND IMIDAZOLES
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Irradiation of pyrazole, 1-methylpyrazole and 4-cyano-1-methylpyrazole gave 3-aminoacrylonitrile, 3-methylaminoacrylonitrile and 2-cyano-3-methylaminoacrylonitrile along with corresponding imidazoles.A new pathway is proposed in which both enaminonitrile and imidazole are produced immediately from pyrazole, besides the sequence of pyrazole - enaminonitrile - imidazole.
- Wakamatsu, Shigeru,Barltrop, John A.,Day, A. Colin
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p. 667 - 670
(2007/10/02)
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