Competing pathways in the phototransposition of pyrazoles

JA Barltrop, AC Day, AG Mack, A Shahrisa…

Index: Barltrop, John A.; Day, A. Colin; Mack, Arthur G.; Shahrisa, Aziz; Wakamatsu, Shigeru Journal of the Chemical Society, Chemical Communications, 1981 , # 12 p. 604 - 606

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Citation Number: 3

Abstract

Cyano-substituted pyrazoles transpose photo-chemically 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.