1,5-(1,7)-Biradicals and Nitrenes Formed by Ring Opening of Hetarylnitrenes
Curt Wentrup A B and David Kvaskoff AA School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia.
B Corresponding author. Email: wentrup@uq.edu.au
Australian Journal of Chemistry 66(3) 286-296 https://doi.org/10.1071/CH12502
Submitted: 7 November 2012 Accepted: 18 December 2012 Published: 11 February 2013
Abstract
Several aromatic and heteroaromatic nitrenes and carbenes undergo photochemical and sometimes also thermal ring opening. Depending on benz-annelation, the ring-opened species may have the character of either nitrenes (for α-annelation) or 1,5-(1,7-)-biradicals (for β-annelation). Both types have been observed, and they are clearly distinguished by their characteristic electron spin resonance spectra. In addition, ring opening of hetarylnitrenes to nitrile ylides can be observed whenever there is a meta-relationship between a ring nitrogen atom and the nitrene (or carbene) centre. The factors governing the two types of ring opening have been investigated. The nitrenes and carbenes are generated by either low temperature Ar matrix photolysis or flash vacuum thermolysis of azides, tetrazoles, triazoles, or diazo compounds with matrix isolation of the products.
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