Oxidation of an allene compound bearing 1,8‐dichloroacridene moieties and photolysis of the halogenated allene compound for the generation of triplet carbenes†
This article is published in Journal of Physical Organic Chemistry as a special issue on the International Symposium on Reactive Intermediates and Unusual Molecules 2014 on Physical Organic Chemistry by Robert Moss (Rutgers University USA) and Anna Gudmundsdottir (University of Cinncinnati, USA).
Abstract
New allene compounds, 5c and 5d, bearing 1,8‐dichloroacridene moieties were synthesized, and the oxidation of 5c and 5d was performed to generate thermally stable triplet carbenes. Since the oxidation resulted in the formation of decomposition products, the photolysis of brominated allene compound 18 was performed. UV–vis measurement at low temperatures indicated the generation of intermediates with decreasing starting material 18, although the efficiency of photolysis was quite low. ESR and electron spin transient nutation (ESTN) spectra suggested that the multiplicity of intermediates is triplet, probably the target triplet carbene 6d is generated. In terms of |D| values of the intermediates, ESR showed that unpaired electrons are more effectively delocalized in 6d by the introduction of nitrogen atoms in the skeleton (biradical character in Scheme 1). The observed triplet species 6d was not stable enough to isolate. Copyright © 2014 John Wiley & Sons, Ltd.
