Reactive Intermediates Produced in the Decomposition of 2-Diazoketone : Mechanism of the Wolff Rearrangement

Abstract

Potential energy hypersurfaces of the nitrogen elimination and the Wolff rearrangement were investigated for both cyclic and open-chain 2-diazoketones by means of semi-empirical MINDO/3 molecular orbital calculations with configuration interaction. In the case of 2-diazobenzen-1-one, the nitrogen elimination takes place simultaneously with the Wolff rearrangement in a concerted fashion and neither ketocarbene nor oxirene is produced. In contrast to the cyclic 2-diazoketone, 2-diazoethan-1-one produces oxirene through nitrogen elimination in a concerted fashion. The oxirene isomerizes to ketene via the Wolff rearrangement, passing over a second saddle point of low energy. No ketocarbene intermediate is produced in either case.