Stereoselective Anti-Markovnikov Geminal Diamination and Dioxygenation of Vinylarenes Mediated by the Bromonium Ion

A straightforward method is reported for the stereoselective anti-Markovnikov geminal diamination and stoichiometric geminal dioxygenation of vinylarenes mediated by a bromonium ion. The role of the substituent on the nucleophile and the nucleophilicity of the heteroatom in the competing geminal and vicinal addition pathways has been described. The stereoselectivity of the geminal dioxygenation is dependent on the ring size of the product and the position of the substituent that induces the stereoselectivity. The migration of the phenyl group through a semi-pinacol rearrangement during the geminal addition process was confirmed by the results of deuterium labelling studies.