The catalytic diazotization of aryl amines was developed using ortho-naphthoquinone catalyst under aerobic conditions, where the 2-nitropropane served as a source of nitrosonium ion. The catalytic generation of diazonium species from aryl amines was further explored in the hydrode-diazotization to give the corresponding products. The mechanistic studies indicated the involvement of aryl radical species that readily underwent the radical cyclization to alkenes as well as the halogen abstraction reactions.