The　vicinal　diamine　motif　plays　a　significant　role　in　natural　products,　drug　design,　and　organic　synthesis,　and　development　of　synthetic　methods　for　the　synthesis　of　diamines　is　a　long-standing　interest.　Herein,　we　report　a　regioselective　intermolecular　three-component　vicinal　diamination　of　styrenes　with　acetonitrile　and　azodicarboxylates.　The　diamination　products　can　be　produced　in　moderate　to　excellent　yields　via　the　Ritter　reaction.　Synthetic　applications　and　theoretical　studies　of　this　reaction　have　been　conducted.