2-Diazoindoles: building blocks for the synthesis of antineoplastic agents

2-Diazoindoles were prepared by diazotization of the corresponding 2-aminoindoles followed by neutralisation. 2-Diazoindoles were utilised for the synthesis of 2-triazenoindoles, indolo[2,1-d][1,2,3,5]tetrazines and indolo[2,1-c][1,2,4]triazines. Most of these compounds exhibited in vitro antiproliferative activity.