B(C6F5)(3)-mediated direct C7-alkenylation of N-propargylindoles without directing groups was developed. This reaction proceeds via the & pi;-activation of the alkynyl group with B(C6F5)(3)/Friedel-Crafts alkenylation/proton transfer reaction sequence. Interestingly, C7-alkenylation products could further convert into the fused indoles by deprotonation and finally polyaromatic N-heterocycles by the hydride abstraction.