A new hetero[7]helicene 1(NN) structured by a diazabenzodiheterole (pyrroloindole) ring core was successfully synthesized by catalytic domino cyclodehydrogenation with Pd(OAc)(2) and O-2 as the key step. Significantly, 1(NN) was stereochemically stable at room temperature and could be subjected to optical resolution by chiral HPLC. Furthermore, kinetic analysis of 1(NN) and DFT calculations on its variants revealed that the stereochemical stability of the benzodiheterole-based helicenes was highly dependent on not only the heteroaromatic ring component but also on the N-substituent of the pyrrole ring unit.