A new method was developed for the construction of tetra- and pentacyclic fused systems based on sigma(H)-adducts of 6-nitro-1,2,4-triazolo[1,5-a]pyrimidine with pi-excessive heteroaromatic compounds. The method involves the reduction of the nitro group accompanied by the aromatization of the dihydropyrimidine ring and followed by the cyclocondensation of the amino derivative with aldehydes