In the present work, we presented an efficient synthesis and anticancer activity evaluation of some new 3-R-6-(5-arylfuran-2-yl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles. We have shown that the proposed synthetic protocols provided the possibility to design triazolothiadiazoles diversity with a considerable chemical novelty. The structures of target substances were confirmed by using 1H NMR spectroscopy, mass spectrometry and elemental analysis. The synthesized compounds were selected by the National Cancer Institute Developmental Therapeutic Program for the in vitro cell line screening. Among all the substances tested, three compounds exhibited significant cytotoxic activity.

Reaction of methyl 2-aryl-5-(chlorosulfonyl)-1,3-oxazole-4-carboxylates with 1H-pyrazol-5-amines and 1H-1,2,4-triazol-5-amines proceeds with the participation of endocyclic aminoazole nitrogen atoms to yield products containing a primary amino group. Being treated by sodium hydride these products undergo a further transformation into the tricyclic compounds. It has been shown that the cyclocondensation pathway includes the Smiles rearrangement with extrusion of SO2 followed by the elimination of MeOH. This reaction sequence is a convenient approach to the synthesis of new annulated [1,3]oxazolo[5,4-d]pyrimidine derivatives.