The design and synthesis of 2,6-diphenylthiazolo[3,2-b][1,2,4]triazoles characterized by a large aromatic building block bearing cationic side chains are reported. These molecules are evaluated as telomeric G-quadruplex stabilizers and for their selectivity towards duplex DNA by competition experiments. Two compounds (14a, 19) were found active with high selectivity for telomeric G-quadruplex over duplex DNA.