Design, synthesis and antiviral activity of novel pyridazines

► A series of pyridazines were prepared and evaluated for their antiviral activity. ► Most of these compounds possess anti-HIV activity and anti-TMV activity. ► The rearranged compounds 35 and 39 exhibited higher HIV inhibitory effect. ► Compound 9 showed similar in vivo anti-TMV activity to commercial Ribavirin. ► An efficient approach to evolve novel multi-functional antiviral agents was described.