Synthesis and nitration of some thieno‐fused analogues of the benzo[a]quinolizinium cation

Abstract

AbstractThree thieno‐fused analogues of benzo[a]quinolizinium (1), thieno[3,2‐a]‐ and thieno[2,3‐a]quinolizinium 4 and 5 and thiazolo[2,3‐a]isoquinolinium (6), were synthesized by photocyclization of 1‐(2‐thienylvinyl)pyridinium salts 9a and 9b and 3‐styrylthiazolium salt 9c, respectively. The nitration of the compounds 4, 5, and 6 occurred predominantly at positions 2, 3, and 7, respectively, while the nitro group was introduced into the 8‐ and 10‐positions of 1 in the ratio of 68:32. The nmr and uv spectral properties and reduction potentials of 4–6 were also compared with those of the parent compound 1.