Synthesis of new azonia derivatives of thia6]helicene ( 1 ) and thia7]helicene ( 2 ) is described. The Knoevenagel condensation of 2‐methylbenzothieno3,2‐a]quinolizinium salt ( 8 ) with appropriate arylaldehydes yielded 2‐(arylvinyl)benzothieno3,2‐a]quinolizinium salts ( 9 and 10 ), respectively. Photocyclization of 2‐styrylbenzothieno3,2‐a]quinolizinium salt ( 8 ) gave 7a‐azonia‐5‐thia6]helicene ( 1 ) in 63% yield. Similarly, 2‐2‐(2‐naphthyl)vinyl]benzothieno3,2‐a]quinolizinium salt ( 10 ) afforded 7a‐azonia‐5‐thia7]helicene ( 2 ) in 56% yield. The complete and unambiguous assignment of their 1H‐ and 13C‐nmr spectra was performed by utilizing two‐dimensional nmr spectroscopic methods.
