Pyrene-Fused [7]Helicenes Connected Via Hexagonal and Heptagonal Rings: Stereospecific Synthesis and Chiroptical Properties.

In this manuscript, we portrayed a stereospecific synthesis of - and -symmetric pyrene-fused [7]helicene compounds and , respectively. Compounds and were synthesized via a one-pot Suzuki coupling-C-H activation and two-step Suzuki coupling-Scholl reaction, respectively, with complete retention of configuration. The synthesized molecules differ in the fusing mode of [7]helicene units with pyrene via six- and seven-membered rings for and , respectively. There was a significant difference in the functional properties and enantiomerization barrier of both compounds because of their distinct molecular symmetry as well as fusing mode to pyrene moiety. The heptagon-containing molecule showed remarkable photophysical and chiroptical properties with commendable configurational stability compared to and pristine [7]helicene as well as its [5]helicene congener.