Helical Dispiroindeno[2,1- c ]fluorenes Possessing Planar Chirality: Synthesis and Chiroptical Properties

Syntheses of enantioenriched helical dispiroindeno[2,1-c]fluorenes (DSIF) possessing one or two pCp moieties are presented. These are based on the conversion of (Sp)- and (Rp) pCp-carbaldehydes 1 to triynediols 2 and 6 that were converted to enantioenriched DSIFs 4 and 8 via a catalytic [2+2+2] cyclotrimerization, oxidation, and spirocyclization sequence. Photophysical properties were measured, and compounds 4 and 8 are highly fluorescent in the violet-blue light region with |glum| values in the order of 10⁻⁴ and 10⁻³, and BCPL values 1.1 and 7.6, respectively.