Access to Chiral Rigid Hemicyanine Fluorophores from Tröger Bases and α-Imino Carbenes.

Chiral hemicyanine fluorophores are afforded in three steps only from Tröger bases via α-imino carbene additions, an original aminal deprotection and Cu(II)-mediated oxidation. The stable benzodiazepinoindolium salts are readily isolated and present (chir)optical properties that can be fine-tuned by late-stage cross-coupling functionalization. The hemicyanine character of dyes was rationalized using first principles.