Synthesis and Reactivity of a New Heptacarbon Chain Carboxonium Salt − Access to a New Class of Streptocyanine Dyes

A new highly reactive heptacarbon chain carboxonium salt 1 was synthesized. It leads, by action of various amines and hydrazone, to a new class of symmetrical heptacarbon chain streptocyanine dyes 2−6. A hemicarboxonium salt 7, which leads to a dissymmetrical streptocyanine, was also obtained. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)