NEW DIAZA PENTADIENYLIUM SALTS (CYANINE DYES) DERIVED FROM N-SILYLATED PHOSPHINIMINES AND GUANIDINES

New synthetic methods for the preparation of pentadienylium cations (cyanine dyes) are developed in our laboratories. In particular the reaction of carboxonium derivatives on various primary and secondary amines is to be emphasized. This method is remarkably versatile to lead to new dyes hardly obtainable otherwise. It is applied here to the synthesis of previously unknown derivatives of N-silylated phosphinimines and guanidines where the conjugated polyenic system can be extended over the nitrogen atom on the phosphinimine or guanidine moiety. Spectrochemical results, mainly P-31, C-13 NMR and UV are in accordance with these assumptions opening thus a new field of investigation for the reactivity of the aza-Wittig compounds and more generally for the physical applications (ie in optical devices).