Synthesis of tetracarbocyanines by the scission of the pyrylium ring of benzopyrylocyanines

It has been shown that the reaction of monomethinecyanines containing 4-benzopyrylium residues with quaternary salts of derivatives of 2-(1, 5, 5-trimethylcyclohex-1-en-3-ylidene)-methyl]benzothiazole leads to the scission of the pyrylium ring and the addition of the quaternary salt to the position of scission. The reaction gives tetracarbocyanines containing an o-hydroxyphenyl or an o-acetoxyphenyl substituent in the polymethine chain in addition to a hydrocarbon ring.