A mechanism for heteroatom scrambling in the synthesis of unsymmetrical chalcogenopyrylium trimethine dyes

Heteroatom scrambling occurs due to the formation of unsymmetrical tris(chalcogenopyramylmethylidene)methanes during the synthesis of unsymmetrical chalcogenopyrylium dyes. The complete chalcogenopyranyl ring is involved during heteroatom scrambling and Reverse aldol reaction with dyes has no significant influence on scrambling mechanism. Dyes have found various applications in optical recording, electrophotography and thermal dye transfer. The experimental procedure for the synthesis of unsymmetrical dyes and tris(chalcogenopyramylmethylidene)methanes is discussed.