3,4-Dibutoxy-3-cyclobutene-1,2-dione was used in the synthesis of novel semisquarylium dye, useful for highly selective Hg2+ sensing in aqueous media. It was also employed in the synthesis of 3-butoxy-4-(1,3,3-trimethyl-2,3-dihydro-1H-2-indolylidenemethyl)-3-cyclobutene-1,2-dione, intermediate for the synthesis of squaryl dyes.
