clear colorless to yellow liquid
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.
Squaric acid and its derivatives (Dibutyl squarate) are used in synthesis of pharmaceutical intermediates, squarylium dyes, and photoconducting squaraines.
ChEBI: A cyclic ketone and diether that is a dibutyl ether derivative of squaric acid.
3,4-Dibutoxy-3-cyclobutene-1,2-dione is the dialkyl ester of squaric acid.
General procedure for the synthesis of di-n-butyl squarate from squaric acid (1) (2.00 g, 17.54 mmol) and n-butanol: Squaric acid (1) was dissolved in n-butanol (50 mL) and the reaction was carried out under stirring conditions at reflux for 3 hours. After completion of the reaction, the mixture was cooled in an ice bath, followed by the addition of diethyl ether (Et2O, 50 mL). The mixture was washed sequentially with cold distilled water, cold saturated aqueous NaHCO3 solution and cold distilled water. The organic layer was separated and dried with anhydrous sodium sulfate. The solvent was removed by distillation under reduced pressure to give the brown oily product di-n-butyl squarate (2.92 g, 74% yield). The product was chromatographically pure and could be used in subsequent reactions without further purification.
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