Dibutyl squarate

Chemical Properties

clear colorless to yellow liquid

Uses

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.

Uses

Squaric acid and its derivatives (Dibutyl squarate) are used in synthesis of pharmaceutical intermediates, squarylium dyes, and photoconducting squaraines.

Definition

ChEBI: A cyclic ketone and diether that is a dibutyl ether derivative of squaric acid.

General Description

3,4-Dibutoxy-3-cyclobutene-1,2-dione is the dialkyl ester of squaric acid.

Synthesis

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.

References

[1] Canadian Journal of Chemistry, 1986, vol. 64, p. 2267 - 2273
[2] Bulletin de la Societe Chimique de France, 1990, # 3, p. 367 - 374
[3] Bioorganic and Medicinal Chemistry, 2017, vol. 25, # 14, p. 3803 - 3814
[4] Journal of Molecular Structure, 2009, vol. 936, # 1-3, p. 239 - 249
[5] Comptes Rendus Chimie, 2012, vol. 15, # 5, p. 454 - 462