Squaramide

Squaramide
Names
	IUPAC name 3,4-diaminocyclobut-3-ene-1,2-dione
Identifiers
CAS Number	5231-89-0;
3D model (JSmol)	Interactive image;
PubChem CID	2781329;
CompTox Dashboard (EPA)	DTXSID40381784 ;
	InChI InChI=1S/C4H4N2O2/c5-1-2(6)4(8)3(1)7/h5-6H2 Key: WUACDRFRFTWMHE-UHFFFAOYSA-N;
	SMILES C1(=C(C(=O)C1=O)N)N;
Properties
Chemical formula	C4H4N2O2
Molar mass	112.088 g·mol−1
Appearance	white solid
Melting point	338–340 °C (640–644 °F; 611–613 K)
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
	Infobox references

Squaramide is the organic compound with the formula O₂C₄(NH₂)₂. Not an amide in the usual sense, it is a derivative of squaric acid wherein two OH centers are replaced by NH₂. Squaramides refer to a large class of derivatives wherein some of the H's are replaced by organic substituents. Exploiting their rigid planar structures, these compounds are of interest as hydrogen-bond donors in supramolecular chemistry and organocatalysis.[1] Squaramides exhibit 10-50x greater affinity for halides than do thioureas.[2]

Squaramide is prepared by ammonolysis of diesters of squaric acid:[3]

O₂C₄(OEt)₂ + 2 NH₃ → O₂C₄(NH₂)₂ + 2 EtOH

N-Substituted squaramides are prepared similarly, using amines in place of ammonia.

Chloride-squaramide interaction in O₂C₄(NH(C₆H₄CF₃)₂. The characteristic planarity of a squaramide is evident.[2]

References

Chauhan, P.; Mahajan, S.; Kaya, U.; Hack, D.; Enders, D. (2015). "Bifunctional Amine-Squaramides: Powerful Hydrogen-Bonding Organocatalysts for Asymmetric Domino/Cascade Reactions". Adv. Synth. Catal. 357: 253–281. doi:10.1002/adsc.201401003.CS1 maint: uses authors parameter (link)
Nathalie Busschaert, Isabelle L. Kirby, Sarah Young, Simon J. Coles, Peter N. Horton, Mark E. Light, Philip A. Gale. "Squaramides as Potent Transmembrane Anion Transporters". Angew. Chem. Int. Ed. 51: 4426–4430. doi:10.1002/anie.201200729.CS1 maint: uses authors parameter (link)
Storer, R. Ian (2013). "Squaramide". e-EROS Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rn01531.

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[1] Chauhan, P.; Mahajan, S.; Kaya, U.; Hack, D.; Enders, D. (2015). "Bifunctional Amine-Squaramides: Powerful Hydrogen-Bonding Organocatalysts for Asymmetric Domino/Cascade Reactions". Adv. Synth. Catal. 357: 253–281. doi:10.1002/adsc.201401003.CS1 maint: uses authors parameter (link)

[Busschaert-2] Nathalie Busschaert, Isabelle L. Kirby, Sarah Young, Simon J. Coles, Peter N. Horton, Mark E. Light, Philip A. Gale. "Squaramides as Potent Transmembrane Anion Transporters". Angew. Chem. Int. Ed. 51: 4426–4430. doi:10.1002/anie.201200729.CS1 maint: uses authors parameter (link)

[3] Storer, R. Ian (2013). "Squaramide". e-EROS Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rn01531.