Summary
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 the two OH groups are replaced by NH2 groups. 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] Squaramides also find application in medicinal chemistry, metabolomics and material science due to their ability to selectively conjugate amines[3][4]
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| IUPAC name
3,4-diaminocyclobut-3-ene-1,2-dione
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3D model (JSmol)
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PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |
| 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
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Squaramide is prepared by ammonolysis of diesters of squaric acid:[5][6]
- O2C4(OEt)2 + 2 NH3 → O2C4(NH2)2 + 2 EtOH
N-Substituted squaramides are prepared similarly, using amines in place of ammonia.
References edit
- ^ 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 (2–3): 253–281. doi:10.1002/adsc.201401003.
- ^ a b Nathalie Busschaert; Isabelle L. Kirby; Sarah Young; Simon J. Coles; Peter N. Horton; Mark E. Light; Philip A. Gale (2012). "Squaramides as Potent Transmembrane Anion Transporters". Angew. Chem. Int. Ed. 51 (18): 4426–4430. doi:10.1002/anie.201200729. PMID 22461434. S2CID 34164978.
- ^ Lin, Weifeng; Yang, Zhen; Kaur, Amanpreet; Block, Annika; Vujasinovic, Miroslav; Löhr, J.-Matthias; Globisch, Daniel (2021). "Squaric acid as a new chemoselective moiety for mass spectrometry-based metabolomics analysis of amines". RSC Chemical Biology. 2 (5): 1479–1483. doi:10.1039/D1CB00132A. ISSN 2633-0679. PMC 8496035. PMID 34704052.
- ^ Wurm, Frederik R.; Klok, Harm-Anton (2013). "Be squared: expanding the horizon of squaric acid-mediated conjugations". Chemical Society Reviews. 42 (21): 8220–8236. doi:10.1039/c3cs60153f. ISSN 0306-0012. PMID 23873344.
- ^ Storer, R. Ian (2013). "Squaramide". e-EROS Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rn01531. ISBN 978-0-471-93623-7.
- ^ Ian Storer, R.; Aciro, Caroline; Jones, Lyn H. (2011). "Squaramides: Physical properties, synthesis and applications". Chemical Society Reviews. 40 (5): 2330–2346. doi:10.1039/c0cs00200c. PMID 21399835.