DABCO

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DABCO
Dabco-2.svg DABCO-3D-balls.png
Identifiers
CAS number 280-57-9 YesY
PubChem 9237
ChemSpider 8882 YesY
Jmol-3D images Image 1
Image 2
Properties
Molecular formula C6H12N2
Molar mass 112.17 g mol−1
Appearance White crystalline powder
Melting point 156 to 160 °C (313 to 320 °F; 429 to 433 K)
Boiling point 174 °C (345 °F; 447 K)
Solubility in water Soluble, hygroscopic
Acidity (pKa) 3.0, 8.8 (in water)[1]
Hazards[2]
GHS hazard statements H228, H302, H315, H319, H335, H412
GHS precautionary statements P210, P261, P273, P305 + P351 + P338
R-phrases R11, R22, R36/37/38, R52/53
S-phrases S26, S60
Main hazards Harmful
NFPA 704
Flammability code 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g., diesel fuel Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 62 °C (144 °F; 335 K)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

DABCO or 1,4-diazabicyclo[2.2.2]octane is a chemical compound and a registered trademark for Air Products' catalyst product line including 1,4-diazabicyclo[2.2.2]octane. It is a polyurethane catalyst, Baylis-Hillman reaction catalyst, complexing ligand, and Lewis base.[3] It is used to regulate the reaction rate in Flexplay time-limited DVDs by adjusting pH. Antioxidants, like DABCO, are used to improve the lifetime of dyes. This makes DABCO useful in dye lasers and in mounting samples for fluorescence microscopy (when used with glycerol and PBS).[4] DABCO can also be used to demethylate quaternary ammonium salts by heating in dimethylformamide (DMF).[5]

Although the first pKa is 8.8 that is almost the same as ordinary alkylamines, the nucleophilicity is high because the alkyl groups does not disturb the lone pairs.

DABCO has been used as a catalyst for a metal-free Sonogashira coupling, with or without microwave enhancement.[6] For example, phenylacetylene couples with electron-deficient iodoarenes to furnish the Sonogashira product in 77% yield with 95% selectivity.

Example of a DABCO-catalysed Sonogashira coupling

DABCO has also been used for Morita-Baylis-Hilman reaction.[7]

The scheme of Baylis Hilman reaction

References[edit]

  1. ^ D. H. Ripin, D. A. Evans (2002). "pKa's of Nitrogen Acids". 
  2. ^ "Safety data for 1,4-diazabicyclo[2.2.2]octane (see MSDS)". Sigma-Aldrich. 
  3. ^ Cecchi, L.; DeSarlo, F.; Machetti, F. (2006). "1,4-Diazabicyclo[2.2.2]octane (DABCO) as an Efficient Reagent for the Synthesis of Isoxazole Derivatives from Primary Nitro Compounds and Dipolarophiles: The Role of the Base". European Journal of Organic Chemistry 2006 (21): 4852–4860. doi:10.1002/ejoc.200600475. 
  4. ^ Valnes, K.; Brandtzaeg, P. (1985). "Retardation of immunofluorescence fading during microscopy" (pdf). Journal of Histochemistry and Cytochemistry 33 (8): 755–761. PMID 3926864. 
  5. ^ Ho, T. L. (1972). "Dealkylation of Quaternary Ammonium Salts with 1,4-Diazabicyclo[2.2.2]octane". Synthesis 1972 (12): 702. doi:10.1055/s-1972-21977. 
  6. ^ Luque, R.; Macquarrie, D. J. (2009). "Efficient solvent- and metal-free Sonogashira protocol catalysed by 1,4-diazabicyclo(2.2.2) octane (DABCO)". Organic and Biomolecular Chemistry 7 (8): 1627–1632. doi:10.1039/b821134p. PMID 19343249. 
  7. ^ Baylis, A. B.; Hillman, M. E. D. German Patent 2155113, 1972.