Chhibber, Manmohan (2004) Potassium Fluoride on Alumina $(KF/Al_2O_3)$. In: Synlett (1). pp. 197-198.
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(A) Sawyer et al. have demonstrated the use of $KF/Al_2O_3$ and 18- Crown-6 to synthesize diaryl ethers, diarylthio ethers, and diaryl amines via $S_NAr$ type addition reaction of phenol, thiophenol, and aniline to 2-fluorobenzonitrile respectively. The optimization of the above reaction conditions led to the synthesis of compounds, which were unachievable using Ullman coupling. For example, electronically unfavorable 3-chloro benzonitrile can be condensed with 3-methylphenol to give corresponding diaryl ether in 66% yields using $KF/Al_2O_3,$ 18-Crown-6 in DMSO at 140 °C. (B) Glaser coupling reactions to generate diacetylenes using $KF/ Al_2O_3$ with $CuCl_2$ and solvent free conditions under microwave irradiation have been optimized by Kabalka et al. The use of two different alkynes, however gives a mixture of products. (C) Silveira et al. have reported the use of $KF/Al_2O_3$ for the synthesis of 3,4-dihydroisoquinolines and isoquinolines by desulfonylation of N-sulfonyltetrahydroisoquinone derivatives. Microwave irradiation (490 W) of the solid-state reaction mixture containing the substrate and base for 10–20 s gives 3,4-dihydroisoquinoline, which on increasing the time leads to the formation of corresponding isoquinoline. (D) $KF/Al_2O_3$ selectively desilylates the tert-butyldimethylsilyl protected phenol at room temperature. Acetonitrile as the solvent eliminates the need for an aqueous work up and the use of ultrasound accelerates the reaction thereby reducing reaction times. (E) Selective O-demethylation of arylalkyl ethers has also been accomplished using $KF/Al_2O_3$ and dry ethylene glycol in 3–5 h at 210–215 °C in moderate to high yields.
|Item Type:||Journal Article|
|Additional Information:||The copyright belongs to Thieme Stuttgart.|
|Department/Centre:||Division of Biological Sciences > Molecular Biophysics Unit
Division of Chemical Sciences > Organic Chemistry
|Date Deposited:||30 May 2006|
|Last Modified:||19 Sep 2010 04:27|
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