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Electrophilic and nucleophilic side chain fluorination of para-substituted acetophenones
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摘要
para-Substituted mg src="http://www.sciencedirect.com/scidirimg/entities/204e.gif" alt="greek small letter alpha" title="greek small letter alpha" border="0">-fluoroacetophenones have been synthesised by three different routes. Electrophilic fluorination of trimethylsilyl enol ethers of acetophenones using Selectfluor (F–TEDA–BF4, 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis-(tetrafluoroborate)) gave high to moderate yield depending on the electronic properties of the substituents. F–TEDA–BF4 mediated fluorination of acetophenones in methanol resulted in a mixture of mg src="http://www.sciencedirect.com/scidirimg/entities/204e.gif" alt="greek small letter alpha" title="greek small letter alpha" border="0">-fluoroacetophenones and the corresponding 2-fluoro-1,1-dimethyl acetals. The dimethyl acetals were hydrolysed using trifluoroacetic acid in water to maximise the yield of the product. Nucleophilic fluorination of mg src="http://www.sciencedirect.com/scidirimg/entities/204e.gif" alt="greek small letter alpha" title="greek small letter alpha" border="0">-bromoacetophenones using tetrabutylammonium hydrogen bifluoride (TBABF) led to moderate yield when having electron-donating substituents, whereas low yields were experienced when more electron-withdrawing substituents were introduced.

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