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34.6.1.3.2 Method 2: Cycloadditions to Vinylic Fluorides

DOI: 10.1055/sos-SD-034-00199

Sai Krishna Murthy, A.; Tardivel, R.; Grée, R.Science of Synthesis, (200534315.

There are very few examples (excluding cyclopropanation reactions) that describe the synthesis of benzylic fluorides using cycloaddition reactions. α-Fluorostyrenes 90 have very low reactivity in DielsAlder reactions, undergoing addition only to 1,3-diphenylbenzo[c]furan (89), to give the benzyl fluoride derivatives 91A and 91B. The endo/exo ratio is about 60:40 and therefore decreased in all cases as compared to the parent alkenes. Both electron-donating and electron-withdrawing substituents in the aromatic ring of the α-fluorostyrenes accelerate the reaction rate, suggesting that a neutral DielsAlder reaction is taking place (Scheme 25).[‌52‌]

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