Hydroarylation of 1-aryl-2-halogeno-3,3,3-trifluoropropenes in CF3SO3H: Regioselective approach to trifluoromethylated diarylethanes and ethenesстатья
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Дата последнего поиска статьи во внешних источниках: 30 марта 2016 г.
Аннотация:The reaction of 2-halogeno-2-CF3 substituted styrenes [ArCH=C(X)CF3, X = F, Cl, Br] with the superacid TfOH resulted in 100% regioselective formation of the corresponding benzyl cations [ArHC+–CH(X)CF3]. Subsequent reaction of these electrophilic species with arenes [Ar’H] afforded diastereomeric 1,1-diaryl-2-halogeno-3,3,3-trifluoro propanes [Ar(Ar’)CH–CH(X)CF3] in high yields (up to 96%). The obtained halogenopropanes were easily transformed to the corresponding trifluoromethylated diarylethenes [Ar(Ar’)C=CCF3] in yields of up to 95% by dehydrohalogenation using base. The elimination of chlorides and bromides using the KOH-ethanol system proceeds via an E2 elimination, whereas in the case of fluorides an E1cb elimination most probably takes place as the major reaction path.