Efficient synthesis of di- and trisubstituted 2-aryloxazoles via ytterbium(III) triflate catalyzed cyclization of tertiary propargylic alcohols with aryl amides
作者:Xiaoxiang Zhang、Wan Teng Teo、Philip Wai Hong Chan
DOI:10.1016/j.jorganchem.2010.09.059
日期:2011.1
based on Yb(OTf)3 catalyzed cyclization of trisubstituted propargylic alcohols with aryl amides is described. The reaction was accomplished in moderate to excellent product yields and with complete regioselective control. The mechanism is suggested to involve activation of the starting alcohol by the metal catalyst that results in its ionization. Subsequent cyclization of this newly generated carbocationic
Beyond Acid Strength in Zeolites: Soft Framework Counteranions for Stabilization of Carbocations on Zeolites and Its Implication in Organic Synthesis
作者:Jose R. Cabrero-Antonino、Antonio Leyva-Pérez、Avelino Corma
DOI:10.1002/anie.201500864
日期:2015.5.4
The generation of a carbocation with an acid depends not only on the acidstrength but also on the ability of the counteranion to stabilize the positive charge left behind. Here we report that despite their relatively weak acidity, zeolites are able to generate and stabilize medium‐size (molecular weight ≈300 Da) delocalized carbocations on their surface under mild reaction conditions, as it can be