Brønsted Acid Catalyzed Cyclization of Propargylic Alcohols with Thioamides. Facile Synthesis of Di- and Trisubstituted Thiazoles
作者:Xiaoxiang Zhang、Wan Teng Teo、Sally、Philip Wai Hong Chan
DOI:10.1021/jo101292r
日期:2010.9.17
A general and efficient method to prepare 2,4-di- and trisubstituted thiazoles via p-TsOH center dot H2O-catalyzed cyclization of trisubstituted propargylic alcohols with thioamides is described. The reaction was accomplished in moderate to excellent product yields under mild conditions that did not require the exclusion of air and moisture and offers an operationally simplistic and convenient route to this synthetically useful aromatic heterocycle.
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