Ammonium Salts Catalyzed Acetalization Reactions in Green Ethereal Solvents

Ugo Azzena, Massimo Carraro, Martina Corrias, Rosella Crisafulli, Lidia De Luca, Silvia Gaspa, Luca Nuvoli, Salvatore Pintus, Luisa Pisano, Riccardo Polese, Michela Sanna, Giuseppe Satta (+3 others)
2020 Catalysts  
Cyclopentyl methyl ether and 2-methyltetrahydrofuran, low impact ethereal solvents forming a positive azeotrope with water, were successfully employed as solvents in the synthesis of a variety of acetals carried out under Dean–Stark conditions in the presence of heterogeneous acidic catalysts. Under these conditions, ammonium salts, either as such or supported on SiO2, performed better or equally well than widely employed homogeneous and heterogeneous acidic catalysts such as p-toluenesulfonic
more » ... cid, Amberlyst 15®, or Montmorillonite K10. Several examples highlight the advantage of tuning the relative acidities of ammonium salts by appropriately selecting the counterion. Within one of these examples, our protocol clearly outweighs the classic p-toluenesulfonic acid/toluene protocol in terms of chemoselectivity. Silica-supported catalysts were characterized by SEM, TEM, and FTIR spectroscopies, as well as by N2 physisorption. Such a characterization reveals an even distribution of ammonium salts on silica, thus confirming the formation of expected catalytic supports.
doi:10.3390/catal10101108 fatcat:22uoi2sqcfei7bby2pucqpcjii