ChemInform Abstract: SYNTHESE VON CYCLOALKA(B)4H‐PYRANEN

Abstract

Bei der Umsetzung der Äthoxycycloalkadihydropyrane (I) bzw. (IV) mit Polyphosphorsäure (PPA) oder p‐Toluolsulfonsäure (Tos) tritt Desalkoxylierung unter Bildung der 4H‐Pyransysteme (II) bzw. (V) ein.

Microwave rehydrated Mg–Al-LDH as base catalyst for the acetalization of glycerol

“…[2][3][4][5][6] These cyclic acetals are used as precursors for the production of green platform compounds 1,3-propanediol and 1,3dihydroxyacetone. 7 Acetalization of glycerol has been studied with various acid catalytic systems like H 2 SO 4 , AlCl 3 , FeCl 3 , ZnCl 2 , p-TSA and HCl [8][9][10][11] in a homogenous medium. Anchored silicotungstates on MCM-41, K10, supported metal oxides, heteropolyacids, zeolites, montmorillonite, Amberlyst-15, mesoporous MoO 3 /SiO 2 , SBA-15, sulfated zirconia, Zr-SBA-16, ion exchange resins, nanocrystalline SnO 2 -based solid acids, aluminium triflate grafted MCM-41, organo iridium derivatives, Hf-TUD-1, Zr-TUD-1, Sn-MCM-41, USY-2, Mo and W-promoted SnO 2 , mesoporous cellular foams (MCFs) modified by niobium or tantalum, acidic ionic liquids, TiO 2 -SiO 2 mixed oxides and Ni-Zr supported on mesoporous activated carbon have been used as heterogeneous catalysts.…”

Room temperature acetalization of glycerol to cyclic acetals over anchored silicotungstates under solvent free conditions

“…5 However, the effluent clearance leads to environmental snags and economical dilemmas. These hitches can be overcome by using heterogeneous catalysts such as alumina, 13 aluminosilicates, 14 resins, 15 transition metal complexes, [16][17][18] and mixed metal oxides. 5,19,20 Even though acid catalysis by supported HPAs has been greatly expanded from the viewpoint of their variety of structures and compositions, according to our knowledge, there is only one report on acetalization of glycerol by using heteropoly acids (HPAs).…”

Design of a solid catalyst for the synthesis of a molecule with blossom orange scent

“…4 The most general method for the synthesis of acetals is to react carbonyl compounds with an alcohol or an orthoester in the presence of acid catalysts. A number of acetalization procedures include the use of protic acids, Lewis acids (zinc chloride) 5 alumina, 6 montmorillonite, 7 zeolites 8 and mesoporous aluminosilicates. 9 Acetalization of aldehydes can be performed in the presence of weak acids, while ketones generally need stronger ones like sulfuric, hydrochloric or ptoluenesulfonic acid and larger amounts of catalyst than aldehydes.…”