Silica-bonded S-sulfonic acid as a recyclable catalyst for chemoselective synthesis of 1,1-diacetates

Silica‐bonded S‐Sulfonic Acid: A Recyclable Catalyst for the Synthesis of Trisubstituted Imidazoles under Solvent‐free Conditions

“…Recently, we have reported the preparation of silica-bonded S-sulfonic acid (SBSSA) and its application as catalyst to the preparation of acylal, 5 quinoxaline, 6 and coumarin derivatives 7 (Scheme 1). In our continued interest in the development of a highly expedient methodology for the synthesis of fine chemicals and heterocyclic compounds of biological importance, [30][31][32][33][34][35] we report here the synthesis of trisubstituted imidazoles in the presence of SBSSA under solvent-free conditions (Scheme 2).…”

Silica immobilized sulfuric acid ([3-(propyl)sulfanyl]propyl]ester andN-propylsulfamic acid as recyclable catalysts for chemoselective synthesis of 1,1-diacetates

“…All the products are known compounds and were characterized by comparison of their IR, 1 H NMR, and 13 C NMR spectroscopic data and their melting points with reported values (10Á25). Silica immobilized sulfuric acid ([3-(propyl)sulfanyl]propyl]ester (I)) and silicabonded N-propylsulfamic acid (II) were prepared according to our previously reported procedures (51,52).…”

“…Other catalysts, such as iodine (36), N-bromosuccinimide (37), and trimethylchlorosilane/sodium iodide (38), have also been used for this transformation, but these procedures are often accompanied by longer reaction times, poor product yields, stringent conditions, good catalyst loading; require the use of toxic solvents; and so on. More recently, cobalt (II) bromide (39), SO 3 H-functionalized ionic liquids (40), ferrous methansulfonate (41), poly(N,N?-dibromo-N-ethylbenzene-1,3-disulfonamide) (42), NbCl 5 (43), SbCl 3 (44), silica-bonded S-sulfonic acid (45), and supported catalysts (46Á50) were reported for the synthesis of 1,1-diacetates.…”

Formylation and acetylation of alcohols using Amberlyst-15®as a recyclable heterogeneous catalyst

“…Formylation using ethyl formate offers numerous advantages such as simple work-up and easy accessibility of the reagent at relatively low rate. Common metal triflates generally used for this reaction are In(OTf) 3 (7), Ce(OTf) 4 (8), and Bi(III)salts (9 (12), TiCl 3 (OTf) (13), cerium polyoxometalate (14), silicabonded N-propyl sulfamic acid (15), and sulfuric acid ([3-(3-silicapropyl)sulfanyl] propyl)ester (16) are the various solid acid catalysts used for formylation with ethyl formate.…”