An Efficient and Chemoselective Procedure for Acylal Synthesis
A novel heterogeneous efficient procedure has been developed for the chemoselective synthesis of acylals (1,1-diacetates) under solvent-free conditions. A novel catalyst prepared by the sulfuric acid catalyzed copolymerization of p-toluenesulfonic acid and paraformaldehyde displays extremely high activities for the title reactions, affording average yields over 90% within several minutes. A comparative study showed that the novel catalyst has much higher activity than other catalysts used for this purpose. Besides, the novel catalyst displays chemoselectivity for the protection of aldehydes in the presence of ketones. In addition the high acidity (4.0 mmol/g), thermal stability (200 ºC) and easy reusability make the novel catalyst one of the best choices for the process.
A Rapid and Convenient Synthesis of 1,1-Diacetates from Aldehydes and Acetic Anhydride Catalyzed by PVC-FeCl3 Catalyst
Abstract A variety of aldehydes can be converted into 1,1-diacetates rapidly and conveniently in the presence of catalytic amounts of poly(vinyl chloride) supported ferric chloride reagent at room temperature in excellent yields.
Copper perchlorate: Efficient acetylation catalyst under solvent free conditions
Abstract Acetylation of alcohols, phenols, amines, thiols and aldehydes is performed using acetic anhydride as acylating agent and M(ClO 4 ) 2 ·6H 2 O as catalyst where M is Mn, Co, Ni, Cu and Zn at room temperature under solvent free conditions. Transition metal perchlorates used here are found to be more efficient than the already reported metal triflates and s, p-block perchlorates. Substrates containing acid sensitive protecting groups are acylated successfully without any cleavage of the protection. Remarkably, less nucleophlic thiols (e.g. 2-mercaptobenzothiazole) are acylated with reasonable yields using transition metal perchlorates as catalyst whereas otherwise active acylation catalyst Mg(ClO 4 ) 2 was found to be inefficient.