Cationic organotin clusters for highly efficient alcohol acetylation catalysts

The effectiveness of cationic species for increasing the catalytic activity of organotin Lewis acids has been assessed by comparing two types of cationic organotin clusters, [Bu2Sn(OH)-(H2O)](2)(2+)2OTf(-) and [(BuSn)(12)O-14(OH)(6)]Cl-2+(2)-.2H(2)O, with neutral clusters in alcohol acetylation. The Sn-2 dication is extremely active, with a catalyst concentration of 0.001 mol %, sufficient to give a quantitative yield. The Sn-12 dication is slightly less active but gives high levels of chemoselectivity and primary/secondary alcohols selection. The neutral clusters are less effective catalysts. A variety of synthetic applications are feasible by changing the Lewis acidity of the catalysts.