A Lewis acid different from typical Lewis acids such as AlCl3, BF3, SnCl4, etc due to its stability in water.1 Has a good effect as a Lewis acid in Diels–Alder, allylation, Friedel–Crafts and Mukaiyama aldol reactions.2,3 Used as a recyclable catalyst for aromatic nitration with inorganic nitrates and acetic anhydride,4 for the direct acetylation of primary, secondary or tertiary alcohols with acetic acid,2 for chemoselective oxathioacetalization of aldehydes in the presence of ketones,5 for the acetylation of starch,6 for chemoselective thioacetalization,7 for catalyzing Strecker-type reactions of aldehydes, amines and tributyltin cyanide in both organic and aqueous solutions,8 for Coumarin synthesis,9 for synthesis of 1,5-benzodiazepine derivatives.10 Also employed in catalyzing the self-sufficient transimination reaction between various types of C=N bonds in organic solvents11 and deprotection of tert-butyl aryl sulfonamides.12
1. Eur. J. Org. Chem. 1999, 15.
2. Chem. Commun. 1997, 351.
3. J. Am. Chem. Soc. 2007, 129, 10029.
4. Chem. Pharm. Bull. 2002, 50, 1060.
5. Synthesis 2003, 2503
6. Carbohydr. Polym. 2008, 72, 439.
7. Tetrahedron Lett. 2002, 43, 1347.
8. Chem. Commun. 1998, 981.
9. Synth. Commun. 2008, 38