Tris(trifluoromethanesulfonato)indium

Introduction

Tris(trifluoromethanesulfonato)indium or indium(III) trif­late [In(OTf)₃] constitute one of the most important catalyst among the lanthanide triflates and indium based reagents. In recent years, indium(III) triflate has received increasing attention both as a reagent and catalyst for organic reactions. [1] It is a mild, selective, and water tolerant Lewis acid in several C-C and C-heteroatom bond forming reactions. In contrast to classical Lewis acids, which often are required in stoichiometric quantities, In(OTf)₃ readily promotes a range of reactions in catalytic quantities soluble both in organic solvents and aqueous media. In some cases the presence of water even improves their activity. Moreover, the solubility of this reagent in water means that they can be readily recovered unchanged from the aqueous phase of reaction mixtures on work up and subsequently reused, a very crucial point as far as green chemistry is concerned, for which it is gaining popularity and momentum in current research. This catalyst finds application in thioacetalization and transthioacetalization of carbonyl compounds, [12] acylation of alcohols and amines, [13] tetrahydropyranylation and depyranylation of alcohols, [14] regioselective ring opening of activated aziridines with arenes. [15]

Preparation: In(OTf)₃ is prepared from the corresponding oxide (In₂O₃) and triflic acid (TfOH) in water.² The water formed in the reaction is evaporated under reduced pressure after filtering the unreacted oxide. The resulting white powder is dried in vacuo.

References

• 1a Molander G. Chem. Rev.  1992,  92:  29 
• 1b Kagan HB. Nany JI. Tetrahedron  1986,  42:  6573 
• 2 Kobayashi S. Hachiya I. Araki M. Ishitani H. Tetrahedron Lett.  1993,  43:  3755 
• 3 Loh T.-P. Tan K.-T. Hu Q.-Y. Angew. Chem. Int. Ed.  2001,  40:  2921 
• 4 Loh T.-P. Hu Q.-Y. Tan K.-T. Cheng H.-S. Org. Lett.  2001,  3:  266 
• 5 Loh T.-P. Hu Q.-Y. Ma L.-T. J. Am. Chem. Soc.  2001,  123:  2450 
• 6 Loh T.-P. Feng L.-C. Yang J.-Y. Synthesis  2002,  937 
• 7 Muthuswamy S. Babu SA. Gunanathan C. Tetrahedron Lett.  2002,  43:  3133 
• 8 Prajapati D. Laskar DD. Sandhu JS. Tetrahedron Lett.  2000,  41:  8639 
• 9 Ali T. Chauhan KK. Frost CG. Tetrahedron Lett.  1999,  40:  5621 
• 10 Frost CG. Hartley JP. Griffin D. Synlett  2002,  1928 
• 11 Kazahaya K. Hamada N. Ito S. Sato T. Synlett  2002,  1536 
• 12 Muthusamy S. Babu SA. Gunanathan C. Tetrahedron  2002,  58:  7897 
• 13 Chauhan KK. Frost CG. Lore J. Waite D. Synlett  1999,  1743 
• 14 Mineno T. Tetrahedron Lett.  2002,  43:  7975 
• 15 Yadav JS. Reddy BVS. Rao RS. Veerendhar G. Nagaiah K. Tetrahedron Lett.  2001,  42:  8067