Introduction
<P>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]
</P><P>Preparation: In(OTf)
3 is prepared from the corresponding
oxide (In
2O
3) 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.</P>
