1. Lanthanide triflates are Lewis acid catalysts that are stable in water, allowing reactions to be carried out in aqueous solvents. 2. They are synthesized by reacting lanthanide oxides with aqueous triflic acid to form hydrated lanthanide triflates. 3. As water-tolerant Lewis acids, lanthanide triflates have been used to catalyze various carbon-carbon and carbon-heteroatom bond forming reactions like Friedel-Crafts alkylations, Mukaiyama aldol additions, and hydroxymethylation reactions.

1. ScandiumSyntheticApplications
Dr.Gurumeet C Wadhawa ,Assistant Professor, Department of Chemistry.
Rayat Shikshan sansthas Veer Wajekar ASC College,Phunde,Uran
3

2. Lanthanide triflates are triflate salts of the lanthanide family with many uses in organic
chemistry as Lewis acid catalysts. The catalysts act similarly to aluminium
chloride or ferric chloride, but are stable in water, which makes it possible to use water
as a solvent instead of organic solvents.
Lanthanide triflates consist of a lanthanide metal ion and three triflate ions.
The lanthanides, or rare earth metals, are the elements
from lanthanum to lutetium in the periodic table. Triflate is a contraction of
trifluoromethanesulfonate; its molecular formula is CF3SO3, and is commonly
designated ‘OTf’. Triflic acid is a ‘superacid’ so its conjugate base ions are very
stable. Lanthanide triflates are normally nonahydrates, mostly commonly
depicted as Ln(OTf)3·(H2O)9; however, in the solid state and in aqueous
solution, the waters are bound to the lanthanide and the triflates are
counteranions, so more accurately lanthanide triflate nonahydrate is written as
[Ln(H2O)9](OTf)3.[1] Anhydrous lanthanide triflates, Ln(OTf)3, are also easily
obtained as described below. The metal triflate complex is
strongly electrophilic, thus acts as a strong Lewis acid.

3. Lanthanide triflates are synthesized from lanthanide oxide and aqueous triflic acid. In a typical
preparation, a 1:1 (v/v) solution of trilfic acid in water is added to a slight stoichiometric excess of
lanthanide oxide. The mixture is stirred and heated at 100 °C for a few hours, and the excess
lanthanide oxide is filtered off. The excess oxide ensures all of the triflic acid is consumed. The
water is removed under reduced pressure (or simply boiled away) to leave a hydrated
lanthanide triflate, Ln(H2O)9(OTf)3.[2]
In simplified form the reaction is
Ln2O3 + 6HOTf → 2Ln(OTf)3 + 3H2O
Since the reaction takes place in aqueous solution, more accurately,
Ln2O3 + 6HOTf + 18H2O → 2[Ln(H2O)9](OTf)3 + 3H2O
Anhydrous lanthanide triflates can be produced by dehydrating their hydrated counterparts by
heating between 180 and 200 °C under reduced pressure for 48 hrs. This is a major advantage
of lanthanide triflates compared to lanthanide halides, whose anhydrous forms require more
tedious synthetic procedures because they cannot be obtained by dehydrating their hydrates
(because of oxyhalide formation).
[Ln(H2O)9](OTf)3 → Ln(OTf)3 + 9H2O (180-200 °C, ~10−2 - 10−4 torr, 48 hrs)

4. 1. Lewis acid catalysis[ed
2. Lewis acids are used to catalyse a wide variety of reactions.
3. The mechanism steps are:[c
4. Lewis acid forms a polar coordinate with a basic site on the reactant
(such as an O or N)
5. Its electrons are drawn towards the catalyst, thus activating the
reactant
6. The reactant is then able to be transformed by a substitution
reaction or addition reaction
7. The product dissociates and catalyst is regenerated

5. • the substitution of organic solvents by water reduces the amount of waste and the metals
are recoverable and hence reusable.
• Generally, the benefits of these catalysts include:[citation needed]
• Selective, often producing fewer by-products than standard methods
• Asymmetric catalysts: chiral forms can be highly diastereo- and enantio-selective
• Some reactions can use greener non-chlorinated reagents, and reduce the number of synthesis
steps
• Less toxic and not corrosive, so safer and easier to handle
• Mild reaction conditions are safer and reduce energy consumption.
t

6. The main disadvantages of these new catalysts compared with
conventional ones are less industrial experience, reduced
availability and increased purchase cost. As they contain rare
metals and sulfonate ions, the production of these catalysts may
itself be a polluting or hazardous process. For example, metal
extraction usually requires large quantities of sulfuric acid. Since
the catalyst is recoverable, these disadvantages would be less
over time, and the cost savings from reduced waste treatment
and better product separation may be substantially greater.
The toxicity of individual lanthanides vary. One vendor MSDS lists
safety considerations including dermal/eye/respiratory/GI burns
on contact. It also lists possible hazardous decomposition
products including CO, CO2, HF and SOx.[10] The compounds
are hygroscopic, so care is required for storage and handling.
However, these considerations also apply to the more common
catalysts.
These possible disadvantages are difficult to quantify, as
essentially all public domain publications on their use are by
research chemists, and do not include Life Cycle Analysis or
budgetary considerations. Future work in these areas would
greatly encourage their uptake by industry.

18. In 1993, Kobayashi et al. 23 first demonstrated the use of Sc(OTf)3 as a promising
Lewis acid catalyst in organic synthesis. Sc(OTf)3 is now commercially available and
can be prepared easily from scandium oxide (Sc2O3) and aqueous
trifluoromethanesulfonic acid (TfOH).7 In general, most of the traditional Lewis acids
are deactivated in the presence of water, but Sc(OTf)3 is stable in an aqueous
environment and can efficiently catalyze organic transformations in aqueous media.
Moreover, Sc(OTf)3 is well tolerated and worked efficiently as a Lewis acid catalyst in
several other organic solvents. As the size of the scandium (Sc3+) ion is smaller than
those of the rare-earth elements forming triflate salts, Sc(OTf)3 is a much more
efficient Lewis acid catalyst than its congeners. Because of all these benefits the use
of this unique catalyst has increased rapidly in organic synthesis especially in carbon-
carbon and carbon-heteroatom bond forming reactions.24 The present
communication focuses on the catalytic application of Sc(OTf)3 as a mild Lewis acid
in organic synthesis, leading to carbon-carbon and carbon-heteroatom bond forming
reactions, with up-to-date literature reported on this subject during the last decade.
The following Sections describe the catalytic applicability of scandium(III) triflate in
organic synthesis.

25. Carbon-Carbon Bond-forming Reactions 2.1 Friedel-Crafts alkylation of
aromatic compounds with alkenes Scandium(III) triflate catalyzed Friedel-
Crafts alkylation of aromatic compounds (1) with alkenes (2) to form the
corresponding alkylated products (3) was demonstrated by Song et al. 25
(Scheme 1) in 1,3- dialkylimidazolium salts as hydrophobic ionic liquid
solvents.

34. Organicchemistryin water Introduction
Organicreactionsin water
・
Advantage:safe,benign,environmentallyfriendly,and cheap
・
Disadvantage:Mostorganicsubstancesareinsolublein water
.
Manyreactivesubstrates,reagents,andcatalystsare decomposed
or deactivatedbywater
.
Me
AcO
+ N
O
O
AcO
N
O
O
Me
H
H
8h, r.t.
water
y. 81%
R1
+ R2I
Zn/CuI, cat. InCl
O OH
H R2
R1
Na2C2O4/H2O
R1 = CN, Br, Cl, H, CH3, CF3, CH2O, HO
R2 = alkyl
y. 14 - 85%
CN
cat. Ru(OH)x/Al2O3
water O
NH2
> 99%
Ru-catalyzed hydration of nitriles
to amides in water
4
Diels–Alder reaction in water
Rateaccelerationof Diels–Alderreactions
bywatersolvent.
Barbier–Grignard type
reaction in water
Chem.Soc.Rev
.,2006,35,68–82

35. Mukaiyamaaldol addition Introduction
R1
O
H
+
OTMS
R3
R2
1) Lewis acid
2) desilylation
R1
R2
OH O
R3
typicalLewisacids:TiCl4,SnCl4,BF3・
OEt3
TheMukaiyamaaldoladditionisatypeof aldolreaction
betweenasilylenoletherandanaldehydeor formate.
Thesereactantsallowfor acrossedaldolreaction
betweenanaldehydeandaketoneor adifferentaldehyde
withoutself-condensationof the aldehyde.
Lewisacidsundergohydrolysisbywatermolecules,
sostrictanhydrousconditionsareneededinthisreaction.
5
Aldoladditionisapowerfulmethodfor forming aC-C bond.

36. Useof Ln(OTf)3asLewisacid
H2O
LnO3 + 6CF3SO3H 2Ln(OTf)3 + 3H2O
Lanthanide triflate
aswater-tolerantLewisacids
Ln(OTf)3ispreparedfromthecorrespondinglanthanideoxides(Ln2O3)
andtrifluoromethanesulfonicacidinwater
.
Chem.Lett.,2187-2190(1991)
Inmost cases,
thereactionsproceededsmoothly
.
Yb(OTf)3isthemostreactivecatalyst.
of 1 withCommercialFormaldehydeSolutionatr
.t.
Hydroxymethylationreactionsbyusing Ln(OTf)3
Effectof LanthanideTriflatesintheReaction
Ph
OSiMe3
+ HCHO aq.
Ln(OTf)3
(x%)
H2O/THF(1/4)
r.t.
Ph
O
OH
7

37. Lanthanide triflate
aswater-tolerantLewisacids
Screeningof Ln(OTf)3
OSiMe3
+
O
H
O OH
H2O/THF(1/4)
r.t.
Effectof LanthanideTriflatesintheReaction
of 4withBenzaldehydeatr.t.for 20hinH2O-THF(1:4).
Ln(OTf)3
(10%)
Highreactivity:Nd-, Gd-, Yb-, Lu(OTf)3
Lowreactivity:La-,Pr-, Tm(OTf)3
9