Green Solvents. Ionic liquids in oxidation...

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Green Solvents.Ionic liquids in oxidation

catalysis.

Prof. Antonio Pastor

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Green chemistry?

Risk = f(hazard, exposure)

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Green Chemistry

Green chemistry consists of chemicalsand chemical processes designed toreduce or eliminate negativeenvironmental impacts.

From EPA (Environmental Protection Agency); USA.

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How can sustainability be achievedin the production of chemicals?

The Green chemical principles

Paul Anastas of the U.S. EnvironmentalProtection Agency (EPA)

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1. Waste preventioninstead of remediation

2. Atom economy orefficiency

3. Use of less hazardousand toxic chemicals

4. Safer products by design

5. Innocuous solvents andauxiliaries

6. Energy efficiency by design

7. Preferred use of renewableraw materials

8. Shorter syntheses (avoidderivatization)

9. Catalytic rather thanstoichiometric reagents

10.Design products to undergodegradation in theenvironment

11.Analytical methodologiesfor pollution prevention

12.Inherently safer processes

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ATOM ECONOMY

SUSTANAIBLEMETHODS

EFFICIENTPROCESSES

RECYCLABLE CATALYSTS

BENIGNSOLVENTS

BENIGN REAGENTS

ENERGY EFFICIENCY

MINIMUM CHEMICAL

WASTE

GREEN CHEMISTRY

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Green Chemistrymetrics

Environmental factor

Atom economy

The environmental quotient

The EcoScale

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E factor =Mass of wastes

Mass of the desired product

E factor =Mass of raw materials mass of product


Limitation: E factor does not account for any type of toxicity of the wastes

Environmental factor

%Atom economy = 100Formula weight of all atoms utilised

Sum of formula weight of all reactants used

Limitation: Qualitative. The yield has not been taken into account.

Atom economy

(Sheldon 1992)

(Trost 1991)

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The chlorohydrin process

Not utilisedUtilisedReactants

1456H,2O,Ca,2Cl442C,4H,O189Total2C,8H,3O,Ca,2Cl

72Ca,4H,2O0_____72Ca(OH)2

22H16O18H2O

712Cl0_____71Cl2

0_____282C,4H28C2H4

FormulaWeight

Not utilised atoms

FormulaWeight

Utilisedatoms

Formulaweight

Formula

E factor = (145/44) = 3.29 (poor)

% Atom economy = (44/189) X 100 = 23 %

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Catalytic synthesis of ethylene oxide

Not utilisedUtilisedReactants

0_____442C,4H,O44Total

2C,4H,1O

0_____16O161/2 O2

0_____282C,4H28C2H4

FormulaWeight

Not utilised atoms

FormulaWeight

Utilisedatoms

FormulaweightFormula

E factor = 0 (excellent)

% Atom economy = (44/44) X 100 = 100 %

catalyst

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E factor =Mass of wastes


Limitation: E factor does not take into account the nature and environmental impact of the generated waste.

The environmental quotient (EQ )

The environmental hazardous quotient (Q):

Q = 1 (NaCl)Q between 100-1000 (heavy metals on the basis of their toxicity)

In order to arrive at a more meaningful prediction, the E-factor is multiplied by Q. (EQ)

(Sheldon, 1994)

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The EcoScale

An ideal reaction (EcoScale = 100):

Compound A (substrate) undergoes a reaction with (or in the presence of) inexpensive compound(s) B to give the desired compound C in 100% yield at room temperature with a minimal risk for the operator and a minimal impact for the environment .

Van Aken et al, Beilstein Journal of Organic Chemistry 2006, 2:3

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Calculation of the EcoScale

An ideal reaction has the EcoScale value of 100. The EcoScale score for a particular preparation of the product in a high purity state (> 98%) is calculated by lowering the maximum value of 100 by any applicable penalty points.

EcoScale = 100 - sum of individual penalties.

Ranking of reaction conditions:Scores: > 75 , excellent; > 50 , acceptable; and < 50 , inadequate

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035

2.- Price (subjective)(price of reaction components to obtain 10 mmol of desired product)

Inexpensive (< $10)Expensive ($10 - $50)Very expensive (> $50)

1.- Yield2

(%)yield100-

Parameter Penalty points

15

555

101010

3.- Safety (basedon hazard warning

symbols)

N (noxious)T (toxic)F (flammable)E (explosive)F+T+

012345

4.Temperature/timeRoom temperature/ < 1hRoom temperature/ < 24hHeating / < 1hHeating / < 24 hCooling to 0CCooling below 0

16

01

2

3

113

5.- Technical setupCommon setupInstruments for controlled addition of chemicals(dropping funnel, syringe pump, gas pressure regulator )Unconventional activation technique(Microwave irradiation, ultrasound or photochemical activation )Pressure equipment (> 1 atm)(sc-CO2, high pressure equipment )Any additional special glassware(Inert) gas atmosphereGlove box

00000122333

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6.- Workup and purificationNoneCooling to room temperatureAdding solvent Simple filtrationRemoval of solvent with bp < 150 C Crystallization and filtrationRemoval of solvent with bp > 150 CSolid phase extractionDistillationSublimationLiquid-liquid extraction (if applicable, the process includes drying of solvent with desiccant and filtration of desiccant)Classical cromatography

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Example 1: reduction of nitrobenzene to aniline.

36Penalty points total

00030

6.- Filtration of the catalystRemoval of MeOHAddition of CHCl3Washing with NaCl(aq)Removal of CHCl3

05.- Room temperature, 1 h.

04.- Common glassware, stirring

10105

3.- Nitrobenzene (T,N)CH3OH (T,F)5% Pt/C (F)

32.- 5% Pt/C, 0,3 g

51.- Yield: 90 %NO2

CH3OH5% Pt/CHCOONH4rt, 1h

NH2

Synth Commun 2000, 30, 3639

Example 2: Oxidation of benzyl chloride to benzoic acid.

14.-Dropwise addition of H2O2

22Penalty points total

33001

6.- Extraction with AcOEt (3x10 mL)Washing with Na2S2O4(aq)Drying over MgSO4Removal of H2O2Crystallization from hexanes

35.- 90C, 10 h.

53.- Benzyl chloride (T)

0000

2.- H2O2(30 %, 36 mmol).Na2WO42H2O (66 mg, 0.2 mmol)[(octyl)3NMe]HSO4 (93 mg,0.2 mmol)Molecular sieves 4(100 mg)

61.- Yield: 87 %CH2Cl

30 % H2O2Na2WO4H2O[(CH3(CH2)7)3NCH3]HSO4MS 4A90C, 10 h.

COOH

J.Org.Chem 2001, 66, 3235

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Considering specific reactions, thedevelopment of green methods isfocused on two main aspects:

Choice of solvent.

The development of catalyzedreactions.

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Environmental friendly solvents

Water Supercritical CO2 (sc-CO2) Room-temperature ionic liquids (IL)

Choice of solvent

GREEN SOLVENTS

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Organic cationic component

Inorganic or organic anion

RNN

R

RN

R

RR

RP

R

R

RN

R

F

B

FF

F (F3C)O2S

N

SO2(CF3)O O

CF3

P

F

F

FF

F F

Cl- Br-

IONIC LIQUIDS

IONIC LIQUIDSa) Thermal stabilityb) Low vapor pressurec) Electric conductivityd) Interesting solvent propertiese) Non flammabilityf) High electroelasticityg) High heat capacityh) Liquid crystalline structuresi) Biphasic systems possibleSEPARATION

a) Gas separationsb) Extractive

distillationc) Extractiond) Membranes

SOLVENTSa) Organic reactions

and catalystb) Nanoparticle synthesisc) Polymerizationd) biocatalyst

LIQUID CRYSTALSdisplays

HEAT STORAGEThermal fluids

ELECTROELASTICMATERIALSa) Roboticsb) Artificial muscles

ELECTROLYTESa) Fuel cellsb) Batteriesc) Sensorsd) Coatinge) Metal finishing

LUBRICANTS ANDFUEL ADDITIVES

ANALYTICSa) GC-head-space

solventsb) MALDITOF

matricesc) Protein

crystallization

APPLICATIONS

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APPLICATIONS

GREEN SOLVENTS Alternative to VOCsnear-zero vapor pressure

TSILs (task-specific ionic liquids)Also reagent or catalyst in some reaction processes

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TSILs (task-specific ionic liquids)

Acidic ionic liquids

Basic ionic liquids

Ionic liquid containing metals

Chiral ionic liquids

NN

H3CCOOH BF4

-

RNN

R

OH-

NN

H3C

PF6-

NH2

RNN

R

Co(CO)4

N

CH2

H

NN R

X-

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PREPARATION (imidazolium ILs)

NNMe RX R

NNMe

X-KPF6

RNN

Me

PF6-

R= CH3CH2CH2CH2 [Bmim]PF6 or [C4mim]PF6 CH3(CH2)4CH2 [Hmim]PF6 or [C6mim]PF6 CH3(CH2)6CH2 [Omim]PF6 or [C8mim]PF6

X = Cl, Br

Tm = -75 Cd = 1,4 kg L -1

(25 C) = 300 mPasTd = 416 C

NN

PF6Some properties of [C 8mim]PF 6

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Influence of the alkyl chain in the melting point of 1-alkyl-3-methylimidazolium [PF 6]- ILs

Length of alkyl chain, R

Tem

pera

ture

(C

)

NNR

PF6-

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RNN

Me

Cl-NaOH

RNN

Me

OH-

NNMe BrCH2CH2NH2 NN

H3C

Br-NH2

BrCH2CH2OMe

NN

H3C

Br-OMe

TSILs (task-specific ionic liquids)

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(CH2)3CH3NN

Me

Cl-Na[Co(CO)4]

[C4mim]Cl

[C4mim][Co(CO)4]

[C4mim][Mn(CO)5], [C4mim][HFe(CO)4] are prepared.Also

Examples of organometallic ILs

Dyson et al. Chem.Commun., 2001, 1862

Br

O O

[C4mim][Co(CO)4]

5 M NaOH

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RNN

R

OH-HOOC NH2

R

RNN

R

-OOC NH2

R

Chiral ILs

Aminoacid as anion

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NH

COOH

a) LiAlH4b) Boc2O

N

CH2OH

Boc

a) TsClb) NaIm

N

CH2

Boc

NN

N

CH2

H

NN R

X-

a) HCl, NaHCO3b) NaX

N

CH2

Boc

NN R

Br-

RBr

Aminoacid as substituent

Chiral ionic liquids with aminoacidsHu et Al. Tetrahedron: Asymmetry 19 (2008) 1

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Silica supported IL

NN

H3C

Cl Si(OC2H5)3

NN

H3C

Si(OC2H5)3Cl-

NN

H3C

Si(OC2H5)3PF6

-

SiO2OHOH

SiO2OO

Si

N

N

H3C

OC2H5

PF6-

+

KPF6

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CHARACTERIZATION

[C4mim][(CF3SO2)2N]Me

NN

Bu

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Burrell et al. Green Chem., 2007, 9, 449

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Are ionic liquids green solvents?

Do they satisfy the principles of green chemistry?

Robin Rogers, director of the Centre for Green Manufacturing at the University of Alabama in Tuscaloosa.

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Deetlefs and Seddon. Green Chem., 2010, 12, 17

38Deetlefs and Seddon. Green Chem., 2010, 12, 17

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1. Waste prevention instead ofremediation

2. Atom economy or efficiency

3. Use of less hazardous andtoxic chemicals

4. Safer products by design

5. Innocuous solvents andauxiliaries

6. Energy efficiency by design

7. Preferred use of renewable rawmaterials

8. Shorter syntheses (avoidderivatization)

9. Catalytic rather thanstoichiometric reagents

10.Design products to undergodegradation in the environment

11.Analytical methodologies forpollution prevention

12.Inherently safer processes

Irrelevant principles to the laboratory-scale ionic liquid prep aration.Principles 8, 11 and 12 apply to all the ionic liquids synth esis exceptin the case of some TSILs.

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Principlesupheld

Atomeconomy

E-factorRoute

1,2,5,6,8,11,12HighPoor1(d)

5,6,8,11,12Low-highPoor1(c)

1,2,5,6,8,11,12HighExcellent1(b)

8, 11, 12HighGood1(a)

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5,6,8,11,12Low-mediumVery poor2(c)

5,6,8,11,12Low-mediumPoor2(b)

1,2,5,6,8,11,12Low-mediumPoor-good2(a)

Principlesupheld

Atomeconomy

E-factorRoute

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8,11,12Low-mediumPoor3

Principlesupheld

Atomeconomy

E-factorRoute

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Conclusions:

Laboratory-scale synthesis and purification of ILs can be considered as green if MW synthesis is employed.

Purification of hydrophobic ILs is greener than hydrophilic ILs.

It is necessary to develop improved purification process for hydrophilic ILs.

SYNTHESIS AND PURIFICATION OF ILs:

GREEN, BUT NOT GREEN ENOUGH


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!!" #$ %!& ()* "

()* + ,

, -

-

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./"0#$ %!1,2()* " ()* + 3

-.,

.

3,289Methanol

3,600Acetonitrile

2.90-6.93Ammonia

0.12-0.15Chlorine

356-620Benzene

29CHCl3

10-17Phenol

8.03-19.91Imidazolium ILs

LC50(mg/L)Compound

Bernot R.J. et al. Environmental Toxicology and Chemistry , 2005, 24, 87

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APPLICATIONS IN CATALYTIC OXIDATION and EPOXIDATION

BENIGN OXIDANTSH2O2, O2

MODEL REACTIONS Oxidation of sulfides Oxidation of alcohols Epoxidation of alkenes

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Oxidation of sulfidesTarget : removal of sulfur containing compounds in fuels.

More attractive solution:

Oxidative desulfurization (ODS).

BTs and DBTs can be oxidized to their corresponding sulfoxides and sulfoneseasily.

Classical in industry: Hydrodesulfurization

Problem: the HDS is limited in treating benzothiophenes (BTs) anddibenzothiophenes (DBTs).

RSR + H2cat.

R-R + H2S

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Oxidative desulfurization

S

[O], cat

SO O

Extraction with water orwater-soluble polar solvents (DMSO, DMF)

Problem : Use of flammable solvents, VOCs or wastewater emissions.

DBT

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Use of ILs

S

S

H2O2, cat.

SO O

Oil phase

IL phase

ILs are used as reaction media and as extractants

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Desulfurization of DBT using IL + Na 2MoO4 +

H2O2

78[C8mim]PF6

70[C4mim]PF6

68[C8mim]BF4

99[C4mim]BF4

Yield (%)Type of IL

T = 70C, t = 3 h, 5mol% catalyst

Khn et al. Coordination Chemistry Reviews, 255 (2011) 1518.

Desulfurization of DBT using

[C4mim]BF 4 + H2O2

99Na3PMo12O40

98(NH4)3PMo12O40

93H3PMo12O40

98(NH4)6Mo7O24

94H2MoO4

99Na2MoO4

Yield (%)Catalyst

T = 70C, t = 3 h, 5mol% catalyst

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Oxidative desulfurization of diesel fuel using ionic liquids.

Published in: Guangren Yu; Jingjing Zhao; Dandan Song; Charles Asumana; Xiaoyue Zhang; Xiaochun Chen; Ind. Eng. Chem. Res. 2011, 50, 11690-11697.DOI: 10.1021/ie200735pCopyright ' 2011 American Chemical Society

Chen et al. Ind. Eng. Chem. Res. 2011,50, 11690

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Lewis and Brnsted acidic ionic liquids used in thi s work.


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S-removal efficiency = X 100 (%)S0 - Sf

S0

S0 : the initial S-content.

Sf : the final S-content after oxidative removal.

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S-removal efficiency vs time for different ILs(model diesel fuel, 12 g; IL, 6 g; the initial S-content, 503 ppm; molar ratio of O/S, 16; temperature, 303 K), refer to previous slide for ILs numbering.


1

2

6

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Comparison between oxidative desulfurization (the data are extracted from the previous slide) and extractive desulfurization(model diesel fuel, 12 g; IL, 6 g; the initial S-content, 503 ppm; temperature, 303 K; time, 60 min).


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S-removal efficiency vs time at different temperatures for [C4mim]Cl/2 ZnCl2 (model diesel fuel, 12 g; IL, 6 g; the initial S-content, 503 ppm; molar ratio of O/S, 16).


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S-removal efficiency vs recycling time for [C4mim]Cl/2ZnCl2and [SO3HC 4mim]HSO4 (mass ratio of IL/oil, 1:2; molar ratio of O/S, 8:1; the initial S-content, 503 ppm; temperature/time, 363 K/1 h for [C4mim]Cl/2ZnCl2, 333 K/6 h for [SO3HC 4mim]HSO4).


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S-removal efficiency vs recycling time for [C4mim]Cl/2ZnCl2in the desulfurization of commercial diesel fuel (diesel fuel, 6 g; initial S-content, 64 ppm; IL, 3 g; 30 wt % H2O2, 0.136 g; temperature, 363 K; time, 1 h).


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Oxidation of alcohols

For classical and recent literature examples :http://www.organic-chemistry.org/synthesis/C2O/aldehydes/oxidationsalcohols.shtm

http://www.organic-chemistry.org/synthesis/C2O/ketones/oxidationsalcohols.shtm

http://www.organic-chemistry.org/synthesis/C2O/carboxylicacids/oxidationsalcohols.shtm

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Oxidation of 1-Napthol to 1,4-Naphthoquinone Using a Hydrogen Peroxide/Methyltrioxorhenium System in [C 4mim][BF 4]

Published in: Vasile I. Prvulescu; Christopher Har dacre; Chem. Rev. 2007, 107, 2615-2665.DOI: 10.1021/cr050948hCopyright ' 2007 American Chemical Society

CH3

ReO O

O

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IL catalyst for alcohol oxidation

OH

catalyst

30% aq H2O2 (dropwise addition)

[C4mim][BF 4] 90C, 1.5 h

O

96 %100 %1,5[C4mim] 4[W10O23]

31 %34 %2Na2MoO4

35 %40 %2Na2WO4

YieldConversiont (h)Catalyst

Oxidation of diphenyl carbinol

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Oxidation of benzylic alcohols

[C4mim] 4[W10O23] (cat)


[C4mim][BF 4] 90C, 1.5 h

OH

OH

OH

O

92 %

Diol oxidation

CH2OHR1

R2

R3

[C4mim] 4[W10O23] (cat)


[C4mim][BF 4] 90C, 1.5 h

CHOR1

R2

R3R1-R2 = OCH2O; R3 = H; 95 %R1=R3 = H; R2 = NO2; 92 %R1= H; R2 = R3 = OMe; 96 %

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3 [C4mim][Br] + 4 H2WO4 + H3PO4 + 8 H2O2

H2OCH2Cl2

[C4mim] 3[PO4(W(O)(O2)2)4] + 3 HBr + 12 H2O

n

OH

[C4mim]3[PO4(W(O)(O2)2)4] (0,05 eq.)


[C4mim][BF 4] 90Cn

O

n = 1, 4 h: 98 %; n= 3, 3 h: 96 %.

IL catalyst containing peroxide ligand

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Olefin epoxidation

O

HOOCl

MCPBA

Classical:

http://www.organic-chemistry.org/synthesis/C1O/epoxides2.shtmFor classical examples :

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UHP : urea-hydrogen peroxide adduct

Epoxidation in ILs

Abu-Omar et al. Chem.Commun., 2000, 1165

R = H, Me, Ph. Conversion and yield > 95 %

Ph MeReO3 (0.02 eq)H2O2 (30 %) (2 eq)

[C2mim][BF4], 8h, rt.

R

OConversion > 95 %Yield < 5 %

R MeReO3 (0.02 eq)UHP (2 eq)

[C2mim][BF4], 8h, rt.

R

O

67Polyhedron2009, 28, 3929.

With molybdenum compound as catalyst.

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MoO(O2)2(4-MepyO) 2

[MoO(O2)2(H2O)n] MoO(O2)2(4-MepyO)2

MoO3 + H2O2 (excess)

4-MepyO

NO CH3

69Chem. Commun.2010, 46, 5933.

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Reaction profile of the oxobisperoxomolybdenumcatalysed epoxidation of cis-cyclooctene

J. Mol. Catal. A2011, 338, 111.

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RecyclabilityAdvantages of RTILs:

Epoxide+

[Mo]+IL

Extraction [Mo]+IL

Epoxide

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Epoxide yield for ten catalytic cycles after 4 h reaction time in C8mim-PF6 as solvent in the presence of [Mo(O)(O2)2(H2O)n]/dmpz (dmpz = 3,5-dimethylpyrazole) with added dmpz after each cycle (red) or without (yellow).

1 2 3 4 5 67

89

10

0

20

40

60

80

100

Yie

ld (

%)

Catalytic Cycle

dmpz added

Dalton Trans.2011, 40, 5210 .

NH

N

CH3

H3C

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Wacker Oxidation of Styrene to Acetophenone


Other oxidations

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Direct Catalytic Oxidation of Cyclohexene to Adipic Acid


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For a review of catalyst in ILs:

V. I. Prvulescu, C. Hardacre, Chem. Rev. ,2007,107,2631

For a review of the use of ILs as solvents for catalyzedoxidations in organic synthesis:J.Muzart Adv.Synth. Catal. 2006, 348, 275

For a recent review of applications of ILs in catalytic oxid ationreactions:Qu et al. Adv.Mat.Res., 2011, 233, 499Khn et al. Cordination Chemistry Reviews, 2011, 255, 1518

For a review of selective chemical reactions in supercritic alcarbon dioxide, water and ionic liquids:

R Skouta, Green Chemistry Letters and Reviews, 2009, 2:3, 121

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