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4 1H,1H,2H,2H-Perfluorooctyl 1,3-dimethylbutyl ether (F-626)

4 1H,1H,2H,2H-Perfluorooctyl 1,3-dimethylbutyl ether (F-626)

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146



H. Matsubara and I. Ryu

CHO



CH2OH



2 mmol



LiAlH4 (1.1 equiv)



solvent



yield



solvent (1 mL), 35 °C, 5 h



F-626

ether



93 %

96 %



H2 (1 atom), 5 % Pd / C (3 mg)



C10H21

2 mmol



solvent (3 mL), r.t., 3 h



C10H21



solvent



yield



F-626

ether



98 %

95 %



Scheme 14



CHO



CH3



Cl



+ N H •H O

2 4

2

1mL



+



KOH

2.0 equiv



110 °C, 2 h, then 200 °C, 6 h



solvent



yield



solvent (2 mL)



F-626

diethylene glycol



89 %

89 %



solvent



yield



F-626

o-dichlorobenzene



83 %

60 %



Cl



Cl



Cl



2.5 mmol

OMe



OMe



OMe



+ HCONMePh + POCl3

1.3 equiv

1.3 equiv



100 °C, 1 h



OHC



solvent (1 mL)

OMe



1.0 mmol

OMe

COOMe

+

Me3SiO



MeOOC



COOMe

1.0 equiv



1.3 mmol



160 °C, 1 h

F-626 (3 mL)



HO



COOMe

83 %



Scheme 15



as an easily removed and reusable solvent for the Vilsmeier formylation, the

Wolff–Kishner reduction, and the Diels–Alder reaction (Scheme 15) [6].

The thermal retro-aldol reaction is a well known reaction and can be frequently

used for the preparation of some natural product analogs and for structure confirmation. F-626 was demonstrated to be an excellent reaction medium for the thermal

retro-aldol reaction, which is easily separable from the products by fluorous/organic

biphasic treatment. In the following example (Scheme 16) [35], the result without

solvent gave a 3/1 mixture of the desired retro-aldol and undesired dehydration

products while the use of ionic liquid [Bmim]NTf2 as a solvent gave an even worse

result for retro-aldol reaction, indeed a 50/50 mixture of desired and undesired

products. F-626 worked quite well for the selective thermal retro-aldol reaction.

The procedure including workup is detailed in Scheme 17. While fluorous ether

solvent F-626 does not dissolve the starting aldol at room temperature, upon heating

one layer results. After cooling, biphase workup using acetonitrile and FC-72,

followed by purification using silica gel chromatography, gave the desired ketone

in 94% yield with a ratio of 95/5 while F-626 was recovered in 98%.



Fluorous Organic Hybrid Solvents for Non-Fluorous Organic Synthesis

O



O

OH



147

O



200 °C, 4 h



+

20a



0.5 mmol



20b

yield (20a / 20b ratio)



solvent



47 % (75 : 25)

65 % (50 : 50)

98 % (95 : 5)



neat

[Bmim]NTf2 (0.5 mL)

F-626 (4 mL)



Scheme 16



O

OH

F-626



200 °C

O

CH3CN



CH3CN



FC-72



CH3CN



SiO2



F-626

FC-72

homogeneous



94 %



F-626

F-626

98 % recovery



Scheme 17



1.5



Methyl Perfluorobutyl Ether (Novec 7100)



The fluorous organic hybrid ether solvents Novec 7100 6 (isomeric mixtures of

methyl perfluorobutyl ether, C4F9OCH3) and Novec 7200 7 (isomeric mixtures of

ethyl perfluorobutyl ether, C4F9OC2H5) are commercially available from 3M Ltd.

Novec-7100 was successfully used as a co-solvent for electrophilic fluorination of

aryl Grignard reagents with N-fluoro-2,4,6-trimethylpyridinium tetrafluoroborate

(19) (Scheme 18) [36].



1.6



Perfluorotriethylamine



Perfluorotriethylamine (PF-TEA, 8) was used as the solvent for some Lewis acid

induced reactions such as the Hosomi–Sakurai and the Friedel–Crafts reactions



148



H. Matsubara and I. Ryu



BF4–



MgBr • LiCl +



MeO



N+

F



0.5 mmol



BF4–

N+

F



MeO



19

1.5 equiv



MgBr • LiCl +

0.5 mmol



0 °C, 1.5 h



F



THF (0.5 mL), Novec 7100 (2 mL)

79 %



0 °C, 1.5 h



F



THF (0.5 mL), Novec 7100 (2 mL)



19

1.5 equiv



62 %



Scheme 18

O

H



OH



TiCl4 (1.0 equiv)



+



SiMe3



2 mmol



1.0 equiv



solvent (4 mL)

-78 °C, then r.t, 15 min

solvent



yield



PF-TEA



90 %

92 % (second run)

92 %



CH2Cl2



O

AlCl3 (1.0 equiv)



O

+

5 mmol



Cl

1.0 equiv



89 %

Ph



OCH3



OCH3

+



4 mmol



PF-TEA (3 mL)

r.t, overnight



Ph



OCH3



1.2 equiv



Sc(OTf)3 (20 mol %)

PF-TEA

r.t, overnight



H3CO

57 %

40 % (second run)



OCH3



Scheme 19



(Scheme 19) [37, 38]. Interestingly, despite the existence of an amine structure, PFTEA does not react with Lewis acids. After the reaction, PF-TEA can be recovered

by triphasic (organic/aqueous/fluorous) workup and reused.



1.7



N-(1H,1H,2H,2H,3H,3H-Perfluorononanyl)-N-methyl

formamide (F-DMF)



Fluorous DMF, (N-(1H,1H,2H,2H,3H,3H-perfluorononanyl)-N-methyl formamide)

(9), is a colorless, slightly viscous liquid with a boiling point of 110  C at 0.75 Torr,

and a density of 1.544 g/cm [3] (25  C). F-DMF does not freeze at À35  C but

transforms to a glassy state at À40  C. F-DMF is miscible with a wide range of

organic solvents, such as hexane, benzene, chloroform, ether, acetone, ethyl acetate, and ethanol; however, it is hardly soluble in cyclohexane and water.



Fluorous Organic Hybrid Solvents for Non-Fluorous Organic Synthesis



O



I

+

1.0 mmol



OBu

1.2 equiv



O



Pd(OAc)2 (2 mol %)

PPh3 (2 mol %)

Pr3N (1.5 equiv)

F-DMF (0.5 mL)

120 °C, 2 h



OBu



87 %



Pd(OAc)2 (2 mol %)

PPh3 (4 mol %)

CuI (2 mol %)



I

+

1.0 mmol



149



1.2 equiv



i-Pr2NH (2.2 equiv)

F-DMF (0.5 mL)

80 °C, 2 h



83 %



Scheme 20



The approximate partition coefficients of F-DMF are listed in Table 4. For biphasic

separation a combination of cyclohexane and FC-72 is recommended.

F-DMF was tested for the Mizoroki–Heck and the Sonogashira reactions

(Scheme 20) [39]. These cross-coupling reactions proceeded smoothly to give the

products in good yields. Recycling and reusing of catalyst was achieved by organic/

fluorous biphasic workup in these reactions.



2 Conclusions

BTF has been used in synthetic chemistry not only as an alternative of harmful

chlorine-containing solvents but also as an option on optimizing reaction

conditions, often providing superior results in yields or selectivity to classical

organic solvents. Apart from BTF, the use of other newcomer fluorous hybrid

solvents has just started. However hydrofluorocarbons such as Solkane and Vertrel

appear promising as a green substitute for toxic chlorohydrocarbons. Fluorous ether

solvents, such as F-626 and Novec, exhibit more fluorous character than BTF.

Nevertheless, they can be employed for a variety of organic syntheses thus far

carried out with organic solvents. Advantage of hybrid solvents having strong

fluorous character is its ease of recovery by fluorous/organic biphasic workup or

fluorous solid phase extraction (F-SPE). F-DMF is unique since, unlike DMF, it is

not miscible with water, while the high polarity is retained. Needless to say, finding

the most suitable solvent to give highest conversion and selectivity is essential and

in this regard we still need a repertoire in designed solvents. For this purpose, it

should be noted that Chu, Yu, and Curran extensively investigated solvent polarity

and fluorophilicity/phobicity [40], which is quite useful for the design of fluorous/

organic biphasic systems with mixed hydrofluoroethers (HFEs, RfOR). This information is also useful for the design of blend solvents for synthetic chemistry.

Having diversity in solvents, organic synthesis would be more extensive, and the

role of fluorous hybrid solvents should be quite large.



150



H. Matsubara and I. Ryu



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Top Curr Chem (2012) 308: 153–174

DOI: 10.1007/128_2011_241

# Springer-Verlag Berlin Heidelberg 2011

Published online: 14 September 2011



Fluorous Catalysis: From the Origin

to Recent Advances

Jean-Marc Vincent



Abstract Among the various strategies developed in the last two decades to

recycle catalysts, fluorous catalysis has emerged as one of the most powerful

approaches as it combines the advantages of homogeneous catalysis for reactivity

(molecular catalysts, most often reactions conducted in one-phase homogeneous

conditions) and heterogeneous catalysis for catalyst recovery (liquid/liquid- or

solid/liquid-phase separation protocols). Of particular interest is the general character of this approach and the variety and efficiency of separation protocols

available to recover catalysts.

Keywords Fluorous catalysis Á Fluorous chemistry Á Green chemistry Á

Perfluorocarbons Á Purification procedures Á Separation techniques



Contents

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2 Liquid/Liquid Phase Separation: Fluorous Biphasic Catalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.1 Metal-Based Catalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.2 Organocatalysis and Biocatalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3 Solid/Liquid Phase Separation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.1 Fluorous Solid-Phase Extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.2 Supported Fluorous Phase Catalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.3 Precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



154

156

156

162

164

164

165

167

169

170



J.-M. Vincent (*)

Institute of Molecular Sciences, University of Bordeaux, UMR CNRS 5255, 351, Cours de la

Libe´ration, 33405 Talence Cedex, France

e-mail: jm.vincent@ism.u-bordeaux1.fr



154



J.-M. Vincent



1 Introduction

Most chemical reactions, whether they are conducted in industry on large scales or

in smaller scales in research and development laboratories, require a catalyst to

proceed efficiently. Triggered by both environmental and economic concerns, as

catalysis very often deals with potentially toxic and/or costly metal complexes, the

search for recoverable catalysts has become a major concern of modern chemistry

[1]. As outlined by Gladysz [2], a recoverable catalyst would, ideally, satisfy an

exacting set of criteria related to its preparation (low cost, easy synthesis and

handling, being non-toxic and hazard-free), its reactivity (no activation, giving

100% product yield, fast kinetics at ambient temperature, low loading), and its

recovery (quantitative by decantation or filtration). Beside the environmental issue,

routinely used automated synthesis applied to drug discovery has pushed toward the

development of adapted synthetic methodologies for the rapid and efficient purification of the product while being able to recycle the catalyst if needed. Fluorous

catalysis emerged in 1994 [3] with the publication of the Fluorous Biphasic

Catalysis (FBC) concept first applied to the rhodium(I) catalyzed hydroformylation

of alkenes by Horva´th and Ra´bai in Science magazine. Since this seminal work,

there has been an enormous interest in developing catalyst separation/recovery

procedures exploiting the unique physico-chemical properties of the perfluoroalkyl

tags in association with perfluorocarbons (PFC) or fluorous supports, i.e., fluorous

silica and perfluoropolymers [4–7]. A selection of fluorous ligands,

organocatalysts/phase transfer catalysts developed within the past 17 years, is

shown in Schemes 1 and 2.

The variety of fluorous ligands now available illustrates the fact that essentially

all important catalytic processes exist in a fluorous version. Among the many

strategies developed in recent years for the recovery of catalysts [1], fluorous

catalysis is undoubtedly one of the most powerful and general approaches for the

following reasons: (1) fluorous catalysis deals with molecular catalysts displaying

structures and reactivity similar to their non-fluorous analogs; (2) in most cases

reactions are conducted in optimal homogeneous conditions for reactivity while a

range of separation strategies based on liquid/liquid or solid/liquid separation

procedures are available; (3) the modification of ligands/catalysts by the fluorous

tags, can be achieved by straightforward reactions from commercially available

fluorous reactants.

The objective of this chapter is not to provide an exhaustive list of fluorous

catalysts and related reactions, but rather to highlight the variety of conceptually

innovative catalyst recovery procedures developed so far which exploit the specific

properties of the perfluoroalkyl chains. Each type of separation/recovery procedure

will be illustrated by one or several examples of representative catalytic processes.



Fluorous Catalysis: From the Origin to Recent Advances



155

Rf8



Rfn



Rfn



P



n = 6, 8, 10

Rfn



NH



1



Rf8



Rf3

Rf8



N



Rf3



NH



Rf3

HN



N



Rf8



N

HN



N



Rf8



Rf8

Rf8



2



Rf3



5

O

Rf7



N

N



Rf8



O

Rf8



Rf7



4



Rf8



N

6



Rf8



Rf8



Rf8

Rf8



Rf8

CO2H



8



NH HN



N



Rf8

Rf8



N



H



7



Rf8



Rf8



H



Rf8



Rf8



N



N



OH HO



10

Rf8



Rf8

9



(Rf6)3Si



(Rf6)3Si



Rf6



OH

PPh2



OH



PPh2

(Rf6)3Si



11



Rf6



(Rf6)3Si

12



Rf8



P

17

Rf6



Rf8

P



Rfn = (CF2)n -1CF3

27

Rf8



Scheme 1 Structures of some fluorous ligands synthesized since 1994



156



J.-M. Vincent



O

N



Rf6



Rf8



N



+

P



N



O

N



I



O







Rf6



Rf6



N



18



O

O



O



H



Rf8



H

N



N

Ph



Rf8



20



Rf8



N

23



O



Rf8



Rf8



N

H



O



O



19



Rf8



Rf8



Rf8



Rf8



Rf8



N



O



O



Rf8



O

24



N

H



OH



Rf8



25

N N

N



Rf8

N N

N

O



O

O



N

N N



Rf8



O



N O



Rf8



N

N



Si



Si

Si



Si



Br –

+

N



Rf8



Rf8



29



Si



Si

Si



Si



Rf8



30



N

N



+N

H



Rf8



N



Rf8



Rf7 CO2–



Rf8



31



IRf8



Rf8



Rf8



N

Rf8I



32



Rfn = (CF2)n-1CF3



Scheme 2 Structures of some fluorous organocatalysts synthesized in recent years



2 Liquid/Liquid Phase Separation: Fluorous Biphasic Catalysis

2.1



Metal-Based Catalysis



The FBC concept, reported by Horva´th and Ra´bai in 1994 [3]1, was first applied

to the rhodium(I) catalyzed hydroformylation of alkenes. The thermomorphic

properties of PFC and hydrocarbons (HC) were exploited to run the



1



In 1991 Vogt M defended a PhD thesis entitled “The application of perfluorinated polyethers for

the immobilization of homogeneous catalysts,” Rheinisch-Wesf€alischen Technischen Hochschule,

Aachen, Germany. Results from this work were published in 1999. See [8].



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