WO2000000455A1

WO2000000455A1 - Perfluorovinyl ether compounds and resins

Info

Publication number: WO2000000455A1
Application number: PCT/GB1999/001893
Authority: WO
Inventors: David Gani; Mahmoud Akhtar; Shuyuan Liu
Original assignee: The University Court Of The University Of St Andrews
Priority date: 1998-06-27
Filing date: 1999-06-28
Publication date: 2000-01-06
Also published as: GB9813862D0; AU4517999A

Abstract

There is provided perfluorovinyl ether compounds which can be used to prepare functionalised perfluoropolymer based resins. Preferred resins have formulae (B1) and (B2), where R represents H or a protecting group such as -C(CH3)3, -CH2C6H5, SiR3, or 2-tetrahydropyranyl. The resins are suitable for solid-phase synthesis or combinatorial chemistry.

Description

Perfluorovinyl Ether Compounds and Resins

The present application describes the synthesis of functionalised fluoroalkenyl ether monomers for use in the preparation of functionalised perfluoropolymer- based resins suitable for solid-phase synthesis (SPOS) and combinatorial chemistry.

In 1963 Merrifield first described a method for "solid phase" peptide synthesis. In this method the first amino acid residue was covalently bonded to a modified polystyrene resin through a resin benzyloxy group ester linkage formed using the carboxyl group of a N- protected amino acid. Subsequently sequential deprotection and peptide bond coupling steps were performed to give a resin-bound tetrapeptide that could be removed from the resin by treament with hydrofluoric acid, for example, to afford the free tetrapeptide (R. B. Merrifield, J. Am. Chem. Soc . , 1963, 85, 2149). Soon after, this method was automated (R. B. Merrifield, J. M. Stewart and N. Jernberg, Anal. Chem., 1966, 38, 1905) and larger peptides were synthesised culminating in the so-called solid-phase synthesis of ribonuclease A, an enzyme containing 124 amino acid residues (B. Gutter and R. B. Merrifield, J. Biol . Chem., 1971, 246, 1922). This novel approach revolutionalised peptide synthesis and Merrifield was awarded the 1984 Nobel Prize for Chemistry. Polymer supported reactions, strictly speaking, are not "solid-phase" reactions, but are inter-phase, multi- phase or gel-phase reactions which are quite different from solid-phase reactions. In the supported synthesis, the polymer supports act as "solid protecting groups" which enables the multi-step synthesis to be carried out easily and cleanly. The advantages of the supported methods are not, however, limited to the synthesis of natural polymers and there are many applications in other areas of organic synthesis. Over a thousand papers have been published on topics unrelated to peptide synthesis over the past 30 years. However, few of these were published prior to 1990 when supported synthesis experienced a second major revolution, this time in the context of combinatorial chemistry (M. A. Gallop, R. . Barrett, . J. Dower, S. P. A. Fodor and E. M. Gordon, J. Med. Chem., 1994, 37, 1233; J. Med. Chem., 1994, 37, 1384; F. Balbenhol , C. von den Bussche-Hύnnefeld, A. Lansky and C. Zechel, Angew. Chem. Int. Ed. Engl . , 1996, 35, 2288; L.A. Thompson and J. A. Ellman, Chem. Rev., 1996, 96, 555: J. S. Frύchtel and G. Jung, Angew. Chem. Int. Ed. Engl., 1996, 35, 17; P. H. H. Hermkens, H. C. J. Ottenheim and D. Rees, Tetrahedron, 1996, 52, 4527; Tetrahedron, 1997, 53, 5643; and H. Maehr, Bioorg. Med. Chem., 1997, 5, 473). Combinatorial chemistry, together with supported synthesis, offers the promise of rapid drug discovery through facilitating the synthesis of a large number of often structurally diverse compounds very quickly. Using an automated approach to synthesise such compounds and/or to rapidly screen the products hastens the identification of potential drug leads.

With the upsurge of interest in polymer supported synthesis, especially with regard to the increasing range of synthetic reactions that have been performed in the solid-phase, together with the concomitant improvements in the automation and robotisation of organic synthesis, the requirements demanded of the supporting resin materials has increased. There is a constant need to develop better polymer supports with higher loading capacities, good site accessibilities, stronger mechanical properties and improved chemical and thermal stability to facilitate more sophisticated chemical reaction protocols and synthetic processes. Remarkably, Merrifield' s original resins based on chloromethlylated polystrene lightly cross-linked with 1-2% divinylbenzene (PS-DVB) have proved to be immensely versatile, but nevertheless, suffer from a number of limitations which restrict their use in organic synthesis.

First, lightly crosslinked polystyrene supports swell considerably in organic solvents. Indeed the swelling factor can be more than 5- fold, making them rather fragile and difficult to handle. Swelling is necessary for the reaction of polystyrene supports to allow the diffusion of the reactants through the polymer-solvent gel-phase into the "active functionalised site". For the highly crosslinked PS-DVB (20-40 %) porous polymer beads, these often fracture in solvent and cannot swell without retarding the rates of species diffusion near the surface of the polymer. Thus, solvents and substrates can only pass through the pores slowly and the loading capacity is effectively reduced by the more rigid frame matrix. Although the loading capacity can be improved by grafting on the surface of the pores, site-site chemical and steric interaction between active sites (due to highly concentrated microenvironments) tends to exert a detrimental effect on facile, clean synthesis.

Second, conventional polymer supports are not chemically or thermally stable enough to withstand certain required reaction conditions. For example, several extreme conditions of strong acidity or basicity used in conventional solution phase organic chemistry are too harsh for the polymer, or for the linker groups which connect the functional reacting moieties to the polymer backbone. These problems include instances where the resins react with the reagents at the wrong site, for example, with the polymer itself or with the linker, and instances where the reagents or elevated temperatures cause the partial or total decomposition of the resin system.

Very similar problems exist in the use of polymer supported transition metal catalysts where the polymer itself or the linker/ligand systems are unstable to the most suitable conditions for the reaction, e.g. high temperature. Here the advantages in stably supporting the catalyst on a polymer which permanently immobilises the transistion metal are significant in separating/recovering expensive catalytic metals and in providing the highest possible purities of the products.

To overcome such problems of polymer incompatibility with the reaction conditions it is necessary to develop custom designed "new generation" polymer supports for SPOS, combinatorial chemistry technology and transition metal catalyst immobilisation. Customised fluoropolymers offer considerable potential in this area although the design and preparation of such materials present many challenges. Perfluoropolymers are known to be extremely stable polymers due to the strong C-F bonding which also enhances C-C bonding in the polymer backbone. Their chemical inertness and thermal stability, along with other special properties, render perfluorinated resins the most suitable of all polymer materials for SPOS. The introduction of branches in the perfluoropolymer backbone through the co-polymerisation of tetrafluoroethylene (TFE) with hexafluoropropene (HFP) or perfluorovinyl ethers is known to lead to improved thermal processability of the PTFE material while retaining the thermal and chemical stability, e.g.- as in Teflon^®-FEP (perfluorinated ethylene- propylene) resin (Encyclopedia of Polymer Science and Technology, edited by H F Mark, N M Bikales, C G Overberger and G Menges, John Wiley & Sons, Chichester, UK, Volume 16, page 601) and Teflon^®-PFA (perfluoroalkoxy) fluorocarbon resin (Encyclopedia of Polymer Science and Technology, edited by H F Mark, N M Bikales, C G Overberger and G Menges, John Wiley & Sons, Chichester, UK, Volume 16, page 614) .

In the early 1970' s, Du Pont introduced the first perfluoroionomer membranes dubbed Nafion^® (see US Patent No 3,282,875 to Du Pont), which were based on copolymers of TFE with a perfluorovinyl ether containing a perfluoroalkyl sulfonyl fluoride group, which in the final membrane is hydrolysed to the sulfonic acid. These types of perfluoropolymers have been widely used in membrane cell technology for the electrolysis of aqueous sodium chloride for chloralkali production because of their chemical stability and high ion selectivity (H. C. Fielding, ICI Chemicals and Polymers, "Fluoropolymer Membranes", Fluoropolymers Conference, 1992) . We have already assessed the possibility of using Nafion^® resin as a support for solid-phase synthesis and have shown that a wide range of reaction types can be achieved (see WO-A-99/07750) . In this work the sulfonic acid moiety was first activated as the sulfonyl chloride and then derivatised with a number of appropriately functionalised alkylamines or anilines. Thus, the N-atom provided a link to the sulfonyl group, to give a sulfonamide or a sulfanilamide, and the functionalised portion could take part in synthetic transformations. While this approach, using Nafion^® as a polymer support in the solid-phase synthesis, was encouraging in that the system displayed superior chemical and thermal stability under many extremely harsh conditions and did facilitate the required chemical reactions, the rates and the yields of reactions were low.

One of the major reasons for low conversion efficiencies is the poor accessibility of the active functionalised sites within the polymer resin due, in part, to the fact that the polymer backbone and functionalised side-chains are perfluorinated and therefore fluorophilic . Thus, the side-chains are simultaneously lipophobic and hydrophobic and repel organic and aqueous solvents, except in the vicinity of the alkylamino or arylamino moieties of the sulfonamides . Unfortunately, the size of the side- chain and linker is such that there is little remaining space for synthesis, which requires contact between reagent, molecules and the functionalised resin- supported moieties, before the exclusion volume of the microenviroment (which is defined by the polymer matrix) is exceeded. Thus, only small molecules can be synthesised using derivatised perfluoroalkylsulfonic acid based systems such as Nafion^®, and Nafion^® is not ideally suited for generic solid-phase organic chemistry.

In the first aspect of this invention, a new range of perfluoropolymer supported functionalised-hydrocarbon polymer resins are envisaged where the functionalised hydrocarbon side-chains will be repelled into solvent by the perfluorocarbon back-bone such that the functional groups will be more accessible to the solvent and solvated reagents for synthesis. The hydrocarbon side-chains also provide greater flexibility and less motional restraint than the perfluoroalkyl chains used in Nafion^® resins and in similar products produced by the Ashai and Dow companies. Furthermore, the hydrocarbon side-chains are smaller, intrinsically, and allow the use of less elaborate linkers such that less space would be required within the polymer matrix for linkage, leaving more space for reagent access. Hence, many of the problems in using Nafion® -based resins are circumvented.

In the second aspect of this invention we describe the design of suitably functionalised monomers for use in the construction of resin materials, of the type described in the first aspect of this invention, that will possess sufficient stability for use in organic synthesis and polymer supported catalysis under the harsh conditions of protic acids, Lewis acids, bases, strong nucleophiles and high and low temperature.

In the third aspect of this invention we describe the synthesis and properties of suitably functionalised monomers which can be incorporated into the desired resin materials and thence, into custom resins for solid-phase organic synthesis or polymer supported catalysis by a man skilled in the art.

The availability of new stable custom designed resins will facilitate the use of solid phase protocols in a fuller range of reaction types and catalytic chemistry.

This application describes the design and preparation of novel functionalized alkyl perfluorovinyl ether co- monomers suitable for co-polymerisation with tetrafluoroethylene (TFE) . The present invention concerns such co-monomers which are functionalised perfluorovinyl ethers derived from dialcohols (diols) or diol precursors where one alcoholic functionality is used to secure the alcohol bearing moiety to a fluorinated alkene, as in precursors for the well-known Teflon-PFA resin, and where the other alcohol moiety or some equivalent functional moiety, is used to tether the functional active-site groups to the fluoropolymer after the fluorinated alkene groups have been co- polymerised with tetrafluoroethylene . The novel aspects of the invention stem from the inclusion of the second alcohol moiety or some equivalent functional group. Thus, the functionalised monomers have the structure A, R-0-X-0-CY=CFR' where R = H or a common alcohol protecting group (for example, -C(CH₃)₃, -CH₂C₆H₅, SiR"₃ or 2-tetrahydropyranyl which can be removed selectively) ; where X is an alkyl or aryl moiety or some other suitable inert spacer which separates the two O-atoms; where Y is H, F, Cl , CH₃ or CF₃, and; where R' is H, F, Cl, CH₃ or CF₃. R-O in structure A could also be "masked" as an alcohol or ether precursor, for example, R-0 could be replaced by a chlorine atom or some other suitable leaving group.

The present invention provides perfluorovinyl ethers of general formula A: A: Z-X-0-CY=CFR'

wherein Z represents an aryl group, an alcohol or ether precursor (for example a chlorine atom or other leaving group) or a group R-O- wherein R represents H or an alcohol protecting group (preferably an alcohol protecting group which can be removed selectively) ;

X represents an alkyl or aryl moiety or any other inert spacer group;

Y represents H, Cl , F, CH₃ or CF₃ ; and

R' represents H, Cl , F, CH₃ or CF₃.

Preferably group X represents a group -(CH₂)₂-, -(CH₂)₃-, -CH(CH₃) -CH₂-, -CH(CH₃) -CH₂CH₂- or -(CH₂)₄..

Preferably R = H, -C(CH₃)₃, -CH₂C₆H₅ in structure A and preferably X = -(CH₂)₂-, -(CH₂)₃-, -CH (CH₃) CH₂- , or -(CH₂)₄- or bis-substituted meta- or para- dialkylbenzenes . Preferably group Z represents a moiety R-O- wherein R represents H, -C(CH₃)₃, -CH₂C_SH₅, -SiR₃ or 2-tetrahydropyranyl.

Preferably, where group Z represents a moiety R-O- , group R represents H, -C(CH₃)₃ or -CH₂C₆H₅ and group X represents -(CH₂)₂-, -(CH₂)₃-, -CH (CH₃) CH₂- , -(CH₂)₄- or bis-substituted meta- or para-dialkylbenzenes .

Preferably groups Y and R' may each independently represent H, F or CF₃. More preferably both groups Y and R' represent F, or group Y represents H and group R' represents F or CF₃.

Preferably both Y and R' should be small and should be fluorine atoms to facilitate efficient incorporation of the co-monomer into the polymer since it is known that larger groups exert detrimental steric effects which retard co-monomer incorporation. Y could be a hydrogen atom where the subsequent use of the polymer resin in synthesis would not involve the use of strong bases that can remove the hydrogen atom as a proton. R' could be a -CF₃ group and would be preferred because its presence would confer good thermoprocessing properties where its introduction would not completely prevent the incorporation of the co-monomer into the polymer resin. However, there are other proven methods for improving thermoprocessibility including incorporating an additional co-monomer, e.g. hexafluoropropene, to break-up the natural crystallinity of PTFE .

Preferred perfluorovinyl ethers of the present invention include those of general formula Al and A2 , where group R represents H or a protecting group (for example -C(CH₃)₃, -CH₂C₆H₅, -SiR₃ or 2-tetrahydropyranyl).

Al A2

The present invention further provides perfluoropolymer resins derived from the perfluorovinyl ether monomers described above. Preferably, the monomers of the invention are combined with tetrafluoroethylene (TFE) to provide a co-polymer resin. One or more different monomer types may be present .

In general terms the moiety -CY=CFR' of monomer A becomes incorporated into the backbone structure of the polymer, with moiety -O-X-Z forming a functionalised side chain.

Thus, for example, preferred monomers Al and A2 will each combine with TFE to produced polymers represented by formulae Bl and B2 respectively (wherein group R represents H or a protecting group (for example -C(CH₃)₃, -CH₂C₆H₅, -SiR₃ or 2-tetrahydropyranyl) .

Bl B2

Where group Z represents an aryl group, this can be functionalised by incorporation of a suitable functional moiety following polymerisation. For example, the aryl group could be chloromethylated.

The polymerisation reaction could be accomplished either with or without the alcohol protecting group in- place and the un-masked alcohol in the polymerised material would be functionalised as is commonplace in the preparation of customised resins for solid-phase synthesis, for example, by activation as a leaving group (e.g. a tosylate) for reaction with a nucleophile, or by reaction of the resin-bound alkoxide with an alkylating agent.

The preparation of simple perfluorovinyl alkyl ethers have been reported using both tetrafluoroethylene (TFE) and hexafluoropropene (HFP) and alcoholate nucleophiles (see US Patent 2,917,548; K. Okuhara, H. Baba and R. Kojima, Bull. Chem. Soc . Jpn. , 1962, 35, 532; and M. H. Hung, S. Rozen and B. E. Smart, J. Org. Chem., 1994, 59, 4322) . In this reaction the alkoxide adds to the electron deficient double bond to give a carbanion which then eliminates fluoride ion to afford the perfluorovinyl alkyl ether. In such reactions, it is important to prevent protona ion of the intermediate carbanion and, therefore, it is not useful to react the monoalkoxide anions of diols directly with TFE or HFP. The reaction of diol bis-alkoxides with TFE or HPF does work but other side reactions result including the reaction of both "ends" of a given diol moiety with two different fluoroolefin molecules. In order to circumvent such problems, the diol can be protected or masked on one of the hydroxy groups and then deprotected later on. This reduces the immediate problem to preparing a mono-protected diol and reacting this with TFE or HFP. Since several mono- protected diols are either readily available or are easily accessible, this strategy was employed and co- monomers 1 and 2 were synthesised as depicted in Scheme 1. Monomer 1 was obtained by reacting hexafluoropropene with the lithium salt of 1-tert- butoxy-2-propanol under moderate pressure in greater than 95% yield. The subsequent deprotection was achieved using Lewis acids, e.g. titanium tetrachloride at low temperatures, to give the alcohol 2 in 70 % yield.

HFP

Scheme 1

TFE based ether monomers 3 and 4 were obtained in a similar manner (Scheme 2) .

TFE

TiCl₄ (0.5 equiv.) OfeCk, l min, tf c

Scheme 2

Using a similar approach other co-monomers including 6 and 7 were synthesised, in 95% and 70% yield respectively (Schemes 3 and 4) . These momoners are one carbon longer and possess a benzyl ether protecting group.

Scheme 3

Using the same strategy TFE based monomers were also synthesised (Scheme 4) .

TFE

Scheme 4

Changing the 3 -benzyloxy ether group to a 3 - tert-butoxy ether offered advantages in product separation after the deprotection step as removal of tert-butylchloride is far easier than that of benzylchloride (Scheme 5, where n=l or 2) .

11 10 Scheme 5

Both the protected and deprotected monomers have the potential to copolymerise with TFE and such polymerisations have been achieved in the case of perfluorovinyl ethers on a commercial scale. The deprotected monomers are expected to be more reactive because of their smaller size. They do display the expected better solubility properties in the aqueous suspension media containing the emulsifying agent, ammonium perfluorooctanate (APFO) .

While the idea of introducing functionalised fluorovinyl alkyl ether co-monomers possessing alcohol or masked alcohol functionalities has been the main focus of this application, other functional groups could serve a similar function and would be within the spirit of the invention described here. For example, the functional group (OH or masked OH) in the perfluorovinyl alkyl ethers of type Al and A2 , or other variants of structure A above, could be replaced by an aryl group which can be chloromethylated after the polymerisation reaction to give an analogous type of perfluoropolymer support (Scheme 6) .

15

TFE/mitiator

Another type of co-monomer that is within the scope of structure A has been prepared using trifluoroethanol as starting material (Scheme 7) . This would lead to a polymer support which is considerably cheaper but slightly less stable to strong bases than the fully fluorinated backbone types.

18

Scheme 7 Under controlled polymerisation conditions in the presence of an initiator, free-radical copolymerisation of all of the above mentioned co-monomers to give corresponding copolymers could be accomplished through minor modifications of existing protocols by the man skilled in the art.

The present invention further provides a method of producing a perfluoropolymer resin, said method comprising:

a) providing a perfluorovinyl ether monomer of _. general formula A (where groups Z, X, Y and R' are each as defined above) ;

b) co-polymerising the monomer of step a) with tetrafluoroethylene;

c) optionally removing any protecting group and/or introducing functionalised groups onto the side- chain of the polymer.

The present invention further provides the use of the perfluoropolymer resins described above in the solid- phase synthesis of chemical compounds.

The present invention will now be further described by reference to the following, non-limiting, examples.

Example 1 . Synthesis of CF₃CF=CFOCH (CH₃ ) CH₂OH ( 2 ) via compound 1

I. Conversion of 1- tert-butoxy-2 -propanol to the lithium salt .

To a stirred solution of 1- tert-butoxy-2 -propanol (26.4 g, 0.2 mol) in anhydrous diethyl ether (30 cm³) was added dropwise a solution of BuLi in hexane (2.5 M, 80 cm³, 0.2 mol) under argon at -70 to -30 °C (using a methanol-dry ice bath) . The solution was stirred for a further 1 hour and when the solution had reached ambient temperature it was used immediately as described below.

II. Etherification of hexafluoropropene

Trans Cis The lithium alkoxide solution was transferred into a 250 cm³ stainless steel autoclave under nitrogen. The pressure vessel system was sealed and then evacuated and flushed with nitrogen three times. After the final evacuation, the vessel was charged with hexafluoropropene at 40 psi. Upon agitation the internal vessel pressure reduced quickly, as a result of the reaction, and the vessel was re-charged with hexafluoropropene . This process was repeated until no further drop in pressure could be detected. After 2 hours at 50 °C, the liquid phase containing the required product and diethyl ether was collected and the solid residue was extracted with diethyl ether (5 x 25 cm³) . The combined organic extracts were dried (MgS0₄) and the solvent was removed under reduced pressure to give the perfluorovinyl ether 1 (50 g, 95%) . No further purification was required.

umax/cπr¹ 1760 (FC=CF) ; δ_H(300 MHz; CDC1₃) 1.19 (t and c, 9 H_d, s) 1.36 and 1.33 (t and c, 3 H, d, ^" _Hc 6.41, H_a) , 3.37-3.55 (t and c, 2 H, m, H_b) and 4.48-4.65 (t and c, 1 H, m, H_c) ; δ_c(75.4 MHz; CDC1₃) 26.17 (t, C_d) , 26.37 (c, C_d) , 15.48 (c, C_a) , 15.66 (t, C_a) , 64.33 (c, C_b) , 65.01 (t, C_b) , 72.50 (c, C_e) , 72.70 (t, C_e) , 79.06 (t, C_c) , 79.63 (c, C_c) , 114.00-126.05 (c, t, m, C_c. C_b.) and .145.50-156.25 (c, t, m, C_a) ; δ_F(282.3 MHz; CDC1₃) trans isomer: -194.28 (I F, 2 x q, J_Fb 120.9, J_Fa 13.9, F_c) , -107.17 (I F, 2 x q, J^" _Fc 120.9, J^" _Fa 21.8, F_b) and -67.73 (I F, 2 x d, J^" _Fb 21.8, J_Fc 13.9, F_a) ; cis isomer: -188.26 to -188.07 (1 F, m, F_c) , -90.809 to -90.74 (1 F, m, F_b) and -67.30 (3 F, 2 x d, J^" _Fb 13.87, J_Fc 9.91, F_a) .

III) Cleavage of the butoxy ether using TiCl

Trans Cis

To a stirred solution of t-butyl ether monomer 1 (2.62 g, 10 mmol) in anhydrous CH₂C1₂ (10 cm³) was added a solution of TiCl₄ in CH₂C1₂ (1 M, 5 cm³, 5 mmol) at 0 °C over 1 minute. Ice-cold water (5 cm³) was added and, after stirring for a further 5 minutes, the aqueous phase was extracted with diethyl ether (2 x 10 cm³) . The combined organic extracts were dried (MgSO and concentrated under reduced pressure to give a pale yellow oil which was purified by column chromatography (diethyl ether-hexane, 3:1) to give monomer 2 (1.85 g, 90%) .

υmax/cm^"1 3410 br (0-H) and 1760 (FC=CF) ; δ_H(300 MHz; CDC1₃) 1.38 (t, 3 H, d, ^" _Hc 6.41, H_a) , 1.34 (c, 3 H_a, d, J_Hc 6.41, H_a) , 1.91 (1 H, br . s, H_d) , 3.61-3.77 (2 H, m, H_b) and 4.48-4.65 (1 H, m, H_c) ; δ_c(75.4 MHz; CDCl₃) 14.40 (c, C_a) , 15.01 (t, C_a) , 64.99 (c, C_b) , 65.06 (t, C_b) , 81.43 (t, C_c) , 81.60 (c, C_c) , 114.05-127.30 (c and t, m, C_a. and C_b.) and 149.20-155.20 (c and t, m, C_c. ) ; δ_F(282.3 MHz; CDC1₃) trans isomer: -192.02 (I F, 2 x q, J_Fb 120.9, J_Fa 13.87, F_c) , -106.91 (1 F, 2 x q, J_Fc 120.9, J_Fa 21.79, F_b) , -67.88 (I F, 2 x d, J_Fh 21.8, J_Fc 13.87, F_a) ; cis isomer: -185.24 to -185.13 (1 F, m, F_c) , -90.03 to -90.94 (1 F, m, F_b) and -67.36 to -67.28 (3 F, 2 x d, J_Fb 13.8, J_Fc 9.91, F_a) .

Example 2. Synthesis of CF₃CF=CFOCH₂CH₂CH₂OH (4) via compound 3

I. Conversion of 3 -benzyloxy-3 -propanol to the lithium salt

To a stirred solution of 3 -benyloxy-1 -propanol (25 cm³, 0.156 mol) in anhydrous diethyl ether (70 cm³) was added dropwise a solution of BuLi (2.5 M, 65 cm³, 0.16 mol) under argon at -70 °C (using a methanol-dry ice bath) . The solution was stirred for a further 1 hour and allowed to warm to ambient temperature and was then used immediately as described below.

II. Etherification of hexafluoropropene

Trans Cis The lithium alkoxide solution was transferred into a 250 cm³ stainless steel autoclave under nitrogen. The pressure vessel system was sealed, evacuated, flushed with nitrogen three times and then charged repeatedly with hexafluoropropene at 40 psi as described above for the preparation of compound 1. After 2 hours at 50 °C, the liquid phase containing the desired product and diethyl ether was collected and the solid residue was extracted with diethyl ether (5 x 25 cm³) . The combined organic extracts were dried (MgS0₄) and the solvent was removed under pressure to give the desired perfluorovinyl ether 3 (46 g, 96%) . No further purification was required.

υ^ cm¹ 1760 (FC=CF) ; δ_H(300 MHz; CDC1₃) 2.06 (t, 2 H, quin., J 6.04, H_a) , 1.98 (c, 2 H, quin., J^" 6.04, H_a) , 3.62 (t, 2 H, t, J 6.04, H_b) , 3.57 (c, 2 H, t, J^" 6.04, H_b) , 4.34 (t, 2 H, t, J 6.04, H_c) , 4.15 (c, 2 H, t, J 6.04, H_c) 4.53 (t, 2 H, s, H_d) , 4.52 cis (c, 2 H, s, H_d) and 7.25-7.42 (t, and c, 5 H, m, H_e) ; δ_c(75.4 MHz; CDC1₃) 26.17 (t, C_d) , 26.371 (c, C_d) , 15.48 (c, C_a) , 15.66 (t, C_a) , 64.33 (c, C_b) , 65.01 (t, C_b) , 72.50 (c, C_e) , 72.70 (t, C_e) , 79.06 (t, C_c) , 79.63 cis (c, C_c) , 114.20-126.42 (c and t, m, C_c, C_b, ) and 145.10-156.38 (c and t, m, C_a) ; δ_F(282.3 MHz; CDC1₃) trans isomer: -194.24 (I F, 2 x q, J_Fb 120.9, J_Fa 13.9, F_c) , -109.52 (1 F, 2 x q, J_Fc 120.9, J_Fa 21.8, F_b) and -67.74 (3 F, 2 x d, J_Fb 21.8, J_FC 13.9, F_a) ; cis isomer: -186.83 to -186.64 (1 F, m, F_c) , -92.87 to -92.71 (1 F, m, F_b) and -67.62 (3 F, 2 x d, J_Fb 13.9, J_Fc 9.9, F_a) .

III) Cleavage of the benzyl group using TiCl4

Trans Cis To a stirred solution of t-butyl ether monomer 3 (15 g, 50 mmol) in anhydrous CH₂C1₂ (50 cm³) was added a solution of TiCl₄ in CH₂C1₂ (1 M, 55 cm³, 55 mmol) at -60 to -30 °C. A standard work-up and purification (as described above) gave compound 4 as an oil (7 g, 70%) .

u^/cm^'1 3410br (O-H) and 1760 (FC=CF) ; δ_H(300 MHz; CDC1₃) 1.68 (1 H, s, H_d) , 2.01 (2 H, quin., J 6.04, H_a) , 3.82 (2 H, t, J 6.04, H_b) and 4.35 (2 H, t, J 6.04, H_c) ; δ_c(75.4 MHz; CDCl₃) 31.42 (c, C_a) , 31.54 (t, C_a) , 57.92 (c and t, C_b) , 69.42 (t, C_c) , 70.65 (c, C_c) , 114.52 to 130.44 (c and t, m, C_b, C_c. ) and 151.61 (c and t, 2 x m, C_a.) ; δ_F(282.3 MHz; CDC1₃) trans isomer: - 194.12 (I F, 2 x q, J_Fb 120.9, J^" _Fa 13.9, F_c) , -109.76 (1 F, 2 x q, J_Fc 120.9, J_Fa 21.79, F_b) and -67.81 (3 F, 2 x d, J_Fb 21.8, J_Fc 13.9, F_a) .

Example 3. Protection of OH groups to be introduced as side chains of the polymer

I. Synthesis of (CH,) ,COCH,CH,CH-,OH

^e(H₃C)₃C-O-CH₂CH₂CH₂— OH (H₃C)₃C-O-CH₂CH₂--OH c a b c b a

^d(H₃C)₃C-O-CH₂CH₂CH₂-Cl (H₃C)₃C-O-CH₂CH₂-Cl _{jj e} c a b c d & a

To a stirred solution of propane-1 , 3-diol (3.80 g, 50 mmol) in THF (20 cm³) was added Amberlyst-15 resin (12 g) . Isobutene was bubbled into this stirring solution at such a rate that almost no excess isobutene was detected at the exit bubbler. The reaction was stopped when 2:1 adduct was observed by TLC . The resin was filtered off and K₂C0₃ (10 g) was added to the filtrate. The crude product was purified by column chromatography to give the required monoprotected diol as a colourless oil (4.3 g, 65%) .

δ_H(300 MHz; CDC1₃) 1.17 (9 H, s, H_β) , 1.87 (2 H, quin., J 5.48, H_a) , 3.75(2 H, t, J 5.48, H_b) , 3.58 (2 H, t, J 5.48, H_c) and 3.22 (1 H, s, H_d) ; δ_c(75.4 MHz; CDC1₃) 27.39 (C_e) , 32.22 (C_a) , 61.74 (C_d) , 63.01 (C_c) and 70.65 (C_b) .

II. Synthesis of (CH,) ,COCH,CH,g_H

This compound was synthesised in the manner identical to that described above in paragraph I . The purified compound was obtained as a colourless oil (4.1g, 70%) .

δ_H(300 MHz; CDC1₃) 1.17 (9 H, s, H_d) , 2.63 (2 H, s, J 6.04, H_c) , 3.42 (2 H, t, J 4.67, H_b) , 3.64 (2 H, t, J 4.67, H_a) ; δ_c(75.4 MHz; CDC1₃) 27.33 (C_d) , 62.08 (C_c) and 62.68 (C_b) and 73.03 (C_a) .

III. Synthesis of (CH,) ,COCH,CH,CH,Cl

This compound was synthesised in the manner identical to that described above in paragraph I, except hexane was used as the solvent. The purified compound was obtained as a colourless oil (7.9g, 95%) .

δ_H(300 MHz; CDCl₃) 1.17 (9 H, s, H_d) , 1.96 (2 H, quin., J 6 . 32 , H_a), 3.48 (2 H, t, J^" 6.32, H_b), 3.64 (2 H, t, J 6.32, H_c) and 1.68 (1 H, s, H_d) ; δ_c(75.4 MHz; CDC1₃) 27.39 (C_d) , 32.31 (C_a) , 42.12 (C_e) , 57.75 (C_b) and 72.72 (C_c) .

IV. Synthesis of (CH,) ,C0CH-,CH,C1

This compound was synthesised in the manner identical to that described above in paragraph I , except hexane was used as the solvent. The purified compound was obtained as a oil (95% yield) .

δ_H(300 MHz; CDCl₃) 1.22 (9 H, s, H_c) and 3.52-3.63 (2 H, m, J 6.04, H_a and H_b) .

Example 4 . Synthesis of CF₃CF=CFOCH₂CH₂C₆H₅ ( 15 )

I. Conversion of 2-phenylalcohol to lithium salt

To a stirred solution of 2-phenylalcohol (2.44 g, 20 mmol) in anhydrous diethyl ether (5 cm³) was added dropwise a solution of BuLi in hexane (2.5 M, 8 cm³, 20 mmol) under argon at -70 to -30°C (using a methanol-dry ice bath) . The solution was stirred for a further for 1 hour and then allowed to warm to ambient temperature.

II. Etherification of hexafluoropropene

Trans _cis The lithium alkoxide solution was transferred into a 50 cm³ autoclave under nitrogen. The pressure vessel system was sealed and then evacuated and flushed with nitrogen three times. After the final evacuation, the vessel was charged with hexafluoropropene at 40 psi. Upon agitation the internal vessel pressure reduced quickly, as a result of the reaction, and the vessel was re- charged with hexafluoropropene . This process was repeated until no further drop in pressure could be observed. After 2 hours at 50 °C, the liquid phase containing the required product and diethyl ether was collected and the solid phase was extracted with diethyl ether (5 x 25 cm³) . The combined organic extracts were dried (MgSO and the solvent removed under pressure to give the perfluorovinyl ether 15. (4.6 g, 92%) . No further purification was required.

umax/cm^"1 1760 (FC=CF) ; δ_H(300 MHz; CDC1₃) 3.08 (2 H, t, J 6.96, H_a) , 4.39 (2 H, t, J^" 6.96, H_b) and 7.22-7.29 (5 H, m, H_b) ; δ_c(75.4 MHz; CDCl₃) 35.67 (C_a) , 72.86 (C_b) and 127.34-129.19 (5C, m, C_c) ; δ_F(282.3 MHz; CDC1₃) trans isomer: -193.88 (1 F, 2 x q, J^" _Fb 120.9, J_Fa 13.9, F_c) , -109.98 (I F, 2 x q, J_Fc 120.9, J^" _Fa 21.8, F_b) and -67.76 (3 F, 2 x d, J_Fb 21.8, J_Fc 13.9, F_a) ; cis isomer: -186.5 to -186.3 (1 F, m, F_c) , -93.2 to -93.0 (1 F, m, F_b) and -67.63 (3 F, 2 x d, ^" _Fb 13.9, J_Fc 9.9, F_a) .

Example 5. Synthesis of CF₂=CFOCH₂CH₂CH₂OC (CH₃) ₃ (10) (n = 2)

I. Conversion of 3 -butoxy-1 -propanol to lithium salt

To a stirred solution of 3 -butoxy-1 -propanol (2.62 g, 20 mmol) in anhydrous diethyl ether (20 cm³) was added dropwise a solution of BuLi (2.5 M, 8 cm³, 20 mmol) under argon at -70 to -30°C (using a methanol-dry ice bath) . The solution was stirred for a 20 minutes, allowed to warm to ambient temperature, and then stirred for a further 2 hours.

II. Etherif ication of tetraf luoroethylene

The lithium alkoxide solution was transferred into a 50 cm³ autoclave under nitrogen. The pressure vessel system was sealed and then evacuated and flushed with nitrogen three times. After the final evacuation, the vessel was charged with tetrafluoroethylene at 50 psi. Upon agitation the internal vessel pressure reduced quickly, as a result of the reaction, and the vessel was re- charged with hexafluoropropene . This process was repeated until no further drop in pressure could be observed. After 5 hours at 50 °C, the liquid phase containing the required product and diethyl ether was collected and the solid phase was extracted with diethyl ether (4 x 10 cm³) . The combined organic extracts were purified using column chromatography (diethyl ether-hexane, 3:1) to give monomer 10 (n = 2) . (2.5 g, 59%) .

δ_H(300 MHz; CDCl₃) 1.19 (9 H, s, H_d) , 1.91 (2 H, quin., J 6.04, H_a) , 3.46 (2 H, t, J- 6.04, H_b) and 4.10 (2 H, t, J 6.04, H_c) ; δ_c(75.4 MHz; CDCl₃) 26.70 (C_d) , 29.85 (C_a) , 56.43 (C_b) , 71.19 (C_e) , 72.12 (C_c) and 134.54 -151.23 (C_a, C_b.) ; δ_F(282.3 MHz; CDCl₃) -135.60 (1 F, 2 x d, J^" _Fa 55.47, J_Fc 108.96, F_b) , -131.86 (1 F, apparent t, J^" _Fa 106.99, J_Fb 108.96, F_c) and -124.72 (2 F, 2 x d, J-_Fb 55.47, J_Fc 106.99, F_a) .

Claims

1. Perfluorovinyl ethers of general formula A:

A: Z-X-0-CY=CFR'

wherein Z represents an aryl group, an alcohol or ether precursor or a group R-O- wherein R represents H or an alcohol protecting group;

X represents an alkyl or aryl moiety or any other inert spacer group;

Y represents H, Cl , F, CH₃ or CF₃ ; and

R' represents H, Cl , F, CH₃ or CF₃.

2. A perfluorovinyl ether as claimed in claim 1 wherein group X represents a group -(CH₂)₂-, -(CH₂)₃-, -CH(CH₃)CH₂-, -CH (CH₃) CH₂CH₂- or -(CH₂)₄-.

3. A perfluorovinyl ether as claimed in either one of claims 1 and 2 wherein group Z represents a moiety R-O- wherein R represents H, -C(CH₃)₃, -CH₂C₆H₅, -SiR₃ or 2-tetrahydropyranyl.

4. A perfluorovinyl ether as claimed in any one of claims 1 to 3 wherein group Z represents a moiety R-0-, group R represents H, -C(CH₃)₃ or -CH₂C₆H₅ and group X represents -(CH₂)₂-, -(CH₂)₃-, -CH (CH₃) CH₂- , (CH₂)₄- or bis-substituted meta- or para- dialkylbenzenes .

5. A perfluorovinyl ether as claimed in any one of claims 1 to 4 wherein groups Y and R' may each independently represent H, F or CF₃.

6. A perfluorovinyl ether as claimed in claim 5 wherein both groups Y and R' represent F, or group Y represents H and group R' represents F or CF₃.

7. A perfluorovinyl ether as claimed in any one of claims 1 to 6 of general formula Al or A2 :

Al A2 where group R represents H or a protecting group.

8. Perfluoropolymer resins derived from the perfluorovinyl ether monomers as claimed in any one of claims 1 to 7.

9. Perfluoropolymer resins as claimed in claim 8 wherein the perfluorovinyl ether monomers are combined with tetrafluoroethylene (TFE) to provide a co-polymer resin.

10. Perfluoropolymer resins as claimed in either one of claims 8 and 9 of general formulae Bl and B2 :

Bl B2 wherein group R represents H or a protecting grou .

11. A method of producing a perfluoropolymer resin, said method comprising:

a) providing a perfluorovinyl ether monomer of general formula A (where groups Z, X, Y and R' are each as defined in Claim 1) ;

b) co-polymerising the monomer of step a) with tetrafluoroethylene;

c) optionally removing any protecting group and/or introducing functionalised groups onto the side-chain of the polymer.

12. Use of the perfluoropolymer resins as claimed in any one of claims 8 to 10 in the solid-phase synthesis of chemical compounds.