(Thio) (meth) acrylate monomers, intermediate compounds for the synthesis of these monomers, polymerisable compositions and polymers obtained, and their optical and ophthalmic uses

The novel monomers correspond to the formula: ##STR1## in which: PA1 Z represents H or CH.sub.3 and X represents O or S, and PA1 Y is a 5- to 8-membered heterocycle consisting of hydrogen, carbon and sulphur atoms and at least two endocyclic sulphur atoms.

The present invention relates, in general, to novel (thio)(meth)acrylate
 monomers, preferably mono(thio)(meth)acrylate monomers, which are useful
 for the formulation of polymerizable compositions leading to transparent
 homopolymers and copolymers that are suitable for optical and ophthalmic
 uses.
 The polymerizable compositions according to the invention allow the
 manufacture of moulded articles made of transparent polymer, which is
 preferably thermoplastic, by polymerization in moulds or by
 injection-moulding.
 The transparent polymers obtained, which have refractive indices of medium
 to high value, 1.54 or more, are particularly suitable for optical and
 ophthalmic uses.
 Among the optical uses of the polymers according to the invention, mention
 may be made of wave guides and optical fibres.
 Among the ophthalmic uses of these polymers, mention may be made of
 spectacle lenses and contact lenses.
 In general, novel monomers according to the present invention are
 functional monomers of mono(thio)(meth)acrylate or mono- and
 di(meth)acrylate type bearing a 5- to 8-membered heterocycle consisting of
 hydrogen, carbon and sulphur atoms and having at least two endocyclic
 sulphur atoms. Preferably, the heterocycle is 6- or 7-membered, better
 still 6-membered. Also preferably, the number of endocyclic sulphur atoms
 is 2 or 3. The heterocycle can optionally be fused with a substituted or
 unsubstituted C.sub.5 -C.sub.8 aromatic or polycyclanic ring, preferably a
 C.sub.6 -C.sub.7 ring.
 When the heterocycle of the functional monomers according to the invention
 contains 2 endocyclic sulphur atoms, these endocyclic sulphur atoms are
 preferably in positions 1-3 or 1-4 of the heterocycle. According to the
 invention, the monomer is preferably also a thio(meth)acrylate monomer.
 Lastly, the monomers according to the invention preferably have molar
 masses of between 150 and 400, preferably 150 and 350 and better still
 between 200 and 300.
 More particularly, the novel functional monomers according to the invention
 correspond to the formula
 ##STR2##
 in which Z represents H or CH.sub.3 (preferably CH.sub.3) and X represents
 O or S, and
 when X represents S, Y represents a radical of formula:
 ##STR3##
 where R.sup.1 and R.sup.2 are chosen from H, alkyl radicals, preferably
 C.sub.1 -C.sub.4 alkyl radicals and better still the CH.sub.3 radical, or
 alternatively R.sup.1 and R.sup.2 together form a (CH.sub.2).sub.5
 radical, and n.sub.1 is an integer from 0 to 2 inclusive, and
 when X represents O, Y represents the radical (a) defined above or a
 radical chosen from the radicals of formulae:
 ##STR4##
 in which n.sub.2 is equal to 1 or 2, R.sup.3 represents H or an alkyl
 radical, preferably a C.sub.1 -C.sub.4 alkyl radical and better still a
 CH.sub.3 radical, R.sup.4 represents H or an alkyl radical, preferably a
 C.sub.1 -C.sub.4 alkyl radical and better still a CH.sub.3 or C.sub.2
 H.sub.5 radical, and R.sup.5 is a divalent radical chosen from the groups
 of the following formulae:
 ##STR5##
 in which:
 A denotes an aryl group, preferably a C.sub.6 -C.sub.12 aryl group and
 better still a phenyl group, or an alkyl group, preferably a C.sub.1
 -C.sub.6 alkyl group,
 R' and R" denote, independently of each other, H, an alkyl group,
 preferably a C.sub.1 -C.sub.6 alkyl group, aryl, preferably phenyl, or R'
 or R" can be a group
 ##STR6##
 where R.sup.a is an alkylene group, preferably a C.sub.1 -C.sub.6 alkylene
 group, in particular a --CH.sub.2 -- group, and R.sup.b is H or CH.sub.3,
 n takes the values 0 or 1 and 0.ltoreq.m (integer.ltoreq.4), and
 ##STR7##
 R.sub.6 denotes H or CH.sub.3, and
 Cy denotes a substituted or unsubstituted aryl ring, preferably a phenyl,
 tolyl or norbornyl ring.
 Preferably, R.sup.5 is a divalent radical chosen from:
 ##STR8##
 ##STR9##
 The monomers according to the invention which are particularly recommended
 are the thio(meth)acrylate monomers corresponding to the formula (A) above
 in which X represents a sulphur atom and Y is a radical of formula (a).
 The monomers according to the invention can be prepared by various known
 synthetic processes.
 Among the mono(thio)(meth)acrylic monomers which are preferred according to
 the invention, mention may be made of the monomers of formulae:
 ##STR10##
 ##STR11##
 ##STR12##
 Among the di(meth)acrylic monomers which are preferred according to the
 invention, mention may be made of the monomers of formulae:
 ##STR13##
 in particular the dimethacrylate.

The remainder of the description gives various examples of the synthesis of
 the monomers according to the invention.
 I. Synthesis of Sulphur-containing Rings by Dieckmann Reaction
 ##STR14##
 I.1 Synthesis of the Diesters Ia, IIIa and IVa
 0.2 mol of ethyl mercaptoacetate (2 eq) in 30 ml of toluene and 1 ml of
 concentrated sulphuric acid is introduced into a 250 ml three-necked flask
 equipped with a condenser.
 The reaction mixture is brought to a temperature of 80.degree. C., followed
 by dropwise addition of either 0.1 mol of formaldehyde as a 36% solution
 in water (stabilized with methanol) in the case of the preparation of
 compound Ia, or 0.1 mol of acetone or cyclohexanone in the case of
 compounds IIIa and IVa.
 After this addition, the reaction mixture is maintained at 100.degree. C.
 for 2 hours. Stirring is then continued overnight at room temperature.
 The reaction mixture is concentrated under reduced pressure. The residue is
 taken up in dichloromethane and washed successively with 5% sodium
 hydroxide solution and then with water.
 The organic phase is dried over sodium sulphate, filtered and then
 concentrated under reduced pressure.
 The product thus obtained is purified by distillation under reduced
 pressure.
 Ia: diethyl-3,5-dithiaheptane 1,7-dicarboxylate
 ##STR15##
 Yield=76%.
 Boiling point=126.degree. C./0.1 mm Hg.
 IIIa: diethyl-3,5-dithia(4-dimethyl)heptane 1,7-dicarboxylate
 ##STR16##
 Yield=78%
 Boiling point=131.degree. C./0.1 mmHg.
 IVa: diethyl-3,5-dithia(4-cyclohexyl)heptane 1,7-dicarboxylate
 ##STR17##
 Yield=96%
 Boiling point=165.degree. C./0.3 mm Hg.
 I.2 Dieckmann Cyclization: Use of Sodium Methoxide in Ether
 0.1 mol (2 eq) of freshly prepared sodium methoxide is suspended in 70 ml
 of anhydrous ether; 0.05 mol (1 eq) of diester dissolved in 20 ml of
 anhydrous ether is added dropwise at room temperature. The reaction
 mixture is then stirred for ten hours at reflux. The reaction mixture is
 allowed to cool to room temperature and is then poured into a
 water-ice-acetic acid mixture.
 The aqueous phase is extracted with twice 60 ml of ether. The ether phases
 are washed with dilute sodium hydrogen carbonate solution and then with
 water.
 The organic phase is dried over sodium sulphate and concentrated under
 reduced pressure.
 The .beta.-keto esters thus obtained are used crude in the remainder of the
 synthesis.
 I.3 Decarboxylation of .beta.-keto Esters in Hydrochloric Acid Medium
 0.05 mol of .beta.-keto ester and 120 ml of 1N hydrochloric acid solution
 are introduced into a round-bottomed flask equipped with a condenser. The
 reaction mixture is maintained at 100.degree. C. for a minimum of 20
 hours. The reaction mixture is taken up in 100 ml of ethyl acetate. The
 aqueous phase is neutralized with sodium hydroxide solution to pH 5.
 The organic phase is then washed successively with water and then with
 saturated sodium chloride solution.
 The organic phase is dried over sodium sulphate and then concentrated under
 reduced pressure.
 The thiacycloalcan-3-ones thus obtained will be purified by chromatography
 on silica gel.
 Ib: 1,3-dithiacyclohexan-5-one
 ##STR18##
 Yield=79% relates to the preceding two steps.
 Melting point=101.degree. C.
 IIIb: 2-dimethyl-1,3-dithiacyclohexan-5-one
 ##STR19##
 Yield=28% relates to the preceding two steps.
 Purification eluent: 9% ethyl acetate/91% petroleum ether.
 IVb: 2-cyclohexyl-1,3-dithiacyclohexan-5-one
 ##STR20##
 Yield=88% relates to the preceding two steps.
 Purification eluent: 10% ethyl acetate/90% petroleum ether.
 I.4 Reduction of a Ketone with LiAlH.sub.4 in THF
 0.05 mol (1 eq) of lithium aluminium hydride suspended in 20 ml of
 anhydrous tetrahydrofuran is introduced, under a nitrogen atmosphere, into
 a three-necked flask fitted with a condenser, a stirrer and a dropping
 funnel.
 0.05 mol (1 eq) of the ketone obtained in step I.3, dissolved in 10 ml of
 tetrahydrofuran, is then added dropwise at room temperature.
 After addition, the reaction mixture is refluxed for 12 hours. The solution
 is then allowed to cool to room temperature. The reaction mixture is
 cooled to 0.degree. C .in order to be hydrolysed with 20 ml of water.
 The solution is then poured into 60 ml of 10% sulphuric acid solution. The
 organic phase is separated out and the aqueous phase is extracted with
 three times 60 ml of ether. The combined ether phases are washed
 successively with 50 ml of water and 50 ml of saturated sodium hydrogen
 carbonate solution and then dried over sodium sulphate and concentrated
 under reduced pressure.
 Ic: 1,3-dithiacyclohexan-5-ol
 ##STR21##
 Yield=53%.
 Purification eluent: 20% ethyl acetate/80% petroleum ether.
 IIIc: 2-dimethyl-1,3-dithiacyclohexan-5-ol
 ##STR22##
 Yield=54%.
 Purification eluent: % ethyl acetate/% petroleum ether.
 IVc: 2-cyclohexyl-1,3-dithiacyclohexan-5-ol
 ##STR23##
 Yield=78%.
 Purification eluent: % ethyl acetate/% petroleum ether.
 I.5 Synthesis of Mercaptans from Alcohols: Use of Lawesson's Reagent
 20 mmol (1 eq) of alcohol obtained in the above step, dissolved in 60 ml of
 toluene, and 11 mmol (0.55 eq) of Lawesson's reagent are introduced under
 a nitrogen atmosphere.
 The reaction mixture is maintained at reflux for a variable period
 depending on the substrate.
 The reaction is monitored by thin layer chromatography.
 After the alcohol has disappeared, the reaction mixture is taken up in 100
 ml of water and extracted with twice 50 ml of dichloromethane.
 The combined organic phases are dried over sodium sulphate and then
 concentrated under reduced pressure.
 The mercaptans thus obtained are used crude in the remainder of the
 synthesis.
 IIa: 1,3-dithiacyclohexan-5-thiol
 ##STR24##
 I.6 Coupling of the MAOC with an Alcohol
 0.05 mol (1 eq) of alcohol obtained in step I.4, 0.05 mol (1 eq) of
 triethylamine and 800 ppm of hydroquinone monomethyl ether (HQME) in 300
 ml of chloroform are introduced into a three-necked flask fitted with a
 condenser, a thermometer and a magnetic stirrer. The reaction mixture is
 cooled to 0.degree. C.; 0.055 mol (1 eq) of methacryloyl chloride
 dissolved in 20 ml of chloroform is then added dropwise, while maintaining
 the temperature at 0.degree. C.
 After warming to room temperature, the mixture is left stirring for 48
 hours.
 The reaction mixture is acidified with 50 ml of 6N sulphuric acid solution
 and is extracted with ether. The organic phase is washed successively with
 10% sodium hydrogen carbonate solution and then with saturated sodium
 chloride solution.
 The ether phase is dried over sodium sulphate and the solvent is evaporated
 off.
 The methacrylic compounds thus obtained are purified by chromatography on
 silica gel.
 ##STR25##
 Yield=32%.
 Purification eluent: 1% ethyl acrylate/99% petroleum ether.
 ##STR26##
 Yield=27%.
 Purification eluent: 2% ethyl acetate/98% petroleum ether.
 ##STR27##
 Yield=45%.
 Purification eluent: 1% ethyl acetate/99% petroleum ether.
 I.7 Production of Methacrylic Thioester by Reaction of a Mercaptan with
 Methacrylic Acid in the Presence of Dicyclohexylcarbodiimide and
 Dimethylaminopyridine
 65 mmol of methacrylic acid and 800 ppm of HQME in 70 ml of dichloromethane
 are introduced, with stirring, into a 250 ml three-necked flask. 32.5 Mmol
 of mercaptan obtained in step I.5 and 650 mg of dimethylaminopyridine
 (DMAP) (catalytic amount of 5% by mass relative to the acid) are added
 dropwise, at room temperature. The reaction mixture is then cooled to
 0.degree. C. and 65 mmol of dicyclohexylcarbodiimide (DCC) are added.
 Stirring is continued at 0.degree. C. for five minutes and then at room
 temperature for five hours.
 The reaction mixture is filtered in order to remove the dicyclohexylurea
 formed.
 The filtrate is taken up in dichloromethane and the organic phase is washed
 successively with 0.5 N hydrochloric acid solution and then with 0.5 N
 sodium hydroxide solution. The organic phase is dried, filtered and
 concentrated under reduced pressure.
 The methacrylic thioester thus obtained is purified by chromatography on
 silica gel.
 ##STR28##
 Yield=33%.
 Purification eluent: 2% ethyl acetate/98% petroleum ether.
 II. Preparation of Sulphur-containing Rings by Intermolecular Cyclization
 Reaction
 This cyclization method makes it possible to obtain a series of
 dithiacycloalkane methacrylic monomers according to the scheme below.
 The various steps in this synthesis are:
 coupling of a dimercaptan with dichloroacetone,
 reduction with lithium aluminium hydride in tetrahydrofuran, and
 coupling of methacryloyl chloride with the alcohol obtained above.
 ##STR29##
 PROCEDURES
 II.1 Coupling of Dichloroacetone with a Dimercaptan
 0.1 mol (2 eq) of freshly prepared sodium methoxide is dissolved in 20 ml
 of anhydrous methanol with stirring, followed by addition of 0.05 mol (1
 eq) of the dimercaptan at room temperature.
 In parallel, a solution of 0.05 mol (1 eq) of 1,3-dichloroacetone dissolved
 in about 25 ml of anhydrous ether is prepared.
 These two solutions are simultaneously introduced into a three-necked flask
 with stirring, at room temperature and under a nitrogen atmosphere, over a
 period of about four hours.
 At the end of the addition, the reaction mixture is poured into a
 water-ice-ether mixture containing 10 ml of 10% sodium hydroxide solution.
 The aqueous phase is extracted with three times 40 ml of ether. The white
 precipitate of polymer is separated out by settling. The organic phases
 are combined, dried over sodium sulphate and concentrated under reduced
 pressure.
 Va: 1,4-dithiacycloheptan-6-one
 ##STR30##
 Yield=64%.
 Purification eluent: 5% ethyl acetate/95% petroleum ether.
 VIIa: 1,5-dithiacyclooctan-7-one
 ##STR31##
 Yield=31%.
 Purification eluent: 5% ethyl acetate/95% petroleum ether.
 II.2 Reduction with LiAlH.sub.4 in THF
 The procedure is the same as that for step I.4 above.
 Vb: 1,4-dithiacycloheptan-6-ol
 ##STR32##
 Yield=43%.
 m.p.=65.degree. C.
 Purification eluent: 15% ethyl acetate/85% petroleum ether.
 VIIb: 1,5-dithiacyclooctan-7-ol
 ##STR33##
 Yield=30%.
 Purification eluent: 10% ethyl acetate/90% petroleum ether.
 II.3 Synthesis of Mercaptans from Alcohols: Use of Lawesson's Reagent
 The procedure is the same as that in step I.5 above.
 VIa: 1,4-dithiacycloheptan-6-thiol
 ##STR34##
 II.4 Coupling of MAOC with an Alcohol
 The procedure is the same as that in step I.6 above.
 ##STR35##
 Yield=69%.
 Purification eluent: 5% ethyl acetate/95% petroleum ether.
 ##STR36##
 Yield=23%.
 Purification eluent: 2% ethyl acetate/98% petroleum ether.
 II.5 Reaction of MAOC with a Mercaptan in the Presence of a Tertiary Base
 55 mmol of MAOC diluted in 25 ml of solvent (acetonitrile, acetone or
 toluene) to which 800 ppm of HQME have been added are introduced into a
 reactor under a nitrogen atmosphere, fitted with a thermometer and a
 dropping funnel. The reaction mixture is cooled to -10.degree. C. and the
 mixture: mercaptan from step II.3 (50 mmol) /triethylamine (55 mmol)
 diluted in 10 ml of solvent, is added dropwise.
 Stirring is continued at the same temperature for five hours.
 After filtering off the salt formed, the solvent is removed. The residue is
 taken up in dichloromethane and washed with 0.5 N sodium hydroxide
 solution; the organic phase is dried over sodium sulphate and concentrated
 under reduced pressure.
 The methacrylic thioesters thus obtained are purified by chromatography on
 silica gel.
 ##STR37##
 Yield=30%.
 Purification eluent: 1% ethyl acetate/99% petroleum ether.
 III. Preparation of Sulphur-containing Rings Containing the S--S Unit
 The various steps in this synthesis are:
 treatment of a dihalo derivative with sodium disulphide (Na.sub.2 S.sub.2)
 which allows the cyclic disulphide to be obtained. This method uses a
 phase transfer catalysis reaction;
 next, coupling of methacryloyl chloride with the alcohol obtained above.
 ##STR38##
 PROCEDURES
 III.1 Preparation of the Alcohols VIlIa and IXa
 1/4 mol of Na.sub.2 S.9H.sub.2 O is dissolved in 100 ml of water in a
 three-necked flask fitted with a thermometer and a condenser, and this
 solution is brought to 40.degree. C. 3 sodium hydroxide pellets are then
 added, followed by sulphur, so as to obtain the desired Na.sub.2 S.sub.2
 system (8 g, 1/4 mol for n=2).
 The mixture is cooled to room temperature and 1/4 mol of dibromo derivative
 in 100 ml of dichloromethane is then added. Tetrabutylammonium hydrogen
 sulphate (phase transfer catalyst) is then added (5 mol % relative to the
 halo derivative).
 This solution is refluxed for one hour with stirring and is then cooled to
 room temperature over one hour. The organic phase is taken up in
 dichloromethane and then washed with water and finally dried over sodium
 sulphate. The solvent is then evaporated off under reduced pressure. The
 ring thus obtained is purified by chromatography on silica gel.
 VIIIa: 1,2-dithiacyclopentan-4-ol
 ##STR39##
 Yield=77%.
 Purification eluent: 20% ethyl acetate/80% petroleum ether.
 IXa: 1,2-dithiacyclohexan-4-ol
 ##STR40##
 Yield=95%.
 Purification eluent: 20% ethyl acetate/80% petroleum ether.
 III.3 Addition Reaction of MAOC with an Alcohol
 The procedure is the same as that in step I.6 above.
 ##STR41##
 Yield=56%.
 Purification eluent: 2% ethyl acetate/98% petroleum ether.
 ##STR42##
 Yield=50%.
 Purification eluent: 2% ethyl acetate/98% petroleum ether.
 IV. Synthesis of a Trithiane-derived Mothacrylic Monomer
 ##STR43##
 PROCEDURES
 IV.1 Addition Reaction of an Electrophile to Trithiane
 5 g (36 mmol) of trithiane dissolved in 70 ml of anhydrous tetrahydrofuran
 are introduced into a three-necked flask under a nitrogen atmosphere. The
 reaction mixture is cooled to -30.degree. C., at which temperature 1.05 eq
 of nBuLi (1.6M as a solution in hexane) are added slowly. This step is
 exothermic and the reaction mixture turns yellow.
 The temperature is maintained between -25 and -15.degree. C. for two hours
 thirty minutes. After this period, the trithiane should be entirely
 dissolved. Lastly, the reaction mixture is cooled to -70.degree. C. and
 the aldehyde dissolved in tetrahydrofuran is then added dropwise by
 syringe. The reaction mixture is stirred overnight at a temperature of
 between 0 and 25.degree. C.
 Stirring is continued for a further one hour at room temperature and the
 reaction mixture is poured into an H.sub.2 O/CCl.sub.4 mixture. The
 aqueous phase is extracted three times with carbon tetrachloride. The
 organic phases are collected and the trithiane in suspension is filtered
 off. The organic phase is washed three times with water and then dried,
 filtered and concentrated under reduced pressure.
 ##STR44##
 Yield 62%.
 IV.2 Coupling of MAOC with the Trithiane Alcohol
 The procedure is the same as that in step I.6 above.
 ##STR45##
 Yield=30%.
 Purification eluent: 2% ethyl acetate/98% petroleum ether.
 V. Synthesis of Dithiane-derived Methacrylic Monomers
 ##STR46##
 ##STR47##
 PROCEDURES
 V.1 Synthesis of Dithiane
 36 ml of BF.sub.3 etherate and 72 ml of glacial acetic acid in 120 ml of
 chloroform are introduced into a three-necked flask fitted with a
 condenser, a magnetic stirrer and a dropping funnel. The reaction mixture
 is brought to reflux and the mixture: 30 ml (0.3 mol) of propanedithiol,
 29 ml of dimethoxymethane (0.33 mol) dissolved in 450 ml of chloroform, is
 then added dropwise. The addition is carried out slowly over a period of
 eight hours. The reaction mixture is allowed to return to room temperature
 and is then washed successively with four times 80 ml of water, twice 120
 ml of 10% potassium hydroxide solution and again with twice 80 ml of
 water. The organic phase is dried over sodium sulphate and filtered and
 the solvent is then evaporated off under reduced pressure.
 The solid residue is taken up in 60 ml of methanol and heated to the
 boiling point of the methanol. A hot filtration is carried out, the
 filtrate is allowed to return to room temperature and this solution is
 finally kept at -20.degree. C. overnight. The white crystals of dithiane
 are collected by filtration and dried.
 XI: 1,3-dithiane
 ##STR48##
 Yield=68%.
 Melting point=55.degree. C.
 V.2 Addition Reaction of an Electrophile to 1,3-dithiane
 5 g (41.6 mmol) of dithiane dissolved in 80 ml of anhydrous tetrahydrofuran
 are introduced into a three-necked flask under a nitrogen atmosphere.
 The reaction mixture is cooled to -40.degree. C., at which temperature 27.3
 ml (43.68 mmol, 1.05 eq) of nBuLi (1.6M as a solution in hexane) are added
 dropwise. The reaction medium is then stirred for two hours at a
 temperature of between -20 and -40.degree. C. After this period, the
 mixture is cooled to -70.degree. C. and the electrophile (aldehyde or
 epoxide) dissolved in the minimum amount of tetrahydrofuran is added
 slowly.
 In the case of an aldehyde, the reaction is instantaneous. In the case of
 an epoxide, the reaction is monitored by thin layer chromatography.
 Once the reaction is complete, the reaction mixture is hydrolysed slowly
 under cold conditions with water.
 The aqueous phase is extracted three times with ether.
 The organic phases are combined, washed three times with water and then
 with saturated sodium chloride solution.
 The organic phases are dried over sodium sulphate and the solvent is then
 evaporated off under reduced pressure.
 The product thus obtained is purified by chromatography on silica gel.
 Electrophile: Acetaldehyde
 ##STR49##
 Yield=96%.
 Purification eluent: 10% ethyl acetate/90% petroleum ether.
 Electrophile: Propionaldehyde
 ##STR50##
 Yield=98%.
 Purification eluent: 10% ethyl acetate/90% petroleum ether.
 Electrophile: Benzaldehyde
 2-(hydroxyphenylmethyl)-1,3-dithiane
 ##STR51##
 Yield=88%.
 M.p.=73.degree. C.
 Purification eluent: 12% ethyl acetate/88% petroleum ether.
 Electrophile: Cyclohexene Oxide
 ##STR52##
 Yield=93%.
 Purification eluent: 10% ethyl acetate/90% petroleum ether.
 Electrophile: Propylene Oxide
 ##STR53##
 Yield=72%.
 Purification eluent: 11% ethyl acetate/89% petroleum ether.
 V.3 Coupling of MAOC with the Alcohol
 The procedure is the same as that in step I.6 above.
 ##STR54##
 Yield=52%.
 Purification eluent: 2% ethyl acetate/98% petroleum ether.
 ##STR55##
 Yield=56%.
 Purification eluent: 3% ethyl acetate/97% petroleum ether.
 2-[.alpha.-(2-propenylcarbonyloxy)benzyl]-1,3-dithiane
 ##STR56##
 Yield=48%.
 M.p.=97.degree. C.
 Purification eluent: 5% ethyl acetate/95% petroleum ether.
 ##STR57##
 Yield=40%.
 Purification eluent: 2% ethyl acetate/98% petroleum ether.
 ##STR58##
 Yield=41%.
 Purification eluent: 3% ethyl acetate/97% petroleum ether.
 VI. Synthesis of Alkyldithiane-derived Methacrylic Monomer
 1st Synthetic Route
 ##STR59##
 2nd Synthetic Route
 ##STR60##
 VI.1 Preparation of 2-methyl-1,3-dithiane and 2-ethyl-1,3-dithiane
 5 g (46.2 mmol) of 1,3-propanedithiol and 46.2 mmol of aldehyde
 (acetaldehyde or propionaldehyde) in 60 ml of chloroform are introduced
 into a three-necked flask. This solution is stirred for one hour at a
 temperature of -20.degree. C. Next, 46.2 mmol of BF.sub.3 etherate are
 added slowly and the mixture is allowed to return to room temperature over
 fifteen hours.
 The reaction mixture is washed three times with water and then with 10%
 potassium hydroxide solution. The organic phase is dried over sodium
 sulphate, filtered and then concentrated under reduced pressure.
 XVIIa: 2-methyl-1,3-dithiane
 ##STR61##
 Yield=85%.
 Purification eluent: 3% ethyl acetate/97% petroleum ether.
 XVIIIa: 2-ethyl-1,3-dithiane
 ##STR62##
 Yield=81%.
 Purification eluent: 2% ethyl acetate/98% petroleum ether.
 VI.2 Addition of an Electrophile to the Alkyldithiane
 The procedure is the same as that in step V.2 above.
 Electrophile: Acetaldehyde
 ##STR63##
 Yield=82%.
 Purification eluent: 9% ethyl acetate/81% petroleum ether.
 Electrophile: Acetaldehyde
 ##STR64##
 Yield=78%.
 Purification eluent: 9% ethyl acetate/91% petroleum ether.
 Electrophile: Oxetane(Trimethylene Oxide)
 2-methyl-2-(3'-hydroxy-1'-propyl)-1,3-dithiane
 ##STR65##
 Yield=71%.
 Electrophile: Cyclohexene Oxide
 2-methyl-2-(2'-hydroxy-1'-cyclohexyl)-1,3-dithiane
 ##STR66##
 Yield=89%.
 VI.3 Addition of MAOC to an Alcohol
 The procedure is the same as that in step I.6 above.
 ##STR67##
 Yield=48%.
 Purification eluent: 1% ethyl acetate/99% petroleum ether.
 ##STR68##
 Yield=53%.
 Purification eluent: 4% ethyl acetate/96% petroleum ether.
 2-methyl-2-(2-propenylcarbonyloxytrimethylene)-1,3-dithiane
 ##STR69##
 Yield=71%.
 n.sub.D.sup.20 =1.5268 .nu..sub.D =39.9
 Purification eluent: 5% ethyl acetate/95% petroleum ether.
 2-methyl-2-[2-(2-propenylcarbonyloxy)cyclohexyl]-1,3-dithiane
 ##STR70##
 Yield=14%.
 n.sub.D.sup.20 =1.5425
 .nu..sub.D =41.7
 Purification eluent: 4% ethyl acetate/96% petroleum ether.
 The optical properties of the monomers synthesized above were evaluated by
 measuring their refractive index and their Abbe number. The various
 results are indicated in Table I below.
 TABLE I
 Product
 Product structural formula number n.sub.D.sup.20 v.sub.D
 ##STR71## Id 1.5509 37.0
 ##STR72## IIb 1.5960 31.6
 ##STR73## IIId 1.5215
 ##STR74## IVd 1.5462 40.1
 ##STR75## Vc 1.5447 39.5
 ##STR76## VIb 1.5923 33.9
 ##STR77## VIIc 1.5393 38.8
 ##STR78## VIIIb 1.5163 38.0
 ##STR79## IXb 1.5419 36.0
 ##STR80## Xb 1.5690 36.9
 ##STR81## XIIb 1.5330 44.2
 ##STR82## XIIIb l.5202 39.5
 ##STR83## XVb 1.5288 40.2
 ##STR84## XVIb 1.5280 40.0
 ##STR85## XVIIc 1.5300 39.2
 ##STR86## XVIIIc 1.5273 40.5
 ##STR87## XIXc 1.5268 39.9
 ##STR88## XXc 1.5425 41.7
 VII. Synthesis of 1,3-dithioacetal Derivatives from Hydroxy Ketones
 ##STR89##
 VII-1 Synthesis of Cyclic 1,3-dithioacetals by Addition Reaction of a
 Dimercaptan to a Ketone
 46.2 mmol of propanedithiol and 46.2 mmol of hydroxy ketone in 60 ml of
 chloroform are introduced into a three-necked flask. This solution is
 stirred for 1 hour at a temperature of -20.degree. C. Next, 46.2 mmol of
 boron trifluoride etherate are added slowly and the mixture is allowed to
 return to room temperature over 12 hours.
 The reaction mixture is washed three times with water and then with 10%
 potassium hydroxide solution. The organic phase is dried over sodium
 sulphate, filtered and then concentrated under reduced pressure. In the
 case of hydroxyphenyl ketones, the organic phase does not undergo any
 basic washing. The products thus obtained are purified by chromatography
 on silica gel.
 2-methyl-2-(2'-methyl-2'-hydroxy-1'-propyl)-1,3-dithiane
 ##STR90##
 Yield=98%.
 2-methyl-2-(4'-hydroxy-1'-phenyl)-1,3-dithiane
 ##STR91##
 Yield=98%.
 2-phenyl-2-(4'-hydroxy-1'-phenyl)-1,3-dithiane
 ##STR92##
 Yield=95%.
 VII-2 Synthesis of Methacrylic Esters by Coupling Methacryloyl Chloride
 with an Alcohol
 50 mmol (1 eq) of alcohol, 50 mmol (1 eq) of triethylamine and 800 ppm of
 HQME in 30 ml of chloroform are introduced into a three-necked flask
 fitted with a condenser, a thermometer and a magnetic stirrer. The
 reaction mixture is cooled to 0.degree. C.; next, 55 mmol (1.1 eq) of
 methacryloyl chloride dissolved in 20 ml of chloroform are added dropwise,
 while maintaining the temperature at 0.degree. C. After returning to room
 temperature, the mixture is left stirring for 48 hours.
 The reaction mixture is acidified with 50 ml of 6N sulphuric acid solution
 and extracted with ether. The organic phase is washed successively with
 10% sodium hydrogen carbonate solution and then with saturated sodium
 chloride solution. The ether phase is dried over sodium sulphate and the
 solvent is evaporated off. The methacrylic compounds thus obtained are
 purified by chromatography on silica gel.
 2-methyl-2-[2-methyl-2-(2-propenylcarbonyloxy)propyl]-1,3-dithiane
 ##STR93##
 Yield=32%.
 n.sub.D.sup.20 =1.5215
 .nu..sub.D =38.6
 Purification eluent: 1% ethyl acetate/99% petroleum ether.
 2-methyl-2-[4-(2-propenylcarbonyloxy)phenyl]-1,3-dithiane
 ##STR94##
 Yield=50%.
 n.sub.D.sup.20 =1.5742
 .nu..sub.D =30.8
 Purification eluent: 4% ethyl acetate/96% petroleum ether.
 2-phenyl-2-[4-(2-propenylcarbonyloxy)phenyl]-1,3-dithiane
 ##STR95##
 Yield=48%.
 m.p.=132.degree. C.
 Purification eluent: 2% ethyl acetate/98% petroleum ether.
 VIII--Synthesis of
 2-methyl-2-(2-propenylcarbonyloxymethyl)-5-methyl-1,3-benzodithiolane and
 4-methyl-4-(2-propenylcarbonyloxymethyl)-3,5-dithiatricyclo[5,2,1,0.sup.
 (2,6) ]decane
 ##STR96##
 VIII-1 Synthesis of the Alcohols
 46.2 mmol of dimercaptan and 46.2 mmol of hydroxyacetone in 60 ml of
 chloroform are introduced into a three-necked flask. This solution is
 stirred for 1 hour at a temperature of -20.degree. C. Next, 46.2 mmol of
 boron trifluoride etherate are added slowly and the mixture is allowed to
 return to room temperature over 12 hours.
 The reaction mixture is washed three times with water and then with 10%
 potassium hydroxide solution. The organic phase is dried over sodium
 sulphate, filtered and then concentrated under reduced pressure. The
 products thus obtained are purified by chromatography on silica gel.
 2-methyl-2-hydroxymethyl-5-methyl-1,3-benzodithiolane
 ##STR97##
 Yield=quantitative.
 Purification eluent: 10% ethyl acetate/90% petroleum ether.
 4-methyl-4-hydroxymethyl-3,5-dithia-tricyclo[5,2,1,0.sup.(2,6) ]decane
 ##STR98##
 Yield=67%.
 VIII-2 Synthesis of Methacrylic Esters by Coupling Methacryloyl Chloride
 with an Alcohol
 50 mmol (1 eq) of alcohol, 50 mmol (1 eq) of triethylamine and 800 ppm of
 HQME in 30 ml of chloroform are introduced into a three-necked flask
 fitted with a condenser, a thermometer and a magnetic stirrer. The
 reaction mixture is cooled to 0.degree. C.; next, 55 mmol (1 eq) of
 methacryloyl chloride dissolved in 20 ml of chloroform are added dropwise,
 while maintaining the temperature at 0.degree. C. After returning to room
 temperature, the mixture is left stirring for 48 hours.
 The reaction mixture is acidified with 50 ml of 6N sulphuric acid solution
 and is extracted with ether. The organic phase is washed successively with
 10% sodium hydrogen carbonate solution and then with saturated sodium
 chloride solution. The ether phase is dried over sodium sulphate and the
 solvent is evaporated off. The methacrylic compounds thus obtained are
 purified by chromatography on silica gel.
 2-methyl-2-(2-propenylcarbonyloxymethyl)-5-methyl-1,3-benzodithiolane
 ##STR99##
 Yield=38%.
 n.sub.D.sup.20 =1.5706
 .nu..sub.D =27.5
 Purification eluent: 1% ethyl acetate/99% petroleum ether.
 4-methyl-4-(2-propenylcarbonyloxymethyl)-3,5-dithiatricyclo[5,2,1,0.sup.
 (2,6) ]decane
 ##STR100##
 Yield=30%.
 n.sub.D.sup.20 =1.5294
 .nu..sub.D =37.6
 Purification eluent: 1% ethyl acetate/99% petroleum ether.
 IX--Synthesis of 2-[2,2-bis(2-propenylcarbonyloxy)propyl]-1,3-dithiane
 ##STR101##
 PROCEDURE
 The procedure is similar to that described above in V.2 and I.6.
 The structures of the monomers were confirmed by NMR spectrography.
 The .sup.1 H NMR spectra were recorded at 250 MHz on a Bruker AC 250
 machine. The proton-decoupled .sup.13 C NMR spectra were recorded at 62.88
 MHz on a Bruker AC 250 machine. The technique used is Spin Echo Fourier
 Transform (SEFT).
 Tetramethylsilane was used as internal reference.
 The thin layer chromatographies were carried out on silica plates
 (Kieselgel 60F.sub.254) and developed using potassium permanganate or
 iodine.
 The mass spectra were acquired on a Hewlett-Packard 5971A machine by
 electron impact (ionization voltage: 70 eV). The spectrometer is coupled
 to a gas chromatograph (capillary column of WCOT Fused Silica type,
 stationary phase: CP-Sil CB, length: 25 meters, inside diameter: 0.25 mm,
 film thickness: 0.12 .mu.m).
 The refractive indices n.sub.D.sup.20 were measured at 20.degree. C. on an
 Abbe refractometer (ASTM-NFT 60194 model) for the sodium D line (589.3
 nm).
 The Abbe numbers (.nu..sub.D) were calculated from the refractive index
 measurements at the following wavelengths: 480 nm (F' of cadmium), 546.1
 nm (E of mercury), 589.3 nm (D of sodium), 643.8 nm (C' of cadmium).
 .nu..sub.D is deduced by the formula:
EQU .nu..sub.D =(n.sub.D -1)/(n.sub.F' -n.sub.C').
 The solvents were distilled before use:
 anhydrous ether dried over Na.sub.2 SO.sub.4, distilled over sodium and
 stored over sodium.
 anhydrous tetrahydrofuran distilled over sodium in the presence of
 benzophenone and stored over sodium.
 anhydrous acetone dried over CaCl.sub.2, distilled over KMnO.sub.4, dried
 over K.sub.2 CO.sub.3 and stored over 4 .ANG. molecular sieves.
 anhydrous methylene chloride distilled over P.sub.2 O.sub.5 and stored over
 4 .ANG. molecular sieves.
 methylene chloride and ether distilled over P.sub.2 O.sub.5.
 methanol distilled over magnesium.
 The present invention also relates to novel compounds which are useful as
 intermediates for the synthesis of monomers according to the invention.
 More particularly, these novel compounds which are useful as synthetic
 intermediates are thiol compounds corresponding to the formula:
 ##STR102##
 in which R.sup.1, R.sup.2 and n.sub.1 are defined as above. Preferably,
 R.sup.1 and R.sup.2 both represent a hydrogen atom.
 Among these novel compounds, mention may be made of the compounds of
 formulae:
 ##STR103##
 The present invention also relates to polymerizable compositions containing
 at least one functional monomer of mono(thio)(meth)acrylate or
 di(meth)acrylate type, preferably mono(thio)(meth)acrylate, bearing a 5-
 to 8-membered heterocycle consisting of hydrogen, carbon and sulphur atoms
 and having at least two endocyclic sulphur atoms.
 The heterocycle which is useful in the compositions according to the
 invention is preferably 6-membered.
 Preferably also, the heterocycle of the monomer which is useful in the
 polymerizable compositions according to the invention contains two
 endocyclic sulphur atoms in positions 1-3 or 1-4 of the heterocycle.
 In another recommended embodiment of the polymerizable compositions
 according to the invention, the heterocycle of the monomer is a 6-membered
 heterocycle containing three endocyclic sulphur atoms. Also, the monomers
 of mono(thio)(meth)acrylate type which are particularly recommended for
 the polymerizable compositions according to the present invention are
 thio(meth)acrylate monomers. Lastly, these monomers preferably have a
 molar mass of between 150 and 350 and better still between 200 and 300.
 The monomers of mono(thio)(meth)acrylate type which are particularly
 recommended in the polymerizable compositions of the present invention are
 the monomers described above and represented by the formula (A), and most
 especially those for which, in formula (A), X represents a sulphur atom.
 The polymerizable compositions according to the invention can comprise only
 one functional monomer according to the invention or a mixture thereof, or
 alternatively the compositions can contain a monomer or a mixture of
 monomers according to the invention as described above, with one or more
 other common monomers which can be copolymerized with the monomers of the
 invention, for the manufacture, by polymerization, of transparent polymers
 which have suitable optical and/or ophthalmic properties.
 Any suitable comonomer which can be copolymerized with the monomers
 according to the invention can be used in the polymerizable compositions
 according to the invention.
 Among the comonomers which can be used with the monomers of
 (thio)(meth)acrylate type for the polymerizable compositions according to
 the invention, mention may be made of mono- or polyfunctional vinyl,
 acrylic and methacrylic monomers.
 Among the vinyl comonomers which are useful in the compositions of the
 present invention, mention may be made of vinyl alcohols and vinyl esters
 such as vinyl acetate and vinyl butyrate.
 The acrylic and methacrylic comonomers can be mono- or polyfunctional alkyl
 (meth)acrylate comonomers and polycyclenic or aromatic mono(meth)acrylate
 comonomers.
 Among the alkyl (meth)acrylates, mention may be made of styrene,
 .alpha.-alkylstyrenes such as .alpha.-methyl styrene, methyl
 (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl
 (meth)acrylate or difunctional derivatives such as butanediol
 dimethacrylate, or trifunctional derivatives such as trimethylolpropane
 trimethacrylate.
 Among the polycyclenic mono(meth)acrylate comonomers, mention may be made
 of cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, isobornyl
 (meth)acrylate and adamantyl (meth)acrylate.
 Comonomers which may also be mentioned are aromatic mono(meth)acrylates
 such as phenyl (meth)acrylate, benzyl (meth)acrylate, 1-naphthyl
 (meth)acrylate, fluorophenyl (meth)acrylate, chlorophenyl (meth)acrylate,
 bromophenyl (meth)acrylate, tribromophenyl (meth)acrylate, methoxyphenyl
 (meth)acrylate, cyanophenyl (meth)acrylate, biphenyl (meth)acrylate,
 bromobenzyl (meth)acrylate, tribromobenzyl (meth) acrylate,
 bromobenzylethoxy(meth)acrylate, tribromobenzylethoxy(meth)acrylate and
 phenoxyethyl (meth)acrylate.
 Among the comonomers which can be used in the compositions according to the
 invention, mention may also be made of allylcarbonates of linear or
 branched, aliphatic or aromatic, liquid polyols such as aliphatic glycol
 bis(allylcarbonates) or alkylenebis(allylcarbonates). Among the
 polyol(allylcarbonates) which can be used to prepare the transparent
 polymers which can be used in accordance with the invention, mention may
 be made of ethylene glycol bis(allylcarbonate), diethylene glycol bis
 (2-methallylcarbonate), diethylene glycol bis(allylcarbonate), ethylene
 glycol bis(2-chloroallylcarbonate), triethylene glycol
 bis(allylcarbonate), 1,3-propanediol bis(allylcarbonate), propylene glycol
 bis(2-ethylallylcarbonate), 1,3-butanediol bis(allylcarbonate),
 1,4-butanediol bis(2-bromoallylcarbonate), dipropylene glycol
 bis(allylcarbonate), trimethylene glycol bis(2-ethylallylcarbonate),
 pentamethylene glycol bis(allylcarbonate) and isopropylene bisphenol
 bis(allylcarbonate).
 The comonomers which can be used in the compositions according to the
 invention also comprise cellulose esters such as cellulose acetate,
 cellulose propionate and cellulose butyrate.
 Comonomers which can also be used are monomers of the polyalkylene glycol
 di(meth)acrylate type or aromatic di(meth)acrylate derivatives such as
 2,2-bis-4-methacryloyloxypolyethoxyphenylpropane.
 The comonomers which are useful in the present invention also comprise
 sulphur-containing compounds other than those of formula (A). These can be
 mono- or poly(meth)acrylates bearing one or more sulphur atoms or
 alternatively monothio(meth)acrylates or polythio(meth)acrylates, for
 example such as those described in patent application EP-273,710. Among
 the polythio(meth)acrylates, mention may be made of bis-2
 methacryloylthioethyl sulphide and 4,4'-bis-methacryloylthiophenyl
 sulphide.
 For an additional description of the comonomers which can be used in the
 compositions according to the invention, reference may be made to French
 patent No. 2,699,541.
 The polymerization of the polymerizable compositions according to the
 invention can be carried out by any known polymerization process. The
 polymerization process which is particularly suitable in the present
 invention is photochemical polymerization. A recommended polymerization
 process is photochemical polymerization via ultraviolet radiation and
 preferably UV-A radiation. The polymerization conditions obviously depend
 on the monomers used in the compositions.
 Such polymerization processes are described, inter alia, in patent
 FR-A-2,699,541.
 Thus, the polymerizable compositions according to the invention generally
 also contain polymerization initiators, preferably photoinitiators, in
 proportions of from 0.001 to 5% by weight relative to the total weight of
 the composition, and even more preferably from 0.01 to 1%.
 The photoinitiators which can be used in the polymerizable compositions
 according to the invention are, in particular,
 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 1-hydroxycyclohexyl phenyl
 ketone, 2,2-dimethoxy-1,2-diphenyl-1-ethanone and alkylbenzoin ethers.
 The recommended photoinitiators are 1-hydroxycyclohexyl phenyl ketone and
 2,4,6-trimethylbenzoyldiphenylphosphine oxide.
 The polymerizable compositions according to the invention can also contain
 additives used conventionally in polymerizable compositions intended for
 moulding optical and ophthalmic articles, in particular contact lenses, in
 standard proportions, namely, inhibitors, dyes, UV absorbers, fragrances,
 deodorants, antioxidants and anti-yellowing agents.
 The present invention also relates to transparent polymer compositions
 obtained by polymerization, and in particular by photo-polymerization, of
 the polymerizable compositions described above.
 The polymerization is carried out in a known manner, using an initial
 mixture containing the various monomers of the polymerizable composition
 and the optional adjuvants, the polymerization reaction being catalysable
 using catalysts such as benzoyle peroxide, cyclohexyl peroxydicarbonate,
 diisopropyl peroxydicarbonate or 2,2'-azobisbutyronitrile.
 Preferably, the polymerization is a photopolymerization and, in this case,
 the polymerizable compositions according to the invention generally
 contain photoinitiators as indicated above.
 Preferably also, this photopolymerization is a photopolymerization by
 irradiation with ultraviolet light.
 The invention also relates to optical and ophthalmic articles manufactured
 from the transparent polymer compositions according to the invention, and
 in particular contact lenses.
 The polymerizable compositions according to the invention can lead to the
 production of thermoplastic polymers. In this case, the polymerizable
 compositions are particularly suitable for obtaining optical and
 ophthalmic articles by injection-moulding (i.e. by compression, in a
 mould, of the polymerizable composition brought to a temperature above its
 glass transition temperature or to the melting point).
 However, the compositions according to the invention can be used to obtain
 optical and ophthalmic articles by any standard moulding process.
 In particular, lenses can be obtained in the final form by casting the
 polymerizable compositions between two moulds having the required surface
 geometry, followed by polymerization. A lens whose two faces are in their
 final state is thus obtained. Semi-finished lenses can also be
 manufactured having, after moulding, only one face in its final geometry,
 it being possible for the second face then to be surfaced as required.
 EXAMPLE OF PREATION OF THE TRANSENT POLYMER ACCORDING TO THE
 INVENTION
 The monomer is prepared in the absence of ultraviolet light.
 An initiator is added to the monomer in a proportion of 0.1% by weight.
 This solution is then injected into the polymerization mould.
 Polymerization is then carried out by ultraviolet radiation.
 Monitoring of the polymerization kinetics is carried out using a
 near-infrared spectrometer which makes it possible to observe the
 disappearance of the acrylic C.dbd.C peak at 6200 cm.sup.-1 for the
 methacrylic esters and at about 6140 cm.sup.-1 for the methacrylic
 thioesters.
 Homopolymerization of the methacrylic ester of 1,4-dithiacycloheptane could
 be achieved under good conditions, and the characteristics of the monomer
 and of the polymer are given below.
 MONOMER: Methacrylic Ester of 1,4-dithiacycloheptane
 ##STR104##
 Properties:
 n.sub.D.sup.20 =1.5447
 Abbe n.sup.b =39.5
 transparent liquid stabilized with bis-di-tert-butylhydroxytoluene
 Homopolymerization in the presence of 0.1% initiator.
 Near-infrared monitoring of kinetics.