PHOTOCATALYTIC AEROBIC OXIDATION OF YPERITE OR AN ANALOG THEREOF

Abstract

The present invention relates to method for converting a sulfide of the following formula (I), such as yperite: R.sup.1SR.sup.2 (I) wherein R.sup.1 and R.sup.2, identical or different, are a (C.sub.1-C.sub.3)alkyl, (C.sub.2-C.sub.3)alkenyl, aryl, aryl-(C.sub.1-C.sub.3)alkyl, or aryl-(C.sub.2-C.sub.3)alkenyl group, said group being optionally substituted by one or several groups selected from a halogen atom, OR.sup.3, and NR.sup.4R.sup.5, and R.sup.3, R.sup.4, and R.sup.5 are, independently of one another, H or a (C.sub.1-C.sub.3)alkyl; into a sulfoxide of the following formula (II): R.sup.1SOR.sup.2 (II) wherein R.sup.1 and R.sup.2, are as defined above, wherein said method comprises oxidizing the sulfide of formula (I) in the presence of a catalyst. under an atmosphere comprising dioxygen, and under white or blue light irradiation, wherein the catalyst has the following formula (I): wherein Ar.sup.1, Ar.sup.2, Ar.sup.3, and Ar.sup.4 are, independently of one another, an aryl group optionally substituted by one or several groups selected from halogen, a (C.sub.1-C.sub.3)alkyl, OR.sup.6, and NR.sup.7R.sup.8, and R.sup.6, R.sup.7, and R.sup.8 are, independently of one another, H or a (C.sub.1-C.sub.3)alkyl. The present invention relates also to an air-filtering device comprising a catalyst of formula (I).

##STR00001##

Claims

1. A method for converting a sulfide of following formula (I):
R.sup.1SR.sup.2(I) into a sulfoxide of following formula (II):
R.sup.1SOR.sup.2(II) wherein R.sup.1 and R.sup.2, identical or different, are a (C.sub.1-C.sub.3)alkyl, (C.sub.2-C.sub.3)alkenyl, aryl, aryl-(C.sub.1-C.sub.3)alkyl, or aryl-(C.sub.2-C.sub.3)alkenyl group, which is optionally substituted by one or several groups selected from the group consisting in a halogen atom, OR.sup.3, and NR.sup.4R.sup.5, and R.sup.3, R.sup.4, and R.sup.5 are, independently of one another, H or a (C.sub.1-C.sub.3)alkyl; wherein the method comprises oxidizing the sulfide of formula (I) in the presence of a catalyst, under an atmosphere comprising dioxygen, and under white or blue light irradiation, wherein oxidizing is performed in air used as the atmosphere comprising dioxygen, wherein the catalyst has following formula (III): ##STR00014## wherein Ar.sup.1, Ar.sup.2, Ar.sup.3, and Ar.sup.4 are, independently of one another, an aryl group optionally substituted by one or several groups selected from the group consisting in halogen, a (C.sub.1-C.sub.3)alkyl, OR.sup.6, and NR.sup.7R.sup.8, and R.sup.6, R.sup.7, and R.sup.8 are, independently of one another, H or a (C.sub.1-C.sub.3)alkyl.

2. The method according to claim 1, wherein the sulfide is a sulfide of formula (I), wherein R.sup.1 and R.sup.2, identical or different, are a (C.sub.1-C.sub.3)alkyl, (C.sub.2-C.sub.3)alkenyl, or aryl group, which is optionally substituted by one or several groups selected from the group consisting in a halogen atom, OR.sup.3, and NR.sup.4R.sup.5.

3. The method according to claim 2, wherein the sulfide is a sulfide of formula (I), wherein R.sup.1 and R.sup.2, identical or different, are a (C.sub.1-C.sub.3)alkyl group optionally substituted by one group selected from the group consisting in a halogen atom, OR.sup.3, and NR.sup.4R.sup.5.

4. The method according to claim 3, wherein the sulfide is yperite.

5. The method according to claim 1, wherein Ar.sup.1, Ar.sup.2, Ar.sup.3, and Ar.sup.4 are, independently of one another, an aryl optionally substituted by one or several (C.sub.1-C.sub.3)alkyl.

6. The method according to claim 5, wherein the catalyst is meso-tetraphenylporphyrin (TPP).

7. The method according to claim 1, wherein the catalyst is used in an amount from 0.01 mol % to 10 mol % relatively to the molar amount of the sulfide.

8. The method according to claim 1, wherein the white or blue light irradiation is a sunlight irradiation or an irradiation from a white or blue light-emitting diode (LED).

9. The method according to claim 1, wherein the white or blue light irradiation is a white light irradiation.

10. The method according to claim 1, wherein the oxidizing step is performed in an aerosol or gas phase.

11. The method according to claim 10, wherein the catalyst is deposited on a substrate.

12. The method according to claim 1, wherein the catalyst is recovered at the end of the oxidizing step, and re-used in another oxidizing step.

13. The method according to claim 1, being performed in a continuous manner.

14. An air-filtering device comprising a filtering membrane impregnated with a catalyst, wherein the filtering membrane is made of cellulose, polytetrafluoroethylene, polyurethane, polyimide, polysulfone or a mixture thereof, and the catalyst has following formula (I): ##STR00015## wherein Ar.sup.1, Ar.sup.2, Ar.sup.3, and Ar.sup.4 are, independently of one another, an aryl group optionally substituted by one or several groups selected from the group consisting in halogen, a (C.sub.1-C.sub.3)alkyl, OR.sup.6, and NR.sup.7R.sup.8, and R.sup.6, R.sup.7, and R.sup.8 are, independently of one another, H or a (C.sub.1-C.sub.3)alkyl.

15. The air-filtering device according to claim 14, wherein the catalyst is meso-tetraphenylporphyrin (TPP).

16. The method according to claim 3, wherein R.sup.1 and R.sup.2, identical or different, are a (C.sub.1-C.sub.3)alkyl group optionally substituted by one group selected from the group consisting in a halogen atom, OH, and NH.sub.2.

17. The method according to claim 3, wherein R.sup.1 and R.sup.2, identical or different, are a (C.sub.1-C.sub.3)alkyl group optionally substituted by one group selected from the group consisting in Cl and OH.

18. The method according to claim 1, wherein Ar.sup.1, Ar.sup.2, Ar.sup.3, and Ar.sup.4 are, independently of one another, a phenyl optionally substituted by one (C.sub.1-C.sub.3)alkyl.

19. The method according to claim 1, wherein the catalyst is used in an amount from 0.1 mol % to 1 mol % relatively to the molar amount of the sulfide.

Description

FIGURES

[0059] FIG. 1: Experimental setup used for the photocatalytic oxidation of sulfides such as CEES in the aerosol/gas phase.

[0060] FIG. 2: Temperature monitoring inside the round-bottom flask (without sulfide/photocatalyst) for the aerosol/gas phase oxidation setup: the white LED is switched ON at t=0 min and switched OFF at t=60 min. A thermometer was inserted in the flask and the temperature was read at constant interval.

[0061] FIG. 3: .sup.1H-NMR spectra alignment for pure CEES, CEESO, CEESO.sub.2 and the reaction mixture recovered after aerosol/gas-phase photocatalytic oxidation of CEES by TPP and under an air atmosphere, for 1 h.

[0062] FIG. 4: Histograms representing the percentage of conversion (dark grey) and the percentage of selectivity to sulfoxide (light grey) for successive CEES oxidation experiments in the aerosol/gas-phase re-using the same piece of paper embedded with the TPP photocatalyst (0.1 mol %). Experiments were performed in triplicate and the error bars represent the standard deviation.

[0063] FIG. 5: Photograph of the filtration device simulator used in example 3.

EXAMPLES

Abbreviations

[0064] BBS: di-n-butylsulfide [0065] CEES: 2-chloroethylethylsulfide [0066] CEPS: chloroethylphenylsulfide [0067] EES: diethylsulfide [0068] HEES: 2-hydroxyethylethylsulfide [0069] GC: gas chromatography [0070] MPS: methylphenylsulfide [0071] NMR: nuclear magnetic resonance [0072] TBTBS: di-tert-butylsulfide [0073] TPP: meso-tetraphenylporphyrin [0074] VES: vinylethylsulfide [0075] VPS: vinylphenylsulfide

1. Photocatalytic Oxidation in the Aerosol/Gas Phase

1.1. Photocatalytic Aerobic Oxidation of CEES

[0076] CEES was chosen as a model sulfide, i.e. as a simulant of sulfur mustard. A typical procedure is given below, the experimental setup being presented on FIG. 1. TPP (photocatalyst) (100 L of a 2 mM solution, 0.2 mol) in CHCl.sub.3 is deposited on a filter paper (15 cm) and allowed to dry for 2 min. The filter paper embedded with the TPP photocatalyst (1) is then connected to a hook (2) attached to the inner portion of a rubber septum (3). Neat 2-chloroethylethylsulfide (4) (23.5 L, 200 mol) is introduced in a 25 mL round-bottom flask (5) (filled with air) which is closed with the rubber septum (connected to the paper-supported TPP). The vertical position of the paper is adjusted in order to stand 1 cm from the bottom of the round-bottom flask. The flask is positioned in a beaker (6) (7 cm diameter) fitted with white LED wires (7). The reaction is initiated by switching the LED wire ON, and it is then stopped by switching it OFF after the specified reaction time (1 h unless otherwise specified). The LEDs here serve a dual purpose, photoexcitation of TPP and gentle heating source to help vaporize CEES in the gas phase or at least convert it into an aerosol phase (FIG. 2) (if a higher temperature is needed, an additional heat source can be used). After cooling down for 5 min, the filter paper is removed and the flask and filter paper are washed with CDCl.sub.3, transferred to a tinted NMR tube, and analyzed by .sup.1H-NMR and by GC. Conversion is determined from NMR analysis of the crude mixture by comparison with the NMR analysis of authentic CEES, CEESO and CEESO.sub.2 samples (FIG. 3). For absolute quantification, a solution of dioxane (20 L, 1 M) was added to the NMR tube to serve as an internal standard.

[0077] Experiments under N.sub.2 and O.sub.2 atmosphere were run by pre-purging the round-bottom flask with the suitable gas for 5 min.

[0078] The results obtained are presented in Table 1 below.

TABLE-US-00001 TABLE 1 Photocatalytic aerobic oxidation of CEES [00004] TPP Entry (mol %) Atmosphere Light Conversion (%) Selectivity (%) 1 0.1 air white LED 100 92 2 0 air white LED 0 3 0.1 air dark 0 4 0.01 air white LED 76 87 5 1 air white LED 100 79 6 0.1 N.sub.2 white LED <5 86 7 0.1 O.sub.2 white LED 100 38 8.sup.(a) 0.1 air sunlight 100 84 .sup.(a)7 h of reaction time under a mid-winter sun on a partly cloudy day

[0079] Under the conditions of the above-mentioned protocol (Entry 1), the starting CEES material was fully converted in 1 h for the most part into CEESO (expected first oxidation product, 90%), together with some minor CEESO.sub.2 (over-oxidation product, 8%), and vinyl derivatives (B-elimination products, <2%).

[0080] Reactions run with either no TPP-catalyst (Entry 2) or in the dark (Entry 3) led to no conversion confirming that the oxidation reaction is photocatalyzed by TPP. The aerobic nature of the transformation was evidenced by running the photocatalytic reaction under an inert nitrogen atmosphere (Entry 6), which failed to provide the expected compound in satisfactory yield (<5%), while the reaction run under pure oxygen (Entry 7) mostly afforded the over-oxidized sulfone product.

[0081] Moreover, the process can be performed with higher or lower amounts of TPP (Entries 4-5) and with sunlight as irradiation source (Entry 8).

[0082] Other photocatalysts were tested under similar conditions (200 mol CEES, 0.1 mol % photocatalyst) as reported above, except for the phthalocyanine photocatalyst which was deposited as a 1 mM suspension in CHCl.sub.3 (due to solubility issues). No conversion was detected for phthalocyanin and (meso-tetraphenylporphyrin) iron(III), whereas a low 4% yield was obtained with (meso-tetraphenylporphyrin) zinc(II).

1.2. Photocatalytic Aerobic Oxidation of Various Sulfides

[0083] Other sulfides were also tested under similar conditions (200 mol sulfide, 0.1 mol % TPP) as reported above. Reaction times were adjusted to get optimal conversion and selectivity.

[0084] The results obtained are presented in Table 2 below.

TABLE-US-00002 TABLE 2 Photocatalytic aerobic oxidation of different sulfides [00005] Conversion Entry Sulfide Time (h) (%) Selectivity (%) 1 CEES [00006] 1 100 92 2 HEES [00007] 8 97 88 3 BBS [00008] 2 100 43 4 TBTBS [00009] 8 88 0 5 EES [00010] 8 89 71 6 VES [00011] 2 95 67 7 8.sup.(a) CEPS [00012] 8 3 18 98 55 87 9 MPS [00013] 3 92 72 .sup.(a)Sulfide deposited directly on the paper support.

[0085] The oxidation of HEES is complete after 8 h, which is consistent with the hydrogen bonding effect of the alcoholic group, imparting lower vapor pressure to the sulfide. Alkyl-substituted sulfides are in general more prone to over-oxidation due to the electron-donating effect of the alkyl substituents that increases the electron density of the central sulfur atom (Entries 3-4). Less electron-rich sulfides such as EES (Entry 5) and VES (Entry 6) were converted to their sulfoxide counterparts with better selectivities than those observed for butyl-substituted compounds BBS and TBTBS. Concerning aromatic sulfides, the high boiling point of CEPS (245 C.) is responsible for the mediocre reactivity/selectivity observed (Entry 7) as confirmed by the fact that the deposition of CEPS directly on the paper support affords 98% conversion with 87% selectivity (Entry 8). Besides, MPS, which has a lower boiling point (188 C.), was efficiently oxidized into the corresponding sulfoxide with a selectivity of 72% and 92% conversion (Entry 9). These results confirm that aromatic sulfides can also react satisfactorily.

1.3. Catalyst Recycling

[0086] Successive CEES oxidation experiments have been performed in the aerosol/gas phase according to the above-mentioned procedure by recovering and re-using the same piece of filter paper embedded with the TPP photocatalyst (0.1 mol %) with a fresh batch of CEES. The experiments were performed in triplicate.

[0087] The results obtained in terms of percentage of conversion of CEES and percentage of selectivity to CEESO are presented in FIG. 4. During the first five cycles, the conversion at 1 h reaction was nearly quantitative (>98%), but gradually decreased to reach 83% after the tenth assay, although selectivity remained nearly constant (85-91%) showing that the TPP catalyst remained fully photoactive.

2. Photocatalytic Oxidation in the Liquid Phase

[0088] A typical procedure is given below for the oxidation of CEES.

[0089] TPP (100 L of a 2 mM solution in CDCl.sub.3, 0.2 mol) is added to a 25 mL round-bottom flask containing 900 L CD.sub.3OD and filled with air. CEES (23.5 L, 200 mol) is then added and the flask is closed with a rubber septum. The flask is positioned in a beaker and illuminated with white LEDs for 1 h as done for the experimentation in an aerosol/gas phase. The product distributions are analyzed directly by .sup.1H-NMR. For absolute quantification, a solution of dioxane (20 L, 1 M) was added to the NMR tube to serve as an internal standard.

[0090] Such a procedure allows the complete conversion of CEES with a selectivity to sulfoxide of 97%.

3. Photocatalytic Oxidation in a Filtration Device Simulator

[0091] A filtration device simulator has been used to perform a photocatalytic oxidation. A photograph of the experimental setup is presented on FIG. 5. This simulator comprises: [0092] a first compartment (1) which is a source compartment containing the sulfide to be oxidized (Et-S-(CH.sub.2).sub.2Cl), [0093] a second compartment (3) which is a collecting compartment, and. [0094] a filtering membrane (2) (filter paper) impregnated with the catalyst (TPP) (for that, the filter paper has been impregnated with a solution of TPP in chloroform before leaving it to dry) which separates the first and second compartments (1) and (3).

[0095] The device has been exposed to blue light irradiation.

[0096] The only product identified in the collecting compartment corresponds to the oxidized form of the sulfide comprised in the source compartment, i.e. the sulfoxide Et-S(O)(CH.sub.2).sub.2Cl.

REFERENCES

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