三氟硫代甲基化试剂

A new synthesis of tri¯uoromethanethiolatesÐcharacterization
and properties of tetramethylammonium,cesium and di(benzo-15-crown-5)cesium tri¯uoromethanethiolates
Wieland Tyrra a,*,Dieter Naumann a ,Berthold Hoge a ,
Yurii L.Yagupolskii b
a
Institut fu Èr Anorganische Chemie,Universita Èt zu Ko Èln,Greinstrasse 6,D-50939Cologne,Germany b
Institute of Organic Chemistry of the National Academy of Sciences of Ukraine,
Murmanskaya 5,UA-02094Kiev,Ukraine
Received 9September 2002;received in revised form 14October 2002;accepted 16October 2002
Dedicated to Professor Ru
Èdiger Mews on the occasion of his 60th birthday.Abstract
[NMe 4]SCF 3,CsSCF 3and [(B-15-C-5)2Cs]SCF 3(B-15-C-5:benzo-15-crown-5)are formed from reactions of the corresponding ¯uorides,
trimethyl(tri¯uoromethyl)silane,Me 3SiCF 3,and elemental sulfur in glyme or THF.All compounds are colorless to pale ochre solids decomposing signi®cantly above ambient temperature.Excellent agreement between experimental and theoretical vibrational frequencies,calculated at the B3PW91level of theory,impressively con®rms the salt-like nature of [NMe 4]SCF 3.
The properties of the title compounds as nucleophilic SCF 3transfer reagents were checked with a variety of organic,organometallic and inorganic compounds.
#2002Elsevier Science B.V .All rights reserved.
Keywords:Tri¯uoromethanethiolate;Synthesis;Properties
1.Introduction
Organic SCF 3groups containing compounds are of sig-ni®cant interest for pharmaceutical and agrochemical pur-poses [1].However,the number of easily accessible reagents suitable for nucleophilic introductions of SCF 3groups into organic,organometallic and inorganic compounds is limited so far.AgSCF 3[2]and Hg(SCF 3)2[3]are available from reactions of the metal ¯uorides and CS 2in moderate to good yields.Both compounds as well as CuSCF 3are most com-monly used as nucleophilic SCF 3transfer reagents espe-cially for aromatic systems [4±7].
Several other MSCF 3derivatives (M K,Cs,NMe 4,S(NMe 2)3,TDAE)have been described in the literature [8±13].Most of the preparative pathways are multi-step reac-tions or proceed under inconvenient conditions using highly toxic materials such as C(S)F 2or CF 3SSCF 3[14].With the
exception of [S(NMe 2)3]SCF 3[13]and (TDAE)[SCF 3]2[8]all other compounds are described to be unstable at ambient temperature.
Herein,a new,convenient one-pot procedure for the pre-paration of [NMe 4]SCF 3,CsSCF 3and [(B-15-C-5)2Cs]SCF 3is presented having the great advantage that neither highly toxic nor very expensive reagents are involved.The com-pounds are thermally stable and can widely be used as nucleophilic SCF 3transfer reagents in halide substitutions in organic,element organic and inorganic systems.2.Results and discussion
2.1.Syntheses and characterizations of [NMe 4]SCF 3,CsSCF 3and [(B-15-C-5)2Cs]SCF 3
In a similar manner as penta¯uorothiophenol has been prepared from reactions of penta¯uorophenyl lithium [15]or magnesium [15,16]reagents in the presence of elemental sulfur,cesium and tetramethylammonium
tri¯uorometha-
Journal of Fluorine Chemistry 119(2003)101±107
*
Corresponding author.Tel.: 49-221-470-3276;fax: 49-221-470-3276.
E-mail address:tyrra@uni-koeln.de (W.Tyrra).
0022-1139/02/$±see front matter #2002Elsevier Science B.V .All rights reserved.PII:S 0022-1139(02)00276-2
nethiolates,CsSCF 3and [NMe 4]SCF 3,are prepared from Me 3SiCF 3,elemental sulfur and the corresponding ¯uorides in glyme or THF (Eq.(1))indicating a close relation between these systems and Grignard reagents.
All tri¯uoromethanethiolates precipitate as colorless solids from the ether solutions in good yields.S(CF 3)2and minor amounts of CF 3H are detected as by-products in the mother liquors.Thermal instability as reported for [NMe 4]SCF 3[11,12]and CsSCF 3[9]was not observed if the compounds were prepared by the method presented.By-product formation as reported for the reactions of alkali metal ¯uorides and C(S)F 2[11,17]was not monitored by means of 19F NMR spectroscopy in any case:Me 3SiCF 3 18S 8 MF
3glyme or THF À60to r :t :=16h
MSCF 3 Me 3SiF (1)
where M [NMe 4],Cs,[(B-15-C-5)2Cs].
After disposing of the liquid and drying in vacuo,color-less to tan,sometimes metallic looking solids are obtained which are identi®ed as mixtures of MSCF 3and elemental sulfur when the latter was used in excess.After extraction of sulfur with diethyl ether or better carbon disul®de in a Soxhlet apparatus and drying in vacuo,white to tan powders were obtained which could be handled at least for a short time in ambient atmosphere.When the reaction is started at room temperature,S(CF 3)2is the major product,while only minor amounts of MSCF 3are formed.
The 19F NMR chemical shifts of CsSCF 3and [NMe 4]SCF 3are in good agreement with those reported for [S(NMe 2)3]SCF 3(d À6.53ppm (CD 3CN)[13])and (TDAE)2 [SCF 3À]2(d À7.8ppm (CD 3CN)[8]).CsSCF 3is suf®ciently soluble in CD 3CN showing a broad 19F NMR signal at d À8.0ppm (W 1=2%500Hz).The line-width might arise from rapid exchange processes in solution.Addition of at least a two-fold excess of 18-crown-6led to a decrease in line-width to approximately 2Hz and allowed the detection of 13C satellites (1J F ;C 293:1Æ0:8Hz);the resonance of [SCF 3]Àis shifted
to d À6.2ppm.The absolute value of the 1J F ;C coupling constant is signi®cantly lower than those of organo(tri¯uor-omethyl)sulfanes (1J F ;C %304Æ3Hz,cf.MeSCF 3described below),bis(tri¯uoromethyl)sulfane [18]and -disulfane [18]and also signi®cantly lower than those of s -bonded metal SCF 3derivatives such as CuSCF 3,AgSCF 3and Hg(SCF 3)2(cf.Section 4.2).In the 13C NMR spectra,the signal of [SCF 3]Àis detected at d 145.45ppm (1J F ;C 292:5Æ0:8Hz)and shifted by approximately 15±20ppm down®eld from signals of covalent bonded organo-SCF 3derivatives.19F and 13C NMR data of CsSCF 3(after addition of 18-crown-6),[(B-15-C-5)2Cs]SCF 3and [NMe 4]SCF 3are nearly identical indicating dissociation in solution.Similar results were obtained in NMR experiments in DMF-d 7solutions.
The electron impact mass spectrum of CsSCF 3(20eV ,1008C)is dominated by the ion [CF 2S] (m =e 82)accompanied by [CFS] (m =e 63)indicating a decay into CsF and C(S)F 2.In the mass spectrum of [(B-15-C-5)2Cs]SCF 3,only the peak of the crown ether is detected.Mass spectra of [NMe 4]SCF 3(20eV)imply a slow decay into [NMe 4]F and C(S)F 2at temperatures below 1308C.At ca.1508C the ions of [MeSCF 3] (m =e 116),[NMe 3] (m =e 59),[Me 2NCH 2] (m =e 58),and [MeF] (m =e 34)dominate the spectra besides that of [CF 2S] .Therefore,a parallel decomposition as indicated in Scheme 1has to be assumed.It should be noted that the decomposition point of [NMe 4]F is 1758C [19].
CsSCF 3,[(B-15-C-5)2Cs]SCF 3,and [NMe 4]SCF 3are room temperature stable colorless solids which can be stored under dry nitrogen or argon for at least several months without decomposition.
Thermal stabilities are comparable with those of [S(NMe 2)3]SCF 3(166±1698C [13])and (TDAE)2 [SCF 3]2À(136±1378C [8]).The onset of decomposition is indicated by gas evolution starting at ca.1588C for the cesium derivative and ca.2108C for the tetramethylammonium compound,while [(B-15-C-5)2Cs]SCF 3melts at 61±638C
without
Scheme 1.EI mass spectrometric decay of [NMe 4]SCF 3(20eV).
102W.Tyrra et al./Journal of Fluorine Chemistry 119(2003)101±107
decomposition.Visible decomposition points were determined in both,one-end open glass capillaries and sealed 4mm glass tubes.After the decomposition process,the 4mm glass tubes were cooled to À1968C,opened and EtCN was poured onto the frozen residue.While NMR spectroscopic analysis of the decomposition products of CsSCF 3did not exhibit any sig-ni®cant signals of ¯uorine containing compounds (traces of CF 3H),thermal decomposition of [NMe 4]SCF 3led to products which were identi®ed as MeSCF 3(d (19F) À44.1ppm,q,1
J F ;C 303:6Æ0:2Hz,4J F ;H 0:6Æ0:2Hz;d (1H) 2.56ppm,q,4J F ;H 0:6Æ0:2Hz,cf.[20,21]),MeF (d (19F) À268.0ppm,q,2J F ;H 45:8Æ1:5Hz;d (1H) 4.20ppm,d,2J F ;H 46:2Æ0:5Hz,cf.[22])and NMe 3(d (1H) 2.23ppm,s)supporting a similar thermal decay as under mass spectrometric conditions.Evidence for C(S)F 2or its consecutive products was not supported by NMR spectroscopic methods.
The optimization of the SCF 3Àanion structure was per-formed with the Gaussian 98program package [23]on the hybrid density level B3PW91/6-311G(3d)yielding a struc-ture of C 3v symmetry (Fig.1)whereby the calculated geometric parameters are in good agreement with experi-mental data of crystalline (TDAE)[SCF 3]2[8].
The reliability of the hybrid density model B3PW91in structural and vibrational predictions was proven earlier on per¯uoroorganyl phosphorus and sulfur derivatives [24].The calculated vibrational frequencies of the SCF 3Àanion are in excellent agreement with the experimental frequen-cies of the SCF 3Àanion in the [NMe 4]salt (Table 1).As to be expected,the CF valence modes of the SCF 3Àanion are
shifted to lower frequencies compared to neutral tri¯uor-omethyl sulfur derivatives,caused by negative hyperconju-gation,as already discussed for the OCF 3Àanion [25].Vibrational frequencies of the cation [NMe 4] correspond well with literature data [19,26].2.2.Nucleophilic substitutions
The properties of CsSCF 3and [NMe 4]SCF 3as sources of nucleophilic [SCF 3]Àwere studied with a variety of organic substrates (Scheme 2)(also see [27,28]).
While halide substitution reactions occurred immediately and selectively with activated substrates at ambient tem-perature as indicated in Scheme 2,vinyl iodide,iodoben-zene,2-bromothiophene and 1-bromo-2-¯uorobenzene remained unaffected under these mild conditions.The sub-strates obtained were identi®ed by comparison with pub-lished 19F NMR data as indicated.
Reactions with organometallic and inorganic compounds (Scheme 3)yielded the expected SCF 3derivatives.
While Hg(SCF 3)2[29],CuSCF 3,AgSCF 3and PhHgSCF 3are formed selectively and quantitatively,reactions with Me 3SiCl give NMR spectroscopic evidence for Me 3SiSCF 3as the major product directly after mixing solutions of MSCF 3and Me 3SiCl at À308C.Me 3SiSCF 3[30]is unstable under the conditions chosen (À308C to ambient tempera-ture)and as a consequence 19F NMR spectroscopic evidence is found for the consecutive products.19F NMR spectra of reaction mixtures of [NMe 4]SCF 3and Me 3SiCl in EtCN are nearly identical with those published for the reaction of AgSCF 3and Me 3SiI in pyridine [30].
Room temperature reactions of [NMe 4]SCF 3and CsSCF 3with elemental iodine or iodine monochloride may be used as a new and convenient approach to bis(tri¯uoromethyl)-disulfane,CF 3SSCF 3[18,33].Room temperature unstable CF 3SI [31,32]is proposed to be the intermediate in these reactions which decomposes into the disulfane and elemen-tal iodine.
Reactions of MSCF 3and Cu(OC(O)Me)2were expected to proceed via the intermediate ``Cu II (SCF 3)(OC(O)Me)''which should readily decompose into Cu I OC(O)Me with concomitant formation of CF 3S radicals in analogy to reactions described in [34].However,the products exclu-sively detected in the 19F NMR spectra were MeC(O)F
and
Fig.1.Geometry of the SCF 3Àion at the B3PW91/6-311G(3d)level of theory.
Table 1
Calculated (B3PW91/6-311G(3d))vibrational frequencies and observed infrared and Raman bands of SCF 3ÀPoint group C 3v IR
Ra
SCF 3À(calculated)
[IR]
(Ra)
Assignments Approximate mode description n 1(A 1)n s (CF 3)1053vs 1050(91)1055.410047n 4(E)n as (CF 3)983s
985(31)975.86329n 2(A 1)d s (CF 3)737(100)732.80100n 5(E)d as (CF 3)533(22)530.4016n 3(A 1)n (CS)494(83)488.9047n 6(E)
d (SCF)
344
(43)
338.7
34
W.Tyrra et al./Journal of Fluorine Chemistry 119(2003)101±107103
F À.With the knowledge that the SCF 3anion can be attacked by nucleophiles such as azolyl groups [35],the exclusive formation of one ¯uoroorgano compound,MeC(O)F,impli-cates a reaction as outlined in Scheme 4.19
F NMR spectroscopic investigations on the reaction of NaOC(O)Me and [NMe 4]SCF 3in DMF gave identical results.The hydrolysis of MSCF 3(M [NMe 4],Cs)was studied by NMR spectroscopic and chemical means.Hydrolyses of solid samples of [NMe 4]SCF 3and CsSCF 3with water or
addition of water to DMF solutions of both compounds gave 19
F NMR spectroscopic evidence for F Àand [HF 2]À[36].After 16h,19F NMR spectra showed exclusively broad signals in the region between À125and À180ppm.On the other hand,CO 2and H 2S were unambiguously qualita-tively identi®ed.Thus,a hydrolysis process as described below might be assumed (Eq.(2)).
SCF 3À 2H 2O 3CO 2 H 2S `` H 2F 3À ''
(2)
Scheme 2.Nucleophilic trifluorothiomethylation of selected organic substrates (M [NMe 4],Cs;solvents:MeCN or EtCN;room
temperature).
Scheme 3.Nucleophilic trifluorothiomethylation of inorganic and organometallic compounds (M [NMe 4],Cs;solvents:MeCN or EtCN;room temperature).
104W.Tyrra et al./Journal of Fluorine Chemistry 119(2003)101±107
3.Conclusion
We have demonstrated the utility of Me 3SiCF 3as a commercially available and widely used compound for the synthesis of MSCF 3with avoidance of toxic materials.The derivatives prepared exhibit a great synthetic potential in organic,organometallic and inorganic syntheses in reac-tions with substances forming stable elemental sulfur s -bonds.
4.Experimental
Schlenk techniques were used throughout all manipula-tions.NMR spectra were recorded on a Bruker AC 200spectrometer operating at 200.1MHz (1H).External stan-dards were used in all cases (1H,13C:Me 4Si;19F:CCl 3F).Acetone-D 6was used as an external lock (5mm tube)in reaction control measurements while an original sample of the reaction mixture was measured in a 4mm insert.Mass spectra were run on a Finnigan MAT 95spectro-meter using the electron impact method (20eV).Inten-sities are referenced to the most intensive peak of a group.Visible decomposition points were determined using the apparatus HWS Mainz 2000.CHN analyses were carried out with a Heraeus CHN Rapid apparatus.IR spectra of [NMe 4]SCF 3were recorded on a Nicolet 5PC FT-IR spectrometer as KBr pellets.Raman spectra were run on a Bruker FRA-106/S spectrometer,with a Nd:YAG laser operating at l 1064nm.The program,Gaussian 98,was used for the structure and frequency calculations [23].
[NMe 4]F was purchased from ABCR as the tetrahydrate and used after careful dehydration [19];CsF was purchased from ABCR and used after drying for several hours at 4008C and a pressure of 0.005Torr.Solvents (P.A.quality),Me 3SiCF 3(ABCR)as well as all deriva-tives used for checking the reactivity were used as received.
4.1.Syntheses of CsSCF 3and [NMe 4]SCF 3
Typical procedure :0.16g (5.0mmol)elemental sulfur was dissolved in 40ml glyme or THF at ambient tempera-ture.An amount of 0.90ml (6.0mmol)Me 3SiCF 3was added and the reaction mixture was cooled to À608C.An amount of 0.47g (5.0mmol)[NMe 4]F was added in one portion.Directly after addition,the color of the reaction mixture changed from pale lemon to intensive orange to become pale yellow.The intensively stirred mixture was kept at À608C for ca.30min and then allowed to warm to room temperature overnight.Turbid pale yellow to some-times brown-orange suspensions were obtained from which [NMe 4]SCF 3precipitated as a colorless to tan solid.19F NMR spectra of the solutions exhibited the signals of S(CF 3)2,CF 3H and Me 3SiF.The solution was disposed,the remaining solid was washed with few carbondisul®de and dried in vacuo to give 0.77g [NMe 4]SCF 3(88%yield).Yields of CsSCF 3prepared in the same manner were signi®cantly lower and still impured by CsF.
When sulfur was used in excess,the vacuum-dried solids were extracted overnight with diethyl ether or carbon dis-ul®de in a Soxhlet apparatus.
While CsSCF 3was only obtained as a colorless powder,[NMe 4]SCF 3crystallizes in colorless needles from saturated MeCN solutions at 08C.Both compounds are moisture sensitive.
Tetramethylammonium tri¯uoromethanethiolate,[NMe 4]-SCF 3:Colorless needles:mp (sintering)153,%194,2108C (dec.).19
F NMR (188.3MHz,CD 3CN):d À6.49ppm (s,1
J F ;C 292:7Hz,W 1=2 4:6Hz);(DMF-d 7)À5.20ppm (s,1J F ;C 293:7Hz,W 1=2 2:2Hz).1
H NMR (200.1MHz,CD 3CN):d 3.14ppm (s);(DMF-d 7)3.41ppm (s).13
C NMR (50.3MHz,C
D 3CN):d 145.2ppm (q,1
J F ;C 293:3Hz,SCF 3),56.0ppm (qm,1J F ;C 142:9Hz,N(CH 3)4);(DMF-d 7)145.3ppm (q,1J F ;C 293:3Hz,SCF 3),55.2ppm (qm,1J F ;C 143:7Hz,N(CH 3)4
).
Scheme 4.Possible reaction sequence for the formation of MeC(O)F from the reaction of Cu(OC(O)Me)2and MSCF 3(M Cs,[NMe 4]).
W.Tyrra et al./Journal of Fluorine Chemistry 119(2003)101±107105
EIMS20eV,m/z(rel.int.):116[MeSCF3] (100),97 [MeSCF2] (2),82[SCF2] (47),69[CF3] (8),63[SCF] (4),59[NMe3] (88),58[Me2NCH2] (90),47[MeS] (15).
Anal.Calcd.for C5H12F3NS:C,34.3;H,6.9;N,8.0. Found:C,32.4;H,6.9;N,7.4.
Cesium tri¯uoromethanethiolate,CsSCF3:Colorless pow-der:mp%1588C(dec.).
NMR data are given in Section2.1.
EIMS20eV,m/z(rel.int.):82[SCF2] (100),63[SCF] (71).
4.1.1.Synthesis of di(benzo-15-crown-5)cesium trifluoromethanethiolate,[(B-15-C-5)2Cs]SCF3
An amount of0.15g(1.0mmol)CsF was added to a solution of0.54g(2.0mmol)of benzo-15-crown-5in5ml glyme at ambient temperature.After a turbid suspension has been formed,the reaction mixture was cooled toÀ308C, while[(B-15-C-5)2Cs]F precipitated.Elemental sulfur (0.03g,1.0mmol)suspended in2ml glyme was added and directly afterwards0.18ml(1.2mmol)of Me3SiCF3. The reaction mixture was allowed to warm up slowly(2h)to ambient temperature and stirred for additional30min,while a colorless solid precipitated from the meanwhile orange-brown solution.19F NMR spectroscopic control revealed that the solution mainly contained by-products(Me3SiF, CF3H)and excess Me3SiCF3.The colorless solid was col-lected in nearly quantitative yield,dried in vacuo and used for further spectroscopic investigations.
Di(benzo-15-crown-5)cesium tri¯uoromethanethiolate, [(B-15-C-5)2Cs]SCF3:Pale ochre powder:mp61±638C. 19F NMR(188.3MHz,CD3CN):d À7.75ppm(s,br, W1=2 175Hz);(DMF-d7)À5.11ppm(s,1J F;C 293:4Hz, W1=2 2:1Hz).
1H NMR(200.1MHz,DMF-d7):d 6.97ppm(m,4H, arom.),4.11ppm(m,4H,OCH2),3.80ppm(m,4H,OCH2), 3.65ppm(s,8H,OCH2).
13C NMR(50.3MHz,DMF-d7):d 149.4ppm(s,C-1,2);140.0(q,1J F;C 288:8Hz,SCF3),122.0(s,C-3,4), 114.8(s,C-5,6),70.6(s,OCH2),70.0(s,OCH2),69.3(s, OCH2),68.9(s,OCH2).
EIMS20eV,m/z(rel.int.):236[C14H20O5] (100). Anal.Calcd.for C29H40F3O10CsS:C,45.2;H,5.2.Found: C,46.0;H,5.1.
4.2.Nucleophilic trifluorothiomethylations
All reactions were performed in MeCN or EtCN solu-tions.An amount of0.18g[NMe4]SCF3(1.03mmol)or 0.24g CsSCF3(1.03mmol)were dissolved in2ml of the solvent.After addition of approximately1mmol of the substrates(0.5mmol HgCl2;C5F5N was used in excess), the reaction mixtures were stirred for5min at room tem-perature(À308C with Me3SiCl)and the course of the reaction was monitored by19F NMR spectroscopy.In all successful experiments,MSCF3had completely reacted within this period.In all other cases,the signal of MSCF3 was still detected after stirring for24h at room temperature without any signi®cant signals which might evidence the formation of the expected products.
Compounds mentioned in Schemes2and3were identi-®ed exclusively on the basis of published19F NMR data. Citations are indicated in the corresponding schemes. pilation of the high resolution19F NMR data (188.3MHz)of the products of nucleophilic trifluorothiomethylations
EtSCF3(CD3CN):d À40.6ppm(s,1J F;C 303:8Hz). PhCH2SCF3(CD3CN):d À40.6ppm(s,1J F;C 305:2Hz).
CH2=CHCH2SCF3(MeCN):d À40.7ppm(s, 1J F;C 305:2Hz).
1-CF3S-2,4-(NO2)2C6H3(MeCN):d À41.2ppm(s, 1J F;C 309:4Hz).
4-CF3SC4F4N(CD3CN):d À39.8ppm(3F,t,1J F;C 308:4Hz,5J F;F 5:6Hz),À89.4ppm(4F,m),À132.5ppm (4F,m).
CuSCF3(MeCN):d À16.6ppm(s,1J F;C 298:2Hz). AgSCF3(MeCN):d À21.6ppm(s,1J F;C 301:7Hz). Hg(SCF3)2(MeCN):d À23.2ppm(s,1J F;C 304:1Hz). PhHgSCF3(EtCN):d À21.5ppm(s,1J F;C 302:4Hz). (CF3S)2(CD3CN):d À45.4ppm(s,1J F;C 313:9Hz, 5J F;F 4:6Hz).
S(CF3)2(MeCN):d À38.1ppm(s,1J F;C 309:2Hz, 4J F;F 9:5Hz).
Acknowledgements
Yurii L.Yagupolskii thanks the Deutsche Forschungsge-meinschaft for a grant.We thank our technicians Sigrid Buslei and Silke Quadt for their help in doing a great part of the experimental work.
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