July
Trifluoromethylthioalkanes, -olefins,
1967
2063
and -acetylenes
Trifluoromethylthioalkanes, -olefins, and -acetylenes J. F.
Harris, Jr.
Contribution No. 1280 from the Central Research Department, Experimental Station, E. I. du Pont de Nemours and Company, Wilmington, Delaware 19898 Received February 20, 1967
A variety of poly(trifluoromethylthio) compounds, including tetrakis(trifluoromethylthio)methane, tetrakis(trifluoromethylthio )ethylene, and bis(trifluoromethylthio)acetylene has been synthesized. The ethylene, prepared by pyrolysis of the methane, is easily attacked by nucleophiles, e.g., methoxide and aliphatic amines. The acetylene also reacts with nucleophiles and undergoes free-radical addition reactions.
The chemistry of fluorosulfur compounds has grown rapidly during the past few years; yet relatively few organic compounds containing CF3S groups have been reported.1 With the development of convenient preparations of trifluoromethanesulfenyl chloride,2 bis(trifluoromethylthio)mercury,3a and trifluoromethanethiol,8b a great number of CF3S compounds are potentially available. This paper presents the results of a study of the preparation and properties of a variety of trifluoromethylthioalkanes, -olefins, and -acetylenes. Alkanes.—Several CF3S-substituted alkanes (I-VI) with varying numbers of CF3S substituents have been prepared by reactions of bis (trifluoromethylthio) mercury with the corresponding haloalkanes (eq 1 and Tables I and II).4 The reactions were generally car-
RX + (CF3S)2Hg
—>
RSCF3
+ HgX2
(1)
tied out at atmospheric pressure and at temperatures in the range 100 to 130°, or at reflux in those cases where the haloalkane was relatively low boiling. Usually an excess of the mercury salt was employed. The low melting point (39-40°) and solvent properties CF3S(CH2)„SCF3
CF3SC2H5
II,
I
=
1, 2, 3, 5
(CF3S)bCH
III
(CF3S)4C
(CF3S)2CHCH3
(CF8S)2CHCH2SCF3
IV
V
VI
of this compound obviated the necessity of an added solvent. The halides employed were generally iodides or bromides. If codistillation of mercury compounds with the product was encountered, the crude reaction mixture was dissolved in trichlorofluoromethane (Freon11), saturated with anhydrous HC1, and then filtered to remove the precipitated HgCl2 prior to distillation. In the reactions with halomethanes, the reactivity increased with the number of halogen substituents. Thus, methylene iodide reacted relatively slowly, several hours at 120° being required to produce a high 1). Iodoform reacted considerably yield of II (ft faster at somewhat lower temperature. Carbon tetrabromide reacted so exothermically at 75° that it was difficult to contain the mixture in the reaction flask, and
partial pyrolysis of the product (IV) occurred, resulting in the formation of tetrakis(trifluoromethylthio)ethylene (eq 2). A less vigorous reaction occurred with CBr4
+
(CF3S)2Hg —>-
C(SCF3)4
+ (CF3S)2C=C(SCF3)2 (2)
IV
VII
dibromodichloromethane, and this reaction proved to
be the method of choice for preparing pure IV. Mono-, bis-, and tris(trifluoromethylthio)ethane (I, V, and VI) were analogously prepared but the yield decreased as the number of halogen atoms increased. sym-Tetrabromoethane appeared not to have reacted with the mercury salt after 18 hr at 150°. Spectra of Trifluoromethyl Sulfides (Table ).—The infrared spectra are relatively simple and are completely consistent with the structures assigned. For example, the spectrum of (CF3S)4C (IV) contains only four strong bands, two at 1157 and 1082 cm-1 indicative of CF bonds, a band at 704 cm-1 which may be a C-S stretch band, and a band at 758 cm-1. This latter band was observed in the spectra of all of the CF3S compounds encountered in this study.6 The spectra of other trifluoromethyl sulfides are tabulated in Table III.
The ultraviolet absorption spectra (Table III) of trifluoromethyl ethyl sulfide (I) and those bis(trifluoromethylthio) alkanes with at least two carbon atoms between the CF3S groups (II, 2,3,5) contain a maxiThe corresponding band in nonmum at 218-219 µ. fluorinated primary alkyl sulfides occurs at about 210 µ (with a shoulder at 229 µ) and has been attributed to the promotion of a nonbonding 3p electron on sulfur =
a vacant d orbital.6 When there are two CF3S groups on the same carbon, as in II ( 1) and V, the maximum is shifted to longer wavelengths (from 219 to 229 µ) and intensified, but not so much as in the nonfluorinated analogs.7 This shift to longer wavelengths in the spectra of alkyl mercaptals has been attributed to 3-p-d overlap of the proximate sulfur atoms.7·8 The higher energy of transition in the fluorinated mercaptals is probably a result
to
=
=
(1) Compounds containing trihaiomethylthio groups have been reviewed recently by A. Senning, Chem. Rev., 66, 385 (1965). (2) C. W. Tullock and D. D. Coffman, J. Org. Chem., 26, 2016 (1960). (3) (a) E. H. Man, D. D. Coffman, and E. L. Muetterties, J. Am. Chem. Soc., 81, 3575 (1959); (b) R. N. Haezeldine and J. M. Kidd, J. Chem. Soe., 3219 (1953). (4) Man, Coffman, and Muetterties8* first used this method for the preparation of CF»S compounds from ¿-butyl chloride, benzyl chloride, allyl chloride, and acetyl chloride. Other trifluoromethyl sulfides have been prepared by addition of CFeSH to olefins4* [J. F. Harris and F. W. Stacey, J. Am. Chem. Soc., 88, 840 (1961) J, by the addition of CFjSCl to halo o!efins4b [J. F. Harris, ibid., 84, 3148 (1962)], and by free-radical reactions of CFsSCl with hydrocarbons40 [J, F. Harris, J. Org. Chem., 81, 931 (1966)],
(5) This band has been attributed to the C-S stretching frequency as well to the CFs deformation frequency; J. K. Brown, and K. J. Morgan, “Advances in Fluorine Chemistry,” Yol. 4, Butterworth, Inc., Washington, D. C., 1965, p 303. (6) . H. Jaffé and M. Orchin, “Theory and Applications of Ultraviolet Spectroscopy,” John Wiley and Sons, Inc., New York, N. Y., 1962, p 476. The hyperconj ugating ability of fluoro substituents may contribute to the lower energy of excitation in the trifluoromethyl sulfides; ~FCFf=S +R. (7) For example, the Xmax of (CHsShCHz occurs at 235 compared with 210 µ for CzHeSCsHe: E. A. Fehnel and M. Carmack, J. Am. Chem. Soc., 71, 84 (1949). (8) S. Oae, W. Tagaki, and A. Ohno, Tetrahedron, 20, 437 (1964). as
Harris
2064
Yol.
32
Table I
Reactions Haloalkane, g (mole)
C2H5I, 50 (0.32) CH2I2, 40(0.149) CHI3, 20 (0.0508) CBr4,« 40 (0.121)
of
Bis(trifluoromethylthio)mercury
Quantity of (CFiS)iHg, g (mole) 130 (0.32) 80 (0.199) 50 (0.124) 200 (0.497)
Haloalkanes
with
Time, hr 21 21
Temp, eC
Reflux 120-125 117-121
Product, % CF3SC2H6, 78 (CF3S)2CH2, 73 (CF3S)3CH, 83 (CF3S)4C, 37
5
70-75
Few minutes
(CF3S)2C=C(SCF3)2, 18 CBr2Cl2,6 15 (0.0618)
BrCH2CH2Br, 15 (0.08) Br2CHCH3, 18.9 (0.10) Br2CHCH2Br,6 20 (0.075)
100
100(0.248) 50 (0.124) 63 (0.157) 65 (0.161) 100 (0.248) 50 (0.124)
(CF3S)4C, 67
2
Reflux Reflux
22.5
CFjSCHíCHíSCF,, 61
20
130
16
(CF3S)2CHCH3, 42 (CF3S)2CHCH2SCF3, 24 CF3S(CH2)3SCF3, 60 CF3S(CH2)5SCF3, 69
Reflux 3.5 100-110 1.5 I(CH2)5I, 25 (0.0772) On warming a mixture of CBr4 and (CF3S)2Hg, a rapid exothermic reaction occurred during which the temperature of the reaction mixture rose to 130°. h In this case the trap contents were dissolved in 100 ml of Freon 11, prior to treatment with anhydrous HC1.
I(CH,),I, 50(0.169)
Table II
CF3S-Substituted Alkanes Prepared Bp, °C (mm)
Compound
cf3sc2h6
40
(CF3S)2CH2
78
(CFsS)3CH
106.5
(CF3S)4C
47(10)
CFgSCHiCHSCFg
110
CF3S(CH2)3SCF3 CF3S(CH2)5SCF3 (CF3S)2CHCH3 (CF3S)2CHCH2SCF3
146
74(10) 93
63-67(60)
from
Bis(trifluoromethylthio)mercury and Haloalkanes
Formula
n25D
1.3369-
C3HsF3S
1.3373 1.3562 1.3650 1.3980 1.3738
C3H2FíS2 C4HF9Sa c3f12s4
1.3825 1.3977 1.3632 1.3830
z—-Carbon, %-> Caled Found
c4h4f6s2 C6H6FeS2
CvHioFeS, C4H4FeS2
C5H3FeS3
of the electron-withdrawing effect of the trifluoromethyl groups which makes the 3-p electron pair on the sulfur atom less available for p-d bonding. The maximum in the spectrum of (CF3S)3CH occurs at slightly lower wavelength than the maximum in the spectrum of (CF3S)2CH2, but it is significantly intensified.9 In the spectrum of (CF3S)4C more intensification occurs and a new band appears at 246 µ,10 which may indicate promotion to a p-d orbital emcompassing all four sul-
/—Hydrogen, %—*. Caled Found
4—Fluorine, %—» Caled Found
43.8
43,6
»-Sulfur, %— Caled
Found
24.6
24.9
52.7 52.4 29.6 29.3 54.1 30.4 54.0 30.0 14.4 14.4 54.8 30.8 55.2 31.0 Identical with the product obtained from the addition of CF3SH to CF3SCH=CH2 25.1 46.7 26.2 24.6 2.5 2.6 47.1 26.2 41.9 41.9 30.9 31.2 3.7 3.9 23.5 24.1 49.5 49.8 27.8 27.9 18.2 18.4 0.9 1.3 51.8 51.9
oxidized to the corresponding sulfones (Table IV) with chromium trioxide in glacial acetic acid at 95°.11 CrOs
CF3SCH2CH2SCF3-> HOAc
CF3S02CH2CH2S02CF3
(3)
Reactions of Trifluoromethyl Sulfides. Oxidation.— Several of the trifluoromethyl alkyl sulfides were
The bis(trifluoromethylthio) alkanes II ( 2, 3, 5) yielded crystalline bissulfones, but from the reaction with II (n 1), no sulfone was isolated. Attempted Formation of Salts.—No reaction occurred when trifluoromethyl ethyl sulfide and mercuric chloride were mixed in absolute ethanol. Similarly, no sulfonium salt was obtained when bromine and this sulfide were mixed. This lack of reactivity has been noted previously with other fluoroalkyl sulfides12 and is no doubt due to the electron-withdrawing capacity of the fluoroalkyl groups which decreases the coordinating ability of the unshared pairs of electrons on the sulfur atom. Pyrolysis of Tetrakis(trifluoromethylthio)methane. —Tetrakis(trifluoromethylthio)methane (IV) can be distilled at atmospheric pressure without noticeable decomposition; however, after 18 hr at reflux, samples contain small quantities of rather volatile decomposition products. When IV is passed through a packed quartz pyrolysis tube at elevated temperature, two modes of decomposition were observed depending upon the conditions employed. At 400° and 1-1.5 mm, the liquid product was almost entirely bis(trifluoromethyl)trithiocarbonate (eq 4). There were also present small amounts of bis(trifluoromethyl) sulfide, bis(trifluoro-
(9) This same relationship has been noted in the spectra of CH2(SC2Hs)2 and CH(SC2He)8.8 (10) The analogous band in the spectrum of tetrakis(methylthio)methane occurs at 244.5 µ: C. W. N. Cumper, A. Melnikoff, and A. L. Vogel, J. Chem. Soc., Sect. A, 242 (1966).
(11) This recipe has been used previously for oxidation of fluoroalkyl sulfides to sudones: W. E. Truce, G. H. Birum, and E. T. McBee, J. Am. Chem. Soc., 74, 3594 (1952). (12) K. E. Rapp, R. L. Pruett, J. T. Barr, C. T. Bahner, J. D. Gibson, and R. H. Lafferty, ibid., 72, 3642 (1950); 74, 749 (1952).
fur atoms.
CFS
=
=
July
Trifluoromethylthioalkanes, -olefins,
1967
and
2065
-acetylenes
methyl) disulfide, and tetrakis(trifluoromethylthio)ethylene. At 400° and atmospheric pressure, the major product was tetrakis(trifluoromethylthio)ethylene (eq 5). Considerable quantities of bis(trifluoromethyl)
+ vnr
mm)l>-
(CF3S^C==S
CF3SCII2CH2C1
(6)
XII, 83% Dehydrochlorination of XII with KOH afforded XI in yields up to 97% (eq 7). CFsSCHiCHiCl + KOH
—>
CF„SCH=CH2
(7)
XI, 97% (13) XII
has also been prepared by the trifluoromethanethiol to vinyl chloride.4b
ultraviolet-initiated addition of
=
CF3SCH=CH2 + Cl,
—>
CF3SCHC1CH2C1
(8)
XIII CF3SCH=CH2 + Br2
kv —>
CF3SCHBrCH2Br
(9)
XIV CF3SCH=CH2 + CF3SH
-X CF3SCH2CH2SCF3 II,
=
(10)
2
of the product of reaction 10 was established by its H1 nmr pattern which consists of a single unsplit at r 6.82. This pattern is methylene resonance identical with that of the product obtained from the reaction of (CF3S)2Hg with 1,2-dibromoethane as described earlier in this paper (Table I). (14) Chem., (15) (16)
R. T. Hobgood, Jr., G. S. Reddy, and J. H. Goldstein, J. Phys,
67, 110 (1963). G. S. Reddy and J. H. Goldstein, J. Am. Chem. Soc., 83, 2045 (1961). All F19 nmr spectra reported in this paper were determined at 56.4 Me. Solutions of about 10% concentration in trichlorofluoromethane (Freon-11) were used. Chemical shifts are reported in cycles per second of the solvent. (cps) measured from the resonance
Table III Infrared A. Alkanes
cf*sc*h5
and
C—H stretch, cm-1
C—H asym deform, cm-1
2980 (m) 2940 (m) 2880 (m)
1432 (m) 1457 (s)
Ultraviolet C—H sym deform, cm-1
1386
(m)
Spectra
Trifluoromethylthio
of
C—F,
cm
1161 1122
(vs) (vs)
*
CFaS, cm
754 (s)
2240 (w)
Compounds
2066
Unassigned infrared bands, cm-1
1876 (w), 1282 (s), 1244 (ra), 1219 (m), 1057 (s), 973 (s), 787 (m), 684 (w), 657 (m)
CFaS(CH2)sSCF, 1221
2980 (m)
CFaS(CH2),SCFa
CFaSiCEWaSCF,
2900(w)
1457 (s) 1431 (s)
2950 (w)
1431 (s)
3030 (m) 2975 (w)
1411 (m)
(CF,S)2CHCH»
3000 (m) 2950 (m) 2895 (w)
1455 (s)
(CFiSi.CHCHiSCFa
2970
(m)
1420
(m)
(CF,S),CH
3010 (m)
1301 1313
(m) (m)
CFaSCHiSCF,
B. Ethylenes
cf9sch=cii2
c=c stretch 1611 (s)
C—H stretch
C—H op deform
3110 (m) 3075 (m) 3030 (m)
914 (s) 957 (s) 1839 (s)
758 (s)
1
C—H ip deform
1387 (m) 1283 (s)
CFaSCH=CHSCF, (cis)
1561 (s)
3080 (m)
691 (s)
1407
CF^CH=CHSCF, (tram)
1554 (s)
3080 (m)
923 (s)
1301
(w)
(m-s) and/or 1319 (m-s)
757 (s)
35
219
93
1236 (vs) 2240 (m) 1161 (vs) 1129 (vs) 1102 (vs) 2270 (s) 1167 (vs) 1133 (vs) 1099 (vs) 2260 (m) 1142 (vs) 1128 (vs) 1091 (vs) 2270 (m) 1157 (vs) 1082 (vs) 2270 (m) C—F
1177 (vs) 1152 (vs) 1138 (vs) 2275 (m-s)
2270 (s) 1170 (vs) 1143 (vs) 1102 (vs) 1170 (vs) 1142 (vs) 1103 (vs) 2270 (s)
1878 (m), 1360 (m), 1322 (s), 1276 (s), 1012 (m), 963 (m), 841 (s), 779 (m), 722 (w), 690 (w) 2090 (w), 1863 (w), 1300 (s), 1281 (m), 1227 (s), 1021 (w), 949 (w),
218
102
219
143
229
311
224
224
906 (w), 850 (m), 837 (m), 704
(m) 757 (s)
1
(CFaS)iC
219
(vs)
1048 (vs) 2270 (m) 1166 (vs) 1126 (vs) 1102 (vs) 2240 (w) 1091 (vs)
1390 (s)
e
758 (s)
756 (s)
1870 (m), 1390 (m), 1309 (m), 1298 (m), 949 (w), 914 (w), 868 (w), 839 (m), 821 (s), 728 (s) 2500 (w), 2430 (w), 1877 (m), 1662 (m), 1600 (m), 1302 (m-s), 1261 (s), 1215 (s), 1056 (s), 973 (s), 707 (s), 672 (m) 1850 (m), 1728 (w), 1653 (w), 1570 (w), 1296 (m), 1250 (m), 948 (w), 891 (s), 719 (s), 679 (m)
Harris
758 (s)
1898
225
758 (s)
1920 (w), 1880 (w), 1849 (w), 1710 (w), 1304 (m), 953 (m), 922 (w), 791 (m), 704 (s)
223 246 (sh)
CFaS
(w), 1852 (w), 1004 (w), 942 (w), 870 (w), 708 (s), 663 (w)
Unassigned infrared bands
mp
598
1620 1040
«
2345 (m-s), 2295 (m-^), 1901 (s), 1040 (s), 1037 (s), 1029 (s), 733 (s), 728 (s), 722 (s)
209 233
5300 1100
759 (s)
2860 (w), 1882 (m-s), 1862 (m-s), 1732 (w), 1680 (w), 1304 (s), 902 (m-s), 838 (s), 718 (m-s)
218 234
6520 5970
758 (s)
2090 (w), 1885 (m), 1860 (m), 1690 (m-s), 1403 (w), 841 (m), 801 (s)
223 247
5340 7210
767 (s) 761 (s)
756 (s)
Vol.
32
July
3
©
3
Teifluobomethylthioalkanes, -olefins,
1967
©
X
©
©
©
©
X
x
©
©
eq
eq
,-c
©
eq X
©
CF3SCH=CH2 + CF3SC1 XI
©
oo
1"H
^
-Í
o
W
X
^
X
to C'q ¡y
x & o
r* ©
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X
fEl * **
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X
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sE w
3g
fl X
®'m* w
a
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sB w
ei
X
-
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x
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2
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to a ¿c»
w
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x
fe x (N sS
i-H
eq ^
^
vB
is
N
eq
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„
eo =g
tJH ©
„
*
©
’-’
©
~
x
S t~
5
*
hilifi
¿
+ (CF3S)2CHCH2SCF3 + VI, 9%
CF3SSCF3
-g
©
©
(11)
disulfide was formed as well as small quantities of several other compounds which were not further investigated. Samples of each of the three major products were isolated by preparative-scale gas chromatography. The structure XV assigned to the predominant product was consistent with the H1 nmr spec3.79 trum (neat) which consists of a doublet ( and a 4.73 from J 5.5 TMS, ( ppm cps) triplet ppm) in an intensity ratio of 2:1. This spectrum in itself is not sufficient for the assignment since the spectrum of the other possible 1:1 adduct (XVII) would be expected to contain the same features. An authentic sample of XVII was prepared by the chlorination of II { 2) (eq 12). The H1 nmr pattern (neat) =
—
Io3
¿I
(CF3S)2CHCH2CI + XV, 43%
=
??
eq eq
o|
7%
—s-
x
©
eq
©
"m
CF3SCHC1CH2C1
^ CC
Hi
^
^
©
©
s-Z'S
6 ^
;Sa
X
$S 5
2 XS t".
b*.
eq
b-
NOJ^
X
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„
^
s
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If
a
©
^
® 2 p
©
8
*
'e
O
j®
/—?
sg
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a
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X
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Q ^ aS a
eq
II
%S x
©
'oa ..
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I
2067
hv
©
eq
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x
x
eq
©
eq
-acetylenes
An ultraviolet-initiated free-radical chain reaction of XI also occurs with CF3SC1 to yield l,l-bis(trifluoromethyIthio)-2-ch!oroethane (XV) as the major product together with smaller amounts of XIII and VI (eq 11).17 A gas chromatogram of the crude reaction mixture indicated that some bis (trifluoromethyl)
©
©
and
^
^
=
hv
I
x
R
&
02 ©
eq
R
x
^ 9
_ ©
N
eq eq
eq ^ ..
©
eq SN 1H eq
x
B
I ©
(5
x
·
S P á > > ©
II,
a
.
X
CF3SCH2CH2SCF3
s
_gi S s
E
^
w|
I
A*
©
R
s X8t> eq rn eq
©
A
©
B
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X
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to
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(
X
X
X
h
eq
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i-H ©
h
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u
~
eq eq
N N ic tb-
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a fe a
3 5 X X
B D
A"
33
©
BB ©
B
2 5
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S3X
vAS
X
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S? ® N N
X
X
o
§ 3
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Ph
©
w
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00
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x
0 § X
III
U
=
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CH3 CH3
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t>-
'to
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(12)
XVII
of XVII also consists of a doublet ( 3.31 ppm, J 5.26 ppm) in a 2:1 intensity 7 cps) and a triplet ( ratio, but, as both the chemical shifts and the coupling constant are different from those in the pattern just discussed, it is clear that the major product of eq 11 cannot have structure XVII and must therefore be XV. The structure of 1,1,2-tris (trifluoromethylthio) ethane (VI) was assigned on the basis of the infrared (Table III) and H1 nmr spectra which were identical with those of VI prepared by the reaction of (CF3S)2Hg with 1,1,2-tribromoethane. Similarly, the H1 nmr pattern of XIII was identical with the pattern of the product of eq 8. At 200° XI undergoes a reaction with 2,3-dimethylbutadiene to form a 1:1 adduct (eq 13). The DielsAlder adduct structure (XVIII) ivas assigned on the basis of the Hl nmr spectrum which contained no
'
A
£
CF3SCHC1CH2SCF3
2
=
T*1_© X eq h eq
S
—>
=
©
X
i-1
=
+ Cl,
3
©
CF3SCH=CH2
+
CH2=C— C=CH2
-^2!*.
XI
J ©
©
X
55
in the vinyl proton region and the infrared spectrum which also indicated the absence of vinyl hydrogens. No C=C stretch band was observed in the infrared spectrum but one was observed at 1670 cm-1 in the Raman spectrum. These spectra would be inconsistent with an alternative cyclobutane structure. resonances
0
to
to
m
?
O
g
q
1 to Ü
9 to g
*g to
£
V
02
g
V
q
q
9 to
o? 6?
g
g
P
%
|
c
=
Job
=
17 cps
J~
Jao
=
9 cps
Jac
-380.7 -290.4 -304.5
=
-0.3 0.0 0.4 0.2 Jed JtF =1.4 cps » The values listed in this table for CF3SCH=CH2 mated from Figure 1. Jbc JoF JbF
=
J bo J ad J bd
0
^0 =0.6 cps
-317.3
16.4 10.3
=
16.3 19.5
16.4 19.9
1.4 2.0
35.2
35,1
33.9
34.1
1.5
2.0
Sulfur, % Caled Found
19.8 21.8 20.8 19.1
20.3 21.7 20.5 19.2
2.13. CH2=CHí
SCHa(d) =
C4H4F604S2 C6H6F604S2 C,H,0FbO482
Fluorine, % Caled Found
the basis of elemental analysis, the infrared spectrum which contains a strong C=C stretch band at 1533 cm-1, and the H1 nmr pattern which consists of a single, unsplit resonance in the vinyl proton region at
Vinyl Sulfide
C=
C0a
—334.1 cps —334.0 cps
+ pentane
Ho
/
Carbon, % Hydrogen, % Caled Found Caled Found
c3h5f3o2s CH3OH
Table V Trifluoromethyl (60 Mc/sec)°
H(b)
Formula
1.3591
H(c)
SCFa
Recrystyn solvent
n«D
172-174 86-87 61-62
89
of
°C
=
Tetrakis (trifluoromethylthio) ethylene (VII).—Compound VII was most conveniently prepared on a large scale by heating a mixture of carbon tetrabromide and bis(trifluoromethylthio)mercury to 100° in an autoclave (eq 2). From these reactions the ethylene was obtained scf3
CF3S
c=c; scf3
“
cf3sz
=
=
were esti-
On storage in pressure vessels at room temperature, XI polymerized to a viscous liquid. Polymerization experiments with azonitrile or peroxide initiators
yielded solid polymers which were somewhat elastic.18 cis- and irons-1,2-Bis (trifluoromethylthio) ethylene (XIX).—Dehydrobromination of bromo-l,2-bis(trifluoromethylthio) ethane (XXa) led to formation of a mixture of the cis and trans isomers of 1,2-bis (trifluoromethylthio) ethylene (XIX, eq 14). Pure samples of Br EtOH
I
CF3SCHCH2SCF3 +
KOH--*-
XXa
CF3SCH=CHSCF3 XIX (cis and trans)
(14)
the two isomers were isolated by preparative-scale gas chromatography. The less prevalent isomer was as-H
CFsS
H'/C
/H >=C xscf3 CF3Sz Hs
°\SCF3
XlXa
XlXb since its infrared at 923 cm-1 which band strong
signed the trans structure
(XlXa)
spectrum contains a probably is a
||
(C2H5)2NC—F
(18)
XXIII
Spectra of Ethylenes.—The infrared spectra of the ethylenes contain a strong band in the 1450-1600-cm-1 region which can be ascribed to the C=C stretching frequency. As the number of CF3S groups on the C=C double bond increases, this band exhibits a shift from 1611 cm-1 for trifluoromethyl vinyl sulfide21 to 1450 cm-1 (Raman) for tetrakis(trifluoromethylof a strong C=C thio)ethylene. The occurrence stretch band (1554 cm-1) in the spectrum of
Caled.
Found
Caled
Found
234(5980)
28.1
28.0
50.0
49.8
218 (6530) 247 (7210)
28.1
28.0
50.0
49.9
H‘ (r),
F18,
Ultraviolet,
Bp, °C
n2,D
ppm
cps
Xjnsxi
96.5
1.3831
3.27
2392
2428
CIS
96.5
trans
1.3892
3.27
µ ( 1.3803. The H1 nmr spectrum consists of a doublet 7.3 cps) and a triplet at 5.18 in an intensity ratio at 6.50 (/ of 2:1 and is identical with the spectrum of VI. The infrared spectra (Table III) of thes two materials are also identical. Anal. Caled for C3H3F9S3: F, 51.8; S, 29.1. Found: F, 50.8; S, 29.3. 13. Preparation of Chloro-l,2-bis(trifluoromethylthio)ethane by Chlorination of 1,2-Bis(trifluoromethylthio)ethane.—A solu=
=
=
tion of 25.3 g (0.110 mole) of 1,2-bis(trifluoromethylthio)ethane and 40 ml of fluorotrichloromethane was placed in a flask fitted with gas inlet tube and an acetone-Dry Ice condenser. About 1 ml of liquid chlorine (at —76°) was added from a small graduated trap cooled in Dry Ice, and the refluxing mixture was irradiated with a sun lamp until the yellow color was nearly gone. This procedure was repeated until a total of 5 ml (7.8 g, 0.110 mole) of chlorine had been added. After distillation of the solvent the residue was examined by gc (6-ft 20% diglyceride of -trifluorohexanoic acid on Columpak, 82°, He flow rate of 55 ml/mm) and found to contain several compounds, the most abundant being the starting material and the monochloro compound. Upon distillation of the residue through a small spinningband still, a fraction (4.04 g) was obtained boiling at 60-65° (80 mm) which was shown by gc to contain about 75% of the monochloro compound. A pure sample was separated by preparative-scale gc, bp 129°, n24D 1.3950. The H1 nmr spectrum 7 cps) and a triplet (neat) consists of a doublet at 3.31 ppm (J at 5.26 in an intensity ratio of 2:1. Anal. Caled for C4H3C1F6S2: F, 43.0; S, 24.2. Found: F, =
42.8; S, 23.7. 14. Reaction of Trifluoromethyl Vinyl Sulfide with 2,3-Dimethylbutadiene.—A mixture of 10 ml of trifluoromethyl vinyl sulfide and 10 ml of 2,3-dimethylbutadiene contained in a 100-ml stainless steel autoclave was heated at 200° for 15 hr. Distillation of the reaction mixture gave 9.17 g (about 56%) of 4-trifluoromethylthio-l,2-dimethylcyclohexene distilling at 49-54° (3.75 mm), n®D 1.4470-1.4498. A gas chromatogram indicated that several impurities were present. A pure sample of the product was obtained by preparative-scale gc (4-ft 25% fluoroalkyl pyromellitate (Zonyl E-T) on Gas Chrom R, 125°, He flow rate of 900 ml/min), bp 89° (32 mm), n26n 1.4446. Anal. Caled for C9Hi3F3S: C, 51.4; H, 6.2; S, 15.3. Found: C, 52.1, 51.9; H, 6.4, 6.4; S, 14.9, 15.0. 15. Dehydrobromination of 1,2-Bis(trifluoromethylthio)bromoethane. Preparation of cis- and 85%) Fraction 2 was also almost entirely a single one compound. compound. A sample of the main component of each fraction was separated by preparative scale gc. The main component of fraction 1 was shown by infrared spectroscopy to be , -diethylthiocarbamoyl fluoride20: bp 53° (1.60 mm), nud 1.4934; ultraviolet 304 m/x (e 108), 254 µ (e 18,100). Anal. Caled for C5H10FNS: F, 14.1; N, 10.4. Found: F, 14.3; N, 10.5, 10.9. The main component of fraction 2 was identified as l,l-bis(trifluoromethylthio)-2-fluoro-2-diethylaminoethylene or an isomer thereof, bp 33° (0.10 mm), n24n 1.4348. The infrared and ultraviolet spectra are tabulated in Table III. Anal. Caled for C8H,0F,NS2: F, 41.9; N, 4.4; 8, 20.2. Found: F, 41.2; N, 4.6, 4.7; 8, 20.1, 20.2. 19. Bromination of l,2-Bis(trifluoromethylthio)ethane.—A mixture of 60 g (0.26 mole) of l,2-bis(trifluoromethylthio)ethane, 34 ml of bromine, and 150 ml of carbon tetrachloride was placed in a 500-ml flask fitted with a Glascol heater and a reflux condenser. The mixture was refluxed and irradiated with a sun lamp for 3 days. Distillation of the reaction mixture through a small spinning-band still gave 35.3 g (44%) of bromo-l,2-bis(trifluoromethylthio)ethane distilling at 75° (77 mm), 28n 1.4226, and 43 g (43%) of dibromo-l,2-bis(trifluoromethylthio)ethane distilling at 59° (7 mm), 28d 1.4599. Monobromide.—The H1 nmr pattern contains a doublet at 7 cps) and a triplet at 4.66 in an intensity ratio of 6.37 (J =
2:1. Anal.
Caled for Br, 25.9; F, 36.7.
C4H3BrF6S2:
Br, 25.8; F, 36.9.
Found:
Dibromide.—The H1 nmr pattern contains two singlets at 4.27 and 5.7 in an intensity ratio of 1.13:1. The relative intensities of these peaks vary as the fraction is distilled. Anal. Caled for C4H2Br2FeS2: Br, 41.2; F, 29.4. Found: Br, 41.9; F, 29.4. 20. Dehydrobromination of Dibromo-l,2-bis(trifluoromethylthio)ethane. Preparation of Bis(trifiuoromethylthio)acetylene. —One-hundred and fifty-five grams of potassium hydroxide (85%) was placed in a flask fitted with a dropping funnel, a gas inlet tube through which a slow stream of nitrogen passed, an exit tube which led to a Dry Ice cooled trap, and an oil bath. The oil bath was heated to 155° which caused the potassium hydroxide to melt. While the oil bath was maintained at 155°,
and -acetylenes
2073
49.83 g (0.129 mole) of dibromo-l,2-bis(trifluoromethylthio)ethane was added during about 0.50 hr. Distillation of the trap contents through a small Vigreux still gave 19.3 g (66.5%) of bis(trifluoromethylthio)acetylene distilling at 81-85°, n25o 1,39241.3928. Upon redistillation through a small spinning-band still, the product distilled at 83°. The infrared spectrum is tabulated
in Table III. Anal. Caled for 8, 28.4.
C4FeS2:
F, 50.3; 8, 28.4. Found: F, 50.4;
21. Photoinitiated Addition of Trifiuoromethanesulfenyl Chloride to Bis(trifluoromethylthio)acetylene.—A mixture of 14.8 g (0.0655 mole) of bis(trifluoromethylthio)acetylene and 11 g (0.0805 mole) of trifiuoromethanesulfenyl chloride contained in a quartz tube fitted with an acetone-Dry Ice condenser was irradiated with a low-pressure mercury resonance lamp as described above for 18 hr. Distillation of the reaction mixture through a small spinning-band still gave 11.3 g (47.4%) of tris(trifluoromethylthio)chloroethylene distilling at 52-60° (25 mm), ti26d 1.4298-1.4308. The ultraviolet and infrared spectra are tabulated in Table III. Anal. Caled for C5C1F9S3: Cl, 9.8; F, 47.2. Found: Cl, 10.3; F, 47.3. 22. Addition of Methanol to Bis(trifluoromethylthio)acetylene.—A solution of 5.0 g (0.0221 mole) of bis(trifluoromethylthio)acetylene in 55 ml of methanol was added dropwise during 5 min to a stirred solution of 0.25 g (0.0046 mole) of sodium methoxide in 25 ml of methanol. After the mildly exothermic reaction was over and the temperature had returned to room temperature, the mixture was heated on a water bath for 0.25 hr. The mixture was then poured into a large excess of water and the organic phase was removed by two extractions with 25 ml of ether. The ether extracts were dried over anhydrous magnesium sulfate, filtered, and distilled through a microstill. There was thus obtained 3.48 g (61%) of l,2-bis(trifluoromethylthio)vinyl methyl ether distilling at 73° (115 mm)-77° (117 mm), rt26n 1.4007-1.4020. The H1 nmr pattern contains two resonances in the methoxy region ( 6.11 and 6.22) and two peaks in the vinyl region ( 3.85 and 4.38) indicating the presence of both possible isomers in a ratio of about 2:1. The infrared spectrum of this mixture of isomers contains a C=C stretch band at 1613 cm-1. The ultraviolet spectrum contains maxima at 246 µ (t 5680) and 218 µ (e 4700). Anal. Caled for C5H4F6OS2: C, 23.3; , 1.6; 8, 24.4. Found: C, 23.3; H, 2.2; 8, 24.3. 23. Addition of Morpholine to Bis(trifluoromethy'thio)acetylene.—A solution of 2.89 g (0.0332 mole) of morpholine in 30 ml of anhydrous ether was added dropwise to a solution of 7.5 g (0.0332 mole) of bis(trifluoromethylthio)acetylene in 30 ml of ether. The temperature was maintained under 35°. The mixture was stirred for 10 min, heated at reflux briefly, and filtered. Distillation through a small spinning-band still gave 8.68 g (84%) of l,2-bis(trifluoromethylthio)-N-morpholinoethylene distilling at 40.5-49° (0.05 mm), «“d 1.4550-1.4600. This material became dark and viscous after a few days at room temperature. The H1 nmr spectrum contains two resonances in the vinyl proton region (r 3.67 and 4.46) in a ratio of 1:2.3 in addition to the resonances due to the morpholine group methylene protons. The intensity ratio of the methylene resonances to the vinyl proton resonances is 8:1. The infrared spectrum of this mixture of isomers contains a C=C stretch band at 1546 cm-1. The ultraviolet spectrum contains a maximum at 274 µ U
7000).
Anal. Caled for C8H9NOS2.' C, 30.7; H, 2.9; F, 36.4; N, 4.5. Found: C, 31.0; , 3.0; F, 36.2; N, 4.7. 24. Addition of 2,3-Dimethylbutadiene to Bis(trifluoromethylthio)acetylene.—A mixture of 5.0 g (0.0221 mole) of bis(trifluoromethylthio)acetylene and 2.0 g (0.0244 mole) of 2,3-dimethylbutadiene was sealed in a small platinum tube and heated at 150° for 10 hr in a bomb pressured at 1000 atm. Distillation through a small Vigreux still gave 2.32 g (34%) of l,2-bis(trifluoromethylthio)-4,5-dimethyl-l,4-cyclohexadiene distilling at 43-46° (0.30 mm), 28 1.4603-1.4610. The infrared spectrum contains CH stretching bands at 2830, 2870, 2930, and 2970 cm-1, but none higher. Anal. Caled for CioHuFeSj: F, 37.0; 8, 20.8. Found: F, 35.3; 8,20.4. 25. Preparation of Phenyl(trifluoromethylthio)acetylene.— A solution of ethylmagnesium bromide was prepared in the usual way from 16.7 g (0.153 mole) of ethyl bromide and 4.78 g (0.197
Bradsher
2074
and
g-atom) of magnesium turnings in 50 ml of anhydrous ether in a flask fitted with a gas inlet tube, a dropping funnel, stirrer, and a Dry Ice-acetone condenser. To this solution, 20 g (0.196 mole) of phenylacetylene in 30 ml of ether was added slowly. After the mixture was cooled to 15-20°, 12 ml (at —76°, 18.8 g, 0.138 mole) of trifluoromethanesulfenyl chloride was added through the gas-addition tube above the surface of the reaction mixture and allowed to reflux into the reaction mixture. This addition required about 1 hr. The reaction mixture was then poured into large volume of ice water containing an excess of hydrochloric acid. The product was removed by two extractions with 100 ml of ether. The ether extracts were washed once with water, dried over anhydrous magnesium sulfate, and rapidly distilled through a small spinning-band still. There was thus obtained 13.77 g (49%) of crude product distilling at 42.5 (1.75 mm)-56° (2.35 mm), n25D 1.5219-1.5509. Upon redistillation of this fraction, 7.20 g (26%) of phenyl (trifluoromethylthio)acetylene was obtained distilling at 43° (2.4 mm), n26d 1.5198— 1.5203. The infrared spectrum is recorded in Table III. Anal. Caled for CeHsFsS: C, 53.5; H, 2.5; F, 28.2; S, 15.8. Found: C, 53.6; H, 2.6; F, 28.0; S, 15.7. 26. Nmr Spectra.—F19 nmr spectra (56.4 Me) were obtained from 10% solutions of the compounds in fluorotrichloromethane (Freon-11) with an A-56/60 nmr spectrometer manufactured by Varían Associates, Palo Alto, Calif. Chemical shifts are reported
K. Bradsher
and
32
in cycles per second (cps) measured from the resonance of fluorotrichloromethane as an internal standard. H1 nmr spectra (60 Me) were obtained with an A-60 nmr spectrometer manufactured by Varían Associated, Palo Alto, Calif. Solutions (10%) in CC1« containing tetramethylsilane were used except where indicated.
Registry No.—I, 13003-31-1; II (n
1), 819-67-0; 2), 674-64-6; II ( 3), 13003-34-4; II ( = 5), 13003-35-5; III, 691-69-0; IV, 681-87-8; V, 674-43-1; VI, 688-53-9; VII, 13003-40-2; XI, 762-80-1; XIII, 674-36-2; XIV, 13040-44-3; XV, 1542-22-9; XVII, 13003-43-5; XVIII, 13003-44-6; XlXa, 13003-45-7; XlXb, 13003-46-8; XX, 13003-47-9; XXI, 13003-48-0; XXII, 13003-49-1; XXIII, 2266-81-1; XXV, 2069-87-6; XXVI, 13003-52-6; cis XXVII, 13003-53-7; irons XXVII, 13003-54-8; XXVIII, 13003-55-9; XXIX, 13003-56-0; XXX, 2002-89-3; trifluoromethanethiol, 1493-15-8; bromo-1,2-bis(trifluoromethylthio) ethane, 673-62-1; CF3S02C2H5, 13003-57-1; CF3S02(CH2)2S02CF3, 13040-45-4; CF3S02(CH2)3S02CF3, 13003-58-2; CF3S02(CH2)6S02CF3, 13003-59-3.
II
(
The Thiazolo[2,3-b]thiazoIium Cation. C.
Vol.
Jones
=
=
=
A New Aromatic System1
W. J. Jones, Jr.2
Department of Chemistry, Duke University, Durham, North Carolina
27706
Received December 8, 1966
Through cyclization of
