Trifluoromethylthiolation of 1,3-dithiane

Article abstract of DOI:10.1080/104265090970377

With a view to synthesize 2-(trifluoromethylthio)-1,3-dithiane (1), 1,3-dithiane (2) was reacted in dry pentane at -78°C under dry N₂ with trifluoromethylsulfenyl chloride (3) and was found to furnish the desired compound in poor yields along with ten other compounds. Under similar conditions, 2-lithio-1,3-dithiane on treatment with 2 and bis-(trifluoromethyl) disulfide (4) gave 8.0% and 10.0% yields of 1, respectively. In connection with this study, (cholromethyl) propyl sulfide and bis(propylthio)methane were synthesized. The reaction of the latter with 3 was also investigated. The characterization of the primary compound formed in the reaction of 2 with 3 using the 'INAPT'-NMR and GC-MS, the probable mechanism of the formation of the various compounds and their mass spectral identification are presented in this article. Copyright Taylor & Francis Group, LLC.

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Trifluoromethylthiolation of
1,3-Dithiane
S. Munavalli a , D. K. Rohrbaugh b , L. L. Szafraniec b
& H. D. Durst b
a Science Applications International Corporation,
Gunpowder Branch, Aberdeen Proving Ground,
Maryland
b U.S. Army Edgewood Chemical Biological Center,
Aberdeen Proving Ground, Maryland
Version of record first published: 16 Aug 2006.
To cite this article: S. Munavalli, D. K. Rohrbaugh, L. L. Szafraniec & H. D. Durst
(2006): Trifluoromethylthiolation of 1,3-Dithiane, Phosphorus, Sulfur, and Silicon and
the Related Elements, 181:2, 305-324
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Phosphorus, Sulfur, and Silicon, 181:305–324, 2006
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/104265090970377
Trifluoromethylthiolation of 1,3-Dithiane
S. Munavalli
Science Applications International Corporation, Gunpowder Branch,
Aberdeen Proving Ground, Maryland
D. K. Rohrbaugh
L. L. Szafraniec
H. D. Durst
U.S. Army Edgewood Chemical Biological Center,
Aberdeen Proving Ground, Maryland
With a view to synthesize 2-(trifluoromethylthio)-1,3-dithiane (1), 1,3-dithiane (2)
was reacted in dry pentane at −78◦C under dry N with trifluoromethylsulfenyl
2
chloride (3) and was found to furnish the desired compound in poor yields along
with ten other compounds. Under similar conditions, 2-lithio-1,3-dithiane on treat-
ment with 2 and bis-(trifluoromethyl)disulfide (4) gave 8.0% and 10.0% yields of
1, respectively. In connection with this study, (cholromethyl) propyl sulfide and bis-
(propylthio)methane were synthesized. The reaction of the latter with 3 was also
investigated. The characterization of the primary compound formed in the reac-
tion of 2 with 3 using the ‘INAPT ’-NMR and GC-MS, the probable mechanism of
the formation of the various compounds and their mass spectral identification are
presented in this article.
Keywords 1,3-dithiane; 1,3-dithiolane; bis-(trifluoromethyl)disulfide; bis-(propylthio)-
methane; free radical; catalyzed cleavage products; (chloromethyl) propyl sulfide; INAPT’-
NMR; GC-MS spectral data; lithio-dithiane; trifluoromethylsulfenyl chloride
Since the 1970s, 1,3-dithiane (2) has been extensively used as a
building block in the preparation of a vast array of organic inter-
mediates and synthons for the total synthesis of several scores of
interesting organic compounds. The synthetic utility of 1,3-dithiane
(2) rests squarely on the facile introduction of functional groups
and the convenient removal of the masking moiety, namely the 1,3-
propanedithiol fragment after the accomplishment of the stated objec-
tive. The pioneering work of Seebach and Corey1 has demonstrated
Received January 18, 2005; accepted February 8, 2005.
Address correspondence to S. Munavalli, Science Applications International Corpo-
ration, P.O. Box 68, Gunpowder Branch, Aberdeen Proving Ground, Maryland 21010.
E-mail: shekar.munavalli@us.army.mil
305

306
S. Munavalli et al.
the synthetic usefulness and versatility of the dithiane synthons.
The chemistry of dithiane and dithiolanes has been reviewed.2 An
excellent report on the synthetic applications of the anions de-
rived from 1,3-dithiane (2) has been published.2c In this context,
it should be mentioned that the dithiane ring system has been
modified to 1,3-oxathiane and its synthetic applications have been
described.3
The presence of fluorine, trifluoromethyl and trifluoromethylthio
groups contributes significantly towards the enhancement of the bi-
ological potency and effectiveness of active compounds.4,5 This ob-
servation has created considerable interest in the development of
methodologies to incorporate the previously mentioned functional
groups into the molecular architecture of biologically active com-
pounds. In continuation of our interest in the chemistry of the
trifluoromethylthio group,6 attempts were made to synthesize new
potential candidate compounds, in particular 2-(trifluoromethylthio)-
1,3-dithiolane and -dithiane. This expectation was based on the use
of N-(trifluoromethylthio)phthalimide in trifluoromethylthiolating car-
bonyl compounds.7 These sulfur-stabilized trifluoromethylthiolated
compounds were considered to be of particular interest and use as
synthetic intermediates. The reaction of 1,3-dithiane (2) with trifluo-
romethylsulfenyl chloride (3) at −78◦C was first examined. The GC-
MS analysis of the reaction mixture enabled the characterization of
eight compounds present in the reaction product. Thus, the structures
of compounds 4 through 8 (Figure 1), have now been deduced from the
examination of their mass spectral fragmentation behavior (Table I).
The reaction of 2-lithio-1,3-dithiane (12) with trifluoromethylsulfenyl
chloride (3) (Figure 2) and bis-(trifluoromethyl) disulfide (4, Figure 3)
was also investigated in this context. A detailed NMR study of the
primary product of the first reaction, namely of 1-(chloromethylthio)-
FIGURE 1 Products from the reaction of 1,3-dithiane with F3CSCl.

Trifluoromethylthiolation of 1,3-Dithiane
307
TABLE I Mass Spectral Fragmentation of Compounds Cited in
Figures 1 and 2
1. Bis-(trifluoromethyl)disulfide (4): M+ = 202, (t = 1.26 min, 0.6%)
2. 1,3-dithialane (9): M+ = 106, (r.t. = 4.20 min, 5.2%)
3. 1,3-dithialane (2): M+ = 120, (r.t. = 5.47 min, 8.9%)
4. (Dichlorofluoromethyl)(trifluoromethyl)disulfide(13): M+ = 234, (r.t. = 2.07 min,
0.2%)
5. Butyl(trifluoromethyl)disulfide (14): M+ = 190, (r.t. = 234 min, 3.2%);
134(M-C4H8);114 (CF2S2); 89(SC4H9);78 (CH2SS); 69(CF3, 100%); 64 (SS);
61(SC2H5) and 60 (C2H4S)
6. 1-methylthio-3-(trifluoromethylperthiyl)propane (10): M+ = 222 (not seen), (r.t. =
ꢀ
4.27 min, 0.5%); 121 (M-SCF3 100%); 93(121-C2H4);78(93-CH3); 73(SC3H5)· 69(CF3);
59(C3H3S); 47(SCH3) and 45(CSH)
7. 1-(trifluoromethylperthiyl)-2-[(trifluoromethylthio)methylthio]ethane (5): M+ = 308,
(r.t. = 729 min, 34.1%); 239 (M CF3); 207 (M-SCF3, 100%); 147 (207-SC2H4); 133
(F3CSS); 115 (CH2SCF3); 106 (C3H6SS);82 (CSF2);78(CH2SS); 73 (SC3H5); 69 (CF3)
and 64 (SS)
8. 1-ethylthio-3-(trifluoromethylperthiyl)propane (11): M+ = 236 (not seen) (r.t. =
610 min, 0.3%); 207(M-C2H5); 136(M-SCF3); 107(135-C2H4, 100%); 103(135-S);
78(CH2SS);73(SC3H5); 69(CF3) and 64(SS)
9. 1-(trifluoromethylperthiyl)-3-[(trifluoromethylthio)methylthio]propane(7): M+ = 322,
(r.t. = 829 min, 0.5%); 221(M-SCF3, 100%); 147(SCH2SCF3 or
CH2SSCF3);115(CH2SCF3); 106(C3H6SS); 78(CH2SS); 73(SC3H5) and 69
(CF3);64(SS), 61(C2 H5S);50(CF2) and 45(CSH)
10. 1-chloromethylthio-3-(trifluoromethylperthiyl)propane (6A): M+ = 256, (r.t = 9.53
min, 24.8%); 221(M-SCF3); 207(M-CH2Cl);175(207-S); 155(M-SCF3, 100%);
147(CH2SSCF3); 106(C3H6SS); 101(SCF3);95(CS2F);82(CSF2); 78(CH2SS);
73(SC3H5);69(CF3), 64(SS) and 61(C2H5S)
11. 2-(trifluoromethylthio)-1,3-dithiane(1): M+ = 220(r.t. = 8.05 min, 0.7%);
151(M-CF3);119 (M-SCF3, 100%); 105(C3H5SS);85; 78(CH2SS); 73(SC3H5);
69(CF3);59(C2H3S) and 45 (CSH, 100%). 146(M-SC3H6);119(M-SCF3’
100%);102(CF3SH);91(119-C2H4);82(CSF2); 75(C3H7S), 69(CF3); 59(C2H3S) and
(CSH)
12. Bis-1,3-(chloromethylthio)propane (8): M+ = 204(r.t. = 10.37 min,
0.8%);169(M-Cl);155 (169-CH2); 120(155-Cl);87(C4H7S); 73(SC3H5); 64(SS),
49(CH2Cl) and 45(CSH)
13. (Trifluoromethylperthiyl)butylthione (15): M+ = 234 (not seen) (r.t. = 3.35) min,
0.9%); 215 (M-F);183(215-S);133 (F3CSS);69 (CF3);64 (SS) and 57(C4H9, 100%)
3-(trifluoromethylperthiyl)propane (6A), was carried out to ascertain
its structure. For the comparison of its NMR spectral characteristics
and to examine the course of the reaction of 3 with 1,3-dithiane (2),
(chloromethyl) propyl sulfide and bis-(propylthio)methane were synthe-
sized. The NMR and GC-MS spectral identification of the various com-
pounds and the probable mechanism of their formation are described
in this article.

308
S. Munavalli et al.
FIGURE 2 Products from the reaction of 2-lithio-1,3 dithiane with F3CSCl.
RESULTS AND DISCUSSION
Simple ab initio calculations on the α-thio carbanions have shown the
involvement and participation of the induced polarization.8a Later cal-
culations have indicated significant contribution of the d-orbitals to the
reactivity of the α-thio carbanions.8b The stability of the carbanions
derived from dithiane has been examined in detail9a and the concept
of the back donation of electrons into the vacant d-orbitals has been
advanced to account for their observed unusual stability.9b The flank-
ing sulfur atoms have been suggested to be responsible for the marked
stabilizing effect on the carbanion.9c
2-chloro-1,3-dithiane has been prepared via the reaction of 1,3-
dithiane (2) with N-chlorosuccinimide10a and sulfuryl chhloride,10b re-
spectively, and its reactions have led to interesting compounds.10b
The use of lithio-1,3-dithianes has been discussed in detail.11 While
the reaction of 2-lithio-1,3-ditihane (12) with nitriles furnishes car-
boxylic acid derivatives,12a the same reagent with nitrile oxides
gives α-diketones.12b The reaction of 2-lithio-2-trimethylsilyl-, 2-lithio-
2-trimethylstannyl-, and 2-lithio-2-trimethylgermanyl-1,3-dithianes
FIGURE 3 Reaction of lithio-dithiane with bis-(trifluoromethyl)disulfide.

Trifluoromethylthiolation of 1,3-Dithiane
309
with acylchloride has been reported to furnish, in addition to 2-
acyl-1,3-dithianes, the thiane ring cleavage prodcuts, namely bis-1,3-
dithia-acylpropane.13 The reaction of 2-alkyl-2-lithio-1,3-dithiane with
bis-(methyl)disulfide has been stated to yield 2-alkyl-2-methylthio-
1,3-dithaine.14 The treatment of 2, 2-diaryl-1,3-dithiolanes and -1,3-
dithianes with n-BuLi has been observed to induce the cleavage of
the heterocyclic ring.15a 1,3-dithiolane (9) has been employed in the
preparation of secondary mercaptans and sulfides.15b However, the re-
action of the thioketals with n-BuLi at 0◦C has been reported to yield
thioketones.15c Anion-induced gas phase deprotonation has also been
described to result in the cleavage of the dithiane system and to form
1-allylthiomethylthiyl anion intermediate.16 Thus, the facile fission of
the ring and the ease of the formation of the products have contributed
to the populairty of 2.
With a view to synthesize 2-trifluoromethylthio-1,3-dithiane (1),
dithiane (2) was reacted with trifluoromethylthiocopper and found
to yield ring cleaavage products 7, 17, and 18 along with bis-
(trifluoromethyl) disulfide (4, Figure 4).17 In addition to the above,
compound 2-methyl-1,3-dithiane (16) was also detected. Next, the
reaction of dithiane (2) with with trifluoromethylsulfenyl chloride
(3) was examined and the following compounds were characterized
by GC-MS analysis: (1) 1,3-dithiane (2), (2) 2-(trifluoromethylthio)-
1,3-dithiane (1), (3) 1,3-dithiolane (9), (4) bis-(trifluoromethyl)disulfide
(4), (5) 1-(trifluoromethylperthiyl)-2-(trilfluoromethyl-thiomethylthio)-
ethane (5), (6) 1-(trifluoromethylperthiyl)-3-(trifluoromethylthio-
methylthio)propane (7), (7) 1-(chloromethylthio)-3-(trifluoromethyl-
perthiyl)-propane (6A) or 1-chloro-1-(trifluoromethylthio)-1,3-dithiane
(6B), (8) bis-1,3-(chloromethylthio)propane (8), (9) 1-methylthio–
3-(trifluoromethylperthiyl)propane (10), and (10) 1-ethylthio–3-
(trifluoromethylperthiyl) propane (11). The major product (92.5%) of
the reaction, based on the GC-MS analysis, was found to be either
FIGURE 4 Compounds from the reaction of 1,3-dithiane and CF3SCu.

310
S. Munavalli et al.
6A or 6B with M+ = 256. The reaction mixture was then subjected
to vacuum distillation to remove more volatile materials. The residue
was then distilled under high vacuum and each fraction was carefully
collected at every 2◦C rise in the temperature. This furnished a highly
pure fraction (95%) according its 13C-NMR spectrum.
A priori, there was no reason to consider 6A as the primary candidate
for this compound. The mass spectral fragmentation, although helpful
in arriving at the molecular formula, did not lead to any definitive con-
clusion about its structure. During the past several years, many inno-
vative modifications of the NMR have been fruitfully employed in deci-
phering the structure of complex organic molecules. In this context, it is
worth mentioning that 13C-NMR spectra have been found to be of con-
siderable help in the study of conformational equilibiria of 1,3-dithiane
derivatives.18 Various polarization transfer NMR techniques such as In-
sensitive Nuclei Enhancement by Polarization Transfer (INEPT),19a,b
Distortionless Enhancement by Polarization Transfer (DEPT),19c At-
tached Proton Test (APT),19d and two-dimensional 13C 1H polariza-
tion J transfer spectroscopy, etc. have been introduced to gain precise
information on the structure and stereochemistry of complex organic
molecules.
The last one is a modification of the clssical INEPT NMR procedure
and permits the application of two-dimensional 13C J spectroscopy to
determine long range coupling.19e Another modifcation of the INEPT
technique, called Insensitive Nuclei Attached Proton Test (INAPT),
which makes use of soft pulses, has been stated to furnish useful
information.19e
The probable mechanism of the formation of compounds 28, 33, 35–
38 and 46 is given in Figure 10. Encouraged by the reported results
of the INAPT techniques, it was considered interesting and useful to
apply this technique to examine the structure of 6A or 6B. In fact
we considered 6B as our first choice for this compound. This assump-
tion was based on the reported characterization of 9-chloro-9-methyl-9-
thiabicyclo[6.1.0]nonane and σ-sulfurane (48 and 49, cf. Figure 11).20
If this assumption was correct, then 6B should exhibit “through space”
13C- and 1H-interactions and as such should show δ-vales resulting from
the interactions between various carbon and hydrogen atoms. These
changes should then be observable through the INAPT measurements.
If the compound in question possessed the acyclic or linear structure,
namely 6A, then no such interactions should be observed. The INAPT
measurements did not show any through-space interactions. This led
us to assign structure 6A to this compound. This inference stands sup-
ported by the following evidence: (i) The 1H-chemical shifts of the CH2Cl
moieties of the 6A and (chloromethyl)propyl sulfide (28, also cf. 6c and
6d, Figure 11) are almost identical; (ii) low temperature measurements

Trifluoromethylthiolation of 1,3-Dithiane
311
showed no evidence of conformational isomers at −50◦C and hence, no
axial and equatorial type resonance “freeze out” was observed; (iii) long-
range coupling experiment showed no coupling between carbon at δ 49.3
and protons at δ 2.96 nor any coupling between the protons at δ 4.71 and
the carbon at δ 38.0; and (iv) all the couplings observed were found to
1
be consistent with the acyclic structure, namely 6A. The H-chemical
shift of S CH2 S of 2 appears at δ = 3.78 ppm.21a Additional NMR
support for 6A compares very well with the reported 1H-chemical shift
of −CH2Cl of (chloromethyl)methyl sulfide (δ = 4.71 ppm).21b
Because the reaction of 1,3-dithiane (2) in dry pentane at −78◦C
under dry N2 with trifluoromethylsulfenyl chloride (3) furnished
the desired compound, namely 2-(trifluoromethylthio)-1,3-dithiane (1),
in poor yields, two additional approaches were explored. First, 2-
lithio-1,3-dithiane (12) was prepared by reacting 2 with n-BuLi
at −78◦C and then reacted with bis-(trifluoromethyl)disulfide (4)
sucked in via the vacuum line. The workup of the reaction mix-
ture and the GC-MS analysis showed the presence of three main
products: 2 (86.9%); 1,3-dithiolane (9), and 1 (8.2%). Second, the
lithium-salt (12) was directly exposed to 3, sucked in via the vac-
uum line at −78◦C. The routine processing of the reaction mixture
followed by the GC-MS analysis indicated the reaction mixture to
consist of 11 components: (1) bis-(trifluoromethyl)disulfide (4, M+
=
202, 0.4%), (2) 1,3-dithiolane (9, M+ = 106, 2.5%), (3) 1,3-dithiane (2,
M+ = 120, 0.3%), (4) 1-[(trifluoromtheylthio)methylthio]-2-(trifluoro-
methylperthiyl)-ethane, (5, M+ = 308, 36.2%), (5) 2-(trifluoromethy-
lthio)-1,3-dithiane (1, M+ = 220, 10.1%), (6) 1-ethylthio-3-(trifluoro
-methylperthiyl)propane (11, M+ = 236, 12.7%), (7) 1-[(trifluoro-
methylthio)methylthio]-3-(trifluoromethylperthiyl)propane (7, M+
=
322, 0.5%); (8) 1-(methylthio)-3-(trifluoromethylperthiyl) propane, (10,
M+ = 222, 0.5%); (9) (dichlorofluoromethyl)(trifluor methyl)disulfide),
(13, M+ = 234, 0.2%), (10) butyl (trifluoromethyl)disulfide (14, M+
=
190, 3.2%) and 1-(chloromethylthio)-1-3-(trifluoromethylperthiyl)pro-
pane (6, M+-256, 0.4%).
Figure 1 describes the products formed from the reaction of 2 with
3. Bis-(tri-fluoromethyl)disulfide (4) arises from the dimerization of the
F3CS.-radical (cf. Eq. (2) Figure 5) while 2 is the substrate itself. The
origin of the ring contraction product, namely 1,3-dithiolane (9), has
been rationalized.17 The reaction of F3CS.-radical with 1,3-dithiolane
(9) gives intermediate 20, which goes on to react with F3CS. to form com-
pound 5. The attack by the chloromethyl radical (cf. Eq. (7) Figure 5)
on 2 results in the intermediate 21, which joins up with Cl. to give com-
pound 8. The abstraction of hydrogen from the C2-position by Cl. leads to
22, which then reacts with F3CS. and furnishes 2-(trifluoromethylthio)-
1,3-dithiane (1). If, on the other hand, F3CS. attacks the sulfur atom

312
S. Munavalli et al.
FIGURE 5 Mechanism of formation of compounds cited in Figures 1 and 2.
of 2, then that would give intermediate 23, which has three options
open to it. First, it can simply react with Cl. to yield the primary
product of the reaction, namely 6A. Second, it can react with F3CS. to
form compound 7. Third, it can simply abstract hydrogen from the sol-
vent to give 1-methylthio-3-(trifluoromethylperthiyl)propane (10). The
methyelene insertion between the C S bond of 10 gives 1-(ethylthio)-3-
(trifluoromethylperthiyl)propane (11). All of the previously mentioned
compounds have been characterized by their mass spectra (Table I).
It was surprising to see a similar distribution pattern of prod-
ucts arising from the reaction of 2-lithio-1,3-dithiane (12) with

Trifluoromethylthiolation of 1,3-Dithiane
313
3. It is interesting to note that two more compounds, namely
(dichlorofluoromethyl)(trifluoromethyl)disulfide (13) and butyl (triflu-
oromethyl)disulfide (14), are formed in this reaction. The formation of
13 from 3 has been previously described,6d while Eqn. 9 (Figure 5) ex-
plains the formation of compound 14.
In view of the reported facile formation of 2-methyl-1,3-dithiane (16)
from the reaction of 2-lithio-1,3-dithiane (12) with dimethyl disulfide,22
it was hoped that the reaction of 12 with 4 would lead to satisfactory
yields of 1. Accordingly, the reaction was carried out and the partial
results thus obtained from this reaction are shown in Figure 3. Three
more compounds present in the reaction product could not be identified
as they undergo extensive degradation in the mass spectrometer with-
out recording their M+-ion peaks. However their partial mass spectra
show the presence of the C4H9and F3CS groups. The formation of com-
pound 14 has already been discussed. The source of the butyl moiety is
the butyl lithium used to generate the lithio-derivative (12) of 2. Figure
6 attempts to explain the probable mechanism of the formation of com-
pounds 14 and 15. Compound 14 is also formed in the reaction of 12
with 3 (cf. Figure 2). Compound 16 owes its origin to compound 1 and
its formation appears to be somewhat much more involved. Loss of the
F3C.-radical from 1 gives the sulfur radical intermediate (cf. Figure 6),
which undergoes the thiane ring cleavage to form intermediate 24 and
fragments off the C3H6S moiety to furnish radical 25, which in turn re-
acts with F3CS. to give intermediate 26. The latter splits off hydrogen
to form 27, which joins up with the .C4H9 radical to give 15.
While preparing (chloromethyl)propyl sulfide (28), bis-(propylthio)
methane (29) was formed as a major product, about 66.0% (cf. Figure 7).
A couple of vacuum distillation gave a highly pure product by G.C.,
which was found by GC-MS to be more than 99.0% pure. It was consid-
ered interesting to examine whether its reaction with 3 would lead to
compounds containing the ‘trifluoroperthiyl’ (F3CSS.) moiety. Accord-
ingly the reaction was conducted under similar conditions as used in
the reaction of 2 with 3 except that anhydrous diethyl ether was used as
a solvent, instead of pentane. The GC-MS analysis of the reaction mix-
ture showed the presence of 8 compounds including the substrate (Fig-
ure 8): (1) (chloromethyl)propyl sulfide (28), (2) bis-(propylthio)methane
(29), (3) bis-(propyl)disulfide (33), (4) (2-chloroethyl) ethyl ether (35), (5)
[(propylthio)methyl](trifluoromethyl)disulfide (36), (6) (dichlorofluoro-
methyl)(trifluoromethyl)disulfide (13), (7) (propyl)(trifluoromethyl)
disulfide (37), and (8) (chloromethyl)(propenyl)disulfide (38).
Figure 9 explains the formation of 7 compounds formed dur-
ing the preparation of bis-(propylthio)methane (29). To begin with,
(chloromethyl)propyl sulfide (28) undergoes free radical dissociation to

314
S. Munavalli et al.
FIGURE 6 Formation of products from reaction of lithio-dithiane with
F3CSSCF3.
form three pairs of radicals: (i) propyl and chloromethylthiyl, (ii) propy-
lthiyl and chloromethyl, and (iii) propylthiomethyl and chlorine radi-
cals. The combination of propylthiomethyl and propylthiyl would result
in bis-(propylthiyl)methane (29). When propylthiyl radical dimerizes,
it yields bis-(propyl)disilfide (33). When it simply abstracts hydrogen, it
forms propyl mercaptol (30). This can also arise from the hydrolysis of
FIGURE 7 Preparation of bis-(propylthio) methane.

Trifluoromethylthiolation of 1,3-Dithiane
315
FIGURE 8 Products from the reaction of bis-(propylthio)methane with
F3CSCI.
the sodium salt of propyl mercaptol (30) used as reagent in the reaction.
Abstraction of hydrogen by a Cl. radical from 29 leads to intermediate
39, which can also be formed by the abstraction of the α-hydrogen,
followed by successive hydrogen migrations to form 39. Whether the
initial abstraction of hydrogen occurs at the α-methylene moiety of 29
or γ -methylene group cannot be definitely stated. In this context it has
been said that the “consideration of the acidity of α-hydrogens does
not, however, explain the directive effects in the chlorination of aikyl
sulfides.23a In addition, “internal competition of hydrogen abstraction”
FIGURE 9 Compounds from the reaction of H7C3SCH2SC3H7 with F3CSCIl.

316
S. Munavalli et al.
may be playing some part in the chlorination of unsymmetrical alkyl
sulfides.23b As stated earlier, it is also possible that the initially formed
radical may undergo successive hydrogen migrations before forming
the final product.
.
The intermediate 39, on reacting with CH2Cl, forms (4-chloro
butylthio)(propylthio)methane (40), which fragments off Cl. and gives
intermediate 41. This intermediate simply abstracts hydrogen to
furnish (butylthio)(propylthio)methane (34). This has two options open
to it. First, 34 splits off (propylthio)methyl moiety and forms butylthiyl
radical (42), which goes on to abstract hydrogen and to yield butyl
mercaptol (31). Second, 34 can fragment off the propylthio entity to
generate intermediate 43, which after abstraction of hydrogen gives
butyl methyl sulfide (32). The GC-MS identification of the compounds
previously described lends credence to the proposed mechanism
(cf. Table II).
Figure 10 endeavors to rationalize the formation of the compounds
formed during the reaction of bis-(propylthio)methane (29) with F3CSCl
(3) (cf. Figure 8). Bis-(propylyhio)methane (29) undergoes free rad-
˙
˙
ical fragmentation to H7C3SCH2 and SC3H7 radicals. The latter re-
˙
acts with F3CS, which is itself formed from the free radical dissoci-
ation of F3CSCl (3) and gives (propyl)(trifluoromethyl) disulfide (44),
which extrudes sulfur to form (propyl)(trifluoromethyl)sulfide (37),
˙
while H7C3SCH2radical has two options available to it. Firsty, it can
react with Cl. to give (chloromethyl)propyl)sulfide (28). Second, the
(propylthio)methyl radical can react with tirlluoroperthiyl (F3CSS.)
[cf. Eq(3)] to form (propylthio)-(trifluoromethylperthiyl)methane (36).
That (chloromethyl)propyl sulfide (28) is a product of the reaction was
confirmed by its absence in the substrate (29) via GC-MS analysis.
Compound 28 dissociates to generate the propylthiyl radical and
chloromethyl radicals, respectively. The propylthiyl radical simply
dimerizes to form the di-sulfide (33). Bis-(propyl)disilfide (33) again
has two options open to it. First, it can slit off a propyl radical to
˙
form propylperthiyl radical (47), which joins up with CH2Cl and gives
(chloromethyl)(propyl)disulfide (38). Second, 33 can undergo hydrogen
abstraction by Cl. to form intermediate 45, which after losing hydrogen,
forms (propenyl)(propyl) disulfide (46). Finally, it remains to explain the
origin of (chloroethyl) ethyl ether (35). The primary source for this com-
pound is the solvent, diethyl ether, used in this reaction. Two possible
pathways from diethyl ether to 35 are shown in Eq. (7) (Figure 10). The
first one envisages the abstraction of hydrogen α to the oxygen to give a
radical intermediate, which undergoes hydrogen migration to form the
β-radical, which in turn links up with a Cl. radical to give compound

Trifluoromethylthiolation of 1,3-Dithiane
317
TABLE II Mass Spectral Fragmentation of Compounds Cited in
Figures 7 and 8
1. Propylmercaptol (30): M+ = 76 (r.t. = 0.33 min, 0.1%); 75 (M-H); 73 (75-2H); 70 (C2
H4S); 61 (SC2H5); 58 (SC2 H2); 48 (CH4 S); 47 (CH3S, 100%), 46 (CSH2) and 45 (CSH)
2. Butyl mercaptol (31); M+ = 90 (r.t. = 0.42 min, 0.7%); 75 (M-CH3); 62 (M-C2H4); 61
(M-SC2H5, 100%); 59 (SC2 H3); 57 (C4 H9); 48 (CH4S); 47 (SCH3); 46 (CSH2) and
45(CSH)
3. Butyl methyl sulfide (32); M+ = 104 (r.t. = 1.06 min, 0.1%); 90(M-CH2); 75 (M-C2H5);
71 (86-CH3); 63 (C2H7S); 61 (SC2H5); 60 (C2H4S); 59 (SC2H3); 58 (C4H10); 57
(C4H9); 48 (CSH4); 47 (SCH3 100%); 46 (SCH2) and 45 (CSH)
4. (Chloromethyl) propyl sulfide (28): M+ = 124 (r.t. = 1.55 min, 326%); 95(M-C2 H5);
89 (M-C1, 100%); 82 (M-C3H5); 75 (89-CH2);73 (C3H5S); 61 (SC2H5); 59 (SC2H3); 49
(CH2Cl); and 45 (CSH)
5. Bis-(propyl)disulfide (33):M+ = 150 (100%); (r.t. = 3.41 min, 0.3%); 108 (M-C3H6);
79(108-C2H5); 73 (C3H5S);66 (H2S2);64 (SS); 59(C2H3S); 47 (SCH3) and 45 (CSH)
6. Bis-(prpopylthio)methane (29); M+ = 164: (r.t. = 5.46 min, 66.2%), 122 (M-C3H6);
117 (M-SCH3); 89 (M-SC3H7, 100%); 79 (CH3S2); 76 (CS2 or C3H7SH); 61 (SC2H5);
55 (C4H7); 49 (C2H3S); 47 (SCH3,) and 45 (CSH)
7. (Butylthio)(propylthio)methane (34):M+ = 178; (r.t. = 7.27 min, 0.1%);136 (M-C3H6);
103 (M-SC3H7);94 (136-C3H6); 89(C4H9S);74 (89- CH3);61 (SC2H5, 100%); 47
(SCH3,); and 45 (CSH)
8. C2H5OCH2CH2Cl(35): M+ = 108;r.t. = 0.3 min, 0.4%); 93 (M-CH3); 79(M- C2H5);63
(CH2CH2Cl); 59(C2H5OCH2, 100%); and 49 (CH2Cl)
9. (Dichlorofluoromethyl)(trifluoromethyl)disulfide (13); M+ = 234; r.t. = 1.20 min,
6.2%)
10. (Trifluoromethyl) propyl sulfide (37) : M+ = 176; r.t. = 2.06 min, 48.6%) ; 157 (M-F);
147 (M-C2H5); 133 (F3CSS or M-C3 H7); 114 (133-F); 101 (F3CS); 82 (CSF2); 78
(C2H3SF); 75(SC3; 69 (CF3, 100%); 64 (CHSF); 50(CF2) and 45 (CSH)
11. (Chloromethyl) propenyl disulfide (38): M+ = 156; r.t. = 2.59 min, 0.4%); 119 (M-Cl);
95 (C2H4 ClS); 89 (C2HS2);81 (CSCl), 79 (C2H2S2, 100%); 73 (C3H5S); 61 (C2H5S); 49
(CH2Cl) and 46 (CSH2)
12. [(Propylthio) methyl](trifluoromethyl)disulfide (36): M+ = 222; r.t. = 3.10 min,
1.1%; 193 (M-C2H5); 153 (M-CF3); 89 (C3H7SCH2, 100%); 73 (C3H5S); 69 (CF3);
61(C2H5S) and 47 (SCH3)
35. The formation of such a free radical α to oxygen of the ethers has
previously been suggested.24 An alternate possibility involves the free
radical cleavage of ether into ethyl and ethoxy radicals. The latter
would then react with a chlormethyl radical to yield chloromethyl
ethyl ether as an intermediate, which undergoes methylene insertion
between C Cl to form 35. There is precedence for the suggested
methyelene insertion.25 That this compound is (2-chloroethyl) ethyl
ether (35) is confirmed by the presence of the molecular ion, the chlo-
rine isotope peaks and the ion m/e = 49 (CH2Cl) in its mass spectrum
(cf. Table II).

318
S. Munavalli et al.
FIGURE 10 Compounds from the reaction of H7C3SCH2SC3H7 with F3CSCl.
FIGURE 11 Structure of the primary product of the reaction of dithiane with
F3CSCl.

Trifluoromethylthiolation of 1,3-Dithiane
319
The results described in Figures. 1, 2, 3, and 4 clearly demon-
strate the cleavage of the heterocyclic ring system of 1,3-dithiane
(2) under mild experimental conditions. It should be stated here
that there are not too many examples of the cleavage of the 1,3-
dithiane ring system.13,15,24 Although the reaction of 1,3-dithiane
with SOCl2 leaves intact the ring system, its reaction with
SO2Cl2 has been reported to give an acyclic product.24 The reac-
tion of 2,2-disubstituted-1,3-dithiolane with Py-(HF)x in the pres-
ence of dibromodimethylhydantoin has been reported to cleave
the dithialane ring and to yield ethyl 1,2-sulfenyl dibromide and
difluoroalkanes.25 The reaction has been suggested to proceed via the
initial attack on sulfur, followed by the cleavage of the dithiolane
ring.
The mass spectra of sulfides show interesting behavior. For exam-
ple, the molecular ion of di-i-propyl sulfide has been described to form
dimeric species with its own precursor26 and the formation of a two-
center three-electron S S bond.26 The loss of the CH3, SH, CH2S,
CH3S, and C3H7S moieties from the molecular ion was seen in the
mass spectral breakdown of 1,3-dithiane. The expulsion of these en-
tities involves a variety of cleavages and hydrogen migrations. A de-
tailed examination of the mass spectral breakdown of 1,3-dithiane us-
ing labeled substrates has appeared.26 FAB and CI-induced as well as
collision-induced dissociation of dithiane fragmentation has also been
investigated.14 The mass spectral breakdown behavior of 1,3-dithiane
(2) and 2-methyl-1,3-dithiane (16) has been investigated with deu-
terium labeling in various positions.26 1,3-dithiane on ionic impact pro-
duces ions with m/e = 105, 87, 74, 55, 46 and 45. On the other hand,
2-methyl-1,3-dithiane (16) furnishes peaks at m/e = 119, 105, 87, 74
and 60, corresponding to the loss of the CH3, C2H5, SCH3, C2H4S and
C3H6S moieties respectively. Also observed is the loss of S2H and SH
fragments.
The most prominent peak (m/e = 155) in the mass spectrum
of 6A arises from the loss of the SCF3-fragment (M SCF3). The
presence of chlorine in the molecule can be inferred by the pres-
ence of the chlorine isotope peaks with intensities in proportion
to their natural abundance. This was seen in all compounds con-
taining chlorine. Other interesting peaks occurred at m/e = 106,
95, 82 (CSF2), 73, 69 (CF3); 64 (SS), 61 (C2H5S), and 45 (CSH).
The mass spectral breakdown of bis(trifluoromethyl)disulfide (4)
and (dichlorofluoromethyl)(trifluoromethyl)disulfide has been pre-
viously discussed.4a,6d The mass spectral fragmentation of the
compounds cited in the narrative is described in Tables I and
II.

320
S. Munavalli et al.
Experimental
Mass spectra were obtained using a Finnigan TSQ-7000 GC/MS/MS
equipped with a 30 m × 0.25 mm. i.d. DB-5 capillary column (J and
W Scientific, Folsom, CA) or a Finnigan 5100 GC/MS equipped with a
15 m × 0.25 mm. i.d. Rtx-5 capillary column (Restek, Bellefonte, PA).
The conditions on 5100 were as follows oven temperature, 60–270◦ C at
10◦C/min; injection temperature, 210◦C, interface temperature 230◦C;
electron energy 70 eV; emission current, 500 µ A; and scan time, 1 s.
The conditions on the TSQ-7000 were as follows: oven temperature,
60–270◦C at 15◦C/min, injection temperature, 220◦C, interface temper-
ature, 250◦C; source temperature, 150◦C, electron energy, 70 eV (EI) or
200 eV (CI); emission current, 400 µA (EI) or 300 µA (CI); and scan time,
0.7 s. Data was obtained in both the electron ionization mode (range
45–450 da) and chemical ionization mode (mass range 60–450 da).
Ultrahigh-purity methane was used as the CI agent gas with a source
pressure of 0.5 Torr (5100) or 4 Torr (TSQ-7100). Routine GC analyses
were accomplished with a Hewlett-Packard 5890A gas chromatograph
equipped with a J and W Scientific 30 m × 0.53 mm i.d. DB-5 col-
umn (J and W Scientific, Folsom, CA). NMR spectra (13C and 19F) were
recorded in CDCl3 on a Varian VXR spectrometer at 100 MHz and 376
MHz, respectively. The external reference for 19F spectra was CFCl3.
Reaction of 1,3-dithiane (2) with trifluoromethylsulfenyl
chloride (3)
A stirred solution of 1,3-dithiane (2) in dry pentane was treated at
−78◦C under argon with stoichiometric amounts of trifluoromethyl-
suflenyl chloride (3) sucked in through the vacuum line. The reaction
mixture was stirred for 2 h at −78◦C. The usual processing of the
reaction mixture gave a colorless homogeneous liquid. Because its
gas chromatograhic analysis showed the presence of a complex
mixture of several components, it was analyzed via GC-MS and
found to contain the following compounds: (1) 1,3-dithiane (2), (2) 2-
(trifluoromethylthio)-1,3-dithiane (1), (3) 1,3-dithiolane (9), (4) bis(tri-
fluoromethyl)disulfide (4), (5) 1-(trifluoromethylperthiyl)-2-(trifluoro-
methylthiomethylthio)ethane (5), (6) 1-(trifluoromethylperthiyl)-3-(tri-
fluoromethylthiomethylthio)propane (7), (7) 1-(chloromethylthio) 3-(tri-
fluoromethylperthiyl)propane (6A) or 1-chloro-1-(tri-fluoromethylthio)-
1,3-dithiane (6B), (8) bis-1,3-chloromethylthio)propane (8), (9) 1-
methylthio-3-(trifluoromethylperthiyl)propane (10), and (10) 1-ethyl-
thio-3-(trifluoromethylperthiyl)propane (11). The major product
(92.5%) of the reaction based on the GC-MS analysis was found

Trifluoromethylthiolation of 1,3-Dithiane
321
to be 6A with M+ = 256. The reaction mixture was then sub-
jected to vacuum distillation to remove volatile materials. The
residue was then distilled under high vacuum and each frac-
tion was carefully collected at every 2◦C rise in the tempera-
ture. This furnished a highly pure fraction (96% according to
NMR): δ-values of 6A: 13C NMR: SCF3 [129.3; (JCF = 314 Hz);
CH2SSCF3 (38.0); SCH2CH2 (27.3); SCH2CH2CH2SSCF3 (29.8);
and SCH2Cl (49.3). 1H: -CH2SSCF3(2.96) [t, JHH = 7.0 Hz, JHF = < 0.6
Hz]; -SCH2 CH2CH2 [2.07 (m, 2H)]; SCH2CH2CH2SSCF3 [2.84 (t,
JHH = 7.2 Hz) and SCH2Cl (s, 4.71).
Reaction of 2-lithio-1,3-dithiane (12) with
trifluoromethylsulfenyl chloride (3)
To a suspension of 1,3-dithiane (2, 1.2 g, 0.0l mole) in freshly dis-
tilled dry tetrahydrofurane (15 mL) cooled to −78◦C, a solution of
n-BuLi in pentane (6.8 mL, 2M) under nitrogen was added drop-
wise over 30 min and the mixture was stirred for 2 h at −78◦C.
To this cold solution, was added stoichiometric amounts of trifluo-
romethylsulfenyl chloride (3) sucked in through the vacuum lime.
The whole was stirred for 2 h at −78◦C. It was allowed to come
to an ambient temperature. After the routine processing of the re-
action mixture and its GC-MS analyis, the presence of the follow-
ing compounds was detected: (1) 1,3-dithiane (2), (2) 1,3-dithiolane
(9), (3) bis-(trifluoromethyl)disulfide (4), (4) 2-(trifluoromethylthio)-1,3-
dithiane (1), (5) 1-ethylthio-3-trifluoromethylperthiyl)-propane (11),
(6) 1-methythio-3-trifluoromethylperthiyl)propane (10), and (7) 1-
(chloromethylthio)-3-trifluoromethylperthiyl)propane (6A) (Figure 2).
Synthesis of (Chloromethyl) Propyl Sulfide (28, Figure 7)
Dry hydrogen chloride gas was bubbled through a solution of propyl
mercaptol and paraformaldehyde in dry methylene chloride at −78◦C
until all the paraformaldehyde got dissolved. The reaction mixture was
stirred for an additional hour and left aside for 24 h. The organic layer
separated, and the usual processing of the reaction mixture and evapo-
ration of the solvent furnished the desired product (28, 32.00 %)29 and
bis-(propylthio)methane (29, 66.00%). A gas chromatographically ho-
mogeneous sample of 28 was obtained after two vacuum distillations.
It gave the following NMR-data: 13C-NMR: CH3 (13.3), CH2 (21.9),
CH2(33.6) and CH2Cl (49.8), and 1H-NMR: CH3 (1.00), CH2 (1.66), CH2
(2.31), and CH2Cl (4.72).

322
S. Munavalli et al.
Preparation of bis-(propylthio)methane (29)
Stoichiometric amounts of the sodium salt of propyl mercaptol reacted
with (chloromethyl)propyl sulfide (28) in a mixture of i–propanol and
benzene (1:3) at r.t. for 2 h with stirring under nitrogen, then refluxed for
2 h and stirred over night at ambient temperature. The reaction mixture
was treated with cold water and extracted with benzene. The organic
layer was washed with water, followed by saturated solution of brine
dried over anhydrous sodium sulfate and the solvent evaporated under
reduced pressure. The GC analysis of the residue showed it to consist of
at least seven components. However, its GC-MS analysis permitted the
identification of the following compounds: (1) (chloromethyl) propyl sul-
fide (28; (32.3%), (2) bis-(propylthio)methane (29, 66.2%), (3) propylmer-
captol (30, 0.1%), (4) butylmercaptol (31, 0.2%), (5) butyl methyl sulfide
(32, 0.1%), (6) butyl disulfide (0.2%), (7) (buylthio) (propylthio)sulfide
(0.2%), (8) bis-(propyl)sulfide (03%) and bis-(chloromethylthio)methane
(0.1%). After several vacuum distillations, a highly purified sample of
bis-(propylthio)methane (29) was obtained (> 98%) and used in the re-
action with F3CSCl. The NMR δ-values are 1H: SCH2S (s, 3.81), -CH2S
(2.76) and CH2 CH2S (1.97) and CH3-CH2S (1.16). 13C: SCH2S (38. 4),
-CH2S (35.6), and -CH2 CH2S (25.5) and CH3 CH2S (16.5).
Reaction of bis-(propylthio)methane (29) with
trifluoromethylsulfenyl chloride (3)
To a soltuion of bis-(propylthio)methane (29) in freshly distilled dry
anhydrous ether (20 mL) contained in a three-necked flask carry-
ing a reflux condenser, dry-ice attachment, and nitrogen outlet and
cooled to −78◦C was added stoichiometric amounts of trifluoromethyl-
sulfenyl chloride (3) sucked in via the vacuum lime. The whole was
stirred for 4 h at −78◦C. It was allowed to come to ambient temper-
ature. The routine processing of the reaction mixture, and its GC-
MS analyis, led to the identification of the following compounds: (1)
(chloromethyl) propyl sulfide (28), (2) bis-(propylthio)methane (29),
(3) bis-(propyl)disulfide (33), (4) (2-chloroethyl) ethyl ether (35), (5)
(propylthiomethyl)- (trifluoro-methyl)disulfide (36), (6) (dichlorofluoro
methyl)(trifluoromethyl)-disulfide (13), (7) prpopyl (trifluoromethyl)
sulfide (37), and (8) (chloromethyl)-propenyldisulfide (38, cf. Figure 8).
REFERENCES
[1] D. Seebach and E. J. Corey, J. Org. Chem., 40, 231 (1975) and references. cited
therein.

Trifluoromethylthiolation of 1,3-Dithiane
323
[2] (a) B. T. Grobel and D. Seebach, Synthesis, (1977) 357, (b) L. Field, Synthesis 101
(1972); (c) Comprehensive Heterocyclic Chemistry, Vol. 3, ch. 2.26; A. Katritzky and
C.W. Rees (Eds.), (Pergamon Press, New York 1984), pp. 943–994; (d) P. C. Bulman
Page, M. B. van Niel, and P. C. Prodger, Tetrahedron, 45, 7643 (1989); (e) L. F. Tietze,
B. Weiga, and C. Wulff, Synthesis, 69 (2000).
[3] (a) K. Fuji, M. Ueda, K. Sumi, and E. Fujita, J. Org. Chem., 50, 662 (1985); (b)
K. Fuji, M. Ueda, K. Sumi, K. Kajiwara, E. Fujita, T. Iwashi, and T. Miura, J. Org.
Chem., 50, 657(1985).
[4] (a) S. Munavalli, D. I. Rossman, J. W. King, L. L. Szafraniec, W. T. Beaudry and
C. P. Ferguson, Proc. ERDEC Scientific Conf. on Chemical Defense, 1993; (b) S.
Munavalli, D. I. Rossman, D. K. Rohrbaugh, C. P. Ferguson, and L. C. Buettner, J.
Fluorine Chem., 65, 15 (1993).
[5] (a) R. Filler and Y. Kobayashi (Eds.), Biomedicinal Aspects of Fluorine Chemistry,
(Kodash/Elsevier, New York 1982); (b) W. C. Randall, P. S. Anderson, E. A. Cresson,
C. A. Hunt, T. F. Lyon, K. Hoogsteen, M. Williams, E. A. Risley and J. A. Totaro, J.
Med. Chem., 22, 1222 (1979) and references cited there; (c) E. A. Nodiff, S. Lipschutz,
and M. Gordon, J. Org. Chem., 25, 60 (1960); (d) J-P. Belgue and D. Bonnet-Delpon,
Tetrahedron, 47, 3207 (1991); (e) D. J. Burton and Z-Y. Yang, Tetrahedron, 48, 189
(1992); (f) G. A. McClinton, Tetrahedron, 48, 6555 (1992).
[6] (a) S. Munavalli, D. I. Rossman, D. K. Rohrbaugh, C. P. Ferguson and L. J. Szafraniec,
J. Fluorine Chem., 59, 91 1992; (b) S. Munavalli, D. I. Rossman, D. K. Rohrbaugh,
and H. D. Durst, J. Organometal. Chem., 587, 160 (1999); (c) S. Munavalli, A.
Hassner, D. I. Rossman, S. Singh, D. K. Rohrbaugh, and C.P. Ferguson, J. Fluo-
rine Chem.,73, 7 (1995); (d) S. Munavalli, D. I. Rossman, D. K. Rohrbaugh, C.P.
Ferguson, and H. D. Durst, J. Fluorine Chem., 76, 7 (1996); (e) S. Munavalli, D.K.
Rohrbaugh, D. I. Rossman, and H. D. Durst, J. Flourine Chem., 89, 189 (1998); (f)
S. Munavalli, G. W. Wagner, A. Bashir-Hashemi, D. K. Rohrbaugh and H. D. Durst,
Synthetic Comm., 27, 2847 (1997); (g) S. Munavalli, D. K. Rohrbaugh, D. I. Rossman,
W. G. Wagner, and H.D. Durst, Phosphorus, Sulfur, and Silicon, 177, 1021 (2002);
(h) S. Munavalli, D. K. Rohrbaugh, D. I. Rossman, W. G. Wagner, and H. D. Durst,
177, 1073 (2002); (i) S. Munavalli, D. K. Rohrbaugh, D. I. Rossman, H. D. Durst
and A. Dondoni, 177, 2465 (2002); (j) S. Munavalli, D. K. Rohrbaugh, D. I. Rossman,
W. G. Wagner, and H. D. Durst, Phosphorus, Sulfur and Silicon, 107, 1073 (2003);
(k). S. Munavalli, D. K. Rohrbaugh, H. D. Durst, and D. I. Rossman, in Recent De-
velopments in Organometallic Chemistry, Vol. 5, (2003), pp 15; (l) S. Munavalli, D.
K. Rohrbaugh, W.G. Wagner H.D. Durst, and F.R. Longo, Phosphorus, Sulfur and
Silicon, 179, 1635 (2004); (m) S. Munavalli, D.K. Rohrbaugh, D. I. Rossman, F. J.
Berg, and H. D. Durst, Phosphorus, Sulfur and Silicon, 179, 1645 (2004); (n) S. Mu-
navalli, D. K. Rohrbaugh, and H. D. Durst, Phosphorus, Sulfur, and Silicon, 179,
1657 (2004).
[7] S. Munavalli, D. K. Rohrbaugh, D. I. Rossman, F. J. Berg, G. W. Wagner, and H. D.
Durst, Synthetic Comm., 30, 2847 (2000).
[8] (a) A. Streitwieser and S. P. Ewing, J. Am. Chem. Soc., 97, 190 (1975), (b) S. Wolfe, S.
Stowlow, and L. A. LaJohn, Tetrahedron Lett., 24, 4071 (1983) and references cited
therein.
[9] (a) J.-M. Lehn and G. Wipff, J. Am. Chem. Soc., 98, 7498 (1976); (b) A. Krief, Tetra-
hedron 36, 2531 (1980); (c) E. Block, in Reactions of Organosulfur Compounds,
(Academic Press, New York, 1978), pp. 42.
[10] (a) K. Arai and K. Oki, Bull. Chem. Soc. (Japan), 49, 553 (1976); (b) C.G. Kruse,
N. L. J. M. Broekhof, A. Wijaman and A. van der Gen, Tetrahedron Lett., 885
(1977).

324
S. Munavalli et al.
[11] (a) W. D. Wessner, Chem. Lett., 43 (1976); (b) D. Seebach, Angew. Chem. Int. Ed., 18,
239 (1979); (c) A. Katritzsky and C. W. Rees, Comprehensive Heterocyclic Chemistry,
Vol. 3, (Pergamon Press, New York 1984), pp. 943.
[12] (a) P. C. Bullman Page, M. B. van Niel, and D. Westwood, J. Chem. Soc., Perkin
Trans., 1, 269 (1988); (b) T. Yamamori and I. Adachi, Tetrahedron Lett., 21, 1747
(1980).
[13] P. Jutzi and O. Lorey, Phosphorus and Sulfur, 5, 203 (1979).
[14] R. A. Elison, W. D. Waesner, and C. C. Willimas, J. Org. Chem., 37, 2767 (1992).
[15] (a) Y. Kamitori, M. Hoja, R. Matsuda, T. Kimura, and T. Yoshida, J. Org. Chem., 51,
4427 (1986); (b) S. R. Wilson, G. M. Georgiadus, H. N. Khatri, and J. E. Bartness, J.
Am. Chem. Soc., 102, 3577 (1980); (c) S. R. Wilson, P. Caldera, and M. A. Jester, J.
Org. Chem., 47, 3319 (1982).
[16] (a) N. M. M. Nibbering, S. Ingemann, and L. J. de Koning in Supplement S, The
Chemistry of Sulfur Containing Functional Groups, S. Patai and Z. Rappoport (Eds.),
(Wiley and Sons, New York 1993), pp. 310; (b) J. E. Bartness, R. L. Hayes, H. N.
Khatri, R. N. Misra, and S. R. Wilson, J. Am. Chem. Soc., 103, 4746 (1991).
[17] S. Munavalli, D. K. Rohrbaugh, D. I. Rossman, and H. D. Durst (in press).
[18] (a) E. L. Eliel, V. S. Rao, and F. G. Riddell, J. Am. Chem. Soc., 98, 3583 (1976); (b)
K. Pihlaja and B. Bjorkqvist, Org. Magn. Reson., 9, 533 (1977).
[19] (a) P. H. Bolton, J. Magn. Reson., 41, 287 (1980); (b) D. M. Doddrell and D. T. Pegg,
J Am. Chem. Soc., 102, 6388 (1980); (c) J. K. M. Sanders and B. K. Hunters, Modern
NMR Spectroscopy, (Oxford Umiversity Press, New York, 1993); (d) S. L. Patt and
J. N. Shoolery, J. Magn. Reson., 46, 535 (1982); (e) D. M. Thomas, M. R. Bendall,
D. T. Pegg, D. M. Doddrell, and J. Field, J. Magn. Reson., 42, 298 (1981).
[20] (a) G. K. Helmkamp, D. C. Owley; D. M. Barness, and H. J. N. Cassey, J. Am. Chem.
Soc., 90, 1635 (1968); (b) D. C. Owley, G. K. Helmkamp, and M. F. Retting, J. Am.
Chem. Soc., 91, 5239 (1969).
[21] Aldrich NMR Catalog, (a) 1 (1); (b) 1 (1) 439B.
[22] R. A. Ellison, W. D. Woessner, and C. C. Williams, J. Org. Chem., 37, 2757 (1972).
[23] (a) D. L. Tuleen and T. B. Stephens, J. Org. Chem., 34, 31 (1969); (b) D. L. Tuleen,
J. Org. Chem., 32, 4006 (1967).
[24] J. Fossey, D. Lefort, and J. Sorba, Free Radicals in Organic Chemistry, (Wiley and
Sons, New York, 1995), pp. 132; (b) J.M. Tedder, Tetrahedron, 38, 313 (1982).
[25] (a) M. Jones, Jr, and R. A. Moss (Eds.), Carbenes, Vol. 1, (Wiley and Sons, New York
1973); (b) S. Munavalli, R. K. Rohrbaugh, and H. D. Durst, Phosphorus, Sulfur, and
Silicon, 180, 2179 (2005).
[26] C. G. Kruse, N. L. J. M. Broekhof, A. Wijman, and A. Vna der Gen, Tetrahedron Lett.,
885 (1977).
[27] S. C. Sondej and J. A. Katzenellenbogen, J. Org. Chem., 51, 3508 (1986).
[28] (a) J. K. Kim, J. Bonicamp, and M. C. Caserio, J. Org. Chem., 46, 4230 (1981) and
references cited therein; (b) T. Clark, J. Am. Chem. Soc., 110, 1672 (1988); (c) P. M.
W. Gill and L. Radom, J. Am. Chem. Soc., 110, 49312 (1988); (d) J.H. Bowie and P.Y.
White, Org. Mass Spectrom., 6, 317 (1972).
[29] (a) D. L. Tuleen and T. B. Stephens, J. Org. Chem., 34, 31 (1969); H. Bohme, H.
Fischer, and R. Frank, Ber., 81, 54 (1948).