Reduction of thiocarbonyl compounds with lithium diisopropylamide

Article abstract of DOI:10.1002/hlca.201400130

Treatment of 4,4-disubstituted 2-phenyl-1,3-thiazole-5(4H)-thiones with lithium diisopropylamide (LDA; LiNⁱPr₂) in THF at -78° yielded the corresponding 1,3-thiazole-5(4H)-thioles in moderate yields. Sequential treatment with LDA and

Full text of DOI:10.1002/hlca.201400130

Helvetica Chimica Acta – Vol. 97 (2014)
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Reduction of Thiocarbonyl Compounds with Lithium Diisopropylamide
by Andreas Gebert1)a), Marcin Jasin´skib), Grzegorz Mloston´ b), and Heinz Heimgartner*a)
a) Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich
(phone: þ 41446354282; e-mail: heinz.heimgartner@chem.uzh.ch)
b
´
´
´
´
) Department of Organic and Applied Chemistry, University of Łodz, Tamka 12, PL-91-403 Łodz
Dedicated to Professor Hans-Ulrich Reissig, Freie Univeristꢀt Berlin, on the occasion of his 65th birthday
Treatment of 4,4-disubstituted 2-phenyl-1,3-thiazole-5(4H)-thiones with lithium diisopropylamide
(LDA; LiNiPr2) in THF at ꢀ 788 yielded the corresponding 1,3-thiazole-5(4H)-thioles in moderate
yields. Sequential treatment with LDA and MeI under the same conditions led to the 5-methylsulfanyl
derivatives. Similarly, reaction of some cycloalkanethiones as well as diaryl thioketones with LDA and
MeI gave cycloalkyl methyl sulfides and diarylmethyl methyl sulfides, respectively. A reaction
mechanism via H transfer from LDA to the thiocarbonyl C-atom via a six-membered transition state
is proposed for this unprecedented reduction of the C¼S bond.
1. Introduction. – For the synthesis of five-membered S-heterocycles, 1,3-dipolar
cycloadditions with C¼S compounds [1] or S-containing 1,3-dipoles [2] are of
continuing interest. In the past, we have reported on various types of [2 þ 3]-
cycloadditions with 1,3-thiazole-5(4H)-thiones of type 1 (cf. Scheme 1) as a model for
C¼S dipolarophiles [3]. For example, reactions with thiocarbonyl ylides led to
spirocyclic 1,3-dithiolanes [4], diazoalkanes reacted with 1 to give spirocyclic 2,5-
dihydro-1,3,4-thiadiazoles [5], and reactions with azomethine ylides yielded spirocyclic
1,3-thiazolidines [6]. Differently substituted azomethine ylides have been generated in
situ in the presence of 1 by various methods (cf. [7]), such as thermal ring opening of
aziridines [6c][6d] or desilylation of N-[(trimethylsilyl)methyl]amino ethers [6e].
Within these studies, we have also tried to generate the C-unsubstituted N-
methylazomethine ylide according to the protocol of Roussi and co-workers [8]. These
authors reported that the treatment of trialkylamine N-oxides in THF with LDA at 08
in the presence of C¼S dipolarophiles leads to the corresponding [2 þ 3] cycloadducts
(1,3-thiazolidine derivatives). For example, the reaction of trimethylamine oxide (2)
with lithium diisopropylamide (LDA) in the presence of thiobenzophenone or
adamantanethione, respectively, gave the corresponding N-methyl-1,3-thiazolidines 3
(Scheme 1). As a rationalization of the formation of five-membered N-heterocycles,
the dehydration of the N-oxides to give an azomethine ylide as a reactive intermediate
was proposed. Unexpectedly, the analogous treatment of a mixture of the 1,3-thiazole-
5(4H)-thione 1a and 2 with LDA at 08 carried out in our laboratories gave only the
reduction product 4a, and none of the expected cycloadduct could be detected.
1
)
Part of the Ph. D. Thesis of A. G., Universitꢀt Zꢂrich, 2001; present address: F. Hoffmann-La Roche
Ltd., Grenzacherstrasse 124, CH-4070 Basel.
ꢁ 2014 Verlag Helvetica Chimica Acta AG, Zꢂrich

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Helvetica Chimica Acta – Vol. 97 (2014)
Scheme 1
The use of LDA as a strong base in organic synthesis, e.g., for the deprotonation of
CH-acidic compounds, is well-known [9]. Less well known is the use of LDA as a
reducing agent [10], e.g., in the reduction of nitro arenes to the corresponding anilines
and azoxy arenes via a single-electron transfer (SET) mechanism [10a]. Furthermore,
treatment of 4-fluorotoluene (5) with lithium diethylamide (LiNEt2) in Et2O led to a
mixture of the meta- and para-isomers of ethyl(2-tolylethyl)amine, 6, and N,N-
diethyltoluidine, 7, as well as toluene [11] (Scheme 2). The formation of 6 was
rationalized by a hydride transfer from LiNEt2 to the intermediate aryne, followed by
nucleophilic addition of the aryl anion at the formed imine. However, to the best of our
knowledge, there is no hydride transfer reaction of LDA known.
Scheme 2
The aim of the present study was to evaluate the ability of LDA as a hydride-
transfer reagent in thiocarbonyl chemistry.
2. Results and Discussion. – As mentioned above, treatment of a mixture of
equimolar amounts of 4,4-dimethyl-2-phenyl-5(4H)-thione (1a) and trimethylamine
N-oxide (2) in THF at 08 with 3.5 equiv. of LDA led to the corresponding 4,5-dihydro-
1,3-thiazole-5-thiole 4a [12], which was isolated in 40% yield, as the major product.
This surprising result motivated us to investigate reactions of C¼S-containing
compounds with LDA. First, the reaction with 1a was repeated in the absence of the
N-oxide 2 at ꢀ 788 by using 1.6 equiv. of LDA. Under these conditions, only one
product, 4a, was formed, which, after treatment with an aqueous 20% NH4Cl solution,

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933
was isolated in 69% yield. An analogous result was obtained with 2-phenyl-3-thia-1-
azaspiro[4.4]non-1-ene-4-thione (1b; 63% yield of 4b; Scheme 3). This outcome hints
at a carbophilic addition of a hydride ion onto 1, leading to an intermediate thiolate 8.
Therefore, 1a and 1b, respectively, in THFat ꢀ 788 were treated with 1.6 equiv. of LDA.
After stirring for 15 min, 1 equiv. of MeI was added, the mixture was allowed to warm
to room temperature, and then poured onto ice. Usual workup gave the corresponding
5-methylsulfanly derivatives 9a [13] and 9b in 68 and 80% yield, respectively.
Unfortunately, the analogous reactions with 2-benzyl- and 2-(phenylsulfanyl)-1,3-
thiazol-5(4H)-thione, 1c and 1d, respectively, failed.
Scheme 3
With the aim of excluding the possibility that the H-atom at C(5) of the reduction
products 4 and 9 stems from the solvent, the reaction with 1a was repeated in (D8)THF
with freshly prepared LDA, as well as with the commercially available 2m LDA
solution in THF. In both cases, the formed 4a did not contain any D-atom. Therefore,
we concluded that LDA acted as a hydride donor in this reaction.
Encouraged by these results, we attempted to extend the scope of this reduction
process to thioketones. Because of the easier workup and purification, the presumably
formed thiolate should be trapped via methylation. First, two cycloaliphatic thioke-
tones, adamantanethione (10a) [14] and pentacyclo[5.4.02,6.03,10.05,9]undecane-8-thione
(10b) [15], in THF/heptane/ethylbenzene at ꢀ 788 were treated with ca. 1.25 equiv. of
LDA for 10 min. Then, excess MeI was added at the same temperature, the mixture was
stirred for another 10 min, and the reaction was quenched by addition of H2O. The
1
yields of the methyl sulfanyl derivatives 11 were estimated on the basis of H-NMR
spectra of the crude mixture to be in the range of 70 – 80%. After chromatographic
purification, 11a [16] and 11b were obtained in 42 and 47% yield, respectively
(Scheme 4). We propose that the MeS group of 11b is endo-oriented as the result of an
exo-addition, in analogy to other nucleophilic additions with pentacy-
clo[5.4.02,6.03,10.05,9]undecan-8-one [15a][17].
Surprisingly, 1,1,3,3-tetramethylindane-2-thione did not react under the same
conditions, and performing the reaction at ꢀ 408 with 3 equiv. of LDA provided a

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Helvetica Chimica Acta – Vol. 97 (2014)
Scheme 4
complex mixture containing traces of the expected sulfide and numerous by-products.
Similarly, neither di(tert-butyl)thioketone nor 2,2,4,4-tetramethyl-3-thioxocyclobuta-
none did undergo a reaction with LDA. Most likely, steric hindrance is the reason for
the failure.
Next, the reaction with aromatic thioketones was examined. Treatment of
thiobenzophenone (10c) [18] as well as thiodibenzosuberone (10d) [19] with ca.
1.25 equiv. of LDA and subsequent treatment of the initial product with MeI led to the
corresponding methylsulfanyl derivatives. 11c [20] and 11d, respectively (in 52 and
41% yield, resp.; Scheme 4). On the other hand, the analogous reaction of the
hetarylthioketones phenyl(thiophen-2-yl)methanethione (10e) [21] and di(selenophen-
2-yl)methanethione [22] led to complex mixtures of diverse products, and, only in the
case of 10e, the corresponding methylsulfanyl derivative 11e was obtained in a very low
yield (9%). Finally, the reduction of diferrocenylthioketone (10f) was performed
successfully by using 3.2 equiv. of LDA and 6.5 equiv. of MeI. After chromatographic
workup, the hitherto unknown diferrocenylmethyl methyl sulfide 11f was obtained in
37% yield.
9H-Fluorene-9-thione (10g) [18][23] is a prominent representative of aromatic
thioketones, known as a superdipolarophilic agent [2]. However, the attempted
reduction of 10g with LDA failed, and only traces of the desired methylsulfanyl
1
derivative were detected in the crude mixture by H-NMR spectroscopy. The major
product was the known bisfluorenylidene (¼ 9-(9H-fluoren-9-ylidene)-9H-fluorene;
12 [24]; Scheme 5), accompanied by numerous by-products.
As a reaction mechanism for the reduction of thiocarbonyl compounds with LDA,
we propose a hydride transfer via a six-membered transition state A, leading to the
thiolate B and the imine C as a side-product (Scheme 6). This transition state resembles
that of reactions of sterically demanding Grignard reagents with carbonyl compounds
bearing bulky substituents, i.e., D (Scheme 6) [25]. Also the AlMe3-catalyzed asym-
metric MeerweinꢀSchmidtꢀPonndorfꢀVerley reduction of prochiral ketones with

Helvetica Chimica Acta – Vol. 97 (2014)
935
Scheme 5
Scheme 6
iPrOH in the presence of enantiomerically pure BINOL (¼ [1,1’-binaphthalene]-2,2’-
diol) is rationalized by an analogous transition state [26].
3. Conclusions. – The unexpected hydride transfer of LDA proved to be a useful
method for the reduction of 4,4-disubstituted 1,3-thiazole-5(4H)-thiones and non-
enolizable thioketones leading to the corresponding thiols. This is the first observation
of a reaction in which LDA acts as a hydride donor. Although the scope of the reaction
is not fully explored, it is very useful in the series of thioketones. Especially important is
the simple access to diaryl/hetaryl methanethiols, which are of great interest from the
point of view of materials chemistry.
We thank the analytical sections of our institutes for spectra and analyses. Generous gift of a sample
´
´
of di(ferrocenyl)thioketone by Dr. Rafał Karpowicz (University of Łodz) is acknowledged. A. G. and
H. H. thank the Swiss National Science Foundation and F. Hoffmann-La Roche AG, Basel, for financial
support, and G. M. and M. J. thank the National Science Center (Cracow, Poland) for generous support
(Grant Maestro-3, Dec-2012/06/A/ST5/00219).
Experimental Part
1. General. The reactions with thioketones were generally performed under Ar in flame-dried flasks.
Solvents and reagents were added by syringe. THF was dried with Na and benzophenone and freshly
distilled before use. Other reagents were purchased and used as received without further purification.
TLC: Merck 60 F254 SiO2-coated Al-plates, 0.2 mm; detection of the substances on the TLC plates under
UV light (l 254 nm) or with KMnO4 soln. Prep. TLC: Merck 60 F254 SiO2-coated glass-plates, 2 mm.
Column chromatography (CC): Merck 60 SiO2, 0.040 – 0.63 mm. M.p.: Mettler-FP-5 or MEL-TEMP II
(Aldrich) instrument; uncorrected. IR Spectra: Perkin-Elmer-1600-FT-IR or FT-IR NEXUS spectro-
photometer; film or KBr pellets; cmꢀ1. 1H- and 13C-NMR Spectra: Bruker-AC-300 and Bruker-ARX-300
(300 and 75.5 MHz, resp.), or Bruker AVIII 600 instrument (600 and 151 MHz, resp.), in CDCl3;
multiplicity of C-atoms from DEPTor 2D spectra (HMQC). MS: Finnigan MAT-90 or Finnigan SSQ-700
instrument (EI, 70 eV, or CI (NH3 or isobutene)) or Varian 500-MS LC Ion Trap instrument (ESI-MS).
Elemental analyses: Vario EL or a Vario EL III (Elementar Analysensysteme GmbH) instruments.

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2. Starting Materials. All chemicals were commercially available (Fluka, Aldrich, and Merck).
Lithium diisopropylamide (LDA) soln. (2.0m in THF) or (2.0m in THF/heptane/ethylbenzene) was
purchased from Fluka and Aldrich, resp., and used as received. Solvents were purified as follows: hexane,
distillation from CaH2; AcOEt and CH2Cl2, distillation from K2CO3 and stored over molecular sieves
(4 ꢃ); THF (purum, Fluka) and Et2O: dried over Na and dist.; toluene (p.a., Merck): stored over Na.
3. Reactions of 1,3-Thiazole-5(4H)-thiones 1 with LDA. General Procedure 1 (GP 1). To a cooled
soln. (ꢀ 788) of 4,4-dimethyl-2-phenyl-1,3-thiazole-5(4H)-thione (1a) or 2-phenyl-3-thia-1-azaspiro[4.4]-
non-1-en-4-thione (1b) (1 mmol), resp. in THF (20 ml) was added a 2m LDA soln. in THF (0.8 ml,
1.6 mmol). The soln. decolorized after a few min, and the mixture was warmed to r.t. Then, a cooled (08)
aq. soln. of NH4Cl was added, and the mixture was extracted with Et2O (3ꢁ). The combined org. phase
was dried (MgSO4), the solvent was evaporated, and the residue was purified by prep. TLC (hexane/
AcOEt).
General Procedure 2 (GP 2). To a cooled soln. (ꢀ 788) of 1a or 1b (1 mmol), resp., in THF (20 ml)
was added a 2m LDA soln. in THF (0.8 ml, 1.6 mmol). After stirring for 15 min, MeI (0.06 ml, 1 mmol)
was added, and stirring was continued at ꢀ 788 for another 15 min. The mixture was poured into ice-
water (100 ml) and extracted with Et2O (3ꢁ). The combined org. phase was dried (MgSO4), the solvent
was evaporated, and the residue was purified by prep. TLC (hexane/AcOEt).
4,5-Dihydro-4,4-dimethyl-2-phenyl-1,3-thiazole-5-thiol (4a) [12]. GP1; prep. TLC (hexane/AcOEt
10 :1). Yield: 154 mg (69%). Pale-yellow oil. IR (film): 2973s, 2929m, 2561m (br.), 1596s, 1576s, 1489m,
1447s, 1379m, 1360m, 1313m, 1259s, 1210m, 1174s, 949s, 847m, 823m, 765s, 690s, 614s. 1H-NMR
(300 MHz): 7.69 – 7.65 (m, 2 arom. H); 7.36 – 7.28 (m, 3 arom. H); 4.65 (d, J ¼ 9.1, HꢀC(5)); 2.02 (d, J ¼
9.1, SH); 1.42, 1.37 (2s, 2 Me). 13C-NMR (75 MHz): 163.5 (s, C¼N); 133.1 (s, 1 arom. C); 131.2, 128.4,
128.1 (3d, 5 arom. CH); 80.2 (s, C(4)); 58.1 (d, C(5)); 26.3, 22.6 (2q, 2 Me). CI-MS: 226 (10), 225 (14),
224 (100, [M þ 1]þ).
4,5-Dihydro-4,4-dimethyl-5-(methylsulfanyl)-2-phenyl-1,3-thiazole (9a) [13]. GP2; prep. TLC (hex-
ane/AcOEt 5 :1). Yield: 161 mg (68%). Pale-yellow oil. IR (film): 3061m, 3027m, 2974s, 2918s, 2861m,
1596s, 1577s, 1489s, 1447s, 1380m, 1360s, 1313m, 1296m, 1260s, 1209m, 1175s, 1120m, 1074m, 1028m,
1
1001m, 949s, 854m, 832s, 765s, 690s, 677s, 642m, 614s. H-NMR (300 MHz): 7.73 – 7.69 (m, 2 arom. H);
7.36 – 7.25 (m, 3 arom. H); 4.60 (s, HꢀC(5)); 2.06 (s, MeS); 1.50, 1.36 (2s, 2 Me). 13C-NMR (75 MHz):
163.1 (s, C¼N); 133.2 (s, 1 arom. C); 131.1, 128.4, 128.1 (3d, 5 arom. CH); 80.6 (s, C(4)); 67.5 (d, C(5));
27.1, 23.4 (2q, 2 Me); 15.5 (s, MeS). EI-MS: 237 (12, Mþ), 146 (9), 145 (100), 104 (31), 86 (53), 84 (94).
2-Phenyl-3-thia-1-azaspiro[4.4]non-1-ene-4-thiol (4b). GP1; prep. TLC (hexane/AcOEt 10 :1).
Yield: 156 mg (63%). Pale yellow oil. IR (film): 2976s, 2934m, 2560m (br.), 1594s, 1570m, 1489m, 1439s,
1360m, 1312m, 1210m, 1172s, 954m, 839m, 819m, 755s, 683m, 629w. 1H-NMR (300 MHz): 7.83 – 7.78 (m, 2
arom. H); 7.47 – 7.29 (m, 3 arom. H); 4.79 (d, J ¼ 8.4, HꢀC(5)); 2.19 – 2.10 (m, 2 H); 2.22 (d, J ¼ 8.4, SH);
2.08 – 1.60 (m, 6 H). 13C-NMR (75 MHz): 162.6 (s, C¼N); 133.1 (s, 1 arom. C); 131.1, 128.4, 128.2 (3d, 5
arom. CH); 92.1 (s, C(4)); 57.6 (d, C(5)); 39.7, 36.6, 34.8, 24.5 (4t, 4 CH2). EI-MS: 249 (6, Mþ), 216 (30),
171 (100), 156 (9), 143 (8), 121 (22), 104 (59), 77 (31).
4-(Methylsulfanyl)-2-phenyl-3-thia-1-azaspiro[4.4]non-1-ene (9b). GP2; prep. TLC (hexane/AcOEt
5 :1). Yield: 212 mg (80%). Colorless oil. IR (film): 3061m, 3026m, 2959s, 2870s, 1596s, 1577s, 1489s,
1
1447s, 1313s, 1256s, 1176m, 1157m, 1074m, 1050m, 1021m, 993s, 942s, 832s, 766s, 690s, 611s. H-NMR
(300 MHz): 7.74 – 7.71 (m, 2 arom. H); 7.34 – 7.24 (m, 3 arom. H); 4.61 (s, HꢀC(5)); 2.27 – 2.22 (m, 1 H);
2.20 – 2.06 (m, 1 H); 1.97 (s, MeS); 1.95 – 1.59 (m, 6 H). 13C-NMR (75 MHz): 162.7 (s, C¼N); 133.3 (s, 1
arom. C); 130.9, 128.4, 128.1 (3d, 5 arom. CH); 91.7 (s, C(4)); 66.0 (d, C(5)); 39.3, 34.1, 24.9, 23.9 (4t,
4 CH2); 14.0 (s, MeS). EI-MS: 263 (10, Mþ), 216 (10), 174 (12), 171 (100), 170 (20), 120 (9), 104 (39).
4. Reactions of Thioketones 10 with LDA. General Procedure 3 (GP 3). A soln. of thioketone
(2.0 mmol) in dry THF (3.0 – 5.0 ml) was added dropwise to a soln. of LDA (2.0m in THF/heptane/
ethylbenzene, 1.25 ml, 2.5 mmol) at ꢀ788 and stirred at this temp. for 10 min. Then, excess MeI (0.45 ml)
was added, and the resulting mixture was stirred another 10 min. After addition of H2O (15 ml), the
mixture was extracted with Et2O (3 ꢁ 10 ml), the combined org. layers were dried (MgSO4), filtered, and
the solvents were removed in vacuo. Crude products were purified by flash chromatography (FCC,
SiO2).

Helvetica Chimica Acta – Vol. 97 (2014)
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Adamant-2-yl Methyl Sulfide (¼2-(Methylsulfanyl)tricyclo[3.3.1.13,7]decane; 11a) [16]. GP 3; FCC
(petroleum ether (PE)/CH2Cl2 6 :1). Yield: 154 mg (42%). Colorless oil. IR (film): 3010 – 2850, 1450,
1100, 965. 1H-NMR (600 MHz): 2.97 (br. s, 1 H); 2.17 – 2.13 (m, 2 H); 2.08 (s, MeS); 1.73 – 2.01 (m,
10 H); 1.51 – 1.56 (m, 2 H). 13C-NMR (151 MHz): 55.0 (d, CH(2)); 38.7, 37.8 (2t); 32.5 (d); 31.9 (t); 27.8,
27.6 (2d); 14.9 (q, MeS). ESI-MS: 183 (100, [M þ 1]þ), 135 (63, [M ꢀ MeS]þ).
endo-Pentacyclo[5.4.0.02,6.03,10.05,9]undec-8-yl Methyl Sulfide (¼ Methyl (5S)-Octahydro-1H-2,4,1-
(ethane[1,1,2]triyl)cyclobuta[cd]pentalen-5-yl Sulfide; 11b). GP 3; FCC (PE/CH2Cl2 4 :1). Yield: 179 mg
(47%). Colorless oil. IR (film): 2970 – 2830, 1455, 1285. 1H-NMR (600 MHz): 2.73 – 2.70, 2.59 – 2.56,
2.55 – 2.53 (3m, 5 H, 2 :2 :1); 2.43 – 2.33, 2.26 – 2.20 (2m, 5 H, 2 :3); 2.10 (s, MeS); 1.70, 1.19 (2d, J ¼ 10.4,
1 H each); 1.05 – 1.01 (m, 1 H). 13C-NMR (151 MHz): 50.0, 47.0, 46.2, 46.0, 42.4, 42.0, 41.7, 39.3, 36.2 (9d);
34.4, 28.2 (2t); 17.5 (q, MeS). ESI-MS: 193 (100, [M þ 1]þ). Anal. calc. for C12H16S (192.32): C 74.94, H
8.39; found: C 74.95, H 8.29.
Diphenylmethyl Methyl Sulfide (11c) [20]. GP 3; FCC (PE/CH2Cl2 3 :1). Yield: 224 mg (52%).
1
Colorless solid. M.p. 29 – 318 ([20]: 30 – 318). IR (KBr): 3095 – 2825, 1490, 1450, 1420, 1080. H-NMR
(600 MHz): 7.46 – 7.42, 7.36 – 7.31, 7.27 – 7.22 (3m, 10 arom. H, 4 :4 :2); 5.08 (s, 1 H); 2.01 (s, MeS).
13C-NMR (151 MHz): 141.3 (s, 2 arom. C); 128.5, 128.3, 127.1 (3d, 10 arom. CH); 56.1 (d, CH)); 15.8 (q,
MeS). ESI-MS: 215 (4, [M þ 1]þ), 167 (100, [M ꢀ MeS]þ).
10,11-Dihydro-5H-dibenzo[a,d]cyclohepten-5-yl Methyl Sulfide (¼ Dibenzosuber-5-yl Methyl Sul-
fide) (11d). GP 3; FCC (PE/CH2Cl2 3 :1). Yield: 197 mg (41%). Colorless solid. M.p. 72 – 738. IR (KBr):
3060 – 2830, 1490, 1445, 1425. 1H-NMR (600 MHz): 7.25 – 7.12 (m, 8 arom. H); 4.93 (s, 1 H); 3.85 – 3.78,
2.96 – 2.89 (2m, 2 H each, CH2CH2); 1.99 (s, MeS). 13C-NMR (151 MHz): 140.7, 137.4 (2s, 2 arom. C);
130.9, 130.6, 127.7, 125.8 (4d, 8 arom. CH); 58.5 (d, CH)); 33.0 (t, CH2CH2); 16.8 (q, MeS). ESI-MS: 193
(100, [M ꢀ MeS]þ). Anal. calc. for C16H16S (240.37): C 79.95, H 6.71; found: C 80.03, H 6.66.
Methyl Phenyl(thiophen-2-yl)methyl Sulfide (¼2-[(Methylsulfanyl)(phenyl)methyl]thiophene; 11e).
GP 3; FCC (PE/CH2Cl2 4 :1). Yield: 39 mg (9%). Pale-orange oil. IR (film): 3100 – 2825, 1600, 1495,
1450, 1435, 1230. 1H-NMR (600 MHz): 7.46 (br. d, J ¼ 7.7, 2 H, Ph); 7.36 – 7.32 (m, 2 H, Ph); 7.29 – 7.25 (m,
1 H, Ph); 7.22 (br. dd, J ¼ 5.0, 0.9, 1 H); 6.96 – 6.91 (m, 2 H); 5.25 (s, CHꢀS); 2.05 (s, MeS). 13C-NMR
(151 MHz): 145.9, 141.1 (2s, 2 arom. C); 128.6, 128.1, 127.6 (3d, 5 CH, Ph); 126.6, 125.7, 125.1 (3d, 3 CH);
51.2 (d, CHꢀS); 16.0 (q, MeS). ESI-MS: 221 (27, [M þ 1]þ), 173 (100, [M ꢀ MeS]þ). Anal. calc. for
C12H12S2 (220.36): C 65.41, H 5.49; found: C 65.41, H 5.63.
Di(ferrocenyl)methyl Methyl Sulfide (11f). According to GP 3, di(ferrocenyl)thioketone (77 mg,
0.186 mmol) was reacted with LDA (0.30 ml, 0.60 mmol) and MeI (171 mg, 0.75 ml, 1.2 mmol). FCC (PE/
CH2Cl2 3 :1) afforded 11f (30 mg, 37%). Orange solid. M.p. 107 – 1088. IR (KBr): 3120 – 2855, 1635, 1410,
1
1105, 1000. H-NMR (600 MHz): 4.46 (s, 1 H); 4.26, 4.16, 4.13 (3 br. s, 18 H, 2 :4 :12); 1.88 (s, MeS).
13C-NMR (151 MHz): 91.4 (s, 2 arom. C); 69.0 (d, 10 arom. CH); 68.0, 67.8, 67.09, 67.07 (4 d, 8 arom. CH);
45.3 (d, CH); 15.8 (q, MeS). ESI-MS: 430 (26, Mþ), 383 (100, [M ꢀ MeS]þ). HR-EI-MS: 430.0150 (Mþ,
C22H22Fe2Sþ; calc. 430.0141).
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Received April 10, 2014