Synthesis and reaction of α-dithiolactone

Article abstract of DOI:10.1002/chem.200600412

Treatment of di-tert-butylthioketene S-oxide (5a) with Lawesson reagent at room temperature resulted in the formation of 3,3-di-fert-butylthiirane-2-thione (4a) in high yield. The oxidation of 4 a with mCPBA (mCPBA = m-chloroperbenzioc acid) gave 3,3-di-ferf-butylthiirane-2-thione S-oxide (6) almost quantitatively. The reactions of 4 a with dimethyl acetyle nedicarboxylate (DMAD) and benzyne afforded dimethyl 2-(2,2,4,4-tetramethylpentan-3-ylidene)-1, 3-dithiole-4,5-dicarboxylate (13) and 2-(2,2,4,4-tetramethylpentan-3-ylidene) benzo[d] [1,3]-dithiole (15), respectively, in high yields, suggesting that 4 a is an excellent 1,3-dipole. The reaction of 4 a with ethylenebis(triphenylphosphine)platinum (16) gave dithiolato-platinum complex (22) in high yield. The structure of 22 was determined by X-ray crystallographic analysis.

Full text of DOI:10.1002/chem.200600412

DOI: 10.1002/chem.200600412
Synthesis and Reaction of a-Dithiolactone
Toshiyuki Shigetomi,[a] Hiroe Soejima,[a] Yoshinori Nibu,[a] Kosei Shioji,[a]
Kentaro Okuma,*[a] and Yoshinobu Yokomori[b]
Abstract: Treatment of di-tert-butylthi-
oketene S-oxide (5a) with Lawesson
reagent at room temperature resulted
in the formation of 3,3-di-tert-butylthi-
irane-2-thione (4a) in high yield. The
oxidation of 4a with mCPBA
(mCPBA=m-chloroperbenzioc acid)
gave 3,3-di-tert-butylthiirane-2-thione
S-oxide (6) almost quantitatively. The
reactions of 4a with dimethyl acetyle-
nedicarboxylate (DMAD) and benzyne
afforded dimethyl 2-(2,2,4,4-tetrame-
thylpentan-3-ylidene)-1,3-dithiole-4,5-
dicarboxylate (13) and 2-(2,2,4,4-tetra-
N
G
methylpentan-3-ylidene)benzo[d][1,3]-
G
Keywords: alpha-thiolactone · ben-
zo-1,3-dithiole · benzyne · platinum ·
synthetic methods
Introduction
Three-membered cyclic compounds containing two hetero-
atoms have been studied extensively.[1–5] The isolation of a
ACHTREUNG
series of stable dithiiranes was reported by Ishii and Na-
kayama.[1a–c] Methods for the synthesis of a-lactams include
the reaction of N-tert-butyl-2-bromo-2-phenylacetamide
with potassium tert-butoxide,[2a] the reaction of 2-bromo-3,3-
dimethyl-N-tert-butylbutyramide with potassium tert-butoxi-
de,[2b] and the reaction of a-chloro-a-phenylacetanilide with
sodium hydride.[2c] Although a-lactones 1[3] have been pro-
posed as intermediates, there is only one example reported
to date of an a-lactone isolable by electronic stabilization,
namely, 3,3-bis(trifluoromethyl)oxirane-2-one,[3a] which is
relatively stable at 258C with a half-life of 8 h. The sterically
congested a-lactone, 3,3-di-tert-butyloxirane-2-one (1a), is
stable at À608C but polymerizes at À208C.[3b] Schaumann
and Behrens reported the synthesis and characterization of
3,3-di-tert-butylthiirane-2-one (2a), a thio analogue of a-lac-
tone, which was synthesized by reacting di-tert-butylthioke-
tene (3a) with nitrones.[4] Compound 2a is stable at room
temperature but decomposes at 658C. Although a-dithiolac-
tone (4) has been proposed as an intermediate for the syn-
thesis of 1,2,4,5-tetrathianes, 1,2,4-trithiolanes, and disul-
fides,[5] there has been no report of the isolation of 4. As 2a
is more stable than 1a, we hypothesized that 3,3-di-tert-bu-
tylthiirane-2-thione (4a) would be the most isolable a-di-
thiolactone. We recently communicated the synthesis of 4a[6]
and herein report the full details of the synthesis and reac-
tion of 4.
Results and Discussion
Synthesis of a-dithiolactone: As Schaumann and Behrens
reported the synthesis of a-thiolactone (2) by the oxidation
of thioketene, the thiation of 3a is expected to be one of the
simplest ways to obtaining a-dithiolactone. Di-tert-butylthio-
ketene (3a) was synthesized from di-tert-butylketene accord-
ing to a reported method.[7] When the reaction of 3a with
Lawesson reagent (LR) was carried out at room tempera-
ture for 20 h, the target compound was not isolated. Thus,
[a] T. Shigetomi, H. Soejima, Y. Nibu, K. Shioji, Prof. Dr. K. Okuma
Department of Chemistry, Faculty of Science
Fukuoka University, Jonan-ku, Fukuoka 814–0180 (Japan)
Fax : (+81)92-865-6030
E-mail: kokuma@fukuoka-u.ac.jp
[b] Prof. Dr. Y. Yokomori
National Defense Academy, Hashirimizu
Yokosuka 239–8686 (Japan)
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another synthetic method was required. Based on the report
by Shimada and Takikawa of the LR-mediated synthesis of
dithiirane from thioketone S-oxides under mild condi-
tions,[1d] we attempted the synthesis of 4a by reacting di-tert-
butylthioketene S-oxide (5a) with LR. Compound 3a was
oxidized with mCPBA to give 5a in 92% yield.[7,8] Treat-
ment of 5a with LR at room temperature for 12 h resulted
in the formation of 4a in 88% yield (Scheme 1).
(1,1,3,3-tetramethyl-1H-inden-2(3H)-ylidene)methanethione
(3c), suggesting that the steric effect of 4c is smaller than
that of 4a and b (Scheme 4).
Scheme 4.
Scheme 1.
As a-dithiolactone is an isomer of dithiirane (7) and thio-
ketene S-sulfide (8), the stabilities of a-dithiolactone 4, di-
thiirane 7, and thioketene S-sulfide 8 were compared
(Scheme 5).[9]
The structure of 4a was confirmed by NMR spectroscopy,
IR spectrometry, elemental analysis, and MS analysis. The
oxidation of 4a with mCPBA (1 equiv) gave 3,3-di-tert-bu-
tylthiirane-2-thione S-oxide (6) almost quantitatively
(Scheme 2). Structural proof of 6 was provided by NMR
Scheme 2.
spectroscopy, IR spectrometry, elemental analysis, and X-
ray crystallographic analysis.[6] Similarly, treatment of
(2,2,6,6-tetramethylcyclohexylidene)methanethione S-oxide
(5b) with LR at room temperature resulted in the formation
Scheme 5.
of
3,3-(2’,2,’6’,6’-tetramethylcyclohexyl)thiirane-2-thione
By means of geometry optimization and frequency calcu-
(4b) in 64% yield (Scheme 3). However, the reaction of
lation at the B3LYP/6-31G(d,p) level, 4a was calculated to
A
be 56.5 and 79.9 kJmolÀ1 more stable than 3-(2,2,4,4-tetra-
methylpentan-3-ylidene)dithiirane (7a) and di-tert-butylthio-
ketene S-sulfide (8a), respectively, at the ground state S0
(Figure 1). The difference in zero vibration energy between
4a and 7a is similar to that between 4b and 3-(2,2,6,6-tetra-
methylcyclohexylidene)dithiirane (7b), whereas the differ-
ence in zero vibration energy between 4c and 7c is smaller
than the above, suggesting that 4c easily isomerizes to 7c,
which might explain the difficulty of isolating 4c.
To confirm the stability of 4, thermolysis of 4 was carried
out. When a-dithiolactones 4a and 4b were refluxed in
[D8]toluene, thioketenes 3a and 3b were obtained. The rate
of thermolysis of 4a could be conveniently and accurately
monitored by 1H NMR spectroscopy. First-order reaction
was observed by this technique. A rate constant of 1.14”
Scheme 3.
(1,1,3,3-tetramethyl-1H-inden-2(3H)-ylidene)methanethione
S-oxide (5c) with LR at room temperature gave not 3,3-
(1’,1’,3’,3’-tetramethyl-2’-indan)thiirane-2-thione (4c), but
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K. Okuma et al.
Scheme 7.
Figure 1. Calculated zero vibration energies of 4, 7, and 8.
and carbene intermediate (12),[11] thus formed by nitrogen
extrusion, rearranged to give 11.
10À2 hÀ1 at 393 K in [D10]xylene was observed. Addition of
sulfur did not affect the rate constant of this reaction, sug-
gesting that direct sulfur extrusion of 4a or 7a might be op-
erative. By comparison with the calculated zero vibration
energy of 4a and 7a, 4a was speculated to isomerize to 7a,
which extruded sulfur to give 3a (Scheme 6).
Reaction of a-dithiolactone: The oxidation of 4a with
excess mCPBA gave 5a almost quantitatively (Scheme 8).
Scheme 6.
Scheme 8.
As the synthesis of thioketene S-oxide 5a requires eight
steps, starting from commercially available pivalonitrile,[7]
a
much shorter synthetic method of 4 is preferable. Schçnberg
reported the synthesis of 3,3,6,6-tetraphenyl-1,2,4,5-tetra-
thiane by reacting diphenyldiazomethane with carbon disul-
fide,[5d] the intermediate of which was surmised to be a-di-
thiolactone. Therefore, we attempted the synthesis of 4a by
reacting di-tert-butyl diazomethane (9a) with carbon disul-
fide (Scheme 7). When 9a was heated in refluxing carbon
disulfide for two days, 4a was obtained in 17% yield along
with 3a in 34% yield and di-tert-butyl thioketone in 27%
yield. We speculated that the extrusion of nitrogen from in-
termediate 10 would give 4a. This is another method for the
synthesis of 4a. Refluxing a solution of diazo-1,1,3,3-tetra-
methylindane (9b) in carbon disulfide for one day afforded
not 4c but 1,1,2,3-tetramethyl-1H-indene (11)[10] in 58%
yield, suggesting that 9b did not react with carbon disulfide,
Reaction of 6 with mCPBA gave the same results. Presuma-
bly, initially formed S-oxide 6 was further oxidized to give
episulfide S-oxide or S,S-dioxide, which extruded SO or SO2
to give 5a. Schaumann and Behrens reported that the oxida-
tion of a-thiolactone afforded the corresponding ketene, the
intermediate of which might be episulfide S-oxide.[4] The
present result is similar to that of Schaumann and Behrens.
The desulfurization of 4a with triphenylphosphine in reflux-
ing chloroform gave 3a in almost quantitative yield along
with triphenylphosphine sulfide. The reaction of 4a with
methyllithium in benzene at room temperature afforded 3a
almost quantitatively. The ring strain of episulfide eliminat-
ed the sulfur of 4a.
To confirm 1,3-dipolarophilic reactivity, the reaction of 4a
with different acetylenes was carried out (Scheme 9). The
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Synthesis and Reaction of a-Dithiolactone
FULL PAPER
oxide with 16 afforded (sulfenato-thilato)-platinum complex
21.[15] Although Ishii and Nakayama isolated dithiolato com-
plex 20 by reacting tetrathiolane with 16, no X-ray crystallo-
graphic analysis of complex 20 was reported due to its low
yield.[16] Thus, we attempted the formation of the dithiolato
complex by reacting 4a with 16, and conducted X-ray crys-
tallographic analysis of the resultant compound.
Treatment of 4a with 16 gave (bistriphenylphosphine)-2-
(2,2,4,4-tetramethylpentan-3-ylidene)-1,3-dithiolato-plati-
num (22) in 90% yield (Scheme 11). The reaction was com-
Scheme 9.
reaction of 4a with DMAD in [D]chloroform afforded di-
methyl 2-(2,2,4,4-tetramethylpentan-3-ylidene)-1,3-dithiole-
4,5-dicarboxylate (13) in almost quantitative yield, whereas
the reaction of 4a with methyl propiolate in [D]chloroform
led to the recovery of starting 4a . Huisgen et al. reported
that DMAD is 337 times more reactive as a 1,3-dipolaro-
phile than methyl propiolate.[12] The difference in reactivity
between DMAD and methyl propiolate in the present study
is similar to that reported by Huisgen et al.
Treatment of 4a with benzyne from o-trimethylsilylphenyl
trifluoromethanesulfonate (14) and tetrabutylammonium
fluoride (Scheme 10) resulted in the formation of 2-(2,2,4,4-
Scheme 11.
pleted within 3 min. As the recrystallization of 22 from
hexane-dichloromethane (3:1) gave single crystals, its X-ray
crystallographic analysis was carried out. Figure 2 shows an
ORTEP drawing of 22.
Scheme 10.
tetramethylpentan-3-ylidene)benzo[d][1,3]dithiole (15) in
G
90% yield. When a 1:1 mixture of 4a and furan was reacted
with benzyne, only 15 was obtained in 85% yield , suggest-
ing that 4a is more reactive than furan. Thus, a-dithiolac-
tone is an excellent 1,3-dipole.
Synthesis of platinum complex: Weigand and Mloston stud-
ied the reactions of disulfides and thiosulfinates with plati-
num(0) complexes[13] and reported that the reaction of
1,2,4,5-tetrathiane and 1,2,4-trithiolane with ethylene (bistri-
phenylphosphine)platinum (16) gave dithiolato complex 17
and thiocarbonyl-platinum complex 18, respectively.[14] They
stated that the X-ray crystallographic analysis of 17 was un-
successful due to the formation of 17 and 18 as a 1:1 mix-
ture. Ishii and Nakayama reported that the reaction of di-
thiirane with 16 gave thiocarbonyl-platinum complex 19 and
not dithiolato complex 20 and the reaction of dithiirane
À
Figure 2. ORTEP drawing of complex 22. Bond lengths: C37 S1:
À
À
À
1.790(3), C37 S2: 1.780(3), Pt S1: 2.290(7), and Pt S2: 2.283(8) Š. Bond
angles: S2-C37-S1: 103.4(14), S2-Pt-S1: 75.6(3), C37-S1-Pt: 90.2(9), and
C37-S2-Pt: 90.7(10)8.
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K. Okuma et al.
À
2(3H)-ylidene)methanethione (3c) (0.054 g, 0.25 mmol) in dichlorome-
thane (3 mL). After the reaction mixture had been stirred for 0.5 h, the
reaction mixture was evaporated to give white-yellow crystals, which
were chromatographed over silica gel by elution with hexane to give
pure 5c (0.049 g, 0.21 mmol). Colorless oil; 1H NMR (400 MHz, CDCl3,
278C, TMS): d=1.17 (s, 6H), 1.28 (s, 6H), 7.28–7.34 (m, 2H), 7.47 (t,
1H, J=7.6 Hz), 7.91 (d, 1H, J=8.0 Hz) 8.63 ppm (d, 1H, J=7.6 Hz).
13C NMR (100 MHz, CDCl3, 278C, TMS): d=25.2, 26.1, 50.2, 53.6, 123.0,
127.8, 128.6, 132.8, 136.3, 153.7, 199.7 ppm; elemental analysis calcd for
C14H16OS·1/2H2O: C 69.67, H 7.10; found: C 69.80, H 7.25.
The bond lengths of the four-membered ring of 22 are C
À
S: 1.790, 1.780 Š and S Pt: 2.290, 2.283 Š. The bond lengths
of the four-membered ring of (sulfenato-thiolato)platinum
À
À
complex 21 are C S: 1.871 or 1.827 Š and S Pt: 2.353 or
2.314 Š.[15] The bond lengths of the four-membered ring of
22 are shorter than those of the four-membered ring of 21.
Thus, complex 22 might be more stable than 21. In the
31P NMR spectrum, the phosphorus signal of 22 resonated at
d=22.7 ppm (J
ported that the phosphorus signal of 17 resonated at d=
22.1 ppm (J
(Pt,P)=2970 Hz).[14] Ishii and Nakayama report-
ed that the phosphorus signal of the 20 resonated at d=
22.9 ppm (J
(Pt,P)=2925 Hz).[16] The phosphorus signal of 22
is similar to those of 17 and 20.
(Pt,P)=2961 Hz). Weigand and Mloston re-
Synthesis of 3,3-di-tert-butylthiirane-2-thione (4a): A solution of Lawes-
son reagent (0.606 g, 1.5 mmol) was added in one portion to a solution of
di-tert-butylthioketene S-oxide (5a) (0.186 g, 1.0 mmol) in dichlorome-
thane (15 mL). After the reaction mixture had been stirred for 12 h, it
was evaporated to give yellow oily crystals, which were chromatographed
over silica gel by elution with hexane to give pure 4a (0.137 g,
0.64 mmol). Sublimation of this compound gave the analytically pure
sample. Yellow crystals; m.p. 98–1018C; 1H NMR (400 MHz, CDCl3,
278C, TMS): d=1.28 ppm (s, 18H; tBu); 13C NMR (100 MHz, CDCl3,
278C, TMS): d=30.4, 39.5, 76.3, 226.7 ppm (C=S); IR (KBr): n˜ =
1367 cmÀ1 (C=S); EIMS m/z (%): found: 202 [M]+ (4.1), 170 [MÀS]+
(2.5), 146 (11.7), 145 [MÀtBu]+ (16.5), 126 (15.7), 113 (15.1), 111 (26.8),
99 (8.1), 69 (15.2), 57 [tBu] (100); elemental analysis calcd for C10H18S2:
C 59.35, H 8.96; found: C 59.05, H 8.65; UV/Vis: lmax (e)=317.5 nm
(4780), 269.0 (3974 molÀ1 dm3 cmÀ1).
ACHTREUNG
ACHTREUNG
Conclusions
Treatment of 5a–b with LR at room temperature resulted in
the formation of 4a–b in high yields. This is the first exam-
ple of the isolation of a-dithiolactones. The oxidation of 4a
with mCPBA (1 equiv) gave 6 almost quantitatively. Struc-
tural proof of 6 was provided by X-ray crystallographic anal-
ysis. Thermolysis of 4a gave thioketene 3a quantitatively.
The reactions of 4a with DMAD and benzyne afforded 13
and 15, respectively, in high yields, suggesting that a-dithio-
lactone is an excellent 1,3-dipolarophile. The reaction of 4a
with 16 gave 22 in high yield. The structure of 22 was deter-
mined by X-ray crystallographic analysis.
Synthesis of 3,3-(2,2,6,6-tetramethylcyclohexyl)thiirane-2-thione (4b): A
solution of Lawesson reagent (0.606 g, 1.5 mmol) was added in one por-
tion to a solution of (2,2,6,6-tetramethylcyclohexylidene)methanethione
S-oxide (5b) (0.198 g, 1.0 mmol) in dichloromethane (15 mL). After the
reaction mixture had been stirred for 12 h, it was evaporated to give
yellow oily crystals, which were chromatographed over silica gel by elu-
tion with hexane to give pure 4b (0.137 g, 0.64 mmol). Sublimation of
this compound gave the analytically pure sample. Yellow crystals; m.p.
59–618C; 1H NMR (400 MHz, CDCl3, 278C, TMS): d=0.97 (s, 6H), 1.24
(s, 6H), 1.75 (s, 4H), 1.75 ppm (m, 2H); 13C NMR (100 MHz, CDCl3,
278C, TMS): d=18.8, 27.8, 28.6, 38.5, 40.7, 75.4, 226.7 ppm. IR (KBr):
n˜ =1379 cmÀ1 (C=S); elemental analysis calcd for C11H18S2: C 61.62; H
8.46; found: C 61.16; H 8.07.
Experimental Section
Thiation of (1,1,3,3-tetramethyl-1H-inden-2(3H)-ylidene)methanethione
S-oxide (5c): Lawesson reagent (31 mg, 0.06 mmol) was added to a solu-
tion of (1,1,3,3-tetramethyl-1H-inden-2(3H)-ylidene)methanethione S-
oxide (5c) (0.010 mg, 0.04 mmol) in [D]chloroform. After the reaction
mixture had been stirred for 3 h, it was monitored by NMR spectroscopy.
The presence of (1,1,3,3-tetramethyl-1H-inden-2(3H)-ylidene)methane-
thione (3c) was observed by 1H NMR spectroscopic analysis. The reac-
tion mixture was then evaporated to give a purple oil, which was chroma-
tographed over silica gel by elution with hexane to give pure 3c (0.008 g,
0.04 mmol).
General: All chemicals were obtained from commercial suppliers and
were used without further purification. Analytical TLC was carried out
on precoated plates (Merck silica gel 60, F254) and flash-column chroma-
tography was performed with silica (Merck, 70—230 mesh). NMR spectra
(1H at 400 MHz; 13C at 100 MHz) were recorded in CDCl3 solvent, and
chemical shifts are expressed in ppm relative to internal TMS. Melting
points were uncorrected.
CCDC-605410 contains the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Synthesis of 3,3-di-tert-butylthiirane-2-thione S-oxide (6): A solution of
m-chloroperbenzoic acid (0.204 g, 1.2 mmol) in dichloromethane (3 mL)
was added in one portion to a solution of 3,3-di-tert-butylthiirane-2-
thione (4a) (0.161 g, 0.8 mmol) in dichloromethane (10 mL). After the
reaction mixture had been stirred for 0.5 h, hexane (10 mL) was added to
the reaction mixture, which was subsequently filtered and evaporated to
give a deep-yellow oil. This oil was chromatographed over silica gel by
Synthesis of (1,1,3,3-tetramethyl-1H-inden-2(3H)-ylidene)methanethione
(3c): 1,1,3,3-Tetramethyl-indan-2-carboxylic acid (0.218 g, 1.0 mmol) was
refluxed in thionyl chloride (10 mL). After the reaction mixture had
been stirred for 2 h, it was evaporated to give a yellow oil (1,1,3,3-tetra-
methyl-indan-2-carbonyl chloride). The mixture of 1,1,3,3-tetramethyl-
indan-2-carbonyl chloride and P4S10 (0.189 g, 0.85 mmol) was refluxed in
pyridine (5 mL) for 9 h. The reaction mixture was evaporated to give a
reddish-yellow oil, which was chromatographed over silica gel by elution
with hexane to give pure 3c (0.024 g, 0.11 mmol). Purple oil; 1H N MR
(400 MHz, CDCl3, 278C, TMS): d=1.22 (s, 6H; CH3), 1.24 (s, 6H; CH3),
7.31 (t, 1H, J=8.0 Hz), 7.42 (d, 1H, J=8.0 Hz), 7.61 (t, 1H, J=8.0 Hz),
7.91 ppm (d, 1H, J=8.0 Hz); 13C NMR (100 MHz, CDCl3, 278C, TMS):
d=25.9 (CH3), 26.1 (CH3), 47.5, 48.8, 65.0, 123.3, 124.4, 127.6, 134.5,
143.2, 160.5, 254.9 ppm; elemental analysis calcd for C14H16S: C 77.72, H
7.45; found: C 77.39, H 7.72.
elution with hexane/dichloromethane 1:1 to give pure
6 (0.164 g,
0.75 mmol). Yellow crystals; m.p. 97–998C; 1H NMR (400 MHz, CDCl3,
278C,TMS): d=1.25 ppm (s, 18H); 13C NMR (100 MHz, CDCl3, 278C,
TMS): d=31.5, 40.9, 83.4, 181.0 ppm; IR (KBr): 1095 cmÀ1 (C=S=0); ele-
mental analysis calcd for C10H18S2O: C 55.00, H 8.31; found: C 55.18, H
8.36; UV/Vis: lmax (e)=321.5 nm (4580 molÀ1 dm3 cmÀ1).
Reaction of di-tert-butyldiazomethane (9a) with carbon disulfide: A sol-
ution of di-tert-butyldiazomethane (9a) (0.77 g, 5.0 mmol) in carbon di-
sulfide (30 mL) was stirred and refluxed for two days. After this time, the
reaction mixture was evaporated to give a yellow oil, which was chroma-
tographed over silica gel by elution with hexane to give 4a (0.172 g,
0.85 mmol), 3a (0.289 g, 1.70 mmol), and di-tert-butyl thioketone (0.213 g,
Synthesis of (1,1,3,3-tetramethyl-1H-inden-2(3H)-ylidene)methanethione
S-oxide (5c): A solution of mCPBA (0.052 g, 0.30 mmol) in dichlorome-
thane (2 mL) was added to a solution of (1,1,3,3-tetramethyl-1H-inden-
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Synthesis and Reaction of a-Dithiolactone
FULL PAPER
1.35 mmol). Purple oil; b.p. 70–758C (25 mmHg) (lit.[17] b.p. 61 8C
(14 mmHg)).
water and extracted with hexane. The combined solution was dried over
magnesium sulfate, filtered, and evaporated to give orange crystals. The
orange crystals were recrystallized from hexane to give yellow crystals 15
(0.059 g, 0.21 mmol).
Reaction of diazo-1,1,3,3-tetramethylindane (9b) with carbon disulfide:
A
mixture of 1,1,3,3-tetramethyl-2-indanone hydrazone (220 mg,
Synthesis of platinum complex (22): Ethylene (bistriphenylphosphine)-
1.1 mmol), barium manganate (700 mg, 13.5 mmol), and calcium oxide
(700 mg, 12.5 mmol) was refluxed in dichloromethane (5 mL). After the
reaction mixture had been stirred for 1 h, it was filtered through celite.
The reaction mixture was then evaporated to give diazo-1,1,3,3-tetra-
methyl indane (9b). A solution of 9b in carbon disulfide (15 mL) was
stirred and heated at 458C for a day. After this time, the reaction mixture
was evaporated to give a red-yellow oil, which was chromatographed
over silica gel by elution with hexane to give colorless oil 11 (0.110 g,
0.64 mmol).
platinum (16) (0.075 g, 0.10 mmol) was added to
a solution of 4a
(0.020 g, 0.10 mmol) in dichloromethane (2 mL). After the reaction mix-
ture had been stirred for 0.5 h, it was evaporated to give a black-yellow
solid. The residue was recrystallized from hexane/dichloromethane 3:1 to
give yellow crystals 22 (0.083 g, 0.09 mmol). Yellow crystals; m.p. 253.0–
255.18C (dec.); 1H NMR (400 MHz, CDCl3, 278C, TMS): d=1.38 (s,
18H; tBu), 7.12–7.46 ppm (m, 45H; PPh3); 13C NMR (100 MHz, CDCl3,
278C, TMS): d=34.0 (tBu), 40.9, 127.8, 130.3, 130.9, 134.9, 137.2.
142.1 ppm; 31P NMR (162 MHz, CDCl3, 278C, H3PO4) d=22.7 ppm (J-
Thermolysis of 4a: Compound 4a (0.020 g, 0.10 mmol) was heated for
four days in [D8]toluene at 1008C. Decomposition of 4a and the forma-
tion of 3a was observed by NMR spectroscopy. The reaction mixture was
evaporated to give a purple oil, which was chromatographed over silica
gel by elution with hexane to give 3a (0.014 g, 0.088 mmol).
(Pt,P)=2961 Hz); elemental analysis calcd for C46H48P2S2Pt: C 59.92, H
5.25; found: C 59.82, H 5.33.
Crystallographic data for 22: C46H48P2PtS2, monoclinic, P21/n(14), a=
13.572(2), b=19.845(2), and c=16.1360(17) Š, a=908, b=107.374(6)8,
g=908, V=4147.7(8) Š3, Z=4, Density (calcd)=1.476 MgmÀ3, Crystal
size 0.40”0.40”0.05 mm3. The final cycle of full-matrix least-squares re-
finement was based on 3994 observed reflections and variable parameters
456 with R1=0.0890 and Rw=0.2301. S (goodness-of-fit)=1.095. Reflec-
tion data were obtained at 293 K on a DIP-3200 X-ray diffractometer
(Bruker AXS Co. LTD) with an imaging plate, CuKa radiation, and Ni
filter.
Reaction of 4a with triphenylphosphine: Triphenylphosphine (0.026 g,
0.10 mmol) was added to
a solution of 4a (0.020 g, 0.10 mmol) in
[D]chloroform. The resulting reaction mixture was then heated for four
days at 608C. The formation of 3a was monitored by NMR spectroscopy.
The reaction mixture was evaporated to give a purple oil, which was
chromatographed over silica gel by elution with hexane to give 3a
(0.015 g, 0.092 mmol) and triphenylphosphine sulfide (0.027 g,
0.092 mmol).
Reaction of 4a with methyllithium: Methyllithium in diethyl ether (1.0m,
0.25 mL, 0.25 mmol) was added to a solution of 4a (0.050 g, 0.25 mmol)
in benzene and the resulting mixture was stirred for 1 h. After the reac-
tion mixture had been washed with water, it was evaporated to give a
purple oil 3a (0.040 g, 0.24 mmol).
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Reaction of 4a with dimethyl acetylenedicarboxylate: Dimethyl acetyle-
nedicarboxylate (0.036 g, 0.25 mmol) was added to a solution of 4a
(0.025 g, 0.12 mmol) in chloroform. After the reaction mixture had been
refluxed for 2 h, it was evaporated to give yellow crystals. The mixture
was purified on silica gel with hexane/dichloromethane 1:1 to give di-
methyl 2-(2,2,4,4-tetramethylpentan-3-ylidene)-1,3-dithiole-4,5-dicarboxy-
late (13) (0.038 g, 0.11 mmol). Yellow crystals; m.p. 87.1–89.18C;
1H NMR (400 MHz, CDCl3, 278C, TMS): d=1.43 (s, 18H; CH3),
3.82 ppm (s, 6H; OCH3); 13C NMR (100 MHz, CDCl3, 278C, TMS): d=
32.5 (tBu), 41.5, 53.5 (OCH3), 123.4, 130.4, 142.6, 160.8 ppm; elemental
analysis calcd for C16H24O4S2: C 55.78, H 7.02; found: C 55.68, H 7.24.
Reaction of 4a with methyl propiolate: To a solution of 4a (0.020 g,
0.10 mmol) in [D]chloroform was added methyl propiolate (0.018 g,
0.20 mmol). The solution was heated for two days at 608C and the reac-
tion was monitored by NMR spectroscopy. After 24 h, 4a was recovered
unchanged.
Synthesis of 2-(2,2,4,4-tetramethylpentan-3-ylidene)benzo[d][1,3]dithiole
A
(15): Tetrabutylammonium fluoride in THF complex (1.0m, 1.0 mL,
1.0 mmol) was added to a solution of 4a (0.101 g, 0.5 mmol) and o-trime-
thylsilylphenyl trifluoromethanesulfonate (0.149 g, 0.5 mmol) in dichloro-
methane (10 mL). After the reaction mixture had been stirred for 0.5 h,
it was evaporated to give a red-yellow oil. The reddish-yellow oil washed
with water and extracted with hexane. The combined extract was dried
over magnesium sulfate, filtered, and then evaporated to give orange
crystals, which were recrystallized from hexane to give yellow crystals 15
(0.125 g, 0.45 mmol). Yellow crystals; m.p. 46.2–52.08C; 1H N MR
(400 MHz, CDCl3, 278C, TMS): d=1.51 (s, 18H, tBu), 6.99–7.02 (m,
2H), 7.19–7.21 ppm (m, 2H); 13C NMR (100 MHz, CDCl3, 278C, TMS):
d=32.9 (tBu), 41.5, 119.9, 124.9, 125.4, 136.9, 142.3 ppm; elemental anal-
ysis calcd for C16H22S2: C 69.01, H 7.96; found: C 68.98, H 7.99.
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[9] Ab initio MO calculations were carried out by using Gaussian 98
program at the B3LYP/6-31G .
(d,p) level. One au=2624.6 kJmolÀ1
G
Calculated vibration frequencies of 1a, 4, and 5 were not imaginary.
Gaussian 98 (Revision A.9) M. J. Frisch, G. W. Trucks, H. B. Schle-
gel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, V. G. Zakrzewski,
J. A. Jr. Montgomery, R. E. Stratmann, J. C. Burant, S. Dapprich,
J. M. A. Millam, D. Daniels, K. N. Kudin, M. C. Strain, O. Farkas, J.
Tomasi, V. Barone, M. Cossi, R. Cammi, B. Mennucci, C. Pomelli,
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Cui, K. Morokuma, D. K. Malick, A. D. Rabuck, K. Raghavachari,
Reaction of 4a and furan with benzyne: Tetrabutylammonium fluoride in
THF complex (1.0m, 0.606 g, 1.5 mmol) was added to a solution of 4a
(0.051 g, 0.25 mmol), furan (0.017 g, 0.025 mmol), and o-trimethylsilyl-
phenyl trifluoromethanesulfonate (0.075 g, 0.025 mmol) in dichlorome-
thane (5 mL). After the reaction mixture had been stirred for 0.5 h, it
was evaporated to give a reddish-yellow oil, which was washed with
Chem. Eur. J. 2006, 12, 7742 – 7748
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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Received: March 24, 2006
Published online: July 3, 2006
7748
www.chemeurj.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 7742 – 7748