Reactions of thioketones with dichlorocarbene

Article abstract of DOI:10.1002/(SICI)1522-2675(19990609)82:6<946::AID-HLCA946>3.0.CO;2-P

The reactions of sterically crowded cycloalkanethiones of type 2 with CHCl₃/NaOH under phase-transfer catalysis (PTC) with benzyl(triethyl)ammonium chloride (TEBA) as catalyst afforded the corresponding 'gem.-dichlorothiiranes' of type 3 in good yields (cf. Scheme 2 and Table). The desulfurization, which, in some cases, occurred spontaneously, led to (dichloromethylidene)cycloalkanes of type 4. Similar results were obtained using Seyferth's reagent in boiling benzene. In the case of 2,2,6,6-tetramethylcyclohexanethione, reaction under PTC conditions after 3 h yielded only the corresponding dichloromethylidene derivative; on the other hand, workup after 1 h gave (2,2,6,6- tetramethylcyclohexylidene)methanethione (thioketene 9; Scheme 5).

Full text of DOI:10.1002/(SICI)1522-2675(19990609)82:6<946::AID-HLCA946>3.0.CO;2-P

946
Helvetica Chimica Acta ± Vol. 82 (1999)
1
Reactions of Thioketones with Dichlorocarbene )
2
3
by Grzegorz Mlosto n *, Jaroslaw Roma n ski ), and Anna Swi aË tek )
Department of Organic and Applied Chemistry, University of è o d z Narutowicza 68, PL-90-136 è o d zÂ
and Heinz Heimgartner*
Organisch-chemisches Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich
Dedicated to Prof. Andrzej Jo n czyk on the occasion of his 60th birthday
3
The reactions of sterically crowded cycloalkanethiones of type 2 with CHCl /NaOH under phase-transfer
catalysis (PTC) with benzyl(triethyl)ammonium chloride (TEBA) as catalyst afforded the corresponding ꢀgem.-
dichlorothiiranesꢁ of type 3 in good yields (cf. Scheme 2 and Table). The desulfurization, which, in some cases,
occurred spontaneously, led to (dichloromethylidene)cycloalkanes of type 4. Similar results were obtained using
Seyferthꢀs reagent in boiling benzene. In the case of 2,2,6,6-tetramethylcyclohexanethione, reaction under PTC
conditions after 3 h yielded only the corresponding dichloromethylidene derivative; on the other hand, workup
after 1 h gave (2,2,6,6-tetramethylcyclohexylidene)methanethione (thioketene 9; Scheme 5).
1. Introduction. ± Various methods are known for the preparation of thiiranes from
different starting materials [1]. For example, thioketones and reactive diazo com-
pounds afford 2,5-dihydro-1,3,4-thiadiazoles, which extrude N to give thiiranes via
2
thiocarbonyl ylides as intermediates [2][3]. On the other hand, less reactive diazo
compounds (e.g., dimethyl diazomalonate) react with thioketones only in the presence
of [Rh (OAc) ] (cf. [4] and refs. cited therein). Whereas in the first case the reaction
2
4
pathway involves a 1,3-dipolar cycloaddition as the key step, the decomposition of the
diazo compound generating a carbenoid initiates the formation of a thiocarbonyl ylide
in the second case. The formation of thiocarbonyl methanides from thioketones and
:
CH , generated by photolysis of CH N , was evidenced by low-temperature experi-
2
2
2
ments in matrices [5].
Dichlorocarbene is one of the best-known and most frequently used carbenes [6]. It
can be formed conveniently by dehydrochlorination of CHCl with strong bases. The
3
most efficient method for its generation is the phase-transfer catalysis (PTC)
elaborated for the preparative organic chemistry by Makosza [7]. However, other
methods which involve thermal decomposition of trichloroacetates and (phenyl)-
(
trichloromethyl)- or (bromodichloromethyl)(phenyl)mercury (Seyferthꢁs reagents)
are also well-known [6].
1)
Presented in preliminary form by G. M. at the 14th International Symposium on the Organic Chemistry of
Sulfur, è o d z 1990.
Postdoctoral stay at the University of Zürich (February 1997 ± July 1998).
In part from the diploma thesis of A. S., University of è o d z , 1996.
2)
3)

Helvetica Chimica Acta ± Vol. 82 (1999)
947
Geminal dichlorothiiranes are only scarcely reported compounds. A long-known
method used for their preparation with only limited application is the reaction of diazo
compounds with thiophosgene (Cl CS) [8]. This method was recently used by Harpp
2
and co-workers to synthesize a series of 3',3'-dichlorospiro[fluorene-9,2'-thiiranes] of
type 1 and related compounds [9] (Scheme 1). In the second reported method for the
synthesis of ꢀgem-dichlorothiiranesꢁ, (bromodichloromethyl)(phenyl)mercury in boil-
ing benzene was used [10]. By this method, thiobenzophenone (2a) was converted into
thiirane 3a (Scheme 1).
Scheme 1
The aim of our present work was to establish a new method for the synthesis of
ꢀ
gem-dichlorothiiranesꢁ starting with thioketones and using PTC conditions. For this
study, we selected the non-enolizable thioketones 2a ± i (cf. Table) to avoid the
4
formation of enethiolates ). Although :CCl generated by PTC methodology was
2
widely used to convert olefins and imines into dichlorocyclopropanes and dichloro-
aziridines, respectively, to the best of our knowledge there are no analogous con-
versions with thiocarbonyl compounds reported (cf. [6][7]).
2
. Results. ± Typically, the two-phase system of the colored solution of a thioketone
2
in CHCl and a concentrated aqueous NaOH solution containing catalytic amounts of
3
benzyl(triethyl)ammonium chloride (TEBA) was stirred at room temperature. The
reactions were in all cases fast, and the color of the starting material disappeared within
3
± 20 min. After usual workup and evaporation of the solvent, thiiranes 3 were
obtained as crystalline, colorless products (Scheme 2, Table).
The thiiranes 3 were characterized by elemental analyses, IR, 13C-NMR, and mass
13
spectra. The signal of CCl in the C-NMR spectrum (C D ) was found at 85 ± 75 ppm,
2
6
6
and all compounds showed a strong C� Cl absorption in the IR spectrum between 780
and 730 cm .
�
1
4)
Stang and Christensen studied the reaction of isopropylidenecarbene with enolizable dialkyl thioketones
and obtained divinyl sulfides as products of the insertion of the carbene into the SH-group of ene-thiols
11].
[

948
Helvetica Chimica Acta ± Vol. 82 (1999)
Scheme 2
Table. 2,2-Dichlorothiiranes 3 and 1,1-Dichloroalkenes 4 Prepared from Thioketones 2 and CHCl
3
under Two-
Phase Conditions
3
4
R
R
2
a
M.p. [8]
Yield [%]
80
M.p. [8]
Yield [%]
Ph
Ph
79 ± 81
59 ± 61
±
b
c
91
82
64 ± 66
37
46
5
8 ± 68
139 ± 140
2 : 1 adducts
cis/trans 4 : 1
d
e
f
65 ± 67
82 ± 83
61
83
63
±
±
105 ± 107
125 ± 1308/12 Torr.
51
46
g
h
i
±
35 ± 378
119 ± 121
±
112 ± 114
80
65
±
By the above-described procedure, 2,2-dichloro-3,3-diphenylthiirane (3a, cf.
5
[
8][10]) was obtained in 80% yield as a stable crystalline material ). Similarly, the
spirocycloaliphatic derivatives 3b ± e were stable and could be stored at room
5)
Thiofluorenone (2i) and 4,4'-dimethoxythiobenzophenone were treated under the same conditions, but we
were not able to isolate the corresponding thiiranes of type 3. Their instability has already been observed
by Harpp and co-workers [9].

Helvetica Chimica Acta ± Vol. 82 (1999)
949
temperature without decomposition. However, in the case of indan derivative 3h, a
spontaneous desulfurization took place at room temperature. After two months, a
crystalline sample of 3h had partially decomposed to afford a ca. 1:1 mixture of 3h
and the corresponding dichloroalkene 4h; the products were separated by chromatog-
raphy.
The spirocyclic dichlorothiirane 3b, which, in the crystalline state, was stable at
room temperature, underwent desulfurization under the conditions of its formation:
after 1 h, the red color of 2b disappeared and 3b could be isolated in 91% yield. The
1
H-NMR spectrum (CDCl ) of 3b showed two singlets at 1.75 and 1.15 ppm for the four
3
Me groups. However, after a reaction time of 7 h, no 3b could be detected by TLC. The
1
H-NMR analysis revealed the presence of dichloroalkene 4b as the main product with
only one signal at 1.35 ppm for all four Me groups. It was accompanied by a minor
product 5 with Me signals at 1.58 and 1.22 ppm. The ratio of 4b/5 was ca. 77:23; after
1
0 h reaction, it changed to 71:29. Chromatographic workup yielded 4b and the new
compound 5; the latter showed no CˆO absorption in the IR spectrum. In the EI-MS,
‡
.
M
appeared at m/z 290, with the characteristic pattern of a compound with four Cl-
atoms, and the elemental analysis confirmed the molecular formula C H Cl O. These
10
12
4
data correspond to a product formed from 2b and two :CCl and elimination of sulfur.
2
Therefore, we proposed the structure of the spirocyclic oxirane 5 (Scheme 3). This
1
3
2
structure was supported by the C-NMR data: two singlets for sp -C-atoms were found
at 148.3 and 113.2 ppm, three singlets for C(2), C(3), and C(4/6) appeared at 88.6, 81.8,
and 48.5 ppm, respectively.
Scheme 3
In the case of 2,2,4,4-tetramethylcyclobutane-1,3-dithione (2c), the color of the
solution disappeared within 1 h, and a mixture of bisthiiranes cis-3c and trans-3c was
6
1
formed (Scheme 4). The cis/trans ratio in the crude mixture was 4 :1 ). In the H-NMR
spectrum (CDCl ), the signal for all four Me groups of trans-3c showed two Me
3
absorptions at 2.02 and 0.86 ppm. When the reaction mixture was stirred for 7 h, two
1
new products 7 and 8, in addition to cis-3c and trans-3c, were identified by H-NMR
spectroscopy. After 14 h stirring, product 7, with Me absorptions at 1.78 and 1.25 ppm,
had disappeared completely. The final product 8, with only one Me absorption at
1.45 ppm, was isolated in 46% yield and was identified as 1,3-bis(dichloromethylidene)-
2
,2,4,4-tetramethylcyclobutane (8; Scheme 4). For the intermediate product, we
propose the structure of 2,2-dichloro-5-(dichloromethylidene)-4,4,6,6-tetramethyl-1-
thiaspiro[2.3]hexane (7).
6)
Separation of cis-3c and trans-3c could be achieved neither by column chromatography nor by
recrystallization. Isolation of the mono-adduct 6 was not attempted.

950
Helvetica Chimica Acta ± Vol. 82 (1999)
Scheme 4
A similar reaction course was observed with 2,2,5,5-tetramethylcyclopentanethione
(2f). To isolate thiirane 3f, the reaction had to be carried out at 0 ± 58 to avoid
desulfurization. A complete elimination of sulfur was observed after 3 h stirring at
room temperature.
With respect to 2f, the homologous cyclohexanethione 2g showed a somewhat
different behavior. After 3 h under PTC conditions at room temperature, chromato-
graphic workup afforded dichloroalkene 4g as the only product (46% yield). All
attempts to isolate the expected thiirane 3g were unsuccessful. Unexpectedly, workup,
7
after 1 h ), by chromatography or distillation, yielded a violet-colored liquid, which, in
�
1
the IR spectrum, showed a very intense absorption band at 1740 cm . By comparison
8
with spectra of an authentic sample ), this product was identified as thioketene 9
9
(
Scheme 5) ). The yield of isolated 9 was rather low, but no other product could be
obtained. In an analogous experiment, we examined the crude mixture by IR
�
1
spectroscopy. When 2g had been completely consumed, no absorption at 1740 cm
could be detected. Therefore, the formation of thioketene 9 must take place during
workup.
To compare scope and limitations of the synthesis of dichlorothiiranes 3 under the
described PTC conditions with Seyferthꢁs procedure, some additional experiments with
7)
8)
After this time, no 2g could be detected by TLC.
We thank Prof. Dr. E. Schaumann, University of Clausthal-Zellerfeld, for kindly providing us with an
original sample and the IR spectrum.
Similarly, the sterically crowded di(tert-butyl) thioketone under analogous conditions gave the
corresponding thioketene in ca. 18% yield.
9)

Helvetica Chimica Acta ± Vol. 82 (1999)
951
Scheme 5
2
a ± c and 2h were carried out. Typically, the reactions were performed with
(
phenyl)(trichloromethyl)mercury in boiling benzene until the color of the thioketone
disappeared (12 ± 24 h). In the case of 2a, workup after 12 h gave dichloroalkene 4a as
the main product (40%) and dichlorothiirane 3a in 9% yield. In addition, 44% of
benzophenone was isolated.
The reaction with monothione 2b afforded thiirane 3b in 84% yield, whereas, in the
case of dithione 2c, monoadduct 6 (cf. Scheme 4) was formed (ca. 10%) along with cis-
3
4
c and trans-3c. Under similar conditions, after 12 h, 2h yielded a 2 :1 mixture of 3h and
h. This result is in accordance with our observation that 3h is less stable than 3b and 3c.
3
. Discussion. ± It is well-known that the two-phase system of CHCl and aqueous
3
�
NaOH in the presence of a quarternary ammonium salt contains :CCl3 and :CCl as
2
reactive species [6][7]. Principally, thioketones are able to react with both reagents.
Therefore, the formation of thiiranes 3 can be rationalized by mechanisms involving
dichlorocarbene or trichloromethyl anion as shown in Scheme 6.
In the case of the ꢀcarbene mechanismꢁ the reaction can occur either as a two-step
process via an intermediate thiocarbonyl ylide A or concerted via a transition state of
type B. It is worth noting that no products of A trapped by thioketones 2 were observed
in our experiments, although, in general, thiocarbonyl ylides easily undergo 1,3-dipolar
cycloadditions with thioketones as dipolarophiles (cf. [12][13]). On the other hand, the
�
reaction pathway via nucleophilic addition of :CCl onto 2 cannot be excluded. In this
3
case, the anion can attack the CˆS group in a carbophilic or a thiophilic fashion to give
intermediates C and D, respectively.
Similar interpretations are conceivable in the case of reactions with Seyferthꢁs
reagent. Furthermore, the dichlorocarbene transfer to thioketones can also occur via a
ꢀ
free carbeneꢁ or via the direct interaction between the organomercury compound and
10
the thioketone (cf. [10]) ).
10)
A procedure for the generation of pure dichlorocarbene is the cheletropic cycloreversion of 11,11-
dichloro-1,6-methano[10]annulene/9,9-dichloro-4a,8a-methanonaphthalene [14]. Because of the very low
yields in the preparation of the precursor, this method is of little importance for preparative work. For an
analogous photochemical generation of dichlorocarbene, see [15].

952
Helvetica Chimica Acta ± Vol. 82 (1999)
Scheme 6
The formation of dichloro alkenes 4 under two-phase conditions results from a
smooth desulfurization of the primarily formed thiiranes 3 (Scheme 2). Based on our
previous results [4] we propose that in this desulfurization :CCl is involved. This
2
electrophilic carbene is especially able to interact with an electron lone pair of the S-
atom. Thiophosgene formed thereafter is immediately hydrolyzed under the basic
conditions.
Scheme 7

Helvetica Chimica Acta ± Vol. 82 (1999)
953
9
The formation of thioketene 9 from sterically crowded dichlorothiirane 3g ) is an
unexpected result. Among the methods for the synthesis of thioketenes, no procedure
involving thiiranes is known [16]. Formally, the transformation 3g ! 9 requires
elimination of Cl , which can be explained by ionic as well as by radical mechanisms
2
(
3
Scheme 7). In both cases, the unsaturated a-chlorosulfenyl chloride 10, an isomer of
1
1
g, may be a key intermediate which, after elimination of Cl , yields 9 ). An anlogous
2
intermediate formed from ꢀgem-dihalodiarylthiiranesꢁ has been proposed to explain
the formation of benzo[b]thiophene derivatives [10].
In conclusion, a new and efficient method for the preparation of 2,2-dichlorothiir-
anes from non-enolizable thioketones under simple two-phase reaction conditions has
been elaborated.
We thank the analytical sections of our institutes for spectra and analyses and Mrs. M. Celeda (University of
è o d z ) for her excellent technical assistance. Financial support of this work by the Polish State Committee for
Scientific Research (KBN grants No. 2 P30305905 and 3T09A00716), the Swiss National Science Foundation,
and F. Hoffmann-La Roche AG, Basel, is gratefully acknowledged. J.R. thanks the Dr. Helmut Legerlotz
Foundation for a scholarship.
Experimental Part
1
. General. M.p.: Determined in a capillary, SMP-20 melting-point apparatus (Aldrich), uncorrected. IR
�
1
1
13
Spectra: Specord-71-IR spectrophotometer, in KBr, in cm . NMR Spectra ( H: 200 or 400 MHz, and C: 50.4
or 100.7 MHz): Varian-Gemini 200 or Bruker-400 spectrometer, in CDCl unless otherwise stated, d in ppm,
3
TMS (ˆ 0 ppm) as internal standard. EI-MS: Finnigan MAT-90 spectrometer; 70 eV. Elemental analyses were
performed in laboratories of the Center of Molecular and Macromolecular Studies, PAN in è o d z and the
University of Zürich.
2
. Starting Materials. Thiobenzophenone (2a) was prepared from benzophenone with Lawessonꢁs reagent
18], 2,2,4,4-tetramethyl-3-thioxocyclobutanone (2b), 2,2,4,4-tetramethylcyclobutane-1,3-dithione (2c), and
adamantanethione (2e) were obtained by thionation of the corresponding ketones with P 10 in pyridine
according to [19][20], 2,2,4,4-tetramethylcyclobutanethione (2d), 2,2,5,5-tetramethylcyclopentanethione (2f),
,2,6,6-tetramethylcyclohexanethione (2g), and 1,1,3,3-tetramethylindan-2-thione (2h) were prepared from the
corresponding ketones in EtOH solns. passing through mixed streams of H S and HCl gas in the presence of
[
2
S
2
2
trimethyl orthoformate as catalyst [20][21]. For the preparation of fluorene-9-thione (2i), a similar procedure
was applied [22], and for di(tert-butyl)thioketone (2j) a protocol involving reaction of di(tert-butyl)ketonimine
lithium salt with CS
triethylamine and benzylchloride [24]. CHCl
. Preparation of ꢁgem-Dichlorothiiranes 3 from Thioketones 2 under PTC Conditions. General Procedure.
A soln. of 2 (5 mmol) in freshly purfied CHCl (10 ml) and an aq. soln. of NaOH (10 ml, 50%) containing 0.2 g
2
was applied [23]. Benzyl(triethyl)ammonium chloride (TEBA) was synthesized from
3
was purified to remove EtOH according to [25].
3
3
of TEBA, was vigorously stirred. When necessary, the reaction flask was placed in a water bath to keep the temp.
below 208. Progress of the reaction was monitored by TLC, and stirring was stopped as soon as no 2 was
detected; reaction times between 10 min and 1 h were needed. The mixtures were poured into H
CH Cl were added, the organic phase was separated, repeatedly washed with H O, dried (CaCl ), filtered, and
evaporated. The brownish residues were separated by CC (SiO ; pentane or petroleum ether, in some cases with
increasing amounts of CH Cl ). Reaction times are given in parentheses, and reported yields refer to isolated 3.
Anal. pure samples were obtained after recrystallization from pentane or MeOH (cooling with dry ice).
2
O, 50 ml of
2
2
2
2
2
2
2
2
,2-Dichloro-3,3-diphenylthiirane (3a) (20min): 1.13 g (80%). M.p. 79 ± 818 (MeOH) ([8]: 89 ± 908). IR:
1
2
980w, 1495m, 1450m, 1110m, 820vs, 780s, 720s. H-NMR (C
C-NMR (C
MS: 282(3), 280(4, M ), 258(39), 210(100, [M � S] ), 178(74), 165(84).
6
D
6
): 7.45 ± 7.4, 7.15 ± 6.9 (2m, 10 arom. H).
1
3
6 6
D ): 139.5 (s, 2 arom. C); 129.9, 129.6, 128.3 (3d, 10 arom. CH); 81.5 (s, C(2)); 67.2 (s,C(3)). EI-
‡
.
‡
11)
2
Sterically crowded a-chlorosulfenyl chlorides have been prepared recently by the reaction of Cl with
corresponding thioketones (cf. [17]). In several cases, an equilibrium with the starting materials was
proposed to explain the instability of a-chlorosulfenyl chlorides (refs. cited in [17]).

954
Helvetica Chimica Acta ± Vol. 82 (1999)
2
,2-Dichloro-4,4,6,6-tetramethyl-1-thiaspiro[2.3]hexan-5-one (3b) (15 min): 1.09 g (91%). M.p. 59 ± 618
1
(
1
2
pentane). IR: 2900s, 1785vs (CˆO), 1450s, 1360m, 1280m, 1150m, 1020m, 915s, 805vs, 760s, 690m. H-NMR:
1
3
.43, 0.91 (2s, 4 Me). C-NMR (C
6
D
6
): 210.5 (s, CˆO); 77.4 (s, C(2)); 72.1 (s, C(3)); 64.8 (s, C(4), C(6)); 23.3,
‡
.
2.1 (2q, 4 Me). EI-MS: 239 (< 1, M ), 205(30), 203(90), 175(69), 133(43), 81(75), 70(100). Anal. calc. for
OS (239.16): C 45.20, H 5.06, Cl 29.65, S 13.41; found: C 45.20, H 5.04, Cl 29.39, S 13.65.
9 2
C H12Cl
cis- and trans-2,2,7,7-Tetrachloro-4,4,8,8-tetramethyl-1,6-dithiadispiro[2.1.2.1]octane (cis-3c and trans-3c,
resp.) (20 min): 1.39 g (82%) as a ca. 4 :1 cis/trans mixture12). M.p. 58 ± 688 (pentane). IR: 2900s, 1460s, 1380s,
1
1
1
7
7
2
250s (br.), 1130w, 1020m, 890m, 820vs (br.), 770vs (br.), 700s, 680s. H-NMR: 2.26, 1.00 (2s, 4 Me of cis-3c);
1
13
.56 (s, 4 Me of trans-3c). H-NMR (C
5.0 (s, 2 CCl ); 74.7 (s, C(3), C(5)); 51.5 (s, C(4), C(8)); 27.8, 21.7 (2q, 4 Me); trans-3c: 78.1 (s, 2 CCl
4.6 (s, C(3), C(5)); 51.6 (s, C(4), C(8)); 29.0 (q, 4 Me). EI-MS: 340(20), 338(38, M ), 336(28), 264(25),
09(67), 207(100), 187(36), 168(52), 133(45), 83(22). Anal. calc. for C10 (338.14): C 35.52, H 3.57,
6
D
6
): 2.02, 0.86 (2s, 4 Me); 1.36 (s, 4 Me). C-NMR (C
6
D
6
): cis-3c:
2
2
);
‡
.
H
4 2
12Cl S
Cl 41.94, S 18.97; found: C 35.74, H 3.62, Cl 42.14, S 18.33.
2
,2-Dichloro-4,4,6,6-tetramethyl-1-thiaspiro[2.3]octane (3d) (10 min): 687 mg (61%). M.p. 65± 678 (MeOH).
1
IR: 2900vs, 1450s, 1365s, 1270s, 1240m, 1180m, 1030w, 920m, 820vs, 765s, 690s. H-NMR: 1.88 (s, CH
.18 (2s, 4 Me). C-NMR (C ): 76.9 (s, C(2)); 49.0 (t, CH
2
); 1.63,
1
3
1
6
D
6
2
); 41.0 (s, C(4), C(6)); 39.3 (s, C(3)); 30.9, 26.6 (2q, 4
Me). Anal. calc. for C H14Cl S (225.18): C 48.00, H 6.27, Cl 31.49, S 14.24; found: C 47.68, H 6.17, Cl 31.23, S 14.38.
9
2
3
,7
3
',3'-Dichlorospiro[tricyclo[3.3.1.1 ]decane-2,2'-thiirane] (3e) (60 min): 1.03 g (83%). M.p. 82 ± 838
1
(
(
3
pentane). IR: 2800s, 1450m, 1360w, 1230m, 1200m, 1110m, 970m, 900m, 800vs, 780s, 750s, 700m. H-NMR
1
3
C
6
D
6
): 1.98, 1.61 (2 br. m, 14 H). C-NMR (C
8.3, 26.9, 26.6 (3d, 4 CH). Anal. calc. for C11
H 5.88, Cl 28.01, S 12.67.
6
D
6
): 84.2 (s, CCl
2 2
); 67.6 (s, C(2)); 37.0, 36.8, 36.4 (3t, 5 CH );
H14Cl S (249.20): C 53.02, H 5.66, Cl 28.45, S 12.87; found: C 53.29,
2
2
,2-Dichloro-4,4,7,7-tetramethyl-1-thiaspiro[2.4]heptane (3f) (2 h): 753 mg (63%). M.p. 105 ± 1078 (MeOH).
1
IR: 2950s, 1470vs, 1370s, 1240m, 1140w, 1010w, 845s, 785vs, 740s, 700m. H-NMR: 1.85 ± 1.7 (m, 2 CH
.03 (2s, 4 Me). C-NMR: 79.7 (s, C(2)); 79.2 (s, C(3)); 46.5 (s, C(4), C(7)); 40.9, 27.2 (2q, 4 Me); 31.2 (t, 2 CH
Anal. calc. for C10
2
); 1.58,
).
S (239.21): C 50.21, H 6.74, Cl 29.64, S 13.40; found: C 50.11, H 6.58, Cl 29.78, S 13.21.
1
3
1
2
H
16Cl
2
3
',3'-Dichloro-1,1,3,3-tetramethylspiro[indan-2,2-thiirane] (3h) (15 min): 1.15 g (80%). M.p. 112 ± 1148
1
(
1
1
2
1
MeOH). IR: 2950s, 1480m, 1450w, 1380m, 1370s, 800vs, 780s, 750vs, 730s. H-NMR: 7.40, 7.18 (2m, 4 arom. H);
1
13
.89, 1.45 (2s, 4 Me). H-NMR (C
6
D
6
): 7.15 ± 7.05, 6.95 ± 6.85 (2m, 4 arom. H); 1.66, 1.27 (2s, 4 Me). C-NMR:
48.6 (s, 2 arom C); 127.8, 121.9 (2d, 4 arom. CH); 78.8, 78.4 (2s, CCl , C(2)); 49.9 (s, C(1), C(3)); 29.8,
8.6 (2q, 4 Me). EI-MS: 287 (2, M ), 286 (15, [M � 1] ), 273(11), 253(10), 251(30), 201(12), 184(15),
57(100), 152(11), 141(20), 115(16). Anal. calc. for C14 S (287.25): C 58.54, H 5.61, Cl 24.68, S 11.16;
2
‡
.
‡
H
16Cl
2
found: C 58.16, H 5.66, Cl 24.58, S 11.12.
Reaction with 9H-Fluorene-9-thione (2i). After 10 min reaction, no 2i could be detected. There was no
thiirane 3i present as the characteristic signals in the 13C-NMR spectrum (CDCl
, 77.3 and 60.3 ppm [9]) were
3
absent. Instead, two signals of an unknown compound 73.9 and 73.3 ppm were observed. The instability of the
expected 3i has already been reported [8][26].
4
. Formation of (Dichloromethylidene)cycloalkanes 4 from Thioketones 2 under PTC Conditions. 4.1.
Reaction of 2b. To a soln. of 2b (780 mg, 5 mmol) in CHCl (10 ml) containing 0.2 g of TEBA, 50% aq. NaOH
soln. (10 ml) was added. The two-phase system was stirred vigorously at r.t. for 7 h. After usual workup and CC
SiO ; petroleum ether with increasing amounts of CH Cl ), two fractions were isolated. Recrystallization
afforded anal. pure samples of 4b and 5; reported yields refer to amounts isolated after CC.
-(Dichloromethylidene)-2,2,4,4-tetramethylcyclobutanone (4b): 367 mg (37%), isolated as the more polar
fraction. M.p. 64 ± 668 (MeOH). IR: 2900m, 1790vs (CˆO), 1650w (CˆC), 1450s, 1180m, 985vs, 900s, 870s,
3
(
2
2
2
3
1
13
8
20w. H-NMR: 1.35 (s, 4 Me). C-NMR: 216.7 (s, CˆO); 146.6 (s, ˆCCl
2
); 114.7 (s, C(3)); 63.8 (s, C(2),
C(4)); 20.2 (q, 4 Me). EI-MS: 207 (1, M ), 180(31), 177(55), 145(23), 143(100), 107(83). Anal. calc. for
O (207.10): C 52.20, H 5.84, Cl 34.24; found: C 52.40, H 6.02, Cl 34.15.
,2-Dichloro-5-(dichloromethylidene)-4,4,6,6-tetramethyl-1-oxaspiro[2.3]hexane (5): 233 mg (17%), isolat-
‡
.
9 2
C H12Cl
2
ed as the less polar fraction. M.p. 98 ± 1008 (pentane). IR: 2900s, 1640s (CˆC), 1460s, 1415m, 1380s, 1260m,
1
13
1
1
2
040s, 1010s, 900vs, 860vs (br.), 820s. H-NMR: 1.58, 1.22 (2s, 4 Me). C-NMR: 148.3 (s, ˆCCl
2
);
‡
.
13.2 (s, (C(5)); 88.6 (s, C(3)); 81.8 (s, C(2)); 20.5, 19.7 (2q, 4 Me). EI-MS: 290(30, M ), 277(40), 275(100),
73(71), 255(25), 253(25), 189(23), 177(26), 175(26), 155(44), 119(20), 101(20), 77(26). Anal. calc. for
C
10
H
12Cl
4
O (290.02): C 41.41, H 4.17, Cl 48.90; found: C 41.74, H 4.37, Cl 49.23.
12)
A similar cis/trans ratio was established in the crude mixture by H-NMR.
1

Helvetica Chimica Acta ± Vol. 82 (1999)
955
4
.2 Reaction of 2c, 2f ± h. The reactions were carried out according to the General Procedure (Exper. 3).
However, the magnetic stirring was continued, until the primarily formed thiirane 3 had disappeared. After
usual workup and evaporation of the solvent, the residue was separated by CC (SiO ; pentane).
2
1
,3-Bis(dichloromethylidene)-2,2,4,4-tetramethylcyclobutane (8) (14 h): 630 mg (46%). M.p. 139 ± 1408
1
(
MeOH). IR (CHCl
C-NMR: 149.6 (s, 2 ˆCCl
3
): 2900s, 1630vs (CˆC), 1460s, 1380s, 1200s, 905vs, 870s. H-NMR: 1.45 (s, 4 Me).
1
3
‡.
2
); 113.0 (s, C(1), C(3)); 50.6 (s, C(2), C(4)); 25.3 (q, 4 Me). EI-MS: 274 (28, M ),
2
72(22), 261(36), 259(96), 241(23), 239(95), 237(100), 223(26), 221(26), 204(20), 202(33), 201(22). Anal.
(274.02): C 43.83, H 4.42, Cl 51.75; found: C 43.55, H 4.59, Cl 51.94.
-(Dichloromethylidene)-2,2,5,5-tetramethylcyclopentane (4f) (3 h): 528 mg (51%), purified additionally
calc. for C10H12Cl
4
1
by bulb-to-bulb distillation at 125 ± 1308/12 Torr. IR (neat): 2880vs, 1600m (CˆC), 1460s, 1370m, 1230m, 920s,
1
13
8
4
1
80m, 860vs, 800w. H-NMR: 1.58 (s, 2 CH
8.1, 47.3 (2s, C(2), C(5)); 41.1, 41.0 (2t, 2 CH
50(45), 135(17), 115(39), 83(100). Anal. calc. for C10
2
); 1.23 (s, 4 Me). C-NMR (C
); 28.8, 26.1 (2q, 4 Me). EI-MS: 207 (1, M ), 171(49), 152(28),
(207.14): C 57.98, H 7.79, Cl 34.23; found: C 57.83,
6
D
6
): 166.6 (s, ˆCCl
2
); 122.6 (s, C(1));
‡
.
2
H
16Cl
2
H 7.65, Cl 34.11.
-(Dichloromethylidene)-2,2,6,6-tetramethylcyclohexane (4g) (3 h): 508 mg (46%). M.p. 35 ± 378 (MeOH/
1
CH
2
Cl
2
). IR (neat): 2890s, 1530m (CˆC), 1470s, 1370m, 1230m, 1160m, 1000m, 900s, 860vs, 790m, 730m.
1
13
H-NMR: 1.48 (br. s, 3 CH
2
); 1.35 (s, 4 Me). C-NMR (C
6
D
6
): 150.9 (s, ˆCCl
2 2
); 119.4 (s, C(1)); 43.8 (t, 2 CH );
‡
.
38.5 (s, C(2), C(6)); 29.2 (q, 4 Me); 17.6 (t, CH
2
). EI-MS: 221(1, M ), 150(18), 143(17), 116(18), 115(27),
(221.17): C 59.74, H 8.20, Cl 32.06; found:
109(17), 96(28), 81(15), 69(100), 55(23). Anal. calc. for C11
H18Cl
2
C 59.91, H 8.34, Cl 31.90.
. Formation of 2-(Dichloromethylidene)-1,1,3,3-tetramethylindan (4h) by Decomposition of 3h. At r.t., 3h
underwent a spontaneous but slow desulfurization. After 2 months, a ca. 1:1 mixture of 3h and 4h was present.
After 8 months, the mixture was separated by CC (SiO ; petroleum ether/CH Cl 8 :2). Yield of 4h: ca. 65%.
5
2
2
2
Colorless crystals. M.p. 119 ± 1218 (MeOH). IR: 2900s, 1570s (CˆC), 1490s, 1460s, 1370m, 1260m, 1130m,
1
13
1
1
2
050w, 1040m, 905s, 870vs, 720vs, 690w. H-NMR: 7.3 ± 7.2, 7.2 ± 7.1 (2m, 4 arom. H); 1.59 (s, 4 Me). C-NMR:
55.1 (s, ˆCCl ); 148.7 (s, 2 arom. C); 127.5, 122.4 (2d, 4 arom. CH); 50.2 (s, C(1), C(3)); 27.4 (q, 4 Me). EI-MS:
55 (3, M ), 241(60), 239(100), 223(13), 221(12), 219(41), 184(19), 152(11). Anal. calc. for C11
2
‡
.
H
14Cl
2
(
255.19): C 65.89, H 6.32; found: C 66.14, H 6.08.
. Formation of Thioketenes 9 from Thioketones under PTC Conditions. (2,2,6,6-Tetramethylcyclohex-
ylidene)methanethione (9). The reaction with 2g (5 mmol) was carried out according to the General Procedure
Exper. 3). After 75 min at r.t., the originally violet color of the mixture turned brownish, and 2g had
6
(
disappeared (TLC). After usual workup, the brown oily residue was separated by CC (SiO
2
; pentane): 100 mg
1
3
8
1
(
12%) of 9
.57 (s, CH
Di(tert-butyl)thioketene. An analogous reaction was carried out with di(tert-butyl)thioketone. TLC
)
, identified by comparison with an authentic sample ). IR (neat): 1740vs (CˆCˆS). H-NMR:
1
2 2
); 1.35 (s, 2 CH ); 1.15 (s, 4 Me).
revealed complete consumption of the starting material after 20 min. However, the violet color of the org. phase
1
remained dominant. H-NMR Analysis (CDCl
3
) of the crude mixture showed a quite complicated pattern of
signals between 2.0 and 1.0 ppm with a dominant s at 1.26 ppm. The IR spectrum of the mixture showed a very
�
1
strong absorption band at 1740 cm . Destillative workup afforded a violet-colored main fraction at 95 ± 1008/
.3 Torr which was identified as di(tert-butyl)thioketene. Subsequent CC (SiO ; pentane) afforded 153 mg
18%). H-NMR: 1.26 (s, 6 Me). C-NMR: 272.5 (s, CˆCˆS); 100.5 (s, CˆCˆS); 31.9 (q, 6 Me). All data
corresponded well to those reported [16b].
. Reactions of Thioketones 2 with (Phenyl)(trichloromethyl)mercury (Seyferthꢁs reagent). A soln. of
0
(
2
1
13
7
PhHgCCl
hexane/CH
PhHgCl was filtered. The clear filtrate was evaporated, and the oily residue was chromatographed (SiO
pentane with increasing amounts of CH Cl
When necessary, additional recrystallization was applied to obtain anal. pure samples.
Reaction with 2b (26 h): CC with hexane/CH Cl 9 :1 afforded 402 mg (84%) of 3b.
Reaction with 2c (24 h): CC afforded mono-adduct 6 as the less polar fraction followed by cis-3c/trans-3c
3
(871 mg, 2.2 mmol) and 2 mmol of 2 in abs. benzene (5 ml) was heated to reflux, until TLC (SiO
2
;
2
Cl
2
8 :2) indicated complete consumption of 2. The mixture was cooled to r.t. and precipitated
2
;
2
2
). Reported yields refer to chromatographically purified products.
2
2
8
:2.
2
,2-Dichloro-4,4,6,6-tetramethyl-1-thiaspiro[2.3]hexane-5-thione (6): 255 mg (50%). Orange crystals. M.p.
53 ± 558 (MeOH). IR: 2970s, 2920m, 1455s (br.), 1410m, 1380m, 1370m, 1360m, 1320s, 1110s, 910m, 810vs (br.),
13)
A similar yield of 9 was obtained after a bulb-to-bulb distillation of the crude mixture at 1008/0.3 Torr.

956
Helvetica Chimica Acta ± Vol. 82 (1999)
7
6
2
70s (br.), 740m. 1H-NMR: 1.81, 1.22 (2s, 4 Me). 13C-NMR: 271 (s, CˆS); 76.9 (s, C(2)); 74.9 (s, C(3));
‡
7.3 (s, C(4), C(6)); 27.5, 26.3 (2q, 4 Me). CI-MS (NH
3
): 256 (43, [M ‡ 1] ), 254(51), 239(18), 221(46),
9 2 2
19(61), 185(14), 183(14), 182(14), 180(15), 103(16), 86(100), 71(18). Anal. calc. for C H12Cl S (255.23):
C 42.35, H 4.74, Cl 27.78, S 25.13; found: C 42.02, H 4.70, Cl 27.59, S 24.95.
Cis- and trans-3c (4 :1): 156 mg (23%). Colorless crystals. M.p. 58 ± 688.
Reaction with 2h (12 h): CC yielded a mixture of 3h and its desulfurization product 4h (2 :1) in a total yield
of ca. 20%.
Reaction with 2a (12 h): CC afforded 3a (50 mg, 9%) and 1,1-dichloro-2,2-diphenylethene (4a) (198 mg,
0%). 4a: Colorless crystals. M.p. 76 ± 778 ([27]: 77 ± 798). Identified by comparison of its spectra and physical
4
properties with those reported in [27]. In addition to 3a and 4a, benzophenone (92 mg, 44%) was isolated as the
most polar fraction.
Reaction with 2e (3 h): After this time, the initially orange color of the mixture changed to black. After
usual workup, no reasonable product could be isolated from the black residue. The only material isolated after
CC was adamantanone (50 mg, 16%).
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[
[
[
[
[
[
[
[
[
[
[
Received March 16, 1999