Reactions of silica chloride (SiO2Cl)/DMSO, a heterogeneous system for the facile regeneration of carbonyl compounds from thioacetals and ring-expansion annelation of cyclic thioacetals

Article abstract of DOI:10.1021/jo016343c

Silica chloride (SiO₂Cl)/DMSO, as a heterogeneous system, has been efficiently used for deprotection of thioacetals into aldehydes in dry CH₂Cl₂ at room temperature. Thioketals without enolizable hydrogens adjacent to a sulfur atom are converted easily to the corresponding ketones in high yields under similar reaction conditions. However, thioketals with enolizable methyl and methylene groups undergo ring-expansion reactions to afford 1,4-dithiepins and 1,4-dithiins in dry CH₂Cl₂ at room temperature in good yields.

Full text of DOI:10.1021/jo016343c

2572
J . Org. Chem. 2002, 67, 2572-2576
Rea ction s of Silica Ch lor id e (SiO2Cl)/DMSO, a Heter ogen eou s
System for th e F a cile Regen er a tion of Ca r bon yl Com p ou n d s fr om
Th ioa ceta ls a n d Rin g-Exp a n sion An n ela tion of Cyclic Th ioa ceta ls
Habib Firouzabadi,* Nasser Iranpoor,* Hassan Hazarkhani, and Babak Karimi
Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71454, Iran
firouzabadi@chem.susc.ac.ir
Received December 4, 2001
Silica chloride (SiO2Cl)/DMSO, as a heterogeneous system, has been efficiently used for deprotection
of thioacetals into aldehydes in dry CH2Cl2 at room temperature. Thioketals without enolizable
hydrogens adjacent to a sulfur atom are converted easily to the corresponding ketones in high
yields under similar reaction conditions. However, thioketals with enolizable methyl and methylene
groups undergo ring-expansion reactions to afford 1,4-dithiepins and 1,4-dithiins in dry CH2Cl2 at
room temperature in good yields.
Sch em e 1
In tr od u ction
Protection of carbonyl groups, as their cyclic thioac-
etals, is an important functional group transformation.
Thioacetals often serve as precursors of acyl anion
equivalents and masked methylene functions (Scheme
1).1 High stability of S,S-acetals in comparison with O,O-
acetals toward different reaction conditions reveals the
significance of thioacetals as protecting groups in organic
synthesis. Conversion of thioacetals at mild reaction
conditions into carbonyl compounds is an important
transformation but is not a straightforward process.
Therefore, a plethora of methods using heavy metal
salts,1 such as HgCl2, HgO/BF3‚Et2O, CAN, SeO2,2 which
are very toxic, nonmetallic reagents such as the oxide of
nitrogen,3a trisethyloxonium tetrafluoroborate,3b and meth-
yl fluorosulfonate,3c are used for this purpose. The
preparation of these reagents and also their handlings
are not so easy, especially for the large-scale operations.
Photolytic methods and electrochemical techniques
have also been used,4 but they require expensive equip-
ment even though they are safe to the environment. Bi-
Sch em e 2
(clayan),6a bis(trifluoroacetoxy)iodobenzene,6b DDQ,6c gal-
lium chloride/H2O or MeOH/O2,6d zirconium sulfenyl
phosphonate {Zr(O3Pme)1.2(O3PC6H4SO3H)0.8},6e a mix-
ture of DMSO with I2,6f HCl/H2O/dioxane,6g trimethylsilyl
chloride (TMSCl),6h and tert-butyl bromide.6i Natural
kaolinitic clay has also been used as a reusable solid
catalyst for the selective dethioacetalization.7 Very re-
cently, reagents for the preparation and cleavage of 1,3-
dithiolanes have been reviewed.8
5a
5b
(NO3)3 and clay-supported Fe(NO3)3 have been suc-
cessfully used in solution and also under solvent-free
conditions for this aim. Some other reported methods
included the use of clay-supported ammonium nitrate
The ring-expansion annelation reactions of cyclic thio-
acetals as 1,3-dithiolanes and 1,3-dithianes can be pri-
marily used for the construction of larger rings containing
sulfur atoms (Scheme 2).
A literature review shows that very few examples of
ring enlargement reactions of 1,3-dithiolanes and 1,3-
* To whom correspondence should be addressed. E-mail: (N.I.)
Iranpoor@chem.susc.ac.ir. Fax: +98(0711)2280926.
(1) (a) Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic
Synthesis, 2nd ed.; Wiley: New York, 1991; pp 178-207. (b) Corey, E.
J .; Seebach, D. Angew. Chem., Int. Ed. Engl. 1965, 4, 1075, 1077. and
J . Org. Chem. 1975, 40, 231. (c) Seebach, D. Angew. Chem., Int. Ed.
Engl. 1969, 8, 639. (d) Grobel, B. T.; Seebach, D. Synthesis 1977, 357.
(e) Bulman Page, P. C.; Van Niel, M. B.; Prodger, J . C. Tetrahedron
1989, 45, 7643. (f) Pettit, G. R.; Van Tamelen, E. E. Org. React. 1962,
12, 356.
(6) (a) Meshram, H. M.; Reddy, S. G.; Yadav, J . S. Tetrahedron Lett.
1997, 38, 8891. (b) Stork, G.; Zhao, K. Tetrahedron Lett. 1989, 30, 287.
(c) Tanemura, K.; Dohya, H.; Imamura, M.; Suzuki, T.; Horaguchi, T.
J . Chem. Soc., Perkin Trans. 1 1996, 453. (d) Saigo, K.; Hashimoto,
H.; Kihara, N.; Umehara, H.; Hasegawa, M. Chem. Lett. 1990, 831.
(e) Curini, M.; Marcotullio, M. C.; Pisani, E.; Rosati, O. Synlett 1997,
769. (f) Chattopadhyaya, J . B.; Rao, A. V. R. Tetrahedron Lett. 1973,
38, 3735. (g) Prato, M.; Quintily, U.; Scorrano, G.; Sturaro, A. Synthesis
1982, 679. (h) Olah, G. A.; Narang, S. C.; Mehrotra, A. K. Synthesis
1982, 965. (i) Olah, G. A.; Narang, S. C.; Mehrotra, A. K. Synthesis
1982, 151.
(2) Haroutounian, S. A. Synthesis 1995, 39.
(3) (a) Mehta, G.; Uma, R. Tetrahedron Lett. 1996, 37, 1879. (b)
Oishi, T.; Kamemoto, k.; Ban, Y. Tetrahedron Lett. 1972, 11, 1085. (c)
Fetizon, M.; J urion, M. J . Chem. Soc., Chem. Commun. 1972, 382.
(4) (a) Nakamura, C. Y.; Satoh, J . Y. J . Chem. Soc., Chem. Commun.
1977, 680. (b) Epling, G. A.; Wang, Q. Tetrahedron Lett. 1992, 33, 5909.
(c) Kamata, M.; Murakami, Y.; Tamagawa, Y.; Kato, M.; Hasegawa,
E. Tetrahedron 1994, 50, 12821. (d) Porter, Q. N.; Utley, J . H. P. J .
Chem. Soc., Chem. Commun. 1978, 255.
(5) (a) Komatsu, N.; Tanguchi, A.; Uda, M.; Suzuki, H. Chem
Commun. 1996, 1847. (b) Balogh, M.; Corne´lis, A.; Laszlo, P. Tetra-
hedron Lett. 1984, 25, 3313.
(7) Bandgar, B. P.; Kasture, S. P. Green Chem. 2000, 2, 154.
(8) Banerjee, A. K.; Laya, M. S. Russ. Chem. Rev. 2000, 69, 947-
955.
10.1021/jo016343c CCC: $22.00 © 2002 American Chemical Society
Published on Web 03/19/2002

Reactions of SiO2Cl/DMSO
Sch em e 3
J . Org. Chem., Vol. 67, No. 8, 2002 2573
Sch em e 4
dithianes are reported. Treatment of 1,3-dithiolanes and
1,3-dithianes with phenyl selenyl chloride (PhSeCl)
resulted in ring-expansion reactions in some steroidal
compounds.9 2,2-Dimethyl-1,3-oxathiolane with chlorine
in a refluxing mixed solvent, CH2Cl2/CCl4, produced
2-methyl-1,4-oxathiene in only 54% isolated yield. This
method has also been used successfully for other com-
pounds.10 TeCl4 has also mediated the ring-expansion
reactions of 1,3-dithiolanes, 1,3-dithianes, and 1,3-ox-
athiolanes.11
Ta ble 1. Dep r otection of Th ioa ceta ls w ith SiO2Cl/DMSO
in CH2Cl2
In recent years, we have been involved in exploring
some new applications of tungsten hexachloride (WCl6),
molybdenum pentachloride (MoCl5), and zirconium tet-
rachloride (ZrCl4) in organic synthesis.12 Along this line,
we have found that WCl6 and MoCl5 in the presence of
DMSO are efficient reagents for the facile deprotection
of thioacetals and one-pot ring-expansion and ring-
expansion chlorination of cyclic thioacetals. Ring-expan-
sion chlorination reaction is the first reported in the
literature (Scheme 3).
Silica gel treated with thionyl chloride has been used
as a catalyst for the selective thioacetalization of carbonyl
compounds.13 We have recently reported a modified
procedure for the production of a highly efficient silica
chloride that has been used for the transthioacetalization
of acetals, transformation of acylals into thioacetals, and
dehydration of tertiary benzylic alcohols to olefins.14 Now
we report dethioacetalization of thioacetals into carbonyl
compounds, ring-expansion annelation, and one-pot ring-
expansion chlorination of cyclic thioacetals using solid
silica chloride (SiO2Cl) in the presence of DMSO.
a
b
Isolated yields. Structures are confirmed by IR, 1H NMR, 13
C
NMR, and mp/bp. c GC purity >95%. The ratio of the substrate/
SiO2Cl/DMSO was 1 mmol/1.4 g/6-8 mmol.
d
1r). 2-Cinnamyl-1,3-dithiane and its 1,3- dithiolane de-
rivative were successfully converted to cinnamaldehyde
in high yields (Table 1, entries 1l and 1m). In these
reactions silica chloride acts as an oxophilic and activat-
ing reagent for DMSO to generate dimethylsulfonium
chloride. DMSO also acts as a source of oxygen in these
reactions. We believe that dimethylsulfonium chloride is
the responsible intermediate for these reactions to occur.
Therefore, we have generated this active species by
independent known methods6h,15 and added it to the
solution of 2-(4-toluyl)-1,3-dithiane to obtain toluyl alde-
hyde in a high yield. In all reactions, a sticky polymeric
material plus fast liberation of dimethyl sulfide was also
detected. Therefore, we have proposed a mechanism in
which the role of DMSO, silica chloride, and dimethyl-
sulfonium chloride in the dethioacetalization reactions
is clarified (Scheme 5).
Thioacetals derived from ketones show quite a different
behavior. In the case of thioacetals derived from ketones
without enolizable hydrogen, deprotection proceeded very
well to give the corresponding ketones in high yields
(Table 1, entries 1n-1o) in CH2Cl2 at room temperature.
It is important to note that cyclic thioacetals derived from
ketones with enolizable hydrogen rearranged to the
corresponding dihydro-1,4-dithiins or -1,4-dithiepins in
good yields (Scheme 6, Table 2).
Resu lts a n d Discu ssion
Silica chloride can be prepared very easily from cheap
starting materials with high yields. This solid polymeric
compound is a mild oxophilic reagent, and its handling
is much easier than those of SOCl2 and TMSCl, which
have toxic and corrosive vapors. In this study we have
applied SiO2Cl/DMSO as a new heterogeneous system for
deprotection of thioacetals into aldehydes in dry CH2Cl2
at room temperature (Scheme 4, Table 1). The reactions
were easy and clean and proceeded under mild reaction
conditions in high yields.
As shown in Table 1, open-chain and cyclic thioacetals
(1,3-dithiolanes or 1,3-dithianes) of aromatic aldehydes
were cleanly converted into their corresponding alde-
hydes in excellent yields (Table 1, entries 1a-1k, 1q, and
(9) Francisco, C. G.; Freire, R.; Hernandez, R.; Salazar, J . A.; Suarez,
E. Tetrahedron Lett. 1984, 25, 1621.
(10) Wilson, G. E. J . Am. Chem. Soc. 1965, 87, 3785.
(11) (a) Tani, H.; Inamasu, T.; Tamura, R.; Suzuki, H. Chem. Lett.
1990, 1323. (b) Tani, H.; Inamasu, T.; Masumoto, K.; Tamura, R.;
Shimizu, H.; Suzuki, H. Phosphorus, Sulfur Silicon 1992, 67, 261.
(12) (a) Firouzabadi, H.; Iranpoor, N.; Karimi, B. Synlett 1998, 739.
(b) Firouzabadi, H.; Iranpoor, N.; Karimi, B. Synlett 1999, 319 and
413. (c) Firouzabadi, H.; Karimi, B. Phosphorus, Sulfur Silicon, in
press. Firouzabadi, H.; Karimi, B. Phosphorus, Sulfur Silicon, in press.
(d) Firouzabadi, H.; J amalian, A. Phosphorus, Sulfur Silicon 2001, 170,
211.
When silica chloride was added to the solution of
2-methyl-2-phenyl-1,3-dithiane and DMSO in dry CH2-
(14) (a) Firouzabadi, H.; Iranpoor, N.; Karimi, B.; Hazarkhani, H.
Synlett 2000, 263. (b) Firouzabadi, H.; Iranpoor, N.; Hazarkhani, H.
Posphorus, Sulfur Silicon, in press. (c) Firouzabadi, H.; Iranpoor, N.;
Hazarkhani, H.; Karimi, B. Synth. Commun., in press.
(13) Kamitori, Y.; Hojo, M.; Masuda, R.; Kimura, T.; Yoshida, T. J .
Org. Chem. 1986, 51, 1427.
(15) (a) Corey, E. J .; Kim, C. U. Tetrahedron Lett. 1973, 12, 919. (b)
Omura, K.; Swern, D. Tetrahedron 1978, 34, 1651.

2574 J . Org. Chem., Vol. 67, No. 8, 2002
Firouzabadi et al
Sch em e 5
Ta ble 2. Rin g-Exp a n sion Ch lor in a tion of 1,3-Dith iola n es
a n d 1,3-Dith ia n es by SiO2Cl/DMSO in CH2Cl2
Sch em e 6
Cl2, 2-chloro-3-phenyl-5,6,7-trihydro-1,4-dithiepin was
produced in a high yield (Table 2, entry 3a). When we
applied a similar reaction to 1,3-dithianes and 1,3-dithio-
lanes derived from different acetophenones, ring-expan-
sion chlorination reaction also proceeded very smoothly
and the chlorinated products were obtained in good to
high yields (Table 2, entries 3a-3f). 2-Methyl-2-(4-meth-
oxyphenyl)-1,3-dithiolane undergoes ring-expansion chlo-
rination and dethioacetalization reactions to produce the
expected products in 27% and 65-70% yields, respec-
tively (Table 2, entry 3g). However, the presence of a nitro
group as a strong electron-withdrawing group on the aro-
matic ring (Table 2, entries 3h and 3i) effectively retards
the chlorination reaction, and only the rearrangement
products 4h and 4i were obtained in 89% and 87%, res-
pectively. This observation indicates that cationic inter-
mediates may be involved in the formation of the chlor-
inated products. In addition, in all reactions in this study,
fast liberation of dimethyl sulfide was also detected.
Therefore, we proposed a mechanism in which the role
of DMSO, the cationic character of the reaction interme-
diates, and the formation of the chlorinated products are
clarified (Scheme 7).
We have also extended the application of the method
to thioacetals prepared from ketones with enolizable
methylene groups to prepare different derivatives of 1,4-
dithiepins and 1,4-dithiins. For this purpose several 1,3-
dithiolanes and a 1,3-dithiane were synthesized and sub-
jected to SiO2Cl/DMSO in CH2Cl2 at room temperature.14
We have found that 2,2-bisbenzyl-1,3-dithiolane was con-
verted successfully to 2-phenyl-3-benzyldihydro-1,4-
dithiin as a purple-red viscous liquid in 75% yield (Table
3, entry 3j). 2-Ethyl-2-phenyl-1,3-dithiolane under similar
reaction conditions was converted to 2-methyl-3-phenyl-
a
Yields refer to isolated product. b The molar ratio of substrates/
SiO2Cl/DMSO was 1 mmol/1.8 g/3-4 mmol.
dihydro-1,4-dithiin as an off white oil in 80% yield (Table
3, entry 3k). 1,3-Dithiolane derived from 4-phenylcyclo-
hexanone was converted into its corresponding dithiin

Reactions of SiO2Cl/DMSO
J . Org. Chem., Vol. 67, No. 8, 2002 2575
Sch em e 7
Ta ble 3. P r ep a r a tion of Su bstitu ted 1,4-Dith iin s a n d
Dith iep in s by Rin g-Exp a n sion Rea ction s of
2,2-Su bstitu ted 1,3-Dith iola n es a n d 1,3-Dith ia n es in th e
P r esen ce of SiO2Cl/DMSO in CH2Cl2
expected, 2-methyl-3-benzoyldihydro-1,4-dithiin was iso-
lated as a light green oily compound in 87% yield (Table
3, entry 3m). 1,3-Dithane derived from R-tetralone was
also rearranged into the corresponding dithiepin in 60%
yield as a red oily compound (Table 3, entry 3n).
The reactions proceeded cleanly without the formation
of polymeric materials at room temperature. However,
the amounts of polymeric materials and carbonyl com-
pounds increase at higher temperatures. This method
does not work properly for aliphatic thioacetals and
always gives a mixture of products that are not identified.
Con clu sion s
In conclusion, we have introduced a new method for
the deprotection of thioacetals derived from aldehydes
and ketones without enolizable hydrogens. We have also
shown that, by this method, cyclic thioacetals with
enolizable hydrogens undergo ring-expansion, one-pot
ring-expansion chlorination, and ring-expansion anne-
lation reactions with good yields. We believe that this
method is general and could be employed for the syn-
thesis of complex derivatives of dithiins and dithiepins.
Exp er im en ta l Section
Gen er a l P r oced u r e for Deth ioa ceta liza tion of Th io-
a ceta ls a n d Th iok eta ls w ith DMSO/SiO2Cl in CH2Cl2. To
a solution of 1,3-dithiolanes or 1,3-dithianes, substituted
benzaldehyde (2 mmol), and dry DMSO (12-16 mmol) in dry
CH2Cl2 (25 mL) was added silica chloride (2.8 g), and the
resulting mixture was stirred at room temperature. The
progress of the reaction was monitored by TLC. After comple-
tion (30-95 min), the reaction was quenched with an aqueous
solution of NaOH (10%, 25 mL) and extracted with CH2Cl2.
The organic extracts were combined together, washed succes-
sively with brine and water, separated, and dried over
anhydrous Na2SO4. The solvent was evaporated under reduced
pressure to afford the almost pure product(s). Further puri-
a
Yields refer to isolated products. b The molar ratio of substrates/
SiO2Cl/DMSO was 1 mmol/1.2 g/3-4 mmol.
as an off white oily material in 65% yield (Table 3, entry
3l).
To show that the methylene groups with more enoliz-
able hydrogen undergo rearrangement reactions, we have
selectively prepared 2-methyl-2-(benzoylmethyl)-1,3-
dithiolane.16 Then, this compound was reacted with SiO2-
Cl/DMSO in CH2Cl2 at room temperature, and as was
(16) Firouzabadi, H.; Iranpoor, N.; Amani, K. Synthesis 2002, 59-
62.

2576 J . Org. Chem., Vol. 67, No. 8, 2002
Firouzabadi et al
fication was achieved by column chromatography on silica gel
(eluent, petroleum ether (60-80 °C)/EtOAc, 5/1) to give the
desired product(s) in good to excellent yields (Table 1, entries
1a-1r; 88-96%).
10H); 13C NMR (CDCl3, 63 MHz) δ ) 29.25, 31.28, 41.55,
124.37, 127.18, 127.58, 128.29, 128.66, 129.77, 130.05, 139.65,
140.12, 145.75; MS (20 eV) m/z (relative intensity) 284 (M+,
100), 223 (M+ - SC2H5, 28.5), 191 (23.4), 121 (31.5), 91 (28.6).
CHN Anal: C (calcd 71.78, found 71.45), H (calcd 5.67, found
5.64).
R in g-E xp a n sion Ch lor in a t ion of 2-P h en yl-2-m et h yl-
1,3-d ith iola n e to th e Cor r esp on d in g Ch lor in a ted Dih y-
d r o-1,4-d ith iin w ith SiO2Cl/DMSO in Dr y CH2Cl2 a s a
Typ ica l P r oced u r e. To a solution of 2-phenyl-2-methyl-1,3-
dithiolane (0.40 g, 2 mmol) and dry DMSO (0.47 g, 8 mmol) in
dry CH2Cl2 (25 mL) was added silica chloride (3.6 g), and the
resulting mixture was stirred at room temperature. The
progress of the reaction was monitored by TLC (CCl4 as
eluent). After completion (80 min), the reaction was quenched
with an aqueous solution of NaOH (10%, 25 mL) and extracted
with CH2Cl2. The organic extracts were washed successively
with brine and water, separated, and dried over anhydrous
Na2SO4. The solvent was evaporated under reduced pressure
to afford the crude product. Further purification was achieved
by column chromatography using a short column of silica gel
(CCl4 as eluent) to afford the desired pure product as a light
brown oily compound (Table 2, entry 3a; 0.34 g, 80% yield):
1H NMR (CDCl3, 250 MHz) δ ) 3.10 (m, 4H), 7.18 (m, 5H);
13C NMR (CDCl3, 63 MHz) δ ) 30.21, 32.20, 113.14, 126.28,
128.36, 128.46, 129.67, 145.75 ppm; MS (20 eV) m/z (relative
intensity) 230 (M+ + 2, 25.2), 228 (M+, 74.0), 200 (M+ - CH2d
CH2, 26.3), 165 (36.3), 121 (100), 77 (15.9).
Da ta for 2-Meth yl-3-p h en yld ih yd r o-1,4-d ith iin (4k ): off
1
white oil; 0.33 g, 80% yield; H NMR (CDCl3, 250 MHz) δ )
1.82 (s, 3H), 3.27 (m, 4H), 7.18-7.37 (m, 5H); 13C NMR (CDCl3,
63 MHz) δ ) 22.51, 29.73, 30.09, 121.12, 124.60, 127.92,
128.21, 129.99, 140.29; MS (20 eV) m/z (relative intensity) 208
(M+, 100), 180 (M+ - C2H4, 22.9), 147 (M+ - SC2H5, 31.4), 121
(44.7). CHN Anal.: C (calcd 63.42, found 63.22), H (calcd 5.81,
found 5.80).
1
Da ta for Dith iin (4l): off white oil; 0.37 g, 65% yield; H
NMR (CDCl3, 250 MHz) δ ) 1.89-1.97 (m, 2H), 2.29-2.34 (m,
4H), 2.81-3.10 (m, 1H), 3.20-3.47 (m, 4H), 7.17-7.35 (m, 5H);
13C NMR (CDCl3, 63 MHz) δ ) 28.79, 30.54, 34.08, 40.13,
41.39, 43.27, 119.36, 119.69, 126.53, 126.74, 128.88, 145.93;
MS (20 eV) m/z (relative intensity) 248 (M+, 100), 189 (9.9),
149 (13.9), 144 (51.1), 131 (89.2), 105 (27.2), 91 (10.2). CHN
Anal.: C (calcd 67.92, found 67.85), H (calcd 6.49, found 6.45).
Da ta for 2-Meth yl-3-ben zoyld ih yd r o-1,4-d ith iin (4m ):
1
light green oil; 0.41 g, 87% yield; H NMR (CDCl3, 250 MHz)
δ ) 1.88 (s, 3H), 3.10-3.27 (m, 4H), 7.34-7.52 (m, 3H), 7.80-
7.89 (m, 2H); 13C NMR (CDCl3, 63 MHz) δ ) 23.33, 27.35,
32.74, 121.85, 128.41, 129.00, 130.01, 133.75, 137.16, 193.70;
Gen er a l P r oced u r e for th e Rin g Exp a n sion of 2,2-
Disu bstitu ted Th ioa ceta ls to th e Cor r esp on d in g Dih y-
d r o-1,4-d ith iin a n d Dith iep in s w ith SiO2Cl/DMSO in Dr y
CH2Cl2. To a solution of 2,2-disubstituted thioacetals (2 mmol)
and dry DMSO (0.35 g, 6 mmol) in dry CH2Cl2 (25 mL) was
added silica chloride (2.4 g), and the resulting mixture was
stirred at room temperature. After completion (1.6-2 h,
monitored by TLC, eluent CCl4), the reaction was quenched
with an aqueous solution of NaOH (10%, 25 mL), and extracted
with CH2Cl2. The organic extracts were combined together,
washed successively with brine and water, separated, and
dried over anhydrous Na2SO4. The solvent was evaporated
under reduced pressure to afford the crude products. Further
purification was achieved by preparative thin-layer chroma-
tography (CCl4 as eluent) to afford pure products (Table 3,
entries 4j-4n; 60-87%).
MS (20 eV) m/z (relative intensity) 236 (M+, 62.2), 176 (M+
-
SC2H4, 22.5), 147 (5.0), 119 (25.9), 105 (100), 77 (32.9). CHN
Anal.: C (calcd 60.98, found 61.01), H (calcd 5.12, found 5.12).
Dith iep in (4n ): break oily compound; 0.28 g, 60% yield;
1H NMR (CDCl3, 250 MHz) δ ) 1.80-1.92 (m, 1H), 2.14-2.18
(m, 1H), 2.39-2.42 (m, 1H), 2.68-2.87 (m, 5H), 3.22-3.28 (m,
2H), 7.05-7.77 (m, 4H); 13C NMR (CDCl3, 63 MHz) δ 29.14,
30.91, 32.41, 34.20, 37.38, 124.41, 126.86, 128.66 133.73,
135.08, 136.04, 136.60, 140.94; MS (20 eV) m/z (relative
intensity) 234 (M+, 100), 205 (7.6), 160 (9.3), 129 (10.1), 115
(7.7), 73 (6.9). CHN Anal.: C (calcd 66.62, found 66.45), H
(calcd 6.02, found 6.01).
Ack n ow led gm en t. We are thankful to the Shiraz
University Research Council for the partial support of
this work.
Da t a for 2-P h en yl-3-b en zyld ih yd r o-1,4-d it h iin (4j):
1
purple-red viscous liquid; 0.43 g, 75% yield; H NMR (CDCl3,
250 MHz) δ ) 3.18-3.26 (m, 4H), 3.49 (s, 2H), 7.18-7.48 (m,
J O016343C