Regioselectivity of the 1,3-oxathiolane formation in the Lewis acid-catalyzed reaction of thioketones with asymmetrically substituted oxiranes

Article abstract of DOI:10.1002/1522-2675(20011114)84:11<3319::AID-HLCA3319>3.0.CO;2-L

The reactions of the aromatic thioketone 4,4′-dimethoxythiobenzophenone (1) with three monosubstituted oxiranes 3a-c in the presence of BF₃ · Et₂O or SnCl4 in dry CH₂Cl₂ led to the corresponding 1:1 adducts, i.e., 1,3-oxathiolanes 4a-b with R at C(5) and 8c with Ph at C(4). In addition, 1,3-dioxolanes 7a and 7c, and the unexpected 1:2 adducts 6a-b were obtained (Scheme 2 and Table 1). In the case of the aliphatic, nonenolizable thioketone 1,1,3,3-tetramethylindane-2-thione (2) and 3a-c with BF₃ · Et₂O as catalyst, only 1:1 adducts, i.e. 1,3-oxathiolanes 10a-b with R at C(5) and 11a-c with R or Ph at C(4), were formed (Scheme 6 and Table 2). In control experiments, the 1:1 adducts 4a and 4b were treated with 2-methyloxirane (3a) in the presence of BF₃ · Et₂O to yield the 1:2 adduct 6a and 1:1:1 adduct 9, respectively (Scheme 5). The structures of 6a, 8c, 10a, 11a, and 11c were confirmed by X-ray crystallography (Figs. 1-5). The results described in the present paper show that alkyl and aryl substituents have significant influence upon the regioselectivity in the process of the ring opening of the complexed oxirane by the nucleophilic attack of the thiocarbonyl S-atom: the preferred nucleophilic attack occurs at C(3) of alkyl-substituted oxiranes (O-C(3) cleavage) but at C(2) of phenyloxirane (O-C(2) cleavage).

Full text of DOI:10.1002/1522-2675(20011114)84:11<3319::AID-HLCA3319>3.0.CO;2-L

Helvetica Chimica Acta Vol. 84 (2001)
3319
Regioselectivity of the 1,3-Oxathiolane Formation in the Lewis Acid-
Catalyzed Reaction of Thioketones with Asymmetrically Substituted
Oxiranes
by Changchun Fu1), Anthony Linden, and Heinz Heimgartner*
Organisch-chemisches Institut der Universit‰t Z¸rich, Winterthurerstrasse 190, CH-8057 Z¸rich
¬
Dedicated to Professor Andre M. Braun on the occasion of his 60th birthday
The reactions of the aromatic thioketone 4,4'-dimethoxythiobenzophenone (1) with three monosubstituted
oxiranes 3a c in the presence of BF3 ¥ Et2O or SnCl4 in dry CH2Cl2 led to the corresponding 1:1 adducts, i.e., 1,3-
oxathiolanes 4a b with R at C(5) and 8c with Ph at C(4). In addition, 1,3-dioxolanes 7a and 7c, and the
unexpected 1:2 adducts 6a b were obtained (Scheme 2 and Table 1). In the case of the aliphatic, nonenolizable
thioketone 1,1,3,3-tetramethylindane-2-thione (2) and 3a c with BF3 ¥ Et2O as catalyst, only 1:1 adducts, i.e.
1,3-oxathiolanes 10a b with R at C(5) and 11a c with R or Ph at C(4), were formed (Scheme 6 and Table 2). In
control experiments, the 1:1 adducts 4a and 4b were treated with 2-methyloxirane (3a) in the presence of BF3 ¥
Et2O to yield the 1 :2 adduct 6a and 1 :1:1 adduct 9, respectively (Scheme 5). The structures of 6a, 8c, 10a, 11a,
and 11c were confirmed by X-ray crystallography (Figs. 1 5). The results described in the present paper show
that alkyl and aryl substituents have significant influence upon the regioselectivity in the process of the ring
opening of the complexed oxirane by the nucleophilic attack of the thiocarbonyl S-atom: the preferred
nucleophilic attack occurs at C(3) of alkyl-substituted oxiranes (OÀC(3) cleavage) but at C(2) of phenyl-
oxirane (OÀC(2) cleavage).
1. Introduction. 1,3-Oxathiolanes are easily prepared via the Lewis acid catalyzed
reaction of oxiranes with thioketones. This direct formation of 1,3-oxathiolanes is
favorable, because oxiranes as well as thiocarbonyl derivatives are easily accessible. In
our recent publications, the reactions of 1,3-thiazole-5(4H)-thiones [1][2], trithiocar-
bonates [3], aromatic thioketones, and nonenolizable aliphatic thioketones [4][5] with
mono- and disubstituted oxiranes were described as a new access to 1,3-oxathiolanes.
Different regioselectivities were observed in the reactions of 1,3-thiazole-5(4H)-
thiones and trithiocarbonates with alkyl- and aryl-oxiranes, respectively.
For the Lewis acid catalyzed addition of oxiranes to CˆS bonds to form 1,3-
oxathiolanes, the following mechanisms were proposed (Scheme 1): the O-atom of the
oxirane forms a complex with the Lewis acid (e.g., BF3), whereby positive charges at
the two C-atoms of the oxirane develop. This facilitates the nucleophilic attack by the
thiocarbonyl S-atom. The oxirane complex A reacts with the CˆS bond via an Sn2-type
process to form B and D, whereby the preferred attack occurs at C(3) of the oxirane
because of steric factors, i.e., B is favorably formed. The cyclizations of B or D, and
subsequent release of the Lewis acid lead to the 5-alkyl derivative C as the major and
the 4-alkyl derivative E as the minor products. In contrast, the Ph group in the oxirane
1
)
Diploma thesis of C. F., Universit‰t Z¸rich, 2001.

3320
Helvetica Chimica Acta Vol. 84 (2001)
Scheme 1
complex F favors a primary ring opening to yield G, which is attacked by the
thiocarbonyl S-atom. The mechanism for the formation of H and, therefore, of I
corresponds to an Sn1-type reaction due to the stabilization of the positive charge by p-
conjugation. According to the postulated mechanism, the stability of the intermediates
B, D, and H might determine the rate of the reactions, i.e., the more easily the
intermediates are formed, the faster the reactions would proceed.
To obtain more insight into the regioselectivity of the ring opening of oxiranes in the
formation of 1,3-oxathiolanes and, in particular, to establish the influence of alkyl and
aryl substituents, reactions of asymmetrical Me-, Bu-, and Ph-substituted oxiranes with
nonenolizable thioketones were carried out. In the present paper, the results of the
reactions with 4,4'-dimethoxythiobenzophenone (1) and 1,1,3,3-tetramethylindane-2-
thione (2) are described.
2. Results. 2.1. Reactions of 4,4'-Dimethoxythiobenzophenone (1) with Oxiranes.
On dropping 5 equiv. of 2-methyloxirane (3a) into a solution of 1 and 1.1 equiv. BF3 ¥
Et2O in dry CH2Cl2 at À788 under N2, the violet solution turned rapidly to light yellow.
After 1 min, the reaction was quenched with H2O. Chromatographic separation gave
1:1 adduct 4a and 4,4'-dimethoxybenzophenone (5) in 27 and 68% yield, respectively,
as well as an unexpected 1:2 adduct 6a in 2% yield. The reaction was repeated at À908
and 08, whereby 4a, 5, and 6a were obtained in 17, 62, and 10%, and in 1, 80, and 1%
yields, respectively. In addition, a second unusual product 7a was isolated in 14% yield
from the reaction performed at 08 (Scheme 2 and Table 1).
The structures of 4a and 7a were assigned by means of elemental analyses, MS, 1H- and 13C-NMR spectra,
and by comparison with the analogues described previously [1 5]. The novel product 6a corresponds to a 1:2
adduct, a 1,3-dioxa-6-thiacyclooctane on the basis of elemental analysis, and CI- and ESI-MS spectra. The NMR

Helvetica Chimica Acta Vol. 84 (2001)
3321
Scheme 2
Table 1. BF3- and SnCl4-Catalyzed Reactions of 1 with 3 in CH2Cl2
3
a
R
Temp. [8]
Yields [%] of Products
4
5
6
7
8
BF3 ¥ Et2O
Me
À 90
17
682
1
4
74
62
10
À 7827
0
80
84
3
1
7
14
b
Bu
À 90
À 7822
À 78
c
a
b
c
Ph
Me
Bu
Ph
76
10
13
SnCl4
À 7852
À 7825
À 78
26
42
1
3
27
71
1
data are in agreement with the structure of the eight-membered ring of type 6; the H- and 13C-NMR spectra
indicate a symmetric molecule. The compound shows an uncommon broad signal in the 1H-NMR spectrum for
the H-atoms of the Ph group between 7.80 7.40 ppm and a d (J ˆ 8.5 Hz) at 6.76 ppm. For the two MeO groups
only one s appears at 3.29 ppm. The 13C-NMR spectrum shows 2 s at 159.4 and 136.1 ppm, 1 br. d at 129.0 ppm
and 1 d at 113.3 ppm for two Ph groups, as well as only 1 q at 54.6 ppm for two MeO. All these data indicate a
symmetric molecule. Apart from that, one fine-structured m for two CH(Me)O appears at ca. 4.0 ppm in the
1H-NMR spectrum, while the protons of two CH2S groups absorb as 2 dd at 2.74 and 2.46 ppm. The latter signals
present the typical values of geminal coupling (14.6 Hz), and cis- and trans-coupling (3.0 and 5.5 Hz) in eight-
membered rings. The signal intensities of CH(Me)O and MeO are in a ratio of 1 :3. The structure of 6a has been
confirmed by X-ray crystal-structure analysis (see Fig. 1).

3322
Helvetica Chimica Acta Vol. 84 (2001)
Fig. 1. ORTEP Plot [6] of one of the two symmetry-independent molecules of 6a (arbitrary numbering of the
atoms; 50% probability ellipsoids)
It is worth mentioning how the most important ions in the CI-MS, and the ions
‡
‡
‡
[M ‡ MeOH ‡ Na] , [M ‡ K] , and [M ‡ Na] in the ESI-MS spectra of 6a could be
formed (Scheme 3).
Analogously, the BF3 ¥ Et2O-catalyzed reaction of 1 with 3b at À788 led to 4b, 5, and
6b in 22, 74, and 3% yields, respectively. In the 1H-NMR spectrum, the 1:2 adduct 6b
also shows signals for the CH2S group with typical values of geminal coupling
(14.6 Hz), and cis- and trans-coupling (3.2 and 5.3 Hz) in eight-membered rings. In the
‡
ESI-MS the most important peaks appear at m/z 513 ([M ‡ MeOH ‡ Na] ), 481
‡
‡
([M ‡ Na] ), and 497 ([M ‡ K] ). When the same reaction was performed at À908,
the yield of 6b increased to 7%.
The corresponding reaction of 1 with 3c at À788 led to 8c, 5, and the unusual
product 7c in 13, 76, and 10% yields, respectively (see Scheme 2 and Table 1).
The structures of 4b, 6b, 7c, and 8c were assigned on the basis of the elemental
analyses, NMR and MS data, and that of 8c was confirmed by X-ray crystallography
(see Fig. 2).
For the formation of 1,3-dioxolanes of type 7, an addition of the corresponding
oxirane to 4,4'-dimethoxybenzophenone (5) was proposed. To verify this proposal, a
mixture of 3c and 5 in CH2Cl2 at À608 was treated with BF3 ¥ Et2O. After stirring for
15 min, separation of the products by column chromatography gave 7c in 66% yield,
and 5 was recovered in 23% yield (Scheme 4).
Repetition of the reaction of 1 with 3a c in the presence of SnCl4 at À788 led to 6a
and 6b in low yields. On the other hand, the yields of 4a, 4b, and 8c increased to 52, 25,
and 71%, respectively. By means of TLC analysis, no 1,3-dioxolane could be detected in
these cases (see Table 1).

Helvetica Chimica Acta Vol. 84 (2001)
3323
Scheme 3
2.2. Reactions of 4a and 4b with 2-Methyloxirane (3a). To explain the formation of
the unexpected product 6a, the 1:1 adduct 4a was reacted with 3a at À908 in the
presence of BF3 ¥ Et2O. After chromatographic separation, the 1:2 adduct 6a was
obtained in 11% yield (Scheme 5).
The analogous reaction of 4b with 3a under the conditions mentioned above gave
the 1:1:1 adduct 9 in 4% yield (Scheme 5). The structure of 9 was assigned on the basis
of its 1H- and 13C-NMR, and ESI mass spectra. The 1H-NMR spectrum shows a signal
(dd) at 3.12 ppm for 1H of CH2S, again with the typical value of a geminal coupling
(14.7 Hz) in eight-membered rings.
2.3. Reactions of 1,1,3,3-Tetramethylindane-2-thione (2) with Oxiranes. To a solution
of 2 and 1.1 equiv. BF3 ¥ Et2O in dry CH2Cl2 at 08 under N2, 5 equiv. of 2-methyloxirane
(3a) were added dropwise. The color of the mixture changed from orange to pale pink.

3324
Helvetica Chimica Acta Vol. 84 (2001)
Fig. 2. ORTEP Plot [6] of the molecular structure of 8c (arbitrary numbering of the atoms; 50% probability ellipsoids)
Scheme 4
Scheme 5

Helvetica Chimica Acta Vol. 84 (2001)
3325
After 4 min, the reaction was quenched by addition of H2O. Chromatographic
separation gave two isomeric 1:1 adducts 10a and 11a, as well as ketone 12 in 44, 5, and
29% yields, respectively. The starting material 2 was recovered in only 5% yield (see
Scheme 6 and Table 2). The reaction was repeated at À788, room temperature, and 408.
It is remarkable that 10a was the exclusive product at À788, but, with rising reaction
temperature the yield of its isomer 11a and ketone 12 increased significantly (see
Table 2).
Scheme 6
Table 2. BF3-Catalyzed Reactions of 2 with 3 in CH2Cl2
3
a
R
Temp.
[8]
Reaction time
[min]
Yields [%] of products
10
11
12
2
Me
À 7820
28
54
0
r.t.
40
4
1
1
60
25
45
44
39
5
9
29
24
5
4
3811
28
43
3
b
c
Bu
Ph
0
9
56
24
62
1
31
64
À 60
0
The BF3 ¥ Et2O-catalyzed reaction of 2 with 3b gave similar results. At 08, the ratio
10b/11b amounted to ca. 3 :1 (CC). Due to the extended reaction time, 12 was isolated
in 62% yield.
The corresponding reaction of 2 with 3c led only to a 1:1 adduct 11c at À608 and at
08 in 56 and 24% yield, respectively. In this case, no 12 could be observed; however, a
larger amount of starting material 2 was recovered (see Table 2).
1
The structures of the products were assigned on the basis of H- and 13C-NMR
spectra, elemental analyses, and EI-MS; the structures of compounds 10a, 11a, and 11c
were confirmed by means of X-ray crystallography (Figs. 3 5).
3. Discussion and Conclusion. The results presented show that the asymmetric 2-
alkyl- and 2-phenyloxiranes 3a c, in the presence of a Lewis acid, react with the
nonenolizable thioketones 1 and 2 to yield 1,3-oxathiolanes. The results support
fundamentally the reaction mechanisms depicted in Scheme 1.
The reactions of 1 and 2 with 3c proceeded with high regioselectivity, and so did
those of 1 with 3a and 3b (Tables 1 and 2). However, different results were obtained in
the cases of 2 with 3a and 3b (Table 2). The reaction of 2 with 3a at À788 gave
exclusively 10a, while both isomers 10a and 11a were formed at 08, room temperature

3326
Helvetica Chimica Acta Vol. 84 (2001)
Fig. 3. ORTEP Plot [6] of the molecular structure of 10a, showing both disordered configurations (arbitrary
numbering of the atoms; 50% probability ellipsoids; a) major component (75%); b) minor component (25%))
and 408, i.e., the regioselectivity decreased with increasing temperature. It is worth
mentioning that the ratio 10a/11a is always in favor of 10a, in good agreement with the
mechanisms depicted in Scheme 1. The nucleophilic attack at the oxirane is favored at
the unsubstituted, the sterically less hindered C-atom.
Under the chosen reaction conditions, the aromatic thioketone 1 is more reactive
than the aliphatic thioketone 2. On the other hand, 2 is more stable than 1, as it was
partially recovered by chromatographic separation even if the reaction was performed
at 08 and 408, while not even traces of 1 could be detected after 1 min at À908.
The control experiments showed that 1,3-oxathiolanes decompose easily in the
presence of mineral or Lewis acids. The mechanism of the decomposition under acidic
conditions has been described by Pihlaja [7]. An analogous mechanism is proposed for
the Lewis acid catalysis, whereby the CÀO bond of the Lewis acid-complexed 1,3-

Helvetica Chimica Acta Vol. 84 (2001)
3327
Fig. 4. ORTEP Plot [6] of the molecular structure of 11a, showing both disordered configurations (arbitrary
numbering of the atoms; 50% probability ellipsoids; a) major component (60%); b) minor component (40%))
oxathiolane is preferentially broken (Scheme 7). The more stable the intermediate J is,
the faster is the decomposition to the ketones 5 and 12. Therefore, the reaction of 1 led
to a significantly higher yield of ketone than that of 2, since J in the case of 1 is
stabilized by the delocalization of the positive charge through the p-conjugation of the
4-methoxyphenyl groups.
On the basis of the results of the control experiments shown in Scheme 5, the
formation of 6a and 9 can be explained as follows (Scheme 8,a): the zwitterion K is
formed by the nucleophilic attack of the S-atom of the 1,3-oxathiolane 4 at C(3) of the
complexed oxirane. Then, the cleavage of the CÀS bond of K gives a new zwitterion L.
The following cyclization leads to the 1:2 adduct 6 or the 1:1:1 adduct 9. It is
remarkable that, in the reaction with racemic starting materials 4 and 3a, only the trans-
substituted products were found, i.e., (R)-1,3-oxathiolane 4 does not react with (S)-
oxirane ((S)-3a), but only with the (R)-enantiomer, and vice versa.
For the formation of 6 and 9, another mechanism is also conceivable (Scheme 8,b):
after complexation of the S-atom of 4 with BF3, first the CÀS bond is cleaved, leading
to the zwitterion M. The attack of the S-atom of M at C(3) of the BF3-complexed 3a

3328
Helvetica Chimica Acta Vol. 84 (2001)
Fig. 5. ORTEP Plot [6] of the molecular structure of 11c, showing both disordered configurations (arbitrary
numbering of the atoms; 50% probability ellipsoids; a) major component (80%); b) minor component (20%))
Scheme 7
yields the zwitterion L, which undergoes cyclization to the product. However, in this
mechanism, the first step is not in accordance with that described by Pihlaja [7]. In
addition, the complexation of 1,3-oxathiolanes with BF3 should occur preferentially at
the O-atom according to the HSAB principle. Therefore, the second mechanism can be
discarded.
We thank the analytical units of our institute for spectra and analyses and Mr. J. Tˆdtli for his assistance
with the determination of the crystal structures. Financial support of this work by the Swiss National Science
Foundation and F. Hoffmann-La Roche AG, Basel, is gratefully acknowledged. C. F. thanks the Betty Sassella-
Keller-Legat for financial support.
Experimental Part
1. General. See [8]. IR Spectra in CHCl3, NMR spectra at 300 (1H) and 75.5 MHz (13C) in C6D6, if not
otherwise stated.
2. Synthesis of the Starting Materials. The thioketones used were prepared according to described
procedures: 4,4'-dimethoxythiobenzophenone (1) [9] was extracted by means of a Soxhlet extractor with

Helvetica Chimica Acta Vol. 84 (2001)
3329
Scheme 8
pentane, the extracts were concentrated i.v., and the residue was recrystallized from AcOEt (yield 97%); for
1,1,3,3-tetramethylindane-2-thione (2), see [10].
3. General Procedure for the Reactions of Thioketones 1 and 2 with Oxiranes 3. To the soln. of 1 or 2 (ca.
1 mmol) in dry CH2Cl2 (10 15 ml) under N2, 1.1 equiv. of a Lewis acid (BF3 ¥ Et2O or SnCl4) was added at À908,
À788, 08, r.t., and 408, resp. In general, this led to a more or less pronounced change in the color of the soln. After
stirring the mixture for 15 min at the selected temp., ca. 5 equiv. of oxirane 3 was added dropwise, whereby the
color of the soln. changed rapidly in most cases. Then, the reaction was quenched by addition of H2O, and the
mixture was washed with sat. aq. NaCl soln. (3Â). The combined org. layers were dried (MgSO4) and
evaporated i.v. The products were separated by chromatography (SiO2; hexane/Et2O or hexane/CH2Cl2; CC or
prep. TLC (PLC)).
4. Reactions of 1. 4.1. With 2-Methyloxirane (3a). Reaction of 1 (258mg, 1 mmol) with 3a (290 mg, 5 mmol)
and 1.1 mmol BF3 ¥ Et2O (or SnCl4) at different temperatures (1 min, CC (hexane/Et2O 10 :1)) yielded 2,2-bis(4-
methoxyphenyl)-5-methyl-1,3-oxathiolane (4a), trans-2,2-bis(4-methoxyphenyl)-4,8-dimethyl-1,3,6-dioxathio-
cane (6a), 2,2-bis(4-methoxyphenyl)-4-methyl-1,3-dioxolane (7a), and 4,4'-dimethoxybenzophenone (5) (see
Table 1).
Data of 4a: Colorless oil. IR: 2955w, 2930w, 2900w, 2835w, 1607s, 1580w, 1507s, 1464w, 1440w, 1410w, 1380w,
1300m, 1250s, 1200 (sh), 1174s, 1090m, 1030s, 8 20s. 1H-NMR (CDCl3): 7.53 (d, J ˆ 8.9, 2 arom. H); 7.31 (d, J ˆ
9.0, 2 arom. H); 6.87 (d, J ˆ 8.9, 2 arom. H); 6.79 (d, J ˆ 9.0, 2 arom. H); 4.30 4.19 (m, HÀC(5)); 3.80, 3.75 (2s,
2 MeO); 3.18( dd, J ˆ 9.9, 5.4, 1 HÀC(4)); 2.97 (dd, J ˆ 9.9, 8.9, 1 HÀC(4)); 1.50 (d, J ˆ 6.0, Me). 13C-NMR
(CDCl3): 159.0, 158.9 (2s, 2 arom. C); 137.5, 137.4 (2s, 2 arom. C); 128.6, 127.9 (2d, 4 arom. CH); 113.5, 113.2 (2d,
4 arom. CH); 98.6 (s, C(2)); 78.3 (d, C(5)); 55.3 (q, 2 MeO); 41.4 (t, C(4)); 19.6 (q, Me). CI-MS (NH3): 319 (6),
‡
318(19), 317 (100, [ M ‡ H] ), 243 (31). Anal. calc. for C18H20O3S (316.42): C 68.33, H 6.37, S 10.13; found: C
68.33, H 6.44, S 10.17.
Data of 6a: Colorless crystals. M.p. 106.5 107.48. IR: 2965w, 2925w, 2835w, 1610m, 1585w, 1508s, 1465w,
1440w, 1410w, 1375w, 1334w, 1312w, 1301w, 1245s, 1205 (sh), 1172s, 1128w, 1080m, 1030s, 1010m, 975w, 8 29m.
1H-NMR: 7.80 7.40 (br. s, 4 arom. H); 6.76 (d, J ˆ 8.5, 4 arom. H); 4.02 3.98 (m, HÀC(4), HÀC(8)); 3.29 (s,
2 MeO); 2.73 (dd, J ˆ 14.6, 3.0, 2 H, CH2(5), CH2(7)); 2.46 (dd, J ˆ 14.6, 5.5, 2 H, CH2(5), CH2(7)); 1.00 (d, J ˆ
6.4, 2 Me). 13C-NMR: 159.4 (s, 2 arom. C); 136.1 (s, 2 arom. C); 129.0 (br. d, 4 arom. CH); 113.3 (d, 4 arom.
CH); 102.7 (s, C(2)); 69.8( d, C(4), C(8)); 54.6 (q, 2 MeO); 38.7 (t, C(5), C(7)); 21.6 (q, 2 Me). CI-MS (NH3):
‡
‡
509 (26), 508(32), 507 (100), 375 (15, [ M ‡ H] ), 374 (23, [M ‡ NH4 À H2O] ), 331 (7), 330 (32), 135 (8), 133

3330
Helvetica Chimica Acta Vol. 84 (2001)
‡
(49). ESI-MS (CHCl3/MeOH ‡ NaI): 429 (32, [M ‡ MeOH ‡ Na] ), 258(18), 257 (100). ESI-MS (MeCN
‡
‡
‡
NaI): 414 (19), 413 (62, [M ‡ K] ), 399 (10), 398(24), 397 (100, [ M ‡ Na] ), 265 (21). Anal. calc. for C21H26O4S
(374.50): C 67.35, H 7.00, S 8.56; found: C 67.19, H 6.79, S 8.77.
Crystals of 6a suitable for the X-ray crystal-structure analysis were grown from Et2O/MeOH.
Data of 7a: Colorless oil. IR: 3000w, 2960w, 2930w, 2905w, 2820w, 1610s, 1580w, 1500m, 1460m, 1440w,
1410w, 1380w, 1300m, 1240s, 1200 (sh), 1170s, 1110w, 1090 (sh), 1070s, 1030s, 1010w, 98 5w, 955w, 930w, 910w,
830s. 1H-NMR: 7.64, 7.63 (2d, J ˆ 8.9, 4 arom. H); 6.80, 6.77 (2d, J ˆ 8.9, 4 arom. H); 4.10 4.00 (m, HÀC(4));
3.82 (dd, J ˆ 7.5, 6.3, 1 HÀC(5)); 3.37 (t, J ˆ 7.4, 1 HÀC(5)); 3.30, 3.26 (2s, 2 MeO); 1.07 (d, J ˆ 6.1, Me).
13C-NMR: 159.9 (s, 2 arom. C); 136.5, 136.3 (2s, 2 arom. C); 128.2, 128.0 (2d, 4 arom. CH); 113.8, 113.6 (2d,
4 arom. CH); 110.2 (s, C(2)); 72.8( d, C(4)); 71.4 (t, C(5)); 54.8( q, 2 MeO); 18.7 (q, Me). ESI-MS (CH2Cl2/
‡
‡
MeOH ‡ NaI): 413 (47), 323 (9, [M ‡ Na] ), 301 (13, [M ‡ H] ), 257 (27), 243 (100), 135 (24). Anal. calc. for
C18H20O4 (300.35): C 71.98, H 6.71; found: C 71.97, H 6.57.
4.2. With 2-Butyloxirane (3b). Reaction of 1 (258mg, 1 mmol) with 3b (500 mg, 5 mmol) and 1.1 mmol
BF3 ¥ Et2O (or SnCl4) at À908 or À788 (1 min, CC (hexane/Et2O 10 :1)) yielded 5-butyl-2,2-bis(4-methoxy-
phenyl)-1,3-oxathiolane (4b), trans-4,8-dibutyl-2,2-bis(4-methoxyphenyl)-1,3,6-dioxathiocane (6b), and 5 (see
Table 1).
Data of 4b: Colorless oil. IR: 2990w, 2950m, 2930m, 2860w, 2835w, 1608s, 1584w, 1508s, 1464m, 1440w,
1410w, 1375w, 1304m, 1250s, 1200 (sh), 1174s, 1112w, 1034s, 1010w, 8 8 w5, 8 25m. 1H-NMR (CDCl3): 7.52 (d, J ˆ
8.8, 2 arom. H); 7.29 (d, J ˆ 8.9, 2 arom. H); 6.87 (d, J ˆ 8.8, 2 arom. H); 6.78 (d, J ˆ 8.9, 2 arom. H); 4.12 4.01
(m, HÀC(5)); 3.80, 3.75 (2s, 2 MeO); 3.15 (dd, J ˆ 9.8, 5.5, 1 HÀC(4)); 3.00 (t, J ˆ 9.4, 1 HÀC(4)); 1.96 1.84,
1.78 1.65 (2 m, 2 H of Bu); 1.09 1.25 (m, 4 H of Bu); 0.96 0.91 (t-like, J ꢀ 7.1, Me ) . 13C-NMR (CDCl3): 159.0,
158.9 (2s, 2 arom. C); 137.6, 137.5 (2s, 2 arom. C); 128.5, 127.9 (2d, 4 arom. CH); 113.3, 113.2 (2d, 4 arom. CH);
98.4 (s, C(2)); 82.4 (d, C(5)); 55.3 (q, 2 MeO); 39.9 (t, C(4)); 34.0, 28.6, 22.7 (3t, 3 CH2); 14.0 (q, Me). CI-MS
‡
(NH3): 361 (7), 360 (21), 359 (100, [M ‡ H] ), 244 (10), 243 (76). Anal. calc. for C21H26O3S (358.50): C 70.36, H
7.31, S 8.94; found: C 70.34, H 7.38, S 9.06.
Data of 6b: Colorless oil. IR: 3000m, 2955s, 2935s, 2870m, 2860m, 2840m, 1610s, 1584w, 1507s, 1465m,
1440w, 1410w, 1378w, 1348w, 1314m, 1302m, 1245s, 1205 (sh), 1172s, 1110s, 1078s, 1030s, 1010m, 942w, 8 35s, 8 10w.
1H-NMR: 7.85 7.35 (br. s, 4 arom. H); 6.78( d, J ˆ 8.7, 4 arom. H); 3.97 3.91 (m, HÀC(4), HÀC(8)); 3.29 (s,
2 MeO); 2.95 (dd, J ˆ 14.5, 3.2, 2 H, CH2(5), CH2(7)); 2.55 (dd, J ˆ 14.6, 5.3, 2 H, CH2(5), CH2(7)); 1.74 1.71
(m, 2 H of 2 Bu); 1.30 1.11 (m, 10 H of 2 Bu); 0.79 (t, J ˆ 7.1, 2 Me ) . 13C-NMR: 159.6 (s, 2 arom. C); 136.3 (s,
2 arom. C); 129.3 (br. d, 2 arom. CH); 113.4 (br. d, 2 arom. CH); 102.9 (s, C(2)); 73.7 (d, C(4), C(8)); 54.8 (q,
2 MeO); 37.3 (t, C(5), C(7)); 35.7, 28.0, 23.0 (3t, 6 CH2); 14.2 (q, 2 Me). ESI-MS (MeOH/CH2Cl2 ‡ NaI): 513
‡
‡
(18, [M ‡ MeOH ‡ Na] ), 258(20), 257 (100). ESI-MS (MeCN ‡ NaI): 497 (7, [M ‡ K] ), 481 (100, [M ‡
‡
Na] ), 265 (10). Anal. calc. for C27H38O4S (458.66): C 70.70, H 8.35, S 6.99; found: C 70.65, H 8.02, S 7.03.
4.3. With 2-Phenyloxirane (3c). Reaction of 1 (258mg, 1 mmol) with 3c (600 mg, 5 mmol) and 1.1 mmol
BF3 ¥ Et2O (or SnCl4) at À788 (1 min, CC (hexane/Et2O 10 :1) and CC (C6H6/hexane 4 :1)) yielded 2,2-bis(4-
methoxyphenyl)-4-phenyl-1,3-oxathiolane (8c), 2,2-bis(4-methoxyphenyl)-4-phenyl-1,3-dioxolane (7c), and 5
(see Table 1).
Data of 8c: Colorless crystals. M.p. 136.3 137.38. IR: 3031w, 3009w, 2960w, 2935w, 2910w, 2875w, 2840w,
1609s, 1584m, 1508s, 1465m, 1455m, 1442m, 1414w, 1305m, 1250s, 1205 (sh), 1175s, 1063m, 1035s, 1013m, 978w,
1
940w, 912w, 8 78w, 8 60w, 8 24s, 715 (sh), 700w. H-NMR (CDCl3): 7.50 (d, J ˆ 9.0, 2 arom. H); 7.43 (d, J ˆ 9.0,
2 arom. H); 7.36 7.23 (m, 5 arom. H); 6.86 (d, J ˆ 9.0, 2 arom. H); 6.83 (d, J ˆ 9.0, 2 arom. H); 4.86 (t, J ˆ 6.7,
HÀC(4)); 4.40 (dd, J ˆ 9.4, 6.6, 1 HÀC(5)); 4.08( dd, J ˆ 9.4, 6.91, 1 HÀC(5)); 3.80, 3.78 (2s, MeO). 13C-NMR
(CDCl3): 159.1 (s, 2 arom. C); 139.8, 137.0, 136.8 (3s, 3 arom. C); 128.6, 128.4, 128.4, 128.1, 127.5 (5d, 9 arom.
CH); 113.4, 113.3 (2d, 4 arom. CH); 100.9 (s, C(2)); 76.9 (t, C(5)); 55.8( d, C(4)); 55.3 (2q, 2 MeO). ESI-MS
‡
(CH2Cl2/MeOH): 379 (93, [M ‡ H] ), 275 (29), 259 (100), 243 (34). Anal. calc. for C23H22O3S (378.49): C 72.99,
H 5.86, S 8.47; found: C 72.69, H 5.84, S 8.71.
Crystals of 8c suitable for the X-ray crystal-structure analysis were grown from Et2O/MeOH.
Data of 7c: Colorless oil. IR: 3002w, 2960w, 2938w, 2910w, 2840w, 1610s, 1585w, 1510s, 1465m, 1455w, 1442w,
1415w, 1305m, 1250s, 1205 (sh), 1172s, 1080s, 1035s, 1013m, 955w, 928w, 8 35s, 700w. 1H-NMR: 7.73, 7.69 (2d, J ˆ
8.9, 4 arom. H); 7.31 7.03 (m, 5 arom. H); 6.84, 6.79 (2d, J ˆ 8.9, 4 arom. H); 5.02 (t, J ˆ 7.0, HÀC(4)); 4.08( dd,
J ˆ 7.8, 6.8, 1 HÀC(5)); 3.78( t, J ˆ 7.5, 1 HÀC(5)); 3.32, 3.27 (2s, 2 MeO). 13C-NMR: 159.9 (s, 2 arom. C); 140.0
(s, 1 arom. C); 135.8( s, 2 arom. C); 128.6, 128.2, 128.1, 128.0, 126.8 (5d, 9 arom. CH); 113.8, 113.7 (2d, 4 arom.
CH); 111.0 (s, C(2)); 78.7 (d, C(4)); 72.3 (t, C(5)); 54.7, 54.6 (2q, 2 MeO). ESI-MS (CH2Cl2/MeOH ‡ NaI): 535
‡
(12), 519 (36), 465 (8), 385 (100, [ M ‡ Na] ). Anal. calc. for C23H22O4 (362.43): C 76.22, H 6.12; found: C 76.10,
H 6.12.

Helvetica Chimica Acta Vol. 84 (2001)
3331
4.4. Reaction of 3c with 5. An analogous reaction of 5 (242 mg, 1 mmol) with 3c (600 mg, 5 mmol) in the
presence of 1.1 mmol BF3 ¥ Et2O at À608 (15 min), yielded 211 mg (66%) of 7c, and 49 mg (23%) of 5 were
recovered.
4.5. Reactions of 4a and 4b with 3a. Treatment of 4a (133 mg, 0.42 mmol) with 3a (122 mg, 2.1 mmol) in the
presence of 0.378mmol BF 3 ¥ Et2O at À908 (20 min, CC (hexane/Et2O 10 :1)) yielded 18mg (11%) of 6a.
An analogous reaction of 4b (180 mg, 0.5 mmol) with 3a (145 mg, 2.5 mmol) under the conditions
mentioned above yielded 9 mg (4%) of trans-4-butyl-2,2-bis(4-methoxyphenyl)-8-methyl-1,3,6-dioxathiocane
(9), 98mg (81%) of 5, and 6 mg (3%) of 4b were recovered.
Data of 9: Colorless oil. IR: 3000w, 2960m, 2935m, 2875m, 2860w, 2840w, 1610s, 1585w, 1508s, 1465w, 1442w,
1412w, 1375w, 1315w, 1304w, 1246s, 1200 (sh), 1174s, 1129w, 1102w, 1092w, 1079m, 1034s, 1012m, 974w, 945w,
860w, 8 35m. 1H-NMR: 7.84 7.42 (br. s, 4 arom. H); 6.79 (d, J ˆ 8.8, 4 arom. H); 4.19 4.13, 3.78 3.73 (2m,
HÀC(4), HÀC(8)); 3.29, 3.28 (2s, 2 MeO); 3.12 (dd, J ˆ 14.7, 3.9, 1 H, CH2(5), CH2(7)); 2.61 2.43 (m, 3 H,
CH2(5), CH2(7)); 1.94 1.90 (m, 1 H of Bu); 1.44 1.16 (m, 5 H of Bu); 0.91 (d, J ˆ 6.4, Me); 0.85 0.81 (t-like,
J ꢀ 7.0, Me). 13C-NMR: 159.4 (s, 2 arom. C); 136.6, 135.6 (2s, 2 arom. C); 129.0 (br. d, 4 arom. CH); 113.2 (br. d,
4 arom. CH); 102.7 (s, C(2)); 72.4 (d, C(4)); 71.1 (d, C(8)); 54.6 (q, 2 MeO); 39.0, 37.3 (2t, C(5), C(7)); 35.4, 28.2,
‡
22.9 (3t, 3 CH2); 22.0, 14.1 (2q, 2 Me). ESI-MS (MeCN ‡ NaI): 456 (7), 455 (19, [M ‡ K] ), 441 (12), 440 (26),
‡
439 (100, [M ‡ Na] ).
5. Reactions of 2. 5.1. With 3a. Reaction of 2 (204 mg, 1 mmol) with 3a (290 mg, 5 mmol) and 1.1 mmol
BF3 ¥ Et2O at different temp. (CC (hexane/CH2Cl2 10 :1) and PLC) yielded 1,1,3,3-tetramethyl-5'-methylspiro-
[indane-2,2'-[1,3]oxathiolane] (10a), 1,1,3,3-tetramethyl-4'-methylspiro[indane-2,2'-[1,3]oxathiolane] (11a), and
1,1,3,3-tetramethylindan-2-one (12). In addition, the starting material 2 was partly recovered (see Table 2).
Data of 10a: Colorless crystals. M.p. 77.6 79.08. IR: 3070w, 2985s, 2965s, 2932s, 2900m, 2870m, 1588w,
1480s, 1450s, 1380s, 1364m, 1350w, 1338w, 1314w, 1180w, 1170w, 1143m, 1122w, 1090s, 1050s, 1028w, 1020w, 998m,
970w, 958m, 912w, 900w, 8 50w. 1H-NMR: 7.16 7.04 (m, 4 arom. H); 4.09 4.02 (m, HÀC(5')); 2.43 (dd, J ˆ 10.3,
4.5, 1 HÀC(4')); 2.33 (t, J ˆ 10.2, 1 HÀC(4')); 1.48, 1.41, 1.37, 1.34 (4s, 4 Me); 0.93 (d, J ˆ 5.9, Me). 13C-NMR:
149.3, 148.7 (2s, 2 arom. C); 127.1, 127.0, 122.7, 122.5 (4d, 4 arom. CH); 112.4 (s, C(2)); 80.4 (d, C(5')); 51.8, 51.6
.
‡
(2s, C(1), C(3)); 39.8( t, C(4')); 32.5, 30.2, 24.1, 22.5, 18.6 (5q, 5 Me). EI-MS: 262 (6, M ), 188 (52), 173 (26),
160 (61), 145 (100), 131 (16), 130 (11), 129 (22), 128(23), 127 (11), 117 (21), 115 (20). Anal. calc. for C 16H22OS
(262.42): C 73.23, H 8.45, S 12.22; found: C 72.85, H 8.57, S 11.94.
Crystals of 10a suitable for the X-ray crystal-structure analysis were grown from MeOH/pentane.
Data of 11a: Colorless crystals. M.p. 87.4 89.38. IR: 3070w, 2990m, 2965s, 2930s, 2870s, 1600w, 1588w, 1479s,
1450m, 1378s, 1362m, 1314w, 1262w, 1170w, 1130m, 1092s, 1019s, 1026w, 1006w, 978m, 957m, 914m, 8 70w.
1H-NMR: 7.15 7.05 (m, 4 arom. H); 3.82 3.78 (m, 1 HÀC(5')); 3.30 3.22 (m, 1 HÀC(5'), HÀC(4')); 1.46,
1.43, 1.37, 1.35 (4s, 4 Me); 0.97 (d, J ˆ 6.1, Me). 13C-NMR: 149.0, 148.6 (2s, 2 arom. C); 127.1, 127.0 (2d, 2 arom.
CH); 122.7, 122.5 (2d, 2 arom. CH); 114.0 (s, C(2)); 78.8 (t, C(5')); 52.4, 51.5 (2s, C(1), C(3)); 44.1 (d, C(4'));
.
‡
32.1, 30.7, 23.7, 22.3, 16.5 (5q, 5 Me). EI-MS: 262 (31, M ), 220 (7), 205 (10), 189 (21), 188 (100), 187 (17), 173
(27), 160 (53), 145 (61), 131 (14), 129 (13), 91 (10). Anal. calc. for C16H22OS (262.42): C 73.23, H 8.45, S 12.22;
found: C 73.15, H 8.44, S 12.25.
Crystals of 11a suitable for the X-ray crystal-structure analysis were grown from Et2O/MeOH.
5.2. With 3b. Reaction of 2 (204 mg, 1 mmol) with 3b (500 mg, 5 mmol) and 1.1 mmol BF3 ¥ Et2O at 08 (1 h,
CC (hexane/CH2Cl2 10 :1) and PLC) yielded 1,1,3,3-tetramethyl-5'-butylspiro[indane-2,2'-[1,3]oxathiolane]
(10b), 1,1,3,3-tetramethyl-4'-butylspiro[indane-2,2'-[1,3]oxathiolane] (11b), and 12. In addition, the starting
material 2 was partly recovered (see Table 2).
Data of 10b: Colorless oil. IR: 3060w, 2990s, 2960s, 2930s, 2862s, 1600w, 1585w, 1478s, 1466s, 1455s, 1450s,
1375s, 1362s, 1344w, 1312m, 1250w, 1175w, 1158w, 1139w, 1124w, 1110w, 1100w, 1050s, 1025m, 1005w, 995w, 970m,
955s, 938w, 923w, 900w, 8 68w. 1H-NMR (CDCl3): 7.25 7.14 (m, 4 arom. H); 4.26 4.17 (m, HÀC(5')); 2.95 (dd,
J ˆ 10.3, 4.4, 1 HÀC(4')); 2.70 (t, J ˆ 10.2, 1 HÀC(4')); 1.78 1.30 ( m, 3 CH2); 1.42, 1.41, 1.34, 1.31 (4s, 4 Me);
0.91 0.86 (t-like, J ꢀ 7.0, Me). 13C-NMR (CDCl3): 149.1, 148.5 (2s, 2 arom. C); 126.8, 126.7, 122.4, 122.2 (4d,
4 arom. CH); 111.7 (s, C(2)); 84.8 (d, C(5')); 51.7, 51.5 (2s, C(1), C(3)); 38.2 (t, C(4')); 33.5, 28.4, 22.6 (3t, 3 CH2);
.
‡
32.4, 30.1, 23.9, 22.3, 13.8(5 q, 5 Me). EI-MS: 305 (6), 304 (22, M ), 303 (12), 220 (6), 205 (11), 189 (26), 188
(100), 187 (21), 173 (13), 160 (28), 145 (32), 129 (6), 117 (7), 91 (5). Anal. calc. for C19H28OS (304.50): C 74.95,
H 9.27, S 10.53; found: C 74.63, H 9.39, S 10.32.
Data of 11b: Colorless oil. IR: 3060w, 2985m, 2955s, 2930s, 2860s, 1584w, 1475s, 1465s, 1450 (sh), 1375s,
1360m, 1310w, 1260w, 1170w, 1150w, 1125w, 1078s, 1000w, 965w, 953m, 910m. 1H-NMR (CDCl3): 7.22 7.11 (m,
4 arom. H); 4.25 (dd, J ˆ 8.2, 5.2, 1 HÀC(5')); 3.67 3.50 (m, 1 HÀC(5'), HÀC(4')); 1.75 1.57 (m, 2 H of Bu);
1.45 1.25 (m, 4 H of Bu, 4 Me); 0.96 0.91 (t-like, J ꢀ 7.0, Me). 13C-NMR (CDCl3): 148.5, 148.1 (2s, 2 arom. C);

3332
Helvetica Chimica Acta Vol. 84 (2001)
126.9, 126.8, 122.5, 122.3 (4d, 4 arom. CH); 112.9 (s, C(2)); 77.3 (t, C(5')); 52.1, 51.3 (2s, C(1), C(3)); 50.1 (d,
.
‡
C(4')); 32.3, 31.5, 22.6 (3t, 3 CH2); 31.8, 30.4, 23.3, 22.1, 13.8 (5q, 5 Me). EI-MS: 304 (7, M ), 205 (11), 189 (18),
188 (100), 173 (30), 161 (11), 160 (69), 146 (15), 145 (75), 131 (16), 129 (17), 128 (13), 117 (20), 115 (15), 91
(15). Anal. calc. for C19H28OS (304.50): C 74.95, H 9.27, S 10.53; found: C 74.87, H 9.13, S 10.23.
5.3. With 3c. Reaction of 2 (204 mg, 1 mmol) with 3c (600 mg, 5 mmol) and 1.1 mmol BF3 ¥ Et2O at À608 or
08 (25 min or 45 min, resp., CC (hexane/CH2Cl2 10 :1)) yielded 1,1,3,3-tetramethyl-4'-phenylspiro[indane-2,2'-
[1,3]oxathiolane] (11c). In addition, the starting material 2 was partly recovered (see Table 2).
Data of 11c: Colorless crystals. M.p. 103.5 104.08. IR: 2960w, 2995m, 2962s, 2935m, 2870m, 1600m, 1575w,
1490m, 1478s, 1450s, 1378s, 1362m, 1312w, 1128m, 1075s, 1025w, 995m, 965w, 952m, 915m, 8 60w, 698m. 1H-NMR
(CDCl3): 7.52 (d, J ˆ 7.3, 2 arom. H); 7.40 7.21 (m, 7 arom. H); 4.73 (dd, J ˆ 10.2, 5.9, HÀC(4')); 4.44 (dd, J ˆ
8.9, 5.9, 1 HÀC(5')); 4.06 4.00 (br. t, J ꢀ 10.3, 9.1, 1 HÀC(5')); 1.50, 1.44, 1.40, 1.39 (4s, 4 Me). 13C-NMR
(CDCl3): 148.4, 148.0, 136.2 (3s, 3 arom. C); 128.6, 128.0, 127.9, 127.0, 126.9, 122.5, 122.3 (7d, 9 arom. CH); 113.9
(s, C(2)); 78.8 (t, C(5')); 53.8( d, C(4')); 52.1, 51.7 (2s, C(1), C(3)); 31.9, 30.3, 23.5, 22.4 (4q, 4 Me). EI-MS: 324
.
‡
(12, M ), 220 (33), 205 (16), 188 (21), 173 (16), 160 (49), 145 (86), 136 (100), 135 (58), 104 (85), 91 (45), 77
(18). Anal. calc. for C21H24OS (324.49): C 77.73, H 7.46, S 9.88; found: C 77.59, H 7.41, S 9.99.
Crystals of 11c suitable for the X-ray crystal-structure analysis were grown from THF.
6. X-Ray Crystal-Structure Determination of 6a, 8c, 10a, 11a, and 11c (see Table 3 and Figs. 1 5)2). All
measurements were made on a Rigaku AFC5R diffractometer using graphite-monochromated MoKa radiation
(l ˆ 0.71069 ä) and a 12-kW rotating anode generator. The w/2q scan mode was employed for data collection.
The intensities were corrected for Lorentz and polarization effects, but not for absorption. Data collection and
refinement parameters are given in the Table 3, views of the molecules are shown in Figs. 1 5.
The structures were solved by direct methods using SHELXS97 [11] for 8c or SIR92 [12] for 6a, 10a, 11a,
and 11c, which revealed the positions of all non-H-atoms. For each structure, all non-H-atoms were refined
anisotropically (except for the atoms of the minor disordered conformation of 11c (see below), which were
refined isotropically). All of the H-atoms were fixed in geometrically calculated positions (d(CÀH) ˆ 0.95 ä),
and each was assigned a fixed isotropic displacement parameter with a value equal to 1.2Ueq of its parent C-
atom. Refinement of each structure was carried out on F using full-matrix least-squares procedures, which
minimized the function Sw( j Fo jÀj Fc j )2. A correction for secondary extinction was applied in each case.
Neutral atom scattering factors for non-H atoms were taken from [13a], and the scattering factors for H-
atoms were taken from [14]. Anomalous dispersion effects were included in FC [15]; the values for f ' and f '' were
those of [13b]. The values of the mass attenuation coefficients are those of [13c]. All calculations were
performed using the teXsan crystallographic software package [16].
For 6a, which is racemic, there are two symmetry-independent molecules in the asymmetric unit; however,
there are no significant conformational differences between the molecules, and they both represent the same
stereoisomer in which the two Me substituents in the eight-membered ring lie trans to one another.
The crystals of 8c are enantiomerically pure, and the absolute configuration of the molecule has been
confidently determined independently by the diffraction experiment (absolute structure parameterˆ 0.01(6))
[17]. The configuration at C(4) is (R). The heterocyclic ring has a half-chair conformation twisted on
O(1)ÀC(5), but distorted significantly towards an envelope conformation with C(5) as the envelope flap.
Compounds 10a, 11a, and 11c are all racemic, as dictated by the space-group symmetry. However, each
structure is disordered in that the sites of one enantiomer in the crystal are also partially occupied by the
opposite enantiomer, and vice versa. In the refined model, this manifests itself in the substituted C-atom of the
heterocyclic five-membered ring occupying two disordered positions, above and below the mean ring plane, with
the configuration about this atom in one position being inverted in the alternate position. In 10a and 11a, the
position of the C-atom of the associated Me substituent is not disordered, but is common to both configurations
(Figs. 3 and 4). In 11c, the associated Ph substituent is necessarily disordered, and the two orientations of this
ring interpenetrate so that they occupy approximately the same space in the crystal lattice (Fig. 5). The
disordered sites in each structure are not equally occupied, and the relative site-occupation factors of the
disordered sites are 0.75 :0.25, 0.6 :0.4 and 0.8:0.2 for 10a, 11a, and 11c, respectively.
2
)
Crystallographic data (excluding structure factors) for the structures of 6a, 8c, 10a, 11a, and 11c have been
deposited with the Cambridge Crystallographic Data Centre as supplementary publications No.
CCDC 167151 167155. Copies of the data can be obtained, free of charge, on application to the CCDC,
12 Union Road, Cambridge CB21EZ, UK (fax: ‡44-(0)1223-336033; e-mail: deposit@ccdc.cam.ac.uk).

Table 3. Crystallographic Data of Compounds 6a, 8c, 10a, 11a, and 11c
6a
8c
10a
11a
11c
Crystallized from
Et2O/MeOH
C21H26O4S
374.49
colorless, prism
0.18 Â 0.33 Â 0.43
173(1)
Et2O/MeOH
C23H22O3S
378.48
colorless, prism
0.28 Â 0.33 Â 0.39
173(1)
monoclinic
P21
MeOH/pentane
C16H22OS
262.41
colorless, prism
0.25 Â 0.28 Â 0.480.33
173(1)
Et2O/MeOH
C16H22OS
262.41
colorless, prism
 0.43  0.43
173(1)
monoclinic
P21/c
THF
Empirical formula
Formula weight [g molÀ1
Crystal color, habit
Crystal dimensions [mm]
Temp. [K]
C21H24OS
324.48
colorless, prism
0.43 Â 0.45 Â 0.50
173(1)
monoclinic
P21/c
]
Crystal system
Space group
triclinic
monoclinic
P21/c
≈
P1
Z
4
2
4
4
4
Reflections for cell determination
2q Range for cell determination [8]
Unit-cell parameters a [ä]
b [ä]
25
25
25
35 40
25
27 39
25
24 26
12.447(2)
14.647(3)
11.417(4)
108.64(2)
94.19(2)
85.54(2)
1963.7(9)
1.267
36 40
11.573(3)
5.750(2)
15.225(2)
90
111.29(1)
90
944.0(4)
1.331
35 39
14.635(5)
7.926(3)
16.860(3)
90
110.24(2)
90
1835(1)
1.174
12.841(4)
10.635(4)
11.706(3)
90
117.16(2)
90
1422.3(8)
1.225
0.214
8.659(2)
22.499(3)
8.158(2)
90
112.97(2)
90
1463.4(6)
1.191
0.208
c
[ä]
a [8]
b [8]
g [8]
V [ä3]
Dx [g cmÀ3
]
m(MoKa) [mmÀ1
2q(max) [8]
]
0.187
50
0.192
55
0.179
55
55
55
Total reflections measured
Symmetry-independent reflections
Reflections used [I > 2s(I)]
Parameters refined
6170
5820
4580
470
4990
4328
3814
245
4326
3276
2545
173
3692
3365
2161
173
4684
4206
2968
237
Final R
0.0373
0.0359
1.740
6.4(6) Â 10À7
0.0007
0.20; À0.19
0.0389
0.0375
0.0449
0.0453
0.0544
0.0480
0.0543
0.0500
2.211
wR (w ˆ [s2(Fo) ‡ (0.005Fo)2]À1
)
Goodness-of-fit
1.837
2.311
2.029
Secondary extinction coefficient
Final Dmax/s
D1(max; min) [e äÀ3
6(1) Â 10À7
8(1)Â 10À7
2.2(9) Â 10À7
2.8(7) Â 10À7
0.0004
0.0004
0.0004
0.001
]
0.34; À0.32
0.32; À0.22
0.37; À0.380.49;
À0.46

3334
Helvetica Chimica Acta Vol. 84 (2001)
REFERENCES
[1] P.-C. Tromm, H. Heimgartner, Helv. Chim. Acta 1990, 73, 2287.
[2] M. Blagoev, A. Linden, H. Heimgartner, Helv. Chim. Acta. 1999, 82, 1458.
[3] V. Oremus, A. Linden, H. Heimgartner, Helv. Chim. Acta 1991, 74, 1500.
[4] M. Blagoev, A. Linden, H. Heimgartner, Helv. Chim. Acta 1999, 82, 2316.
[5] M. Blagoev, A. Linden, H. Heimgartner, Helv. Chim. Acta, 2000, 83, 3163.
[6] C. K. Johnson, −ORTEP II. Report ORNL-5138×, Oak Ridge National Laboratory, Oak Ridge, Tennessee,
1976.
[7] K. Pihlaja, J. Am. Chem. Soc. 1972, 94, 3330.
[8] D. Moya Argilagos, R. W. Kunz, A. Linden, H. Heimgartner, Helv. Chim. Acta 1998, 81, 2388.
[9] B. S. Pedersen, S. Scheibye, N. H. Nilsson, S.-O. Lawesson, Bull. Soc. Chim. Belg. 1978, 87, 223.
[10] C. P. Klages, J. Vo˚, Chem. Ber. 1980, 133, 2255; E. Langhals, H. Langhals, Tetrahedron Lett. 1990, 31, 859;
¬
¬
G. Mloston, J. Romanski, A. Linden, H. Heimgartner, Helv. Chim. Acta 1995, 78, 1067.
[11] G. M. Sheldrick, −SHELXS97, Program for the Solution of Crystal Structures×, University of Gˆttingen,
Germany 1997.
[12] A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, M. C. Burla, G. Polidori, M. Camalli, SIR92, J.
Appl. Crystallogr. 1994, 27, 435.
[13] a) E. N. Maslen, A. G. Fox, M. A. O×Keefe, in −International Tables for Crystallography×, Ed. A. J. C.
Wilson, Kluwer Academic Publishers, Dordrecht, 1992 Vol. C, Table 6.1.1.1, p. 477; b) D. C. Creagh, W. J.
McAuley, ibid. Table 4.2.6.8, p. 219; c) D. C. Creagh, J. H. Hubbell, ibid. Table 4.2.4.3, p. 200.
[14] R. F. Stewart, E. R. Davidson, W. T. Simpson, J. Chem. Phys. 1965, 42, 3175.
[15] J. A. Ibers, W. C. Hamilton, Acta Crystallogr. 1964, 17, 78 1.
[16] teXsan: Single Crystal Structure Analysis Software, Version 1.10b, Molecular Structure Corporation, The
Woodlands, Texas, 1999.
[17] H. D. Flack, Acta Crystallogr., Sect. A 1983, 39, 876; G. Bernardinelli, H. D. Flack, Acta Crystallogr., Sect. A
1985, 41, 500.
Received July 16, 2001