Pd-catalyzed asymmetric synthesis of allylic tert-butyl sulfones and sulfides: Kinetic resolution of the allylic substrate by a chiral Pd-complex

Article abstract of DOI:10.1016/S0957-4166(97)00601-0

The acyclic and cyclic allylic tert-butyl sulfones 3, ent-3, 11a, 11b and 15a-c of 89-98% ee were synthesized in 40-92% yield by a Pd-catalyzed reaction of the respective allylic acetates and carbonates rac-1a, rac-1b, rac-10a, rac-10b and rac-14a-c with

Full text of DOI:10.1016/S0957-4166(97)00601-0

Pergamon
Tetrahedron: Asymmetry 9 (1998) 235–248
Pd-catalyzed asymmetric synthesis of allylic tert-butyl sulfones
and sulfides: Kinetic resolution of the allylic substrate by a chiral
Pd-complex
Hans-Joachim Gais,∗ Holger Eichelmann, Nicole Spalthoff, Frank Gerhards, Michael Frank
and Gerhard Raabe
Institut für Organische Chemie der Rheinisch-Westfälischen Technischen Hochschule Aachen, Professor-Pirlet-Straße 1,
52056 Aachen, Germany
Received 27 October 1997; accepted 18 November 1997
Abstract
The acyclic and cyclic allylic tert-butyl sulfones 3, ent-3, 11a, 11b and 15a–c of 89–98% ee were synthesized in
40–92% yield by a Pd-catalyzed reaction of the respective allylic acetates and carbonates rac-1a, rac-1b, rac-10a,
rac-10b and rac-14a–c with LiO2St-Bu in the presence of the chiral ligands 2a, ent-2b and 12. Formation of the
n-butyl sulfones 13a and 13b of 95% ee was observed. Reactions of rac-1a and 1b/ent-1b with LiO2St-Bu in the
presence of 2a and ent-2b, respectively, in THF under heterogeneous conditions were accompanied by a kinetic
resolution of the allylic substrates. The faster reacting allylic substrate and the preferentially formed sulfone had
the same absolute configuration. The allylic tert-butyl sulfide 17 of 92% ee was obtained in 63% yield by the Pd-
catalyzed reaction of rac-1b with Me3SiSt-Bu in the presence of ent-2b. © 1998 Elsevier Science Ltd. All rights
reserved.
1. Introduction
The Pd-catalyzed allylic alkylation1 of aryl sulfinates2–5 provides for an effective route for the
asymmetric synthesis of allylic aryl sulfones. In a continuation of previous studies,3 we were interested
to see whether this method could be extended to the asymmetric synthesis of allylic alkyl sulfones and of
allylic sulfides. Sulfones I and II, bearing a tert-butyl group at the S-atom, are of special interest because
of their potential utilization in the synthesis of chiral nonracemic allylic α-sulfonyl carbanions.6 Herein
we describe the Pd-catalyzed asymmetric synthesis of cyclic and acyclic allylic tert-butyl sulfones as
well as of an allylic tert-butyl sulfide. In addition we report on the observation of a kinetic resolution of
the allylic substrate during the Pd-catalyzed substitution and the determination of its stereochemistry.
∗
Corresponding author.
0957-4166/98/$19.00 © 1998 Elsevier Science Ltd. All rights reserved.
PII: S0957-4166(97)00601-0

236
H.-J. Gais et al. / Tetrahedron: Asymmetry 9 (1998) 235–248
2. Results and discussion
2.1. Acyclic allylic sulfones and kinetic resolution
Lithium tert-butylsulfinate was prepared as a colorless solid by reaction of tert-butyllithium with a
large excess of sulfur dioxide in n-hexane–n-pentane.7 The LiO2St-Bu thus obtained was contaminated
with approximately 4% of lithium tert-butylsulfonate according to NMR and IR spectroscopy. Although
in THF as a solvent the amount of LiO3St-Bu was lower (1–2%), the formation of other unidentified side
products made this solvent less suitable. LiO2St-Bu has a low solubility in anhydrous THF (0.074 M),
thus, Pd-catalyzed reactions in this solvent proceeded under heterogeneous conditions (vide infra).
Treatment of acetate rac-1a with LiO2St-Bu in the presence of Pd2(dba)3·CHCl3
(dba=dibenzylideneacetone) (1.5 mol%) and P,N-ligand 2a8–11 (6.6 mol%) in THF (25°C, 8 days) gave
sulfone 3 with an ee value of 93% (HPLC) in 69% chemical yield (Scheme 1). Similar results were
obtained with carbonate rac-1b as substrate.
Scheme 1.
Sulfone 3 was contaminated by approximately 7% of diene 4 which was formed as a mixture of
diastereomers.12 A chromatographic separation of 3 and 4 on silica gel or aluminum oxide proved not to
be possible because of the instability of 3 under these conditions. However, crystallization of the mixture
of 3 and 4 from ethanol gave pure 3 of ≥99% ee (HPLC) in 40% yield. The use of ent-2b8–11 and ent-
2c8–11 instead of 2a as ligands led to formation of ent-3 of 91% ee (90% ee) in 71% (69%) chemical
yield. Sulfone 3 was shown to have the (S) configuration by X-ray structure analysis13 (Fig. 1).
Fig. 1. Structure of 3 in the crystal. Selected bond distances (Å) and bond angles (deg): S–O 1.442(2), S–t-Bu 1.823(3), S–C
1.840(3), O–S–O 117.3(1), C–S–C 106.0(2)

H.-J. Gais et al. / Tetrahedron: Asymmetry 9 (1998) 235–248
237
Under the heterogeneous conditions employed the reactions of acetate rac-1a and carbonate rac-1b
with LiO2St-Bu (2 equiv.) in THF were rather slow. As a result, their course could be easily followed by
HPLC analysis on a chiral column. This led to the observation that the alkylations of tert-butylsulfinate in
the presence of 2a and ent-2b were accompanied by a kinetic resolution of the racemic substrates rac-1a
and rac-1b. HPLC analysis of the reaction mixture obtained upon treatment of rac-1a with LiO2St-Bu in
the presence of Pd2(dba)3·CHCl3 (1.6 mol%) and ent-2b (6.6 mol%) showed, after approximately 40%
conversion, formation of sulfone ent-3 of 91% ee and acetate 1a of 94% ee (Scheme 2). Upon further
reaction, 1a was converted to ent-3 as well. The ee value of sulfone ent-3, however, did not practically
change. By using 2a as a ligand, opposite results were obtained in the reaction of rac-1a with LiO2St-
Bu under the above conditions. The reaction mixture contained, after approximately 60% conversion,
sulfone 3 of 89% ee and ent-1a of 93% ee. Because of the instability of 3 and ent-1a on silica gel and
aluminum oxide, a chromatographic separation of both compounds was not possible.
Scheme 2.
Treatment of rac-1b and 1b:ent-1b (93:7) (vide infra) with LiO2St-Bu in THF in the presence of
Pd2(dba)3·CHCl3 (9 mol%) and 2a (40 mol%) gave similar results as in the case of rac-1a. As revealed
by the continuous monitoring of the reaction of 1b:ent-1b (93:7) by HPLC analysis, the ee value of 1b
gradually dropped to 0%, and after a reaction time of 50 h ent-1b of 80% ee remained (Fig. 2). We note
that in this experiment, where higher amounts of catalyst and ligand were used (vide supra), the ee value
of sulfone 3 was considerably lower (76–81%).
Fig. 2. Time dependence of the ratios of 1b:ent-1b and 3:ent-3 in the Pd-catalyzed reaction of 1b:ent-1b (93:7) with LiO2St-Bu
in the presence of 2a

238
H.-J. Gais et al. / Tetrahedron: Asymmetry 9 (1998) 235–248
The above described kinetic resolutions are not without precedent. Hayashi et al. reported on the
kinetic resolution of a racemic allylic acetate in the Pd-catalyzed allylic alkylation of a soft C-nucleophile
in the presence of a chiral P,P-ligand.14 However, the stereochemistry of this kinetic resolution was not
fully established. Thus, we decided to determine the absolute configurations of carbonate 1b and acetate
1a as well. The methyl substituted alcohol 5 had been previously synthesized15 by the kinetic resolution
of rac-5 using the Sharpless epoxidation method (Scheme 3).16 Subjecting alcohol rac-6 to this method
by using (+)-L-diisopropyl tartrate gave 6 with an ee value of 86% (HPLC) in 29% yield. The rather low
yield of 6 is due to its extensive decomposition during chromatography on silica gel. Besides 6, epoxide
7 and its epimer were formed, but were not isolated.17
Scheme 3.
A comparison of the chiroptical data of 6 with those of 5 led to the assignment of the (S) configuration
to 6 which was converted to acetate 1a and carbonate 1b, both having an ee value of 86% (HPLC). Thus,
in the Pd-catalyzed substitutions of rac-1b, 1b/ent-1b and rac-1a the faster reacting allylic substrate and
the preferentially formed allylic sulfone have the same absolute configuration. This can be rationalized
on the basis of a simplified version of the mechanism proposed for the Pd-catalyzed allylic alkylation of
soft nucleophiles in the presence of 2a–c and related ligands1,18–21 as follows. The chiral Pd(0)-complex
8 reacts reversibly with ent-1a and 1a under formation of complexes ent-1a·8 and 1a·8, respectively
(Scheme 4). In ent-1a·8 the C-atom, bearing the nucleofuge, is trans to the P-atom and the phenyl
groups are in the exo position. The subsequent preferential ionization of ent-1a·8 leads to complex exo-9
which is in equilibrium with endo-9 (exo:endo=9:1).18 These steps of an enantiomer selective ionization
are followed by a preferential attack of tert-butylsulfinate at the C-atom of exo-9 which is trans to the
P-atom, giving sulfone ent-3. A similar rationalization can be applied to the Pd-catalyzed substitutions
of rac-1a, rac-1b and 1b/ent-1b in the presence of 2a.
Synthesis of 1,3-dialkyl substituted allyl tert-butyl sulfones was studied by first using ent-2b as a
ligand. Treatment of rac-10a with NaO2St-Bu22 in THF in the presence of Pd2(dba)3·CHCl3 and ent-2b
under heterogeneous conditions for 2 days, gave a mixture of sulfone ent-11a and the corresponding
sulfinate ester in a ratio of 94:6 (1H NMR) in 61% yield (Scheme 5). Chromatography afforded pure
sulfone ent-11a in 55% yield. However, ent-11a had an ee value of only 58% according to GC analysis.
A similar low enantioselectivity had been found in the substitution of rac-10a with p-tolylsulfinate in the
presence of ent-2b.3 Because of the low enantioselectivity recorded in the formation of ent-11a in the
presence of ent-2b, substitution of rac-10a and rac-10b was carried out in the presence of P,P-ligand
124 which was expected to provide a higher enantioselectivity. Treatment of rac-10a with LiO2St-Bu
in the presence of Pd2(dba)3·CHCl3 and 12 in a liquid two-phase system of water–CH2Cl2 (Hex4NBr)
for 4 days gave 11a in 51% yield. Sulfone 11a had an ee value of 98% (GC). A similar reaction of rac-
10b in the presence of 12 afforded 11b of 96% ee (GC) in 43% yield. Both reactions were rather slow
and approximately 40% of the allylic substrates were recovered. The (R) configuration was tentatively
assigned to 11a and 11b since a similar reaction of rac-10a and rac-10b with benzenesulfinate gave the
corresponding phenyl sulfones, having the (R) configuration.4
The inadvertent treatment of rac-1a with a 1:1 mixture of LiO2St-Bu and lithium n-butylsulfinate7 in
water–CH2Cl2 (Hex4NBr) in the presence of Pd2(dba)3·CHCl3 and 12 led to isolation of a 47:53 mixture
of 11a (96% ee) and the n-butyl sulfone 13a in 46% yield (Scheme 6). Sulfone 13a had an ee value of

H.-J. Gais et al. / Tetrahedron: Asymmetry 9 (1998) 235–248
239
Scheme 4.
Scheme 5.
95% (GC). A similar reaction of rac-10b with LiO2St-Bu:LiO2Sn-Bu gave a 45:55 mixture of 11b (96%
ee) and 13b of 95% ee in 83% yield. These results suggest that asymmetric synthesis of allylic n-alkyl
sulfones by using lithium n-alkyl sulfinates7 should be feasible as well.
Scheme 6.
2.2. Cyclic allylic sulfones
Because of the highly enantioselective synthesis of cyclic allylic phenyl sulfones using 12,4 we chose
this ligand for the synthesis of cyclic allylic tert-butyl sulfones (Scheme 7). Treatment of carbonates rac-
14a–c with LiO2St-Bu in water–CH2Cl2 (Hex4NBr) in the presence of Pd2(dba)3·CHCl3 (1.5 mol%)
and 12 (4.5 mol%) for 24 h gave sulfones 15a–c in 76%, 92% and 89% yield, respectively, with ee values
of 89%, 90% and 93% (GC, 1H NMR), respectively. Reactions of the cyclic carbonates rac-14a–c with
LiO2St-Bu in the presence of 12 were faster than those of the acylic acetates rac-10a,b. The absolute
configuration of 15a–c was tentatively assigned as (S) on the premise that Pd-catalyzed substitution

240
H.-J. Gais et al. / Tetrahedron: Asymmetry 9 (1998) 235–248
–
of rac-14a–c with RSO2 in the presence of 12 proceed with the same sense of asymmetric induction
irrespective of the nature of the group R of the sulfinate.
Scheme 7.
2.3. Acyclic allylic sulfides
Since allylic sulfides can be selectively oxidized to the corresponding sulfones, it was of interest to see
whether the asymmetric synthesis of allylic tert-butyl sulfides could be accomplished by a Pd-catalyzed
allylic alkylation. Because of the known ability of trimethylsilyl sulfides to enter into a Pd-catalyzed
allylic substitutions in the presence of achiral ligands,23,24 we studied the reaction of rac-1b with sulfide
1625 in the presence of 2a and ent-2b (Scheme 8). Treatment of rac-1b with 16 in the presence of
Pd2(dba)3·CHCl3 (5 mol%) and 2a (13 mol%) in CH2Cl2 gave sulfide 17 with an ee value of 92% in
62% yield. A similar reaction of rac-1b in the presence of ent-2b led to the isolation of sulfide ent-17 with
an ee value of 93% (HPLC) in 63% yield. The (R) configuration of 17 (85% ee) was determined by its
oxidation to sulfone ent-3 (69% ee). The nucleophile in the substitution of rac-1b was presumably tert-
butylthiolate formed by a desilylation of 16 by ethoxide, which in turn originated from the decomposition
of the nucleofuge.26
Scheme 8.
3. Conclusion
The Pd-catalyzed asymmetric allylic alkylation of tert-butylsulfinate in the presence of P,P-ligand 12
proceeds with high enantioselectivity and provides for an easy access to cyclic and acyclic allylic tert-
butyl sulfones. An enantiomer differentiating ionization of the allylic substrate by the chiral Pd–P,N-
ligand complexes has been experimentally verified in the reactions of rac-1a and 1b/ent-1b in the
presence of ligands 2a and ent-2b. In accordance with the currently proposed mechanism of the Pd-
catalyzed allylic alkylation, the faster reacting substrate and the preferentially formed product have the
same configuration. The Pd-catalyzed allylic alkylation of S-nucleophiles in the presence of 2a, ent-2b
and 12 proceeds with the same sense and with a similar degree of asymmetric induction as with C-
and N-nucleophiles. Allylic sulfides can perhaps be obtained as well with high enantioselectivity by this
method. We note, however, that reaction of rac-1b with sulfide 16 required considerably larger amounts
of catalyst and ligand as compared to those with sulfinates.

H.-J. Gais et al. / Tetrahedron: Asymmetry 9 (1998) 235–248
241
4. Experimental section
All reactions were carried out in an atmosphere of argon with Schlenk and syringe techniques.
Suspensions of LiO2St-Bu and NaO2St-Bu in THF were prepared by ultrasonication. THF was distilled
under argon from potassium benzophenone ketyl. n-Pentane was distilled under argon from sodium
benzophenone ketyl in the presence of diglyme (10% v/v). Water was deoxygenated under argon by the
freeze–thaw technique. CH2Cl2 was distilled under argon. TLC was performed on E. Merck plates coated
with silica gel 60 F254 (0.2 mm). Chromatography was performed with E. Merck silica gel 60 (230–400
1
mesh) and silica gel 60 (70–230 mesh). Melting points are uncorrected. H NMR chemical shifts are
reported in ppm relative to Me4Si: δ 0.00 as the internal standard. Coupling constants (J) are given in
Hz. 13C NMR chemical shifts are reported in ppm relative to Me4Si: δ 0.00 as the internal standard. Peaks
in the 13C NMR spectra are denoted as ‘u’ for carbons with zero or two attached protons or as ‘d’ for
carbons with one or three attached protons, as determined from the APT pulse sequence. Determination
of enantiomer composition by capillary GC analysis was performed with a 2,3-dipentyl-6-O-methyl-γ-
cyclodextrin column (25 m×0.25 mm, 0.25 µm) (Lipodex-γ) and a permethyl-β-cyclodextrin column (25
m×0.25 mm, 0.25 µm) (Lipodex-E). HPLC was done with a Baker Chiracel OD-H column. Retention
times (tR) are given in min.
4.1. Lithium tert-butylsulfinate
To a solution of SO2 (150 mL, 3.45 mol) in n-hexane (300 mL) was added, within 3 h at −70°C with
a double-ended needle, a solution of tert-BuLi in n-pentane (300 mL, 1.6 M, 0.48 mol). After stirring
the yellow–brown suspension at this temperature for 1 h, it was allowed to warm to room temperature
over 24 h. A stream of dry argon was passed through the flask to remove last traces of SO2. The solvents
were removed in vacuum under argon and stirring. Drying of the remaining solid for 3 days under high
vacuum gave LiO2St-Bu (5.48 g, 90%) as a colorless solid which contained 4% of LiO3St-Bu: 1H NMR
(300 MHz, D2O) δ 0.83 (s, 9H); 13C NMR (75.5 MHz, D2O) δ 23.33 (d), 57.02 (u); IR (KBr) (in part)
ν 1005 (s). LiO3St-Bu: 1H NMR (300 MHz, D2O) δ 1.16 (s, 9H); 13C NMR (75.5 MHz, D2O) δ 27.02
(d), 57.99 (u); IR (KBr) (in part) ν 1180 (s) cm−1
.
4.2. (−)-(S,E)-1,3-Diphenyl-3-(tert-butylsulfonyl)prop-1-ene 3
To a solution of Pd2(dba)3·CHCl3 (155 mg, 0.15 mmol) in THF (5 mL) was added 2a (268 mg, 0.66
mmol) at room temperature. After stirring the mixture for 15 min, a solution of rac-1a (2.524 g, 10 mmol)
in THF (2 mL) was added. Stirring was continued for 15 min and a suspension of LiO2St-Bu (1.282 g,
20 mmol) in THF (3 mL) was added. After stirring the mixture for 8 days at room temperature, brine
(10 mL) was added and the mixture was extracted with THF. The organic phase was dried (MgSO4) and
concentrated under vacuum. The residue contained 2.374 g of a mixture of 3 and 4 in a ratio of 12:1
(HPLC), corresponding to a 69% chemical yield of 3; 93% ee (HPLC). Recrystallization of the crude
22
material from EtOH gave 3 (1.006 g, 40%): ≥99% ee (HPLC); mp 160°C; [α]D −25.2 (c 0.17, EtOH);
1H NMR (300 MHz, CDCl3) δ 1.36 (s, 9H), 5.07 (dd, J=6.4, J=2.0, 1H), 6.64 (dd, J=16.1, J=2.0, 1H),
6.70 (dd, J=16.1, J=6.4, 1H), 7.23–7.43 (m, 8H), 7.52–7.57 (m, 2H); 13C NMR (75.5 MHz, CDCl3) δ
24.60 (d), 62.65 (u), 68.88 (d), 122.53 (d), 126.76 (d), 128.43 (d), 128.66 (d), 128.89 (d), 128.92 (d),
129.68 (d), 133.57 (u), 135.87 (u), 136.32 (d); MS (EI, 70 eV) m/z (rel. intensity) 314 (M+, 0.5), 209 (5),
194 (21), 193 (100), 178 (17), 165 (7), 115 (73), 91 (22), 65 (6), 57 (34); IR (KBr) ν 3084 (w), 3062 (w),
3043 (w), 3028 (w), 2992 (m), 2976 (m), 1494 (m), 1476 (m), 1457 (m), 1448 (m), 1279 (s), 1210 (m),

242
H.-J. Gais et al. / Tetrahedron: Asymmetry 9 (1998) 235–248
1188 (m), 1108 (s), 1067 (m), 1029 (m), 979 (m), 749 (s), 718 (m), 698 (s), 676 (s) cm−1. Anal. Calcd for
C19H22O2S: C, 72.58; H, 7.06. Found C, 72.57; H, 7.05. From the mother liquor impure 4 was isolated
by chromatography as a mixture of diastereomers. Data for 4: 1H NMR (300 MHz, CDCl3) δ 3.89 (m,
2H), 6.19 (d, J=15.8, 1H), 6.31 (ddd, J=15.8, J=5.4, J=2.4, 1H), 6.39 (d, J=15.8, 1H), 6.54 (ddd, J=15.8,
J=5.4, J=2.4, 1H), 7.05–7.35 (m, 20H); 13C NMR (75.5 MHz, CDCl3) δ 55.20 (d), 55.31 (d), 126.12 (d),
126.16 (d), 126.24 (d), 126.50 (d), 127.01 (d), 127.14 (d), 128.18 (d), 128.33 (d), 128.37 (d), 128.38 (d),
128.43 (d), 128.62 (d), 131.12 (d), 131.36 (d), 131.90 (d), 132.15 (d), 137.49 (u), 137.53 (u), 142.39 (u),
142.63 (u); GC–MS (CI, MeOH, in part) m/z (rel. intensity) 385 (M++1, 2), 309 (13), 283 (5), 231 (9),
205 (18), 194 (16), 193 (100), 167 (24).
4.3. (+)-(R,E)-1,3-Diphenyl-3-(tert-butylsulfonyl)prop-1-ene ent-3
Following the procedure described for the synthesis of 3, Pd2(dba)3·CHCl3 (7.8 mg, 8 µmol), ent-2b
(12.3 mg, 33 µmol) or ent-2c (12.8 mg, 33 µmol), rac-1a (126 mg, 0.5 mmol) and LiO2St-Bu (128 mg,
1 mmol) in THF (1 mL) gave an oil which contained 127 mg (110 mg) of a mixture of ent-3 and 4 in
a ratio of 9:1 (11:1) (HPLC), corresponding to a 71% (63%) chemical yield of ent-3; 91% ee (90% ee)
(HPLC).
4.4. Kinetic resolution of rac-1a and 1b:ent-1b (93:7)
Determination of conversion, product formation and enantiomer ratios: HPLC; chiral column;
Baker Chiracel OD-H; flow rate: 0.5 mL/min; solvent: n-hexane:i-PrOH, 9:1; detection: UV 254
nm; tR(3)=23.75, tR(ent-3)=25.24, tR(ent-1b)=23.75, tR(1b)=25.24, tR(ent-1a)=12.02, tR(1a)=12.90,
tR(4)=8.72 and 9.28. Peak assignment was made by coinjection with authentic samples.
rac-1a and ent-2b: Following the procedure described for the synthesis of 3, Pd2(dba)3·CHCl3 (7.8
mg, 8 µmol), ent-2b (13.4 mg, 33 µmol), rac-1a (126 mg, 0.5 mmol) and LiO2St-Bu (128 mg, 1 mmol)
in THF (1 mL) gave, after 2 days at room temperature, a mixture which contained ent-3 of 91% ee and
1a of 94% ee in a ratio of 60:40. The ratio of 3 to 4 was 2:1.
rac-1a and 2a: Following the procedure described for the synthesis of 3, Pd2(dba)3·CHCl3 (7.8 mg, 8
µmol), 2a (12.3 mg, 33 µmol), rac-1a (126 mg, 0.5 mmol) and LiO2St-Bu (128 mg, 1 mmol) in THF (1
mL) gave, after 2 days at room temperature, a mixture which contained 3 of 89% ee and ent-1a of 93%
ee in a ratio of 40:60. The ratio of ent-3 to 4 was 26:1.
1b:ent-1b (93:7) and 2a: Following the procedure described for the synthesis of 3, Pd2(dba)3·CHCl3
(16.8 mg, 0.016 mmol), 2a (28.6 mg, 0.070 mmol), 1b (56.7 mg, 0.172 mmol) (86% ee) and LiO2St-Bu
(73 mg, 0.561 mmol) were combined in THF (10 mL), and the mixture was stirred at room temperature.
During the course of the reaction aliquots (0.05 mL) were withdrawn and analyzed by HPLC.
4.5. (−)-(S,E)-1,3-Diphenyl-prop-2-en-1-ol 6
To a solution of rac-6 (3.862 g, 18.4 mmol) in CH2Cl2 (60 mL) were added (+)-L-diisopropyltartrate
(0.58 mL, 2.76 mmol) and activated molecular sieve (20 g, 3 Å). The suspension was cooled to −20°C
and Ti(O–iPr)4 (523 mg, 1.84 mmol) was added. After stirring the mixture for 30 min, it was treated at
−20°C with a solution of t-BuOOH (4.2 mL, 3 M, 12.87 mmol) in isooctane. Stirring of the mixture was
continued for 39 h at −20°C, and an aqueous solution (60 mL) of FeSO4 (5.76 g) and citric acid (2.04
g) was added. After stirring the mixture for 30 min at room temperature, it was extracted with CH2Cl2.
The organic phase was stirred vigorously with an aqueous solution of NaOH (18.5 g) and NaCl (3.1 g),

H.-J. Gais et al. / Tetrahedron: Asymmetry 9 (1998) 235–248
243
washed with brine, dried (Na2SO4), and concentrated under vacuum. Chromatography (n-hexane:EtOAc,
4:1) of the residue gave 2.33 g of a mixture of 6, 7 and epi-7 in a ratio of 42:48:9 (1H NMR). The
mixture was dissolved in ether:water (1:1, 50 mL) and NaOH was added until a pH value of 10 was
reached. After stirring the mixture for 7 days at room temperature, the ratio of the three compounds had
changed to 70:29:1 (GC). The mixture was extracted with ether. The organic phase was dried (MgSO4)
and concentrated under vacuum. Purification of the residue by chromatography (n-hexane:EtOAc, 10:1)
gave 6 (560 mg, 29%) as a colorless oil: 86% ee [HPLC: n-hexane:i-PrOH, 9:1, tR(6)=34.98, tR(ent-
20
6)=45.57]; [α]D −23.7 (c 0.67, MeOH). The NMR spectroscopic data of compound 6, as obtained
above, were identical with those of rac-6.
4.6. Ethyl (−)-(S,E)-1,3-diphenyl-prop-2-enyl carbonate 1b
To a solution of 6 (442 mg, 2.10 mmol) in THF (10 mL) were added pyridine (0.75 mL) and 4-
dimethylaminopyridine (5 mg). The solution was cooled to 0°C and ClCOOEt (0.70 mL, 7.4 mmol)
was added dropwise with stirring. After stirring the mixture for 12 h, brine was added and the mixture
was extracted with ether. The organic phase was successively washed with 2 N HCl and brine and dried
(MgSO4). Concentration of the organic phase and drying of the residue under vacuum gave 1b (530 mg,
22
90%) as a colorless oil: 86% ee (HPLC); [α]D −1.8 (c 0.27, MeOH). Anal. Calcd for C18H18O3: C,
76.57; H, 6.43. Found: C, 76.62; H, 6.40. The NMR spectroscopic data of the thus obtained 1b were
identical with those of rac-1b.
4.7. (+)-(S,E)-4-(tert-Butylsulfonyl)-pent-2-ene ent-11a
To a solution of Pd2(dba)3·CHCl3 (403 mg, 0.39 mmol) and ent-2b (640 mg, 1.72 mmol) in THF (50
mL) was added a solution of rac-10a (2.00 g, 15.6 mmol) in THF (2 mL). After stirring the mixture for
15 min, a suspension of NaO2St-Bu (4.50 g, 31.2 mmol) in THF (60 mL) was added at room temperature.
After stirring the suspension for 2 days at room temperature, brine was added and stirring was continued
for 1 h. The organic phase was washed with brine and the aqueous phase was extracted with CHCl3.
The combined organic phases were dried (MgSO4) and concentrated under vacuum to give 1.72 g of a
mixture of ent-11a and the corresponding sulfinate ester in a ratio of 94:6 (GC) as a viscous, yellow oil.
Chromatography (EtOAc:n-hexane, 1:4) of the oil afforded ent-11a (1.62 g, 55%) as a colorless oil: 58%
ee [GC, Lipodex-E, tR (11a)=33.3, tR (ent-11a)=34.0]; [α]D22 +4.3 (c 1.30, EtOH); 1H NMR (300 MHz,
CDCl3) δ 1.43 (s, 9H), 1.48 (d, J=7.1, 3H), 1.75 (dd, J=6.4, J=1.3, 3H), 3.90 (dq, J=9.1, J=7.1, 1H),
5.58 (ddq, J=15.4, J=9.1, J=1.7, 1H), 5.75 (dq, J=15.8, J=6.4, 1H); 13C NMR (75 MHz, CDCl3) δ 14.8
(d), 17.9 (d), 24.49 (d), 58.13 (d), 61.35 (u), 127.49 (d), 130.66 (d); MS (EI, 70 eV) m/z (rel. intensity)
190 (M+, 2), 162 (5), 150 (1), 135 (2), 125 (7), 124 (7), 123 (100), 69 (6), 57 (5); IR (neat) ν 2980 (m),
2940 (m), 1450 (m), 1285 (s), 1115 (s), 1015 (m), 975 (m), 720 (m), 650 (m) cm−1. Anal. Calcd for
C9H18O2S: C, 56.80; H, 9.53. Found: C, 56.76; H, 9.79.
4.8. (−)-(R,E)-4-(tert-Butylsulfonyl)-pent-2-ene 11a
To a solution of Pd2(dba)3·CHCl3 (15.5 mg, 0.015 mmol) and 12 (31.4 mg, 0.045 mmol) in CH2Cl2
(5 mL) was added a solution of rac-10a (128 mg, 1.0 mmol) in CH2Cl2 (1 mL) at room temperature.
The mixture was stirred for 15 min, cooled to 0°C and a suspension of LiO2St-Bu (256 mg, 2.0 mmol)
and Hex4NBr (21 mg) in CH2Cl2 (10 mL) as well as water (3 mL) were added rapidly. After stirring
the suspension for 4 days at room temperature, brine was added and stirring was continued for 1 h.

244
H.-J. Gais et al. / Tetrahedron: Asymmetry 9 (1998) 235–248
The organic phase was washed with brine, and the aqueous phase was extracted with CH2Cl2. The
combined organic phases were dried (MgSO4) and concentrated in vacuum. Purification of the residue
by chromatography (EtOAc:NEt3:n-hexane, 12.5:1:77.5) gave 11a (98 mg, 51%) as a colorless oil: 98%
22
ee (GC, Lipodex-E); [α]D −11.2 (c 1.00, EtOH).
4.9. (−)-(R,E)-5-(tert-Butylsulfonyl)-hept-3-ene 11b
Following the procedure described for the synthesis of 11a, Pd2(dba)3·CHCl3 (15.5 mg, 0.015 mmol),
12 (31.4 mg, 0.045 mmol) in CH2Cl2 (5 mL), rac-10b (156 mg, 1.0 mmol) in CH2Cl2 (1 mL), LiO2St-Bu
(256 mg, 2.0 mmol) and Hex4NBr (21 mg) in CH2Cl2 (10 mL) as well as water (3 mL) gave 11b (95
22
mg, 43%) as a colourless oil: 96% ee [GC, Lipodex-E, tR (11b)=30.8, tR (ent-11b)=31.1]; [α]D −31.4
1
(c 1.00, EtOH); H NMR (300 MHz, CDCl3) δ 0.94 (t, J=7.4, 3H), 1.03 (t, J=7.4, 3H), 1.42 (s, 9H),
1.68 (m, 1H), 2.18 (m, 3H), 3.55 (dt, J=10.1, J=3.3, 1H), 5.45 (ddt, J=15.6, J=9.9, J=1.6, 1H), 5.75 (dt,
J=15.6, J=6.3, 1H); 13C NMR (75.5 MHz, CDCl3) δ 11.35 (d), 13.58 (d), 20.97 (u), 25.10 (d), 26.13 (u),
62.20 (u), 65.34 (d), 124.46 (d), 139.48 (d); MS (EI, 70 eV) m/z (rel. intensity) 219 (M+, 1), 162 (5), 125
(5), 124 (5), 123 (100), 69 (6), 57 (5); IR (neat) ν 2980 (s), 2940 (s), 1460 (m), 1280 (s), 1115 (s), 1015
(m), 975 (m), 800 (w), 720 (m), 660 (m) cm−1. Anal. Calcd for C11H22O2S: C, 60.51; H, 10.16. Found:
C, 60.62; H, 10.48.
4.10. (R,E)-4-(n-Butylsulfonyl)-pent-2-ene 13a and 11a
To a solution of Pd2(dba)3·CHCl3 (15.5 mg, 0.015 mmol) and 12 (31.4 mg, 0.045 mmol) in CH2Cl2
(5 mL) was added a solution of rac-10a (128 mg, 1.0 mmol) in CH2Cl2 (1 mL) at room temperature.
The mixture was stirred for 15 min, cooled to 0°C, and a suspension of LiO2St-Bu (128 mg, 1.0 mmol),
LiO2Sn-Bu (128 mg, 1.0 mmol) and Hex4NBr (21 mg) in CH2Cl2 (10 mL) as well as water (3 mL)
were added rapidly. After stirring the suspension for 48 h at room temperature, brine was added and
stirring was continued for 1 h. The organic phase was washed with brine and the aqueous phase was
extracted with CH2Cl2. The combined organic phases were dried (MgSO4) and concentrated in vacuum.
Purification of the residue by chromatography (EtOAc:NEt3:n-hexane, 12.5:1:76.5) gave 87 mg (46%)
of a mixture of 11a (96% ee) (GC, Lipodex-E) and 13a (95% ee) (GC, Lipodex-E, tR(13a)=37.4, tR(ent-
13a)=37.7) in a ratio of 47:53 (GC, 1H NMR) as a colorless oil. 13a: 1H NMR (300 MHz, CDCl3) δ 0.95
(t, J=7.1, 3H), 1.47 (d, J=7.1, 3H), 1.78 (dd, J=6.3, J=1.6, 3H), 1.82 (m, 4H), 2.92 (t, J=8.2, 2H), 3.59
(dq, J=7.7, J=7.7, 1H), 5.53 (ddq, J=15.4, J=8.5, J=1.3, 1H), 5.83 (dq, J=15.4, J=6.3, 1H); 13C NMR
(75 MHz, CDCl3) δ 12.57 (d), 13.58 (d), 18.17 (d), 23.37 (u), 21.86 (u), 49.06 (u), 61.12 (d), 130.64 (d),
132.98 (d); GC–MS (EI, 70 eV) m/z (rel. intensity) 163 (6), 125 (11), 124 (11), 123 (66), 105 (17), 89
(40), 69 (91), 61 (10), 53 (17), 43 (100), 42 (13), 41 (73), 39 (31), 32 (13).
4.11. (R,E)-5-(n-Butylsulfonyl)-hept-3-ene 13b and 11b
Following the procedure described for the synthesis of 13a, Pd2(dba)3·CHCl3 (77.5 mg, 0.075 mmol),
15 (157 mg, 0.274 mmol) in CH2Cl2 (20 mL), rac-10b (750 mg, 5.0 mmol) in CH2Cl2 (1 mL), LiO2St-Bu
(1.28 g, 5 mmol), LiO2Sn-Bu (1.28 g, 5 mmol), and Hex4NBr (21 mg) in CH2Cl2 (20 mL) and water (10
mL) gave 910 mg (83%) of a mixture 11b (96% ee) (GC, Lipodex-E) and 13b (95% ee) (GC, Lipodex-E,
1
tR(13b)=35.5, tR(ent-13b)=35.8) in a ratio of 45:55 (1H NMR) as a colorless oil. 13b: H NMR (300
MHz, CDCl3) δ 0.94 (t, J=7.4, 3H) 0.98 (t, J=7.4, 3H), 1.03 (t, J=7.4, 3H), 1.45 (m, 2H), 1.80 (m, 3H),
2.15 (m, 3H), 2.94 (m, 2H), 3.32 (dt, J=15.4, J=10.0, J=3.3, 1H), 5.36 (ddt, J=15.4, J=9.7, J=1.7, 1H),

H.-J. Gais et al. / Tetrahedron: Asymmetry 9 (1998) 235–248
245
5.86 (dq, J=15.5, J=6.2, 1H); 13C NMR (75 MHz, CDCl3) δ 11.13 (d), 13.06 (d), 13.57 (d), 19.95 (u),
21.86 (u), 23.48 (u), 25.74 (u), 49.06 (u), 67.76 (d), 121.98 (d), 141.51 (d); GC–MS (EI, 70 eV) m/z (rel.
intensity) 217 (M+, 1), 123 (100), 97 (20), 81 (5), 65 (1), 55 (9), 53 (4), 41 (5), 39 (15).
4.12. (−)-(S)-3-(tert-Butylsulfonyl)cyclopent-1-ene 15a
A mixture of rac-14a (0.13 g, 0.93 mmol), Pd2(dba)3·CHCl3 (15 mg, 14 µmol) and 12 (31 mg, 45
µmol) in CH2Cl2 (3 mL) was stirred for 30 min at room temperature. The yellow solution was cooled
to 0°C and a cold (0°C) suspension of LiO2St-Bu (256 mg, 2 mmol) and Hex4NBr (24 mg, 55.2 µmol)
in CH2Cl2 (3 mL) was added. Subsequently, water (3 mL) was added quickly to the mixture. After
stirring the reaction mixture for 1 day at room temperature, brine (10 mL) was added and the mixture
was stirred for 1 h. The aqueous phase was extracted with CH2Cl2, and the combined organic phases
were concentrated in vacuum. Purification of the residue by chromatography (n-hexane:EtOAc:NEt3,
13:76:1) gave 15a (133 mg, 76%) as a colorless solid: 89% ee [GC, Lipodex-E: tR (15a)=33.62, tR (ent-
1
15a)=33.75; H NMR (300 MHz, CDCl3, 30 mol% Eu(hfc)3): δ (t-Bu) (15a) 2.47, δ (t-Bu) (ent-15a)
22
2.50]; mp 58°C; [α]D −192.6 (c 1.02, CH2Cl2); 1H NMR (300 MHz, CDCl3) δ 1.44 (s, 9H), 2.16–2.75
(m, 4H), 4.40 (m, 1H), 5.78–5.83 (ddt, J=5.7, J=2.3, J=2.0, 1H), 6.19–6.23 (ddt, J=5.7, J=2.0, J=1.3,
1H); 13C NMR (75 MHz, CDCl3) δ 24.16 (d), 25.99 (u), 32.69 (u), 60.15 (u), 64.73 (d), 123.85 (d),
139.18 (d); MS (EI, 70 eV) m/z (rel. intensity) 67 (M+−SO2t-Bu, 100), 66 (20), 57 (78); IR (KBr) ν
3327 (w), 3085 (w), 3057 (m), 2973 (s), 2933 (s), 2854 (m), 1627 (m), 1577 (w), 1479 (s), 1465 (s), 1398
(m), 1372 (m), 1352 (m), 1278 (s), 1196 (m), 1107 (s), 1014 (s), 988 (m), 942 (w), 917 (s), 805 (m), 742
(s), 671 (s), 616 (s) cm−1. Anal. Calcd for C9H16O2S: C, 57.41; H, 8.57. Found: C, 57.36; H, 8.76.
4.13. (−)-(S)-3-(tert-Butylsulfonyl)-cyclohex-1-ene 15b
Following the procedure described for the synthesis of 15a, rac-14b (0.80 g, 5.1 mmol),
Pd2(dba)3·CHCl3 (75 mg, 72.4 µmol), 12 (155 mg, 0.22 mmol), LiO2St-Bu (1.3 g, 10 mmol)
and Hex4NBr (125 mg, 0.3 mmol) in CH2Cl2 (60 mL) and water (30 mL) gave, after 1 h at 0°C and 2
h at room temperature, 15b (0.97 g, 92%) as a colorless solid: 90% ee [1H NMR (300 MHz, CDCl3, 30
22
mol% Eu(hfc)3): δ (t-Bu) (15b) 2.08, δ (t-Bu) (ent-15b) 2.12]; mp 55°C; [α]D −170 (c 0.99, CH2Cl2);
1H NMR (300 MHz, CDCl3) δ 1.45 (s, 9H), 1.58–1.70 (m, 1H), 1.94–2.28 (m, 5H), 3.93 (m, 1H), 5.84
(ddt, J=10.4, J=4.0, J=2.0, 1H), 6.12 (ddt, J=10.4, J=4.0, J=2.3, 1H); 13C NMR (75 MHz, CDCl3) δ
20.14 (u), 23.90 (u), 24.28 (d), 24.37 (u), 55.23 (d), 61.27 (u), 119.75 (d), 134.64 (d); MS (EI, 70 eV)
m/z (rel. intensity) 81 (M+−SO2t-Bu, 34), 80 (29), 79 (23), 77 (10), 57 (100), 53 (11); IR (KBr) ν 3392
(m), 3042 (m), 2981 (st), 2943 (st), 2921 (st), 2870 (m), 2839 (m), 1676 (w), 1647 (w), 1589 (w), 1471
(s), 1449 (m), 1433 (m), 1397 (m), 1385 (m), 1370 (m), 1364 (m), 1331 (m), 1283 (s), 1249 (s), 1242
(s), 1210 (s), 1188 (s), 1112 (s), 1044 (m), 1022 (m), 991 (m), 946 (w), 935 (m), 896 (s), 871 (m), 835
(m), 801 (m), 762 (m), 746 (m), 736 (m), 717 (m), 675 (s), 628 (s) cm−1. Anal. Calcd for C10H18O2S:
C, 59.37; H, 8.97. Found: C, 59.10; H, 9.01.
4.14. (−)-(S)-3-(tert-Butylsulfonyl)-cyclohept-1-ene 15c
Following the procedure described for the synthesis of 15a, rac-14c (172 mg, 1 mmol),
Pd2(dba)3·CHCl3 (15.5 mg, 15 µmol), 12 (31.3 mg, 45 µmol), LiO2St-Bu (256 mg, 2 mmol)
and Hex4NBr (25 mg, 57.5 µmol) in CH2Cl2 (6 mL) and water (3 mL) gave, after 2 h, 15c (192 mg,
1
89%) as a colorless solid: 93% ee [GC, Lipodex-E: tR (15c)=33.84, tR (ent-15c)=34.20; H NMR (300

246
H.-J. Gais et al. / Tetrahedron: Asymmetry 9 (1998) 235–248
22
MHz, CDCl3, 30 mol% Eu(hfc)3): δ (t-Bu) (15c) 1.98, δ (t-Bu) (ent-15c) 2.11]; mp 48°C; [α]D
1
−94 (c 1.01, CH2Cl2); H NMR (300 MHz, CDCl3) δ 1.43 (s, 9H), 1.45–1.91 (m, 4H), 2.08–2.39 (m,
4H), 3.98 (m, 1H), 5.63–6.10 (m, 2H); 13C NMR (75 MHz, CDCl3) δ 24.39 (d), 25.78 (u), 26.52 (u),
27.93 (u), 29.34 (u), 59.06 (d), 61.36 (u), 126.90 (d), 135.31 (d); MS (EI, 70 eV) m/z (rel. intensity) 95
(M+−SO2t-Bu, 52), 94 (11), 67 (24), 57 (100); IR (KBr) ν 3033 (m), 2972 (m), 2931 (s), 2859 (m), 1650
(w), 1473 (s), 1448 (m), 1398 (w), 1367 (m), 1282 (s), 1232 (m), 1191 (m), 1106 (s), 1067 (m), 1023
(w), 958 (w), 835 (m), 792 (m), 747 (m), 698 (m), 670 (s), 638 (m) cm−1. Anal. Calcd for C11H20O2S:
C, 61.07; H, 9.32. Found: C, 60.94; H, 9.30.
4.15. (−)-(R,E)-1,3-Diphenyl-3-(tert-butylsulfenyl)-prop-2-ene 17
To a solution of rac-1b (2.82 g, 10 mmol) in CH2Cl2 (50 mL) was added a solution of
Pd2(dba)3·CHCl3 (518 mg, 0.5 mmol) and ent-2b (748 mg, 2 mmol) in CH2Cl2 (20 mL) at room
temperature. After stirring the mixture for 30 min, a solution of 16 (2 mL, 10 mmol) in CH2Cl2 (30 mL)
was added gradually (1 mL/h). Stirring of the mixture was continued for 4 days at room temperature.
Water was added and the aqueous phase was extracted with CH2Cl2. The combined organic phases
were washed with brine, dried (MgSO4), and concentrated under vacuum. Purification of the residue
by chromatography (n-hexane:EtOAc, 60:1) gave 17 (1.78 g, 63%) as a colorless oil which crystallized
readily: mp 46–47°C, 92% ee [HPLC: n-hexane:i-PrOH=100:0.3, tR (17)=16.49, tR (ent-17)=17.95];
22
[α]D −20.9 (c 0.99, CHCl3); 1H NMR (300 MHz, CDCl3) δ 1.31 (s, 9H), 4.75 (d, J=6.7, 1H), 6.42 (d,
J=15.8, 1H), 6.48 (dd, J=15.8, J=6.7, 1H), 7.42–7.09 (m, 10H); 13C NMR (75 MHz, CDCl3) δ 31.77
(d), 44.84 (u), 50.58 (d), 127.29 (d), 127.71 (d), 126.62 (d), 128.24 (d), 128.85 (d), 130.50 (d), 132.36
(d), 137.12 (u), 142.55 (u); IR (kap) ν 3081 (m), 3059 (m), 3026 (s), 2960 (s), 2939 (s), 2922 (s), 2896
(m), 2861 (m), 1599 (m), 1493 (s), 1471 (m), 1451 (s), 1390 (m), 1364 (s), 1307 (w), 1209 (m), 1159
(s), 1073 (m), 1029 (m), 965 (s), 912 (w), 871 (w), 841 (w), 801 (m) cm−1; MS (EI) m/z (rel. intensity)
282 (M+, 5), 194 (14), 193 (100), 178 (10), 115 (78), 91 (16). Anal. Calcd for C19H22S: C, 80.80; H,
7.85. Found: C, 80.67; H, 7.92.
4.16. Oxidation of 17 to ent-3
To a solution of 17 (282 mg, 1 mmol, 85% ee) in dioxane (4 mL) was added at 0°C a solution of
oxone (938 mg, 1.53 mmol) in water (4 mL). Stirring of the mixture was continued for 4 h at room
temperature. Water (10 mL) was added to the white slurry, and the mixture was extracted with CHCl3.
The combined organic phases were washed with brine, dried (MgSO4), and concentrated under vacuum.
Recrystallization of the residue from EtOH gave ent-3 (202 mg, 64%) of 69% ee (HPLC).
4.17. Structure determination of the sulfone 3
Single crystals of 3 were obtained by recrystallization from EtOA–n-hexane at room temperature.
Compound 3 crystallizes in the orthorhombic space group P212121 (No. 19). 25 Reflections in the
range of 11.04°<θ<21.91° were used to determine the cell constants a=8.8678(5), b=20.7233(9), and
c=9.5767(3) Å. At a cell volume of 1759.9 Å3 and Z=4, the calculated density amounts to 1.187 g cm−3
.
8646 Reflections (Friedel pairs; h: 0-→ꢀ11; k: 0-→ꢀ25; l: 0-→ꢀ11) were collected at room temperature
on a ENRAF NONIUS CAD4 four circle diffractometer employing graphite-monochromated Cu-Kα
radiation (λ=1.54179 Å), and merged (Rint=0.03(4)) to give 3569 ‘independent’ and 2718 observed
(I>2σ(I)) reflections. The data were corrected for Lorentz and polarization but not for absorption effects.

H.-J. Gais et al. / Tetrahedron: Asymmetry 9 (1998) 235–248
247
The structure was solved by direct methods as implemented in the XTAL3.2 crystallographic program
package,27 employing GENSIN28 to generate structure invariant relationships and GENTAN29 for the
general tangent phasing procedure. All hydrogen atoms were calculated in idealized positions and their
positional parameters were kept constant in the refinement process. Their Uis were fixed at 1.5 times the
isotropic displacement parameter of the relevant heavy atoms prior to the final full-matrix least-squares
refinement on F of 200 variables which converged at R=0.048 (Rw=0.041, w=σ−2), an error of fit of
1.612, and a residual electron density of −0.6/+0.4 e·Å−3, r*=1235.30 The absolute configuration of 3
as given in Fig. 1 was determined by calculating Flack’s absolute structure parameter.31
Acknowledgements
Financial support of this work by the Deutsche Forschungsgemeinschaft (SFB 380) is gratefully
acknowledged.
References
1. Hayashi, T. In Catalytic Asymmetric Synthesis; Ojima, I., Ed.; VCH; Weinheim, 1993 and references cited therein. (b) Trost,
B. M.; van Vranken, D. L. Chem. Rev. 1996, 96, 395 and references cited therein.
2. Hiroi, K.; Makino, K. Chem. Lett. 1986, 617. (b) Hiroi, K.; Makino, K. Chem. Pharm. Bull. 1988, 36, 1749.
3. Eichelmann, H.; Gais, H.-J. Tetrahedron: Asymmetry 1995, 6, 643.
4. Trost, B. M.; Organ, M. G.; O’Doherty, G. A. J. Am. Chem. Soc. 1995, 117, 9662. (b) Trost, B. M.; Krische, M. J.; Radinov,
R.; Zanoni, G. J. Am. Chem. Soc. 1996, 118, 6297. (c) Trost, B. M.; Krueger, A. C.; Bunt, R. C.; Zambrano, J. J. Am. Chem.
Soc. 1996, 118, 6520. (d) Trost, B. M.; Radinov, R. J. Am. Chem. Soc. 1997, 119, 5962.
5. Seebach, D.; Devaquet, E.; Ernst, A.; Hayakwa, M.; Kühnle, F. N. M.; Schweizer, W. B.; Weber, B. Helv. Chim. Acta 1995,
78, 1636.
6. Gais, H.-J.; Hellmann, G.; Günther, H.; Lopez, F.; Lindner, H. J.; Braun, S. Angew. Chem. 1989, 101, 1061; Angew. Chem.
Int. Ed. Engl. 1989, 28, 1025. (b) Gais, H.-J.; Hellmann, G. J. Am. Chem. Soc. 1992, 114, 4439.
7. Pinnick, H. W.; Reynolds, M. A. J. Org. Chem. 1979, 44, 160.
8. von Matt, P.; Pfaltz, A. Angew. Chem. 1993, 105, 614; Angew. Chem. Int. Ed. Engl. 1993, 32, 566.
9. Sprintz, J.; Helmchen, G. Tetrahedron Lett. 1993, 34, 1769.
10. Dawson, G. J.; Frost, C. G.; Williams, J. M. J.; Coote, S. J. Tetrahedron Lett. 1993, 34, 3149.
11. Koch, G.; Lloyd-Jones, G. C.; Loiseleur, O.; Pfaltz, A.; Prétôt, R.; Schaffner, S.; Schnider, P.; von Matt, P. Recl. Trav. Chim.
Pays-Bas 1995, 114, 206.
12. Sustmann, S.; Rüchardt, C. Chem. Ber. 1975, 108, 3043.
13. Crystallographic data (excluding structure factors) for the structures reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre as a supplementary publication. Copies of the data can be obtained free of
charge on application to the Director, CCDC, 12 Union road, Cambridge CB21EZ [Fax: Int. code +(1223)336-033; e-mail:
deposit@chemcrys.cam.ac-uk].
14. Hayashi, T.; Yamamoto, A.; Ito, Y. J. Chem. Soc., Chem. Commun. 1986, 1090.
15. von Matt, P.; Lloyd-Jones, G. C.; Minidis, A. B.; Pfaltz, A.; Macko, L.; Neuburger, M.; Zehnder, M.; Rüegger, H.; Pregosin
P. S. Helv. Chim. Acta 1995, 78, 165.
16. Gao, Y.; Hanson, R. M.; Klunder, J. M.; Ko, S. Y.; Masamune, H.; Sharpless, K. B. J. Am. Chem. Soc. 1987, 109, 5765.
17. Eichelmann, H. Ph.D. Thesis, RWTH Aachen 1997.
18. Sprinz, J.; Kiefer, M.; Helmchen, G.; Reggelin, M.; Huttner, G.; Walter, O.; Zsolnai, L. Tetrahedron Lett. 1994, 35, 1523.
(b) Steinhagen, H.; Reggelin, M.; Helmchen, G. Angew. Chem. 1997, 109, 2199; Angew. Chem. Int. Ed. 1997, 36, 2108.
19. Togni, A.; Burckhardt, U.; Gramlich, V.; Pregosin, P. S.; Salzmann, R. J. Am. Chem. Soc. 1996, 118, 1031.
20. Brown, J. M.; Hulmes, D. I.; Guiry, P. J. Tetrahedron 1994, 50, 4493.
21. Burckhardt, U.; Baumann, M.; Togni, A. Tetrahedron: Asymmetry 1997, 8, 155.
22. NaO2St-Bu was prepared from HO2St-Bu and NaH, and HO2St-Bu was obtained by treatment of LiO2St-Bu with H3PO4.
23. Trost, B. M.; Scanlan, T. S. Tetrahedron Lett. 1986, 27, 4141.

248
H.-J. Gais et al. / Tetrahedron: Asymmetry 9 (1998) 235–248
24. Goux, C.; Lhoste, P.; Sinou, D. Tetrahedron Lett. 1992, 32, 8099. (b) Goux, C.; Lhoste, P.; Sinou, D. Tetrahedron 1994, 50,
10321.
25. Abel, E. W. J. Chem. Soc. 1960, 4406. (b) Langer, S. H.; Connell, S, Wender, I. J. Org. Chem. 1958, 23, 50.
26. Heck, R. F. Palladium Reagents in Organic Synthesis, Academic Press, London, 1985.
27. Hall, S. R.; Flack, H. D.; Stewart, J. M., Eds., XTAL3.2 Reference Manual; Universities of Western Australia, Geneva, and
Maryland, Lamb: Perth, 1992.
28. Subramanian, V.; Hall, S. R., GENSIN, In XTAL3.2 Reference Manual; Hall, S. R.; Flack, H. D.; Stewart, J. M., Eds.;
Universities of Western Australia, Geneva, and Maryland, Lamb: Perth, 1992; p. 131.
29. Hall, S. R., GENTAN, In XTAL3.2 Reference Manual; Hall, S. R.; Flack, H. D.; Stewart, J. M., Eds.; Universities of Western
Australia, Geneva, and Maryland, Lamb: Perth, 1992; p. 139.
30. Larson, A. C. In Crystallographic Computing; Ahmed, F. R.; Hall, S. R.; Huber, C. P., Eds.; Munksgaard: Copenhagen,
1969; p. 291.
31. Flack, H. D. Acta Cryst. 1983, A39, 876.
Note added in proof: Sulfones 11a (98% ee) and 11b (96% ee) were obtained in 96% yield (2 h) and 97% yield (6 h) by
using instead of rac-10a and rac-10b the corresponding racemic carbonates.