Stereochemical studies of the palladium-catalyzed rearrangements of chiral 2-alkynyl sulfinates into chiral allenyl sulfones

Article abstract of DOI:10.1016/S0040-4020(00)01111-X

Palladium-catalyzed reactions of diastereomerically pure chiral 2-alkynyl p-toluenesulfinates under very mild reaction conditions gave both enantiomers of optically active sulfonyl allenes in good yields with high stereospecificity. The stereochemistry of this transformation with the assistance of a palladium catalyst was determined. The conversion rate was measured by the HPLC analysis in accordance with the elapse of the reaction time, and the rather marked difference of the rate was observed between the diastereomeric sulfinates. A novel mechanism for this transformation with palladium catalysts is proposed.

Full text of DOI:10.1016/S0040-4020(00)01111-X

TETRAHEDRON
Pergamon
Tetrahedron 57 (2001) 1543±1550
Stereochemical studies of the palladium-catalyzed
rearrangements of chiral 2-alkynyl sul®nates into chiral
allenyl sulfones
Kunio Hiroip and Fumiko Kato
Department of Synthetic Organic Chemistry, Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai,
Miyagi 981-8558, Japan
Received 16 October 2000; accepted 20 November 2000
AbstractÐPalladium-catalyzed reactions of diastereomerically pure chiral 2-alkynyl p-toluenesul®nates under very mild reaction condi-
tions gave both enantiomers of optically active sulfonyl allenes in good yields with high stereospeci®city. The stereochemistry of this
transformation with the assistance of a palladium catalyst was determined. The conversion rate was measured by the HPLC analysis in
accordance with the elapse of the reaction time, and the rather marked difference of the rate was observed between the diastereomeric
sul®nates. A novel mechanism for this transformation with palladium catalysts is proposed. q 2001 Elsevier Science Ltd. All rights reserved.
1. Introduction
2. Results and discussion
2.1. Synthesis of chiral 2-alkynyl sul®nates
Allene functionality has been widely used as a three-carbon
unit in organic synthesis,1 being applied to cycloaddition2
and addition reactions.3 Furthermore, axial chirality of
allenes4 has received much attention for the high stereo-
speci®city of the reactions with them in asymmetric
synthesis. In recent years, in particular, much interest has
been focused on the transition metal-catalyzed reactions of
allenyl compounds.5 We have so far investigated asym-
metric synthesis by palladium-catalyzed reactions of
allenes6 and palladium-catalyzed enantiospeci®c reactions
of chiral allenes.7 Hitherto, however, there has appeared no
general and ef®cient synthetic way readily accessible to
chiral allenes. Currently, we have been developing a novel
method for the easy preparation of both enantiomers of
chiral allenes. Previously we achieved successfully asym-
metric synthesis of chiral allylic sulfones by thermal8 or
palladium-catalyzed chiral allylic sul®nate±sulfone
rearrangements.9 We have applied this methodology to
synthesis of chiral allenes.
The 2-alkynyl sul®nates (Ss,S)-3a and 4a, and (Ss,R)-3b
and 4b were obtained with 95% stereospeci®city in 88%
yield of equal amounts of the diasteroisomers by means
of our method,11 namely the BF3´OEt2-mediated alcoholysis
of (S)-(1)-N,N-dimethyl-p-toluenesul®namide (2) with
2-alkynyl alcohols (^)-1a,b in toluene at 08C for 6 or 7 h
(Scheme 1). The diastereomeric sul®nates 3a,b and 4a,b
were isolated by column chromatography over silica gel.
The absolute con®guration of the sulfur atom in the chiral
sul®nates 3a,b and 4a,b obtained above were determined as
(S) by the highly stereospeci®c reactions of the sul®nates
with phenylmagnesium bromide with inversion of con-
®guration, affording (R)-(1)-phenyl tolyl sulfoxide of
known absolute con®guration.12 The stereospeci®city of
the BF3´OEt2-mediated reaction of (S)-2 with 1a,b was
determined on the basis of the enantiomeric excess (e.e.)
of (S)-2 used and the optical purity (e.e. of the phenyl
tolyl sulfoxide obtained above) of the sulfur atoms in 3a,b
and 4a,b obtained. The absolute con®guration of the chiral
carbon centers in 3a,b and 4a,b was determined by chemical
correlation to 1-butyn-3-yl acetate13 and 1-ocyn-3-ol14 of
known absolute con®guration.
We report here details of our stereochemical studies on
palladium-catalyzed transformation of chiral 2-alkynyl
sul®nates into sulfonyl allenes, and propose a mechanism
of the asymmetric transformation on the basis of the stereo-
chemical results obtained.10
2.2. The palladium-catalyzed reactions of chiral 2-
alkynyl sul®nates
Keywords: allenes; asymmetric reactions; palladium and compounds;
sul®nic acids and derivatives; sulfonyl compounds.
Corresponding author. Tel.: 181-22-234-4181 (ext. 2531); fax: 181-22-
275-2013; e-mail: khiroi@tohoku-pharm.ac.jp
The 2-alkynyl sul®nates were thermally transformed into
sulfonyl allenes.15 The transformation was facilitated by
the palladium catalysis. The chiral 2-alkynyl sul®nates
p
0040±4020/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(00)01111-X

1544
K. Hiroi, F. Kato / Tetrahedron 57 (2001) 1543±1550
Scheme 1.
Scheme 2.
(Ss,S)-3a and 4a or (Ss,R)-3b and 4b obtained above were
treated with Pd(OAc)2 (0.05 equiv.) in THF at room
temperature in the presence of phosphine ligands
(0.075 equiv.) to afford (S)-(1)-sulfonyl allenes 5a,b or
(R)-(2)-5a,b, respectively (Scheme 2). The e.e. of the
products was determined by the HPLC analysis with Chir-
alpak AD. The stereospeci®city of the reaction was calcu-
lated on the optical purity of the starting sul®nates (87%
e.e.) used and the allenes obtained. The results obtained
are summarized in Table 1. The palladium-catalyzed reac-
tion of (Ss,S)-4a and (Ss,R)-4b provided slightly lower
stereospeci®city in comparison to that of the methyl-substi-
tuted substrate 3a,b, as shown in Table 1. The unequivocal
effects of phosphine ligands in the palladium-catalyzed
reactions were observed. Use of dpph as a ligand provided
the highest stereospeci®city.
Table 1. Palladium-catalyzed transformation of chiral sul®nates 3a,b and
4a,b into chiral allenes 5a,ba
Sul®nate
Ligand
Reaction
time
(h)
Isolated
yield
(%) of 5
Stereospeci®city
(%)b
[absolute
con®guration]
(Ss,S)-3a
(Ss,R)-3b
(Ss,S)-3a
(Ss,R)-3b
(Ss,S)-3a
(Ss,R)-3b
(Ss,S)-3a
(Ss,R)-3b
(Ss,S)-4a
(Ss,R)-4b
(Ss,S)-4a
(Ss,R)-4b
(Ss,S)-4a
(Ss,R)-4b
dppe
dppe
dppb
dppb
dpph
dpph
PPh3
PPh3
dppb
dppb
dpph
dpph
PPh3
PPh3
18
18
18
18
18
18
16
16
28
18
24
24
24
24
65 (5a)
75 (5a)
72 (5a)
80 (5a)
74 (5a)
89 (5a)
65 (5a)
64 (5a)
46 (5b)
50 (5b)
39 (5b)
51 (5b)
53 (5b)
61 (5b)
88 (S)
85 (R)
82 (S)
83 (R)
80 (S)
89 (R)
79 (S)
77 (R)
64 (S)
72 (R)
69 (S)
73 (R)
60 (S)
73 (R)
The yields of 5a,b from (Ss,S)-3a and 4a or (Ss,R)-3b and
4b were plotted by the HPLC analysis with Chiralpack AD
in accordance with the elapse of the reaction time, and
depicted in Figs. 1 and 2. The unequivocal difference of
the conversion rate between the diastereoisomers was
observed as shown in the Figs. 1 and 2; the conversion
rate of (Ss,R)-3b and 4b was greater than that of the corre-
sponding diastereoisomers (Ss,S)-3a and 4a. The stereospe-
ci®city in the transformation of each diastereoisomer was
not changeable with the elapse of the reaction time.
a
The sul®nates (Ss,S)-3a and 4a or (Ss,R)-3b or 4b (87% e.e.) were treated
with Pd(OAc)2 (0.05 equiv.) in the prsence of a phosphite ligand
[0.075 equiv. except for PPh3 (0.10 equiv.)] in THF at room temperature;
dppe: 1,2-bis(diphenylphosphino)ethane; dppb: 1,3-bis(diphenylphos-
phino)butane; dpph: 1,6-bis(diphenylphosphino)hexane.
The stereospeci®city of the transformation was calculated by the e.e. of
the starting sul®nates (87% e.e.) and the products 5a,b obtained by HPLC
analysis with Chiralpack AD.
b
Similar results were obtained in the thermal transformation

K. Hiroi, F. Kato / Tetrahedron 57 (2001) 1543±1550
1545
Figure 1. The conversion rate of (Ss,S)-3a and (Ss,R)-3b into (S)- or (R)-5a under palladium-catalyzed reaction conditions [Pd(OAc)2, dppb, in THF, at 228C].
Figure 2. The conversion rate of (Ss,S)-4a and (Ss,R)-4b into (S)- or (R)-5b under palladium-catalyzed reaction conditions [Pd(OAc)2, dppb, in THF, at 228C].
of the chiral 2-alkynyl sul®nates into the sulfonyl allenes
under heating at re¯ux in toluene. The results are sum-
marized in Table 2. The yields of 5a,b from of (Ss,S)-3a
and 4a or (Ss,R)-3b and 4b were plotted by the HPLC
analysis in a similar way in accordance with the elapse of
the reaction time. As shown in Figs. 3 and 4, the conversion
rate of (Ss,R)-3b and 4b was greater than that of the corre-
sponding diastereoisomers (Ss,S)-3a and 4a, similar to the
palladium catalysis mentioned above. The greater difference
of the conversion rate between each diastereomer was
dependent upon the increasing steric bulk of the substituents
in the 2-alkynyl groups.
Table 2. Thermal transformation of chiral sul®nates 3 and 4 into chiral
allenes 5a
Alkynyl
sul®nates
3 and 4
Reaction
time
(h)
Yield
of 5
(%)
Stereospeci®city
(%)b
[absolute
con®guration]
(Ss,S)-3a
(Ss,R)-3b
(Ss,S)-4a
(Ss,R)-4b
16
16
15
14
96 (5a)
94 (5a)
100 (5b)
100 (5b)
98.6 (S)
99.0 (R)
94.7 (S)
91.8 (R)
a
The reactions of (Ss,S)-3a and 4a or (Ss,R)-3b and 4b (87% e.e.) were
carried out in re¯uxing toluene.
The stereospeci®city of the transformation was calculated by the e.e. of
the starting sul®nates (87% e.e.) used and the products 5a,b obtained by
HPLC analysis with Chiralpack AD.
This thermal transformation of (Ss,S)-3a and 4a or (Ss,R)-3b
and 4b proceeds by a [2,3]sigmatropic rearrangement15
via a ®ve-membered-like cyclic intermediate 6a,b to give
b

1546
K. Hiroi, F. Kato / Tetrahedron 57 (2001) 1543±1550
Figure 3. The conversion rate of (Ss,S)-3a and (Ss,R)-3b into (S)- or (R)-5a under thermal reaction conditions [on re¯ux in toluene].
(R)-8a, followed by the sulfonylation with retention of
con®guration via (R)-8b to provide (R)-5a,b. This is not
consistent with the result obtained. The substitution of the
sul®nate with the palladium catalyst at the a-carbon of the
2-alkynyl group in (Ss,S)-3a and 4a with inversion of
con®guration affords (R)-7a. The intramolecular sulfonyl-
ation via (R)-7b with retention of con®guration gives
(R)-5a,b. However, this is not consistent with the experi-
mental result. Therefore, it might be more reasonable that
the sulfonylation of (R)-7a by conjugate addition of the
p-toluenesulfonyl anion with inversion of con®guration
gives (S)-5a,b. However, if (R)-7a would be the most
important key intermediate, the stereospeci®city of the
reactions, chemical yield of allenes, and the conversion
rate of the diastereomeric sul®nates should not be change-
able in each diastereomer.
Figure 4. The conversion rate of (Ss,S)-4a and (Ss,R)-4b into (S)- or (R)-5b
under thermal reaction conditions [on re¯ux in toluene].
Furthermore, this reaction path to (S)-5a,b via (R)-7a should
be rejected by the following result of the cross-sulfonylation
reactions: (1) the palladium-catalyzed reactions of (Ss,S)-3a
and 4a or (Ss,R)-3b and 4b were carried out in the presence
of sodium benzenesul®nate to give (S)- or (R)-5a,b, respec-
tively, without any formation of the corresponding phenyl-
sulfonyl allenes; (2) the palladium-catalyzed reaction of
(^)-3 (1.0 equiv.) and 9 (1.0 equiv.) in THF at room
temperature for 18 h using Pd(OAc)2 (0.05 equiv.) and
dpph (0.075 equiv.) gave an equal amount of (^)-5a (83%
yield) and 11 (86% yield) without any cross-sulfonylation
products 10 and 12 (Scheme 5). These results indicate that
the aforementioned palladium-catalyzed reactions of the
2-alkynyl sul®nates would proceed, not via an ionic
intermediate (R)-7a, but through an intramolecular trans-
formation mechanism.
Scheme 3.
(S)-(1)-5a,b or (R)-(2)-5a,b in high stereospeci®city,
respectively, as shown in Scheme 3. The absolute con-
®guration of the products was also con®rmed by the
application of the Lowe rule.16
Thus, we wish to propose another novel mechanism via
palladium-mediated intermediates for this transformation
by the direct participation of chirality of the sul®nate in
the crucial stage of the transition states (see Scheme 6).
The palladium-catalyzed reaction of (Ss,S)-3a and 4a will
take place by the initial formation of 13a coordinated by the
acetylene group and the sul®nate sulfur atom, which has
higher potential ability of coordination to palladium rather
than the sul®nate oxygen atom.17 The allenylpalladium
2.3. The mechanism of the palladium-catalyzed
transformation
The plausible mechanism of this transformation is presented
as follows (see Scheme 4). The conjugate addition of a
palladium catalyst to the g-carbon of the 2-alkynyl group
in (Ss,S)-3a and 4a with inversion of con®guration gives

K. Hiroi, F. Kato / Tetrahedron 57 (2001) 1543±1550
1547
Scheme 4.
Scheme 5.
complex 14a would be formed via 13a with retention of
con®guration. The intramolecular sulfonylation of 14a
with retention of con®guration provides (S)-5a,b. Similarly,
the palladium-catalyzed reaction of another diastereoisomer
(Ss,R)-3b or 4b proceeds via 13b and 14b to give (R)-5a,b.
The aforementioned observation of the difference in the
transformation rate between both the diastereoisomers
(Figs. 1 and 2) should be reasonably understandable. The
transition state 13a has steric hindrance between R and the
tolyl group owing to the cis con®guration in the ®ve-
membered-like intermediate. Therefore, the reaction via
13a could not be accessible with ease, and provided the
rather slower conversion rate, as shown in Fig. 1, and the
slightly lower stereospeci®city, presumably due to proceed-
ing via a somewhat ionized intermediate, compared with
that derived from 13b.
On the other hand, the coordination of the sul®nate oxygen
atom to the palladium catalyst, if possible, provides a six-
membered-like intermediate, which gives incorrect stereo-
chemical results, due to a similar argument.
Similar observations were detected in the thermal trans-
formation of the chiral sul®nates into allenes, and are
Scheme 6.

1548
K. Hiroi, F. Kato / Tetrahedron 57 (2001) 1543±1550
rationalized as a result of the formation of the similar cyclic
intermediates as mentioned before (Scheme 3).
4.1.1. (S)-1-Butyn-3-yl (S)-p-toluenesul®nate (3a). 50%
yield. [a]Dˆ2121.88 (c 1.42, EtOH, 288C) (87% e.e.). IR
cm21: 3270 (CxCH), 2120 (CxC), 1595 (aromatic),
film
max
n
1130 (sul®nate). NMR (CCl4) d: 1.53 (3H, d, Jˆ7 Hz,
CHCH3), 2.50 (3H, s, C6H4CH3), 2.59 (1H, d, Jˆ2 Hz,
CxCH), 4.90±5.29 (1H, m, OZCH), 7.38±7.95(4H, m,
C6H4). MS m/z: 208 (M1). Exact mass determination:
208.0378 (Calcd C11H12O2S: 208.0558).
3. Conclusion
We have found that the palladium-catalyzed reactions of
each diastereomer of chiral 2-alkynyl sul®nates resulted in
the ready formation of both enantiomers of chiral allenes
4.1.2. (R)-1-Butyn-3-yl (S)-p-toluenesul®nate (3b). 50%
yield. [a]Dˆ213.28 (c 1.59, EtOH, 288C) (87% e.e.). IR
with considerably high e.e. We proposed
a novel
mechanism of the intramolecular palladium-catalyzed
rearrangement via a ®ve-membered-like cyclic intermediate
for this transformation. This is the ®rst example of the
synthesis of chiral allenes from propargylic alcohol
derivatives bearing chiral leaving groups.
cm21: 3300 (CuCH), 2120 (CuC), 1590 (aromatic),
film
max
n
1130 (sul®nate). NMR (CCl4) d: 1.55 (3H, d, Jˆ7 Hz,
CHCH3), 2.17 (1H, d, Jˆ2 Hz, CuCH), 2.46 (3H, s,
C6H4CH3), 4.73±5.17 (1H, m, OZCH), 7.26±7.90 (4H, m,
C6H4). MS m/z: 208 (M1). Exact mass determination:
208.0012 (Calcd. C11H12O2S: 208.0558).
4. Experimental
4.1.3. (S)-1-Octyn-3-yl (S)-p-toluenesul®nate (4a).
[a]Dˆ2118.98 (c 4.07, EtOH, 228C) (87% e.e.). IR nmfilamx
cm21: 3330 (CuCH), 2125 (CuC), 1600 (aromatic),
1140 (sul®nate). NMR (CCl4) d: 0.56±1.00 (3H, m,
(CH2)4CH3), 1.05±1.89 (8H, m, (CH2)4CH3), 2.35 (3H, s,
C6H4CH3), 2.41 (1H, d, Jˆ7 Hz, CuCH), 4.45±5.83 (1H,
m, OZCH), 6.90±7.49 (4H, m, C6H4). MS m/z: 264 (M1).
Exact mass determination: 264.1056 (Calcd. C15H20O2S:
264.1184).
Infrared (IR) spectra were obtained in the indicated state
with a JASCO DR-81 Fourier-transform IR spectrometer.
NMR spectra were determined in the indicated solvent with
a JEOL EX-270 (1H-NMR; 270 MHz) high-resolution NMR
spectrometer; chemical shifts are given in ppm from tetra-
methylsilane as an internal standard. Splitting patterns are
designated as s: singlet, d: doublet, q: quartet, m: multiplet.
Mass spectra were taken on a JEOL JMS-DX 303/JMA-DA
5000 system. High performance liquid chromatography
(HPLC) was performed with a Tosoh UV-8010 CCPM
(column: Daicel Chiralpak AD, i-PrOH±hexane 5:95, ¯ow
rate 1.0 mL/min, 254 nm). Optical rotations were measured
with a JASCO DIP-370 polarimeter. Flash column chroma-
tography was performed with Merck Silica gel 60 (230±400
mesh). Thin layer or thick layer plates (preparative TLC)
were made from Merck Silica gel 60PF-254 activated by
drying at 1408C for 3.5 h.
4.1.4. (R)-1-Octyn-3-yl (S)-p-toluenesul®nate (4b).
[a]Dˆ227.78 (c 1.30, EtOH, 288C) (87% e.e.). IR nmfilamx
cm21: 3330 (CuCH), 2130 (CuC), 1600 (aromatic),
1140 (sul®nate). NMR (CCl4) d: 0.68±1.10 (3H, m,
(CH2)4CH3), 1.15±1.96 (8H, m, (CH2)4CH3), 2.15 (1H, d,
Jˆ2.8 Hz, CuCH), 2.48 (3H, s, C6H4CH3), 4.66±5.00 (1H,
m, OZCH), 7.43±7.91 (4H, m, C6H4). MS m/z: 264 (M1).
Exact mass determination: 264.0983 (Calcd. C15H20O2S:
264.1184).
4.1. Synthesis of optically active 2-alkynyl p-toluene-
sul®nates. General procedure
4.2. Reaction of chiral sul®nates 3a,b and 4a,b with
phenylmagnesium bromide
A 25 mL two-necked ¯ask equipped with a septum inlet was
placed with a stirring bar, ¯ushed with nitrogen, and main-
tained under a positive pressure of argon.
A 2 M THF solution of phenylmagnesium bromide (0.8 mL,
0.36 mmol) was added to a solution of chiral sul®nates
(Ss,S)-3a and 4a or (Ss,R)-3b and 4b (0.31 mmol) obtained
above in THF (5 mL) cooled to 2788C. The reaction
mixture was stirred at 2788C for 2 h. After the reaction
was completed, the cooling bath was removed, and the reac-
tion solution was quenched with 10% aqueous HCl and
extracted with ether. The ethereal layers were combined,
dried over anhydrous Na2SO4, and concentrated in vacuo.
The residual oil was submitted to preparative TLC (hexane±
ether 1:2) to give almost quantitatively (R)-(1)-phenyl
p-tolyl sulfoxide ([a]Dˆ1228 (acetone)13) with high e.e.
(95%).
A solution of (S)-(1)-N,N-dimethyl-p-toluenesul®namide
(2) ([a]Dˆ1111.58 (acetone, 248C), 91.6% e.e.18)
(300 mg, 1.42 mmol) in anhydrous toluene (8 mL) was
added to the ¯ask, followed by the addition of a solution
of 2-alkynyl alcohols (1a,b) (4.27 mmol) in anhydrous
toluene (2 mL). A solution of boron tri¯uoride etherate
(0.2 mL, 1.42 mmol) in anhydrous toluene (1 mL) was
added to the above ¯ask cooled to 08C, and the reaction
mixture was stirred at 08C for 6±8 h. The reaction mixture
was diluted with ether, and the mixture was washed with a
saturated NaHCO3 aqueous solution and a saturated NaCl
aqueous solution. The ethereal layer was separated, dried
over anhydrous Na2SO4, and concentrated under reduced
pressure. The residue was submitted to ¯ash column chro-
matography over silica gel (ether±hexane 1:2) to give a 1:1
diastereomeric mixture of sul®nates (Ss,S)-3a and 4a and
(Ss,R)-3b and 4b in good yields with 87% e.e., which was
determined by transformation into (R)-(1)-phenyl p-tolyl
sulfoxide as described later.
4.3. Hydrolysis of chiral sul®nates 4a,b
A solution of KOH (33mg, 0.60 mmol) in methanol (2 mL)
was added to a solution of (Ss,S)-4a (79 mg, 0.30 mmol)
obtained before in methanol (1 mL), and the reaction
mixture was stirred at room temperature for 1 h. The reac-
tion solution was concentrated in vacuo, and the residue was
dissolved with chloroform. The chloroform solution was

K. Hiroi, F. Kato / Tetrahedron 57 (2001) 1543±1550
1549
washed with a saturated aqueous NaCl solution, dried over
anhydrous Na2SO4, and concentrated in vacuo. The residue
was submitted to preparative TLC (hexane±ethyl acetate
6:1) to give (S)-(2)-1-octyn-3-ol [32 mg, 84% yield;
[a]Dˆ219.68 (c 2.20, ether, 228C)] [lit.15 [a]Dˆ222.38
(ether)]. Hydrolysis of (Ss,R)-4b (79 mg, 0.30 mmol)
obtained before under the same reaction conditions
mentioned above gave (R)-(1)-1-octyn-3-ol [30 mg, 79%
yield, [a]Dˆ120.68 (c 1.14, ether, 208C)].
Table 1, and the conversion rate of 4a,b into 5b is depicted
in Fig. 2. The [a]D values of 5a,b obtained above are
corrected as for those of the optically pure allenes on the
basis of the data by the HPLC analysis.
4.5.1. (S)-(1)-1,2-Butadienyl p-tolyl sulfone (5a). [a]Dˆ
1124.68(c 0.80, EtOH, 248C). IR n cm21: 1955 (allene),
film
max
1590 (aromatic), 1300, 1140 (sulfone). NMR (CCl4) d: 1.74
(3H, q, Jˆ4 Hz, CyCHCH3), 2.41 (3H, s, C6H4CH3), 5.53±
6.22 (2H, m, HZCyCyCZH), 7.06±7.86 (4H, m, C6H4).
MS m/z: 208 (M1). Exact mass determination: 208.1390
(Calcd. C11H12O2S: 208.0558).
4.4. Transformation of (Ss,S)-3a into (S)-(2)-1-butyn-3-
yl acetate
4.5.2. (R)-(2)-1,2-Butadienyl p-tolyl sulfone (5a).
[a]Dˆ2129.98 (c 1.64, EtOH, 248C). The IR and NMR
spectra of (R)-(2)-5a obtained were superimposable with
those of (S)-(1)-5a described above. MS m/z: 208 (M1).
Exact mass determination: 208.0789 (Calcd C11H12O2S:
208.0558).
A solution of KOH (186 mg, 3.33 mmol) in methanol
(2 mL) was added to a solution of (Ss,S)-3a (346 mg,
1.66 mmol) obtained before in methanol (1 mL). The reac-
tion mixture was stirred at room temperature for 1 h. The
reaction was worked-up in the usual way as described
above. The crude product was submitted to an acetylation
reaction without further puri®cation. A reaction mixture of
the crude alcohol (1-butyn-3-ol) obtained above and acetic
anhydride (0.25 mL, 2.49 mmol) in pyridine (1 mL) was
stirred at room temperature for 16 h. The reaction mixture
was dissolved in ether. The solution was washed with 10%
aqueous HCl, saturated aqueous NaHCO3, and saturated
aqueous NaCl. The ethereal layer was dried over anhydrous
Na2SO4, and concentrated in vacuo. The residue was
submitted to preparative TLC (hexane±ethyl acetate 6:1)
to give (S)-(2)-1-butyn-3-yl acetate13 [70 mg, 60% yield,
[a]Dˆ2120.68 (c 2.57, MeOH, 248C)]. The reactions of
(Ss,R)-3b obtained before under the same reaction condi-
tions described above gave (R)-(1)-1-butyn-3-yl acetate
(70 mg, 60% yield, [a]Dˆ1125.38 (c 2.25, MeOH, 248C).
4.5.3. (S)-(1)-1,2-Octadienyl p-tolyl sulfone (5b).
[a]Dˆ1124.58 (c 0.72, EtOH, 248C). IR nfmilamx cm21: 1960
(allene), 1600 (aromatic), 1330, 1140 (sulfone). NMR
(CCl4) d: 0.96±1.26 (3H, m, CH2CH3), 1.36±1.63 (6H, m,
(CH2)3CH3), 2.09±2.43 (2H, m, CyCCH2), 2.55 (3H, s,
C6H4CH3), 5.71±6.33 (2H, m, HZCyCyCZH), 7.42±
8.23 (4H, m, C6H4). MS m/z: 264 (M1). Exact mass
determination: 264.1089 (Calcd. C15H20O2S: 264.1184).
4.5.4. (R)-(2)-1,2-Octadienyl p-tolyl sulfone (5b).
[a]Dˆ2130.08 (c 1.60, EtOH, 248C). The IR and NMR
spectra of (R)-(2)-5b obtained were superimposable with
those of (S)-(1)-5b described above. MS m/z: 264 (M1).
Exact mass determination: 264.0721 (Calcd. C15H20O2S:
264.1184).
4.5. Palladium-catalyzed transformation of chiral
sul®nates (Ss,S)-3a and 4a and (Ss,R)-3b and 4b into
sulfonyl allenes 5a,b. General procedure
4.6. Thermal transformation of chiral sul®nates into
allenes. General procedure
A 25 mL two-necked ¯ask equipped with a septem inlet and
containing palladium acetate (Pd(OAc)2) (2.7 mg,
0.01 mmol) and 1,2-bis-(diphenylphosphino)ethane (dppe)
(30 mg, 0.02 mmol) was ¯ashed with argon, and maintained
under a positive pressure of argon. To the above ¯ask THF
(2 mL) was added and the mixture was stirred at room
temperature for 30 min. A solution of (Ss,S)-3a or (Ss,R)-
3b (50.0 mg, 0.42 mmol) obtained before in THF (1 mL)
was added to the above solution, and the reaction mixture
was stirred at room temperature for 16±18 h. After the reac-
tion was completed, the reaction mixture was diluted with
ether and ®ltered. The ®ltrate was concentrated in vacuo and
the residue was submitted to preparative TLC (hexane±
ether 2:1) to give allenes, (S)-(1)- or (R)-(2)-5a, respec-
tively. The result obtained under various reaction conditions
using various phosphine ligands are summarized in Table 1.
The conversion rate of 3a,b into 5a, when 1,4-bis(diphenyl-
phosphinobutane) (dppb) was used as a ligand, was deter-
mined by HPLC analysis with Chiralpak AD (i-PrOH±
hexane (5:95), ¯ow rate 1.0 mL/min (254 nm), retention
time: 16.3 min. [(S)-5a], 18.1 min [(R)-5a], 12.1 min [(S)-
5b], and 14.2 min [(R)-5b)], and plotted in accordance with
the elapse of the reaction time, as designated in Fig. 1.
Similar reaction conditions and procedure were applied to
(Ss,S)-4a and (Ss,R)-4b. The results are summarized in
A solution of chiral sul®nates (Ss,S)-3a and 4a or (Ss,R)-3b
and 4b (0.372 mmol) (87% e.e.) obtained before in toluene
(3.5 mL) was re¯uxed for 14±16 h. The reaction solution
was concentrated in vacuo and the residue was submitted
to preparative TLC (ether±hexane 1:4) to give allenes,
(S)-(1)- or (R)-(2)-5a,b, respectively. The results are
summarized in Tables 2 and 3. The products were identical
to those obtained above. The conversion rate was plotted by
the HPLC analysis in accordance with the elapse of the
reaction time, and depicted in Figs. 3 and 4.
Table 3. Thermal transformation of chiral sul®nates 3 and 4 into chiral
allenes 5a
2-Alkynyl
sul®nates
3a,b and 4a,b
Reaction
time
(h)
Yield
of 5
(%)
[a]D
(c, 8C, EtOH) of 5
(Ss,S)-3a
(Ss,R)-3b
(Ss,S)-4a
(Ss,R)-4b
16
16
15
14
96 (5a)
94 (5a)
100 (5b)
40 (5b)
199.48 (1.80, 25)
2113.08 (1.00, 24)
1108.38 (0.72, 24)
2118.58 (1.08, 24)
a
The reactions were carried out in re¯uxing toluene.

1550
K. Hiroi, F. Kato / Tetrahedron 57 (2001) 1543±1550
4.7. Studies on a cross-sulfonylation reaction
detected by HPLC analysis (Chiralpak AD, i-PrOH±hexane
(5:95), ¯ow rate 1.0 mL/min; retention time: 10.8 min (11),
16.3 min [(S)-5a], and 18.1 min [(R)-5a)]. The products 5a
and 11 were identical to those obtained before.
4.7.1. 2-Butynyl benzenesul®nate (9). A solution of
benzenesul®nyl chloride (2.69 g, 16.8 mmol) (generated
from sodium benzenesul®nate and thionyl chloride) in
ether (10 mL) was added to a mixture of 2-butynol
(806 mg, 11.5 mmol) and pyridine (7 mL) in ether
(30 mL) cooled at 08C. The reaction mixture was stirred at
room temperature for 8 h. The reaction mixture was diluted
with ether and ®ltered. The ®ltrate was washed successively
with a 10% aqueous HCl solution, a saturated aqueous
NaHCO3 solution, and a saturated NaCl solution, dried
over anhydrous Na2SO4, and concentrated in vacuo. The
residue was submitted to preparative TLC (ether±hexane
1:3) to give 9 (1.65 g, 76% yield).
Acknowledgements
The present work was supported by a Grant-in-Aid for
Scienti®c Research from the Ministry of Education,
Science, Sports and Culture, Japan.
References
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The reaction of 1-butyn-3-ol (538 mg, 7.70 mmol) with
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out in a similar way to give (^)-3 (1.50 g, 84% yield),
which was identical to that obtained before.
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IR nmfilamx cm21: 2240 (ZCuCZ), 1144 (ZSOZOZR). NMR
(CCl4) d: 1.82 (3H, s, CH3), 4.27±4.63 (2H, m, CH2), 7.53±
7.76 (5H, m, C6H5). MS m/z: 195 (M111). Exact mass
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9 (50 mg,
palladium-catalyzed reaction of sul®nate
0.26 mmol) was carried out in THF (4 mL) at room
temperature for 24 h in the presence of Pd(OAc)2 (2.9 mg,
0.013 mmol)
and
1,6-bis(diphenylphosphino)hexane
(dpph). The usual work-up as described before and puri®ca-
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film
max
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194.0402).
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4.8. A cross-sulfonylation reaction between (^)-3 and 9
The cross-sulfonylation reaction between (^)-3 and 9 was
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0.25 mmol) in THF (3 mL) was added to a mixture of
Pd(OAc)2 (5.6 mg, 0.025 mmol) and 1,6-bis(diphenyl-
phosphino)hexane (dpph) (17 mg, 0.038 mmol) in THF
(5 mL) under argon atmosphere. The reaction mixture was
stirred at room temperature for 18 h. The usual work-up as
described before, followed by puri®cation with preparative
TLC, gave (^)-5a (43 mg, 83% yield) and 11 (42 mg, 86%
yield). No cross-sulfonylation products 10 and 12 were
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