Do the electronic effects of sulfur indeed control the π-selectivity of γ-sulfenyl enones? An investigation

Article abstract of DOI:10.1021/jo034608c

The electronic effects of sulfur in γ-sulfenyl enones are not transmitted to the carbonyl carbon through the π bond as reported previously. The diastereoselectivity is rather controlled by a combination of several other factors. The steric effects arising

Full text of DOI:10.1021/jo034608c

Do th e Electr on ic Effects of Su lfu r In d eed Con tr ol th e
π-Selectivity of γ-Su lfen yl En on es? An In vestiga tion †
Veejendra K. Yadav,*,‡ K. Ganesh Babu,‡ and Masood Parvez§
Department of Chemistry, Indian Institute of Technology, Kanpur 208 016, India, and
Department of Chemistry, University of Calgary, Calgary, Alberta, Canada T2N 1N4
vijendra@iitk.ac.in
Received May 9, 2003
The electronic effects of sulfur in γ-sulfenyl enones are not transmitted to the carbonyl carbon
through the π bond as reported previously. The diastereoselectivity is rather controlled by a
combination of several other factors. The steric effects arising from the substituents on the sulfur
atom and the γ-carbon and the bulk of the nucleophile constitute the major control elements.
SCHEME 1
In tr od u ction
The influence of a heteroatom that is vinylogously
adjacent to a center of nucleophilic attack has received
much attention.1 Sato et al.2 have studied the hydride
reduction of γ-sulfenyl enones. The observed high anti-
to-S selectivity was attributed to the electronic effect of
sulfur that was transmitted to the reaction center
through the π bond. It was emphasized that the observed
selectivity was neither steric- nor chelation-controlled.
Wipf et al.3 have reported high anti-to-O selection from
the reactions of 4,4-disubstituted cyclohexadienones with
Grignard reagents in support of a dipolar control model
that allowed a nucleophile to approach the carbonyl
function from the positive end of the molecular dipole.
Felkin-Anh-Cieplak-type hyperconjugative orbital sta-
bilization4 in the TS was considered secondary. This
dipolar control model, when applied to the above γ-sulfe-
nyl enones, predicts syn-to-S addition.
In contrast, Fleming et al.5 observed a complete loss
of selectivity from hydride reduction of γ-methoxy enones
that led them to conclude that the Cram selectivity6 was
largely steric in origin. Reetz et al.7 made a similar
observation from the addition of alkyllithium and Grig-
nard reagents to γ-amino and γ-alkoxy enals and con-
cluded that the possible electronic and steric effects were
not transmitted from the heteroatom to the reaction
center through the π-system. Dumaritin et al.8 observed
no or very little selectivity from the reduction of 1,1-bis-
ethoxy-5-tert-butyldiphenylsilyloxy-3-hexen-2-one. Our
own investigation of nucleophilic additions to 6-methyl-
1-oxa-4-thiaspiro[4.5]dec-6-ene-7-carbaldehyde, a sub-
strate that possessed both sulfur and oxygen at the
γ-carbon, showed only a marginal anti-to-S selection.9
However, if the rationale of electronic effects2 were true,
high anti-to-S selectivity must have prevailed for the
combined electronic effects of the two heteroatoms.
Likewise, had the dipolar control model been at work,
the syn-to-S selectivity must have predominated.
The above contrasts led us to probe steric effects, and
thus, we investigated the hydride reduction of variously
substituted γ-sulfenyl enones in detail. We describe our
results herein to demonstrate conclusively that the
observed selectivity is predominantly steric-in-origin and
that the solvent and the low temperature also contributed
to it.
Sta r tin g Ma ter ia ls
The γ-sulfenyl enones 7 were prepared by Wittig-
Horner reaction of the corresponding R-sulfenyl alde-
hydes 3 that, in turn, were prepared by following the
protocols given in Schemes 1 and 2. The R-sulfenyl esters
5 were reduced to the alcohols 6 that were oxidized to
furnish the R-sulfenyl aldehydes 3. The protocol outlined
in Scheme 2 offers the flexibility of incorporating different
substituents on sulfur as required for our studies. The
R-sulfenyl aldehydes with R1 ) Et, (CH2)4, (CH2)5, and
† Dedicated fondly to Professor Sukh Dev on the occasion of his 80th
birthday.
‡ Indian Institute of Technology.
§ University of Calgary.
(1) Mengel, A.; Reiser, O. Chem. Rev. 1999, 99, 1191.
(2) Sato, T.; Kido, M.; Otera, J . Angew. Chem., Int. Ed. Engl. 1995,
34, 2254.
(3) Wipf, P.; Kim, Y. J . Am. Chem. Soc. 1994, 116, 11678. Wipf, P.;
J ung, J .-K. Angew. Chem., Int. Ed. Engl. 1997, 36, 764.
(4) Cherest, M.; Felkin, H.; Prudent N. Tetrahedron Lett. 1968, 2199.
Anh, N. T.; Eisenstein, O. Nouv. J . Chim. 1977, 1, 61. Cieplak, A. S.
Chem. Rev. 1999, 99, 1265.
(5) Fleming, I.; Ku¨hne. H.; Takaki, K. J . Chem. Soc., Perkin Trans.
1 1986, 725.
(6) Cram, D. J .; Elhafez, F. A. A. J . Am. Chem. Soc. 1952, 74, 5828.
(7) Reetz, M. T.; Wang, F.; Harms, K. Chem. Commun. 1991, 1309.
See also: Arai, M.; Nemoto, T.; Ohashi, Y.; Nakumara, E. Synlett 1992,
309.
(8) Dumaritin, H.; Floch, Y. L.; Gree, R. Tetrahedron Lett. 1994, 35,
6681.
(9) Yadav, V. K.; J eyaraj, D. A.; Parvez, M.; Gauniyal, H. M. J . Org.
Chem. 1998, 63, 3831. Yadav, V. K.; Senthil, G.; Ganesh Babu. K.;
Parvez, M.; Reid, J . L. J . Org. Chem. 2002, 67, 1109.
10.1021/jo034608c CCC: $27.50 © 2004 American Chemical Society
Published on Web 04/29/2004
3866
J . Org. Chem. 2004, 69, 3866-3874

π-Selectivity of γ-Sulfenyl Enones
SCHEME 2
TABLE 1. Dia ster eoselectivity of Hyd r id e Ad d ition to
SCHEME 3
SCHEME 4
γ-Su lfen yl En on es 7a a ,b
entry
R1
R2
R3
yieldc (%)
ratio 9:10d
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
C2H5
Ph
Ph
Me
Me
96
92
94
94
92
94
92
91
94 (98)
93 (97)
90
97
94
93
94
93
71:29
85:15
66:34
n-C4H9
n-C4H9
i-C3H7
i-C3H7
t-C4H9
t-C4H9
n-C6H13
n-C8H17
n-C8H17
c-C5H8
c-C5H8
c-C6H10
c-C6H10
Me Me
Ph Me
Me Me
Ph Me
Me Me
86:14
68:32
91:9e
68:32
85:15
83:17 (63:37)
66:34 (54:46)
100:0
100:0
100:0
100:0
Ph
Ph
Me
Me
Me Me
Ph Me
Me Me
Ph Me
Me Me
Ph Me
Me Me
f
CH2CH2Ph and R2 ) Ph were prepared by the protocol
given in Scheme 1.10,11 All other R-sulfenyl aldehydes
were prepared as outlined in Scheme 2.
f
f
f
-CH2CH2Ph
-CH2CH2Ph
79:21
55:45g
Resu lts a n d Discu ssion
a
All the reactions were carried out in THF at -78 °C for 30
b
min using 2 equiv of L-Selectride. Values in the parentheses are
Since, in all but one substrate, the substituent on
sulfur was Ph and the substituent on the γ-carbon was
a large alkyl group (t-Bu, i-Pr, n-C6H13, n-C7H15), the
observed selectivity could very well be a consequence of
large group steric effects. Further, since the C-S bond
is almost orthogonal to the plane of the enone function
with S-C-CdC dihedral angle at ∼106°,12 the Ph on
sulfur is likely to shield one face of the enone and thus
direct a nucleophile to the other face. An evaluation of
steric and electronic effects was therefore necessary, and
we chose to study both the SPh- and SMe-substrates (7,
R2 ) Ph, Me) (Scheme 3). Again, since the bulk of R3 was
shown by the earlier investigators2 not to influence the
selectivity appreciably (e.g., the anti-to-S selectivity was
reduced from 97:3 to 94:6 to 91:9 on changing R3 from
t-Bu to i-Pr to Me, respectively, for the substrate with
R1 ) t-Bu and R2 ) Ph), we chose to study the substrates
with R3 ) Me. This allowed us to probe the steric effects
of R1, R2, and the hydride reagent.
the results from reduction with 1 equiv of NaBH4 in MeOH at
d
-78 °C. c Isolated yields. Determined from 1H integrals of
CH(OH)Me and SMe for PhS- and MeS-substrates, unless indi-
cated otherwise. e Determined from 1H integrals of CH(SPh). f The
g
γ-carbon atom is part of the ring system. Determined from 1H
integrals of OCOMe of the corresponding mixture of acetates.
selectivity than the corresponding MeS-substrates. This
is likely to be due to a more effective shielding of the syn-
to-S face of the enone by Ph than by Me that guides
Selectride to the anti-to-S face of the carbonyl function.
The selectivity was constant at about 67:33 for R1 ) n-Bu,
i-Pr, t-Bu, and n-C8H17 for the MeS-substrates just as it
was constant at about 86:14 for the PhS-substrates. The
only exception was the substrate with R1 ) t-Bu and R2
) Ph when the selectivity increased to 91:9. Interestingly,
irrespective of the substituent on the sulfur, the selectiv-
ity had increased further to 100:0 when the γ-carbon was
part of a ring system (entries 11-14). The anti-to-S
selectivity was confirmed from the X-ray structure of the
4-bromobenzoate of the sulfone derived from the alcohol
at entry 13 (Figure 1).
A notable observation was made to the effect that the
anti-to-S selectivity had decreased from about 86:14 to
78:22 for the PhS-bearing substrate when R1 was changed
from n-Bu/i-Pr to CH2CH2Ph (entry 2/4 vs 15). This is
likely to be due to a competitive shielding of the anti-
to-S face of the enone by the Ph present in R1 in much
the same manner as the Ph on S was expected to shield
the syn-to-S face. This argument draws support from the
1. Ster ic Effects of R1 a n d R2. The ratios of the
alcohols 9 and 10 formed from L-Selectride reduction of
several γ-sulfenyl enones 7a are collected in Table 1.13
The PhS-substrates showed considerably higher anti-to-S
(10) Groot, A. D.; J ansen, B. J . M. Tetrahedron Lett. 1981, 22, 887.
(11) Sato, T.; Okazaki, H.; Otera, J .; Nozaki, H. J . Am. Chem. Soc.
1988, 110, 5209.
(12) Dorgio, A. E.; Morokuma, K. J . Am. Chem. Soc. 1989, 111, 6524.
(13) The distributions of diastereomers formed from the hydride
reductions of SPh and SMe enones were determined, respectively, from
1H integrals of SMe and CH(OH)Me.
J . Org. Chem, Vol. 69, No. 11, 2004 3867

Yadav et al.
F IGURE 2. ORTEP plot of the X-ray crystal structure the
alcohol in entry 2, Table 2. Selected bond lengths (Å), bond
angles (deg), and torsional angles (deg): C(3)C(4) 1.312(3);
S(1)C(5) 1.8062(19); C(4)C(5)S(1) 108.29(12), C(3)C(4)C(5)
124.15(17); S(1)C(5)C(4)C(3) -112.12(15), C(4)C(3)C(2)O(1)
12.4 (3).
F IGURE 1. ORTEP plot of the X-ray crystal structure of the
sulfone/4-bromobenzoate of the product in entry 13, Table 1.
Selected bond lengths (Å), bond angles (deg), and torsional
angles (deg): C(7)C(8) 1.314(3), S(1)C(1) 1.837(2); C(7)C(1)S-
(1) 107.95(16); C(8)C(7)C(1) 126.4(2), S(1)C(1)C(7)C(8) 102.4
(2), C(7)C(8)C(9)O(1) 130.2(2).
event, not only did the anti-addition predominate but it
was also enhanced somewhat in comparison to that for
the corresponding sulfenyl substrates. For instance, the
selectivity had increased from 71:29 to 75:25 for the
substrate with R1 ) C2H5 and R2 ) Ph and from 91:9 to
100:0 for the substrate with R1 ) t-Bu and R2 ) Ph. The
stereostructure of the product with R1 ) t-Bu and R2 )
Ph was confirmed from its X-ray structure (Figure 2). It
is important to note that the carbon-sulfur bond is
almost orthogonal to the plane of the olefinic bond in the
product alcohol. Ab initio MO calculations at the B3LYP/
6-31G* level15 suggest that the s-cis-8 (R1 ) R3 ) Me, R2
) Ph) is slightly favored over the s-trans-8 by 0.22 kcal/
mol and that both the conformers possessed the carbon-
sulfur and C-H bonds, respectively, orthogonal to and
in-plane of the enone function.
TABLE 2. Red u ction of γ-Su lfon yl En on es 8 w ith
L-Selectr id ea
entry
R1
R2
Ph
R3
yield 11 + 12b (%) ratio 11:12c
1
2
3
C2H5
t-C4H9 Ph
t-C4H9 Me
Me
Me
Me
90
93
91
75:25
100:0
65:35
a
The reductions were carried out under conditions identical to
those for the reductions of the corresponding sulfenyl enones.
b
Isolated yields. c Determined by 1H integrals of CH(OH)Me for
SO2Ph materials and the integral of SO2Me for entry 3.
observation that the anti-to-S selectivity for the corre-
sponding MeS-derivative had also decreased from about
67:33 to 55:45 (entry 16). Our results, therefore, support
significant steric effects on the observed selectivity that
contrasts the “only electronic effects” argument.2 The
electronic effects arising from the sulfur14 influence
primarily the stable conformers distribution in compli-
ance with the stereoelectronic effects that favor the
carbon-sulfur bond to be aligned orthogonal to the plane
of the enone function.
2. Effect of Rever sin g th e Electr on ic Effects of
Su lfu r . We substantiate our claim that the preferred
anti-to-S addition of nucleophiles to the γ-sulfenyl enones
is due primarily to the steric effects and that the
electronic effects of sulfur are less importrant in the
diastereocontrol from the results obtained from L-Selec-
tride reduction of the γ-sulfonyl enones 8. The sulfur has
changed from being electron-donating in 7 to electron-
attracting in 8 (Table 2). Obviously, an addition syn-to-S
must predominate if the selectivity were indeed con-
trolled by only the electronic effects of the sulfur. In the
3. Effect of th e Bu lk of th e Hyd r id e Rea gen t. We
studied next the effect of the bulk of the reducing agent
and performed selected reactions with NaBH4 at -78 °C.
These results are also collected in Table 1. In both the
cases, NaBH4 gave only marginal anti-to-S selectivity.
The considerable drop in the anti-to-S selectivity is
instructive. The bulk of the hydride reagent is obviously
much more important than the bulks of the substituents
in the substrate for the diastereocontrol. The large bulk
of L-Selectride coupled with those of Ph or Me on S
ensured the high selectivities observed throughout by the
previous investigators.2
NaBH4 is less sensitive to the bulks of R1 and R2 than
L-Selectride because of its relatively much smaller size.
It can, therefore, approach both the faces of the enone
with considerably reduced discrimination. Had it been
(15) Frish, M. J .; Trucks, G. W.; Schlegel, H. B.; Gill, P. M. W.;
J ohnson, B. G.; Robb, M. A.; Cheeseman, J . R.; Keith, T.; Peterson, G.
A.; Montgomery, J . A.; Raghavachari, K.; Al-Laham, M. A.; Zakrzewski,
V. G.; Ortiz, J . V.; Foresman, J . B.; Cioslowski, J .; Stefanov, B. B.;
Nanayakkara, A.; Challacombe, M.; Peng, C. Y.; Ayala, P. Y.; Chen,
W.; Wong, M. W.; Andres, J . L.; Replogle, E. S.; Gomperts, R.; Martin,
R. L.; Fox, D. J .; Binkley, J . S.; Defrees, D. J .; Baker, J .; Stewart, J .
P.; Head-Gordon, M.; Gonzalez, C.; Pople, J . A. Gaussian, Inc.,
Pittsburgh, PA, 1995.
(14) The electron-donating abilities of σ-bonds increases in the
order: σCO < σCC < σCH < σCS. Epiotis, N. D.; Cherry, W. R.; Shaik, S.;
Yates, R. L.; Bernardi, F. Top. Curr. Chem. 1977, 70.
3868 J . Org. Chem., Vol. 69, No. 11, 2004

π-Selectivity of γ-Sulfenyl Enones
TABLE 3. Rea ction s of γ-Su lfen yl En on es 7a w ith
TABLE 4. Rea ction s of γ-Su lfen yl En a ls 7c w ith RMgIa
L-Selectr id e u n d er Differ en t Con d ition sa
Sl no.
R1
R2 R3
R
yield 9 + 10b (%)
9:10
yield
1
2
3
t-C4H9
t-C4H9
c-C6H10
Ph
Ph
Ph
H
H
H
Me
Ph
Me
84
87
89
58:42c
72:28c
100:0
T
(°C)
9 + 10b
entry
R1
n-C4H9 Ph Me THF
n-C4H9 Ph Me toluene
R2 R3
solvent
(%)
9:10c
d
1
2
3
4
5
6
7
-78
-78
92
90
92
87
92
93
94
85:15
74:26
76:24
73:27
85:15
75:25
66:34
a
The reactions were carried out in THF at - 78 °C for 2 h using
b
2 equiv of freshly prepared RMgI (1 M solution in Et2O). Isolated
n-C4H9 Ph Me THF/HMPA (10:1) -78
n-C4H9 Ph Me THF/HMPA (10:5) -78
yields. c Determined by 1H integrals for CH(SPh). The γ-carbon
d
is part of the ring system.
n-C8H17 Ph Me THF
n-C8H17 Ph Me THF
n-C8H17 Ph Me THF
-78
-40
0
ness of the former to the reaction center. The anti-to-S
approach of a nucleophile will then generate the product
10 that will be formed, in principle, from the syn-to-S
approach of a nucleophile to the s-cis conformer A. This
results in the loss of selectivity.
a
All the reactions were carried out for 30 min with 2 equiv of
L-Selectride. Isolated yields. c Ratios were calculated from 1H
b
integrals of CH(OH)Me.
The above steric interactions are absent in the anti-
to-S approach of a nucleophile to the s-cis conformer A.
The syn-to-S approach, however, will experience steric
interactions from the phenyl on S that, as stated above,
is conformationally fairly close to the reaction center. This
will allow the s-cis conformer A to react faster than the
s-trans conformer B. The predominant formation of 9 over
10 even at 0 °C suggests that it is possibly the s-cis
conformer A that reacted in preference to the s-trans
conformer B. The high selectivity observed with the
single methyl ketone studied by the previous investiga-
tors2 was thereofre supported additionally by the low
temperature (-78 °C) at which the reaction was per-
formed. The methyl ketone reacted primarily (or even
exclusively) through the s-cis conformer at -78 °C (vide
infra).
5. Rea ction of th e Cor r esp on d in g En a l w ith Gr ig-
n a r d Rea gen ts. With a 2-fold objective of (a) evaluating
the rationale that the substituent on sulfur indeed
controlled the selectivity and (b) indirectly confirming the
fact that the methyl ketones 7 indeed reacted largely
through the s-cis conformation at -78 °C, we considered
reacting the γ-sulfenyl enals 7c with MeMgI to generate
the same products as those formed from the hydride
reduction of the corresponding methyl ketone and also
with PhMgI to assess the impact of the bulk of the
nucleophile additionally.18 The results are collected in
Table 4. Enals exist in the s-trans conformation predomi-
nantly.16 Our own ab initio MO calculatiuons of the s-cis-
7c and s-trans-7c (R1 ) R2 ) Me) at B3LYP/6-31G* level
indicated the s-trans conformer to be 1.48 kcal/mol more
stable than the s-cis conformer.
For the reasons discussed above for the transition
structure B, more anti-to-S reaction must take place than
the alternate syn-to-S variant. In the event, MeMgI
exhibited 9c:10c ) 58:42 selectivity that was raised to
72:28 on reaction with PhMgI. Whereas the 58:42 dias-
tereocontrol observed with MeMgI is too small to support
the “only electronic effects” argument, the increase in the
anti-to-S selectivity in the reaction with PhMgI clearly
supports the steric effects argument. The increased steric
interactions of the phenyl on S with PhMgI than that
with MeMgI appears responsible for the enhanced anti-
to-S approach of the former reagent. The cycloderivative
at entry 3 reacted with remarkable anti-to-S control. The
major product 9 that is formed from the anti-to-S addition
F IGURE 3.
due to the electronic effects of S, the anti-to-S selectivity
from reduction with NaBH4 will be expected to be, more
or less, similar to the selectivity observed from reduction
with L-Selectride.
4. Effect of Solven t a n d Tem p er a tu r e. The solvent
and temperature also contributed to the selectivity. We
have studied R1 ) n-Bu and n-C8H17 with R2 ) Ph and
R3 ) Me for the study of the effects of solvent and
temperature, respectively. The results are collected in
Table 3. The selectivity dropped from 85:15 in THF to
74:26 in toluene. The solvent THF will be expected to
increase the total bulk of L-Selectride by complexation
with Li+ cation that, in turn, will increase the anti-to-S
selectivity. Such a complexation is less likely in toluene.
The increase in the polarity of the solvent by the addition
of HMPA reduced the selectivity (cf. entries 3 and 4).
HMPA will be expected to solvate Li+ and remove it away
from tri-sec-butyl borohydride. The bulk of the nucleo-
phile is, therefore, reduced, and poor anti-to-S selectivity
is observed.
The selectivity was reduced from 85:15 observed at -
ï
ï
78 °C to 75:25 and 66:34 at -40 C and 0 C (entries 5
and 7), respectively, under otherwise identical conditions.
This is likely because the contribution from the s-trans
conformer is raised at higher temperatures. Studies on
the conformational preferences of similar methyl enones
have revealed that they received contribution from both
the s-cis and the s-trans conformers.16 The incoming
nucleophile encounters steric interactions with the phen-
yl on S and n-C8H17 in the s-trans conformer B during
the additions syn and anti to the sulfur, respectively
(Figure 3).4,17 The steric interactions with the phenyl on
S will, however, be larger than the steric interactions
with n-C8H17 due to the improved conformational close-
(16) Oelichmann, H.-J .; Bougeard, D.; Schrader, B. Angew. Chem.
Suppl. 1982, 1404. Liljefors, T.; Allinger, N. L. J . Am. Chem. Soc. 1976,
98, 2745.
(17) (a) Bu¨rgi, H. B. Angew. Chem. 1975, 87, 461. (b) Bu¨rgi, H. B.
Angew. Chem., Int. Ed. Engl. 1975, 14, 460. (c) Bu¨rgi, H. B.; Dunitz,
J . D. Acc. Chem. Res. 1983, 16, 153.
(18) The enals were obtained from the reduction of the corresponding
γ-sulfenyl esters with diisobutylaluminum hydride.
J . Org. Chem, Vol. 69, No. 11, 2004 3869

Yadav et al.
TABLE 5. Dia ster eoselectivities of 7g a n d 7f w ith
Differ en t Hyd r id e Agen ts
larger drop in the selectivity of 7a at higher temperatures
must, therefore, be due to the larger participation of the
s-trans form that reacted preferably anti to the S.
yield
reducing
agent
T
9 + 10a
(%)
entry substrate
solvent (°C)
9:10b
Con clu sion
1
2
3
4
5
7f
L-Selectride THF
L-Selectride THF
L-Selectride THF
-78
-78
0
95
95
95
97
96
97:3
7g
7g
7g
7g
68:32
64:36
45:55
40:60
In conclusion, the preferred anti-to-S addition of nu-
cleophiles to γ-sulfenyl enones is not due to the electronic
effects of sulfur that was earlier considered to be trans-
mitted to the reaction center through the olefinic bond.
It is rather due to a combination of the steric effects
arising from the substituents on sulfur and the γ-carbon,
the large bulk of L-Sselectride, the low reaction temper-
ature (-78 °C), and THF as the reaction solvent. It was
the best combination of all these parameters that lead
to the very high anti-to-S selectivity observed by the
previous investigators.
NaBH4
LiAlH4
MeOH -78
Et2O -78
a
b
Isolated yield. Ratios were calculated from 1H integrals of
-CH(OH).
of MeMgI to s-trans-7c (R1 ) t-Bu, R2 ) Ph) could be
formed from the anti-to-S hydride reduction of the methyl
ketone 7 (R1 ) t-Bu, R2 ) Ph, R3 ) Me) only if the latter
reacted through its s-cis form.
6. Com p u ta tion a l Evid en ce Th a t F a vor s s-cis-7a
over s-tr a n s-7a (th e Meth yl Keton e 7a ). The methyl
ketones similar to 7a have been reported16 to exist as a
equilibrium mixture of the s-cis and the s-trans forms,
and it has been, more or less, a common belief that the
latter form is the more stable of the two. Our experi-
mental results presented above indicated otherwise, and
thus, we took to ab initio MO calculations of the species
7d (7a , R1 ) Me, R2 ) Ph) and 7e (7a , R1 ) R2 ) Me) at
the B3LYP/6-31G* level of theory. The s-cis-7d was 0.72
kcal/mol more stable than the s-trans-7d . Likewise, s-cis-
7e was 0.30 kcal/mol more stable than s-trans-7e. The
higher concentration of the s-cis form at equilibrium at
-78 °C coupled with its above-discussed superior reactiv-
ity could very well be taken to understand that it was
mainly the s-cis form of each methyl ketone (Table 1) that
had reacted. The carbon-sulfur bond is at a torsion angle
of 106.5° and 111.8° with the double bond in the com-
puted s-cis-7d and s-cis-7e, respectively. Further, the
C5-H bond on C5 of the main skeleton is syn with the
C3-H bond.
Exp er im en ta l Section
1H and 13C NMR spectra were recorded in CDCl3. The 1H
and 13C positions are reported in δ relative to TMS used as an
internal standard and the central line for CDCl3, respectively.
The solvents were removed under reduced pressure on a
rotovap. The chromatographic separations were performed
over silica gel (100-200 mesh) using mixtures of EtOAc and
hexane.
Gen er a l P r oced u r e for th e P r ep a r a tion of γ-Su lfen yl
Alcoh ols 6. A solution of ester 4 (5 mmol) in THF (5 mL) was
added slowly to a solution of LDA (6 mmol) in THF (3 mL)
ï
under stirring at -78 C. After 10 min, a solution of disulfide
(7.5 mmol) in THF (4 mL) was added, all at once, at the same
temperature, and the reaction mixture was allowed to warm
to room temperature. It was then diluted with ether, washed
with 2% HCl, H2O, and brine, concentrated, and filtered
through a short column of silica gel to afford 5. A solution of
5 in Et2O (10 mL) was added to an ethereal suspension of LAH
at 0 ïC and was gradually warmed to room temperature. After
6 h, the reaction was quenched with EtOAc. The contents were
filtered and the filtrate was concentrated. The crude material
was purified by column chromatography to afford 6.
7. F ixin g th e s-cis Con for m a tion of th e En on e a n d
Estim a tin g th e Selectivity. To eliminate doubts in
regard to the discussions presented above for the involve-
ment of the s-cis conformer of the methyl ketone, we
opted to study the substrates 7f (7, R1 ) R3 ) t-Bu and
R2 ) Ph) and 7g (7, R1 ) R3 ) t-Bu and R2 ) Me) as this
secures fully the s-cis form of the enone and allows one
to study the steric effects of both the substituent on S
(Ph vs Me) and the reducing agent. The stereochemical
data are collected in Table 5. The considerable drop in
the selectivity from 97:3 for 7f to 68:32 for 7g from
reduction with L-Selectride demonstrates the dramatic
steric effect of the substituent on the sulfur. It is to be
noted that the above selectivity of 7g is the same as that
of 7a (R1 ) t-Bu, R2 ) Me, entry 7, Table 1). This could
possibly be taken as evidence to the fact that the latter
reacted almost exclusively through the s-cis form at -
78 °C. Further, the drop in the selectivity of 7g from
68:32 from reduction with L-Selectride to 45:55 from
reduction with NaBH4 or 40:60 from reduction with
LiAlH4 demonstrates the significance of the bulk of the
hydride source in the control of the overall selectivity.
The purported electronic effects of sulfur stand evapo-
rated. A comparison of the results at entries 2 and 3
demonstrates a very small change in the selectivity on
change in the temperature. The comparatively much
Gen er a l P r oced u r e19 for th e P r ep a r a tion of γ-Su lfen yl
Ald eh yd es 3 fr om 6. (CF3CO)2O (2.25 mmol, 0.32 mL) in dry
CH2Cl2 (2 mL) was added to a solution of dry DMSO (3.0 mmol,
0.21 mL) in CH2Cl2 at -70 ïC at such a rate that the
temperature of the reaction mixture did not rise above -60
ïC. The addition took 10 min. The contents were stirred at
the same temperature for 15 min before the alcohol 6 (1.5
mmol) in CH2Cl2 (2 mL) was added. The mixture was stirred
for another 45 min, and dry diisopropylamine (4.2 mmol, 0.58
mL) was added drop by drop in about 10 min. The cooling bath
was then removed, and the contents were stirred for 45 min.
The reaction mixture was diluted with CH2Cl2, and the organic
solution was washed with H2O and brine. The residue obtained
from concentration was filtered through a short column, and
the product 3 thus obtained was used directly for further
reaction.
P r ep a r a tion of γ-Su lfen yl En on e 7a fr om 3. To a
suspension of NaH (1.2 mmol) in THF (2 mL) was added
diethyl (2-oxopropyl)phosphonate (1.2 mmol, 0.233 g) in THF
ï
(4 mL) at 0 C over 10 min. When all the NaH had dissolved,
aldehyde 3 (1 mmol) in THF (4 mL) was added. The cooling
bath was removed, and the contents were stirred for 12 h. The
reaction mixture was diluted with Et2O, washed with satu-
rated aqueous NH4Cl and brine, and concentrated. The residue
was filtered through a silica gel column to afford the enone
7a .
(19) Muncuso, A. J .; Swern, D. Synthesis, 1981, 165.
3870 J . Org. Chem., Vol. 69, No. 11, 2004

π-Selectivity of γ-Sulfenyl Enones
P r ep a r a tion of γ-Su lfen yl Ester 7b fr om 3. To a suspen-
1H), 3.51 (s, 3H), 2.87-2.80 (m, 1H), 2.76-2.63 (m, 1H), 2.26-
2.17 (m, 1H), 1.84-1.75 (m, 1H); 13C NMR δ 141.8, 133.9,
132.2, 128.8, 128.5, 128.3, 127.8, 125.7, 94.5, 71.9, 56.7, 34.3,
31.5.
sion of NaH (1.2 mmol) in THF (2 mL) was added triethyl
ï
phosphonoacetate (1.2 mmol, 0.269 g) in THF (4 mL) at 0 C.
After all the NaH had dissolved, the aldehyde 3 (1 mmol) in
THF (4 mL) was added at the same temperature. The cooling
bath was removed, and the contents were stirred for 12 h. The
reaction mixture was diluted with Et2O, washed with satu-
rated aqueous NH4Cl and brine, and concentrated. The residue
was filtered through a silica gel column to afford the ester 7b.
Gen er a l P r oced u r e for th e P r ep a r a tion of γ-Su lfon yl
En on es 8 fr om 7a . To a stirred solution of enone 7a (0.2
6 (R1 ) n -Bu , R2 ) P h , 70%, liqu id ): 1H NMR δ 7.45-7.43
(m, 2H), 7.32-7.26 (m, 3H), 3.65-3.61 (dd, J ) 11.4, 4.9 Hz,
1H), 3.53-3.49 (dd, J ) 11.5, 6.4 Hz, 1H), 3.18-3.12 (m, 1H),
2.41 (bs, 1H), 1.69-1.28 (m, 6H), 0.91 (t, J ) 7.2 Hz, 3H); 13
C
NMR δ 133.4, 132.7, 128.9, 127.3, 63.6, 52.5, 30.8, 29.2, 22.5,
13.9.
6 (R1 ) n -Bu , R2 ) Me, 68%, liqu id ): 1H NMR δ 3.68-
3.64 (dd, J ) 11.2, 4.6 Hz, 1H), 3.51-3.46 (dd, J ) 11.2, 7.3
Hz, 1H), 2.70-2.64 (m, 1H), 2.20 (bs, 1H), 2.03 (s, 3H), 1.60-
1.30 (m, 6H), 0.92 (t, J ) 7.2 Hz, 3H); 13C NMR δ 62.7, 50.0,
30.4, 29.2, 22.5, 13.9, 11.8.
ï
mmol) in 4 mL of CH2Cl2 at -10 C was added m-CPBA (0.4
mmol, 0.098 g, 70%), and the resultant mixture was stirred
at the same temperature for 30 min. The reaction mixture was
then diluted CH2Cl2, washed with saturated aqueous NaHCO3,
water, brine, concentrated, and purified using radial chroma-
tography to obtain γ-sulfonyl enones 8 in >80% yield.
Gen er a l P r oced u r e for th e L-Selectr id e Red u ction of
γ-Su lfen yl En on es 7a a n d γ-Su lfon yl En on es 8. To a
solution of 7a or 8 (0.1 mmol) in THF (1 mL) was added
L-Selectride (1.0 M THF solution, 0.2 mmol, 0.2 mL) at -78
ïC. After being stirred for 30 min, the reaction was mixed with
MeOH (0.1 mL), 1 N NaOH (0.1 mL), and 30% H2O2 (0.1 mL).
The resulting mixture was allowed to warm to room temper-
ature and stirred for 30 min. Extraction with EtOAc, evapora-
tion of the solvent, and filtration of the crude material through
a short silica gel column provided the diastereomeric mixture
of 9 and 10 or 11 and 12, respectively.
6 (R1 ) i-P r , R2 ) P h , 80%, liqu id ): 1H NMR δ 7.46-7.43
(m, 2H), 7.30-7.22 (m, 3H), 3.73-3.69 (dd, J ) 11.5, 5.5 Hz,
1H), 3.62-3.58 (dd, J ) 11.5, 6.7 Hz, 1H), 3.07-3.03 (q, J )
5.9 Hz, 1H), 2.10-1.95 (m, 1H), 1.05 (d, J ) 6.6 Hz, 3H), 1.04
(d, J ) 6.6 Hz, 3H); 13C NMR δ 135.2, 131.7, 128.8, 126.8, 62.4,
60.1, 29.4, 20.3, 19.3.
6 (R1 ) i-P r , R2 ) Me, 67%, liqu id ): 1H NMR δ 3.76-3.72
(dd, J ) 11.2, 4.3 Hz, 1H), 3.55-3.50 (dd, J ) 11.2, 8.0 Hz,
1H), 2.50-2.45 (m, 1H), 2.08 (s, 3H), 1.95-1.86 (m, 1H), 1.03
(d, J ) 6.8 Hz, 6H); 13C NMR δ 61.7, 58.6, 29.5, 20.4, 19.9,
14.2.
6 (R1 ) t-Bu , R2 ) P h , 88%, liqu id ): 1H NMR δ 7.49-7.46
(m, 2H), 7.29-7.18 (m, 3H), 3.93-3.89 (dd, J ) 11.7, 4.2 Hz,
1H), 3.62-3.56 (dd, J ) 11.7, 8.5 Hz, 1H), 3.06-3.03 (dd, J )
8.5, 4.2 Hz, 1H), 2.35 (bs, 1H), 1.06 (s, 9H); 13C NMR δ 137.0,
131.4, 129.0, 126.7, 67.0, 61.7, 35.0, 28.1.
Gen er a l P r oced u r e for Na BH4 Red u ction of γ-Su lfen yl
En on es 7a a t -78 °C. To a solution of 7a (0.1 mmol) in MeOH
(1 mL) was added a solution of NaBH4 (0.1 mmol, 4 mg) in
MeOH (1 mL) at -78 ïC. The contents were stirred at this
temperature for 30 min. MeOH was removed, and the residue
was taken in Et2O, washed with saturated aqueous NH4Cl,
dried, and concentrated to furnish the mixture of alcohols 9
and 10.
6 (R1 ) t-Bu , R2 ) Me, 64%, liqu id ): 1H NMR δ 3.88-3.84
(dd, J ) 11.5, 4.2 Hz, 1H), 3.45-3.40 (dd, J ) 11.5, 9.3 Hz,
1H), 2.59 (bs, 1H), 2.42-2.38 (dd, J ) 9.3, 4.2 Hz, 1H), 2.18
(s, 3H), 1.03 (s, 9H); 13C NMR δ 65.5, 61.1, 34.8, 27.9, 17.9.
1
6 (R1 ) n -C6H13, R2 ) P h , 73% liqu id ): H NMR δ 7.45-
Gen er a l P r oced u r e for LiAlH 4 Red u ction of th e γ-Su l-
fen yl En on es 7g a t -78 °C. LiAlH4 (0.2 mmol, 8 mg) was
7.42 (m, 2H), 7.31-7.25 (m, 3H), 3.64-3.60 (dd, J ) 11.2, 4.6
Hz, 1H), 3.53-3.49 (dd, J ) 11.2, 6.3 Hz, 1H), 3.17-3.11
(quintet, J ) 6.0 Hz, 1H), 2.33 (bs, 1H), 1.67-1.28 (m, 10H),
0.88 (t, J ) 7.1 Hz, 3H); 13C NMR δ 133.5, 132.8, 128.9, 127.4,
63.7, 52.6, 31.6, 31.2, 29.0, 27.0, 22.5, 14.0.
ï
added to a solution of 7g (0.1 mmol) in Et2O (1 mL) at -78 C.
The contents were stirred at this temperature for 30 min.
EtOAc (2 mL) and water (2 drops) were added to destroy the
excess LiAlH4. It was then filtered and concentrated. The
residue, thus obtained, was filtered through a short silica gel
column to obtain the mixture of the corresponding alcohols 9
and 10.
6 (R1 ) n -C8H17, R2 ) P h , 71% liqu id ): 1H NMR δ 7.44-
7.41 (m, 2H), 7.29-7.21 (m, 3H), 3.63-3.59 (dd, J ) 11.5, 5.0
Hz, 1H), 3.53-3.49 (dd, J ) 11.5, 6.1 Hz, 1H), 3.16-3.10 (m,
1H), 2.47 (bs, 1H), 1.66-1.48 (m, 4H), 1.27 (bm, 10H), 0.88 (t,
J ) 6.8 Hz, 3H); 13C NMR δ 133.6, 132.6, 128.8, 127.2, 63.7,
52.4, 31.8, 31.2, 29.3, 29.1, 27.0, 22.6, 14.0.
Gen er a l P r oced u r e for th e Gr ign a r d Ad d ition to
γ-Su lfen yl En a ls 7c. Freshly prepared Grignard reagent (1
M solution in Et2O, 0.2 mmol) was added to a solution of
6 (R1 ) n -C8H17, R2 ) Me, 64%, liqu id ): 1H NMR δ 3.67-
3.63 (dd, J ) 11.2, 4.8 Hz, 1H), 3.52-3.47 (dd, J ) 11.2, 7.1
Hz, 1H), 2.69-2.63 (m, 1H), 2.37 (bs, 1H), 2.02 (s, 3H), 1.59-
1.34 (m, 4H), 1.28-1.27 (bm, 10H), 0.88 (t, J ) 6.8 Hz, 3H);
13C NMR δ 62.8, 49.9, 31.8, 30.7, 29.4, 29.2, 27.0, 22.6, 14.0,
11.8.
ï
γ-sulfenyl enal 7c (0.1 mmol) in THF (1 mL) at -78 C. After
being stirred for 2 h, the reaction mixture was diluted with
Et2O and washed with water. Evaporation of the solvent and
filtration of the residue through a short silica gel column
provided a mixture of 9 and 10.
2 (R1 ) Et). Identical with the one reported previously.20
1
6 (R1 ) C(CH2)4, R2 ) Me, 75%, liqu id ): H NMR δ 3.42
1
2 (R1 ) C(CH2)4, 80%, liqu id ): H NMR δ 7.54-7.52 (m,
(s, 2H), 2.63 (bs, 1H), 1.96 (s, 3H), 1.86-1.77 (m, 2H), 1.74-
1.61 (m, 6H); 13C NMR δ 65.3, 58.1, 35.3, 24.6, 11.1.
2H), 7.33-7.24 (m, 3H), 4.67 (s, 1H), 3.45 (s, 3H), 2.37 (bs,
1H), 1.95-1.56 (m, 8H); 13C NMR δ 135.8, 132.7, 129.1, 127.4,
101.3, 84.7, 57.5, 36.8, 24.4.
1
6 (R1 ) C(CH2)5, R2 ) Me, 77%, liqu id ): H NMR δ 3.38
(s, 2H), 2.59 (bs, 1H), 1.89 (s, 3H), 1.72-1.54 (m, 4H), 1.54-
1.25 (m, 6H); 13C NMR δ 66.7, 51.4, 32.0, 25.9, 21.3, 8.8.
6 (R 1 ) P h CH2CH2, R 2 ) Me, 67%, liq u id ): 1H NMR δ
7.27-7.14 (m, 5H), 3.62-3.58 (dd, J ) 11.5, 5.1 Hz, 1H), 3.53-
3.49 (dd, J ) 11.5, 6.8 Hz, 1H), 2.87-2.80 (m, 1H), 2.76-2.68
(m, 1H), 2.64-2.57 (m, 1H), 1.99 (s, 3H), 1.93-1.84 (m, 1H),
1.80-1.70 (m, 1H); 13C NMR δ 141.3, 128.22, 128.20, 125.7,
62.9, 48.7, 32.8, 32.0, 11.7.
1
2 (R1 ) C(CH2)5, 84%, liqu id ): H NMR δ 7.55-7.52 (m,
2H), 7.32-7.25 (m, 3H), 4.49 (s, 1H), 3.42 (s, 3H), 2.29 (bs,
1H), 1.73-1.54 (m, 10H); 13C NMR δ 136.1, 132.7, 129.1, 127.3,
104.1, 74.1, 57.7, 33.1, 32.7, 25.7, 21.7, 21.3.
2 (R1 ) P h CH2CH2-, 68%, liqu id ). Less polar diastere-
omer: 1H NMR δ 7.48-7.14 (m, 10H), 4.44 (d, J ) 6.8 Hz,
1H), 3.62-3.57 (m, 1H), 3.47 (s, 3H), 2.90-2.83 (m, 1H), 2.69-
2.60 (m, 1H), 2.09-2.01 (m, 1H). 1.87-1.78 (m, 1H); 13C NMR
δ 142.0, 133.8, 132.3, 129.0, 128.4, 128.3, 128.0, 125.7, 97.1,
71.3, 56.9, 34.4, 31.9. More polar diastereomer: 1H NMR δ
7.39-7.15 (m, 10H), 4.39 (d, J ) 7.3 Hz, 1H), 3.64-3.59 (m,
1
7a (R1 ) Et, R2 ) P h , R3 ) Me, 75%, liqu id ): H NMR δ
7.37-7.35 (m, 2H), 7.30-7.24 (m, 3H), 6.59-6.52 (dd, J ) 16.0,
9.4 Hz, 1H), 5.70 (d, J ) 16.0 Hz, 1H), 3.57-3.51 (dt, J ) 8.4,
7.6 Hz, 1H), 2.17 (s, 3H), 1.85-1.68 (m, 2H), 1.04 (t, J ) 7.4
Hz, 3H); 13C NMR δ 198.1, 146.3, 133.6, 133.1, 130.4, 128.8,
127.9, 52.9, 27.0, 26.7, 11.9. Anal. Calcd for C13H16OS: C,
70.87; H, 7.32. Found: C, 70.72 H, 7.24.
(20) Rawal, V. H.; Akiba, M.; Cava, M. P. Synth. Commun. 1984,
14, 1129.
J . Org. Chem, Vol. 69, No. 11, 2004 3871

Yadav et al.
1
8 (R1 ) Et, R2 ) P h , R3 ) Me): H NMR δ 7.83-7.81 (m,
7g (7; R1 ) R3 ) t-Bu , R2 ) Me, 78%, color less solid , m p
ï
2H), 7.69-7.65 (m, 1H), 7.61-7.52 (m, 2H), 6.51-6.44 (dd, J
) 16.1, 9.6 Hz, 1H), 5.96 (d, J ) 16.1 Hz, 1H), 3.60-3.54 (dt,
J ) 10.3, 3.4 Hz, 1H), 2.27-2.22 (m, 1H), 2.24 (s, 3H), 1.83-
1.72 (m, 1H), 0.96 (t, J ) 7.6 Hz, 3H); 13C NMR δ 196.9, 137.2,
137.0, 134.1, 129.1, 128.9, 128.1, 70.0, 27.3, 20.7, 11.2. Anal.
Calcd for C13H16O3S: C, 61.88; H, 6.39. Found: C, 61.69; H,
6.30.
53-55 C): 1H NMR δ 6.78-6.71 (dd, J ) 14.9, 11.0 Hz, 1H),
6.28 (d, J ) 14.9 Hz, 1H), 2.83 (d, J ) 11.0 Hz, 1H), 1.88 (s,
3H), 1.14 (s, 9H), 0.99 (s, 9H); 13C NMR δ 203.9, 143.0, 123.9,
62.0, 42.8, 34.2, 27.9, 26.2, 14.9. Anal. Calcd for C13H24OS: C,
68.37; H, 10.60. Found: 68.27; H, 10.47.
8 (R1 ) t-Bu , R2 ) R3 ) Me, color less solid , m p 62-63
ïC): 1H NMR δ 6.90-6.83 (dd, J ) 15.8, 11.0 Hz, 1H), 6.25 (d,
J ) 15.8 Hz, 1H), 3.45 (d, J ) 11.0 Hz, 1H), 2.82 (s, 3H), 2.36
(s, 3H), 1.23 (s, 9H); 13C NMR δ 197.0, 138.4, 137.0, 76.0, 41.9,
35.9, 28.8, 27.3; HRMS calcd m/z for C10H18O3S 218.0977,
found m/z 218.0960.
7a (R1 ) n -C6H13, R2 ) P h , R3 ) Me, 70%, color less solid ,
m p 50-52° C): 1H NMR δ 7.38-7.34 (m, 2H), 7.30-7.24 (m,
3H), 6.57-6.51 (dd, J ) 15.8, 9.4 Hz, 1H), 5.66 (d, J ) 15.8
Hz, 1H), 3.63-3.57 (m, 1H), 2.16 (s, 3H), 1.82-1.62 (m, 2H),
1.49-1.24 (m, 8H), 0.88 (t, J ) 6.8 Hz, 3H); 13C NMR δ 198.2,
146.6, 133.6, 133.2, 130.2, 128.8, 127.9, 51.3, 33.5, 31.5, 28.9,
27.2, 27.0, 22.5, 14.0. Anal. Calcd for C17H24OS: C, 73.86; H,
8.75. Found: C, 73.70; H, 8.64.
7a (R1 ) n -C8H17, R2 ) P h , R3 ) Me, 68%, color less solid ,
54-55 °C): 1H NMR δ 7.37-7.33 (m, 2H), 7.30-7.25 (m, 3H),
6.57-6.51 (dd, J ) 15.8, 9.5 Hz, 1H), 5.66 (d, J ) 15.6 Hz,
1H), 3.63-3.57 (dt, J ) 8.8, 6.4 Hz, 1H), 2.16 (s, 3H), 1.80-
1.62 (m, 2H), 1.47-1.39 (m, 2H), 1.37-1.27 (m, 10H), 0.88 (t,
J ) 6.7 Hz, 3H);. 13C NMR δ 198.2, 146.6, 133.7, 133.2, 130.2,
128.9, 127.9, 51.3, 33.5, 31.8, 29.3, 29.22, 29.15, 27.3, 27.0, 22.6,
14.1; HRMS calcd m/z for C19H28OS 304.1861, found m/z
304.1855.
7a (R1 ) n -Bu , R2 ) P h , R3 ) Me, 65%, liqu id ): 1H NMR
δ 7.36-7.33 (m, 2H), 7.29-7.23 (m, 3H), 6.57-6.51 (ddd, J )
15.9, 9.4, 0.9 Hz, 1H), 5.65 (d, J ) 15.9 Hz, 1H), 3.63-3.57
(dt, J ) 8.5, 6.8 Hz, 1H), 2.15 (s, 3H), 1.78-1.64 (m, 2H), 1.46-
1.29 (m, 4H), 0.90 (t, J ) 6.8 Hz, 3H); 13C NMR δ 197.9, 146.3,
133.5, 133.0, 130.0, 128.7, 127.7, 51.1, 33.0, 29.3, 26.8, 22.2,
13.7. Anal. Calcd for C15H20OS: C, 72.53; H, 8.12. Found: C,
72.40; H, 7.98.
7a (R1 ) n -Bu , R2 ) R3 ) Me, 68%, liqu id ): H NMR δ
1
6.45-6.38 (ddd, J ) 15.8, 9.5, 1.2 Hz, 1H), 5.86 (d, J ) 15.8
Hz, 1H), 3.08-3.02 (m, 1H), 2.21 (s, 3H), 1.88 (s, 3H), 1.65-
1.49 (m, 2H), 1.35-1.20 (m, 4H), 0.81 (t, J ) 7.1 Hz. 3H); 13
C
NMR δ 198.3, 146.7, 130.1, 48.5, 32.9, 29.3, 26.8, 22.2, 13.7.
Anal. Calcd for C10H18OS: C, 64.46; H, 9.74. Found: C, 64.34;
H, 9.64
7a (R1 ) i-P r , R2 ) P h , R3 ) Me, 79%, liqu id ): 1H NMR δ
7.36-7.32 (m, 2H), 7.29-7.22 (m, 3H), 6.63-6.56 (dd, J ) 15.9,
10.0 Hz, 1H), 5.63 (d, J ) 15.9 Hz, 1H), 3.44-3.40 (dd, J )
10, 6.7 Hz, 1H), 2.15 (s, 3H), 2.07-1.96 (m, 1H), 1.12 (d, J )
6.8 Hz, 3H), 1.04 (d, J ) 6.8 Hz, 3H); 13C NMR δ 198.0, 144.8,
133.7, 133.5, 130.7, 128.8, 127.7, 59.3, 31.9, 27.0, 20.6, 20.0.
Anal. Calcd for C14H18OS: C, 71.75; H, 7.74. Found: C, 71.60;
H, 7.65.
7a (R1 ) n -C8H17, R2 ) R3 ) Me, 71%, liqu id ): 1H NMR δ
6.45-6.39 (dd, J ) 15.9, 9.5 Hz, 1H), 5.88 (d, J ) 15.9 Hz,
1H), 3.09-3.03 (m, 1H), 2.21 (s, 3H), 1.89 (s, 3H), 1.62-1.52
(m, 2H), 1.34-1.29 (m, 1H), 1.23-1.20 (m, 11H), 0.81 (t, J )
6.8 Hz, 3H); 13C NMR δ 198.1, 146.7, 130.2, 48.5, 33.2, 31.7,
29.22, 29.15, 29.1, 27.2, 26.8, 22.5, 13.9, 13.7. Anal. Calcd for
7a (R1 ) i-P r , R2 ) R3 ) Me, 75%, liqu id ): 1H NMR δ
6.58-6.51 (dd, J ) 15.6, 10.3 Hz, 1H), 5.93 (d, J ) 15.6 Hz,
1H), 2.93-2.89 (dd, J ) 10.2, 7.0 Hz, 1H), 2.30 (s, 3H), 1.96
(s, 3H), 1.96-1.89 (m, 1H), 1.06 (d, J ) 6.7 Hz, 3H), 1.00 (d, J
) 6.7 Hz, 3H); 13C NMR δ 198.2, 145.1, 130.7, 56.6, 31.7, 26.9,
20.5, 20.1, 14.4. Anal. Calcd for C9H16OS: C, 62.74; H, 9.36.
Found: C, 62.60; H, 9.25.
C
14H26OS: C, 69.36; H, 10.81. Found: C, 69.22; H, 10.69.
7a (R1) C(CH2)4, R2 ) P h , R3 ) Me, 75%, liqu id ): 1H NMR
δ 7.38-7.26 (m, 5H), 6.90 (d, J ) 16.1 Hz, 1H), 5.51 (d, J )
16.1 Hz, 1H), 2.22 (s, 3H), 2.01-1.66 (m, 8H); 13C NMR δ 198.5,
149.9, 136.5, 132.0, 129.0, 128.5, 127.2, 60.6, 36.4, 27.1, 23.1;
HRMS calcd m/z for C15H18OS 246.1078, found m/z 246.1064.
7a (R1 ) C(CH2)4, R2 ) R3 ) Me, 78%, liqu id ): 1H NMR δ
6.78 (d, J ) 16.1 Hz, 1H), 5.89 (d, J ) 16.1 Hz, 1H), 2.30 (s,
3H), 1.92-1.82 (m, 6H), 1.87 (s, 3H), 1.73-1.67 (m, 2H); 13C
NMR δ 198.7, 149.4, 127.2, 55.9, 36.0, 26.8, 23.2, 12.3. Anal.
Calcd for C10H16OS: C, 65.17; H, 8.75. Found: C, 65.00; H,
8.64.
7a (R1 ) t-Bu , R2 ) P h , R3 ) Me, 80%, liqu id ): H NMR
1
δ 7.35-7.32 (m, 2H), 7.28-7.23 (m, 3H), 6.72-6.65 (dd, J )
15.6, 10.5 Hz, 1H), 5.48 (d, J ) 15.6 Hz, 1H), 3.31 (d, J ) 10.5
Hz, 1H), 2.14 (s, 3H), 1.11 (s, 9H); 13C NMR δ 198.0, 143.8,
134.1, 133.8, 130.2, 128.8, 127.8, 65.0, 34.5, 27.9, 27.0. Anal.
Calcd for C15H20OS: C, 72.53; H, 8.12. Found: 72.38; H, 8.00.
7b (R1 ) t-Bu , R2 ) P h , R3 ) OEt, 82%, liqu id ): 1H NMR
δ 7.36-7.34 (m, 2H), 7.29-7.23 (m, 3H), 6.93-6.87 (dd, J )
15.4, 10.7 Hz, 1H), 5.30 (d, J ) 15.4 Hz, 1H), 4.17-4.11 (m,
2H), 3.30 (d, J ) 10.5 Hz, 1H), 1.25 (t, J ) 7.2 Hz, 3H), 1.10
(s, 9H); 13C NMR δ 166.1, 145.2, 134.5, 133.6, 128.9, 127.6,
120.9, 64.6, 60.2, 34.6, 27.9, 14.2. Anal. Calcd for C16H22O2S:
C, 69.03; H, 7.97. Found: C, 68.93; H, 7.85.
7c (R1 ) t-Bu , R2 ) P h , R3 ) H, 76%, liqu id ): 1H NMR δ
9.47 (d, J ) 8.0 Hz, 1H), 7.35-7.32 (m, 2H), 7.30-7.25 (m,
3H), 6.79-6.72 (dd, J ) 15.4, 10.7 Hz, 1H), 5.57-5.51 (d, J )
15.4, 7.8 Hz, 1H), 3.44 (d, J ) 10.7 Hz, 1H), 1.13 (s, 9H); 13C
NMR δ 193.4, 153.8, 133.8, 131.7, 129.1, 128.1, 64.8, 34.5, 27.8.
Anal. Calcd for C14H18OS: C, 71.76; H, 7.75. Found: C, 71.67;
H, 7.64.
8 (R1 ) t-Bu , R2 ) P h , R3 ) Me, color less solid , m p 77-
78 ïC): 1H NMR δ 7.78-7.76 (m, 2H), 7.63-7.57 (m, 1H), 7.52-
7.49 (m, 2H), 6.72-6.65 (dd, J ) 16.1, 11.0 Hz, 1H), 5.48 (d, J
) 16.1 Hz, 1H), 3.44 (d, J ) 10.7 Hz, 1H), 2.16 (s, 3H), 1.28 (s,
9H); 13C NMR δ 196.8, 139.3, 137.7, 136.9, 133.8, 128.9, 128.5,
77.5, 36.1, 29.0, 27.0. Anal. Calcd for C15H20O3S: C, 64.26; H,
7.19. Found: C, 64.10; H, 7.06.
7a (R1 ) t-Bu , R2 ) R3 ) Me, 78%, liqu id ): 1H NMR δ
6.56-6.50 (dd, J ) 15.6, 10.7 Hz, 1H), 5.80 (d, J ) 15.6 Hz,
1H), 2.74 (d, J ) 10.5 Hz, 1H), 2.20 (s, 3H), 1.84 (s, 3H), 0.94
(s, 9H); 13C NMR δ 198.0, 143.9, 130.3, 61.8, 34.0, 27.7, 26.8,
14.7. Anal. Calcd for C10H18OS: C, 64.46; H, 9.74. Found: C,
64.30; H, 9.64.
7a (R 1 ) C(CH2)5, R 2 ) P h , R 3 ) Me, 71%, liq u id ): 1H
NMR δ 7.36-7.26 (m, 5H), 6.64 (d, J ) 16.4 Hz, 1H), 5.41 (d,
J ) 16.4 Hz, 1H), 2.20 (s, 3H), 1.85-1.70 (m, 7H), 1.55-1.36
(m, 3H); 13C NMR δ 198.5, 150.4, 137.6, 130.4, 129.3, 128.5,
127.6, 53.8, 35.0, 27.2, 25.7, 22.6. Anal. Calcd for C16H20OS:
C, 73.80; H, 7.74. Found: C, 73.65; H, 7.62.
1
7b (R1 ) C(CH2)5, R2 ) P h , R3 ) OMe, 77%, liqu id ): H
NMR δ 7.39-7.25 (m, 5H), 6.85 (d, J ) 16.1 Hz, 1H), 5.19 (d,
J ) 16.1 Hz, 1H), 4.21-4.15 (q, J ) 16.1 Hz, 2H), 1.84-1.69
(m, 6H), 1.51-1.37 (m, 4H), 1.28 (t, J ) 7.2 Hz, 3H); 13C NMR
δ 198.5, 150.4, 137.6, 130.4, 129.3, 128.5, 127.6, 53.8, 35.0, 27.2,
25.7, 22.6. Anal. Calcd for C17H22O2S: C, 70.31; H, 7.64.
Found: C, 70.16; H, 7.56.
7c (R1 ) C(CH2)5, R2 ) P h , R3 ) H, 67%, liqu id ): 1H NMR
δ 9.53 (d, J ) 7.6 Hz, 1H) 7.37-7.32 (m, 3H), 7.30-7.26 (m,
2H), 6.66 (d, J ) 15.9 Hz, 1H), 5.49-5.43 (dd, J ) 15.8, 7.8
Hz, 1H), 1.88-1.71 (m, 6H), 1.56-1.36 (m, 4H); 13C NMR δ
193.9, 160.6, 137.5, 129.9, 129.5, 129.3, 128.6, 53.9, 34.9, 25.6,
22.5. Anal. Calcd for C15H18OS: C, 73.14; H, 7.37. Found: C,
73.03; H, 7.27.
7a (R1 ) C(CH2)5, R2 ) R3 ) Me, 65%, liqu id ): 1H NMR δ
6.55 (d, J ) 16.3 Hz, 1H), 5.86 (d, J ) 16.3 Hz, 1H), 2.31 (s,
3H), 1.80 (s, 3H), 1.77-1.68 (m, 6H), 1.54-1.38 (m, 4H); 13C
3872 J . Org. Chem., Vol. 69, No. 11, 2004

π-Selectivity of γ-Sulfenyl Enones
NMR δ 198.9, 150.0, 127.3, 48.9, 34.2, 26.8, 25.7, 22.2, 10.3.
Anal. Calcd for C11H18OS: C, 66.62; H, 9.15. Found: C, 66.54;
H, 9.00.
1.87-1.81 (m), 1.31 (d, J ) 6.3 Hz, minor isomer), 1.30 (d, J
) 6.3 Hz, major isomer), 1.01 (d, J ) 6.6 Hz, minor isomer),
1.00 (d, J ) 6.8 Hz, major isomer), 0.98 (d, J ) 6.6 Hz, minor
isomer), 0.96 (d, J ) 6.8 Hz, major isomer); 13C NMR δ 136.2,
136.1, 128.9, 128.8, 68.5, 68.4, 56.8, 32.0, 29.7, 23.9, 23.8, 20.7,
19.9, 19.8, 14.4, 14.3. Anal. Calcd for C9H18OS: C, 62.02; H,
10.41. Found: C, 61.94; H, 10.31.
7a (R1 ) P h CH2CH2, R2 ) P h , R3 ) Me, 74%, liqu id ): 1H
NMR δ 7.34-7.16 (m, 10H), 6.60-6.53 (dd, J ) 15.8, 9.3 Hz,
1H), 5.65 (d, J ) 15.8 Hz, 1H), 3.62-3.56 (td, J ) 8.6, 7.6 Hz,
1H), 2.79 (t, J ) 7.6 Hz, 2H), 2.14 (s, 3H), 2.11-1.97 (m, 2H);
13C NMR δ 198.0, 146.0, 140.5, 133.7, 132.7, 130.3, 128.9,
128.5, 128.4, 128.0, 126.2, 50.3, 34.8, 33.1, 27.0. Anal. Calcd
for C19H20OS: C, 76.98; H, 6.80. Found: C, 76.85; H, 6.70.
7a (R1 ) P h CH2CH2, R2 ) R3 ) Me, 79%, liqu id ): 1H NMR
δ 7.30-7.26 (m, 2H), 7.20-7.15 (m, 3H), 6.54-6.48 (dd, J )
15.9, 9.5 Hz, 1H), 5.92 (d, J ) 15.8 Hz, 1H), 3.15-3.09 (td, J
) 9.0, 7.6 Hz, 1H), 2.73 (t, J ) 7.6 Hz, 2H), 2.27 (s, 3H), 2.03-
1.92 (m, 2H), 1.94 (s, 3H); 13C NMR δ 198.2, 146.1, 140.6, 130.3,
128.4, 128.3, 126.0, 47.5, 34.5, 33.1, 26.8, 13.5. Anal. Calcd
for C14H18OS: C, 71.75; H, 7.74. Found: C, 71.62; H, 7.63.
9 (R1 ) Et, R2 ) P h , R3 ) Me, less p ola r a lcoh ol, m a jor
isom er , liqu id ): 1H NMR δ 7.39-7.37 (m, 2H), 7.30-7.21 (m,
3H), 5.49-5.42 (dd, J ) 15.4, 9.1 Hz, 1H), 5.31-5.26 (dd, J )
15.4, 6.4 Hz, 1H), 4.19-4.12 (quintet, J ) 6.4 Hz, 1H), 3.52-
3.46 (dt, J ) 8.1, 6.4 Hz, 1H), 1.79-1.58 (m, 2H), 1.12 (d, J )
6.3 Hz, 3H), 1.0 (t, J ) 7.4 Hz, 3H); 13C NMR δ 135.9, 134.6,
133.5, 130.4, 128.6, 127.3, 68.1, 52.9, 27.4, 23.0, 11.9. Anal.
Calcd for C13H18OS: C, 70.22; H, 8.16. Found: C, 70.10; H,
8.05.
9 (R1 ) t-Bu , R2 ) P h , R3 ) Me, less p ola r a lcoh ol, m a jor
isom er , liqu id ): 1H NMR δ 7.36-7.33 (m, 2H), 7.26-7.18 (m,
3H), 5.55-5.49 (dd, J ) 15.1, 10.2 Hz, 1H), 5.06-5.01 (dd, J
) 15.1, 6.6 Hz, 1H), 4.10-4.04 (quintet, J ) 6.4 Hz, 1H), 3.28
(d, J ) 10.2 Hz, 1H), 1.04 (d, J ) 6.4 Hz, 3H), 1.03 (s, 9H); 13
C
NMR δ 136.0, 135.5, 134.0, 128.6, 128.4, 127.2, 68.2, 64.8, 34.4,
28.0, 23.0; HRMS calcd m/z for C15H22OS 250.1391, found m/z
250.1385.
10 (R1 ) t-Bu , R2 ) P h , R3 ) Me, m or e p ola r a lcoh ol,
m in or isom er , liqu id ): 1H NMR δ 7.34-7.32 (m, 2H), 7.26-
7.19 (m, 3H), 5.59-5.52 (dd, J ) 15.4, 10.2 Hz, 1H), 5.09-
5.04 (dd, J ) 15.4, 6.7 Hz, 1H), 4.14-4.07 (quintet, J ) 6.4
Hz, 1H), 3.27 (d, J ) 10.2 Hz, 1H), 1.06 (s, 9H), 0.99 (d, J )
6.3 Hz, 3H); 13C NMR δ 135.7, 135.4, 133.9, 128.6, 128.3, 127.1,
68.3, 64.9, 34.4, 28.0, 23.2; HRMS calcd m/z for C15H22OS
250.1391, found m/z 250.1382.
9 (R1 ) t-Bu , R2 ) R3 ) P h , less p ola r a lcoh ol, m a jor
1
isom er , liqu id ): H NMR δ 7.40-7.12 (m, 10H), 5.76-5.69
(ddd, J ) 15.1, 10.4, 1.1 Hz, 1H), 5.26-5.20 (dd, J ) 15.1, 6.4
Hz, 1H), 5.02 (d, J ) 6.6 Hz, 1H), 3.38 (d, J ) 10.5 Hz, 1H),
1.08 (s, 9H); 13C NMR δ 142.5, 135.4, 133.8, 130.1, 128.7, 128.3,
127.45, 127.42, 127.3, 126.1, 74.1, 64.6, 34.5, 28.0. Anal. Calcd
for C20H24OS: C, 76.88; H, 7.75. Found: C, 76.74; H, 7.66.
10 (R1 ) Et, R2 ) P h , R3 ) Me, m or e p ola r a lcoh ol,
m in or isom er , liqu id ): 1H NMR δ 7.38-7.36 (m, 2H), 7.29-
7.21 (m, 3H), 5.49-5.43 (dd, J ) 15.4, 9.0 Hz, 1H), 5.32-5.26
(dd, J ) 15.4, 6.6 Hz, 1H), 4.20-4.13 (quintet, J ) 6.4 Hz,
1H), 3.51-3.45 (dt, J ) 8.4, 6.0 Hz, 1H), 1.79-1.58 (m, 2H),
1.07 (d, J ) 6.4 Hz, 3H), 1.01 (t, J ) 7.6 Hz, 3H); 13C NMR δ
135.8, 134.5, 133.4, 130.4, 128.6, 127.2, 68.3, 53.0, 27.4, 23.2,
11.9. Anal. Calcd for C13H18OS: C, 70.22; H, 8.16. Found: C,
70.14; H, 8.08.
10 (R1 ) t-Bu , R2 ) R3 ) P h , m or e p ola r a lcoh ol, m in or
1
isom er , liqu id ): H NMR δ 7.28-7.08 (m, 10H), 5.77-5.71
(ddd, J ) 15.1, 10.2, 1.0 Hz, 1H), 5.29-5.23 (dd, J ) 15.1, 6.9
Hz, 1H), 5.05 (d, J ) 7.1 Hz, 1H), 3.32 (d, J ) 10.2 Hz, 1H),
1.10 (s, 9H); 13C NMR δ 142.7, 135.1, 133.7, 133.6, 130.3, 128.6,
128.3, 127.4, 127.1,126.1, 74.6, 64.5, 34.5, 28.1. Anal. Calcd
for C20H24OS: C, 76.88; H, 7.75. Found: C, 76.78; H, 7.64.
1
Mixtu r e of 11 a n d 12 (R1 ) Et, R2 ) P h , R3 ) Me): H
NMR δ 7.85-7.81 (m), 7.64-7.62 (m), 7.56-7.52 (m), 5.54-
5.40 (m), 4.28-4.22 (m), 3.44-3.37 (m), 2.20-2.11 (m), 1.74-
1.62 (m), 1.14 (d, J ) 6.6 Hz, major isomer), 1.12 (d, J ) 6.3
Hz, minor isomer), 0.94 (t, J ) 7.3 Hz); 13C NMR δ 143.6, 137.6,
133.6, 129.1, 128.8, 121.3, 121.1, 70.2, 67.7, 22.9, 20.5, 11.2;
HRMS calcd m/z for C13H18O3S 254.0977, found m/z 254.0970.
11 (R1 ) t-Bu , R2 ) P h , R3 ) Me, color less solid , m p 134
1
ïC): H NMR δ 7.82-7.80 (m, 2H), 7.61-7.57 (m, 1H), 7.53-
7.49 (m, 2H), 5.71-5.64 (ddd, J ) 15.1, 10.7, 1.2 Hz, 1H), 5.07-
5.02 (dd, J ) 15.4, 5.9 Hz, 1H), 4.15-4.08 (quintet, J ) 6.4
Hz, 1H), 3.33 (d, J ) 10.7 Hz, 1H), 1.24 (s, 9H), 1.00 (d, J )
6.4 Hz, 3H); 13C NMR δ 143.0, 140.2, 133.2, 128.7, 128.6, 121.5,
77.6, 67.6, 35.6, 29.0, 22.6; HRMS calcd m/z for C15H22O3S
282.1290, found m/z 282.1287.
Mixtu r e of a lcoh ols 9 a n d 10 (R1 ) n -Bu , R2 ) P h , R3
)
Me, liqu id ): 1H NMR δ 7.39-7.34 (m), 7.30-7.22 (m), 5.47-
5.41 (dd, J ) 15.4, 9.2 Hz), 5.27-5.22 (dd, J ) 15.4, 6.4 Hz),
4.17-4.10 (quintet, J ) 6.4 Hz), 3.58-3.51 (m), 1.73-1.55 (m),
1.46-1.25 (m), 1.00 (d, J ) 6.3 Hz, major isomer), 1.05 (d, J )
6.3 Hz, minor isomer), 0.89 (t, J ) 7.4 Hz); 13C NMR δ 135.6,
135.5, 134.6, 134.5, 133.5, 133.4, 130.6, 128.6, 127.3, 127.2,
68.2, 68.1, 51.4, 51.3, 33.9, 29.4, 23.1, 23.0, 22.4, 13.9. Anal.
Calcd for C15H22OS: C, 71.95; H, 8.86. Found: C, 71.80, H,
8.75.
Mixtu r e of 9 a n d 10 (R1 ) t-Bu , R2 ) R3 ) Me, liqu id ):
1H NMR δ 5.57-5.44 (m), 4.38-4.34 (m), 2.75 (d, J ) 10 Hz,
minor isomer), 2.74 (d, J ) 9.8 Hz, major isomer), 1.96 (s, major
isomer), 1.93 (s, minor isomer), 1.31 (d, J ) 6.4 Hz, minor
isomer), 1.30 (d, J ) 6.3 Hz, major isomer), 1.00 (s, minor
isomer), 0.99 (s, major isomer); 13C NMR δ 136.0, 135.9, 128.2,
128.1, 68.5, 68.4, 62.19, 62.15, 34.1, 27.9, 23.9, 23.8, 14.8, 14.7.
Anal. Calcd for C10H20OS: C, 63.77; H, 10.70. Found: C, 63.64;
H, 10.60.
Mixtu r e of 9 a n d 10 (R1 ) R3 ) t-Bu , R2 ) Me, liqu id ):
1H NMR δ 5.64-5.43 (m), 3.82 (d, J ) 6.8 Hz, minor isomer),
3.78 (d, J ) 7.0 Hz, major isomer), 2.78 (d, J ) 10.3 Hz, minor
isomer), 2.77 (d, J ) 9.8 Hz, major isomer), 1.98 (s, major
isomer), 1.97 (s, minor isomer), 1.01 (s, minor isomer), 1.00 (s,
minor isomer), 0.93 (s, minor isomer), 0.925 (s, major isomer);
13C NMR δ 131.7, 131.4, 131.1, 131.0, 80.8, 80.3, 62.6, 34.9,
34.2, 28.0, 25.8, 14.9. Anal. Calcd for C13H26OS: C, 67.78; H,
11.38. Found: C, 67.65; H, 11.24.
Mixtu r e of 11 a n d 12 (R1 ) t-Bu , R2 ) R3 ) Me, liqu id ):
1H NMR δ 5.93-5.78 (m), 4.46-4.39 (m), 3.31 (d, J ) 9.8 Hz,
minor isomer), 3.30 (d, J ) 9.8 Hz, major isomer), 2.84 (s, major
isomer), 2.81 (s, minor isomer), 1.32 (d, J ) 6.6 Hz), 1.20 (s,
minor isomer), 1.18 (s, major isomer); 13C NMR δ 143.1, 143.0,
122.6, 122.3, 76.43, 76.39, 67.9, 67.8, 41.60, 41.56, 35.3, 28.8,
23.3, 23.1. Anal. Calcd for C10H20O3S: C, 54.51; H, 9.15.
Found: C, 54.44; H, 9.06.
Mixtu r e of 9 a n d 10 (R 1 ) n -Bu , R2 ) R3 ) Me, liqu id ):
1H NMR δ 5.56-5.51 (dd, J ) 15.4, 5.9 Hz, major isomer),
5.55-5.50 (dd, J ) 15.4, 6.1 Hz, minor isomer), 5.45-5.39 (dd,
J ) 15.4, 9.2 Hz), 4.38-4.32 (quintet, J ) 6.1 Hz), 3.05-2.99
(dt, J ) 8.6, 6.3 Hz), 1.99 (s, major isomer), 1.97 (s, minor
isomer), 1.75-1.48 (m), 1.38-1.25 (m), 1.30 (d, J ) 6.4 Hz,
minor isomer), 1.29 (d, J ) 6.4 Hz, major isomer), 0.89 (t, J )
7.1 Hz); 13C NMR δ 135.4, 131.0, 130.8, 68.3, 48.8, 33.8, 29.5,
23.7, 22.4, 13.9, 13.8. Anal. Calcd for C10H20OS: C, 63.77; H,
10.70. Found: C, 63.70; H, 10.60.
Mixt u r e of 9 a n d 10 (R1 ) i-P r , R2 ) P h , R3 ) Me,
1
liqu id ): H NMR δ 7.39-7.34 (m), 7.29-7.20 (m), 5.51-5.45
(m), 5.24-5.19 (m), 4.15-4.10 (quintet, J ) 6.3 Hz), 3.43-
3.39 (m), 1.98-1.89 (m), 1.11-1.00 (overlapping doublets); 13
C
NMR δ 136.4, 136.3, 135.1, 133.5, 133.4, 128.7, 128.6, 127.2,
68.3, 68.2, 59.1, 32.1, 29.7, 23.2, 23.0, 20.7, 19.7. Anal. Calcd
for C14H20OS: C, 71.13; H, 8.53. Found: C, 71.00; H, 8.45.
Mixtu r e of 9 a n d 10 (R1 ) i-P r , R2 ) R3 ) Me, liqu id ):
1H NMR δ 5.55-5.43 (m), 4.38-4.32 (quintet, J ) 6.1 Hz),
2.86-2.82 (m), 1.98 (s, major isomer), 1.96 (s, minor isomer),
J . Org. Chem, Vol. 69, No. 11, 2004 3873

Yadav et al.
Mixtu r e of 9 a n d 10 (R1 ) n -C6H13, R2 ) P h , R3 ) Me,
16.0 Hz, 1H), 5.58-5.52 (quintet, J ) 6.6 Hz, 1H), 5.08-5.03
(dd, J ) 16.0, 5.6 Hz, 1H), 1.85-1.65 (m, 6H), 1.54-1.32 (m,
4H), 1.34-1.32 (dd, J ) 6.3, 1.1 Hz, 3H); 13C NMR δ 164.9,
137.7, 131.61, 131.55, 131.4, 131.1, 129.6, 128.6, 128.1, 127.8,
127.6, 71.8, 53.4, 35.74, 35.69, 25.9, 22.5, 20.53, 20.45.
The above material was oxidized with m-CPBA to furnish
the corresponding sulfone as a colorless solid: mp 124 °C; 1H
NMR δ 7.89-7.86 (m, 2H), 7.76-7.73 (m, 2H), 7.61-7.54 (m,
3H), 7.43-7.39 (m, 2H), 5.63-5.48 (m, 3H), 2.07-1.89 (m, 4H),
1.74-1.58 (m, 3H), 1.41 (d, J ) 6.1 Hz, 3H), 1.38-1.16 (m,
3H); 13C NMR δ 164.8, 137.1, 135.0, 133.4, 131.7, 131.1, 130.8,
129.1, 128.2, 128.1, 71.1, 67.7, 28.6, 28.4, 25.1, 21.5, 20.1;
ESMS [M + NH4] 494.2 and 496.2 (1:1).
1
liqu id ): H NMR δ 7.39-7.35 (m), 7.30-7.23 (m), 5.47-5.41
(ddd, J ) 15.4, 9.2, 1.0 Hz), 5.27-5.21 (dd, J ) 15.4, 7.1 Hz),
4.17-4.11 (m), 3.58-3.52 (m), 1.73-1.54 (m), 1.43-1.36 (m),
1.34-1.21 (m), 1.10 (d, J ) 6.4 Hz, major isomer), 1.05 (d, J )
6.4 Hz, minor isomer), 0.88 (t, J ) 7.1 Hz); 13C NMR δ 135.6,
135.5, 134.6, 133.6, 133.5, 130.8, 130.7, 128.6, 127.3, 127.2,
68.2, 68.1, 51.4, 34.2, 31.6, 28.9, 27.3, 23.2, 23.0, 22.6, 14.0.
Anal. Calcd for C17H26OS: C, 73.33; H, 9.41. Found: C, 73.20;
H, 9.33.
Mixtu r e of 9 a n d 10 (R1 ) n -C8H17, R2 ) P h , R3 ) Me,
1
liqu id ): H NMR δ 7.32-7.28 (m), 7.23-7.15 (m), 5.41-5.35
(dd, J ) 15.4, 9.3 Hz), 5.21-5.16 (dd, J ) 15.4, 6.4 Hz, minor
isomer), 5.20-5.15 (dd, J ) 15.4, 6.4 Hz, major isomer), 4.11-
4.04 (quintet, J ) 6.4 Hz), 3.51-3.45 (m), 1.65-1.47 (m), 1.37-
1.29 (m), 1.25-1.13 (m), 1.03 (d, J ) 6.4 Hz, major isomer),
0.99 (d, J ) 6.4 Hz, minor isomer), 0.81 (t, J ) 7.0 Hz); 13C
NMR δ 135.7, 134.6, 133.6, 133.5, 130.8, 128.6, 127.33, 127.25,
68.2, 51.4, 34.2, 31.8, 29.4, 29.3, 29.2, 27.3, 23.2, 23.0, 22.6,
14.1. Anal. Calcd for C19H30OS: C, 74.45; H, 9.87. Found: C,
74.35; H, 9. 78.
9 (R1 ) C(CH2)5, R2 ) R3 ) Me, liqu id ): 1H NMR δ 5.52-
5.40 (m, 2H), 4.40-4.34 (quintet, J ) 6.4 Hz, 1H), 1.83 (s, 3H),
1.71-1.60 (m, 7H), 1.51-1.36 (m, 3H), 1.31 (d, J ) 6.4 Hz,
3H); HRMS calcd m/z for C11H20OS 200.1235, found m/z
200.1230.
4-Br om ob en zoa t e of 9 (R 1 ) C(CH 2)5, R 2 ) R 3 ) Me,
1
liqu id ): H NMR δ 7.91 (d, J ) 6.8 Hz, 2H), 7.58 (d, J ) 6.8
Hz, 2H), 5.66-5.60 (m, 2H), 5.49-5.44 (dd, J ) 16.1, 6.3 Hz,
1H), 1.81 (s, 3H), 1.72-1.62 (m, 6H), 1.49-1.35 (m, 4H). 1.47
(d, J ) 6.4 Hz, 3H); 13C NMR δ 165.0, 137.2, 131.6, 131.1,
129.6, 127.9, 127.5, 72.0, 48.7, 35.1, 34.9, 26.0, 22.3, 20.9, 10.4.
Mixtu r e of 9 a n d 10 (R1 ) n -C8H17, R2 ) R3 ) Me,
liqu id ): 1H NMR δ 5.56-5.504 (dd, J ) 15.1, 6.1 Hz major
isomer), 5.55-5.495 (dd, J ) 15.1, 6.1 Hz, minor isomer), 5.45-
5.39 (dd, J ) 15.1, 9.0 Hz), 4.38-4.31 (quintet, J ) 6.2 Hz),
3.04-2.99 (dt, J ) 8.5, 6.2 Hz), 1.98 (s, major isomer), 1.96 (s,
minor isomer), 1.65-1.47 (m), 1.40-1.21 (m), 0.88 (t, J ) 7.1
Hz); 13C NMR δ 135.4, 135.3, 131.0, 130.9, 68.4, 68.3, 48.9,
48.8, 34.21, 34.15, 31.8, 29.4, 29.3, 29.2, 27.3, 23.8, 23.7, 22.6,
14.1, 13.8. Anal. Calcd for C14H28OS: C, 68.79; H, 11.55.
Found: C, 68.65; H, 11.47.
Mixtu r e of 9 a n d 10 (R1 ) P h CH2CH2, R2 ) P h , R3
)
Me, liqu id ): 1H NMR δ 7.36-7.17 (m), 5.52-5.46 (m), 5.29-
5.23 (m), 4.19-4.13 (m), 3.58-3.52 (m), 2.81-2.69 (m), 2.07-
1.88 (m), 1.12 (d, J ) 6.4 Hz, major isomer), 1.06 (d, J ) 6.4
Hz, minor isomer); 13C NMR δ 141.2, 136.1, 135.9, 134.2, 133.6,
133.5, 130.2, 128.63, 128.61, 128.49, 128.47, 128.4, 127.43,
127.36, 126.0, 68.2, 68.1, 50.5, 50.4, 35.6, 33.3, 23.1, 23.0. Anal.
Calcd for C19H22OS: C, 76.46; H, 7.43. Found: C, 76.32; H,
7.38.
1
9 (R1 ) C(CH2)4, R ) P h , R3 ) Me, liqu id ): H NMR δ
7.43-7.41 (m, 2H), 7.33-7.26 (m, 3H), 5.82 (d, J ) 15.6 Hz,
1H), 5.10-5.05 (dd, J ) 15.6 Hz, 6.8 Hz, 1H), 4.25-4.19
(quintet, J ) 6.4 Hz, 1H), 1.97-1.64 (m, 8H), 1.45 (bs, 1H),
1.16 (d, J ) 6.4 Hz, 3H); 13C NMR δ 136.5, 135.0, 133.4, 132.0,
128.5, 128.3, 68.7, 60.7, 37.4, 37.2, 23.2; HRMS calcd m/z for
Mixtu r e of a lcoh ols 9 a n d 10 (R 1 ) P h CH2CH2, R2 ) R3
) Me, liqu id ): 1H NMR δ 7.30-7.26 (m), 7.21-7.17 (m), 5.57-
5.42 (m), 4.39-4.33 (m), 3.06-3.00 (dt, J ) 8.0, 6.6 Hz), 2.75-
2.69 (m), 2.00-1.84 (m), 1.98 (s, major isomer), 1.96 (s, minor
isomer), 1.64 (bs), 1.30 (d, J ) 6.3 Hz); 13C NMR δ 141.4, 135.9,
135.8, 130.5, 130.3, 128.4, 125.9, 68.44, 68.36, 48.02, 47.95,
35.5, 33.3, 23.7, 23.6, 13.7. Anal. Calcd for C14H20OS: C, 71.14;
H, 8.52. Found: C, 71.05; H, 8.45.
C
15H20OS 248.1235, found m/z 248.1224.
4-Br om oben zoa te of 9 (R1) C(CH2)4, R2 ) P h , R3 ) Me,
1
liqu id ): H NMR δ 7.88 (d, J ) 5.0 Hz, 2H), 7.58 (d, J ) 5.0
Hz, 2H), 7.40-7.38 (m, 2H), 7.26-7.15 (m, 3H), 6.01-5.96 (dd,
J ) 15.6, 0.9 Hz, 1H), 5.74-5.51 (m, 1H), 5.16-5.10 (dd, J )
15.6, 6.8 Hz, 1H), 1.96-1.65 (m, 8H), 1.34 (d, J ) 6.6 Hz, 3H);.
13C NMR δ 164.9, 137.4, 136.5, 133.0, 131.6, 131.1, 129.6,
128.4, 128.3, 127.9, 127.1, 71.7, 60.6, 37.2, 37.1, 23.2, 20.5.
Aceta te of a lcoh ols 9 a n d 10 (R 1 ) P h CH2CH2, R2 ) R3
) Me, liqu id ): 1H NMR δ 7.30-7.26 (m), 7.21-7.16 (m), 5.55-
5.34 (m), 3.05-2.98 (m), 2.75-2.67 (m), 2.06 (s, minor isomer),
2.05 (s, major isomer), 1.98-1.81 (m), 1.95 (s), 1.34 (d, J ) 6.6
Hz); 13C NMR δ 170.3, 141.3, 132.5, 132.3, 131.2, 128.44,
128.36, 125.9, 70.4, 70.3, 47.9, 47.8, 35.42, 35.37, 33.3, 21.4,
20.7, 20.5, 13.6, 13.5.
1
9 (R1 ) C(CH2)4, R2 ) R3 ) Me, liqu id ): H NMR δ 5.72
(d, J ) 15.6 Hz, 1H), 5.49-5.43 (dd, J ) 15.6, 6.6 Hz, 1H),
4.39-4.32 (quintet, J ) 6.4 Hz, 1H), 1.89 (s, 3H), 1.87-1.63
(m, 8H), 1.30 (d, J ) 6.4 Hz, 3H); 13C NMR δ 134.2, 132.0,
68.7, 56.0, 37.0, 36.7, 23.9, 23.4, 12.3; HRMS calcd m/z for
Ack n ow led gm en t. We thank the Council of Scien-
tific & Industrial Research (CSIR), New Delhi, Govern-
ment of India, for support of this research. K.G.B.
acknowledges CSIR for the award of Senior Research
Fellowship.
C
10H18OS 186.1078, found m/z 186.1064.
1
Aceta te of 9 (R1 ) C(CH2)4, R2 ) R3 ) Me, liqu id ): H
NMR δ 5.75 (d, J ) 14.6 Hz, 1H), 5.42-5.36 (m, 2H), 2.04 (s,
3H), 1.87 (s, 3H), 1.87-1.61 (m, 8H), 1.33 (d, J ) 6.1 Hz, 3H);
13C NMR δ 171.8, 136.0, 127.5, 70.8, 36.9, 36.7, 29.7, 23.4, 21.4,
20.8, 12.3.
Su p p or t in g In for m a t ion Ava ila b le: The Crystallo-
graphic Information Files (CIF) for 4-bromobenzoate of the
sulfone derived from the alcohol 9 (R1 ) cy-C6H10, R2 ) Ph, R3
) Me) and the alcohol 11 (R1 ) t-Bu, R2 ) Ph, R3 ) Me) and
the coordinates of the optimized geometries of s-cis-8 and
s-trans-8 (R1 ) R3 ) Me, R2 ) Ph), s-cis-7d and s-trans-7d
(7a ; R1 ) Me, R2 ) Ph), s-cis-7e and s-trans-7e (7a ; R1 ) R2 )
Me), and s-cis-7c and s-trans-7c (R1 ) R2 ) Me). This material
is available free of charge via the Internet at http://pubs.acs.org.
1
9 (R1 ) C(CH2)5, R2 ) P h , R3 ) Me, liqu id ): H NMR δ
7.42-7.40 (m, 2H), 7.33-7.26 (m, 3H), 5.55 (d, J ) 15.9 Hz,
1H), 5.03-4.97 (dd, J ) 15.8, 6.8 Hz, 1H), 4.24-4.18 (quintet,
J ) 6.5 Hz, 1H), 1.81-1.68 (m, 6H), 1.50-1.37 (m, 4H), 1.15
(d, J ) 6.4 Hz, 3H); 13C NMR δ 137.7, 135.3, 132.6, 131.9,
128.7, 128.2, 68.9, 53.7, 36.02, 35.97, 25.9, 23.1, 22.6; HRMS
calcd m/z for C16H22OS 262.1391, found m/z 262.1376.
4-Br om oben zoa te of 9 (R1 ) C(CH2)5, R2 ) P h , R3 ) Me,
1
liqu id ): H NMR δ 7.88 (d, J ) 7.3 Hz, 2H), 7.58 (d, J ) 7.3
Hz, 2H), 7.39-7.37 (m, 2H), 7.26-7.15 (m, 3H), 5.72 (d, J )
J O034608C
3874 J . Org. Chem., Vol. 69, No. 11, 2004