Chemoselective samarium-mediated benzoyloxysulfone eliminations

Article abstract of DOI:10.1021/jo201734t

An investigation of the substrate dependence on the rate of samarium-mediated reductive elimination of Β-acyloxysulfones has provided insights into the mechanism of this transformation and allowed for the development of a chemoselective elimination process.

Full text of DOI:10.1021/jo201734t

ARTICLE
pubs.acs.org/joc
Chemoselective Samarium-Mediated Benzoyloxysulfone Eliminations
Erasmus O. Volz and Gregory W. O’Neil*
Department of Chemistry, Western Washington University, Bellingham, Washington 98225, United States
S Supporting Information
b
ABSTRACT: An investigation of the substrate dependence on the
rate of samarium-mediated reductive elimination of β-acyloxysulfones
has provided insights into the mechanism of this transformation and
allowed for the development of a chemoselective elimination process.
Scheme 2. Proposed Samarium Acetyloxysulfone
Elimination
’ INTRODUCTION
Nearly 40 years ago, Julia and Paris described a novel alkene
synthesis in which β-acyloxysulfones are reductively cleaved to
the corresponding predominantly trans-olefins.1 The method
was later significantly developed by Lythgoe and Kocienski and
has since been used extensively in organic synthesis, particu-
larly as a fragment coupling strategy.2 Classically, the reac-
tion is carried out in a three-step sequence by addition of an
α-metalated sulfone to an aldehyde or ketone, acylation with
acetic anhydride (Ac2O), and reductive elimination of the result-
ing acyloxysulfone with sodiumÀmercury amalgam (Na/Hg)
(Scheme 1).
Scheme 1. Classical Julia Olefination
Scheme 3. Proposed Samarium Benzoyloxysulfone
Elimination
More recently, samarium diiodide (SmI2) has been shown to
be capable of affecting reductive eliminations of this type.3 Keck
and co-workers reported that β-acetyloxysulfones will undergo
reductive elimination when treated with SmI2 in THF and
methanol at 25 °C for 1 h (Scheme 2).4 This reaction was
proposed to proceed in an analogous fashion to that originally
proposed for the Na/Hg-mediated process involving single-
electron transfer (SET) to the sulfone followed by radical
decomposition and elimination.
Similarly, Markꢀo and co-workers described an elimination of
β-benzoyloxysulfones using SmI2 in THF in the presence of an
additive such as HMPA or DMPU (Scheme 3).5 Unlike the
acetyloxysulfone elimination, the proposed mechanism involves
first transfer of an electron to the benzoyl group, followed by loss
of benzoate and elimination.
inert to these conditions (Scheme 4). Even after prolonged
reaction times at higher temperatures, only the starting benzoy-
loxysulfone was recovered. Instead, the corresponding alkene
product was obtained using sodiumÀmercury amalgam which is
now known to occur via a different mechanism proceeding
through the intermediate vinylsulfone 3.4
This paper describes a closer examination of the substrate
dependence on the rate of samarium-mediated elimination
Our own examination into the samarium-mediated reductive
elimination of benzoyloxysulfones6 revealed that the rate of
elimination is highly dependent on the substrate structure. For
example, while phenylbenzoyloxysulfone 1 rapidly eliminated at
À78 °C using SmI2 and DMPU, alkylbenzoyloxysulfone 2 was
Received: August 18, 2011
Published: September 04, 2011
r
2011 American Chemical Society
8428
dx.doi.org/10.1021/jo201734t J. Org. Chem. 2011, 76, 8428–8432
|

The Journal of Organic Chemistry
ARTICLE
Scheme 4. Differential Acyloxysulfone Reactivity
Table 1. Elimination Competition Experiments
entry
1
compds
conditionsa
a
% conversionb
6 + 7
6 = 100%
7 = 100%
6 = 100%
4 = 10%
6 = 100%
8 = 0%
2
3
4
5
6
7
6 + 4
6 + 8
7 + 4
7 + 8
4 + 8
9 + 10
a
a
a
a
a
b
Scheme 5. Benzylsulfone Samarium Elimination
7 = 100%
4 = 14%
7 = 100%
8 = 0%
4 = 12%
8 = 0%
9 = 70%
10 = 0%
reactions of β-acyloxysulfones. The results provide evidence that
both of the proposed mechanisms do operate, although at
substantially different rates. These insights have then allowed
for a chemoselective elimination process to be achieved.
a Key: (a) SmI2 (6 equiv), THF/DMPU (4:1), 0 °C, 60 min; (b) SmI2
(6 equiv), THF/DMPU (4:1), 22°C, 5 h. b Ratios determined by NMR.
Scheme 6. Allylic Benzoyloxysulfone Elimination
’ RESULTS AND DISCUSSION
The results in Scheme 4 indicate that substrates with an aryl
group adjacent to the benzoylester and an alkyl group adjacent
to the sulfone rapidly eliminate when treated with samarium
diiodide. Substitution of the aryl with an alkyl group as in
compound 2 causes the reaction to fail. To examine the
remaining aryl/alkyl combination, benzoyloxysulfone 4 was
prepared and treated with SmI2 in THF and DMPU (Scheme 5).
The eliminated product 5 was indeed obtained; however, the
reaction required 5 h at rt compared to 30 min at À78 °C for
compound 1.
Taken together, these results provide support for both of the
proposed samarium-mediated acyloxysulfone elimination me-
chanisms (see Schemes 2 and 3). A comparison of the elimina-
tion of compounds 1 and 2 provides further support for the
mechanism proposed by Markꢀo8 and suggests that the rate-
determining-step (RDS) involves carbon-radical formation post
SET into the benzoylcarbonyl which would be resonance stabi-
lized for compound 1. This is further supported by the results
from each competition experiment involving compound 7 along
with the successful elimination of allylic benzoate 11. Similarly,
placement of an aryl substituent adjacent to the phenylsulfone
does have an impact on the rate of elimination (entries 6 and 7,
Table 1) for both the benzoyloxy and acetoxy series. This data
provides strong evidence for Keck’s mechanism and suggests that
the RDS for this pathway involves carbon-radical formation upon
desulfonylation.
Importantly, the competition experiment between compounds 7
and 4 allows for a direct comparison of the rate of the two processes
themselves (entry 4, Table 1). The result demonstrates that while
both pathways do operate, the mechanism involving SET to the
benzoylester is faster (Scheme 7).9 If the resulting carbon radical
is too high in energy, however, the slower SET/sulfone pathway
then competes.10
A series of competition experiments were performed to
further test this differential reactivity as described in Table 1.
As can be seen from the results, those substrates with an aryl
group adjacent to the benzoyl ester (6 and 7) were completely
consumed when treated with SmI2 in THF/DMPU at 0 °C for
1 h (entries 1À5). Mixed alkyl/aryl compounds with the aryl
group adjacent to the sulfone (4) did eliminate under these
conditions, but only to the extent of ca. 10% (entries 2, 4,
and 6). Dialkyl substrate 8 remained completely intact in all
1
experiments as determined by H NMR (entries 3, 5, and 6).
Acetyloxysulfone substrates 9 and 10 displayed a similar sub-
strate rate dependence; however, only compound 9 with the
phenyl group adjacent to the sulfone gave any elimination
product even after prolonged reaction times at elevated tem-
peratures (entry 7).
This elimination profile is not limited to only to aryl-contain-
ing substrates. For instance, alkenyl benzoyloxysulfones of type
11 rapidly eliminate when treated with SmI2 in THF/DMPU
at À78 °C generating the corresponding all-trans triene as the
major product (Scheme 6).7
As a further demonstration of the substrate dependence
on the elimination mechanism, we set out to prepare a
8429
dx.doi.org/10.1021/jo201734t |J. Org. Chem. 2011, 76, 8428–8432

The Journal of Organic Chemistry
ARTICLE
Scheme 7. Relative Elimination Rates
’ EXPERIMENTAL SECTION
Competition Experiments (Table 1). To a 1:1 mixture of
acyloxysulfones (0.05 mmol/each) in THF (0.4 mL) and DMPU
(0.1 mL) at 0 °C was added SmI212 (0.1 M, 2.5 mL), and the mixture
was stirred for 1 h. The reaction was quenched with aq NH4Cl (15 mL)
and extracted with EtOAc (15 mL). The organic phase was dried over
MgSO4, filtered, and concentrated in vacuo. Ratios of starting material-
(s) and product(s) were determined by 1H NMR.
Benzoyloxysulfone 6. To a solution of benzyl phenyl sulfone
(300 mg, 1.29 mmol) in THF (6.5 mL) at À78 °C was added a solution
of n-BuLi (1.6 M, 0.97 mL), and the resulting mixture was stirred for
60 min. To the lithiated sulfone thus obtained was added benzaldehyde
(0.20 mL, 1.94 mmol), and the resulting mixture was stirred for 1 h.
Benzoyl chloride (0.30 mL, 2.58 mmol) was then added, and the mixture
was allowed to slowly warm to room temperature overnight. The reaction
was quenched with aq NH4Cl (15 mL) and extracted with EtOAc (2 Â
15 mL). The combined organic extracts were dried over MgSO4, filtered,
andconcentrated in vacuo. Purification by flash column chromatography
on silica (10:1, 4:1, 1:1 hexanes/ethyl acetate) afforded 6 (512 mg, 90%)
as 1.6:1 inseperable mixture of diastereomers: IR (ATR) 3012, 1721,
Scheme 8. Chemoselective Samarium-Mediated Elimination
1447, 1307, 1261, 1140, 1097, 1081, 1070, 1026, 757, 710, 687 cmÀ1
.
Signals for the mixture of diastereomers: 1H NMR (500 MHz, CDCl3) δ
8.12 (d, J = 7.3 Hz, 1H), 8.04 (d, J = 7.3, 2H), 7.95 (d, J = 7.0, 2H), 7.68
(d, J = 6.9 Hz, 2H), 7.43À7.64 (m, 8H), 7.22À7.41 (m, 12H), 7.05À
7.19 (m, 14 H), 6.89 (d, J = 10.3 Hz, 1H), 4.91 (d, J = 10.3 Hz, 1H), 4.45
(d, J = 3.7 Hz, 1H); 13C NMR (75 MHz, CDCl3) δ 165.0, 164.9, 139.5,
138.1, 137.3, 137.0, 133.7, 133.6, 133.3, 133.2, 133.1, 131.5, 130.5, 130.2,
130.1, 129.9, 129.8, 129.7, 129.6, 129.1, 129.0, 128.9, 128.8, 128.7, 128.6,
128.5, 128.4, 128.3, 128.2, 127.7, 126.6, 75.6, 75.1, 75.0, 72.5; HRMS
(ESI+) calcd for C27H22O4SNa (M + Na)+ 465.1131, found 465.1134.
Benzoylxysulfone 4. To a solution of benzyl sulfone (100 mg,
0.43 mmol) in THF (2.2 mL) at À78 °C was added a solution of n-BuLi
(1.6 M, 0.32 mL), and the resulting mixture was stirred for 20 min. To
the lithiated sulfone thus obtained was added hexanal (0.10 mL, 0.86
mmol), and the resulting mixture was stirred for 1 h. Benzoic anhydride
(292 mg, 1.29 mmol) and DMAP (158 mg, 1.29 mmol) were then
added, and the mixture was allowed to slowly warm to room temperature
overnight. The reaction was quenched with H2O (15 mL) and extracted
with MTBE (2 Â 15 mL). The combined organic extracts were dried
over MgSO4, filtered, and concentrated in vacuo. Purification by flash
column chromatography on silica (10:1, 4:1 hexanes/ethyl acetate)
afforded 4 (160 mg, 85%) as 1.7:1 inseperable mixture of diastereomers:
IR (ATR) 3063, 2956, 2929, 2860, 1720, 1692, 1602, 1584, 1449, 1317,
1269, 1177, 1147, 1107, 710 cmÀ1. Signals for the mixture of diaster-
eomers: 1H NMR (300 MHz, CDCl3) δ 8.05 (dd, J = 8.1, 1.2 Hz, 2H),
7.89 (td, J = 6.9, 1.8 Hz, 2H), 7.60À7.12 (m, 26H), 6.06 (m, 2H), 4.55
(d, J = 8.7 Hz, 1H), 4.24 (d, J = 3.9 Hz, 1H). 1.79À0.90 (m, 16H),
0.80À0.63 (m, 6H); 13C NMR (125 MHz, CDCl3) δ 165.8, 138.0,
134.0, 133.9, 133.8, 133.7, 133.3, 133.2, 131.5, 131.0, 130.9, 130.7, 130.4,
130.1, 129.3, 129.1, 129.0, 128.9, 128.8, 128.7, 128.6, 128.5, 128.4, 128.3,
74.8, 73.5, 72.5, 70.0, 69.3, 63.1, 35.0, 34.6, 32.5, 31.6, 31.5, 25.5, 24.3,
24.0, 22.7, 22.6, 22.5, 14.1, 14.0; HRMS (ESI+) calcd for C26H28O4SNa
(M + Na)+ 459.1601, found 459.1600.
compound that contained two different types of benzoylox-
ysulfones. To that end, cross-metathesis of alkenyl benzoy-
loxysulfone 12 with crotonaldehyde using Grubbs’ second-
generation catalyst (13)11 afforded aldehyde 14 that was
immediately treated with the lithium anion of methyl phenyl
sulfone (Scheme 8). Methyl phenyl sulfone was chosen to
limit the number of stereoisomers that would be produced
from the reaction. Acylation with benzoyl chloride (BzCl)
gave bis-benzoyloxysulfone 15, setting the stage for a che-
moselective samarium-mediated acyloxysulfone elimination
reaction. Specifically, reductive elimination of compound 15
would be expected to proceed by first selective debenzoyla-
tion to form the resonance-stabilized radical intermediate 16.
This would then decompose to give diene 17 containing an
intact benzoyloxysulfone. In the event, treatment of 15 with
samarium diiodide in a mixture of THF and DMPU at À78 °C
for 1 h cleanly afforded 17, thus confirming the substrate
dependence of the rate of samarium-mediated acyloxysulfone
reductive elimination.
’ CONCLUSION
The rate of samarium-mediated elimination of β-acyloxysul-
fones shows a clear substrate dependence as evidenced by a
series of competition experiments. These results indicate that
both of the proposed mechanisms are indeed operable, and it is
the substrate structure that determines by which mechanism
elimination occurs. Specifically, electron transfer to the sulfonyl
and/or benzoyl group is likely reversible and can occur into
both acceptor groups. The next step is fragmentation into a
carbon radical, and this is rate-determining. A difference in
carbon radical stabilities allowed for the chemoselective reduc-
tive-elimination of a bis-benzoyloxysulfone substrate. Efforts
are ongoing to design and implement additional permutations
of this general concept for the preparation of more complex
intermediates.
Acetyloxysulfone 9. To a solution of benzyl phenyl sulfone (198 mg,
0.85 mmol) in THF (4.3 mL) at À78 °C was added a solution of n-BuLi
(1.6 M, 0.80 mL), and the resulting mixture was stirred for 20 min. To the
lithiated sulfone thus obtained was added hexanal (0.20 mL, 1.71 mmol),
and the resulting mixture was stirred for 1 h. Acetic anhydride (261 mg,
2.56 mmol) and DMAP (312 mg, 2.56 mmol) were then added, and the
mixture was allowed to slowly warm to room temperature overnight.
The reaction was quenched with aq NH4Cl (15 mL) and extracted with
MTBE (2 Â 15 mL). The combined organic extracts were dried over
MgSO4, filtered, and concentrated in vacuo. Purification by flash column
8430
dx.doi.org/10.1021/jo201734t |J. Org. Chem. 2011, 76, 8428–8432

The Journal of Organic Chemistry
ARTICLE
chromatography on silica (4:1 hexanes:ethyl acetate) afforded 9 (340 mg,
and the mixture was allowed to slowly warm to room temperature
overnight. The reaction was quenched with aq NH4Cl (15 mL) and
extracted with EtOAc (2 Â 15 mL). The combined organic extracts were
dried over MgSO4, filtered, and concentrated in vacuo. Purification by
flash column chromatography on silica (10:1, 4:1, 1:1 hexanes/ethyl
acetate)afforded 15(176 mg, 61%) asaninseperablemixture ofdiastereo-
59%) as 2.6:1 inseperable mixture of diastereomers: IR (ATR) 2958, 2930,
2859, 1737, 1447, 1371, 1308, 1221, 1143, 1085, 1024, 755, 699 cmÀ1
.
Signals for the major diastereomer: 1H NMR (300 MHz, CDCl3)
δ 7.46À7.57 (m, 4H), 7.27À7.40 (m, 5H), 7.19À7.24 (m, 4H), 7.14
(dd, J = 7.3, 1.5 Hz, 2H), 5.88À5.94 (m, 2H), 4.42 (d, J = 9.2 Hz, 1H),
1.01À1.19, (m, 4H), 0.77À0.83 (m, 2H). Signals for the mixture of
diastereomers: 13C NMR (125 MHz, CDCl3) δ 170.3, 169.8, 151.5,
138.7, 138.2, 133.5, 133.3, 131.3, 130.9, 130.4, 129.9, 129.0, 128.9, 128.8,
128.7, 128.6, 128.5, 128.4, 128.3, 73.5, 73.2, 71.2, 69.8, 33.3, 32.4, 31.3,
24.8, 23.9, 22.4, 22.3, 21.2, 21.1, 13.9, 13.8; HRMS (ESI+) calcd for
C21H26O4SNa+ (M + Na)+ 397.1444, found 397.1463.
1
mers. Signals for the mixture of diastereomers: H NMR (300 MHz,
CDCl3) δ 8.12 (dd, J = 8.1, 1.1 Hz, 1H), 7.88 (ddd, J = 14.3, 7.0, 1.1 Hz,
8H), 7.70 (dd, J = 18.3, 8.1 Hz, 8H), 7.60À7.30 (m, 23H), 5.89À5.75
(m, 4H), 5.49, (dd, J = 15.4, 7.0 Hz, 2H), 4.57 (dd, J = 4.8, 2.6 Hz, 4H),
3.72 (dd, J = 8.8, 3.3 Hz, 1H), 3.69 (dd, J = 8.8, 2.9 Hz, 1H), 3.30À3.50,
(m, 4H), 1.74, (m, 4H), 1.63 (m, 4H), 1.55 (m, 4H); 13C NMR (125
MHz, CDCl3) δ 165.8, 164.8, 139.6, 138.4, 135.0, 134.9, 133.8, 133.7,
133.6, 133.4, 133.2, 130.2, 129.6, 129.3, 129.2, 129.0, 128.5, 128.3, 128.2,
128.0, 126.3, 69.4, 63.8, 61.2, 59.8, 31.7, 29.7, 25.7, 24.8; HRMS (ESI+)
calcd for C35H34O8S2 (M + H)+ 647.1773, found 647.1793.
Diene 17. To a solution of 15 (28 mg, 0.04 mmol) in 4:1 THF/
DMPU (0.34:0.08 mL) at À78 °C was added SmI2 (0.1 M, 1.30 mL),
and the resulting mixture was stirred for 30 min. The reaction was
quenched with aq NH4Cl (15 mL) and extracted with EtOAc (2 Â
15 mL). The combined organic extracts were dried over MgSO4, filtered,
and concentrated in vacuo. Purification by flash column chromatogra-
phy on silica (4:1, 1:1, hexanes/ethyl acetate) afforded 17 (31 mg, 76%):
IR (ATR) 2918, 2850, 1721, 1649, 1602, 1448, 1412, 1306, 1270, 1171,
1037, 1008, 831, 711 cmÀ1; 1H NMR (300 MHz, CDCl3) δ 7.90 (m, 2H),
7.69 (dd, J = 7.9, 0.8 Hz, 2H), 7.44À7.63 (m, 4H), 7.35 (t, J = 7.9 Hz,
2H), 6.25 (dt, J = 20.2, 10.1 Hz, 1H), 6.03 (dd, J = 15.8, 13.5 Hz, 1H),
5.60 (dt, J = 14.1, 6.6 Hz, 1H), 5.07 (d, J = 16.7 Hz, 2H), 4.97 (d, J = 10.1
Hz, 2H), 4.60 (d, J = 4.9 Hz, 2H), 3.41 (sextet, J = 4.4 Hz, 1H), 2.13
(m, 2H), 1.65 (m, 4H); 13C NMR (125 MHz, CDCl3) δ 165.8, 138.5,
136.9, 135.8, 133.7, 133.4, 133.3, 132.0, 130.2, 129.7, 129.3, 129.0, 128.8,
128.5, 128.3, 115.5, 63.9, 61.1, 32.1, 29.7, 29.6, 26.2, 24.8; HRMS (ESI+)
calcd for C22H24O4SNa (M + Na)+ 407.1288, found 407.1302.
Acetyloxysulfone 10. To a solution of 5-hexenyl phenyl sulfone13
(200 mg, 0.89 mmol) in THF (4.5 mL) at À78 °C was added a solution
of n-BuLi (1.6 M, 0.67 mL), and the resulting mixture was stirred for
30 min. To the lithiated sulfone thus obtained was added hexanal (0.16 mL,
1.34 mmol), and the resulting mixture was stirred for 1 h. Acetyl chloride
(0.126 mL, 1.78 mmol) was then added, and the mixture was allowed to
slowly warm to room temperature overnight. The reaction was quenched
with aq sodium bicarbonate (15 mL) and extracted with EtOAc (2 Â
15 mL). The combined organic extracts were dried over MgSO4, filtered,
and concentrated in vacuo. Purification by flash column chromatogra-
phy on silica (4:1 hexanes/ethyl acetate) afforded 10 (204 mg, 63%) as
1.2:1 inseperable mixture of diastereomers: IR (ATR) 2929, 2860, 1739,
1447, 1288, 1232, 1144, 1084, 1024, 998, 911, 753, 728, 699 cmÀ1. Signals
for the mixture of diastereomers: 1H NMR (500 MHz, CDCl3) δ 7.91
(m, 4H), 7.68 (q, J = 8.4 Hz, 2H), 7.60 (q, J = 7.7 Hz, 2H), 7.59 (q, J = 7.4
Hz, 2H), 5.71 (m, 2H), 4.97 (m, 4H), 4.12 (m, 1H), 4.05 (m, 1H), 3.09
(m, 2H), 1.14À2.20 (m, 34H), 0.89 (t, J = 7.0 Hz, 3H), 0.85 (t, J = 7.0
Hz, 3H); 13C NMR (125 MHz, CDCl3) δ 170.2, 170.0, 139.2, 139.1,
138.9, 138.5, 138.0, 137.7, 137.6, 137.5, 134.0, 133.8, 133.6, 129.4, 129.2,
129.1, 129.0, 128.6, 128.0, 115.4, 70.4, 70.1, 69.3, 68.8, 68.3, 66.6, 65.9,
56.1, 34.2, 34.0, 33.5, 33.4, 33.3, 33.0, 32.3, 31.6, 31.4, 31.3, 31.2, 31.1,
29.7, 29.6, 28.3, 27.9, 27.4, 26.8, 26.6, 25.6, 25.5, 25.4, 25.3, 25.2, 23.5,
22.6, 22.5, 22.4, 22.1, 22.0, 20.8, 14.0, 13.9; HRMS (ESI+) calcd for
C20H30O4SNa+ (M + Na)+ 389.1757, found 389.1789.
Hydroxysulfone 12. To a solution of 5-hexenyl phenyl sulfone
(133 mg, 0.59 mmol) in THF (3.0 mL) at À78 °C was added a solution
of n-BuLi (1.6 M, 0.71 mL), and the resulting mixture was stirred for
30 min. To the lithiated sulfone thus obtained was added paraformalde-
hyde (89 mg, 2.96 mmol), and the mixture was allowed to slowly warm
to room temperature for 15 h. The reaction was quenched with aq
NH4Cl (20 mL) and extracted with MTBE (2 Â 20 mL). The combined
organic extracts were dried over MgSO4, filtered, and concentrated in
vacuo. Purification by flash column chromatography on silica (4:1 hexanes/
ethyl acetate) afforded 12 (151 mg, 76%) as an oil: IR (ATR) 3327,
2928, 2856, 1628, 1447, 1211, 1157, 1085, 1024, 728 cmÀ1; 1H NMR
(300 MHz, CDCl3) δ 7.90 (m, 2H), 7.70 (m, 1H), 7.61 (m, 2H), 5.69
(ddt, J = 13.5, 10.5, 6.6 Hz, 1H), 4.95 (m, 1H), 4.93 (m, 1H), 3.92 (d, J =
2.7 Hz, 2H), 3.10 (m, 1H), 2.02 (m, 2H), 1.76 (m, 1H), 1.68À1.50
(m, 2H), 1.38 (m, 1H); 13C NMR (75 MHz, CDCl3) δ 137.3, 137.2,
134.1, 129.3, 128.8, 115.4, 65.9, 59.2, 33.2, 25.7, 24.0; HRMS (ESI+)
calcd for C13H19O3S (M + H)+ 255.1077, found 255.1097.
’ ASSOCIATED CONTENT
1
Supporting Information. Copies of H and 13C NMR
S
b
spectra for new compounds 4, 6, 9, 10, 12, 15, and 17.
This material is available free of charge via the Internet at http://
pubs.acs.org
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: oneil@chem.wwu.edu.
’ ACKNOWLEDGMENT
Financial support from Western Washington University, M. J.
Murdock Charitable Trust and Research Corporation depart-
mental development grant, and the Petroleum Research Fund
administered by the American Chemical Society (49499-UNI) is
gratefully acknowledged.
Bisbenzoyloxysulfone 15. To a solution of 12 (115 mg,
0.45 mmol) andcrotonaldehyde (316mg, 4.5 mmol) intoluene(2.3 mL)
was added catalyst 13 (19 mg, 0.02 mmol), and the mixture was warmed
to 60 °C for 10 h. The reaction was cooled to room temperature and flushed
through a plug of silica with EtOAc, and volatiles were removed in vacuo.
The crude aldehyde 14 was used immediately in the next reaction.
To a solution of MeSO2Ph (176 mg, 1.13 mmol) in THF (4.4 mL)
at À78 °C was added a solution of n-BuLi (1.6 M, 0.71 mL), and the
resulting mixture was stirred for 20 min. To the lithiated sulfone thus
obtained was added 14 obtained above, and the resulting mixture was
stirred for 3 h. Benzoyl chloride (0.15 mL, 1.35 mmol) was then added,
’ REFERENCES
(1) Julia, M.; Paris, J. M. Tetrahedron Lett. 1973, 14, 4833.
(2) (a) Kocienski, P. J.; Lythgoe, B.; Ruston, S. J. Chem. Soc.
1978, 829. (b) Kocienski, P. J.; Lythgoe, B.; Waterhouse, I. J. Chem.
Soc. 1980, 1045.(c) Takeshi, T. The Julia Reaction. In Modern Carbonyl
Olefination; Dumeunier, R., Markoꢀ, I. E., Eds.; Wiley-VCH: Weinheim,
2004. (d) Blakemore, P. R. J. Chem. Soc., Perkin Trans. 1 2002, 23, 2563.
(3) (a) de Pouilly, P.; Chenede, A.; Mallet, J.-M.; Sinay, P. Tetrahedron
Lett. 1992, 33, 8065. (b) Hojo, M.; Harada, H.; Yoshizawa, J.; Hosomi,
A. J . Org. Chem. 1993, 58, 6541. (c) Kunzer, H.; Stahnke, M.; Sauer, G.;
8431
dx.doi.org/10.1021/jo201734t |J. Org. Chem. 2011, 76, 8428–8432

The Journal of Organic Chemistry
ARTICLE
Wiechert, R. Tetrahedron Lett. 1991, 32, 1949. (d) Ihara, M.; Suzuki, S.;
Taniguchi, T.; Tokunaga, Y.; Fukumoto, K. Synlett 1994, 859.
(4) Keck, G. E.; Savin, K. A.; Weglarz, M. A. J. Org. Chem. 1995,
60, 3194.
(5) (a) Marko, I. E.; Murphy, F.; Dolan, S. Tetrahedron Lett. 1996,
37, 2089. (b) Marko, I. E.; Murphy, F.; Kumps, L.; Ates, A.; Touillaux, R.;
Craig, D.; Carballares, S.; Dolan, S. Tetrahedron 2001, 57, 2609.
(6) O’Neil, G. W.; Moser, D. J.; Volz, E. O. Tetrahedron Lett. 2009,
50, 7355.
(7) Carter, K. P.; Moser, D. J.; Storvick, J. M.; O’Neil, G. W.
Tetrahedron Lett. 2011, 52, 4494.
(8) For a recent report of benzoylesters as radical precursors, see:
Markꢀo, I. E.; Lam, K. Org. Lett. 2008, 10, 2773.
(9) (a) Wagenknecht, J. H.; Goodin, R.; Kinlen, P.; Woodard, F. E.
J. Electrochem. Soc. 1984, 131, 1559. (b) Webster, R. D.; Bond, A. M.
J. Org. Chem. 1997, 62, 1779.
(10) For a recent example of sulfone single-electron transfer, see:
Prakash, G. K. S.; Hu, J.; Olah, G. A. J. Org. Chem. 2003, 68, 4457.
(11) Trnka, T. M.; Grubbs, R. H. Acc. Chem. Res. 2001, 34, 18.
(12) Beemelmanns, C.; Reissig, H.-U. Angew. Chem., Int. Ed. 2010,
49, 8021–8025.
(13) Yang, H.; Carter, R. G. Org. Lett. 2010, 12, 3108.
8432
dx.doi.org/10.1021/jo201734t |J. Org. Chem. 2011, 76, 8428–8432