Zinc homologation-elimination reaction of α-sulfinyl carbanions as a new route to olefins

Article abstract of DOI:10.1002/ejoc.200800529

α-Lithiosulfinyl carbanions react either intermolecularly, after transmetalation into an organocopper derivative in an S_N2-type process, with zinc carbenoids, or intramolecularly by higher-order zincates through a tandem zinc homologation-β-elimination reaction into the corresponding alkenes. α,α- and α,β-Disubstituted alkenes can also be produced through these two methodologies. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejoc.200800529

FULL PAPER
DOI: 10.1002/ejoc.200800529
Zinc Homologation–Elimination Reaction of α-Sulfinyl Carbanions as a New
Route to Olefins
Adi Abramovitch[a] and Ilan Marek*[a]
Keywords: Zinc / Carbenoids / Sulfur / Carbanions / Alkenes / Elimination / Rearrangement
α-Lithiosulfinyl carbanions react either intermolecularly, af-
ter transmetalation into an organocopper derivative in an
SN2-type process, with zinc carbenoids, or intramolecularly
by higher-order zincates through a tandem zinc homologa-
tion–β-elimination reaction into the corresponding alkenes.
α,α- and α,β-Disubstituted alkenes can also be produced
through these two methodologies.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
tremely challenging all-carbon quaternary stereocenters.[3]
In such reaction, three new carbon–carbon bonds are cre-
Introduction
Enantiomerically pure sulfoxide moieties are very efficient ated in a single-pot operation from common starting mate-
chiral auxiliaries that are inducing important asymmetric rials.[4] However, in most of the applications, sulfoxides are
transformations. Therefore, the past decades have witnessed the only chiral synthetic tools and must be disposed of at
an exponential use of these chiral auxiliaries in asymmetric the end of the sequence. In this context, we[5] and others[6,7]
synthesis, establishing the chiral sulfinyl group as one of have recently reported the easy transformation of vinyl sulf-
the most efficient and versatile chiral controllers in carbon– oxides into organometallic species. This was found to be
carbon formations.[1] In this context, we recently reported synthetically very interesting, as further functionalization
that the chiral sulfinyl group plays multiple roles in asym- easily increases the complexity of the carbon skeleton. In
metric nucleophilic allylations[2] as chelating elements to contrast, the thermal syn-β-elimination reaction between a
slow down the metalotropic equilibrium, as activators and hydrogen and a sulfoxide is a well-known process and has
regiocontrol elements for the carbometalation reaction of been found to be a powerful route to chiral alkenes.[8] Simi-
the alkynyl moiety, as well as a chiral auxiliary for the cre- larly, the reduction of sulfoxides[9] as well as the β-elimi-
ation of two new stereogenic centers, including the ex- nation reaction of sulfinyl radicals (estimated to be very fast
Scheme 1. Combined carbometalation–zinc homologation–syn-elimination sequence.
[a] The Mallat Family Laboratory of Organic Chemistry, Schulich
process, ca 109 s–1) for aryl sulfoxide borne by a Csp3 cen-
Faculty of Chemistry and the Lise Meitner-Minerva Center for
ter[10] or a Csp2 center[11] was recently used in synthesis.
Computational Quantum Chemistry, Technion-Israel Institute
Following the pioneering work of Posner,[12] we were re-
of Technology,
Haifa, 32000 Israel
cently interested in the formation of enantioenriched allene
by the in situ combination of a carbometalation reaction
Fax: +972-4-829-3709
E-mail: chilanm@tx.technion.ac.il
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Zinc Homologation–Elimination Reaction of α-Sulfinyl Carbanions
zinc homologation followed by a β-elimination reaction as Table 1. Preparation of 1-alkenes from α-sulfinyl copper and zinc
described in Scheme 1.[13] Although the enantioselectivity
carbenoid species.
Entry[a]
R
Yield [%][b] (product)
of the reaction was only moderate, it implies an interesting
“deracemization” of the sp3 organometallic species before
the β-elimination reaction.
1 (1a)
2 (1b)
n-C11H23
Ph(CH2)2
Ph
pTol
pMeOC6H4
77 (5a)
70 (5b)
50 (5c)
65 (5d)
67 (5e)
The question of the fate of sp3 α-sulfinyl carbanions for 3 (1c)
4 (1d)
5 (1e)
the tandem zinc homologation followed by β-elimination
reactions as a new source of olefins was logically raised
[a] See experimental part. [b] Isolated yield after column
chromatography.
(Scheme 2).
(DMSO) can also be used in this reaction as a source of
terminal olefins as described in Scheme 4. In such a case,
dimsyl copper 6 (obtained after metalation and transmet-
alation of DMSO) was treated with the in situ prepared
secondary zinc carbenoid 3b (formed by treatment of 1,1-
bisiodoalkane[20] with Bu2Zn, 2 LiBr)[21] to give the zinc
homologated product 7, which spontaneously undergoes a
β-elimination reaction to lead to the corresponding allyl-
benzene 5f in 70% isolated yield. This particular example
illustrates the mild experimental condition used for this
transformation, as no conjugated alkene (β-methyl styrene)
was detected.
The first step, namely the metalation followed by the
transmetalation reactions into the organocopper species oc-
curs quantitatively to provide the corresponding dimsyl
copper species 6 in quantitative yield as originally described
in Scheme 4. Then, Bu2Zn and RCHI2 are all added to the
reaction mixture at –20 °C. As the transmetalation from
alkylcopper to alkylzinc is a slow process at –20 °C, the re-
action between R2Zn and RCHI2 occurs first to lead to the
in situ formation of the secondary zinc carbenoid 3b.[21]
This carbenoid readily homologates alkylcopper 6 (al-
though not demonstrated, it may be through a SN2-type
mechanism)[22] into species 7, which undergoes spontaneous
β-elimination to give the expected alkene in good yield
(intermolecular processes, Scheme 5). The β-elimination
could proceed either by a syn or anti process.
Scheme 2. α-Sulfinyl carbanions as a new source of alkenes.
The transformation of alkyl sulfones into olefins is a
well-known reaction,[14] and it has been successfully used in
natural product syntheses[15] but usually requires unstable
lithium or magnesium carbenoids (generated at low tem-
perature).[16] The use of thermally stable zinc carbenoids[17]
combined with the well-known and rich chemistry of sulf-
oxides led us to examine this reaction in detail. Moreover,
the in situ formation of zinc sulfenates (leaving group) may
find interesting synthetic applications.[18]
Results and Discussion
Our first experiments were performed by treatment of
alkyl sulfoxides 1a,e with one equivalent of LDA at low
temperature, followed by a transmetalation reaction to give
the corresponding α-sulfinyl copper species 2a–e. Then, by
addition of zinc carbenoid 3a, easily prepared by the ad-
dition of Et2Zn (1 equiv.) to CH2I2 (2 equiv.),[19] the inter-
molecular zinc homologated adducts 4a–e are in situ
formed, followed by a β-elimination reaction to give mono-
substituted olefins 5a–e in good overall yields as described
in Scheme 3 and Table 1.
Although this reaction proceeds nicely, an excess amount
of zinc carbenoid (classically 3 equiv.) was needed to reach
good chemical yields. Therefore, to improve our methodol-
ogy and to only use stoichiometric amounts of reagents, we
decided to investigate the intramolecular reaction between
α-sulfinyllithium derivatives and zinc carbenoid by a 1,2-
zincate
rearrangement
(intramolecular
processes,
Scheme 5).[23] In such an intramolecular rearrangement, the
organolithium species reacts with the zinc atom to form
first a zincate species and then, one of the ligands on the
zinc migrates to the carbon center bearing the leaving group
Scheme 3. General route to the preparation of terminal olefins.
As can be seen from analysis of Table 1, alkyl sulfoxides to lead to the rearranged product.[24]
1a (R = n-C11H23) and 1b [R = Ph(CH2)2] lead to the corre-
Accordingly, dodecyl p-tolyl sulfoxide (1a) was first met-
sponding alkenes 5a and 5b in good isolated yields (Table 1, alated with LDA and then added to bis(iodomethyl)zinc
entries 1 and 2, respectively). When benzyl sulfoxide 1c (R carbenoid 3a, in a 1 to 1 ratio, to form the corresponding
= Ph) was used as starting material, styrene 5c was obtained zincate 8. However, even after a few hours at room tempera-
only in moderate yield (Table 1, entry 3) due to the volatile ture, no rearrangement was observed (path A, Scheme 6).
nature of the final product. Various substituted styrenyl de- Either zincate 8 is not reactive enough to undergo the ex-
rivatives were also prepared in good yields by this simple pected 1,2-metalate rearrangement or the in situ generated
strategy (Table 1, entries 4 and 5). Dimethyl sulfoxide HN(iPr)2 protonates organozincate 8 (two possible different
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A. Abramovitch, I. Marek
FULL PAPER
Scheme 4. DMSO as a source of alkene.
Scheme 5. Two possible mechanistic pathways.
carbon–carbon bonds can be protonated). Therefore, to
solve these potential problems, once the alkyl sulfoxide was
deprotonated to give the α-sulfinyl carbanion and
HN(iPr)2, one more equivalent of nBuLi was added to re-
generate LDA (path B, Scheme 6). Then, zinc carbenoid 3a
was added to the reaction mixture and after 1 h at room
temperature, we were pleased to observe the formation of
alkene 5a in 70% isolated yield as described in Scheme 6,
path B. Following this positive result, we wanted to further
underline the effect of regenerated LDA, and more pre-
cisely, to see if the formally higher-order zincate 9 (we use
the term higher-order zincate when four groups are for-
mally attached to the zinc atom)[25] was necessary to pro-
mote the rearrangement. Although alternative mechanisms
could be proposed, such as the SN2 substitution on the car-
bon–iodine bond of the zincate generated from LDA and
zinc carbenoid 3a, we proposed that the formation of
higher-order zincate should be faster.[26] As we have already
reported that higher-order nucleophilic species are needed
to perform anionic rearrangements,[27] we tested this hy-
pothesis by performing the same experiment with MeLi as
deprotonating agent. When sulfoxide 1a was metalated with
MeLi, the corresponding α-sulfinyl carbanion was obtained
and after addition of zinc carbenoid 3a at –70 °C, interme-
diate zincate 8 was obtained (path C, Scheme 6). However,
even after a few hours at room temperature, neither homol-
ogated nor alkene species was detected (Path C, Scheme 6).
Scheme 6. 1,2-Metalate rearrangement.
Scheme 7. Mechanistic hypothesis for 1,2-zincate rearrangement.
Therefore, the 1,2-zincate rearrangement occurs only material and zinc carbenoid) led to identical yields as com-
when a higher-order zincate is formed as a reactive interme- pared to the one described previously (Scheme 3 and
diate (similarly to the 1,2-cuprate rearrangement, where an Table 1, intermolecular homologation, where the sulfoxide/
extra anionic charge is needed on the metal to promote the zinc carbenoid ratio was 1:3).[28] Then, we turned our atten-
reaction)[17b,27] as described in Scheme 7. Interestingly, the tion to the preparation of 1,1-disubstituted olefins by reac-
added negative charge on the zinc atom by addition of LiN- tion of secondary alkyl sulfoxides 10a,d and zinc carbenoid
(iPr)2 plays also the role of a dummy ligand (nontransfera- 3a. Our first attempt was performed by the intermolecular
ble group).
homologation reaction. However, this olefination reaction
This new 1,2-metalate rearrangement was generalized to does not proceed in satisfactory yield when tertiary α-sulf-
different primary alkyl sulfoxide derivatives (Table 2) and inyl organocopper is used (only 30% yield of the final 1,1-
this improved procedure (with a 1:1 ratio between starting disubstituted olefin was obtained).
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Zinc Homologation–Elimination Reaction of α-Sulfinyl Carbanions
Table 2. Preparation of 1-alkenes by 1,2-metalate rearrangement.
By using the conditions developed for the intramolecular
1,2-zincate rearrangement, α,α-disubstituted olefins 11 were
obtained in good overall yields in an easy and straightfor-
ward manner from the corresponding tertiary α-sulfinyllith-
ium species. It should be emphasized that the reaction does
not require an excess of reagents and that the mild condi-
tions used for this transformation leads to sensitive noncon-
jugated dienes such as 11b and 11d.
Entry[a]
R
Yield [%][b] (product)
1 (1a)
2 (1b)
3 (1c)
4 (1d)
5 (1e)
n-C11H23
Ph(CH2)2
Ph
pTol
pMeOC6H4
70 (5a)
60 (5b)
50 (5c)
65 (5d)
65 (5e)
[a] See Experimental Section. [b] Isolated yield after column
chromatography.
Finally, we investigated the formation of 1,2-disubsti-
tuted alkenes by the reaction of primary alkyl sulfoxides
and secondary zinc carbenoids. When secondary carbenoid
3b was added to α-sulfinyllithium species for the 1,2-intra-
molecular rearrangement, we did not observe the expected
alkene but rather the formation of hexylbenzene 13
(Scheme 9). This result can be rationalized by a reaction
between the in situ formed secondary zinc carbenoid 3b and
the lithiated sulfoxide to give the corresponding higher-or-
der zincate 12. In this particular case, a competition exists
between the butyl and sulfinyl groups for the rearrange-
ment. As a butyl group is a better migrating group, only
the product resulting from its migration is obtained.
To succeed in the preparation of 1,2-disubstituted olefins
from sulfinyl species, the intermolecular reaction was there-
fore tested. After metalation with LDA and transmetalation
with CuBr, the corresponding α-sulfinyl copper species was
treated at room temperature with the in situ prepared sec-
ondary zinc carbenoid 3b as described in Scheme 10. Under
such conditions, the zinc homologation–elimination oc-
curred to give alkene 15a in 60% isolated yield with a Z/E
ratio of 20:1 (Scheme 10).
The main reason is that such a quaternary α-sulfinyl or-
ganocopper species was found to be thermally unstable, and
even without addition of zinc carbenoid, this organocopper
species undergoes fast degradation when the temperature
reaches –40 °C. Therefore, the intramolecular 1,2-metalate
rearrangement was tested as described in Scheme 8 and
Table 3.
Scheme 8. Preparation of 1,1-disubstituted alkenes.
The observed stereoselectivity of the reaction (formation
of the Z-isomer as major isomer) is rather puzzling and
deeper mechanistic investigations are needed to clarify this
stereochemical outcome. Indeed, intramolecular chela-
tion[29] between the zinc organometallic species and the
oxygen of the sulfoxide to lead to the most stable intermedi-
ate having an anti relationship between the benzyl and the
alkyl (n-C11H23) groups, through a thermodynamic equili-
bration reaction,[30] followed by a β-elimination reaction
could rationalize the stereochemistry, but the discrepancies
in the E/Z ratio requires more study. Several additional ex-
Table 3. Preparation of 1,1-disubstituted alkenes from disubstituted
alkyl sulfoxides.
Entry[a]
R
R1
Yield [%][b]
1 (10a)
2 (10b)
3 (10c)
4 (10d)
n-C11H23
n-C11H23
Ph
n-C4H9
CH2CH=CH2 65 (11b)
n-C4H9
66 (11a)
68 (11c)
Ph
CH2CH=CH2 67 (11d)
[a] See Experimental Section. [b] Isolated yield after column
chromatography.
Scheme 9. Unsuccessful attempt to prepare 1,2-disubstituted alkenes.
Eur. J. Org. Chem. 2008, 4924–4931
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A. Abramovitch, I. Marek
FULL PAPER
General Procedure for the Intermolecular Homologation Reaction
(α-Sulfinyl Organocopper and Zinc Carbenoid; Procedure A): To a
prepared solution of LDA (2 mmol) in THF (10 mL) was added
the primary alkyl sulfoxide (2 mmol) dissolved in THF (2 mL) at
–70 °C. The reaction mixture was warmed to –40 °C and stirred
for an additional 30 min. CuBr (2 mmol) was then added, and the
reaction mixture was warmed to room temperature over 30 min.
Bis(iodomethyl)zinc carbenoid 3a (6 mmol), prepared from the re-
action of diethylzinc (1  in hexanes, 6 mL, 6 mmol) and diiodome-
thane (3.2 g, 12 mmol) in THF at –50 °C, was then added to the
reaction mixture in THF (10 mL) at room temperature. The re-
sulting black solution was allowed to stir for 1 h at room tempera-
ture. A mixture of NH4OH (30%) and saturated NH4Cl (1:2) was
added and the phases were separated. The water phase was ex-
tracted with diethyl ether (3ϫ), and the combined organic phase
was washed with Na2S solution, dried, filtered, and then concen-
trated to give a yellow crude product. After chromatography (hex-
ane), the colorless olefins were obtained.
Scheme 10. Preparation of 1,2-disubstituted alkenes by intermo-
lecular reaction.
amples were performed as reported in Table 4. In entry 3,
the stereochemistry is reversed (Z/E = 1:2) and could be
rationalized by isomerization of Z-styrenyl adduct 15d.[31]
Table 4. Preparation of 1,2-disubstituted alkenes.
General Procedure for the Intramolecular Homologation (α-Sulfinyl
Organolithium and Zinc Carbenoid; Procedure B): To a prepared
solution of LDA (2 mmol) in THF (10 mL) was added the primary
sulfoxide (2 mmol) dissolved in THF (2 mL) at –70 °C. The reac-
tion was warmed to –40 °C and stirred for an additional 30 min.
nBuLi (2 mmol) was added at –70 °C, and the reaction was allowed
to stir for 10 min. Bis(iodomethyl)zinc carbenoid 3a (2 mmol), pre-
pared from the reaction of diethylzinc (1  in hexanes, 2 mL,
2 mmol) and diiodomethane (1 g, 4 mmol) in THF at –50 °C, was
then added to the reaction mixture, and the resulting yellow solu-
tion was warmed to room temperature and stirred for 1 h. A satu-
rated solution of NH4Cl was then added and the phases were sepa-
rated. The water phase was extracted with diethyl ether (3ϫ), and
the combined organic phase was dried with Na2SO4, filtered, and
then concentrated to give a yellow oily crude product. After
chromatography (hexane), the colorless oily olefin was obtained.
Entry[a]
R
R1
Z/E ratio[b] Yield [%][c]
1 (1a)
2 (1b)
3 (1c)
4 (1f)
n-C11H23
Ph(CH2)2
Ph
PhCH2
PhCH2
PhCH2
PhCH2
20:1
3:1
60 (15a)
62 (15b)
51 (15c)
40 (15d)
1:2
iPr
12:1
[a] See Experimental Section. [b] Determined from the NMR spec-
trum of the crude reaction mixture. [c] Isolated yield after column
chromatography.
General Procedure with DMSO (Procedure C): To a prepared solu-
tion of LDA (2 mmol) in THF (10 mL) was added DMSO
(2 mmol) dissolved in THF (2 mL) at –70 °C. The reaction was
warmed to 0 °C and stirred for an additional 30 min. CuBr
(2 mmol) was then added at –40 °C, and the reaction mixture was
warmed to room temperature. 1,1-Diiodoalkane (4 mmol) dis-
Conclusions
We have disclosed an easy and straightforward prepara-
tion of substituted alkenes from various alkyl sulfoxides
either by an SN2 process (intermolecular homologation fol-
lowed by β-elimination) or by a 1,2-metalate rearrangement solved in THF (4 mL) was added at room temperature followed by
dibutylzinc, prepared from nBuLi (1.5  in hexane, 5.3 mL,
8 mmol) and zinc bromide (0.9 g, 4 mmol) in THF (10 mL) at
–30 °C. The resulting black solution was stirred for 1 h at room
temperature. A mixture of NH4OH (30%) and saturated NH4Cl
(1:2) was added and the phases were separated. The water phase
was extracted with diethyl ether (3ϫ), and the combined organic
phase was washed with Na2S solution, dried, filtered, and then
concentrated to give a yellow crude product. After chromatography
(hexane), the colorless olefin was obtained.
(intramolecular homologation followed by β-elimination).
In the latter case, the formation of a higher-order zincate is
necessary for the reaction to proceed.
Experimental Section
General: Starting sulfoxides were prepared from literature pro-
cedures[32] and the NMR spectroscopic data were in full agreement
with authentic samples: 1a, 1-methyl-4-(dodecylsulfinyl)benzene,
General Procedure for the Preparation of 1,2 Disubstituted Olefins
registry number 148017-75-8; 1b, 1-methyl-4-[2-phenylethylsulfinyl]- (General Procedure D): To a prepared solution of LDA (2 mmol)
benzene, registry number 120982-92-5; 1c, 1-methyl-4-[(phen-
ylmethyl)sulfinyl]benzene, registry number 10381-70-1; 1d, 1-
methyl-4-[(4-methylphenyl)methyl]sulfinylbenzene, registry number
in THF (10 mL) was added the sulfoxide (2 mmol) dissolved in
THF (2 mL) at –70 °C. The reaction was warmed to –60 °C and
stirred for an additional 30 min. CuBr (2 mmol) was then added at
95126-91-3; 1e, 1-methoxy-{[(4-methylphenyl)sulfinyl]methyl}- –60 °C, and the reaction was warmed to room temperature. 1,1-
benzene, registry number 180746-15-0; 1f, 1-methyl-4-[(2-meth-
ylpropyl)sulfinyl]benzene, registry number 77919-66-5; 10a, 1-[(1-
butyldodecyl)sulfinyl-4-methyl]benzene, registry number 667447-
30-5; 10c, 1-methyl-4-[(1-phenylpentyl)sulfinyl]benzene, registry
number 667447-32-7; 10d, 1-methyl-4-[(1-phenyl-3-buten-1-yl)sulf-
inyl]benzene, registry number 667447-34-9.
Diiodoalkane (4 mmol) dissolved in THF (4 mL) was added at
room temperature followed by dibutylzinc, prepared from nBuLi
(1.5  in hexane, 5.3 mL, 8 mmol) and zinc bromide (0.9 g,
4 mmol) in THF (10 mL) at –30 °C. The resulting black solution
was stirred for 1 h at room temperature. A mixture of NH4OH
(30%) and saturated NH4Cl (1:2) was added and the phases were
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Zinc Homologation–Elimination Reaction of α-Sulfinyl Carbanions
separated. The water phase was extracted with diethyl ether (3ϫ),
and the combined organic phase was washed with Na2S solution,
dried, filtered, and then concentrated to give a yellow crude prod-
uct. After chromatography (hexane), the colorless olefin was ob-
tained.
CDCl3): δ = 5.8–5.6 (m, 1 H), 5.1–5.0 (m, 2 H), 4.7 (s, 1 H), 4.7 (s,
1 H), 2.8 (d, J = 6.9 Hz, 2 H), 2 (t, J = 7.2 Hz, 2 H), 1.4–1.3 (m,
2 H), 1.3–1.1 (m, 16 H), 0.9 (t, J = 6.2 Hz, 3 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 141.6, 139.1, 138.6, 134.7, 130.3, 125.2,
118.2, 64.5, 32.3, 30.6, 29.9, 29.8, 29.7, 29.6, 27.7, 27.2, 23.03, 21.7,
14.4 ppm.
1-Tridecene (5a): The reaction was performed according to general
procedure A from dodecyl p-tolyl sulfoxide (1a; 617.2 mg, 2 mmol)
and gave 5a (0.281 g, 77%). When the reaction was performed ac-
cording to general procedure B, 1a (617.2 mg, 2 mmol) gave 5a
(0.280 g, 70%; registry number 2437-56-1). 1H NMR (300 MHz,
CDCl3): δ = 5.8–5.7 (m, 1 H), 5–4.8 (m, 2 H), 2.1–2.0 (m, 2 H),
1.3–1.1 (m, 18 H), 0.8 (t, J = 6.7 Hz, 3 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 139.1, 114.5, 34.1, 32, 29.9, 29.8,29.7, 29.6,
29.5,29.4, 29.2, 22.8, 14 ppm.
11c: The reaction was performed according to general procedure B
from 1-phenyl-1-(p-tolylsulfinyl)-pentane sulfoxide (10c; 572.9 mL,
2 mmol) and gave 11c (0.217 g, 68%; registry number 20826-80-6)
as a colorless oil. 1H NMR (300 MHz, CDCl3): δ = 7.3 (d, J =
6.9 Hz, 2 H), 7.2–7.0 (m, 2 H), 7.1 (d, J = 6.9 Hz, 1 H), 5.1 (d, J
= 1.2 Hz, 1 H), 4.9 (d, J = 1.2 Hz, 1 H), 2.4 (t, J = 7.1 Hz, 2 H),
1.4–1.2 (m, 4 H), 0.8 (t, J = 7.3 Hz, 3 H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 149.1, 143.3, 141.9, 128.7, 128.6, 127.6, 126.5, 125.9,
112.3, 36.3, 35.4, 31.9, 31.6, 30.8, 22.9, 22.8, 14.4, 14.3 ppm.
But-3-enylbenzene (5b): The reaction was performed according to
general procedure A from 3-phenyl 1-(p-tolylsulfinyl)propane (1b;
516.7 mg, 2 mmol) and gave 5b (0.18 g, 70%; registry number 768-
15a: The reaction was performed according to general procedure
D from dodecyl p-tolylsulfoxide (1a; 617.2 mg, 2 mmol) and gave
olefin 15a (0.2006 g, 60%; registry number 99464-25-2) as a color-
less oil (mixture of isomers). Major isomer was Z (Z/E = 20:1). 1H
NMR (300 MHz, CDCl3): δ = 7.5–7.3 (m, 2 H), 7.3–7.2 (m, 3 H),
5.7–5.5 (m, 2 H), 3.5 (d, J = 6.5 Hz, 2 H), 3.4 (d, J = 6 Hz, 2 H),
2.2 (q, J = 7 Hz, 2 H), 1.4–1.2 (m, 18 H), 0.9 (t, J = 7.5 Hz, 3 H)
ppm. 13C NMR (75 MHz, CDCl3): δ = 140.7, 131.7, 128.3, 128,
127.9, 125.5, 38.7, 33.1, 32.1, 31.5, 29.3, 29.2, 29, 28.8, 28.6, 26.9,
22.3, 13.7 ppm.
1
56-9) as a colorless oil. H NMR (300 MHz, CDCl3): δ = 7.2–7.0
(m, 5 H), 5.8–5.7 (m, 1 H), 4.9–4.8 (m, 2 H), 2.6 (t, J = 7.5 Hz, 2
H), 2.4–2.2 (m, 2 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 141.4,
137.7, 128, 127.9, 128.8, 125.4, 114.5, 35.1 ppm.
Vinylbenzene (5c): The reaction was performed according to gene-
ral procedure A from benzyl p-tolyl sulfoxide (1c; 460.6 mg,
2 mmol) and gave 5c (0.104 g, 50%; registry number 100-42-5) as
a colorless oil. 1H NMR (300 MHz, CDCl3): δ = 7.3–7.1 (m, 5 H),
6.7 (dd, J = 17.6 Hz, J = 10.8 Hz, 1 H), 5.7 (d, J = 10.8 Hz, 1 H),
5.2 (d, J = 10.8 Hz, 1 H) ppm. 13C NMR (75 MHz, CDCl3): δ =
137.5, 128.5, 128, 126.1, 113.9 ppm.
15b: The reaction was performed according to general procedure
D from 3-phenyl 1-(p-tolylsulfinyl)propane (1b; 516.7 mg, 2 mmol)
and gave olefin 15b (0.274 g, 62%; registry number 69485-56-9) as
a colorless oil (mixture of isomers). Major isomer was Z (Z/E =
3:1). 1H NMR (300 MHz, CDCl3): δ = 7.4–7.3 (m, 4 H), 7.3–7.2
(m, 6 H), 5.8–5.7 (m, 2 H), 5.7–5.6 (m, 2 H), 3.5 (d, J = 5 Hz, 2
H), 3.4 (d, J = 6 Hz, 2 H), 2.8 (t, J = 7.5 Hz, 2 H), 2.4 (q, J =
6 Hz, 2 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 143.8, 142.7,
132.9, 132.3, 130.2, 130.1, 127.8, 127.7, 127.6, 40.8, 37.8, 36.2,
35.3 ppm.
1-Methyl-4-vinylbenzene (5d): The reaction was performed accord-
ing to general procedure A from 4-methylbenzyl p-tolyl sulfoxide
(1d; 488.7 mg, 2 mmol) and gave 5d (0.153 g, 65%; registry number
1
622-97-9) as a colorless oil. H NMR (300 MHz, CDCl3): δ = 7.3
(d, J = 8.1 Hz, 2 H), 7.1 (d, J = 8.1 Hz, 2 H), 6.6 (dd, J = 10.8 Hz,
J = 10.8 Hz, 1 H), 5.7 (d, J = 17.7 Hz, 1 H), 5.1 (d, J = 11.1 Hz,
1 H), 2.3 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 137.9,
136.2, 135, 129.1, 126.1, 112.2, 21.8 ppm.
15c: The reaction was performed according to general procedure
D from benzyl p-tolyl sulfoxide (1c; 460.7 mg, 2 mmol) and gave
olefin 15c (0.2 g, 51%; registry number 1138-83-6) as a colorless oil
1-Methoxy-4-vinylbenzene (5e): The reaction was performed ac-
cording to general procedure A from 4-methoxybenzyl p-tolyl sulf-
oxide (1e; 520.7 mg, 2 mmol) and gave 5e (0.179 g, 67%; registry
1
(mixture of isomers). Major isomer was E (Z/E = 1/2). H NMR
1
(300 MHz, CDCl3): δ = 7.4–7.3 (m, 10 H), 6.4–6.3 (m, 2 H), 5.8
(q, J = 1.5 Hz, 2 H), 3.7 (d, J = 6.5 Hz, 2 H), 3.5 (d, J = 3.5 Hz,
2 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 140.2, 139.6, 130.5,
129.2, 129, 128.5, 128.1, 127.9, 126.5, 125.6, 125.4, 38.8, 38.4 ppm.
number 636-69-4) as a colorless oil. H NMR (300 MHz, CDCl3):
δ = 7.4 (d, J = 6.3 Hz, 2 H), 6.7 (d, J = 6.3 Hz, 2 H), 6.6–6.4 (m,
1 H), 5.5 (d, J = 18.6 Hz, 1 H), 5.0 (d, J = 9.9 Hz, 1 H), 3.7 (s, 3
H) ppm. 13C NMR (75 MHz, CDCl3): δ = 159.9, 136, 131, 126.5,
114.1, 111.6, 55.1 ppm.
15d: The reaction was performed according to general procedure
D from isobutyl p-tolyl sulfoxide (1f; 392.7 mg, 2 mmol) and gave
olefin 15d (0.13 g, 40%; registry number 6016877-6) as a colorless
oil (mixture of isomers). Major isomer was Z (Z/E = 12:1). 1H
NMR (300 MHz, CDCl3): δ = 7.4–7.3 (m, 2 H), 7.3–7.1 (m, 3 H),
5.6–5.5 (m, 2 H), 3.4 (d, J = 5 Hz, 2 H), 2.4–2.3 (m, 1 H), 1.1 (d,
J = 7 Hz, 6 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 141, 130.3,
130.2, 130.1, 130, 129.9, 127.7, 127.5, 24.5, 16, 15.9 ppm.
Allylbenzene (5f): The reaction was performed according to general
procedure C with DMSO (0.14 mL, 2 mmol) and 1,1-diiodo-2-
phenylethane (1.43 g, 4 mmol, ) and gave 5f (0.165 g, 70%; registry
number 410095-78-2) as a colorless oil. 1H NMR (200 MHz,
CDCl3): δ = 7.3–7.1 (m, 5 H), 6.1–5.9 (m, 1 H), 5.1–5.0 (m, 2 H),
3.4 (t, 2 H) ppm.
11a: The reaction was performed according to general procedure B
from (1-undecyl-1-butyl)-p-tolyl sulfoxide (10a; 729.4 mg, 2 mmol)
and gave 11a (0.314 g, 66%; registry number 667447-31-6) as a col-
Acknowledgments
1
orless oil. H NMR (300 MHz, CDCl3): δ = 4.6 (s, 1 H), 4.6 (s, 1
H), 1.9 (t, 4 H), 1.5–1.2 (m, 22 H), 0.9 (t, 6 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 157.9, 105.5, 38.2, 37.9, 32.5, 30.7, 30.4,
30.3, 30.0, 27.8, 23.5, 23.1, 14.1, 14.0 ppm.
The authors thank the Israel Science Foundation administrated by
the Israel Academy of Sciences and Humanities (grant N0 459/04),
the German-Israeli Foundation for scientific research and develop-
ment (GIF Research Grant No. I-871–62.5/2005), and the United
11b: The reaction was performed according to general procedure B
from (1-undecyl-1-allyl)-p-tolyl sulfoxide (10b; 697.3 mg, 2 mmol) States–Israel Binational Science Foundation (grant 2005128). I.M.
and gave 11b (0.293 g, 65%) as a colorless oil. 1H NMR (300 MHz,
is holder of the Sir Michael and Lady Sobell Academic Chair.
Eur. J. Org. Chem. 2008, 4924–4931
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
4929

A. Abramovitch, I. Marek
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Published Online: September 9, 2008
Eur. J. Org. Chem. 2008, 4924–4931
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
4931