Phospholane-catalyzed wittig reaction

Article abstract of DOI:10.1002/ejoc.201500243

We identified 2-phenylisophosphindoline 2-oxide as a suitable and potentially tunable catalyst for the catalytic Wittig reaction of aldehydes with activated organohalides. This catalyst was obtained by a straightforward two-step synthesis. Trimethoxysilane proved to be an efficient reducing agent for the in situ generation and regeneration of the catalyst from the corresponding phosphane oxide. Sodium carbonate was identified as a suitable base for the transformation. It is noteworthy that the particle size of the sodium carbonate had a tremendous effect on the outcome of the reaction. Under the optimized reaction conditions, 23 aldehydes were converted into the corresponding alkenes in high isolated yields of up to 88%. Moreover, an asymmetric catalytic Wittig reaction was performed for the desymmetrization of a prochiral diketone.

Full text of DOI:10.1002/ejoc.201500243

FULL PAPER
DOI: 10.1002/ejoc.201500243
Phospholane-Catalyzed Wittig Reaction
Thomas Werner,*[a] Marcel Hoffmann,[a] and Sunetra Deshmukh[a]
Keywords: Synthetic methods / Homogeneous catalysis / Wittig reactions / Alkenes / Phosphanes
We identified 2-phenylisophosphindoline 2-oxide as a suit-
able and potentially tunable catalyst for the catalytic Wittig
reaction of aldehydes with activated organohalides. This cat-
alyst was obtained by a straightforward two-step synthesis.
Trimethoxysilane proved to be an efficient reducing agent for
the in situ generation and regeneration of the catalyst from
the corresponding phosphane oxide. Sodium carbonate was
identified as a suitable base for the transformation. It is note-
worthy that the particle size of the sodium carbonate had a
tremendous effect on the outcome of the reaction. Under the
optimized reaction conditions, 23 aldehydes were converted
into the corresponding alkenes in high isolated yields of up
to 88%. Moreover, an asymmetric catalytic Wittig reaction
was performed for the desymmetrization of a prochiral diket-
one.
Various systems for the reduction of phosphane oxides
into their corresponding phosphanes have been reported.
For example, these systems include aluminum hydrides,[13]
SmI2/hexamethylphosphoric triamide (HMPA),[14] TiCp2Cl2/
Mg,[15] Bi/TiO2,[16] InBr3/1,1,3,3-tetramethyldisilazane
(TMDS),[17] SiCl4,[18] electroreductions,[19] and (COCl)2/
Hantzsch ester.[20] Nevertheless, these procedures are not
suitable, as the reaction conditions and necessary reagents
are incompatible with the components of a Wittig reaction.
Recently, organosilanes in combination with specially de-
signed phospholes and phospholanes were utilized for the
in situ reduction to enable the performance of the catalytic
Introduction
Phosphorus-based reagents are versatile, important com-
pounds that are utilized in numerous organic transforma-
tions.[1] The Wittig,[2] Appel,[3] and Mitsunobu[4] reactions
are three examples of frequently employed methods that are
based on phosphanes. Nevertheless, the phosphane oxides
that form as byproducts in these reactions often hamper the
purification of the desired products and lead to an increase
in the associated costs as a result of low atom economy.[5]
In addition to the numerous immobilization approaches,[6]
the regeneration of the phosphane is performed under
harsh reaction conditions or by the utilization of highly
toxic phosgene.[7] A promising alternative involves the in
situ reduction of the phosphane oxide and the use of cata-
lytic amounts of the phosphane.[8]
Carbonyl olefinations are one of the fundamental and
most frequently employed transformations in organic syn-
thesis.[1c,9] Hence, the development of catalytic Wittig reac-
tions is a challenging yet worthy task. Despite the draw-
backs described above, this long known reaction is the most
commonly used method to convert aldehydes and ketones
into the corresponding olefins, even on multigram scales, to
provide products with high regio- and E/Z-selectivity.[10]
The first examples of catalytic Wittig-type reactions utilized
arsenic-[11] and telluride-based[12] catalysts. One major issue
in the development of catalytic Wittig reactions involves the
compatibility of the reducing agent, which is used for the
in situ reduction of the phosphane oxide, with the other
reagents and products.
Appel,[8h] Staudinger,[21] and Wittig reactions.[8b,8j,8k,8o]
A
recently published life cycle assessment (LCA) by Huij-
bregts et al. indicates that ecological factors such as the
cumulative energy demand and greenhouse gas emissions
might be reduced under certain conditions by applying
these methods.[22] The development of catalytic variations
of the above-mentioned phosphorus-based transformations
can generally be categorized into redox-shuttled and redox-
neutral approaches (Scheme 1).[5]
In redox-shuttled processes, the oxidation state of the
catalyst changes from PIII in the phosphane into PV in the
corresponding oxide, whereas in redox-neutral processes,
the oxidation state remains constant throughout the cata-
lytic cycle. The redox-shuttled process was established by
O’Brien for catalytic Wittig reactions.[8b,8j,8k,8o] Further-
more, van Delft et al. developed catalytic Appel, Staud-
inger, and aza-Wittig reactions by using this strategy.[8h,8i,8l]
Catalytic diaza-Wittig reactions and catalytic amide forma-
tions have been recently reported.[23] Marsden established
the redox-neutral strategy for a catalytic aza-Wittig[24] reac-
tion, as Denton utilized it for catalytic Appel reac-
tions.[8e–8g] The phospholane structure is a common motif
for catalysts in both redox-shuttled and redox-neutral pro-
[a] Leibniz-Institut für Katalyse e.V. an der Universität Rostock,
Albert-Einstein-Strasse 29a, 18059 Rostock, Germany
E-mail: Thomas.Werner@catalysis.de
http://www.catalysis.de
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201500243.
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Phospholane-Catalyzed Wittig Reaction
by employing them in the model reaction. We identified
HSi(OMe)3 and Na2CO3 as a suitable reducing agent and
base, respectively. The utilization of Na2CO3 as a base in
catalytic Wittig reactions has been previously reported by
O’Brien and co-workers.[8b,8k] However, in our hands, our
very promising initial results were difficult to reproduce,
and the yields varied under the same reaction conditions
between 12 and 85%. However, a cautious investigation re-
vealed the significance of the grain size of Na2CO3 on the
outcome of the reaction. A detailed evaluation of the influ-
ence of the particle size of Na2CO3 revealed that ground
Na2CO3 with a grain size of 125–250 μm gave reproducible
and excellent yields of approximately 85%. In contrast,
Na2CO3 that had a particle size between 125 and 1000 μm
afforded varying yields in the above-mentioned range (Sup-
porting Information). Under our initial reaction conditions,
the utilization of 2 as a catalyst led to 5a in yields up to
85% (Table 1, Entry 1). Other cyclic and acyclic phospha-
nes and phosphane oxides gave the desired product 5a in
yields of 5–71% (Table 1, Entries 2–6). Further optimiza-
tion studies led to a decrease in the amount of the precata-
lyst to 5 mol-%, the retention of toluene as the solvent of
choice, a lower reaction temperature of 125 °C, and a reac-
tion time of 16 h (Table 1, Entry 7). A further decrease in
the amount of precatalyst to 2.5 mol-% resulted in a de-
creased yield of 52% (Table 1, Entry 8).
Scheme 1. General approaches to catalytic processes utilizing phos-
phorus-based organocatalysts and selected examples of organo-
phosphorus catalysts.
cesses (Scheme 1). Moreover, it is well-known that modifi-
cations to the basic framework and the introduction of sub-
stituents have a great impact on the catalytic activity of
those catalysts. We are interested in the synthesis and appli-
cation of phosphorus-based organocatalysts.[25] In this con-
text, we recently reported the first asymmetric catalytic Wit-
tig reaction that utilizes catalytic amounts of chiral phos-
phanes.[8n] Promising results were also obtained with phos-
pholane derivatives such as 1,2-bis[(2S,5S)-2,5-dimethyl-
phospholano]benzene (S,S-Me-DuPhos). Hence, we envi-
sioned phospholane derivative 1 to be a potentially tunable
catalyst for catalytic Wittig reactions (Scheme 2).
Table 1. Utilization of different phosphorus-based catalysts in the
model reaction of 3a with 4a.[a]
Scheme 2. Preparation of 2-phenylisophosphindoline 2-oxide (2).
Reagents and conditions: (1) (a) Mg, tetrahydrofuran (THF),
23 °C, 16 h; (b) PhPCl2, THF, 23 °C, 3 h. (2) H2O2 (10%), acetone,
reflux, 1 h, 49% over two steps.
[a] Screening reactions were performed on a 1.5 mmol scale. Rea-
gents and conditions: R3P or R3P=O (catalytic amount), benzalde-
hyde (3a, 0.5 m in toluene, 1.0 equiv.), methyl bromoacetate (4a,
1.2 equiv.), trimethoxysilane (2.0 equiv.), Na2CO3 (1.5 equiv.), 24 h.
[b] Calculated/determined by GC analysis using n-hexadecane as
the internal standard. [c] 16 h.
Results and Discussion
Initially, we prepared the desired product 2 by a two-step
synthesis starting from α,αЈ-dichloro-ortho-xylene.[26] How-
Under the reaction conditions, we propose that precata-
ever, phospholane 1 is air sensitive and partially oxidized lyst 2 is initially reduced by treatment with trimethoxysilane
during purification or when stored under ambient condi- to give the corresponding phosphane 1 (Scheme 3). The for-
tions. Hence, 1 was converted into the corresponding mation of hexamethyldisilicate, as the only byproduct from
bench-stable and easy-to-handle phospholane oxide 2.
the phosphane oxide reduction, was detected by GC–MS
As a proof of principle, we chose the conversion of benz- analysis and can easily be separated from the product upon
aldehyde (3a) and methyl bromoacetate (4a) into methyl the conclusion of the reaction. In situ formation of the cor-
phenylpropenoate (5a) as the model reaction to evaluate responding phosphonium salt in step 2 and subsequent de-
various reaction conditions and potential catalysts for the protonation in step 3 leads to the Wittig ylide. Finally, the
catalytic Wittig reaction (Table 1). In our initial studies, sev- conversion of aldehyde 3a in the last step regenerates phos-
eral phosphanes and phosphane oxides in addition to com- phane oxide 2 and releases the desired olefinic product 5a.
pound 2 as well as numerous silanes, bases, solvents, and At this point, we want to highlight that the complete cata-
temperatures over a range of 100–150 °C were examined lytic cycle consists in total of four steps. Hence, the conver-
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T. Werner, M. Hoffmann, S. Deshmukh
FULL PAPER
Scheme 3. The four consecutive reaction steps of the catalytic Wittig reaction.
sion and selectivity of each step of the catalytic cycle must the conversion of meta-anisaldehyde (3h) with bromoaceto-
be Ͼ95% in average to finally provide 5a in 85% yield. nitrile and methyl 2-bromopropionate led to the corre-
We were then interested in the scope and limitations of sponding olefins 5j and 5k in 84 and 54% yield, respectively
the catalytic Wittig reaction under our standard conditions. (Table 2, Entries 10 and 11). The moderate yield of 5k
Hence, we examined the reaction of various aromatic, might be attributed to steric effects. Notably, when the reac-
heteroaromatic, and aliphatic aldehydes 3 with halo-substi- tion was performed under harsher conditions (i.e., 10 mol-
tuted derivatives 4 to yield the desired alkenes 5 (Scheme 4). % 2, 150 °C, 24 h), products 5a–5f were obtained with a
higher (E) selectivity but with slightly lower yields. Notably,
the E/Z selectivities were in contrast to the levels of selectiv-
ity obtained by the same substrates in other catalytic Wittig
transformations.[8b,8j–8n] Here, the selectivities are higher
when the amount of catalyst and the reaction temperature
is increased (Table 2, Entries 1–6). One explanation for this
might be that some equilibration is occurring at 125 °C. The
Scheme 4. Evaluation of the scope and limitations of the catalytic
Wittig reaction under standard reaction conditions (EWG = elec-
tron-withdrawing group).
E/Z ratio of product 5a (83:17) did not change significantly
when it was stirred in the presence of 5 mol-% 2 and
HSi(OMe)3 in toluene at 125 °C for 16 h.
The scope of the substrates for this reaction is not restric-
ted to aromatic aldehydes. We also successfully employed
heteroaromatic and aliphatic aldehydes (Table 3). The cor-
responding heteroaromatic products 5l–5o were obtained in
good to excellent isolated yields of 72–88%. In contrast,
quinoline derivative 5p was obtained in only 22% yield.
This drastic drop in the yield of 5p compared to 5b and 5l–
5o might be attributed to the pyridine moiety, which can
participate in a side reaction such as an alkylation as a re-
sult of the Lewis base nature of the nitrogen atom. Ali-
phatic aldehydes and 4a were converted into olefins 5q–5w
in slightly lower yields of 66–78%.
We began by studying the conversion of aromatic alde-
hydes 3a–3f and methyl bromoacetate (4a) into the corre-
sponding alkenes 5a–5f (Table 2, Entries 1–7). The employ-
ment of benzaldehyde (3a) yielded methyl 3-phenylpropeno-
ate (5a) in 82% isolated yield (Table 2, Entry 1). The utiliza-
tion of methyl chloroacetate (4b) or iodoacetate (4c) led to
significantly lower yields of 24 and 30%, respectively. The
reaction of 2-naphthaldehyde (3b) with 4a afforded the cor-
responding olefin 5b in 82% yield (Table 2, Entry 2). More-
over, substituted benzaldehydes that have electron-donating
or -withdrawing groups could be converted with similar effi-
ciency into 5c in 83% yield, 5d and 5e, both in 76% isolated
Recently, we reported the first enantioselective catalytic
yield, and tert-butyl derivative 5f in 60% yield (Table 2, En- Wittig reaction.[8n] So far, there are very few examples of
tries 3–6). The reaction of methoxy-substituted benzalde- stoichiometric modifications to this reaction.[27] We exam-
hydes 3g–3i gave the desired products 5g–5i in up to 87% ined the desymmetrization of prochiral diketone 6 in the
yield (Table 2, Entries 7–9). The employment of other acti- presence of a catalytic amount of a chiral phosphane to give
vated halogenated compounds is also possible. For example, bicyclic olefin 7 (Scheme 5). In the context of this work, we
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Phospholane-Catalyzed Wittig Reaction
Table 2. Substrate study of the catalytic Wittig reaction with dif-
ferent aryl aldehydes and organohalides.[a]
Table 3. Substrate scope for the reaction of heteroaromatic and ali-
phatic substrates 3l–3w with methyl bromoacetate (4a).[a]
[a] Reagents and conditions: aldehyde
3 (0.5 m in toluene,
1.0 equiv.), organohalide (1.2 equiv.), 2-phenylisophosphindoline 2-
oxide (2, 5 mol-%), trimethoxysilane (2.0 equiv.), Na2CO3
(1.5 equiv.), 125 °C, 16 h. Isolated yields are reported. E/Z ratios
[a] Reactions were conducted on a 1–2 mmol scale. Reagents and
conditions: aldehyde 3 (0.5 m in toluene, 1.0 equiv.), organohalide
(1.2 equiv.), 2-phenylisophosphindoline 2-oxide (2, 5 mol-%), tri-
methoxysilane (2.0 equiv.), Na2CO3 (1.5 equiv.), 125 °C, 16 h. Iso-
1
were determined by H NMR spectroscopy.
1
lated yields are reported. E/Z ratios were determined by H NMR
spectroscopy. [b] The use of methyl chloroacetate (4b) or iodoacet-
ate (4c) instead of 4a led to 24 and 30% yield, respectively, of the
product. [c] Reagents and conditions: aldehyde 3 (0.5 m in toluene,
1.0 equiv.), methyl bromoacetate (4a) (1.2 equiv.), 2-phenylisophos-
phindoline 2-oxide (2, 10 mol-%), trimethoxysilane (2.0 equiv.),
Na2CO3 (1.5 equiv.), 150 °C, 24 h, yields and E/Z ratios were deter-
were interested in the further elaboration of this reaction
by screening potential chiral catalysts 8–10 under thermal
conditions (Table 4). Precatalyst 2 gave the desired product
7 in 72% yield and with the expected 1:1 mixture of
enantiomers (Table 4, Entry 1). (R,R)-1,2-Ethanediylbis-
1
mined by H NMR spectroscopy.
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T. Werner, M. Hoffmann, S. Deshmukh
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Scheme 5. Chiral phosphane catalysts for the enantioselective catalytic Wittig reaction.
[(2-methoxyphenyl)phenylphosphane] [(R,R)-DIPAMP, 8] reaction. Na2CO3 was employed as a base in combination
and (4R,5R)-4,5-bis[(diphenylphosphanyl)methyl]-2,2-di- with trimethoxysilane as the in situ reducing agent. The
methyl-1,3-dioxolane [(R,R)-DIOP, 9] gave the desired particle size of Na2CO3 was identified as a crucial factor
product 7 in low yields and with low enantioselectivities for the reproducibility of the reaction. Hexamethyldisilicate
(Table 4, Entries 2 and 3).
was produced as the only byproduct of the phosphane oxide
reduction. Aromatic, heteroaromatic, and aliphatic alde-
hydes underwent the reaction with methyl bromoacetate
and bromoacetonitrile to afford products in yields up to
88%. This is especially remarkable because the four steps of
the catalytic cycle must successfully proceed with an average
yield of about 97% for each step. In attempts towards an
asymmetric catalytic Wittig reaction for the desymmetriz-
ation of a prochiral diketone, a yield of up to 53% and an
ee value of up to 86% were obtained.
Table 4. Screening chiral catalysts 8–13 in the enantioselective cata-
lytic Wittig reaction.
Entry Catalyst mol-%
Yield / %
ee / %[a]
er [R/S][a]
1
2
3
4
5
6
7
2
8
10
5
5
5
5
5
5
72[b]
Ͻ20[c]
29[b]
8[c]
0
8
1
86
36
32
62
50:50
54:46
55:45
81:19
68:32
34:66
81:19
Experimental Section
9
10
11
12
13
General Methods: All reagents were purchased from commercial
sources and used without further purification, with the exception
of benzaldehyde, which was freshly distilled. Toluene and THF
were freshly distilled from sodium/benzophenone. To obtain repro-
ducible results, it is important to use sodium carbonate with a small
particle size (125–250 μm).
53[c]
Ͻ5[c]
50[b]
[a] The ee values and enantiomeric ratios (er) were determined by
chiral GC–MS analysis. [b] Isolated yield after column chromatog-
raphy. [c] The yields were determined by H NMR analysis of the
1
2-Phenylisophosphindoline 2-Oxide (2): THF (10 mL) was added to
magnesium turnings (3.6 g, 0.15 mol), which were then activated
with 1,2-dibromoethane (0.24 mL) at 23 °C. The solvent was re-
moved in vacuo, and fresh THF (40 mL) was added again. A solu-
tion of 1,2-bis(chloromethyl)benzene (6.4 g, 37 mmol) in THF
(450 mL) was added to this mixture over a period of 3.5 h at 23 °C,
and the greenish solution was stirred for another 15 h. This Grig-
nard solution was poured dropwise and simultaneously with a solu-
tion of phenyldichlorophosphane (6.6 g, 37 mmol) in THF
(100 mL) into vigorously stirred THF (100 mL) over a period of
1.5 h. The yellowish mixture was then stirred at 23 °C for an ad-
reaction mixture.
Nevertheless, high enantioselectivity can be obtained in
the presence of catalytic amounts of (S,S)-Me-DuPhos (10)
which afforded an excellent enantiomeric excess (ee) value
of 86% (Table 4, Entry 4). However, the yield was Ͻ10%.
The employment of 1,2-bis[(2R,5R)-2,5-dimethylphos-
pholano]ethane [(R,R)-Me-BPE, 11] gave the desired prod-
uct 7 in 53% yield with an enantiomeric excess value of
36% (Table 4, Entry 5). This result indicates that both good
yields and selectivities ought to be achievable in general.
Catalyst 12 gave 7 in 32%ee (Table 4, Entry 6). Interest-
ingly, chiral phosphane 13 contains a subunit of our model
catalyst 2. In the presence of 13, the desired product 7 was
obtained in 50% yield and 62%ee (Table 4, Entry 6).
ditional 3 h. Subsequently,
a satd. aqueous NH4Cl solution
(300 mL) was added, and the aqueous layer was extracted with
Et2O (3ϫ 150 mL). The combined organic layers were dried with
MgSO4, and the solvents were removed. The crude product was
dissolved in acetone (100 mL) and cooled to 0 °C, and an aqueous
H2O2 solution (10 wt.-%, 78 mL) was added slowly. The mixture
was allowed to reach 23 °C and was then heated at reflux for 1 h.
All of the volatiles were removed in vacuo. The residue was dried
with MgSO4 in CH2Cl2 and purified by flash column chromatog-
raphy (ethyl acetate/ethanol, 20:1) to afford 2 (4.1 g, 49%) as a pale
Conclusions
As initially envisioned, 2-phenylisophosphindoline 2-ox-
ide (2) acts as an efficient precatalyst in the catalytic Wittig orange oil. 1H NMR (300 MHz, CDCl3): δ = 3.33–3.63 (m, 4 H,
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Phospholane-Catalyzed Wittig Reaction
CH2), 7.30–7.64 (m, 9 H, ArH) ppm. 13C NMR: δ = 35.4 (d, JC,P 166.6 (C=O) ppm. MS (EI, 70 eV): m/z (%) = 220 (52) [M]+, 205
= 67.6 Hz, 2ϫ CH2), 127.3 (d, JC,P = 15.2 Hz, 2ϫ CH), 128.0 (d,
JC,P = 1.0 Hz, 2ϫ CH), 128.7 (d, JC,P = 11.7 Hz, 2ϫ CH), 129.7
(d, JC,P = 9.5 Hz, 2ϫ CH), 132.2 (d, JC,P = 2.7 Hz, CH), 133.4
(C), 135.6 (d, JC,P = 10.1 Hz, 2ϫ C) ppm. 31P NMR: δ =
56.01 ppm. MS (EI, 70 eV): m/z (%) = 228 (100) [M]+, 165 (15),
104 (65), 103 (22), 78 (21), 77 (18). HRMS (EI): calcd. for
C14H13OP [M]+ 228.0699; found 228.0697.
(16) [M+ – Me], 189 (100) [M+ – OMe], 161 (17) [M+ – CO2Me],
145 (19), 115 (12), 102 (22). C12H12O4 (220.22): calcd. C 65.45, H
5.49; found C 65.16, H 5.33.
Methyl 3-(4-Chlorophenyl)propenoate (5d): By following GP1, 4-
chlorobenzaldehyde (3d, 248 mg, 1.76 mmol), methyl bromoacetate
(4a, 323 mg, 2.11 mmol), 2-phenylisophosphindoline 2-oxide (2,
20 mg, 0.09 mmol), Na2CO3 (280 mg, 2.64 mmol), and HSi(OMe)3
General Procedure (GP1) for the Catalytic Wittig Reaction: A (430 mg, 3.52 mmol) were combined in toluene (3.5 mL). Purifica-
15 mL Ace pressure tube that was equipped with a stir bar was
charged with 2-phenylisophosphindoline 2-oxide (2, 0.08 mmol,
5 mol-%), aldehyde 3 (0.5 m in toluene, 1.5 mmol, 1.0 equiv.),
tion by flash chromatography (SiO2; cyclohexane/EtOAc, 10:1) af-
forded 5d (262 mg, 76%; E/Z, 80:20) as a colorless solid. 1H NMR
(300 MHz, CDCl3, major isomer): δ = 3.82 (s, 3 H, CH3), 6.42 (d,
J = 16.0 Hz, 1 H, CH), 7.35–7.39 (m, 2 H, ArH), 7.45–7.48 (m, 2
H, ArH), 7.65 (d, J = 16.0 Hz, 1 H, CH) ppm. 13C NMR (75 MHz,
CDCl3, major isomer): δ = 51.5 (CH3), 118.2 (CH), 128.9 (2ϫ CH),
129.0 (2ϫ CH), 132.7 (C), 135.9 (C), 143.1 (CH), 166.8
(C=O) ppm. MS (EI, 70 eV): m/z (%) = 198 (17) [M]+, 196 (51)
[M]+, 167 (33), 165 (100) [M+ – OMe], 137 (32) [M+ – CO2Me],
102 (31), 101 (30), 75 (19). C10H9ClO2 (196.63): calcd. C 61.08, H
4.61; found C 60.99, H 4.33.
Na2CO3 (2.3 mmol, 1.5 equiv.), organohalide
4
(1.8 mmol,
1.2 equiv.), and HSi(OMe)3 (3.0 mmol, 2.0 equiv.). The tube was
then purged with argon and sealed with an O-ring cap, and the
reaction mixture was heated at 125 °C for 16 h. After cooling to
23 °C, purification was performed by flash chromatography [SiO2;
cyclohexane/ethyl acetate (EtOAc)].
Methyl 3-Phenylpropenoate (5a): By following GP1, benzaldehyde
(3a, 161 mg, 1.52 mmol), methyl bromoacetate (4a, 279 mg,
1.82 mmol), 2-phenylisophosphindoline 2-oxide (2, 17 mg,
0.08 mmol), Na2CO3 (242 mg, 2.28 mmol), and HSi(OMe)3
(371 mg, 3.04 mmol) were combined in toluene (3.0 mL). Purifica-
tion by flash chromatography (SiO2; cyclohexane/EtOAc, 20:1) af-
Methyl 3-[(1,1Ј-Biphenyl)-4-yl]propenoate (5e): By following GP1,
4-phenylbenzaldehyde (3e, 273 mg, 1.50 mmol), methyl bromoacet-
ate (4a, 275 mg, 1.80 mmol), 2-phenylisophosphindoline 2-oxide (2,
17 mg, 0.07 mmol), Na2CO3 (238 mg, 2.18 mmol), and HSi(OMe)
1
forded 5a (203 mg, 82%; E/Z, 83:17) as a colorless oil. H NMR
(426 mg, 3.49 mmol) were combined in toluene (3.0 mL). Purifi-
3
(300 MHz, CDCl3, major isomer): δ = 3.82 (s, 3 H, CH3), 6.46 (d, cation by flash chromatography (SiO2; cyclohexane/EtOAc, 5:1) af-
1
J = 16.0 Hz, 1 H, CH), 7.38–7.43 (m, 3 H, ArH), 7.51–7.56 (m, 2
forded 5e (272 mg, 76%; E/Z, 85:15) as a colorless solid. H NMR
(300 MHz, CDCl3, major isomer): δ = 3.84 (s, 3 H, CH3), 6.49 (d,
H, ArH), 7.72 (d, J = 16.0 Hz, 1 H, CH) ppm. 13C NMR (75 MHz,
CDCl3, major isomer): δ = 51.6 (CH3), 117.7 (CH), 128.0 (2ϫ CH), J = 16.0 Hz, 1 H, CH), 7.36–7.42 (m, 1 H, ArH), 7.44–7.50 (m, 2
128.8 (2ϫ CH), 130.2 (CH), 134.2 (C), 144.7 (CH), 167.3 H, ArH), 7.59–7.66 (m, 6 H, ArH), 7.75 (d, J = 16.0 Hz, 1 H,
(C=O) ppm. MS (EI, 70 eV): m/z (%) = 162 (51) [M]+, 161 (25),
CH) ppm. 13C NMR (75 MHz, CDCl3, major isomer): δ = 51.6
131 (100) [M+ – OMe], 103 (62) [M+ – CO2Me], 102 (16), 77 (35). (CH3), 117.5 (CH), 126.9 (2ϫ CH), 127.4 (2ϫ CH), 127.8 (CH),
128.5 (2ϫ CH), 128.8 (2ϫ CH), 133.2 (C), 140.0 (C), 143.0 (C),
Methyl 3-(2-Naphthyl)propenoate (5b): By following GP1, 2-naph-
144.3 (CH), 167.4 (C=O) ppm. MS (EI, 70 eV): m/z (%) = 238 (100)
thaldehyde (3b, 339 mg, 2.17 mmol), methyl bromoacetate (4a,
[M]+, 207 (62) [M+ – OMe], 178 (76) [M+ – CO2Me], 165 (30), 152
398 mg, 2.60 mmol), 2-phenylisophosphindoline 2-oxide (2, 25 mg,
(25), 89 (25).
0.11 mmol), Na2CO3 (345 mg, 3.26 mmol), and HSi(OMe)3
(530 mg, 4.34 mmol) were combined in toluene (4.3 mL). Purifica-
tion by flash chromatography (SiO2; cyclohexane/EtOAc, 20:1) af-
forded 5b (378 mg, 82%; E/Z, 86:14) as a colorless solid. 1H NMR
Methyl 3-(4-tert-Butylphenyl)propenoate (5f): By following GP1, 4-
tert-butylbenzaldehyde (3f, 230 mg, 1.42 mmol), methyl bromoacet-
ate (4a, 261 mg, 1.71 mmol), 2-phenylisophosphindoline 2-oxide (2,
(300 MHz, CDCl3, major isomer): δ = 3.85 (s, 3 H, CH3), 6.57 (d, 17 mg, 0.07 mmol), Na2CO3 (226 mg, 2.13 mmol), and HSi(OMe)
J = 16.0 Hz, 1 H, CH), 7.48–7.54 (m, 2 H, CH), 7.66–7.70 (m, 1
H), 7.80–7.91 (m, 4 H), 7.93–7.97 (m, 1 H) ppm. 13C NMR
(75 MHz, CDCl3, major isomer): δ = 51.5 (CH3), 117.7 (CH), 123.3
(CH), 126.5 (CH), 127.0 (CH), 127.6 (CH), 128.4 (CH), 128.5
(347 mg, 2.84 mmol) were combined in toluene (2.8 mL). Purifi-
3
cation by flash chromatography (SiO2; cyclohexane/EtOAc, 20:1)
1
afforded 5f (186 mg, 60%; E/Z, 81:19) as a yellowish oil. H NMR
(300 MHz, CDCl3): δ = 1.34 (s, 9 H, CH3), 3.81 (s, 3 H, CH3), 6.42
(CH), 129.8 (CH), 131.7 (C), 133.1 (C), 134.0 (C), 144.7 (CH), (d, J = 16.0 Hz, 1 H, CH), 7.41–7.50 (m, 4 H, ArH), 7.70 (d, J =
167.3 (C=O) ppm. MS (EI, 70 eV): m/z (%) = 212 (100) [M]+, 211
16.0 Hz, 1 H, CH) ppm. 13C NMR (75 MHz, CDCl3): δ = 30.9
(14), 182 (14), 181 (94) [M+ – OMe], 153 (52) [M+ – CO2Me], 152 (3ϫ CH3), 34.6 (C), 51.3 (CH3), 116.7 (CH), 125.7 (2ϫ CH), 127.8
(78), 151 (21), 127 (13), 76 (27). C14H12O2 (212.25): calcd. C 79.22, (2ϫ CH), 131.5 (C), 144.5 (CH), 153.5 (C), 167.2 (C=O) ppm. MS
H 5.70; found C 79.16, H 5.63.
(EI, 70 eV): m/z (%) = 218 (20) [M]+, 203 (100) [M+ – Me], 128
(10).
Methyl 3-(4-Methoxycarbonylphenyl)propenoate (5c): By following
GP1, 4-(methoxycarbonyl)benzaldehyde (3c, 262 mg, 1.59 mmol),
methyl bromoacetate (4a, 292 mg, 1.91 mmol), 2-phenylisophos-
Methyl 3-(4-Methoxyphenyl)propenoate (5g): By following GP1, 4-
methoxybenzaldehyde (3g, 202 mg, 1.48 mmol), methyl bromoacet-
phindoline 2-oxide (2, 18 mg, 0.08 mmol), Na2CO3 (253 mg, ate (4a, 217 mg, 1.42 mmol), 2-phenylisophosphindoline 2-oxide (2,
2.39 mmol), and HSi(OMe)3 (389 mg, 3.18 mmol) were combined
in toluene (3.2 mL). Purification by flash chromatography (SiO2;
18 mg, 0.08 mmol), Na2CO3 (232 mg, 2.18 mmol), and HSi(OMe)
(288 mg, 2.36 mmol) were combined in toluene (3.0 mL). Purifi-
3
cyclohexane/EtOAc, 5:1) afforded 5c (290 mg, 83%; E/Z, 76:24) as
cation by flash chromatography (SiO2; cyclohexane/EtOAc, 20:1)
1
a colorless solid. H NMR (300 MHz, CDCl3, major isomer): δ = afforded 5g (186 mg, 65%; E/Z, 81:19) as a yellowish solid. 1H
3.83 (s, 3 H, CH3), 3.94 (s, 3 H, CH3), 6.53 (d, J = 16.1 Hz, 1 H, NMR (300 MHz, CDCl3): δ = 3.80 (s, 3 H, CH3), 3.84 (s, 3 H,
CH), 7.57–7.62 (m, 2 H, ArH), 7.72 (d, J = 16.1 Hz, 1 H, CH), CH3), 6.32 (d, J = 15.9 Hz, 1 H, CH), 6.89–6.93 (m, 2 H, ArH),
8.01–8.08 (m, 2 H, ArH) ppm. 13C NMR (75 MHz, CDCl3, major
isomer): δ = 51.5 (CH3), 51.9 (CH3), 119.9 (CH), 127.6 (2ϫ CH),
129.8 (2ϫ CH), 131.1 (C), 138.3 (C), 143.1 (CH), 166.0 (C=O),
7.47–7.50 (m, 2 H, ArH), 7.66 (d, J = 15.9 Hz, 1 H, CH) ppm. 13C
NMR (75 MHz, CDCl3): δ = 51.5 (CH3), 55.2 (CH3), 114.2 (2ϫ
CH), 115.2 (CH), 127.0 (C), 129.6 (2ϫ CH), 144.4 (CH), 161.3
Eur. J. Org. Chem. 2015, 3286–3295
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3291

T. Werner, M. Hoffmann, S. Deshmukh
FULL PAPER
(C), 167.6 (C=O) ppm. MS (EI, 70 eV): m/z (%) = 192 (71) [M]+, (C), 138.7 (CH), 159.3 (C), 169.0 (C=O) ppm. MS (EI, 70 eV): m/z
161 (100) [M+ – OMe], 133 (31) [M+ – CO2Me], 89 (16).
(%) = 206 (72) [M]+, 175 (25) [M+ – OMe], 146 (100) [M+
CO2Me], 131 (22), 115 (33), 103 (28), 91 (23).
–
Methyl 3-(3-Methoxyphenyl)propenoate (5h): By following GP1, 3-
methoxybenzaldehyde (3h, 161 mg, 1.18 mmol), methyl bromoacet-
ate (4a, 217 mg, 1.42 mmol), 2-phenylisophosphindoline 2-oxide (2,
Methyl 3-(2-Furanyl)propenoate (5l): By following GP1, furan-2-
carbaldehyde (3l, 155 mg, 1.61 mmol), methyl bromoacetate (4a,
14 mg, 0.06 mmol), Na2CO3 (188 mg, 2.36 mmol), and HSi(OMe)3 296 mg, 1.93 mmol), 2-phenylisophosphindoline 2-oxide (2, 18 mg,
(288 mg, 2.36 mmol) were combined in toluene (2.4 mL). Purifica-
tion by flash chromatography (SiO2; cyclohexane/EtOAc, 10:1) af-
forded 5h (198 mg, 87%, E/Z, 83:17) as a yellowish oil. H NMR
(300 MHz, CDCl3, major isomer): δ = 3.82 (s, 3 H, CH3), 3.84 (s,
3 H, CH3), 6.44 (d, J = 16.0 Hz, 1 H, CH), 6.93–6.96 (m, 1 H,
ArH), 7.04–7.06 (m, 1 H, ArH), 7.12–7.14 (m, 1 H, ArH), 7.29–
0.08 mmol), Na2CO3 (256 mg, 2.41 mmol), and HSi(OMe)3
(393 mg, 3.22 mmol) were combined in toluene (3.2 mL). Purifica-
tion by flash chromatography (SiO2; cyclohexane/EtOAc, 5:1) af-
forded 5l (177 mg, 72%; E/Z, 71:29) as an orange oil. 1H NMR
(300 MHz, CDCl3, major isomer): δ = 3.79 (s, 3 H, CH3), 6.32 (d,
J = 15.7 Hz, 1 H, CH), 6.46–6.48 (m, 1 H, ArH), 6.60–6.63 (m, 1
1
7.34 (m, 1 H, ArH), 7.67 (d, J = 16.0 Hz, 1 H, CH) ppm. 13C NMR H, ArH), 7.44 (d, J = 15.7 Hz, 1 H, CH), 7.48–7.49 (m, 1 H,
(75 MHz, CDCl3, major isomer): δ = 51.5 (CH3), 55.1 (CH3), 112.9 ArH) ppm. 13C NMR (75 MHz, CDCl3, major isomer): δ = 51.6
(CH), 116.0 (CH), 117.9 (CH), 120.6 (CH), 129.7 (CH), 135.6 (C), (CH3), 112.2 (CH), 114.7 (CH), 115.3 (CH), 131.1 (CH), 144.7
144.6 (CH), 159.8 (C), 167.2 (C=O) ppm. MS (EI, 70 eV): m/z (%) (CH), 150.8 (C), 167.4 (C=O) ppm. MS (EI, 70 eV): m/z (%) = 152
= 192 (81) [M]+, 191 (20), 161 (100) [M+ – OMe], 133 (22) [M+
CO2Me], 118 (26), 90 (15), 89 (15), 77 (11).
–
(50) [M]+, 121 (100) [M+ – OMe], 65 (43).
Methyl 3-(2-Thienyl)propenoate (5m): By following GP1, 2-thienyl-
carbaldehyde (3m, 204 mg, 1.82 mmol), methyl bromoacetate (4a,
335 mg, 2.19 mmol), 2-phenylisophosphindoline 2-oxide (2, 21 mg,
0.09 mmol), Na2CO3 (289 mg, 2.73 mmol), and HSi(OMe)3
Methyl 3-(2-Methoxyphenyl)propenoate (5i): By following GP1, 2-
methoxybenzaldehyde (3i, 157 mg, 1.15 mmol), methyl bromoacet-
ate (4a, 262 mg, 1.71 mmol), 2-phenylisophosphindoline 2-oxide (2,
13 mg, 0.06 mmol), Na2CO3 (191 mg, 1.80 mmol), and HSi(OMe)3 (445 mg, 3.64 mmol) were combined in toluene (3.6 mL). Purifica-
(273 mg, 2.23 mmol) were combined in toluene (2.4 mL). Purifica-
tion by flash chromatography (SiO2; cyclohexane/EtOAc, 20:1) af-
forded 5i (144 mg, 65%, E/Z, 87:13) as a yellowish oil. H NMR
tion by flash chromatography (SiO2; cyclohexane/EtOAc, 5:1) af-
forded 5m (265 mg, 87%; E/Z, 86:14) as a reddish oil. 1H NMR
(300 MHz, CDCl3, major isomer): δ = 3.80 (s, 3 H, CH3), 6.25 (d,
J = 15.7 Hz, 1 H, CH), 7.04–7.08 (m, 1 H, ArH), 7.25–7.27 (m, 1
1
(300 MHz, CDCl3): δ = 3.81 (s, 3 H, CH3), 3.90 (s, 3 H, CH3), 6.55
(d, J = 16.2 Hz, 1 H, CH), 6.87–7.00 (m, 2 H, ArH), 7.33–7.39 (m, H, ArH), 7.37–7.39 (m, 1 H, ArH), 7.80 (dt, J = 15.7 Hz, J =
1 H, ArH), 7.50–7.53 (m, 1 H, ArH), 8.01 (d, J = 16.0 Hz, 1 H, 0.7 Hz, 1 H, CH) ppm. 13C NMR (75 MHz, CDCl3, major isomer):
CH) ppm. 13C NMR (75 MHz, CDCl3): δ = 51.4 (CH3), 55.27 δ = 51.5 (CH3), 116.3 (CH), 127.9 (CH), 128.3 (CH), 130.8 (CH),
(CH3), 111.0 (CH), 118.1 (CH), 120.5 (CH), 123.2 (C), 128.7 (CH),
137.1 (CH), 139.3 (C), 167.1 (C=O) ppm. MS (EI, 70 eV): m/z (%)
131.4 (CH), 140.1 (CH), 158.2 (C), 167.8 (C=O) ppm. MS (EI, = 168 (60) [M]+, 137 (100) [M – OMe]+, 109 (40) [M – CO2Me]+,
70 eV): m/z (%) = 192 (31) [M]+, 161 (100) [M+ – OMe], 118 (21), 65 (18).
105 (17). C11H12O3 (192.21): calcd. C 68.74, H 6.29; found C 68.54,
Methyl 3-(2-Benzofuranyl)propenoate (5n): By following GP1,
H 6.14.
benzofuran-2-carbaldehyde (3n, 250 mg, 1.71 mmol), methyl
3-(3-Methoxy)phenylpropene Nitrile (5j): By following GP1, 3-
methoxybenzaldehyde (3h, 208 mg, 1.53 mmol), bromoacetonitrile
(220 mg, 1.84 mmol), 2-phenylisophosphindoline 2-oxide (2, 14 mg,
0.06 mmol), Na2CO3 (197 mg, 1.86 mmol), and HSi(OMe)3
(303 mg, 2.48 mmol) were combined in toluene (2.9 mL). Purifica-
tion by flash chromatography (SiO2; cyclohexane/EtOAc, 10:1) af-
forded 5j (165 mg, 84%; E/Z, 83:17) as a colorless oil. 1H NMR
bromoacetate (4a, 314 mg, 2.05 mmol), 2-phenylisophosphindoline
2-oxide (2, 20 mg, 0.09 mmol), Na2CO3 (272 mg, 2.57 mmol), and
HSi(OMe)3 (418 mg, 3.42 mmol) were combined in toluene
(3.4 mL). Purification by flash chromatography (SiO2; cyclohexane/
EtOAc, 5:1) afforded 5n (269 mg, 78%; E/Z, 74:26) as a colorless
solid. 1H NMR (300 MHz, CDCl3, major isomer): δ = 3.83 (s, 3
H, CH3), 6.59 (d, J = 15.6 Hz, 1 H, CH), 6.90–6.95 (m, 1 H, ArH),
(300 MHz, CDCl3, major isomer): δ = 3.84 (s, 3 H, CH3), 5.88 (d, 7.22–7.28 (m, 1 H, ArH), 7.33–7.40 (m, 1 H, ArH), 7.45–7.52 (m, 1
J = 16.6 Hz, 1 H, CH), 6.94–7.14 (m, 3 H), 7.30–7.44 (m, 2
H) ppm. 13C NMR (75 MHz, CDCl3, major isomer): δ = 55.2
(CH3), 96.5 (CH), 112.3 (CH), 116.7 (CH), 118.0 (C), 119.8 (CH),
H, ArH), 7.54–7.61 (m, 2 H, ArH, CH) ppm. 13C NMR (75 MHz,
CDCl3, major isomer): δ = 51.7 (CH3), 111.1 (CH), 111.3 (CH),
118.3 (CH), 121.6 (CH), 123.2 (CH), 126.3 (CH), 128.2 (C), 131.3
130.0 (CH), 134.7 (C), 150.3 (CH), 159.8 (C) ppm. MS (EI, 70 eV): (CH), 152.1 (C), 155.4 (C), 167.0 (C=O) ppm. MS (EI, 70 eV): m/z
m/z (%) = 159 (100) [M]+, 158 (11), 131 (21), 130 (28), 129 (27), (%) = 202 (82) [M]+, 171 (100) [M+ – OMe], 143 (16) [M+
128 (14) [M+ – OMe], 116 (28), 102 (21), 89 (37), 63 (15). C10H9NO CO2Me], 115 (47), 89 (12). C12H10O3 (202.21): calcd. C 71.28, H
–
(159.19): calcd. C 75.45, H 5.70, N 8.80; found C 75.73, H 5.44, N
8.59.
4.98; found C 71.22, H 5.15.
Methyl 3-(2-Benzothiophenyl)propenoate (5o): By following GP1,
benzothiophene-2-carbaldehyde (3o, 146 mg, 0.90 mmol), methyl
Methyl 2-Methyl-3-(3-methoxyphenyl)propenoate (5k): By following
GP1, 3-methoxybenzaldehyde (3h, 206 mg, 1.51 mmol), methyl 2- bromoacetate (4a, 165 mg, 1.08 mmol), 2-phenylisophosphindoline
bromopropionate (307 mg, 1.84 mmol), 2-phenylisophosphindoline 2-oxide (2, 10 mg, 0.05 mmol), Na2CO3 (143 mg, 1.35 mmol), and
2-oxide (2, 17 mg, 0.07 mmol), Na2CO3 (240 mg, 2.26 mmol), and HSi(OMe)3 (220 mg, 1.80 mmol) were combined in toluene
HSi(OMe)3 (380 mg, 3.11 mmol) were combined in toluene
(2.9 mL). Purification by flash chromatography (SiO2; cyclohexane/
(1.8 mL). Purification by flash chromatography (SiO2; cyclohexane/
EtOAc, 10:1) afforded 5o (172 mg, 88%; E/Z, Ͼ99:1) as a colorless
EtOAc, 20:1) afforded 5k (168 mg, 54%; E/Z, 89:11) as a yellowish solid. 1H NMR (300 MHz, CDCl3): δ = 3.83 (s, 3 H, CH3), 6.32
oil. 1H NMR (300 MHz, CDCl3): δ = 2.13 (d, J = 1.5 Hz, 3 H,
(d, J = 15.6 Hz, 1 H, CH), 7.36–7.40 (m, 2 H, ArH), 7.47–7.48 (m,
CH3), 3.83 (s, 6 H, CH3), 6.86–6.91 (m, 1 H), 6.92–6.95 (m, 1 H),
1 H, ArH), 7.75–7.82 (m, 2 H, ArH), 7.86–7.92 (m, 1 H, CH) ppm.
6.98–7.02 (m, 1 H), 7.29–7.35 (m, 1 H), 7.67 (s, 1 H) ppm. 13C 13C NMR (75 MHz, CDCl3): δ = 51.8 (CH3), 119.0 (CH), 122.4
NMR (75 MHz, CDCl3): δ = 14.0 (CH3), 52.0 (CH3), 55.1 (CH3), (CH), 124.4 (CH), 124.8 (CH), 126.2 (CH), 128.7 (CH), 137.8
113.8 (CH), 115.0 (CH), 122.0 (CH), 128.4 (C), 129.3 (CH), 137.1
(CH), 139.4 (C), 139.5 (C), 140.1 (C), 166.9 (C=O) ppm. MS (EI,
3292
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© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2015, 3286–3295

Phospholane-Catalyzed Wittig Reaction
70 eV): m/z (%) = 218 (100) [M]+, 187 (94) [M+ – OMe], 159 (19) (300 MHz, CDCl3, major isomer): δ = 2.50–2.59 (m, 2 H, CH2),
[M+ – CO2Me], 158 (25), 115 (85), 79 (16).
2.76–2.82 (t, J = 7.7 Hz, 2 H, CH2), 3.74 (s, 3 H, CH3), 5.87 (dt, J
= 15.7 Hz, J = 1.6 Hz, 1 H, CH), 7.03 (dt, J = 15.7 Hz, J = 6.8 Hz,
1 H, CH), 7.17–7.25 (m, 3 H, ArH), 7.27–7.34 (m, 2 H, ArH) ppm.
13C NMR (75 MHz, CDCl3, major isomer): δ = 33.9 (CH2), 34.3
(CH2), 51.4 (CH3), 121.4 (CH), 126.1 (CH), 128.3 (2ϫ CH), 128.5
(2ϫ CH), 140.7 (C), 148.3 (CH), 167.0 (C=O) ppm. MS (EI,
70 eV): m/z (%) = 190 (1) [M]+, 158 (8) [M+ – OMe], 130 (15) [M+ –
CO2Me], 91 (100).
Methyl 3-(Quinolin-2-yl)propenoate (5p): By following GP1, quinol-
ine-2-carbaldehyde (3p, 295 mg, 1.88 mmol), methyl bromoacetate
(4a, 345 mg, 2.26 mmol), 2-phenylisophosphindoline 2-oxide (2,
21 mg, 0.09 mmol), Na2CO3 (299 mg, 2.82 mmol), and HSi(OMe)3
(459 mg, 3.76 mmol) were combined in toluene (3.8 mL). Purifica-
tion by flash chromatography (SiO2; cyclohexane/EtOAc, 10:1) af-
1
forded 5p (90 mg, 22%; E/Z, 95:5) as a yellowish solid. H NMR
Methyl Non-2-enoate (5t): By following GP1, heptanal (3t, 181 mg,
1.59 mmol), methyl bromoacetate (4a, 292 mg, 1.91 mmol), 2-phen-
ylisophosphindoline 2-oxide (2, 18 mg, 0.079 mmol), Na2CO3
(253 mg, 2.39 mmol), and HSi(OMe)3 (389 mg, 3.18 mmol) were
combined in toluene (3.2 mL). Purification by flash chromatog-
raphy (SiO2; cyclohexane/EtOAc, 10:1) afforded 5t (190 mg, 70%;
(300 MHz, CDCl3): δ = 3.86 (s, 3 H, CH3), 7.03 (d, J = 16.0 Hz, 1
H, CH), 7.56–7.60 (m, 1 H, ArH), 7.62–7.64 (m, 1 H, ArH), 7.74–
7.78 (m, 1 H, ArH), 7.82–7.85 (m, 1 H, ArH), 7.93 (d, J = 16.0 Hz,
1 H, CH), 8.13–8.16 (m, 1 H, ArH), 8.20–8.22 (m, 1 H, ArH) ppm.
13C NMR (75 MHz, CDCl3): δ = 51.9 (CH3), 120.3 (CH), 123.2
(CH), 127.3 (CH), 127.5 (CH), 128.0 (C), 129.8 (CH), 130.0 (CH),
136.7 (CH), 144.3 (CH), 148.2 (C), 153.0 (C), 166.9 (C=O) ppm.
MS (EI, 70 eV): m/z (%) = 213 (66) [M]+, 198 (16) [M+ – Me], 182
(85) [M+ – OMe], 155 (100), 154 (80) [M+ – CO2Me], 129 (32), 128
(64), 127 (18), 101 (22), 77 (30).
1
E/Z, 79:21) as a colorless oil. H NMR (300 MHz, CDCl3, major
isomer): δ = 0.86–0.92 (m, 3 H, CH3), 1.24–1.51 (m, 8 H, CH2),
2.16–2.24 (m, 2 H, CH2), 3.73 (s, 3 H, CH3), 5.82 (dt, J = 15.7 Hz,
J = 1.6 Hz, 1 H, CH), 6.98 (dt, J = 15.7 Hz, J = 7.0 Hz, 1 H,
CH) ppm. 13C NMR (75 MHz, CDCl3, major isomer): δ = 14.0
(CH3), 22.5 (CH2), 27.9 (CH2), 28.7 (CH2), 31.5 (CH2), 32.2 (CH2),
51.3 (CH3), 120.7 (CH), 149.5 (CH), 167.1 (C=O) ppm. MS (EI,
Methyl 5-(5-Methylfur-2-yl)hex-2-enoate (5q): By following GP1, 3-
(5-methylfur-2-yl)butanal (3q, 184 mg, 1.21 mmol), methyl bromo-
acetate (4a, 222 mg, 1.45 mmol), 2-phenylisophosphindoline
2-oxide (2, 14 mg, 0.06 mmol), Na2CO3 (296 mg, 1.82 mmol), and
HSi(OMe)3 (296 mg, 2.42 mmol) were combined in toluene
(2.4 mL). Purification by flash chromatography (SiO2; cyclohexane/
EtOAc, 5:1) afforded 5q (185 mg, 73%; E/Z, 79:21) as a yellow oil.
1H NMR (300 MHz, CDCl3, major isomer): δ = 1.25 (d, J =
7.0 Hz, 3 H, CH3), 2.26 (s, 3 H, CH3), 2.33–2.44 (m, 1 H, CH2),
2.55–2.65 (m, 1 H, CH2), 2.89–3.00 (m, 1 H, CH), 3.73 (s, 3 H,
CH3), 5.83–5.88 (m, 3 H, 2 ArH, CH), 6.87–6.97 (m, 1 H,
CH) ppm. 13C NMR (75 MHz, CDCl3, major isomer): δ = 13.4
(CH3), 18.5 (CH3), 32.3 (CH), 38.2 (CH2), 51.3 (CH3), 104.6 (CH),
105.6 (CH), 122.4 (CH), 147.0 (CH), 150.4 (C), 157.0 (C), 166.8
(C=O) ppm. MS (EI, 70 eV): m/z (%) = 208 (4) [M]+, 109 (100)
70 eV): m/z (%) = 139 (34) [M+ – OMe], 138 (32), 113 (37) [M+
–
C4H9], 101 (18), 100 (21), 96 (51), 87 (100), 81 (32), 74 (34), 69
(39), 55 (72).
Methyl Trideca-2,12-dienoate (5u): By following GP1, undec-10-
enal (3u, 249 mg, 1.48 mmol), methyl bromoacetate (4a, 272 mg,
1.78 mmol), 2-phenylisophosphindoline 2-oxide (2, 17 mg,
0.07 mmol), Na2CO3 (235 mg, 2.22 mmol), and HSi(OMe)3
(362 mg, 2.96 mmol) were combined in toluene (3.0 mL). Purifica-
tion by flash chromatography (SiO2; cyclohexane/EtOAc, 10:1) af-
1
forded 5u (220 mg, 66%; E/Z, 80:20) as a colorless oil. H NMR
(300 MHz, CDCl3, major isomer): δ = 1.25–1.50 (m, 12 H, CH2),
2.00–2.09 (m, 2 H, CH2), 2.16–2.24 (m, 2 H, CH2), 3.73 (s, 3 H,
CH3), 4.90–5.04 (m, 2 H, CH2), 5.75–5.89 (m, 2 H, CH), 6.98 (dt,
J = 15.6 Hz, J = 7.0 Hz, 1 H, CH) ppm. 13C NMR (75 MHz,
CDCl3, major isomer): δ = 27.9 (CH2), 28.8 (CH2), 29.0 (CH2),
29.0 (CH2), 29.2 (CH2), 29.3 (CH2), 32.1 (CH2), 33.7 (CH2), 51.2
(CH3), 114.1 (CH), 120.7 (CH), 139.0 (CH), 149.6 (CH), 167.1
(C=O) ppm. MS (EI, 70 eV): m/z (%) = 224 (1) [M]+, 150 (33), 142
(17), 135 (15), 121 (22), 113 (65), 109 (28), 100 (37), 95 (51), 87
(49), 81 (95), 67 (63), 55 (100), 41 (76).
[M+ – C H CO Me]. IR [attenuated total reflectance (ATR)]: ν =
˜
3
4
2
2951 (w), 1721 (vs), 1657 (m), 1613 (w), 1566 (w), 1436 (m), 1270
(m), 1216 (s), 1164 (vs), 1112 (m), 1019 (s), 957 (m), 940 (m), 780
(s), 720 (m) cm–1. HRMS (EI): calcd. for C12H16O3 208.1094; found
208.1090. C12H16O3 (208.26): calcd. C 69.21, H 7.74; found C
69.19, H 7.65.
Methyl 4,4-(Diphenyl)but-2-enoate (5r): By following GP1, di-
phenylacetaldehyde (3r, 330 mg, 1.68 mmol), methyl bromoacetate
(4a, 308 mg, 2.02 mmol), 2-phenylisophosphindoline 2-oxide (2,
19 mg, 0.08 mmol), Na2CO3 (267 mg, 2.52 mmol), and HSi(OMe)3
(411 mg, 3.36 mmol) were combined in toluene (3.3 mL). Purifica-
tion by flash chromatography (SiO2; cyclohexane/EtOAc, 20:1) af-
Methyl 5,7,7-Trimethyloct-2-enoate (5v): By following GP1, 3,5,5-
trimethylhexanal (3v, 213 mg, 1.50 mmol), methyl bromoacetate
(4a, 275 mg, 1.80 mmol), 2-phenylisophosphindoline 2-oxide (2,
17 mg, 0.08 mmol), Na2CO3 (238 mg, 2.25 mmol), and HSi(OMe)3
(367 mg, 3.00 mmol) were combined in toluene (3.0 mL). Purifica-
tion by flash chromatography (SiO2; cyclohexane/EtOAc, 10:1) af-
forded 5v (219 mg, 1.10 mmol, 74%; E/Z, 78:22) as a colorless oil.
1H NMR (300 MHz, CDCl3, major isomer): δ = 0.90 (s, 9 H, 3ϫ
CH3), 0.92–0.97 (m, 3 H, CH3), 1.00–1.31 (m, 2 H, CH2), 1.58–
1.77 (m, 1 H, CH), 2.00–2.32 (m, 2 H, CH2), 3.74 (s, 3 H, CH3),
5.82 (dt, J = 15.5 Hz, J = 1.5 Hz, 1 H, CH), 6.95 (dt, J = 15.6 Hz,
J = 7.5 Hz, 1 H, CH) ppm. 13C NMR (75 MHz, CDCl3, major
isomer): δ = 22.3 (CH3), 28.8 (CH), 29.8 (3ϫ CH3), 30.9 (C), 41.8
(CH2), 50.3 (CH2), 51.1 (CH3), 121.9 (CH), 148.3 (CH), 166.7
1
forded 5r (331 mg, 78%; E/Z, 95:5). H NMR (300 MHz, CDCl3,
major isomer): δ = 3.74 (s, 3 H, CH3), 4.90 (d, J = 7.3 Hz, 1 H,
CH), 5.76 (dd, J = 15.6 Hz, J = 1.5 Hz, 1 H, CH), 7.16–7.36 (m,
10 H, 10 ArH), 7.42–7.52 (m, 1 H, CH) ppm. 13C NMR (75 MHz,
CDCl3, major isomer): δ = 51.4 (CH3), 53.3 (CH), 122.4 (CH),
126.8 (2ϫ CH), 128.5 (4ϫ CH), 128.6 (4ϫ CH), 141.4 (2ϫ C),
150.1 (CH), 166.7 (C=O) ppm. MS (EI, 70 eV): m/z (%) = 252 (14)
[M]+, 221 (15) [M+ – OMe], 193 (93) [M+ – CO2Me], 192 (100),
191 (39), 178 (29), 165 (33), 115 (93), 91 (18).
(C=O) ppm. IR (ATR): ν = 2953 (m), 2905 (m), 2869 (w), 1724
˜
Methyl 5-Phenylpent-2-enoate (5s): By following GP1, 3-phenyl-
propanal (3s, 210 mg, 1.57 mmol), methyl bromoacetate (4a,
288 mg, 1.88 mmol), 2-phenylisophosphindoline 2-oxide (2, 18 mg,
0.08 mmol), Na2CO3 (250 mg, 2.36 mmol), and HSi(OMe)3
(384 mg, 3.14 mmol) were combined in toluene (3.1 mL). Purifica-
tion by flash chromatography (SiO2; cyclohexane/EtOAc, 20:1) af-
(vs), 1657 (m), 1468 (m), 1436 (m), 1395 (w), 1363 (m), 1309 (s),
1270 (w), 1226 (w), 1195 (s), 1162 (s), 1128 (m), 1101 (m), 1043
(m), 982 (s), 921 (m), 816 (m), 718 (m) cm–1. HRMS (EI): calcd.
for C12H22O2 198.1614; found 198.1617.
Methyl 6-(5,5-Dimethyl-1,3-dioxanyl)-hex-2-enoate (5w): By follow-
forded 5s (216 mg, 72%; E/Z, 83:17) as a colorless oil. 1H NMR ing GP1, 4-(5,5-dimethyl-1,3-dioxanyl)butanal (3w, 266 mg,
Eur. J. Org. Chem. 2015, 3286–3295
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3293

T. Werner, M. Hoffmann, S. Deshmukh
FULL PAPER
[5]
[6]
H. A. van Kalkeren, F. L. van Delft, F. P. J. T. Rutjes, Chem-
SusChem 2013, 6, 1615–1624.
1.43 mmol), methyl bromoacetate (4a, 262 mg, 1.72 mmol), 2-phen-
ylisophosphindoline 2-oxide (2, 16 mg, 0.07 mmol), Na2CO3
(227 mg, 2.15 mmol), and HSi(OMe)3 (349 mg, 2.86 mmol) were
combined in toluene (2.9 mL). Purification by flash chromatog-
raphy (SiO2; cyclohexane/EtOAc, 5:1) afforded 5w (243 mg, 70%;
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1
E/Z, 81:19) as a colorless oil. H NMR (300 MHz, CDCl3, major
isomer): δ = 0.71 (s, 3 H, CH3), 1.18 (s, 3 H, CH3), 1.53–1.72 (m,
4 H, CH2), 2.18–2.26 (m, 2 H, CH2), 3.38–3.44 (m, 2 H, OCH2),
3.56–3.61 (m, 2 H, OCH2), 3.71 (s, 3 H, CH3), 4.40–4.45 (m, 1 H,
CH), 5.82 (dt, J = 15.6 Hz, J = 1.6 Hz, 1 H, CH), 6.96 (dt, J =
15.6 Hz, J = 6.9 Hz, 1 H, CH) ppm. 13C NMR (75 MHz, CDCl3,
major isomer): δ = 21.6 (CH3), 22.1 (CH2), 22.8 (CH3), 29.9 (C),
31.8 (CH2), 34.0 (CH2), 51.1 (CH3), 77.0 (2ϫ CH2), 101.5 (CH),
121.0 (CH), 148.9 (CH), 166.8 (C=O) ppm. MS (EI, 70 eV): m/z
[7]
[8]
(%) = 242 (1) [M]+, 241 (8), 141 (21), 125 (52), 115 (100), [M+
C H O ], 97 (13), 81 (17), 69 (73), 56 (42). IR (ATR): ν = 2952
–
˜
7
11
2
(m), 2846 (w), 1721 (vs), 1656 (m), 1436 (m), 1394 (w), 1312 (m),
1270 (s), 1195 (s), 1165 (s), 1132 (vs), 1110 (s), 1039 (m), 1017 (s),
980 (s), 940 (w), 923 (m), 855 (m), 817 (m), 784 (s), 719 (m), 665
(m) cm–1. C13H22O4 (242.31): calcd. C 64.44, H 9.15; found C
64.06, H 9.18.
General Procedure (GP2) for the Asymmetric Catalytic Wittig Reac-
tion, Compound 7: A 15 mL Ace pressure tube that was equipped
with a stir bar was charged with the phosphane or phosphane oxide
(0.05 mmol, 5 mol-%), triketone 6 (0.5 m in toluene, 1.0 mmol,
1.0 equiv.), Na2CO3 (1.5 equiv., 1.5 mmol), and HSi(OMe)3
(2.0 mmol, 2.0 equiv.). The tube was then purged with argon and
sealed with an O-ring cap, and the reaction mixture was heated at
125 °C for 20 h. After cooling to 23 °C, the reaction mixture was
filtered through a short plug of silica (ethyl acetate) and then puri-
fied by flash column chromatography [SiO2; cyclohexane/ethyl
acetate (EtOAc)].
Synthesis of (R)-Bis-nor Wieland–Miescher Ketone (R-7): By fol-
lowing GP2, (1R,1ЈR,2S,2ЈS)-2,2Ј-di-tert-butyl-2,3,2Ј,3Ј-tetra-
hydro-1H,1ЈH-(1,1Ј)biisophosphindolyl [(R,R,S,S)-DuanPhos, 13,
10 mg, 0.026 mmol, 5 mol-%), Na2CO3 (80 mg, 0.75 mmol), carb-
onyl compound 6 (128 mg, 0.518 mmol), and HSi(OMe)3 (125 mg,
1.02 mmol) were combined in toluene (1.1 mL). Purification by
flash chromatography (SiO2; cyclohexane/EtOAc, 1:1) afforded
product (R)-7 (39 mg, 50%, 62%ee) as a colorless oil. 1H NMR
(300 MHz, CDCl3): δ = 1.35 (s, 3 H, CH3), 2.28–2.64 (m, 3 H,
CH2), 2.91–3.20 (m, 3 H, CH2), 5.97 (s, 1 H, CH) ppm. 13C NMR
(75 MHz, CDCl3): δ = 23.2 (CH3), 24.4 (CH2), 38.3 (CH2), 44.7
(CH2), 56.7 (C), 126.1 (CH), 184.7 (C), 207.6 (C=O), 212.5
(C=O) ppm.
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Received: February 18, 2015
Published Online: April 17, 2015
Eur. J. Org. Chem. 2015, 3286–3295
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3295