Silicon assisted diversified reaction of a β-silylmethylene malonate with dimethylsulfoxonium methylide

Article abstract of DOI:10.1016/j.jorganchem.2008.11.005

Reaction of dimethylsulfoxonium methylide with a β-silylmethylene malonate gives diversified products, cyclopropane, cyclobutane or allyl and homoallyl silanes depending upon the stoichiometry of the reactants and reaction conditions. Contrary to this, re

Full text of DOI:10.1016/j.jorganchem.2008.11.005

Journal of Organometallic Chemistry 694 (2009) 382–388
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Silicon assisted diversified reaction of a b-silylmethylene malonate with
dimethylsulfoxonium methylide
*
Pintu K. Kundu, Rekha Singh, Sunil K. Ghosh
Bio-Organic Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Reaction of dimethylsulfoxonium methylide with a b-silylmethylene malonate gives diversified products,
cyclopropane, cyclobutane or allyl and homoallyl silanes depending upon the stoichiometry of the reac-
tants and reaction conditions. Contrary to this, reaction of a b-arylmethylene malonate gives only the
cyclopropane product. The product(s) formed are unique and the silicon group played a crucial role either
by assisting and/or by participating in the process.
Received 24 September 2008
Received in revised form 30 October 2008
Accepted 3 November 2008
Available online 7 November 2008
Ó 2008 Elsevier B.V. All rights reserved.
Keywords:
Cyclobutane
Dimethylsulfoxonium methylide
b-Silylmethylene malonate
Allylsilane
1. Introduction
affinity for fluorine and oxygen, which makes the silicon chemistry
highly selective as exemplified in Brook rearrangement [31–33]
The unique properties of silicon [1,2] have led to its wide utili-
zation in organic chemistry ranging from protecting functional
groups [3], forming temporary tether [4–6] and masking hydroxyl
group [7,8], to highly controlled and selective organic reactions
[1,2,9]. The stabilization of either an electron deficient center such
as a carbocation at the b-position (b-effect) [10–12] or a carbanion
and cross-coupling reactions [34–38].
Sulfonium and sulfoxonium ylides [39–43] are extensively used
in organic chemistry to achieve the stepwise insertion of a methy-
lene or a substituted methylene across the double bond of a car-
bonyl, an imine, or an electrophilic olefin to yield an oxirane, an
aziridine, or a cyclopropane, respectively. Besides their difference
in stability, the outcomes of many reactions with these ylides are
similar, although, some notable differences in their reactivity and
selectivity are also reported [44]. Recently, we and others have
shown that dimethylsulfonium methylide (DIMSY) (1) when used
in excess, or in the presence of a base can act as an equivalent of
a carbenoid to produce interesting product(s) when reacted with
various Michael acceptors [45–52], activated dienes [53], carbonyl
compounds, imines and epoxides [54–57]. For example, when
DIMSY was reacted with b-silylmethylene or b-arylmethylene mal-
onates 2, cyclopropane derivatives 3 or olefins 4 were obtained
[45–52] depending upon the quantities of the ylide and base used
(Scheme 1).
We were therefore interested to know if excess dimethylsul-
foxonium methylide (DIMSOY) (5) would react in similar fashion
with b-silylmethylene malonate 2a (R = SiMe2Ph, E = CO2Et). Inter-
estingly, when excess DIMSOY, generated from the reaction of
trimethylsulfoxonium iodide and sodium hydride in dimethyl sulf-
oxide (DMSO) was reacted with the b-silylmethylene malonate 2a
at room temperature, the expected cyclopropane 3a was formed
albeit in moderate yield, associated with two unusual products
viz. cyclobutane 6a and the allylated malonate 7 (Scheme 2). How-
ever, when stoichiometric quantity of the ylide 5 was used, besides
at the
a-position (a-effect) [13] with respect to a silicon group is
the central theme of organosilicon chemistry, applied to organic
synthesis. The former effect is clearly demonstrated by the en-
hanced rates of unimolecular solvolysis [14] of b-(trimethylsilyl)
esters compared to the corresponding silicon-free analogues. The
regio- and stereo-selectivity of electrophilic substitution reactions
[9,15] of allyl-, vinyl- and aryl-silanes have been shown to be con-
trolled by the b-effect. This stabilizing effect also plays an impor-
tant role in directing the regioselectivity in various organic
reactions. Some recent examples include Baeyer–Villiger oxidation
[16], Bamford–Stevens reaction [17], Beckmann fragmentation
[18,19], Curtius reaction [20], Norrish types I and II cleavages
[21,22], palladium-catalyzed nucleophilic substitution [23],
Nazarov cyclizations [24,25], decarboxylation reactions [26] and
stereospecific 1,2-silyl shifts [27,28]. The propensity of b-elimina-
tion of organosilicon compounds was first demonstrated by
Peterson [29,30] for olefin synthesis. The starting b-silyl alcohols
were conveniently prepared by the reaction of a stabilized a-silyl
carbanion with carbonyl compounds. Besides, silicon has unique
* Corresponding author. Tel.: +91 22 25595012; fax: +91 22 255055151.
E-mail address: ghsunil@barc.gov.in (S.K. Ghosh).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.11.005

P.K. Kundu et al. / Journal of Organometallic Chemistry 694 (2009) 382–388
383
Table 1
R
CO2Et
CO2Et
Me2S=CH2 (1)
(1 equiv)
Optimization of conditions for the synthesis of cyclobutane 6a.
3
3a:6a:7a
% Yield of 3a+6ab
R
CO2Et
CO2Et
Entry
Me3S(O)I
(equiv.)
Base (equiv.)
Solvent
1
2
3
4
5
6
7
8
2
NaH (2)
NaH (2.5)
NaH (2.5)
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMF
24:41:35
49:2:49
28:4:68
17:83:0
13:87:0
12:88:0
13:87:0
68:32:0
43:57:0
59:41:0
12:88:0
34c
ndd,e
ndd,f
60
71
69
69
19
61
60
2
R
CO2Et
CO2Et
under different
2.5
2.5
2
2.5
3
2.5
2.5
2.5
2.5
2.5
1
R = SiMe2Ph, Ar
(excess
or base)
LiOBu-t (2)
LiOBu-t (2.5)
LiOBu-t (3)
LiOBu-t (2.5)
LiOBu-t (2.5)
NaOBu-t (2.5)
KOBu-t (2.5)
LiOBu-t (2.5)
4
Scheme 1. Reaction of some Michael acceptors with ylide
1
conditions.
THF
9
10
11
DMSO
DMSO
DMSO
cyclopropane 3a, a pair of new products, an allylsilane 8a and its
regioisomeric homoallylsilane 9a were formed (Scheme 2). The
diversified products formed under different conditions therefore
challenged us to formulate conditions for individual products.
We report, herein, the conditions developed for two interesting
groups of products, cyclobutane and allyl/homoallylsilane with
very high selectivity merely by adjusting the stoichiometry of the
ylide and reaction conditions.
73
Ratios determined by 1H NMR from the crude product.
a
b
c
d
e
f
All the reactions (except entries 2 and 3) were performed at 20 °C.
20% of 7 was also isolated.
Yield not determined.
Reaction was performed at À10 °C.
Reaction was performed at 50 °C.
2. Results and discussion
to substantial formation of the undesired byproduct 7 at the ex-
pense of the target cyclobutane 6a (Table 1, entries 2 and 3).
Changing the base to LiOBu-t (generated from n-butyl lithium
and tert-butanol) in DMSO improved the product yield with over-
whelming preference for the cyclobutane 6a. Amongst the solvents
studied, N,N-dimethyl formamide (DMF) showed comparable
yields and selectivity. The cation in the base had a dramatic influ-
ence on the selectivity of the formation of cyclobutane 6a over
cyclopropane 3a, and increased in the order Li > Na > K. Hence,
the best condition was to use 2.5 equiv. each of LiOBu-t and trim-
ethylsulfoxonium iodide with respect to malonate 2a in DMSO at
20 °C, which gave cyclobutane 6a and cyclopropane 3a
(3a:6a = 13/87) in 71% isolated yield (Table 1, entry 5). Increasing
the amount of ylide 5 beyond 2.5 equiv. neither enhance the yield
nor selectivity (Table 1, entry 6). The effect of counter ion in the
trimethylsulfoxonium salt did not have much impact since the
reaction with trimethylsulfoxonium chloride proceeded with sim-
ilar yield and selectivity (Table 1, entry 11).
To see the generality of this synthetic strategy, we prepared two
more silylmethylene malonates 2b,c. The dimethyl(trimethylsilyl-
oxy)silyl substituted methylene malonate 2b was prepared in 58%
yield from 2a by a selective protiodephenylation of the phenyldim-
ethylsilyl group with trifluromethanesulfonic acid in dichloro-
methane followed by mixed disiloxane formation by adding
excess trimethylsilyl chloride to the reaction mixture and then
quenching with ammonium hydroxide (Scheme 3). For the prepa-
ration of di-tert-butyloxy(phenyl)silyl substituted methylene mal-
onate 2c, we adopted a procedure similar to the preparation of 2a.
Therefore, the known di-tert-butyloxy(phenyl)silyl lithium was
prepared from the corresponding silyl chloride [62,63], and reacted
with diethyl ethoxymethylene malonate in THF to give 2c in mod-
erate yield (Scheme 4).
2.1. Preparation of cyclobutane derivative
Cyclobutanes have been known for more than a century but
their use as synthetic intermediates has gained popularity very re-
cently [58–61]. The reactivity of cyclobutane derivatives is due to
their inherent ring strain. The regioselectivity of bond cleavage in
cyclobutane is decided by the ring substituents, reagents and con-
ditions. Although cyclobutane systems are more commonly pre-
pared by cycloaddition, cyclopropane ring expansion and ring
contraction reactions, synthesis of suitably functionalized deriva-
tives is still challenging. We, therefore, first aimed to establish
the optimized conditions for the preparation of the silicon func-
tionalized cyclobutane derivative 6a. To this end, we carried out
the reactions of 2a with DIMSOY, generated from trimethylsulfoxo-
nium iodide under different conditions and the results are pre-
sented in presented in Table 1. The reaction of 2a with 2 equiv.
of DIMSOY, generated using sodium hydride as base in DMSO at
20 °C provided the cyclopropane 3a associated with a significant
amount of cyclobutane 6a and the allylated malonate 7 in moder-
ate yield (Table 1, entry 1). Further increase in the DIMSOY quan-
tity or changing the temperature did not improve the yield, but led
CO2Et
CO2Et
CO2Et
PhMe2Si
CO2Et
CO2Et
PhMe2Si
+
+
CO2Et
3a
7
6a
2a
DIMSOY (5)
(excess)
PhMe2Si
CO2Et
CO2Et
When 2b was reacted with DIMSOY, generated under the opti-
mized conditions (Table 1, entry 5), a mixture of cyclopropane 3b
and cyclobutane 6b were formed in moderate yield and selectivity
(3b:6b = 1/2) (Scheme 5). Under these conditions, silylmethylene
(1 equiv)
5
SiMe2Ph
SiMe2Ph
EtO2C
CO2Et
1. CF3SO3H,
EtO2C
CO2Et
(Me3SiO)Me2Si
CO2Et
+
CH2Cl2, -10 oC
PhMe2Si
CO2Et
CO2Et
CO2Et
CO2Et
CO2Et
9a
CO2Et
CO2Et
2. Me3SiCl
3. NH4OH
8a
2a
2b
Scheme 2. Reaction of b-silylmethylene malonate 2a with ylide 5 under different
conditions.
Scheme 3. Preparation of silylmethylene malonate 2b.

384
P.K. Kundu et al. / Journal of Organometallic Chemistry 694 (2009) 382–388
malonate 2c also reacted with DIMSOY to give a mixture of cyclo-
propane 3c and cyclobutane 6c. In this case, there was a reversal of
selectivity wherein cyclopropane 3c was formed as the major
product (3c:6c = 7/3) (Scheme 5). This suggested a crucial role of
the silyl substituents on the course of the reaction.
R'2RSi
CO2Et
CO2Et
R'2RSi
CO2Et
CO2Et
a
2
Me2(O)S
b
H2C S(O)Me2
Me2(O)S CH2
To find the role played by the silicon group in these reactions,
the arylidene malonate 2d, was reacted with varying amounts of
DIMSOY, generated from the corresponding iodide and base. In
all the cases, no trace of cyclobutane or the dimerization products
was observed. The cyclopropane 3d was the sole product associ-
ated with the unreacted starting material in cases where substoi-
chiometric quantity of ylide 5 was used (Scheme 6).
10
path-a
- DMSO
R'2RSi
path-b
- DMSO
CO2Et
CO2Et
3
H2C S(O)Me2
excess
X
These results, unambiguously established the vital role of the si-
lyl group in the malonates 2a–c in governing the pathway of the
reaction. Evidently, the cyclobutane 6a, formed in the reaction of
2a with excess DIMSOY was not produced via the cyclopropane
intermediate. In separate experiments, cyclopropane 3a was found
to be unreactive to the ylide 5 even when treated in large excess.
Although, cyclopropanes are known not to react with excess DIM-
SOY to give cyclobutanes, DIMSOY can add to epoxides and suit-
ably N-protected aziridines under harsh conditions to give
oxetanes [64–68] and azetidines [69,70] or other products
[71–76], depending on the other functionalities present on the
substrates. A plausible mechanism for the formation of cyclobu-
tane products from silyl substituted methylene malonates 2 is
delineated in Scheme 7. The nucleophilic addition of DIMSOY on
the b-silylalkylidene malonate 2 produced the intermediate 10
which can give the cyclopropane 3 by loss of DMSO (path-a). As
the silicon group is known to facilitate nucleophilic substitution
b-to it, the other favorable pathway (path-b) was the nucleophilic
R'2RSi
CO2Et
CO2Et
CO2Et
CO2Et
R'2RSi
- DMSO
Me2(O)S
11
6
Scheme 7. Plausible mechanism for the formation of cyclobutane 6.
displacement of DMSO on 10 by ylide 5 to give the intermediate
11, which on intramolecular cyclization provided the cyclobutane
6 with expulsion of DMSO. As the silicon group becomes larger,
path-b becomes unfavorable owing to the steric effect. This was
clearly manifested in case of 2c where cyclopropane 3c was ob-
tained as the major product.
Although diethyl allylmalonate 7 can be readily prepared from
diethyl malonate and allyl bromide, its formation in the reaction
of silymethylene malonates 2 with excess DIMSOY is somewhat
unusual. It is well established that cyclopropylmethyl halides,
cyclobutyl halides and homoallyl halides are all in equilibrium in
acid solutions and the mixture of products are often formed via
delocalized cationic intermediate [77–87]. But, under present cir-
cumstances, this situation is unlikely. We believe that the silyl
group plays an important role in this reaction also. We propose that
the malonate 7 is also formed from the intermediate anion 11 as de-
picted in Scheme 8. The enolate form of 11 probably formed a pen-
EtO
CO2Et
CO2Et
(t-BuO)2PhSiLi
(t-BuO)2PhSi
CO2Et
CO2Et
THF, -78 to 0 oC
2c 53%
Scheme 4. Preparation of silylmethylene malonate 2c.
tacoordinated silicate [88,89] species 12 which facilitated a c-silyl
group assisted (neighboring group participation) [90,91] loss of
DMSO to give a primary carbocation that initiated a 1,2-hydride
shift induced 1,3-silyl shift to give a b-silicon stabilized cationic
intermediate 13. Loss of silyl group from it then yields 7.
R'2RSi
CO2Et
CO2Et
Me3S(O)I + t-BuOLi
R = OSiMe3, R' = Me; 3b
R = Ph, R' = t-BuO; 3c
2.2. Preparation of allyl and homoallylsilanes
R'2RSi
Me2S(O)=CH2 (5)
2.5 equiv
CO2Et
CO2Et
+
Next, we turned our attention towards the preparation of the
functionalized allylsilane 8a, obtained by the same reaction under
DMSO, 20oC
R'2RSi
CO2Et
CO2Et
R = OSiMe3, R' = Me; 2b
R = Ph, R' = t-BuO; 2c
65-73%
O
R = OSiMe3, R' = Me; 6b
R = Ph, R' = t-BuO; 6c
O
R'2RSi
1,2-shift
OEt
R'2RSi
OEt
Scheme 5. Reaction of b-silylmethylene malonates 2b and 2c with ylide 5 to give
6b and 6c.
H
CO2Et
1,3-shift
CO2Et
Me2(O)S
Me2(O)S
11
12
Me3S(O)I + t-BuOLi
OMe
OMe
CO2Et
OEt
Me2S(O)=CH2 (5)
2.5 equiv
CO2Et
+
CO2Et
CO2Et
CO2Et
CO2Et
DMSO, 20oC
72%
O
CO2Et
Si
R
3d
R'
R'
7
2d
13
Scheme 6. Reaction of b-arylmethylene malonate 2d with ylide
cyclopropane 3d.
5 to give
Scheme 8. Plausible mechanism for the formation of allylated malonate 7.

P.K. Kundu et al. / Journal of Organometallic Chemistry 694 (2009) 382–388
385
Table 2
3. Conclusion
Optimization of conditions for the synthesis of olefins 8a and 9a from 2a using
1.1 equiv. of t-BuOLi and 0.5 equiv. of trimethylsulfoxonium iodide.
In conclusion, we have illustrated for the first time the reaction
of silymethylene malonates with DIMSOY, which produces diversi-
fied products depending upon the stoichiometry of the reactants
and reaction conditions. The product(s) formed are unique, and
the silicon group played crucial role either by assisting and/or by
participating in the process. The cyclopropanes, cyclobutanes, allyl
and homoallyl silanes, produced in this method have synthetic
potentials as the chemistry of these classes of molecules is well
established. In addition, the present work also exemplified the un-
ique difference of reactivity of DIMSOY and DIMSY with silymeth-
ylene and /or arylmethylene malonates.
Entry
Solvent (temp)
% Yield of 8a+9aa
% Yield of 3ab
1.
2.
3.
4.
5.
DMSO (5 °C)
DMF (15 °C)
DMF (5 °C)
DMF (0 °C)
NMP (5 °C)
55
58
65
51
67
13
11
12
11
11
a
Refers to combined isolated yield.
Product contaminated with 8–10% of 6a.
b
4. Experimental
PhMe2Si
Me2(O)S
CO2Et
CO2Et
PhMe2Si
CO2Et
4.1. Materials and methods
CO Et
2a
2
10
H2C S(O)Me2
CO2Et
CO2Et
All reactions were performed in oven-dried (120 °C) or flame-
dried glass apparatus under dry N2 or argon atmosphere. Tetrahy-
drofuran (THF) was dried from sodium/benzophenone while
t-BuOH, DMSO, DMF and NMP were dried from CaH2 followed by
storage over 4 Å molecular sieves. n-BuLi (1.5 M in hexane), Me3-
S(O)I and Me3SI were purchased from Aldrich. Compounds 2a and
2d were prepared following our reported procedure [46]. The col-
umn chromatography was performed on silica gel (230–400 mesh).
1H NMR and 13C NMR spectra were recorded with a Bruker 200 and
500 MHz spectrometers. Spectra were referenced to residual chlo-
roform (d 7.25 ppm, 1H; d 77.00 ppm, 13C). The mass spectra were
recorded on a Shimadzu GC–MS 2010 mass spectrometer (EI
70 eV). High resolution mass spectra were recorded at 60–70 eV
with a Waters Micromass Q-TOF spectrometer (ESI, Ar). Infrared
spectra (IR) were recorded on a JASCO FT IR spectrophotometer in
NaCl cells or in KBr discs. Peaks are reported in cmÀ1. Melting points
(mp) were determined on a Fischer John’s melting point apparatus
and are uncorrected. Gas chromatography (GC) studies were carried
out using Younglin Acme 6000 M Gas Chromatograph fitted with a
capillary column (WCOT Fused Silica, CP-SIL-5-CB, 50 m  0.25
t-BuOLi
PhMe2Si
PhMe2Si
Me2(O)S
PhMe2Si
Me2(O)S
EtO2C
CO2Et
CO2Et
CO2Et
CO2Et
CO2Et
14
SiMe2Ph
CO2Et
PhMe2Si
CO2Et
15
-DMSO
-SiMe2Ph
SiMe2Ph
SiMe2Ph
EtO2C
CO2Et
EtO2C
CO2Et
CO2Et
8a
CO2Et
CO2Et
9a
CO2Et
Scheme 9. Plausible mechanism for the formation of allylsilane 8a and homoall-
ylsilane 9a.
mm/0.39 mm, 0.25 lm; carrier: helium 1 mL/min).
stoichiometric condition (Scheme 2). Allylsilanes are important
intermediates in organic synthesis and their use in stereocon-
trolled organic reactions are well documented [9,92–96]. The
homoallylsilane 9a and the allylsilane 8a are essentially labile ole-
fin regioisomers, and are interconvertible under mild conditions.
Their structures suggest that these products are formed from two
molecules of malonate 2a. Therefore, while optimization, the ylide
quantity was reduced to half that of the malonate 2a. A large num-
ber of reaction conditions were tried to optimize the formation of
8a and/ or 9a as presented in Table 2. The reactions were per-
formed using 0.5 equiv. of DIMSOY generated from 0.5 equiv. of
trimethylsulfoxonium iodide and 1.1 equiv. of t-BuOLi (with re-
spect to 2a) at a temperature range of 0–15 °C using different sol-
vents like DMSO, DMF and N-methyl pyrrolidone (NMP). The best
result was obtained by carrying out the reaction with 0.5 equiv.
of ylide 5 in DMF or NMP at 5 °C (Table 2, entries 3 and 5).
The formation pathway of allylsilane from b-silylalkylidene
malonate 2a under substoichiometric amount of ylide and stoichi-
ometric amount of base is exemplified in Scheme 9. The ylide 5
adds to malonate 2a to give the adduct 10 from which the base ab-
stracts a proton to generate a new ylide 14. This, in turn, reacts
with another molecule of malonate 2a to give the intermediate
15. A Peterson type olefination with elimination of PhMe2Si and
Me2S(O)+ groups afforded the allylsilane 8a. The homoallylsilane
9a is then formed by base induced double bond isomerization of
the allysilane.
4.2. Diethyl dimethyl(trimethylsilyloxy)silylmethylene malonate (2b)
Trifluoromethanesulfonic acid (4.3 mL, 49 mmol, 5 equiv.) was
added to a stirred solution of 2a (3 g, 9.8 mmol) in dry CH2Cl2
(15 mL) at À2 °C. After 10 min, chlorotrimethylsilane (12.5 mL,
98 mmol, 10 equiv.) was added to the reaction mixture. The reac-
tion mixture was poured into ice-cold saturated NH4OH solution
(100 mL) and extracted with CHCl3. The organic extract was dried
over anhydrous sodium sulfate and evaporated under reduced
pressure. The residue was purified by chromatography to give 2b
(1.8 g, 58%) as colorless oil. Rf = 0.58 (hexane/EtOAc, 95:5); IR (film,
cmÀ1): 2982, 2958, 2904, 1732, 1370, 1318, 1254, 1198, 1051, 844,
809, 754, 691; 1H NMR (200 MHz, CDCl3): d À0.02 (s, 9H, Me3SiO),
3
0.13 (s, 6H, Me2Si), 1.18 (t, 3H, JHH = 6 Hz, OCH2CH3), 1.20 (t, 3H,
3
3JHH = 6 Hz, OCH2CH3), 4.13 (q, 2H, JHH = 6 Hz, OCH2CH3), 4.15 (q,
3
2H, JHH = 6 Hz, OCH2CH3), 6.99 (s, 1H, SiCH@C); 13C NMR
(50 MHz, CDCl3): d 0.46 (2C), 1.55 (3C), 13.73 (2C), 60.91, 61.11,
140.11, 149.36, 163.78, 165.5; ESI-MS: m/z (relative intensity)
341 (43, [M+Na]+), 201(16), 155 (10), 83 (100); HRMS Calc. for
C13H26O5Si2Na [M+Na]: 341.1217. Found 341.1219.
4.3. Diethyl di-tert-butyloxy(phenyl)silylmethylene malonate (2c)
Di-tert-butyloxy(phenyl)silyl lithium was prepared following
the procedure reported in the literature [63]. For this di-tert-butyl-

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P.K. Kundu et al. / Journal of Organometallic Chemistry 694 (2009) 382–388
oxy(phenyl)silyl chloride [62] (8.5 g, 29.6 mmol) was added to a
stirred suspension of lithium metal (830 mg, 0.118 g atom) in
THF (30 cm3) at room temperature under argon. After 40 min, the
reaction mixture was cooled to 0 °C and stirred for 4 h. This deep
red silyl lithium solution was slowly cannulated to a stirred solu-
tion of diethyl ethoxymethylene malonate (6.5 mL, 32.6 mmol,
1.1 equiv.) in THF (30 mL) at –78 °C over 15 min. After the addition
was over, the reaction mixture was stirred for 30 min and the cold
bath was removed. The reaction mixture was allowed to attain to
room temperature (about 25 min) and poured into saturated
ammonium chloride solution, extracted with Et2O. The organic ex-
tract was washed with water and with brine, dried over anhydrous
MgSO4 and evaporated. The residue was purified by column chro-
matography on silica using hexane/EtOAc (95/5) to give the diester
2c (6.6 g, 53%) as colorless oil. Rf = 0.62 (hexane/EtOAc, 5:95); IR
(film, cmÀ1): 3070, 2978, 1731, 1615, 1390, 1366, 1331, 1235,
1119, 1046, 899, 870, 830; 1H NMR (200 MHz, CDCl3): d 1.13 (t,
167.94, 170.14; ESI-MS: m/z (relative intensity) 357 (100,
[M+Na]+), 243 (6), 201 (16), 135 (10), 111 (6); HRMS Calc. for
C18H22O4SiNa [M+Na]: 357.1498. Found 357.1505. Compound 7:
Rf = 0.58 (hexane/EtOAc, 95:5); IR (film, cmÀ1): 3082, 2984, 2939,
1733, 1644, 1466, 1370, 1336, 1237, 1178, 1033, 916, 856, 733;
3
1H NMR (200 MHz, CDCl3):
d
1.25 (t, 6H, JHH = 7.2 Hz,
3
2 Â OCH2CH3), 2.63 (t, 2H, JHH = 7.6 Hz, CH2@CHCH2), 3.41 (t, 1H,
3JHH = 7.6 Hz, CH(CO2Et)2), 4.18 (q, 4H, 3JHH = 7.2 Hz, 2 Â OCH2CH3),
3
3
5.04 (d, 1H, JHH = 9.6 Hz, C@CHAHB), 5.10 (d, 1H, JHH = 16.8 Hz,
C@CHAHB), 5.67–5.84 (m, 1H, H2C@CH–); 13C NMR (50 MHz,
CDCl3): d 13.90 (2C), 32.65, 51.47, 61.21 (2C), 117.31, 133.94,
168.74 (2C).
4.5. Reaction of 2a with 2.5 equiv. of 5 using lithium tert-butoxide as
base
Dry t-BuOH (0.26 mL, 2.7 mmol) was added dropwise to n-BuLi
(1.7 mL, 1.5 M solution in hexane, 2.5 mmol) under argon atmo-
sphere. The solvent was removed under vacuum and the residue
was dissolved in dry DMSO (2 mL). The solution was cooled to
20 °C and solid trimethylsulfoxonium iodide (550 mg, 2.5 mmol)
was added into it. After 20 min, a solution of 2a (306 mg, 1 mmol,
1 equiv.) in dry DMSO (1 mL) was added slowly (10 min) to the
reaction mixture. The reaction mixture was stirred at room tem-
perature for 30 min and diluted with water (50 mL), extracted with
5% ethyl acetate in hexane (3 Â 30 mL). The combined extract was
washed with brine, dried over anhydrous magnesium sulfate and
concentrated under reduced pressure. The residue was purified
by column chromatography on silica using hexane/EtOAc (97/3)
to give the pure cyclopropane 3a (25 mg, 8%) and cyclobutane 6a
(210 mg, 63%).
3
3
3H, JHH = 7 Hz, OCH2CH3), 1.29 (t, 3H, JHH = 7 Hz, OCH2CH3), 1.29
3
(s, 18H, OBu-t), 3.89 (q, 2H, JHH = 6 Hz, OCH2CH3), 4.23 (q, 2H,
3JHH = 6 Hz, OCH2CH3), 7.12 (s, 1H, SiCH@C), 7.28–7.37 (m, 3H,
Ar), 7.62–7.67 (m, 2H, Ar); 13C NMR (50 MHz, CDCl3): d 13.43,
13.75, 31.62 (6C), 60.48, 61.24, 73.88 (2C), 127.22 (2C), 129.58,
134.38 (2C), 135.30, 140.99, 143.45, 163.44, 165.57; ESI-MS: m/z
(relative intensity) 445 (17, [M+Na]+), 349 (23), 265 (100), 219
(47), 147 (23); HRMS Calc. for C22H34O6SiNa [M+Na]: 445.2022.
Found: 445.2026.
4.4. Reaction of 2a with 2.5 equiv. of 5 using sodium hydride as base
Sodium hydride (96 mg, 50% in oil, 2 mmol, 2 equiv.) was made
oil free by washing with dry hexane and dry DMSO (2 mL) was
added into it. Trimethylsulfoxonium iodide (440 mg, 2 mmol,
2 equiv.) was added and the suspension was stirred under argon
atmosphere for 30 min. The solution was cooled to 20 °C and a
solution of 2a (306 mg, 1 mmol, 1 equiv.) in dry DMSO (1 mL)
was added slowly (10 min) to the reaction mixture. The reaction
mixture was stirred at room temperature for 30 min and diluted
with water (50 mL), extracted with 5% ethyl acetate in hexane
(3 Â 30 mL). The combined extract was washed with brine, dried
over anhydrous magnesium sulfate and concentrated under re-
duced pressure. The residue was purified by column chromatogra-
phy on silica using hexane/EtOAc (97/3) to give the pure
cyclopropane 3a [46] (42 mg, 13%), cyclobutane 6a (70 mg, 21%)
and malonate 7 [97] (40 mg, 20%). Compound 3a: Rf = 0.49 (hex-
ane/EtOAc, 95:5); IR (film, cmÀ1): 1731, 1249, 1116; 1H-NMR
(200 MHz, CDCl3): d 0.25 (s, 3H, SiMe), 0.34 (s, 3H, SiMe), 1.10
4.6. Reaction of 2b with 2.5 equiv. of 5 using lithium tert-butoxide as
base
Following the procedure described for the reaction of 2a with
ylide 5, trimethylsulfoxonium iodide (550 mg, 2.5 mmol), t-BuOH
(0.26 mL, 2.7 mmol), n-BuLi (1.7 mL, 1.5 M solution in hexane,
2.5 mmol) and 2b (318 mg, 1 mmol, 1 equiv.) gave a mixture of
cyclopropane 3b and cyclobutane 6b (220 mg, 65%; 3b:6b = 1/2
by 1H NMR) which could not be separated. Compounds 3b and
6b mixture: Rf = 0.47 (hexane/EtOAc, 95:5); IR (film, cmÀ1): 2981,
2958, 2903, 1728, 1371, 1321, 1284, 1254, 1207, 1135, 1057,
843; 1H NMR (200 MHz, CDCl3): (recognizable peaks for 3b) d
3
0.84 (dd, 1H, JHH = 11.2, 9.4 Hz, SiCH); (recognizable peaks for
2
3
6b) d 0.97 (dd, 1H, JHH = 3.4 Hz, JHH = 14.4 Hz, SiCHCHAHB),
1.83–1.98 (m, 1H, SiCHCHAHB); EIGCMS (column: WCOT Fused Sil-
3
3
(dd, 1H, JHH = 9.5, 11 Hz, SiCH), 1.18 (t, 3H, JHH = 7.1 Hz,
3
OCH2CH3), 1.26 (t, 3H, JHH = 7.1 Hz, OCH2CH3), 1.41 (dd, 1H,
ica, CP-SIL-5-CB, 50 m  0.25 mm/0.39 mm, 0.25
lm; carrier: he-
2JHH = 3.4 Hz, 3JHH = 9.5 Hz, CHAHBCHSi), 1.52 (dd, 1H, 2JHH = 3.4 Hz,
3JHH = 11 Hz, CHAHBCHSi), 3.80–4.30 (m, 4H, 2 Â OCH2Me), 7.30–
7.75 (m, 5H, Ph); 13C NMR (50 MHz, CDCl3): d À3.32, À3.16,
13.80, 14.00, 15.35, 18.38, 33.31, 61.16, 61.56, 127.71 (2C),
129.12, 133.78 (2C), 137.86, 169.07, 170.98; EIMS: m/z (relative
intensity) 305 (100, M+ÀMe), 275 (11), 243 (70.3), 231 (90), 215
(21), 187 (76), 169 (73), 159 (27), 135 (41), 105 (29). Compound
6a: Rf = 0.45 (hexane/EtOAc, 95:5); IR (film, cmÀ1): 3070, 2981,
2958, 2904, 1724, 1427, 1371, 1321, 1251, 1135, 1114, 1025,
lium 1 mL/min; temp.: 60 °C–2 min–10 °C/min–300 °C): tR
7.34 min (3b) (35%); tR 8.61 min (6b) (57%); m/z for 3b (relative
intensity): 317 (73, MÀMe), 287 (20), 243 (100), 199 (34) 169
(80, 157 (35), 147 (27), 133 (40), 95 (14), 73 (23); m/z for 6b (rel-
ative intensity): 346 [1,M]+, 331 (20), 301 (12), 273 (19), 257 (8),
177 (15), 147 (100), 133 (29), 108 (39), 81 (44).
4.7. Reaction of 2c with 2.5 equiv. of 5 using lithium tert-butoxide as
base
836 cmÀ1
;
1H NMR (500 MHz, CDCl3): d 0.34 (s, 3H, SiMe), 0.35
3
(s, 3H, SiMe), 0.43 (dd, 1H, JHH = 11.5, 11.5 Hz, SiCH), 1.20 (dd,
1H, 2JHH = 3 Hz, 3JHH = 11.5 Hz, SiCHCHAHB), 1.25 (t, 3H,
3JHH = 6.5 Hz, OCH2CH3), 1.24–1.27 (m, 1H, CHAHBC), 1.28 (t, 3H,
Following the procedure described for the reaction of 2a with
ylide 5, trimethylsulfoxonium iodide (550 mg, 2.5 mmol), t-BuOH
(0.26 mL, 2.7 mmol), n-BuLi (1.7 mL, 1.5 M solution in hexane,
2.5 mmol) and 2c (422 mg, 1 mmol, 1 equiv.) gave a mixture of
cyclopropane 3c and cyclobutane 6c (322 mg, 73%; 3c:6c = 7/3 by
1H NMR) which could not be separated. Compounds 3c and 6c mix-
ture: Rf = 0.65 (hexane/EtOAc, 95:5); IR (film, cmÀ1): 2977, 2933,
1731, 1429, 1366, 1330, 1241, 1194, 1118, 1060, 702; 1H NMR
3JHH = 6.5 Hz, OCH2CH3), 1.39 (dd, 1H, JHH = 3 Hz, JHH = 7 Hz,
CHAHBC), 1.86–1.92 (m, 1H, SiCHCHAHB), 4.09–4.29 (m, 4H,
2 Â OCH2CH3), 7.36 (s, 3H, Ar), 7.50–7.51 (m, 2H, Ar); 13C NMR
(50 MHz, CDCl3): d À3.41, À3.27, 13.80, 13.98, 14.81, 22.17,
24.75, 34.56, 60.92 (2C), 127.58 (2C), 128.88, 133.26 (2C), 137.86,
2
3

P.K. Kundu et al. / Journal of Organometallic Chemistry 694 (2009) 382–388
387
(200 MHz, CDCl3): (recognizable peaks for 3c) d 0.99 (dd, 1H,
7.53 (m, 5H, Ph); 13C NMR (50 MHz, CDCl3): d À3.92, À3.41,
13.85 (2C), 13.99 (2C), 26.12, 28.30, 52.20, 61.08 (2C), 61.24 (2C),
127.71 (2C), 128.68, 129.17, 134.00 (2C), 137.27, 149.05, 163.65,
164.99, 169.10, 169.46; ESIMS: m/z (relative intensity) 515 (93,
[M+Na]+), 510 (33), 447 (33), 415 (10), 401 (37), 369 (100), 323
(6); HRMS Calc. for C25H36O8SiNa [M+Na]: 515.2077. Found:
515.2099.
2
3
3JHH = 9.6, 10.8 Hz, SiCH), 1.46 (dd, 1H, JHH = 3 Hz, JHH = 10.8 Hz,
2
3
SiCHCHAHB), 1.61(dd, 1H, JHH = 3 Hz, JHH = 9.6 Hz, SiCHCHAHB);
3
(recognizable peaks for 6c) d 0.44 (dd, 1H, JHH = 11.6, 14.6 Hz,
SiCH), 1.96–2.12 (m, 1H, SiCHCHAHB); EIGCMS (column: WCOT
Fused Silica, CP-SIL-5-CB, 50 m  0.25 mm/0.39 mm, 0.25
lm; car-
rier: helium 1 mL/min; temp: 60 °C–2 min–10 °C/min–300 °C): tR
12.91 min (3c) (66%); tR 13.66 min (6c) (31%); m/z for 3c (relative
intensity): 363 (100, MÀt-BuO), 360 (71), 335 (11), 307 (13), 279
(23), 247 (11), 233 (39), 219 (24), 189 (18), 173 (14), 161 (12),
140 (12), 139 (88); m/z for 6c (relative intensity): 450 (2, M+),
393 (6), 377 (8), 349 (5), 293 (4), 251 (5), 195 (15), 140 (13), 139
(100), 108 (4).
References
[1] E.W. Colvin, Silicon Reagents in Organic Synthesis, Academic Press, London,
1988.
[2] E.W. Colvin, Silicon Reagents in Organic Synthesis, Butterworth, London, 1981.
[3] T.W. Greene, P.M.G. Wuts, Protective Groups in Organic Synthesis, second ed.,
Wiley, Interscience, 1990.
[4] M. Bols, T. Skrydstrup, Chem. Rev. 95 (1995) 253–1277.
[5] L. Fensterbank, M. Malacria, S.McN. Sieburth, Synthesis (1997) 813–854.
[6] D.R. Gauthier, K.S. Zandi, K.J. Shea, Tetrahedron 54 (1998) 2289–2338.
[7] I. Fleming, Chemtract-Org. Chem. 9 (1996) 1–64.
4.8. Reaction of 2d with 2.5 equiv. of 5 using lithium tert-butoxide as
base
[8] K. Tamao, N. Ishida, Y. Ito, M. Kumada, Org. Synth. 69 (1990) 96–105.
[9] I. Fleming, J. Dunogues, R. Smithers, Org. React. (1989) (Chapter 2).
[10] S.N. Ushakov, A.M. Itenberg, Zh. Obshch. Khim. 7 (1937) 2495 [Chem. Abstr. 32
(1938) 2083(8)].
[11] L.H. Sommer, D.L. Bailey, G.M. Goldberg, C.E. Buck, T.S. Bye, F.J. Evans, F.C.
Whitmore, J. Am. Chem. Soc. 76 (1954) 1613–1618.
Following the procedure described for the reaction of 2a with
ylide 5, trimethylsulfoxonium iodide (550 mg, 2.5 mmol), t-BuOH
(0.26 mL, 2.7 mmol), n-BuLi (1.7 mL, 1.5 M solution in hexane,
2.5 mmol) and 2d (278 mg, 1 mmol, 1 equiv.) gave diethyl
2-(3-methoxyphenyl) cyclopropane-1, 1-dicarboxylate 3d [98]
(210 mg, 72%). Rf = 0.44 (hexane/EtOAc, 9:1); IR (film, cmÀ1):
2981, 2938, 2837, 1725, 1603, 1585, 1491, 1465, 1371, 1280,
1208, 1131, 1032, 991, 862; 1H NMR (200 MHz, CDCl3): d 0.87 (t,
[12] J.M. White, Aust. J. Chem. 48 (1995) 1227–1251.
[13] P.D. Magnus, T.K. Sarkar, S. Djuric, in: G. Wilkinson, F.G.A. Stone, E.W. Abell
(Eds.), Comprehensive Organometallic Chemistry, Pergamon Press, 1981
(Chapter 48).
[14] J.B. Lambert, Tetrahedron 46 (1990) 2677–2689.
3
3
3H, JHH = 7 Hz, OCH2CH3), 1.26 (t, 3H, JHH = 7 Hz, OCH2CH3), 1.65
[15] D. Habich, F. Effenherger, Synthesis (1979) 841–876.
[16] P.F. Hudrlik, A.M. Hudrlik, T. Yimenu, M.A. Waugh, G. Nagendrappa,
Tetrahedron 44 (1988) 3791–3809.
[17] T.K. Sarkar, B.K. Ghorai, J. Chem. Soc., Chem. Commun. (1992) 1184–1185.
[18] H. Nishiyama, K. Sakuta, N. Osaka, H. Arai, M. Matsumoto, K. Itoh, Tetrahedron
44 (1988) 2413–2426.
[19] P.F. Hudrlik, M.A. Waugh, A.M. Hudrlik, J. Organomet. Chem. 271 (1984) 69–
76.
[20] R. Verma, S.K. Ghosh, J. Chem. Soc., Perkin Trans. I (1998) 2377–2381.
[21] J. R Hwu, B.A. Gilbert, L.C. Lin, B.R. Liaw, J. Chem. Soc., Chem. Commun. (1990)
161–163.
2
3
(dd, 1H, JHH = 5.2 Hz, JHH = 9.4 Hz, CHAHB), 2.11 (dd, 1H,
2JHH = 5.2 Hz, JHH = 8 Hz, CHAHB), 3.16 (dd, 1H, JHH = 8.6, 8.6 Hz,
ArCH), 3.74 (s, 3H, ArOMe), 3.84 (q, 2H, JHH = 7 Hz, OCH2CH3),
3
3
3
4.14–4.29 (m, 2H, OCH2CH3), 6.72–6.77 (m, 3H, Ar), 7.10–7.18
(m, 1H, Ar); 13C NMR (50 MHz, CDCl3): d 13.58, 13.95, 18.76,
32.00, 37.30, 55.05, 61.01, 61.57, 112.96, 114.03, 120.69, 128.97,
136.19, 159.31, 166.48, 169.73.
[22] J.R. Hwu, B.-L. Chen, L.W. Huang, T.-H. Yang, J. Chem. Soc., Chem. Commun.
(1995) 299–300.
4.9. Reaction of 2a with 0.5 equiv. of 5 using lithium tert-butoxide as
base
[23] S. Thorimbert, M. Malacria, Tetrahedron Lett. 37 (1996) 8483–8486.
[24] S.E. Denmark, M.A. Wallace, C.B. Walker, J. Org. Chem. 55 (1990) 5543–5545.
[25] K.-T. Kang, S.S. Kim, J.C. Lee, S.U. Jong, Tetrahedron Lett. 33 (1992) 3495–3498.
[26] H. Nishiyama, M. Matsumoto, H. Arai, H. Sakaguchi, K. Itoh, Tetrahedron Lett.
27 (1986) 1599.
[27] I. Fleming, S.K. Ghosh, J. Chem. Soc., Chem. Commun. (1992) 1777–1779.
[28] I. Fleming, S.K. Ghosh, J. Chem. Soc., Chem. Commun. (1994) 2285–2286.
[29] D.J. Peterson, J. Org. Chem. 33 (1968) 780–784.
[30] W.P. Weber, Silicon Reagents for Organic Synthesis, Springer-Verlag, 1983.
[31] M.A. Brook, Silicon in Organic, Organometallic, and Polymer Chemistry, John
Wiley and Sons, Inc., New York, 2000.
[32] A.G. Brook, A.R. Bassindale, in: P. de Mayo (Ed.), Rearrangements in Ground
and Excited States, Academic Press, New York, 1980, pp. 149–221.
[33] A.G. Brook, Acc. Chem. Res. 7 (1974) 77–84.
[34] T. Hiyama, E. Shirakawa, Top. Curr. Chem. 219 (2002) 61–88.
[35] S.E. Denmark, R.F. Sweis, Chem. Pharm. Bull. 50 (2002) 1531–1541.
[36] S.E. Denmark, R.F. Sweis, Acc. Chem. Res. 35 (2002) 835–846.
[37] R.J.P. Corriu, J. Organomet. Chem. 653 (2002) 20–22.
[38] K. Tamao, K. Sumitani, M. Kumada, J. Am. Chem. Soc. 94 (1972) 4374–4376.
[39] E.J. Corey, M. Chaykovsky, J. Am. Chem. Soc. 87 (1965) 1353–1364.
[40] D.M. Hodgson, M.J. Fleming, S.J. Stanway, Org. Lett. 7 (2005) 3295–3298.
[41] J. Aubé, in: B.M. Trost, I. Fleming (Eds.), Comprehensive Organic Synthesis:
Selectivity, Strategy, and Efficiency in Modern Synthetic Chemistry, vol. 1,
Pergamon, Oxford, 1991, pp. 822–825.
Dry t-BuOH (0.1 mL, 1 mmol) was added dropwise to n-BuLi
(0.67 mL, 1.5 M solution in hexane, 1 mmol) under argon atmo-
sphere. The solvent was removed under vacuum and the residue
was dissolved in dry N-methyl pyrrolidone (1 mL). The solution
was cooled to 20 °C and solid trimethylsulfoxonium iodide
(110 mg, 0.5 mmol) was added into it. After 20 minutes, this ylide
solution was added dropwise to neat 2a (306 mg, 1 mmol) over
15 min at 5 °C under argon atmosphere. The reaction mixture
was allowed to attain to room temperature and stirred for
20 min, diluted with water (30 mL) and extracted with 10% ethyl
acetate in hexane (3 Â 30 mL). The combined extract was washed
with brine, dried over anhydrous magnesium sulfate and concen-
trated under reduced pressure. The residue was purified by column
chromatography on silica using hexane/EtOAc (96/4) to give the
pure allylsilane 8a (10 mg, 4%) and homoallylsilane 9a (155 mg,
63%). A small amount of a mixture of cyclopropane 3a and cyclobu-
tane 6a (36 mg, 11%) was also isolated. Compound 8a: Rf = 0.34
(hexane/EtOAc, 95:5); 1H NMR (200 MHz, CDCl3): d 0.32 (s, 6H,
2 Â SiMe3), 1.12–1.29 (m, 12 H, 4 Â OCH2CH3), 2.60 (t, 1H,
[42] A.-H. Li, L.-X. Dai, V.K. Aggarwal, Chem. Rev. 97 (1997) 2341–2372.
[43] Y.G. Gololobov, A.N. Nesmeyanov, V.P. Lysenko, I.E. Boldeskul, Tetrahedron 43
(1987) 2609–2651.
3
3JHH = 9.4 Hz, SiCH), 3.42 (d,1H, JHH = 8.6 Hz, CH(CO2Et)2), 3.88–
[44] C. Bermand, A. Comel, G. Kirsch, ARKIVOC (2000) 128–132.
[45] S.K. Ghosh, R. Singh, S.M. Date, Chem. Commun. (2003) 636–637.
[46] S.M. Date, R. Singh, S.K. Ghosh, Org. Biomol. Chem. 3 (2005) 3369–3378.
[47] S.K. Ghosh, R. Singh, G.C. Singh, Eur. J. Org. Chem. (2004) 4141–4147.
[48] R. Singh, G.C. Singh, S.K. Ghosh, Eur. J. Org. Chem. (2007) 5376–5385.
[49] R. Singh, G.C. Singh, S.K. Ghosh, Tetrahedron Lett. 46 (2005) 4719–4722.
[50] S.M. Date, S.K. Ghosh, Bull. Chem. Soc. Jpn. 77 (2004) 2099–2100.
[51] S.M. Date, S.K. Ghosh, Angew. Chem., Int. Ed. 46 (2007) 386–388.
[52] R. Chowdhuri, S.K. Ghosh, Eur. J. Org. Chem. (2008) 3868–3874.
[53] R. Singh, S.K. Ghosh, Org. Lett. 9 (2007) 5071–5074.
3
4.22 (m, 9H, 4 Â OCH2CH3, CH(CO2Et)2), 5.54 (dd, 1 H, JHH = 8.6,
3
15.4 Hz, CH@CH), 5.72 (dd, 1H, JHH = 15.4, 10 Hz, CH@CH), 7.32–
7.49 (m, 5H, Ar). Compound 9a: Rf = 0.34 (hexane/EtOAc, 95:5);
IR (film, cmÀ1): 3070, 2982, 2938, 2906, 1725, 1644, 1446, 1371,
1254, 1153, 1111, 1028, 836, 817, 777, 737; 1H NMR (200 MHz,
CDCl3): d 0.33 (s, 3H, SiMe3), 0.36 (s, 3H, SiMe3), 1.17–1.32
(m, 12H, 4 Â OCH2CH3), 1.88–1.98 (m, 1H, SiCH), 2.50–2.60 (m,
[54] L. Alcaraz, J.J. Harnett, C. Mioskowski, JP. Martel, T. Le Gall, D.-S. Shin, J.R. Falck,
Tetrahedron Lett. 35 (1994) 5449–5452.
[55] L. Alcaraz, A. Cridland, E. Kinchin, Org. Lett. 3 (2001) 4051–4053.
3
2H, C@CHCH2), 3.43 (d, 1H, JHH = 5.2 Hz, CH(CO2Et)2), 4.02–4.28
3
(m, 8H, 4 Â OCH2CH3), 6.84 (t, 1H, JHH = 7.6 Hz, C@CH), 7.33–

388
P.K. Kundu et al. / Journal of Organometallic Chemistry 694 (2009) 382–388
[56] L. Alcaraz, K. Cox, A.P. Cridland, E. Kinchin, J. Morris, S.P. Thompson, Org. Lett. 7
(2005) 1399–1401.
[57] L. Alcaraz, J.J. Harnett, C. Mioskowski, J.P. Martel, JP. Martel, T. Le Gall, D.-S.
Shin, J.R. Falck, Tetrahedron Lett. 35 (1994) 5453–5456.
[76] E.D. Butova, A.A. Fokin, P.R. Schreiner, J. Org. Chem. 72 (2007) 5689–5696.
[77] M. Julia, S. Julia, R. Guegan, Bull. Soc. Chim. Fr. (1960) 1072–1079.
[78] R.D. Hoffsommer, D. Taub, N.L. Wendler, J. Org. Chem. 27 (1962) 4134–
4137.
[58] D. Bellus, B. Ernst, Angew. Chem., Int. Ed. 27 (1988) 797–827.
[59] H.N.C. Wong, K.-L. Lau, K.-F. Tam, Top. Curr. Chem. 133 (1986) 83–157.
[60] J.C. Namyslo, D.E. Kaufmann, Chem. Rev. 103 (2003) 1485–1537.
[61] E. Lee-Ruff, G. Mladenova, Chem. Rev. 103 (2003) 1449–1483.
[62] K. Tamao, A. Kawachi, Organometallics 14 (1995) 3108–3111.
[63] A. Kawachi, K. Tamao, Organometallics 15 (1996) 4653–4656.
[64] A.O. Fitton, J. Hill, D.E. Jane, R. Miller, Synthesis (1989) 1140–1142.
[65] P.S. Sabila, A.R. Howell, Tetrahedron Lett. 48 (2007) 8353–8355.
[66] I.M. Sasson, B.A. Otter, J. Org. Chem. 46 (1981) 1114–1120.
[67] K. Okuma, Y. Tanaka, S. Kaji, H. Ohta, J. Org. Chem. 48 (1983) 5133–5134.
[68] A.A. Fokin, E.D. Butova, L.V. Chernish, N.A. Fokina, J.EP. Dahl, R.M.K. Carison,
P.S. Schreiner, Org. Lett. 9 (2007) 2541–2544.
[69] M. Vaultier, R. Danion-Bougot, D. Danion, J. Hamelin, R. Carrie, J. Org. Chem. 40
(1975) 2990–2992.
[70] U.K. Nadir, V.K. Koul, J. Chem. Soc., Chem. Commun. (1981) 417–418.
[71] J.M. Schomaker, V.R. Pulgam, B. Borhan, J. Am. Chem. Soc. 126 (2004) 13600–
13601.
[72] J.M. Schomaker, S. Bhattacharjee, J. Yun, B. Borhan, J. Am. Chem. Soc. 129
(2007) 1996–2003.
[73] Y. Gao, J.M. Klunder, R.M. Hanson, H. Masamune, S.Y. Ko, K.B. Sharpless, J. Am.
Chem. Soc. 109 (1987) 5765–5780.
[74] P.S. Sabila, Y. Liang, A.R. Howell, Tetrahedron Lett. 48 (2007) 8356–8359.
[75] D.M. Hodgson, M.J. Fleming, Z. Hu, C. Liu, S.J. Stanway, Chem. Commun. (2006)
3226–3228.
[79] M. Julia, C. Descoinis, C. Risse, Tetrahedron (1966) 443–462 (Suppl. 8).
[80] S. Sarel, J. Yovell, M. Sarel-Imber, Angew. Chem., Int. Ed. 7 (1968) 577–588.
[81] S.F. Brady, M. Ilton, W.S. Johnson, J. Am. Chem. Soc. 90 (1968) 2882–2889.
[82] W.S. Johnson, T. Li, D.J. Faulkner, S.F. Campbell, J. Am. Chem. Soc. 90 (1968)
6225–6226.
[83] K. Mori, M. Ohki, A. Sato, M. Mataui, Tetrahedron 28 (1972) 3739–3745.
[84] M. Julia, J.-M. Paris, Tetrahedron Lett. (1974) 3445–3446.
[85] C. Descoins, D. Samain, Tetrahedron Lett. (1976) 745–748.
[86] C.Z. Santelli, Tetrahedron Lett. (1979) 1165–1168.
[87] E.J. Corey, A.K. Long, J. Org. Chem. 43 (1978) 2208–2216.
[88] C. Trindle, J.-T. Hwang, F.A. Carey, J. Org. Chem. 38 (1973) 2664–2669.
[89] L.F. van Staden, D. Gravestock, D.J. Ager, Chem. Soc. Rev. 31 (2002) 195–
200.
[90] V.J. Shiner, M.W. Ensinger, G.S. Kriz, J. Am. Chem. Soc. 108 (1986) 842–844.
[91] J.R. Hwu, B.A. Gilbert, J. Am. Chem. Soc. 113 (1991) 5917–5918.
[92] I. Fleming, A. Barbero, D. Walter, Chem. Rev. 97 (1997) 2063–2192.
[93] C.E. Masse, J.S. Panek, Chem. Rev. 95 (1995) 1293–1316.
[94] T.K. Sarkar, in: Science of Synthesis, Houben–Weyl Methods of Molecular
Transformations, vol. 4, Georg Thieme Verlag, Stuttgart, 2002, pp. 837–925.
[95] T.K. Sarkar, Synthesis (1990) 1101–1111.
[96] L. Chabaud, P. James, Y. Landais, Eur. J. Org. Chem. (2004) 3173–3199.
[97] T. Yamazaki, A. Kasatkin, Y. Kawanaka, F. Sato, J. Org. Chem. 61 (1996) 2266–
2267.
[98] A. Chraibi, H. Fillion, L.D. Cuong, Ann. Pharm. Fr. 38 (1980) 343–352.