2-Lithio-3-methoxy-1,3-dimethylcyclopentene: A synthetic equivalent of 2-lithio-1,3-dimethylcyclopentadiene and useful synthon for 6-alkyl-1,4- dimethylfulvenes and ansa-metallocene complexes

Article abstract of DOI:10.1055/s-2004-822324

2-Bromo-3-methoxy-1,3-dimethylcyclopentene (3). is synthesized in 85% yield in 80 g scale by 1,2-addition of MeLi to 2-bromo-3-methyl-2-cyclopenten-1-one and subsequent in situ treatment of MeI. Addition of n-BuLi to the bromo-compound 3 in Et₂O affords 2-lithio-3-methoxy-1,3- dimethylcyclopentene (1). Successive addition of RCHO [R = CH₃, (CH₂)₂CH₃, CH(CH₃)₂, C(CH₃)₃, H] and MeI to the lithium compound and aqueous acidic work-up provide cyclopentadiene compounds, 2-[CHR(OMe)]-1,3-Me ₂C₅H₃ in 60-84% yields. Treatment of the cyclopentadienes with NaH or KH in pentane affords 1,4,6-trimethylfulvene, 6-n-propyl-1,4-dimethylfulvene, 6-isopropyl-1,4-dimethylfulvene, 6-tert-butyl-1,4-dimethylfulvene and 1,4-dimethylfulvenein 67-83% yields. Ligand for an ansa-metallocene complex, CH₂C(1,3-Me₂Cp) ₂ZrCl₂, can be shortly afforded in 64% yield by reacting the lithium compound 1 with the newly synthesized 1,4-dimethylfulvene.

Full text of DOI:10.1055/s-2004-822324

1
052
PAPER
2
-Lithio-3-methoxy-1,3-dimethylcyclopentene: A Synthetic Equivalent of 2-
Lithio-1,3-dimethylcyclopentadiene and Useful Synthon for 6-Alkyl-1,4-dime-
thylfulvenes and ansa-Metallocene Complexes
a
a
a
a
b
b
2
Y
-Lithio-3-methox
o
y-1,3-dimeth
u
ylcyclopente
n
ne g Chul Won, Ui Gab Joung, Eun Sook Cho, Bun Yeoul Lee,* Hyosun Lee, Young-Whan Park,
c
Kwang Ho Song
a
Department of Molecular Science and Technology, Ajou University, Suwon 442-749, Korea
Fax +82(31)2192519; E-mail: bunyeoul@ajou.ac.kr
b
c
LG Chem Ltd., Research Park, 104-1, Munji-dong, Yuseong-gu, Daejon 305-380, Korea
Department of Chemical & Biological Engineering, Korea University, Seoul 136-701, Korea
Received 19 January 2004; revised 20 February 2004
which is not desirable for large-scale synthesis, and most
intermediates were purified by column chromatography.
In order for a metallocene complex to have commercial
viability, scalable synthesis should be ensured. Herein, we
Abstract: 2-Bromo-3-methoxy-1,3-dimethylcyclopentene (3) is
synthesized in 85% yield in 80 g scale by 1,2-addition of MeLi to 2-
bromo-3-methyl-2-cyclopenten-1-one and subsequent in situ treat-
ment of MeI. Addition of n-BuLi to the bromo-compound 3 in Et O
2
affords 2-lithio-3-methoxy-1,3-dimethylcyclopentene (1). Succes- report a more convenient and scaleable synthetic route for
sive addition of RCHO [R = CH , (CH ) CH , CH(CH ) , C(CH ) ,
3
2 2
3
3
2
3 3
the fulvenes. A key intermediate of the synthetic route is
-lithio-3-methoxy-1,3-dimethylcyclopentene (1), which
has potential to react with various electrophiles. Because
the methoxy group can be easily eliminated by aqueous
acidic work-up to furnish cyclopentadiene compounds,
H] and MeI to the lithium compound and aqueous acidic work-up
provide cyclopentadiene compounds, 2-[CHR(OMe)]-1,3-
Me C H in 60–84% yields. Treatment of the cyclopentadienes with
2
8
2
5
3
NaH or KH in pentane affords 1,4,6-trimethylfulvene, 6-n-propyl-
,4-dimethylfulvene, 6-isopropyl-1,4-dimethylfulvene, 6-tert-bu-
1
tyl-1,4-dimethylfulvene and 1,4-dimethylfulvene in 67–83% yields. compound 1 is a synthetic equivalent of 2-lithio-1,3-di-
Ligand for an ansa-metallocene complex, CH C(1,3- methylcyclopentadiene (Scheme 2).
2
Me Cp) ZrCl , can be shortly afforded in 64% yield by reacting the
2
2
2
lithium compound 1 with the newly synthesized 1,4-dimethylful-
vene.
O
O
Ph
OH
O
O
Br
Key words: fulvene synthesis, cyclopentadienes, metallocenes,
lithiation, organometallic reagents
Br
Me
O
Me
Me
Me
Me
Ph
Ph
1
6
5
Fulvenes are versatile intermediates for metallocene com-
plexes, which can be used as catalysts for polymerization
2
Ph
OTHP
OTHP
4
3
1
of olefins, and also serve as substrates for cycloaddition
Me
Me
Me
reaction by which useful organic compounds can be pro-
2
Scheme 1 Previous synthetic route for 1,4,6-substituted fulvene
vided. Most of fulvenes are prepared by coupling reac-
tion of cyclopentadiene or substituted cyclopentadienes
3
with aldehydes or ketones. 1,4-Disubstituted or 1,4,6-
Me OMe
Me
trisubstituted fulvenes cannot be afforded by the synthetic
route. If a 1,3-disubstituted cyclopentadiene is reacted
with an aldehyde or ketone aiming to prepare a 1,4-substi-
tuted or 1,4,6-substituted fulvene, the substituents are sit-
uated mainly at 1,3-positions in the resulting fulvene due
Li
E
E
then acidic work-up
Me
Me
1
Scheme 2
4
to steric reason. Other routes for synthesis of fulvene de-
rivatives have been described but, in those cases, the prod-
ucts still have substituents on 1- and 3-positions.5
The lithium compound 1 can be generated from the corre-
sponding bromo-compound 3 by treatment of n-BuLi in
Syntheses of 1,2,3,4-tetramethylfulvene and 1,2,3,4,6-
pentamethylfulvene and their use for preparation of useful
Et O (Scheme 3). White solid precipitated at room tem-
2
6
perature, which was directly used for the next reaction
without isolation or purification. The bromo-compound 3
was synthesized in 80 g scale in 85% yield in 1.0 L flask
from 2 by the 1,2-addition of MeLi and subsequent treat-
ment of MeI. MeLi should be used as a complex with LiBr
metallocene complexes were reported.
Very recently, we have reported a synthetic route to obtain
7
1
,4,6-substituted fulvenes (Scheme 1). The synthetic
route contains protection/de-protection of carbonyl,
in Et O. If MeLi not containing LiBr was used, yield was
2
low with formation of black precipitates. The solvent was
changed to DMF in the stage of ether formation. Incom-
plete ether formation was observed when only MeI was
SYNTHESIS 2004, No. 7, pp 1052–1056
x
x
.
x
x
.2
0
0
4
Advanced online publication: 02.04.2004
DOI: 10.1055/s-2004-822324; Art ID: F01304SS
Georg Thieme Verlag Stuttgart · New York
©

PAPER
2-Lithio-3-methoxy-1,3-dimethylcyclopentene
1053
added to the lithium alkoxide. This might be attributed to was so volatile that it was isolated by bulb-to-bulb distil-
the presence of some proton donors in the reaction mix- lation under the vacuum after pentane was removed by
ture, e.g., water in DMF. Complete ether formation was vacuum at low temperature (–30 °C). Polymerization of
achieved by extra addition of NaH to the reaction mixture. 13 to a viscous residue is frequently observed during the
The compound was easily purified by vacuum distillation. distillation but it can be avoided when the pentane solu-
tion is thoroughly washed with water before distillation. A
O
Me OMe
cyclopentadienyl anion formed in the presence of NaH
1
13
might initiate the polymerization. The H NMR, C NMR
spectra, and the high-resolution mass data were in agree-
ment with the fulvene structures.
Br MeLi
then MeI
Br n-BuLi
1
Me
Me
2
3
Me
Me
R
Scheme 3
NaH
RC(O)H
then MeI
1
R
OMe
Addition of aldehydes to the lithium compound 1 and sub-
sequent treatment of MeI and final aqueous 2 N HCl
work-up furnished the desired cyclopentadiene com-
pounds 4–8 in 60–84% yields (Scheme 4). Solvent change
to DMF and an additional addition of NaH are required for
the complete formation of methyl ethers. Elimination of
MeOH was carried out by shaking the EtOAc solution of
the resulting products with 2 N aqueous HCl for several
minutes to afford cyclopentadiene compounds. Analysis
Me
4: R=CH3
Me
9: R=CH3
10: R=(CH2)2CH3
11: R=CH(CH3)2
12: R=C(CH3)3
13: R=H
5: R=(CH2)2CH3
6: R=CH(CH3)2
7: R=C(CH3)3
8: R=H
Scheme 4
Compound 8 can be prepared in one step from compound
2 (Scheme 5). The step is composed of successive treat-
ments of five reagents but it can be conducted in one pot
in 64% overall yield. 1,2-Addition of MeLi to 2 in THF af-
forded lithium tertiary alkoxide, which was directly lithi-
ated by the addition of two equivalents of t-BuLi.
Formaldehyde gas, which was generated by heating
paraformaldehyde in the presence of catalytic amount of
p-toluenesulfonic anhydride, was added and then the re-
sulting dilithium salt was transformed to methyl ether by
treatment of MeI in DMF. The same one-pot procedure
did not give the desired compounds 4–6. Addition of the
dilithium salts to the aldehydes containing a-protons
might trigger some side reaction such as deprotonation re-
action and subsequent the aldol condensation.
1
13
of the H and C NMR spectra indicated that the crude
product was fairly clean and hence they were used for the
next reaction without further purification. Substituted cy-
clopentadienes are frequently obtained as a set of isomers
9
due to the rapid 1,5-sigmatropic rearrangement. Howev-
er, compounds 4–6, and 8 were obtained as a single iso-
mer by the symmetry of the substituents and they could be
1
13
unambiguously characterized by the H and C NMR
spectra. However, compound 7 was obtained as a pair of
isomers. Signals of vinyl proton and t-butyl protons were
not separated but the other signals were separated in a 3:2
1
ratio in the H NMR spectrum. The observation of two
sets of signals might be attributed to the existence of iso-
mers arisen by hindered rotation of the C–C bond as
shown in Figure 1. If the bulky t-butyl group prevents the
rotation, the two compounds shown in Figure 1 are not
equivalent each other.
Me
Me
H
H
X
OMe
OMe
Me
Me
Figure 1
Scheme 5
The fulvenes were afforded by treatment of NaH to the cy-
clopentadiene compounds 4–6 and 8 in pentane or hexane
at room temperature in 69–83% yield (Scheme 4). The
yellow color appeared as the reaction proceeded. In the
case of bulky t-butyl compound 7, the reaction was slug-
gish with the identical conditions. The fulvene 12 was
successfully generated by treatment of more reactive KH
at 35–40 °C for 2 days in 67% yield. Fulvenes 9–12 were
simply purified by passing the residue through short pad
of silica gel eluting with pentane or hexane. Fulvene 13
The lithium compound 1 can be used for the synthesis of
an ansa-metallocene complex 15, which was reported to
be highly active, when activated with MAO, for ethylene–
norbornene copolymerization with excellent incorpora-
10
tion of norbornene. Because the ethylene–norbornene
copolymer is very attractive as a novel substrate for high-
density data storage device, packaging, and optical/bio-
11
medical applications, we were pushed to develop an ef-
ficient synthetic route for the complex. Previously, the
Synthesis 2004, No. 7, 1052–1056 © Thieme Stuttgart · New York

1
054
Y. C. Won et al.
PAPER
complex was prepared in five steps from 1,4-pentadiyne was removed with rotary evaporator to give a residue, which was
distilled under reduced pressure (70 °C/0.5 torr) to give white solid
with low overall yield (6.8%). The starting material, 1,4-
contaminated with some oily impurity. The solid was dissolved in
pentadiyne, was not readily available and the intermedi-
EtOAc (100 mL) and hexane (200 mL). When the solution was
ates were purified mainly by column chromatography. By
stored at –20 °C overnight, white crystals were deposited which
were collected by filtrations. The crystals were washed with hexane
using the lithium compound 1 and newly synthesized ful-
vene 13, compound 14 was prepared in one step in 64%
(ca. 50 mL); yield: 70% (134 g).
yield (Scheme 6). The compound 14 was easily purified
by passing the crude residue through short pad of alumina 2-Bromo-3-methoxy-1,3-dimethylcyclopentene (3)
MeLi as complex with LiBr (300 mL, 1.5 M in Et O, 456 mmol)
eluting with hexane.
2
was added to a flask (1 L) and Et O was removed by vacuum. THF
2
(
200 mL) was added at –78 °C and compound 2 (80.0 g, 456 mmol)
Me
dissolved in THF (200 mL) was added with syringe pump for 1 h.
The solution was stirred for 1 h at –78 °C. The solvent was removed
by vacuum. Anhyd DMF (400 mL) and MeI (64.8 g, 456 mmol)
were added successively. The solution was stirred for 2 h. NaH
Me
Me
Me
Me
Me
ZrCl2
1
+ 13
(
11.0 g, 450 mmol) and MeI (64.8 g, 456 mmol) were additionally
Me
added and the solution was stirred overnight at 40 °C. Water (800
mL) and hexane (1600 mL) were added. Organic phase was collect-
ed and washed with brine (3 × 400 mL). The organic phase was
dried with anhyd Na CO and solvent was removed with rotary
evaporator. Anhyd MgSO should not be used as a drying agent be-
Me
14
15
Scheme 6
2
3
4
cause it causes the elimination reaction. The product was isolated
and purified by vacuum distillation (50 °C/0.5 torr); yield: 85% (80
In conclusion, short and scaleable synthesis of 6-alkyl-
1
,4-dimethylfulvenes (alkyl = methyl, n-propyl, isopro- g).
pyl, t-butyl) is achieved in two steps in overall 47–59%
1
H NMR (CDCl ): d = 3.11 (s, 3 H, OCH ), 2.42–2.24 (m, 2 H,
3
3
yields from 2-bromo-3-methoxy-1,3-dimethylcyclopen- CH ), 2.18 (ddd, J = 14.0, 9.2, 4.0 Hz, 1 H, CH ), 1.92 (ddd, J =
2
2
tadiene (3), which can be easily synthesized in 80 g scale 14.4, 9.2, 5.6 Hz, 1 H, CH ), 1.82 (s, 3 H, CH ), 1.36 (s, 3 H, CH ).
2
3
3
from 2-bromo-3-methyl-2-cyclopenten-1-one (2). 1,4-
13
1
C{ H} NMR (CDCl ): d = 141.50, 121.79, 88.36, 50.30, 34.83,
3
Dimethylfulvene (13) was synthesized from 2 in two steps 31.40, 26.35, 16.37.
in 53% overall yield. Key intermediate of the synthetic
route, 2-lithio-3-methoxy-1,3-dimethylcyclopentene (1),
can react with newly synthesized 1,4-dimethylfulvene
2
-(1-Methoxyethyl)-1,3-dimethyl-1,3-cyclopentadiene (4)
Compound 3 (10.0 g, 48.8 mmol) was dissolved in Et O (60 mL)
2
and the solution was cooled to –30 °C. n-BuLi (19.5 mL, 2.5 M in
hexane, 48.8 mmol) was added dropwise and the solution was al-
lowed to warm to r.t. The solution was stirred for 30 min after which
white solid precipitated. The solution was cooled to –30 °C and ac-
etaldehyde (2.37 g, 53.7 mmol) was added dropwise via syringe.
The solution was stirred for 20 min at –30 °C. All volatiles were re-
moved by vacuum. Anhyd DMF (50 mL) and NaH (1.17 g, 48.8
mmol) were added and the solution was stirred for 30 min at r.t. MeI
(
13) to give a biscyclopentadiene compound 14, which
can be used for the synthesis of a useful ansa-metallocene
complex, CH C(1,3-Me Cp) ZrCl (15).
2
2
2
2
All manipulations were performed under an inert atmosphere using
standard glove box and Schlenk techniques. Pentane, hexane, THF,
and Et O were distilled from benzophenone ketyl. DMF was puri-
2
(
13.9 g, 97.6 mmol) was added and the resulting mixture was stirred
fied by vacuum distillation and subsequent contacting with molec-
ular sieves. NMR spectra were recorded on a Varian Mercury plus
overnight. Water (100 mL) and hexane (100 mL) were added and
the organic phase was collected which was washed with brine (150
mL). Solvent was removed with rotary evaporator and the residue
was dissolved in EtOAc (10 mL). Aqueous HCl (2 N, 30 mL) was
added and the two-phase mixture was shaken vigorously for 2 min.
Water phase was removed and the organic phase was washed with
4
00. Mass spectra were obtained on a Micromass VG Autospec.
2
-Bromo-3-methyl-2-cyclopenten-1-one (2)
Scalable synthesis of the compound has been already reported by
7
us but when the compound prepared by this procedure was used for
sat aq NaHCO (40 mL). The organic phase was dried with anhyd
MgSO and solvent was removed with rotary evaporator. Analysis
3
the synthesis of 3, severe decomposition of the product was ob-
served during the distillation. We attributed it to the presence of
some uneliminated compound as an impurity, which can generate
HBr by the heating causing the decomposition of the acid labile
compound 3. When the elimination reaction was carried out com-
4
1
13
of the H and C NMR spectra indicated that the crude residue was
fairly clean and it was used for the next reaction without further pu-
rification; yield: 60% (4.50 g).
1H NMR (CDCl
6.4 Hz, 1 H, CHOCH
2.00 (q, J = 2.0 Hz, 3 H, CH
Hz, 3 H, CHCH ).
pletely by using Et N as a base, the decomposition problem was
3
): d = 5.78 (d, J = 2.0 Hz, 1 H, =CH), 4.31 (q, J =
), 3.17 (s, 3 H, OCH ), 2.77 (s, 2 H, CH ),
), 1.98 (s, 3 H, CH ), 1.35 (d, J = 6.4
3
solved. Thus, 3-methyl-2-cyclopenten-1-one (105 g, 1.09 mol) was
dissolved in CH Cl (1.15 L) in a 3.0 L three-necked flask. The so-
3
3
2
2
2
3
3
lution was cooled to 0 °C with an ice bath. Bromine (192 g, 1.20
mol) dissolved in CH Cl (1.0 L) was added dropwise for 5 h keep-
3
13
1
2
2
C{ H} NMR (CDCl ): d = 142.63, 140.07, 139.64, 124.83, 73.37,
3
ing the temperature below 5 °C. The solution color turned to pale
5
5.95, 44.28, 21.01, 15.43, 13.78.
yellow. Et N (166 g, 1.64 mol) was added dropwise for 5 h keeping
3
HRMS (EI): m/z calcd for C H O: 152.1201; found: 152.1203.
1
0
16
the temperature below 5 °C. The solution was allowed to warm to
r.t. and stirred overnight. HCl solution (1.0 N, 500 mL) was added
and the mixture was stirred for 30 min. The mixture was poured into
a separatory funnel. The aqueous layer was removed and the organ-
2
-(1-Methoxybutyl)-1,3-dimethyl-1,3-cyclopentadiene (5)
The compound was synthesized according to the method and condi-
tions used for 4 by using 3 (2.00 g, 9.75 mmol) and butanal (0.773
ic layer was washed with sat. aq NaHCO solution (500 mL). The
3
organic layer was collected and dried over anhyd MgSO . Solvent
4
Synthesis 2004, No. 7, 1052–1056 © Thieme Stuttgart · New York

PAPER
2-Lithio-3-methoxy-1,3-dimethylcyclopentene
1055
g, 10.7 mmol). The crude residue was used for the next reaction
was washed with sat aq NaHCO (200 mL). The organic phase was
3
without further purification; yield: 68% (1.19 g).
dried with anhyd MgSO and solvent was removed with rotary
4
1
evaporator. The product was isolated by distillation under reduced
pressure (50 °C/0.7 torr).; yield from 2: 64% (15.2 g).
H NMR (CDCl ): d = 5.83 (d, J = 1.6 Hz, 1 H, =CH), 4.17 (t, J =
3
7
.2 Hz, 1 H, CHOCH ), 3.21 (s, 3 H, OCH ), 2.84 (quintet, J = 1.6
3
3
1
Hz, 2 H, CH ), 2.03 (q, J = 1.6 Hz, 3 H, CH ), 2.02 (s, 3 H, CH ),
1
1
H NMR (CDCl ): d = 5.83 (d, J = 2.0 Hz, 1 H, =CH), 4.15 (s, 2 H,
2
3
3
3
.87–1.78 (m, 1 H, CHCH CH ), 1.65–1.55 (m, 1 H, CHCH CH ),
OCH ), 3.33 (s, 3 H, OCH ), 2.85 (t, J = 2.0 Hz, 2 H, CH ), 2.05 (s,
2
2
2
2
2
3
2
.46–1.34 (m, 2 H, CH CH ), 0.94 (t, J = 7.6 Hz, 3 H, CH CH ).
3 H, CH ), 1.99 (q, J = 2.0 Hz, 3 H, CH ).
2
3
2
3
3
3
1
3
1
13
1
C{ H} NMR (CDCl ): d = 142.67, 140.79, 138.61, 124.67, 77.55,
C{ H} NMR (CDCl ): d = 142.97, 142.75, 136.37, 123.64, 65.76,
3
3
5
5.89, 44.14, 37.35, 19.36, 15.41, 14.13, 13.82.
57.69, 44.37, 14.11, 13.90.
HRMS (EI): m/z calcd for C H O: 180.1514; found: 180.1512.
HRMS (EI): m/z calcd for C H O: 138.1045; found: 138.1043.
1
2
20
9
14
2
-(1-Methoxy-2-methylpropyl)-1,3-dimethyl-1,3-cyclopentadi-
1,4,6-Trimethylfulvene (9)
ene (6)
Compound 4 (2.90 g, 19.2 mmol) was dissolved in pentane (20 mL)
and NaH (0.534 g, 22.3 mmol) was added under nitrogen. The mix-
ture was stirred overnight at r.t. The solution turned to yellow and
The compound was synthesized according to the method and condi-
tions used for 4 by using 3 (5.00 g, 24.4 mmol) and isobutylalde-
hyde (1.94 g, 26.9 mmol). The crude residue was used for the next
reaction without further purification; yield: 73% (3.19 g).
1
the by-product of NaOCH precipitated. The evolved hydrogen gas
3
was removed by venting. The mixture was filtered and washed with
pentane until the filtrate is colorless. The solution was passed
through short pad of silica gel (5.0 g). The solvent was removed by
rotary evaporator to give yellow oily residue which was found to be
H NMR (CDCl ): d = 5.82 (s, 1 H, =CH), 3.70 (d, J = 9.2 Hz, 1 H,
3
CHOCH ), 3.19 (s, 3 H, OCH ), 2.85 (t, J = 2.0 Hz, 2 H, CH ), 2.02–
3
3
2
1
.98 [m, 1 H, CH(CH ) ], 2.00 (s, 6 H, CH ), 1.09 [d, J = 6.8 Hz, 3
3 2 3
1
13
pure by the analysis of the H and C NMR spectra; yield: 71%
H, CH(CH ) ], 0.74 [d, J = 6.8 Hz, 3 H, CH(CH ) ].
3
2
3 2
(
1.65 g).
1
3
1
C{ H} NMR (CDCl ): d = 142.96, 141.88, 137.90, 124.57, 83.96,
3
1
H NMR (CDCl ): d = 6.44 (q, J = 7.6 Hz, 1 H, C=CHCH ), 6.06 (s,
3
3
5
6.36, 44.20, 32.66, 20.25, 19.34, 15.65, 14.16.
1
H, =CH), 5.96 (s, 1 H, =CH), 2.25 (s, 3 H, CH ), 2.20 (d, J = 7.6
3
HRMS (EI): m/z calcd for C H O: 180.1514; found: 180.1512.
1
2
20
Hz, 3 H, C=CHCH ), 2.05 (s, 3 H, CH ).
3
3
1
3
1
C{ H} NMR (CDCl ): d = 145.71, 133.07, 132.73, 130.24,
3
2
-(1-Methoxy-2,2-dimethylpropyl)-1,3-dimethyl-1,3-cyclopen-
1
29.98, 125.27, 17.44, 15.16, 12.57.
tadiene (7)
The compound was synthesized according to the method and condi-
tions used for 4 by using 3 (1.00 g, 4.88 mmol) and trimethylacetal-
dehyde (0.462 g, 5.37 mmol). The crude residue was used for the
next reaction without further purification; yield: 84% (0.796 g). Sig-
nals of two sets of isomers were observed in the H NMR spectrum
in a 3:2 ratio. The signals for the minor isomer are marked by italic
HRMS (EI): m/z calcd for C H : 120.0939; found: 120.0938.
9 12
6-Propyl-1,4-dimethylfulvene (10)
The compound was synthesized according to the method and condi-
tions for 9 by using 5 (0.973 g, 5.40 mmol) and NaH (0.154 g, 6.48
mmol); yield: 69% (0.554 g).
1
character.
1
H NMR (CDCl ): d = 6.32 (t, J = 7.6 Hz, 1 H, C=CHCH ), 6.05 (s,
3
2
1
H NMR (CDCl ): d = 5.82 (s, 1 H, =CH), 3.87, 3.74 (s, 1 H,
1 H, =CH), 5.95 (s, 1 H, =CH), 2.60 (q, J = 7.6 Hz, 2 H, C=CHCH ),
2.22 (s, 3 H, CH ), 2.04 (s, 3 H, CH ), 1.61 (sextet, J = 7.6 Hz, 2 H,
3
2
CHOCH ), 3.20, 3.19 (s, 2 H, OCH ), 2.86, 2.80 (br s, 2 H, CH ),
3
3
2
3
3
2
.11, 2.07 (s, 3 H, CH ), 1.96, 1.92 (s, 3 H, CH ), 0.96 (s, 9 H, CH ).
CH CH ), 1.04 (t, J = 7.6 Hz, 3 H, CH CH ).
3
3
3
2
3
2
3
1
3
1
13
1
C{ H} NMR (CDCl ): d = 144.49, 143.91, 142.84, 141.30,
C{ H} NMR (CDCl ): d = 144.73, 138.89, 132.98, 130.24,
3
3
1
4
37.61, 136.31, 125.27, 123.94, 87.03, 86.62, 57.07, 56.68, 45.05,
4.26, 37.88, 37.46, 27.29, 26.98, 16.65, 16.03, 15.51, 15.45.
130.13, 125.333, 30.97, 23.06, 17.34, 14.12, 12.66.
HRMS (EI): m/z calcd for C H : 148.1252; found: 148.1250.
1
1
16
HRMS (EI): m/z calcd for C H O: 194.1670; found: 194.1669.
1
3
22
6
-Isopropyl-1,4-dimethylfulvene (11)
2
-Methoxymethyl-1,3-dimethyl-1,3-cyclopentadiene (8)
The compound was synthesized according to the method and condi-
tions used for 9 by using 6 (1.19 g, 6.57 mmol) and NaH (0.189 g,
7.89 mmol); yield: 81% (0.788 g).
To a flask containing 2 (30.0 g, 171 mmol) in THF (300 mL) was
added MeLi (126 mL, 1.5 M in Et O, 189 mmol) for 1 h at –78 °C
2
with syringe pump. The solution was stirred for 2 h at –78 °C and
then t-BuLi (202 mL, 1.7 M in pentane, 343 mmol) was added. The
solution was stirred for 2 h at –78 °C. Gaseous formaldehyde, gen-
erated by heating paraformadehyde (15.4 g) in the presence of p-tol-
uenesulfonic anhydride (8.0 g) at 100 °C, was vacuum-transferred
directly via a Schlenk line to the solution at –78 °C under vigorous
stirring. The solution was warmed to r.t. and then the volatiles were
removed under vacuum. Anhyd DMF (250 mL) and MeI (48.7g,
1
H NMR (CDCl ): d = 6.10 (d, J = 10.4 Hz, 1 H, C=CHCH), 6.05
3
(
1
6
s, 1 H, =CH), 5.95 (s, 1 H, =CH), 3.30 [d septet, J = 10.4, 6.4 Hz,
H, CH(CH ) ], 2.24 (s, 3 H, CH ), 2.04 (s, 3 H, CH ), 1.16 (d, J =
3 2 3 3
.4 Hz, 6 H, CH(CH ) ].
3
2
1
3
1
C{ H} NMR (CDCl ): d = 145.54, 142.18, 133.45, 130.34,
3
1
30.09, 125.36, 27.70, 23.03, 17.03, 12.68.
HRMS (EI): m/z calcd for C H : 148.1252; found: 148.1250.
1
1
16
3
43mmol) were added successively to the residue and the resulting
mixture was stirred overnight. NaH (4.00 g, 166 mmol) and MeI
24.3g, 166 mmol) were added successively to the solution and the
6
-tert-Butyl-1,4-dimethylfulvene (12)
(
The compound was synthesized according to the method and condi-
mixture was stirred for another 20 h. Water (300 mL), brine (300
mL), and hexane (600 mL) were added and the organic phase was
collected. The aqueous phase was extracted with additional hexane
tions used for 9 by using 7 (0.119 g, 0.610 mmol) and KH (0.29 g,
0
.73 mmol). The reaction was so sluggish at r.t. that the mixture was
heated to 35–40 °C for 2 d; yield: 67% (0.066 g).
(200 mL). The organic phases were combined and washed with
1
H NMR (CDCl ): d = 6.46 (s, 1 H, =CH), 6.17 (s, 1 H, =CH), 5.95
3
brine (3 × 200 mL). Solvent was removed with rotary evaporator
and the residue was dissolved in EtOAc (300 mL). Aqueous HCl (2
N, 200 mL) was added and the two-phase mixture was shaken vig-
orously for 2 min. Water phase was removed and the organic phase
(
s, 1 H, CH), 2.32 (s, 3 H, CH ), 2.04 (s, 3 H, CH ), 1.38 [d, J = 0.8
3
3
Hz, 9 H, C(CH ) ].
3
3
Synthesis 2004, No. 7, 1052–1056 © Thieme Stuttgart · New York

1
056
Y. C. Won et al.
PAPER
1
3
1
C{ H} NMR (CDCl ): d = 150.00, 143.60, 136.10, 133.30, References
3
1
27.62, 124.79, 33.10, 31.80, 19.36, 13.51.
(1) (a) Alt, H. G.; Jung, M. J. Organomet. Chem. 1998, 568, 87.
HRMS (EI): m/z calcd for C H : 162.1408; found: 162.1410.
1
2
18
(
b) Kaminsky, W.; Engehausen, R.; Kopf, J. Angew. Chem.,
Int. Ed. Engl. 1995, 34, 2273. (c) Kunz, K.; Erker, G.;
Dörig, S.; Bredeau, S.; Kehr, G.; Fröhlich, R.
Organometallics 2002, 21, 1031. (d) Erker, G.; Wilker, S.;
Krüger, C.; Nolte, M. Organometallics 1993, 12, 2140.
1
,4-Dimethylfulvene (13)
The compound was synthesized according to the method and condi-
tions used for 9 by using 8 (14.2 g, 103 mmol) and NaH (2.47 g, 103
mmol) in pentane (100 mL). The reaction time was reduced to 3 h.
The volatile product was isolated by following the work-up proce-
dure. Thus, the reaction mixture was filtered and washed with pen-
tane until the filtrate is colorless. The filtrate was washed
thoroughly with water and dried over anhyd MgSO . Pentane was
removed under vacuum at –30 °C. The compound was isolated by
bulb-to-bulb distillation at r.t. under vacuum; yield: 83% (9.07 g).
(
e) Koch, T.; Blaurock, S.; Somoza, F. B.; Voigt, A.;
Kirmse, R.; Hey-Hawkins, E. Organometallics 2000, 19,
2556. (f) Eisch, J. J.; Shi, X.; Owuor, F. A. Organometallics
1998, 17, 5219. (g) Beckhaus, R.; Lützen, A.; Haase, D.;
4
Saak, W.; Stroot, J.; Becke, S.; Heinrichs, J. Angew. Chem.
Int. Ed. 2001, 40, 2056. (h) Halterman, R. L. Chem. Rev.
1992, 92, 965.
1
H NMR (C D ): d = 5.95 (q, J = 1.2 Hz, 2 H, CH), 5.41 (t, J = 1.2
(2) (a) Barluenga, J.; Martinez, S.; Suarez-Sobrino, A. L.;
Tomas, M. J. Am. Chem. Soc. 2002, 124, 5984.
6
6
Hz, 2 H, CH ), 1.89 (d, J = 1.2 Hz, 6 H, CH ).
2
3
1
3
1
(b) Barluenga, J.; Martinez, S.; Suarez-Sobrino, A. L.;
Tomas, M. J. Am. Chem. Soc. 2001, 123, 11113.
(3) (a) Stone, K. J.; Little, R. D. J. Org. Chem. 1994, 59, 1849.
C{ H} NMR (C D ): d = 154.51, 131.19, 128.99, 114.74, 12.43.
6
6
HRMS (EI): m/z calcd for C H : 106.0783; found: 106.0782.
8
10
(
b) Erden, I.; Xu, F.-P.; Sadoun, A.; Smith, W.; Sheff, G.;
2
,2¢-Methylenebis(1,3-dimethyl-1,3-cyclopentadiene) (14)
Ossun, M. J. Org. Chem. 1995, 60, 813.
4) Collins, S.; Hong, Y.; Taylor, N. J. Organometallics 1990, 9,
2695.
5) (a) Lee, G. C. M.; Tobias, B.; Holmes, J. M.; Harcourt, D.
A.; Garst, M. E. J. Am. Chem. Soc. 1990, 112, 9330.
To the lithium compound prepared from compound 3 (21.2 g, 103
mmol) in Et O according to the same method and conditions de-
(
(
2
scribed in the synthesis of 4 was added dropwise fulvene 13 (11.0
g, 103 mmol) in pentane (130 mL) at –25 °C. The solution was
stirred for 30 min at –25 °C. The yellow fulvene color disappeared.
Water (60 mL) was added and the organic layer was collected. Sol-
vent was removed with rotary evaporator and some volatiles were
thoroughly removed under vacuum. Cold EtOAc (800 mL, –20 °C)
and aq HCl (2 N, 400 mL) were added successively and the two-
phase mixture was shaken vigorously for 2 min. Aqueous phase was
discarded and the organic phase was washed with sat. aq NaHCO3
(
b) Johnson, E. S.; Balaich, G. J.; Fanwick, P. E.; Rothwell,
I. P. J. Am. Chem. Soc. 1997, 119, 11086.
(
6) (a) Döring, S.; Erker, G. Synthesis 2001, 43. (b) Mallin, D.
T.; Rausch, M. D.; Lin, Y. G. J. Am. Chem. Soc. 1990, 112,
2
030.
(
7) Won, Y. C.; Kwon, H. Y.; Lee, B. Y.; Park, Y.-W. J.
Organomet. Chem. 2003, 677, 133.
(8) Related acylvinyl and vinylogous synthons were
comprehensively reviewed. See: Chinchilla, R.; Nájera, C.
Chem. Rev. 2000, 100, 1891.
(
200 mL). The organic phase was dried with anhyd MgSO and sol-
4
vent was removed with rotary evaporator. The residue was filtered
over short pad of alumina (70 g) eluting with hexane (420 mL);
yield: 64% (13.3 g). H and C NMR spectra are identical with
1
13
(
9) Jutzi, P. Chem. Rev. 1986, 86, 983.
10) (a) Lee, B. Y.; Kim, Y. H.; Won, Y. C.; Han, J. W.; Suh, W.
1
0
those of the authentic sample.
(
H.; Lee, I. S.; Chung, Y. K.; Song, K. H. Organometallics
2
002, 21, 1500. (b) Lee, B. Y.; Kim, Y. H.; Won, Y. C.;
Shim, C. B.; Shin, D. M.; Chung, Y. K. J. Organomet. Chem.
002, 660, 161.
Acknowledgment
2
The authors are grateful to LG Chemical Ltd. for financial assi-
stance.
(
11) (a) Park, S. Y.; Choi, K. Y.; Song, K. H.; Jeong, B. G.
Macromolecules 2003, 36, 4216. (b) Kaminsky, W.;
Engehausen, R.; Kopf, J. Angew. Chem., Int. Ed. Engl. 1995,
34, 2273. (c) McKnight, A. L.; Waymouth, R. M.
Macromolecules 1999, 32, 2816. (d) Ruchatz, D.; Fink, G.
Macromolecules 1998, 31, 4669. (e) Ruchatz, D.; Fink, G.
Macromolecules 1998, 31, 4681. (f) Ruchatz, D.; Fink, G.
Macromolecules 1998, 31, 4684. (g) Ruchatz, D.; Fink, G.
Macromolecules 1998, 31, 4674.
Synthesis 2004, No. 7, 1052–1056 © Thieme Stuttgart · New York