Coupling of Cyclobutenediones with Fischer Carbene Complexes: A One-Step Synthesis of Cyclopentenediones and/or 5-Alkylidenefuranones via Net Insertion of the Carbene Unit into a C - C Bond

Article abstract of DOI:10.1021/om9905198

The reaction of Fischer carbene - chromium complexes with 3-cyclobutene-1,2-diones has been investigated. In most cases, the major product of the reaction is the C - C bond insertion product, a 2-alkoxy-4-cyclopentene-1,3-dione, accompanied by a minor amount of the partial deoxygenation product, a 4-cyclopentene-1,3-dione. In some cases, 5-alkylidenefuranones are also formed. A mechanism involving oxidative addition of the coordinatively unsaturated Fischer carbene complex followed by acyl migration and reductive elimination was proposed to account for cyclopentenedione formation. Furanone formation was thought to arise via demetalation of the acyl migration product, followed by O-acylation. An electronic dependence was noted for cyclopentenedione/alkylidene - furanone ratio, which was evaluated using the Hammett equation.

Full text of DOI:10.1021/om9905198

Organometallics 1999, 18, 4429-4436
4429
Cou p lin g of Cyclobu ten ed ion es w ith F isch er Ca r ben e
Com p lexes: A On e-Step Syn th esis of Cyclop en ten ed ion es
a n d /or 5-Alk ylid en efu r a n on es via Net In ser tion of th e
1
Ca r ben e Un it in to a C-C Bon d
Metin Zora,2a,b Yuhui Li,2b and J ames W. Herndon*,2b,c,3
Department of Chemistry and Biochemistry, University of Maryland,
College Park, Maryland 20742-2021; Department of Chemistry, Middle East Technical
University, 06531 Ankara, Turkey; and Department of Chemistry and Biochemistry,
New Mexico State University, Las Cruces, New Mexico 88003
Received J uly 6, 1999
The reaction of Fischer carbene-chromium complexes with 3-cyclobutene-1,2-diones has
been investigated. In most cases, the major product of the reaction is the C-C bond insertion
product, a 2-alkoxy-4-cyclopentene-1,3-dione, accompanied by a minor amount of the partial
deoxygenation product, a 4-cyclopentene-1,3-dione. In some cases, 5-alkylidenefuranones are
also formed. A mechanism involving oxidative addition of the coordinatively unsaturated
Fischer carbene complex followed by acyl migration and reductive elimination was proposed
to account for cyclopentenedione formation. Furanone formation was thought to arise via
demetalation of the acyl migration product, followed by O-acylation. An electronic dependence
was noted for cyclopentenedione/alkylidene-furanone ratio, which was evaluated using the
Hammett equation.
In tr od u ction
Sch em e 1
Fischer carbene complexes have emerged as powerful
4
tools in organic synthesis. An early and continuing
aspect of these studies has been the use of Fischer
carbene complexes as substitutes for simple carbenes
or carbenoids in classical reaction processes of these
reactive intermediates. Many examples utilizing Fischer
carbene complexes in the most notable carbene reaction,
5
cyclopropanation of alkenes, have been reported. Imita-
tions of other simple carbene reactions, including C-H
6
7
insertion, other element-H insertion, and Wagner-
8
Meerwein-type shifts, have also been demonstrated.
Lesser known are C-C bond insertion processes. In
a recent study, the coupling of cyclobutenediones and
1
1
,9
Fischer carbene complexes was reported. The reaction
produces cyclopentenediones (e.g., 3 and 4, Scheme 1),
which are the product of a net insertion of the carbene
unit into the acyl-acyl bond of the cyclobutenedione.
This article constitutes a more detailed study of the
coupling of cyclobutenediones with Fischer carbene
complexes.
(
1) For a preliminary account of this work, see: Zora, M.; Herndon,
J . W. Organometallics 1993, 12, 248-249.
2) (a) Middle East Technical University. (b) University of Maryland.
c) New Mexico State University.
3) Address all correspondence to this author at New Mexico State
University.
(
(
(
(4) Numerous reviews of the use of Fischer carbene complexes in
organic synthesis have appeared; the most recent include: (a) D o¨ tz,
K. H.; Tomuschat, P. Chem. Soc. Rev. 1999, 28, 187-198. (b) Wulff,
W. D. Organometallics 1998, 17, 3116-3134. (c) Harvey, D. F.; Sigano,
D. M. Chem. Rev. 1996, 96, 271-288. (d) Aumann, R.; Nienaber, H.
Adv. Organomet. Chem. 1997, 41, 163-242. (e) Hegedus, L. S.
Tetrahedron 1997, 53, 4105-4128.
Resu lts
Cou p lin g of Alk ylca r ben e Com p lexes w ith Cy-
clobu ten ed ion es. The reaction of a variety of cy-
clobutenediones with a variety of Fischer carbene
complexes is presented in Table 1. The reaction of
alkylcarbene complexes with cyclobutenediones pro-
duced a mixture of cyclopentenedione 3 and a lesser
(5) For the most recent paper focusing on Fischer carbene cyclopro-
panations, see: Barluenga, J .; Fernandez-Acebes, A.; Trabanco, A. A.;
Florez, J . J . Am. Chem. Soc. 1997, 119, 7591-7592.
(6) See: Sierra, M. A.; Mache n˜ o, M. J .; S a´ ez, E.; del Amo, J . C. J .
Am. Chem. Soc. 1998, 120, 6812-6813, and references therein.
10
amount of monodeoxygenated cyclopentenedione 4
(7) For recent examples, see: (a) Mak, C. C.; Tse, M. K.; Chan, K.
S. J . Org. Chem. 1994, 59, 3585-3589. (b) Merlic, C. A.; Albaneze, J .
Tetrahedron Lett. 1995, 36, 1007-1110.
(entries A-C, E, and K). Aminocarbene complex 2B
entry B) was somewhat unreactive and afforded adduct
(
(
8) (a) Zora, M.; Herndon, J . W. J . Org. Chem. 1994, 59, 699-701.
(
(
b) Herndon, J . W.; Zhu, Y. Tetrahedron Lett. 1998, 39, 7443-7446.
c) Harvey, D. F.; Neil D. A. Tetrahedron 1993, 49, 2145-2150.
(10) Deoxgenations using low-valent chromium has precedent. (a)
(
9) Zora, M.; Herndon, J . W. Organometallics 1994, 12, 3370-3374.
Tumer, S. U.; Herndon, J . W.; McMullen, L. A. J . Am. Chem. Soc. 1992,
114, 8394-8404. (b) Wulff, W. D.; Kaesler, R. W.; Peterson, G. A.; Tang,
P. C. J . Am. Chem. Soc. 1985, 107, 1060-1062.
To our knowledge, this example and ref 1 are the only examples of
C-C bond insertion by a discrete transition metal-carbene complex.
1
0.1021/om9905198 CCC: $18.00 © 1999 American Chemical Society
Publication on Web 09/16/1999

4
430 Organometallics, Vol. 18, No. 21, 1999
Zora et al.
Ta ble 1. Cou p lin g of Cyclobu ten ed ion es w ith
F isch er Ca r ben e Com p lexes
Sch em e 2
cyclobutenediones
carbene complexes
A R1, R2 ) i-PrO
A R ) CH3, X ) OCH3
B R1 ) i-PrO, R2 ) CH3
C R1 ) CH3, R2 ) Ph
D R1, R2 ) CH3
B R ) CH3, X ) N(CH3)2
C R ) c-C3H5, X ) OCH3
D R ) p-CH3OPh, X ) OCH3
E R ) p-CH3Ph, X ) OCH3
F R ) Ph, X ) OCH3
Sch em e 3
G R ) p-ClPh, X ) OCH3
H R ) p-CF3Ph, X ) OCH3
adducts 3-5 and 14-18
A R1, R2 ) i-PrO, R ) CH3, X ) OCH3 (1A + 2A)
B R1, R2 ) i-PrO, R ) CH3, X ) N(CH3)2 (1A + 2B)
C R1, R2 ) i-PrO, R ) c-C3H5, X ) OCH3 (1A + 2C)
D R1, R2 ) i-PrO, R ) Ph, X ) OCH3 (1A + 2F )
E R1 ) i-PrO, R2 ) CH3, R ) CH3, X ) OCH3 (1B + 2A)
F R1 ) CH3, R2 ) i-PrO, R ) p-CH3OPh, X ) OCH3 (1B + 2D)
G R1 ) CH3, R2 ) i-PrO, R ) p-CH3Ph, X ) OCH3 (1B + 2E)
H R1 ) CH3, R2 ) i-PrO, R ) Ph, X ) OCH3 (1B + 2F )
I R1 ) CH3, R2 ) i-PrO, R ) p-ClPh, X ) OCH3 (1B + 2G)
J R1 ) CH3, R2 ) i-PrO, R ) p-CF3Ph, X ) OCH3 (1B + 2H)
K R1 ) CH3, R2 ) Ph, R ) CH3, X ) OCH3 (1C + 2A)
L R1, R2 ) CH3, R ) p-CF3Ph, X ) OCH3 (1D + 2H)
cyclo-
butenedione
carbene
complex
entry
yield 3
yield 4
yield 5a
arylcarbene complexes (entries F-J ) afforded mixtures
of cyclopentenediones 3 and 4 and alkylidenefuranones
A
B
C
D
E
F
G
H
I
1A
1A
1A
1A
1B
1B
1B
1B
1B
1B
1C
1D
2A
2B
2C
2F
2A
2D
2E
2F
2G
2H
2A
2H
31
12
34
0
25
37
29
20
19
15
20
8
14
0
17
0
16
30
27
21
23
15
15
7
0
0
0
55
0
11
15
14
22
29
0
5
. The cyclopentenedione/alkylidenefuranone ratio was
insensitive to the reaction time, and neither the pure
alkylidenefuranone nor the pure cyclopentenedione
underwent interconversion under the reaction condi-
12
tions. Coupling of nonoxygenated cyclobutenedione 1D
with arylcarbene complex 2H (entry L) afforded only
cyclopentenediones 3L and 4L in low yield.
J
K
L
Rea ction of Oth er Sm a ll-Rin g Su bstr a tes w ith
Ca r ben e Com p lexes. A variety of other strained ring
systems were tested in their reaction with carbene
complex 2A. Diphenylcyclopropenone (6) was the only
compound that appeared to form a C-C bond insertion
product (Scheme 3), and the reaction of this compound
with a variety of carbene complexes has been reported.9
Benzoyl cycanide (9) did not form an adduct with
carbene complex 2A in refluxing dioxane. Other strained
ring-containing compounds, including tetraphenylcy-
clopentadienone (10), donor-acceptor-substituted cy-
clopropane 11, and cyclobutenone 12, did not form an
adduct with carbene complex 2A.
0
a
Combined yield of E- and Z-isomers; in all cases a nearly 1:1
E:Z mixture was obtained.
3
B11 only in low yield; this is the only case where the
reduced cyclopentenedione 4 was not observed. In most
cases, adducts were produced in good to moderate total
yield; however much lower yields were observed in
couplings involving nonoxygenated cyclobutenediones
(entries K, L).
Cou p lin g of Ar ylca r ben e Com p lexes w ith Cy-
clobu ten ed ion es. The reaction of arylcarbene com-
plexes and cyclobutenediones (entries D and F-J )
afforded 5-alkylidenefuranone derivatives (5) and/or
cyclopentenedione derivatives (3 or 4) (Scheme 2).
Reaction of dioxygenated cyclobutenedione 1A with
phenylcarbene complex 2F (entry D) afforded exclu-
sively the 5-alkylidenefuranone derivative 5D as a 1.1:1
E:Z mixture of alkene stereoisomers. The reaction of
monooxygenated cyclobutenedione 1B with a variety of
Discu ssion
F or m a tion of Cyclop en ten ed ion es (3). The mech-
anism proposed for the formation of cyclopentenediones
(12) (a) For interconversion via thermolysis, see: Claisen, L.; Ewan,
T. J ustus Liebigs Ann. Chem. 1895, 284, 245-299. (b) For intercon-
version via base, see: Gedge, D. R.; Pattenden, G. J . Chem. Soc., Chem.
Commun. 1978, 880-882. (c) For utilization of this interconversion
for organic synthesis, see: Campbell, A. C.; Maidment, M. S.; Pick, J .
H.; Stevenson, D. F. M. J . Chem. Soc., Perkin Trans. 1 1985, 1567-
1576.
(11) For an alternative synthesis of 2-amino-1,3-cyclopentenediones,
see: Sun, L. J .; Liebeskind, L. S. J . Org. Chem. 1994, 59, 6856-6858.

Coupling of Cyclobutenediones
Sch em e 4
Organometallics, Vol. 18, No. 21, 1999 4431
furanone ring occurs in the narrow chemical shift range
of δ 1.90-2.01 on all the isomers of 5F -H. Additional
support for this structural assignment is from the
carbon-13 NMR spectrum. Compounds 5F -J all feature
one carbon signal in the range 161.5-163.0, which is
consistent with the asterisked carbon in the highly
polarized â-alkoxy-R,â-unsaturated carbonyl linkage of
1
5
5
F -J . The alkene carbons in the R-hydroxy-R,â-
1
6
unsaturated ester system occur at less than δ 140.
F or m a tion of Alk ylid en efu r a n on es (5). The for-
mation of alkylidenefuranones was observed only in the
coupling of arylcarbene complexes with cyclobutenedi-
ones. The alkylidenefuranone was the exclusive product
from the coupling of phenylcarbene complex 2F with
dioxygenated cyclobutenedione 1A; however mixtures
of alkylidenefuranones and cyclopentenediones were
observed in the coupling of monooxygenated cyclobutene-
dione 1B and arylcarbene complexes 2D-H. Coupling
of unoxygenated cyclobutenedione 1D and arylcarbene
complex 2H afforded only cyclopentenediones 3L and
4L in low yield; no alkylidenefuranones were observed
from this coupling. In all cases, the alkylidenefuranone
was a nearly 1:1 mixture of E- and Z-stereoisomers.
The interconversion of cyclopentenediones and alkyl-
idenefuranones is a well-documented process and can
is depicted in Scheme 4. First CO dissociation followed
1
3
by oxidative addition affords the metallacyclopentene-
1
4
dione 14, followed by acyl migration to afford metal-
lacyclohexenedione 15, which affords cyclopentenedione
3
upon reductive elimination. The reaction is inhibited
by the addition of triphenylphosphine to the reaction
mixture, which further supports this mechanism.
F or m a tion of Deoxygen a ted Cyclop en ten ed i-
on es (4). The formation of deoxygenated cyclopentene-
diones (4) is a secondary reaction process and occurs
via a chromium-induced reduction of cyclopentenedione
3
. When cyclopentenedione 3A was an additive in the
coupling of carbene complex 2C with cyclobutenedione
A, partial conversion to deoxygenated cyclopentene-
1
1
2b
12a
dione 4A was observed. Similarly, treatment of cyclo-
pentenedione 3A with chromium hexacarbonyl in re-
fluxing dioxane led to a slow reduction to 4A. Secondary
deoxygenation processes have often been observed in the
reactions of chromium carbene complexes.10 A possible
mechanism involves electron transfer followed by â-
elimination. No deoxygenation was observed in the
amino analogues (entry B) possibly due to the poorer
leaving group ability of an amino group relative to an
alkoxy group.
be induced by either base
or thermolysis.
The
alkylidenefurane/cyclopentenedione ratio was insensi-
tive to reaction time. Furthermore, the conversion of
alkylidenefuranone 5H to cyclopentenedione 3H was not
observed when 5H was heated to 100 °C in dioxane or
heated to 100 °C in dioxane in the presence of chromium
hexacarbonyl, or when 5H was an additive in the
coupling of cyclobutenedione 1B and methylcarbene
complex 2A. These results suggest that alkylidene-
furanones are primary products of the coupling reaction
and do not result from the rearrangement of cyclopen-
tenediones under the conditions of the reaction.
Str u ctu r a l Assign m en t of Alk ylid en efu r a n on es
(
5). A major concern in the structural assignment of the
alkylidenefuranones 5F -H is the placement of the
isopropoxy group on the furanone ring system. Assign-
ment as 5 and not 16 is based primarily on the severe
chemical shift differences of the isopropoxy methyls and
methines in the E and Z isomers of 5F -H. In the Z
isomers, the chemical shift of the isopropyl methyls is
below δ 0.90 in all cases, while the same proton in the
E isomers occurs at δ 1.40-1.42. Similarly, the isopropyl
methines appear at δ 4.39-4.51 in the Z isomers and δ
A possible mechanism for the alkylidenefuranone
formation is depicted in Scheme 5. Migration of the more
electron-deficient acyl group in intermediate metalla-
cyclopentenedione-carbenes 14F -J affords the indi-
cated regioisomer of metallacyclohexenediones 15F -J .
Elimination of chromium affords enolate-acylium in-
termediates 17F -J , which undergo intramolecular O-
1
7
acylation to afford the alkylidenefuranone.
Electr on ic Dep en d en ce on th e Alk ylid en efu -
r a n on e/Cyclop en ten ed ion e Ra tio. There appears to
be an electronic dependence on the alkylidenefuranone/
cyclopentenedione ratio for entries F-J of Table 1 (see
Table 2). More alkylidenefuranone is produced for the
4
.83-4.88 in the E isomers. This large effect has been
attributed to strong anisotropic interaction of the aro-
matic rings and the isopropoxy groups, which would be
predicted for 5 and not 16. The methyl group on the
(
13) This C-C bond is very susceptible to oxidative addition.
Liebeskind, L. S.; J ewell, C. F., J r. J . Organomet. Chem. 1985, 285,
05-319.
14) Similar intermediates have been proposed in unrelated pro-
(15) Anderson, J . R.; Edwards, R. L.; Whalley, A. J . S. J . Chem. Soc.,
Perkin Trans. 1 1982, 215-221.
3
(16) a. Raffauf, R. F.; Zennie, T. M.; Onan, K. D.; Le Quesne, P. W.
J . Org. Chem. 1984, 49, 2714-2718.
(
cesses. (a) Xu, Y.-C.; Challener, C. A.; Dragisch, V.; Brandvold, T. A.;
Peterson, G. A.; Wulff, W. D.; Williard, P. G. J . Am. Chem. Soc. 1989,
11, 7269-7271. (b) Liebeskind, L. S.; Chidambaran, R. J . Am. Chem.
Soc. 1987, 109, 5025-5026.
(17) A similar explanation has been used to explain formation of
cyclopentendiones and alkylidenefuranones in ring expansion of 4-di-
azoalkyl-2-cyclobuten-1-ones. Ohno, M.; Noda, M.; Yamamoto, Y.;
Eguchi, S. J . Org. Chem. 1999, 64, 707-712.
1

4
432 Organometallics, Vol. 18, No. 21, 1999
Zora et al.
Sch em e 5
Sch em e 6
is less clear; when R2 is isopropoxy, the ketene reso-
nance is destabilized relative to the case where R2 is
2
0
methyl; however the effect on the stability of the
acylium ion is not clear.
Su m m a r y
The generality of the direct insertion of Fischer
carbenes into the acyl-acyl bond of cyclobutenediones
has been demonstrated in a variety of electronically
diverse cyclobutenedione derivatives. The reaction leads
to either cyclopentenediones or alkylidenefuranone
derivatives in moderate to good yield in a single step.
A mechanism involving insertion of chromium into the
acyl-acyl bond followed by acyl migration and reductive
elimination was proposed. Alkylidenefuranone forma-
tion was attributed to ionization of the carbon-
chromium bond of metallacyclohexenedione intermedi-
ate to form an enolate, and this process was supported
through a Hammett study.
Ta ble 2. Ha m m ett P a r a m eter s for En tr ies F -J
entrya
% 5x/5H (log)b
3+4/5
σ
σ+
F
G
H
I
6.09
3.73
2.93
1.91
1.03
0.554 (-0.257)
0.831 (-0.082)
1.000 (0)
1.351 (0.125)
1.936 (0.284)
-0.268
-0.170
0
0.227
0.54
-0.648
-0.250
0
0.035
0.582
2
1
J
a
The entry letters match those in Table 1. b The % 5x is the %
yield of 5x divided by the sum of the % yields of 3x, 4x, and 5x;
the % 5H is 25.4%.
carbene complexes featuring electron-deficient aromatic
rings. A Hammett plot for log of % alkylidenefuranone
Ar-X/Ar-H gives a F of 0.61 (correlation coefficient )
Exp er im en ta l Section
0
0
.95) using σ values and 0.45 (correlation coefficient )
1
Gen er a l Con sid er a tion s. Nuclear magnetic resonance ( H
+
18
.96) using σ values. The observed F values are
13
and C) spectra were recorded on a Bruker AF200 (200 MHz)
supportive of the mechanism in Scheme 5, where there
is significant negative charge development in the vicin-
ity of the aryl group. Since R-aryl groups significantly
enhance the acidity of ketones,19 this could also explain
the absence of alkylidenefuranones in the coupling of
cyclobutenediones with alkylcarbene complexes 2A-C
or Bruker AF400 (400 MHz) spectrometer. Chemical shifts are
reported in parts per million (δ) downfield from an internal
tetramethylsilane reference. Coupling constants (J values) are
reported in hertz (Hz), and spin multiplicities are indicated
by the following symbols: s (singlet), d (doublet), t (triplet), q
(quartet), m (multiplet). Infrared spectra were recorded on a
Nicolet 5DXC FT-IR spectrometer. Band positions are reported
(entries A-C, E, K). Alternatively, enolate-ketene 17
-1
in reciprocal centimeters (cm ). Band intensities are reported
relative to the most intense band and are listed as br (broad),
vs (very strong), s (strong), m (medium), w (weak). Mass
spectra (MS) were obtained on a VG 7070E spectrometer using
electron impact (EI) or chemical ionization (CI) or on a
Hewlett- Packard GC-Mass Spec 5970B with mass selection
detector; m/e values are reported, followed by the relative
intensity in parentheses. Flash column chromatography was
performed using thick-walled glass columns and “flash grade”
silica (Bodmann 230-400 mesh). Routine thin-layer chroma-
tography (TLC) was performed by using precoated 0.25 mm
silica gel plates purchased from Whatman. The relative
proportion of solvents in mixed chromatography solvents refers
to the volume/volume ratio. All commercially available re-
agents and reactants were obtained in reagent grade and used
without purification. All reaction solvents were distilled for
purity. Diethyl ether, THF, and dioxane were distilled from
sodium/benzophenone ketyl, and dichloromethane was distilled
from calcium hydride prior to use. All reactions were performed
in an inert atmosphere created by a slight positive pressure
might be an intermediate in all of the reaction processes,
and the alkylidenefuranone/cyclopentenedione ratios
would thus reflect the O-Vs C-acylation ratios for the
enolate species.
The structure of the cyclobutenedione starting mate-
rial also has an effect on the product distribution. Only
the alkylidenefuranone 5D was obtained in the coupling
of phenylcarbene complex 2F with dioxygenated cy-
clobutenedione 1A (entry D). Mixtures of alkylidene-
furanones and cyclopentenediones were obtained from
the coupling of arylcarbene complexes 2D-H with
monooxygenated cyclobutenedione 2D (entries F-J ),
while only cyclopentenediones were obtained from the
coupling of arylcarbene complex 2H with unoxygenated
cyclobutenedione 1D (entry L). A possible rationale for
the absence of alkylidenefuranone in entry L is the
absence of resonance stabilization of the ketene species
in 17L by the oxygen substituent (exhibited by reso-
nance structure 18 in Scheme 6). As noted in the
comparison of entry D with entry H, the R2 substituent
also has a dramatic effect on the alkylidenefuranone/
cyclopentenedione ratio. The rationale for this difference
(
ca. 0.1 psi) of nitrogen. Cyclobutenediones 1A-D were
22
prepared according to literature procedures. Carbene complex
2
1
0a
C was prepared according to a literature procedure.
(20) Gong, L.; McAllister, M. A.; Tidwell, T. T. J . Am. Chem. Soc.
1
991, 113, 6021-6028.
(
18) Gordon, A. J .; Ford, R. A. The Chemist’s Companion; J ohn Wiley
and Sons: New York, 1972; pp 145-147.
19) Bordwell, F. G.; Harrelson, J . A., J r. Can. J . Chem. 1990, 68,
714-1718.
(21) For a general discussion of the synthesis and importance of
cyclopentenediones, see refs 11, 12, 14, and 17.
(22) Liebeskind, L. S.; Fengl, R. W.; Wirtz, K. R.; Shawe, T. T. J .
Org. Chem. 1988, 53, 2482-2488.
(
1

Coupling of Cyclobutenediones
Organometallics, Vol. 18, No. 21, 1999 4433
Gen er a l P r oced u r e I. P r ep a r a tion of Ca r ben e Com -
p lexes. At - 78 °C and under nitrogen, a solution of tert-
butyllithium (1.7 M in pentanes, 11.7 mL, 20.0 mmol) was
added to a solution of corresponding alkyl bromide (10.0 mmol)
in diethyl ether (25 mL) via syringe over a period of 15 min.
The mixture was stirred for 30 min at -78 °C and then
transferred via cannula to a suspension of metal hexacarbonyl
3.86 (s, 3 H). The spectral data are in agreement with those
reported previously for this compound.26
P en ta ca r bon yl[(4-m eth ylp h en yl)m eth oxym eth ylen e]-
ch r om iu m (2E). General procedure I was followed using
4-tolyl bromide (1.71 g, 10.0 mmol), tert-butyllithium (11.7 mL
of 1.7 M pentane solution, 20.0 mmol), chromium hexacarbonyl
(2.20 g, 10.0 mmol), and methyl trifluoromethanesulfonate (3.4
mL, 30 mmol). After chromatographic purification, the red
fraction was collected to give carbene complex 2E (2.28 g, 70%).
(10.0 mmol) in diethyl ether (50 mL) at 0 °C. (If commercially
available, the corresponding alkyllithium (10.0 mmol) was
added directly to a suspension of metal hexacarbonyl (10.0
mmol) in diethyl ether (50 mL) at 0 °C under nitrogen over a
period of 15 min.) The reaction mixture was allowed to warm
to room temperature and then stirred for 1 h. The mixture
was cooled to 0 °C and methyl trifluoromethanesulfonate (3.4
mL, 30 mmol) was added. The mixture was stirred at room
temperature for 20 min. The reaction mixture was poured into
saturated aqueous sodium bicarbonate solution in a separatory
funnel and then extracted with hexane (3 × 100 mL). The
hexane layer was washed with water and saturated aqueous
sodium chloride solution, respectively. After drying over
sodium sulfate, the solvent was removed on a rotary evapora-
tor. The crude oil was purified by flash chromatography on
silica gel using hexane as the eluent.
1
2E: H NMR (CDCl ) δ 7.36-7.17 (m, 4 H), 4,74 (s, 3 H),
3
2.37 (s, 3 H). The spectral data are in agreement with those
reported previously for this compound.26
P en t a ca r b on yl[(p h en yl)m et h oxym et h ylen e]ch r om i-
u m (2F ). General procedure I was followed using phenyl-
lithium (5.6 mL of a 1.8 M cyclohexanes/ether solution, 10.0
mmol), chromium hexacarbonyl (2.20 g, 10.0 mmol), and
methyl trifluoromethanesulfonate (3.4 mL, 30 mmol). After
chromatographic purification, the red fraction was collected
to give carbene complex 2F (2.03 g, 65%).
F : 1H NMR (CDCl
064 (vs), 1986 (m), 1951 (vs) cm . The spectral data are in
2
3
4
) δ 7.35 (m, 5 H), 4.65 (s, 3 H); IR (Ccl )
-1
2
26
agreement with those reported previously for this compound.
P en ta ca r bon yl[(4-ch lor op h en yl)m eth oxym eth ylen e]-
ch r om iu m (2G). General procedure I was followed using
4-chlorobromobenzene (1.91 g, 10.0 mmol), n-butyllithium
(6.25 mL of 1.6 M pentane solution, 10.0 mmol), chromium
hexacarbonyl (2.20 g, 10.0 mmol), and methyl trifluoromethane-
sulfonate (3.4 mL, 30 mmol). After chromatographic purifica-
tion, the red fraction was collected to give carbene complex
2G (1.73 g, 50%).
P en t a ca r b on yl[(m et h yl)m et h oxym et h ylen e]ch r om i-
u m (2A). General procedure I was followed using methyl-
lithium (6.7 mL of a 1.5 M diethyl ether solution, 10.00 mmol),
chromium hexacarbonyl (2.200 g, 10.00 mmol), and methyl
trifluoromethanesulfonate (3.4 mL, 30.00 mmol). After chro-
matographic purification, the yellow fraction was collected to
give carbene complex 2A (mp 33-34 °C, 1.400 g, 56%).
1
2G: 1H NMR (CDCl
The spectral data are in agreement with those reported
previously for this compound.
) δ 7.40-7.28 (m, 4 H), 4.77 (s, 3 H).
2
A: H NMR (CDCl
3
) δ 5.35 (s, 3 H), 4.65 (s, 3 H); IR (CCl
4
)
3
-
1
2
064 (vs), 1985 (s), 1948 (vs) cm . The spectral data are in
agreement with those reported previously for this compound.
2
3
26
Since the acquisition of these data, we have verified that the
more economical procedure using dimethyl sulfate as the
methylating agent, developed by Wulff and co-workers,24 is
applicable to the synthesis of this carbene complex.
P e n t a ca r b on yl[(4-t r iflu or om e t h ylp h e n yl)m e t h oxy-
m eth ylen e]ch r om iu m (2H). General procedure I was fol-
lowed using 4-trifluoromethylbromobenzene (2.24 g, 10.0
mmol), n-butyllithium (6.25 mL of 1.6 M pentane solution, 10.0
mmol), chromium hexacarbonyl (2.20 g, 10.0 mmol), and
methyl trifluoromethanesulfonate (3.4 mL, 30 mmol). After
chromatographic purification, the red fraction was collected
P en t a ca r b on yl[m et h yl(d im et h yla m in o)m et h ylen e]-
ch r om iu m (2B). A solution of carbene complex 2A (0.750 g,
3
.00 mmol) and dimethylamine (0.38 mL of a 40 wt % solution
to give carbene complex 2H (1.90 g, 50%).
in water, 3.00 mmol) in THF (25 mL) was stirred at room
temperature for a period of 30 min. The mixture was stirred
at room temperature for 30 min. The reaction mixture was
poured into saturated aqueous sodium bicarbonate solution
in a separatory funnel and then extracted with hexane. The
hexane layer was washed with water and saturated aqueous
sodium chloride solution, respectively. After drying over
sodium sulfate, the solvent was removed on a rotary evapora-
tor. The crude oil was purified by flash chromatography on
silica gel using 9:1 hexane/ethyl acetate as the eluent. The
fraction was collected to give carbene complex 2B (mp 74-75
1
2
H: H NMR (CDCl
3
) δ 7.68-7.24 (m, 4 H), 4.72 (s, 3 H).
The spectral data are in agreement with those reported
previously for this compound.26
Gen er a l P r oced u r e II: Cou p lin g of Ca r ben e Com -
p lexes w ith Cyclobu ten ed ion es. Rea ction of Ca r ben e
Com p lex 2F w ith 3-Isop r op oxy-4-m eth yl-3-cyclobu ten e-
1,2-d ion e (1B). A solution of cyclobutenedione 1B (1.00 mmol)
and carbene complex 2F (1.20 mmol) in dioxane (5 mL) was
heated to reflux under nitrogen for a period of 4 h. The mixture
was allowed to cool to room temperature, and the solvent was
removed on a rotary evaporator. The residue was dissolved in
9:1 hexane/ethyl acetate (25 mL) and filtered through Celite.
After removal of solvent on a rotary evaporator, final purifica-
tion was achieved by flash chromatography on silica gel using
19:1 hexane/ethyl acetate as the eluent.
°
C, 0.570 g, 76%).
B: 1H NMR (CDCl
) δ 3.86 (s, 3 H), 3.29 (s, 3 H), 2.67 (s,
2
3
-1
3
H); IR (CCl ) 2054 (vs), 1970 (vs), 1923 (vs) cm . The spectral
4
data are in agreement with those reported previously for this
2
5
compound.
Rea ction of Ca r ben e Com p lex 2A w ith 3,4-Diisop r o-
p oxy-3-cyclobu ten e-1,2-d ion e (1A): En tr y A of Ta ble 1.
General procedure II was followed using cyclobutenedione 1A
P en tacar bon yl[(4-m eth oxyph en yl)m eth oxym eth ylen e]-
ch r om iu m (2D). General procedure I was followed using
4
-bromoanisole (1.87 g, 10.0 mmol), tert-butyllithium (11.7 mL
of 1.7 M pentane solution, 20.0 mmol), chromium hexacarbonyl
2.20 g, 10.0 mmol), and methyl trifluoromethanesulfonate (3.4
(0.198 g, 1.00 mmol) and carbene complex 2A (0.325 g, 1.30
mmol). After chromatographic purification, two fractions were
isolated. The product in the first fraction was assigned as 4,5-
diisopropoxy-2-methyl-4-cyclopentene-1,3-dione (4A) (0.032 g,
(
mL, 30 mmol). After chromatographic purification, the red
fraction was collected to give carbene complex 2D (2.39 g, 70%).
1
4%). The product in the second fraction was identified as 4,5-
2
D: 1H NMR (CDCl
3
) δ 7.75-6.87 (m, 4 H), 4.84 (s, 3 H),
diisopropoxy-2-methoxy-2-methyl-4-cyclopentene-1,3-dione (3A)
(
0.080 g, 31%).
A: 1H NMR (CDCl
) δ 5.48 (septet, 2 H, J ) 6.1 Hz), 3.18
(
23) Fischer, E. O.; Maasb o¨ l, A. Chem. Ber. 1967, 100, 2445-2446.
3
3
(24) Bao, J .; Wulff, W. D.; Dominy, J . B.; Fumo, M. J .; Grant, E. B.;
(
s, 3 H), 1.35 (s, 3 H), 1.32 (d, 6 H, J ) 6.1 Hz), 1.31 (d, 3 H,
Rob, A. C.; Whitcomb, M. C.; Yeung, S.-M.; Ostrander, R. L.; Rheingold,
A. L. J . Am. Chem. Soc. 1996, 118, 3392-3405.
(
25) Moser, E.; Fischer, E. O. J . Organomet. Chem. 1968, 13, 387-
(26) Fischer, E. O.; Kreiter, C. G.; Kollmeier, H. J .; M u¨ ller, J .;
Fischer, R. D. J . Organomet. Chem. 1971, 28, 237-258.
3
98.

4
434 Organometallics, Vol. 18, No. 21, 1999
Zora et al.
J ) 6.1 Hz); 13C NMR (CDCl
) δ 194.9, 150.1, 77.3, 74.8, 53.2,
21.9; IR (CDCl
) 1746 (vs), 1628 (s) cm-1; MS (EI) 318 (M+,
3
3
-
1
2
2.9, 19.2; IR (CDCl ): 1688 (vs), 1601 (vs) cm ; MS (EI) 256
M+, 25), 214 (59), 172 (100), 143 (24), 115 (21), 97 (13), 84
10), 75 (10), 69 (10), 55 (30); HRMS calcd for C13
56.1311, found 256.1301.
3
100), 276 (50), 234 (64), 191 (36), 177 (19), 161 (18), 146 (13),
105 (22), 77(10); HRMS calcd for C18 318. 1467, found
(
(
2
22 5
H O
H
20
O
5
318.1511. Compound 5F-Z was assigned as the Z isomer
because of the upfield shift of an isopropyl secondary H (δ 4.82
in the Z isomer versus δ 5.16 and 4.89 in the E isomer) and
methyl (δ 0.84 and 1.18 in the Z isomer versus δ 1.24 and 1.35
in the E isomer) and might be attributed to anisotropic
interaction with the phenyl ring.
Rea ction of Ca r ben e Com p lex 2A w ith 3-Isop r op oxy-
4-m eth yl-3-cyclobu ten e-1,2-d ion e (1B): En tr y E of Ta ble
1. General procedure II was followed using cyclobutenedione
1B (0.154 g, 1.00 mmol) and carbene complex 2A (0.325 g, 1.30
mmol). After chromatographic purification, two fractions were
isolated. The product in the first fraction was assigned as
4-isopropoxy-2,5-dimethyl-4-cyclopentene-1,3-dione (4E) (0.030
g, 16%). The product in the second fraction was identified as
4-isopropoxy-2-methoxy-2,5-dimethyl-4-cyclopentene-1,3-di-
one (3E) (0.054 g, 25%).
1
4
A: H NMR (CDCl
3
) δ 5.41 (septet, 2 H, J ) 6.1 Hz); 2.71
(
q, 1 H, J ) 7.5 Hz), 1.31 (d, 12 H, J ) 6.1 Hz), 1.20 (d, 3 H,
J ) 7.5 Hz); C NMR (CDCl ) δ 195.9, 149.9, 74.3, 44.8, 22.9,
1.2; IR (CDCl
0), 184 (37), 153 (31), 142 (51), 114 (100), 73 (17), 68 (28);
226.1205, found 226.1220.
1
3
3
-
1
1
1
3
) 1685 (vs), 1609 (m) cm ; MS (EI) 226 (M+,
HRMS calcd for C12
18 4
H O
Rea ction of Ca r ben e Com p lex 2B w ith 3,4-Diisop r o-
p oxy-3-cyclobu ten e-1,2-d ion e (1A): En tr y B of Ta ble 1.
General procedure II was followed using cyclobutenedione 1A
(0.198 g, 1.00 mmol) and carbene complex 2B (0.342 g, 1.30
mmol). After chromatographic purification, a single fraction
was isolated and identified as 4,5-diisopropoxy-2-methyl-2-
(
1
N,N-dimethylamino)-4-cyclopentene-1,3-dione (3B) (0.033 g,
2%).
B: 1H NMR (CDCl
s, 6 H), 1.30 (s, 3 H), 1.27 (d, 12 H, J ) 6.1 Hz); C NMR
3E: 1H NMR (CDCl
(s, 3 H), 1.87 (s, 3 H), 1.31 (s, 3 H), 1.30 (d, 3 H, J ) 6.1 Hz),
1.27 (d, 3 H, J ) 6.1 Hz); 13C NMR (CDCl
) δ 199.0, 198.5,
3
164.3, 137.2, 77.8, 74.8, 53.3, 23.2, 23.1, 19.1, 7.0; IR (CDCl )
1689 (vs), 1608 (s) cm ; MS (EI) 212 (M+, 100), 181 (10), 170
(88), 153 (49), 140 (29), 131 (11), 119 (8), 112 (18); HRMS calcd
) δ 5.59 (septet, 1 H, J ) 6.1 Hz), 3.16
3
3
) δ 5.41 (septet, 2 H, J ) 6.1 Hz), 2.34
3
1
3
(
(
(
(
CDCl
CDCl
3
) δ 198.8, 148.8, 74.4, 65.3, 40.0, 23.0, 22.9, 18.7; IR
3
-
1
3
) 1681 (vs), 1604 (s) cm ; MS (EI) 269 (M+, 67), 227
-
1
34), 216 (68), 198 (57), 185 (26), 174 (100), 145 (23), 128 (83),
1
2
12 (36), 100 (31); HRMS calcd for C14
69.1629.
H
23NO
4
269.1627, found
for C11
4E: 1H NMR (CDCl
(q, 1 H, J ) 7.6 Hz), 1.84 (s, 3 H), 1.28 (d, 3 H, J ) 6.1 Hz),
H
16
O
4
212.1048, found 212.1047.
Rea ction of Ca r ben e Com p lex 2C w ith 3,4-Diisop r o-
p oxy-3-cyclobu ten e-1,2-d ion e (1A): En tr y C of Ta ble 1.
General procedure II was followed using cyclobutenedione 1A
3
) δ 5.49 (septet, 1 H, J ) 6.1 Hz), 2.66
1
3
1.27 (d, 3 H, J ) 6.1 Hz), 1.17 (d, 3 H, J ) 7.6 Hz); C NMR
(CDCl ) δ 200.2, 199.2, 164.8, 136.4, 74.3, 45.7, 23.2, 23.1, 10.9,
7.0; IR (CDCl
37), 166 (6), 153 (20), 149 (7), 141 (58), 140 (100), 122 (26),
111 (19); HRMS calcd for C10 182.0943, found 182.0948.
(0.198 g, 1.00 mmol) and carbene complex 2C (0.359 g, 1.30
3
-
1
mmol). After chromatographic purification, two fractions were
isolated. The product in the first fraction was assigned as
3
) 1689 (vs), 1616 (s) cm ; MS (EI) 182 (M+,
2
-cyclopropyl-4,5-diisopropoxy-4-cyclopentene-1,3-dione (4C)
14 3
H O
(
0.043 g, 17%). The product in the second fraction was
Rea ction of p-Meth oxyp h en ylca r ben e Com p lex 2D
with 3-Isopr opoxy-4-m eth yl-3-cyclobu ten e-1,2-dion e (1B):
En tr y F of Ta ble 1. General procedure II was followed using
cyclobutenedione 1B (0.154 g, 1.00 mmol) and carbene complex
2D (0.410 g, 1.20 mmol). After chromatographic purification,
four fractions were isolated. The product in the first fraction
was assigned as compound 3F (0.112 g, 37%). The product in
the second fraction was identified as compound (4F ) (0.083 g,
30%). The products in the third and fourth fractions were
assigned as compounds 5F -E (0.02 1 g, 7%) and 5F -Z (0.012
g, 4%).
identified as 2-cyclopropyl-4,5-diisopropoxy-2-methoxy-4-cy-
clopentene-1,3-dione (3C) (0.096 g, 34%).
1
3
C: H NMR (CDCl
3
) δ 5.47 (septet, 2 H, J ) 6.1 Hz), 3.27
(s, 3 H), 1.33 (d, 6 H, J ) 6.1 Hz), 1.32 (d, 6 H, J ) 6.1 Hz),
1
1
1
.23 (m, 1 H), 0.56-0.48 (m, 4 H); 13C NMR (CDCl
50.8, 79.8, 74.8, 53.4, 22.9, 14.6, 1.9; IR (CDCl ) 1685 (vs),
601 (vs) cm ; MS (EI) 282 (M+, 37), 251 (15), 240 (89), 209
3
) δ 193.5,
3
-
1
(
1
14), 198 (100), 183 (13), 168 (14), 155 (10), 142 (24), 125 (23),
10 (44); HRMS calcd for C15 282.1467, found 282.1467.
) δ 5.40 (septet, 2 H, J ) 6.1 Hz), 2.46
d, 1 H, J ) 6.5 Hz), 1.35 (d, 6 H, J ) 6.1 Hz), 1.34 (d, 6 H,
22 5
H O
1
4
C: H NMR (CDCl
3
(
3F : 1H NMR (CDCl
H, J ) 6.1 Hz), 3.76 (s, 3 H), 3.32 (s, 3 H), 1.95 (s, 3 H), 1.36
(d, 3 H, J ) 6.1 Hz), 1.24 (d, 3 H, J ) 6.1 Hz); 13C NMR (CDCl
δ 196.9, 195.8, 165.2, 160.1, 138.4, 128.6, 126.0, 114.0, 81.3,
3
) δ 7.36-6.83 (m, 4 H), 5.62 (septet, 1
1
3
J ) 6.1 Hz), 0.98 (m, 1 H), 0.52-0.43 (m, 4 H); C NMR
CDCl ) δ 194.5, 150.4, 74.3, 50.5, 22,9, 9.6, 1.8; IR (CDCl
686 (vs), 1612 (s) cm-1; MS (EI) 252 (M+, 16), 227 (6), 210
73), 195 (8), 184 (5), 168 (100), 150 (6), 140 (37), 122 (22), 111
22); HRMS calcd for C14 252.1361, found 252.1346.
Rea ction of Ca r ben e Com p lex 2F w ith 3,4-Diisop r o-
(
1
(
(
3
3
)
3
)
-1
75.0, 55.3, 53.9, 23.2, 7.2; IR (CH
MS (EI) 304 (M+, 13), 262 (31), 189 (22), 166 (21), 135 (100),
77 (26); HRMS calcd for C17 304.1311, found 304.1306.
4F : 1H NMR (CDCl
) δ 7.06-6.82 (m, 4 H), 5.58 (septet, 1
H, J ) 5.9 Hz), 3.86 (s, 1 H), 3.75 (s, 3 H), 1.96 (s, 3 H), 1.35
(d, 3 H, J ) 5.9 Hz), 1.32 (d, 3 H, J ) 5.9 Hz); 13C NMR (CDCl
δ 197.5, 196.4, 166.0, 159.2, 138.5, 129.3, 125.2, 114.4, 74.6,
2 2
Cl ) 1691 (vs), 1610 (s) cm ;
20 4
H O
20 5
H O
p oxy-3-cyclobu ten e-1,2-d ion e (1A): En tr y D of Ta ble 1.
General procedure II was followed using cyclobutenedione 1A
3
(0.198 g, 1.00 mmol) and carbene complex 2F (0.406 g, 1.30
3
)
mmol). After chromatographic purification, two fractions were
isolated. The product in the first fraction was assigned as
compound 5D-E (0.093 g, 29%). The product in the second
-
1
56.2, 55.2, 23.1, 7.3; IR (CH
(EI) 274 (M+, 100), 232 (53), 159 (7), 148 (76), 121 (62), 77
(8); HRMS calcd for C16 274.1205, found 274.1209.
5F -E: 1H NMR (CDCl
) δ 7.70-6.90 (m, 4 H), 4.84 (septet,
1 H, J ) 6.1 Hz), 3.79 (s, 3 H), 3.62 (s, 3 H), 1.98 (s, 3 H), 1.40
(d, 6 H, J ) 6.1 Hz); 13C NMR (CDCl
) δ 170.5, 163.0, 160.6,
143.0, 135.5, 130.5, 124.2, 114.0, 103.0, 75.1, 60.6, 55.3, 22.6,
2 2
C1 ) 1692 (vs), 1615 (s) cm ; MS
fraction was identified as compound 5D-Z (0.083 g, 26%).
18 4
H O
1
5
D-E: H NMR (CDCl
3
) δ 7.64 (d, 2 H, J ) 7.1 Hz), 7.36-
3
7
.28 (m, 3 H), 5.16 (septet, 1 H, J ) 6.1 Hz), 4.89 (septet, 1 H,
J ) 6.1 Hz), 3.55 (s, 3 H), 1.35 (d, 6 H, J ) 6.1 Hz), 1.24 (d, 6
H, J ) 6.1 Hz); C NMR (CDCl
1
IR (CDCl ) 1748 (vs), 1626 (s) cm ; MS (EI) 318 (M+, 56),
2
3
1
3
3
) δ 164.5, 150.3, 143.2, 134.5,
-
1
31.8, 130.5, 128.8, 128.4, 122.8, 74.4, 73.7, 60.5, 22.7, 22.5;
8.8; IR (CH
65), 262 (27), 189 (17), 166 (16), 135 (100), 77 (14); HRMS calcd
for C17 304.1311, found 304.1308.
5F -Z: 1H NMR (CDCl
) δ 7.32-6.87 (m, 4 H), 4.40 (septet,
1 H, J ) 6.1 Hz), 3.83 (s, 3 H), 3.65 (s, 3 H), 1.90 (s, 3 H), 0.89
2 2
C1 ) 1751 (vs), 1604 (s) cm ; MS (EI) 304 (M+,
-
1
3
76 (64), 234 (100), 191 (57), 177 (27), 161 (27), 146 (22), 105
20 5
H O
(30), 77 (19); HRMS calcd for C18 318. 1467, found
H
22
O
5
3
3
18.1477.
D-Z: 1H NMR (CDCl
H, J ) 6.1 Hz), 3.57 (s, 3 H), 1.18 (d, 6 H, J ) 6.1 Hz), 0.84
13
5
3
) δ 7.35-7.25 (m, 5 H), 4.82 (septet,
(d, 6 H, J ) 6.1 Hz); C NMR (CDCl ) δ 170.6, 162.1, 160.9,
3
2
142.3, 132.0, 129.1, 123.5, 113.2, 100.7, 73.9, 58.5, 55.4, 21.9,
8.9; IR (CH C1 ) 1744 (vs), 1605 (vs) cm ; MS (EI) 304 (M+,
2 2
42), 262 (17), 189 (14), 166 (16), 135 (100), 83 (43); HRMS calcd
1
3
-1
(
1
d, 6 H, J ) 6.1 Hz); C NMR (CDCl
3
) δ 164.3, 149.7, 141.9,
31.0, 130.5, 129.5, 128.3, 127.6, 121.4, 73.7, 73.5, 58.4, 22.5,

Coupling of Cyclobutenediones
304.1311, found 304.1299. Compound 5C-Z was
assigned as the Z isomer because of the upfield shift of an
isopropyl secondary H (δ 4.40 in the Z isomer versus δ 4.84 in
the E isomer) and methyl (δ 0.89 in the Z isomer versus δ
Organometallics, Vol. 18, No. 21, 1999 4435
for C17
H
20
O
5
1750 (vs), 1611 (s) cm-1; MS (EI) 274 (M+, 100), 232 (50), 217
(8), 202 (9), 175 (10), 159 (30), 148 (10), 121 (15), 120 (18), 105
(99); HRMS calcd for C16
H
18
O
4
274.1205, found 274.1205.
5H-Z: 1H NMR (CDCl
) δ 7.50-7.30 (m, 511), 4.41 (septet,
3
1
.40 in the E isomer) and might be attributed to anisotropic
111, J ) 6.1 Hz), 3.66 (s, 311), 1.90 (s, 311), 0.84 (d, 611, J )
6.1 Hz); 13C NMR (CDCl
) δ 170.0, 162.0, 142.4, 131.5, 130.5,
129.6, 127.8, 100.3, 73.8, 58.5, 21.8, 8.9; IR (CDCl4) 1744 (vs),
interaction with the phenyl ring.
3
Rea ction of p-Tolylca r ben e Com p lex 2E w ith 3-Iso-
p r op oxy-4-m eth yl-3-cyclobu ten e-l,2-d ion e (1B): En tr y G
of Ta ble 1. General procedure II was followed using cy-
clobutenedione 1B (0.154 g, 1.00 mmol) and carbene complex
-
1
1611 (s) cm ; MS (EI) 274 (M+, 94), 232 (45), 217 (8), 202 (8),
175 (9), 159 (26), 148 (10), 137 (6), 121 (12), 120 (17), 105 (100);
HRMS calcd for C16
18 4
H O 274.1205, found 274.1187.
2
E (0.391 g, 1.20 mmol). After chromatographic purification,
Rea ction of p-Ch lor op h en ylca r ben e Com p lex 2G w ith
3-Isop r op oxy-4-m eth yl-3-cyclobu ten e-1,2-d ion e (1B): En -
tr y I of Ta ble 1. General procedure II was followed using
cyclobutenedione 1B (0.154 g, 1.00 mmol) and carbene complex
2G (0.416 g, 1.20 mmol). After chromatographic purification,
four fractions were isolated. They were assigned as 3I (0.057
g, 19%), 4I (0.063 g, 23%), 5I-E (0.040 g, 13%), and 5I-Z (0.029
g, 9%).
four fractions were isolated. They were assigned as 3G (0.083
g, 29%), 4G (0.069 g, 27%), 5G-E (0.023 g, 8%), and 5G-Z
(
0.019 g, 7%).
G: 1H NMR (CDCl
H, J ) 6.1 Hz), 3.34 (s, 3 H), 2.3 (s, 3 H), 1.96 (s, 3 H), 1.36 (d,
3
3
) δ 7.30-7.11 (m, 4 H), 5.62 (septet, 1
1
3
3
H, J ) 6.1 Hz), 1.25 (d, 3 H, J ) 6.1 Hz); C NMR (CDCl
3
)
δ 196.8, 195.7, 165.4, 138.9,138.6, 131.2, 129.2, 127.0, 81.8,
-1
3I: 1H NMR (CDCl
H, J ) 6.1 Hz), 3.33 (s, 3 H), 1.98 (s, 3 H), 1.37 (d, 3 H, J ) 6.1
) δ 196.2, 195.2,
7
5.0, 53.9, 23.2, 21.1, 7.2; IR (CH
MS (EI) 288 (M+, 32), 246 (17), 216 (5), 189 (9), 173 (18), 135
10), 119 (100), 91(39), 83 (45), 65 (16); HRMS calcd for
288.1362, found 288.1363.
G: 1H NMR (CDCl
) δ 7.14-6.98 (m, 4 H), 5.57 (septet, 1
H, J ) 6.1 Hz), 3.89 (s, 3 H), 2.29 (s, 3 H), 1.97 (s, 3 H), 1.35
d, 3 H, J ) 6.1 Hz), 1.32 (d, 3 H, J ) 6.1 Hz); 13C NMR (CDCl
δ 197.3, 196.3, 166.1, 138.6, 137.6, 130.2, 129.6, 128.1, 74.7,
2
C1
2
) 1691 (vs), 1612 (s) cm
;
3
) δ 7.33-7.32 (m, 4 H), 5.63 (septet, 1
Hz), 1.27 (d, 3 H, J ) 6.1 Hz); 13C NMR (CDCl
(
C
3
17
H
20
O
4
182.6, 139.2, 135.2, 132.8, 128.9, 128.5, 81.3, 75.3, 54.0, 23.2,
-1
4
3
2 2
7.3; IR (CH Cl ) 1691 (vs), 1611 (s) cm ; MS (EI) 308 (M+,
100), 266 (58), 236 (10), 195 (9), 139 (5), 111 (8), 51(4); HRMS
35
(
3
)
calcd for C16
H
17
O
4
C1 308.0815, found 308.0802.
) δ 7.32-7.05 (m, 4 H), 5.58 (septet, 1
1
4I: H NMR(CDCl
3
-
1
5
6.7, 23.2, 21.1, 7.3; IR (CH
2
C1
2
) 1693 (vs), 1618 (s) cm ; MS
H, J ) 5.6 Hz), 3.91 (s, 3 H), 1.97 (s, 3 H), 1.36 (d, 3 H, J ) 5.6
) δ 196.6, 195.5,
Hz), 1.33 (d, 3 H, J ) 5.6 Hz); 13C NMR (CDCl
(
EI) 258 (M+, 78), 216 (50), 159 (3), 132 (100), 105 (74), 78
3
(9); HRMS calcd for C16
H
18
O
3
258.1256, found 258.1254.
156.0, 138.7, 133.9, 131.5, 129.7, 129.0, 74.9, 56.1, 23.2, 7.4;
1
-1
5
G-E: H NMR (CDCl
3
) δ 7.63-7.18 (m, 4 H), 4. 83 (septet,
2 2
IR (CH Cl ) 1682 (vs), 1615 (s) cm ; MS (EI) 278 (M+, 52),
1
H, J ) 6.1 Hz), 3.61 (s, 3 H), 2.36 (s, 3 H), 1.98 (s, 3 H), 1.41
236 (58), 163 (10), 152 (100), 125 (40), 89 (21), 63 (4); HRMS
1
3
35
(d, 6 H, J ) 6.1 Hz); C NMR (CDCl
3
) δ 170.4, 163.0, 143.1,
calcd for C15
5I-E: 1H NMR(CDCl
2 H, J ) 8.7 Hz), 4.85 (septet, 1 H, J ) 6.1 Hz), 3.63 (s, 3 H),
1.99 (s, 3 H), 1.40 (d, 6 H, J ) 6.1 Hz); 13C NMR (CDCl
) δ
170.1, 162.8, 141.5, 136.9, 135.5, 130.5, 130.1, 128.8, 103.5,
H
15
O
3
C1 278.0710, found 278.0702.
1
8
3
9
39.8, 136.0, 129.2, 128.9, 128.8, 103.4, 75.1, 60.5, 22.6, 21.4,
3
) δ 7.67 (d, 2 H, J ) 8.7 Hz), 7.37 (d,
-
1
.7; IR (CH
3), 246 (22), 216 (10), 189 (9), 173 (27), 132 (13), 119 (100),
1(38), 83 (47), 65 (15); HRMS calcd for C17 288.1362,
2 2
C1 ) 1753 (vs), 1608 (s) cm ; MS (EI) 288 (M+,
3
20 4
H O
-
1
found 288.1373.
G-Z: 1H NMR (CDCl
H, J ) 6.0 Hz), 3.64 (s, 3 H), 2.38 (s, 3 H), 1.90 (s, 3 H), 0.86
2 2
75.1, 60.8, 22.7, 8.9; IR (CH Cl ) 1759 (s), 1613 (s) cm ; MS
5
3
) δ 7.27-7.15 (m, 4 H), 4.39 (septet,
(EI) 308 (M+, 44), 266 (26), 193 (27), 181 (49), 169 (44), 139
1
(100), 131 (96), 119 (79), 83 (76), 69 (331); HRMS calcd for
1
3
35
(
1
d, 6 H, J ) 6.0 Hz); C NMR (CDCl
3
) δ 170.1, 162.1, 142.7,
16 17 4
C H O C1 308.0815, found 308.0820.
1
39.8, 130.5, 128.5, 100.5, 73.9, 58.4, 21.8, 21.4, 8.9; IR (CH
2
2
-
5I-Z: H NMR(CDCl
H, J ) 6.1 Hz), 3.68 (s, 3 H), 1.91 (s, 3 H), 0.90 (d, 6 H, J ) 6.1
Hz); 13C NMR (CDCl
) δ 169.9, 161.5, 141.0, 135.7, 131.8,
130.1, 128.3, 128.0, 99.9, 73.9, 58.9, 22.0, 9.0; IR (CH C1 ) 1749
3
) δ 7.36-7.29 (m, 4 H), 4.49 (septet, 1
-
1
C1 ) 1748 (vs), 1609 (s) cm ; MS (EI) 288 (M+, 72), 246 (32),
1
2
89 (12), 173 (22), 119 (100), 91(34); HRMS calcd for C17
88.1362, found 288.1364.
H
20
O
4
3
2
2
-
1
Rea ction of P h en ylca r ben e Com p lex 2F w ith 3-Iso-
(s), 1616 (m) cm ; MS (EI) 308 (M+, 44), 266 (27), 193 (27),
141 (37), 139 (100), 131 (37), 119 (32), 69 (123); HRMS calcd
p r op oxy-4-m eth yl-3-cyclobu ten e-1,2-d ion e (1B): En tr y H
of Ta ble 1. General procedure II was followed using cy-
clobutenedione 1B (0.154 g, 1.00 mmol) and carbene complex
3
5
for C16
17 4
H O C1 308.0815, found 308.0829.
Rea ction of p-Tr iflu or om eth ylp h en ylca r ben e Com -
p lex 2H w ith 3-Isop r op oxy-4-m eth yl-3-cyclobu ten e-1,2-
d ion e (1B): En tr y J of Ta ble 1. General procedure II was
followed using cyclobutenedione 1B (0.154 g, 1.00 mmol) and
carbene complex 2H (0.456 g, 1.20 mmol). After chromato-
graphic purification, four fractions were isolated. They were
assigned as 3J (0.051 g, 15%), 4J (0.047 g, 15%), 5J -E (0.045
g, 16%), and 5J -Z (0.037 g, 13%).
2
F (0.375 g, 1.20 mmol). After chromatographic purification,
four fractions were isolated. They were assigned as 3H (0.050
g, 20%), 4H (0.046 g, 21%), 5H-E (0.020 g, 7%), and 5H-Z
(
0.020 g, 7%).
H: 1H NMR (CDCl
11, J ) 6.1 Hz), 3.35 (s, 3 H), 1.97 (s, 3 H), 1.36 (d, 3 H, J )
.1 Hz), 1.25 (d, 3 H, J ) 6.1 Hz); 13C NMR (CDCl
) δ 196.6,
95.6, 165.6, 138.9, 134.3, 128.9, 128.6, 127.0, 82.0, 75.1, 54.0,
3
3
) δ 7.45-7.30 (m, 511), 5.62 (septet,
1
6
1
2
9
3
3J : 1H NMR (CDCl
H, J ) 6.1 Hz), 3.35 (s, 3 H), 2.00 (s, 3 H), 1.38 (d, 3 H, J ) 6.1
Hz), 1.28 (d, 3 H, J ) 6.1 Hz); 13C NMR (CDCl
) δ 195.9, 194.9,
165.9, 139.7, 138.3, 127.4, 125.6, 125.6, 81.6, 75.5, 54.1, 23.2,
) δ 7.62-7.49 (m, 4 H), 5.64 (septet, 1
3
-
1
3.1, 7.2; IR (CDCl
4
) 1697 (vs), 1618 (s) cm ; MS (EI) 274 (M+,
3), 243 (10), 233 (7), 217 (8), 202 (10), 175 (11), 159 (33), 148
3
18 4
(12), 121 (16), 120 (20), 105 (100); HRMS calcd for C16H O
-
1
2
74.1205, found 274.1204.
7.4; IR (CH
10), 300 (9), 270 (4), 255 (7), 227 (13), 173 (100), 145 (34), 111
(28); HRMS calcd for C17 342.1079, found 342.1083.
4J : 1H NMR (CDCl
) δ 7.66-7.24 (m, 4 H), 5.59 (septet, 1
H, J ) 5.0 Hz), 4.01 (s, 3 H), 1.99 (s, 3 H), 1.36 (d, 3 H, J ) 5.0
2 2
Cl ) 1693 (vs), 1610 (s) cm ; MS (EI) 324 (M+,
1
4
H: H NMR (CDCl
septet, 1 H, J ) 6.1 Hz), 3.92(s, 1 H), 1.97 (s, 311), 1.35 (d,
11, J ) 6.1 Hz), 1.32 (d, 311, J ) 6.1 Hz); 13C NMR (CDCl
δ 197.1, 196.0,166.1, 138.7, 133.2, 128.9, 128.3, 127.8, 74.7,
3
) δ 7.30 (m, 311), 7.11 (m, 2 H), 5.58
(
3
17 3 4
H F O
3
)
3
-
1
13
5
2
1
6.9, 23.1, 7.3; IR (CDCl
4
) 1696 (vs), 1621 (s) cm ; MS (EI)
Hz), 1.33 (d, 3 H, J ) 5.0 Hz); C NMR (CDCl
3
) δ 196.1, 195.1,
44 (M+, 100), 202 (41), 163 (8), 129 (6), 119 (16), 118 (52),
166.1, 138.8, 136.9, 128.8, 125.8, 75.0, 56.5, 23.2, 16.9, 7.4; IR
-
1
13 (7); HRMS calcd for C15
H
15
O
3
244.1099, found 244.1107.
(CH
(40), 241 (8), 187 (100), 159 (55), 97 (12), 57 (23); HRMS calcd
for C16 313.1052, found 313.1060.
5J -E: 1H NMR (CDCl
) 87.88-7.62 (m, 4 H), 4.88 (septet,
1 H, J ) 6.1 Hz), 3.62 (s, 3 H), 2.01 (s, 3 H), 1.42 (d, 6 H, J )
2 2
C1 ) 1694 (s), 1622 (m) cm ; MS (CI) 313 (M+, 29), 271
1
5
H-E: H NMR (CDCl
3
) δ 7.71 (m, 211), 7.33 (m, 3 H), 4.84
(septet, 1 H, J ) 6.1 Hz), 3.62 (s, 311), 1.98 (s, 311), 1.41 (d,
16 3 3
H F O
1
3
6
3
11, J ) 6.1 Hz); C NMR (CDCl
3
) δ 170.3, 163.0, 142.9 136.4,
3
1.8, 129.5, 128.9, 128.5, 103.6, 75.2, 60.5, 22.7, 8.8; IR (CDCl
4
)

4
436 Organometallics, Vol. 18, No. 21, 1999
Zora et al.
6
1
1
.1 Hz); 13C NMR (CDCl
3
) δ 169.9, 162.7, 140.9, 137.8, 135.7,
C1
100), 172 (11), 157 (9), 144 (13), 129 (4), 116 (52), 115 (69);
HRMS calcd for C13H O 200.0837, found 200.0838.
12 2
29.0, 125.4, 125.4, 103.7, 75.2, 60.8, 22.7, 8.9; IR (CH
2
2
)
761 (s), 1634 (m), 1613 (m) cm-1; MS (EI) 342 (M+, 54), 300
Rea ction of p-Tr iflu or om eth ylp h en ylca r ben e Com -
p lex 2H w ith 3,4-Dim eth yl-3-cyclobu ten e-1,2-d ion e (1D):
En tr y L of Ta ble 1. General procedure II was followed using
cyclobutenedione 1D (0.110 g, 1.00 mmol) and carbene complex
(46), 270 (8), 227 (21), 173 (100), 126 (3); HRMS calcd for
C
17
H
17
F
3
O
4
342.1079, found 342.1076.
1
5
J -Z: H NMR (CDCl ) δ 7.66-7.47 (m, 4 H), 4.51 (septet,
3
1
6
H, J ) 6.0 Hz), 3.72 (s, 3 H), 1.92 (s, 3 H), 0.86 (d, 6 H, J )
2
H (0.456 g, 1.20 mmol). After chromatographic purification,
.0 Hz).
two fractions were isolated. They were assigned as 3L (0.024
g, 8%) and 4L (0.019 g, 7%).
Rea ction of Ca r ben e Com p lex 2A w ith 3-Meth yl-4-
p h en yl-3-cyclobu ten e-1,2-d ion e (1C): En tr y K of Ta ble
1
1
mmol). After chromatographic purification, two fractions were
isolated. The product in the first fraction was assigned as 2,4-
diinethyl-5-phenyl-4-cyclopentene-1,3-dione (4K) (0.031 g, 15%).
The product in the second fraction was identified as 2-methoxy-
2
2
3
L: 1H NMR (CDCl
H, J ) 9.5 Hz), 3.34 (s, 3 H), 2.11 (s, 6 H); C NMR (CDCl
δ 199.6, 156.3, 137.9, 127.7, 125.6, 125.6, 79.2, 54.2, 9.7; IR
3
) δ 7.59 (d, 2 H, J ) 9.5 Hz), 7.49 (d, 2
13
. General procedure II was followed using cyclobutenedione
C (0.172 g, 1.00 mmol) and carbene complex 2A (0.325 g, 1.30
3
)
-
1
(
CH
2
Cl
2
) 1700 (s) cm ; MS (EI) 298 (M+, 52), 174 (100), 145
(
40), 69 (18), 54 (12); HRMS calcd for C15
13 3 3
H F O
298.0817,
found 298.0823.
L: 1H NMR (CDCl
H, J ) 9.5 Hz), 3.93 (s, 1 H), 2.10 (s, 6 H); C NMR (CDCl
4
3
) δ 7.58 (d, 2 H, J ) 8.6 Hz), 7.25 (d, 2
,4-diinethyl-5-phenyl-4-cyclopentene-1,3-dione (3K) (0.047 g,
1
3
3
)
-
0%).
3
K: 1H NMR (CDCl
3
) δ 7.60-7.40 (m, 5 H), 3.28 (s, 3 H),
13
δ 199.9, 156.4, 136.8, 128.9, 125.8, 125.8, 54.9, 9.6; IR (CH
2
-
1
Cl
97 (14), 189 (15), 186 (44), 173 (18), 158 (44), 89 (11), 54 (22),
53 (14); HRMS calcd for C14 268.0708, found 298.0711.
2
) 1700 (s), 1688 (s) cm ; MS (EI) 268 (M+, 100), 225 (13),
2
1
.22 (s, 3 H), 1.43 (s, 3 H); C NMR (CDCl
3
) δ 203.6, 201.6,
1
52.7, 152.1, 130.4, 129.6, 128.6, 128.3, 76.3, 53.6, 18.9, 10.6;
-1
11 3 2
H F 0
IR (CCl ) 1709 (vs) cm ; MS (EI) 230 (M+, 100), 215 (18), 187
4
(20), 173 (8), 159 (7), 143 (5), 115 (30); HRMS calcd for
14 14 3
C H O
4
230.0943, found 230.0942.
Ack n ow led gm en t. We thank the Petroleum Re-
search Fund, administered by the American Chemical
Society, for financial support of this research.
1
K: H NMR (CDCl
J ) 7.6 Hz), 2.18 (s, 3 H), 1.31 (d, 3 H, J ) 7.6 Hz); C NMR
CDCl ) δ 204.2, 202.6, 153.6, 153.1, 129.9, 129.5, 129.3, 128.5,
4.8, 10.7, 10.4; IR (CCl
3
) δ 7.60-7.40 (m, 5 H), 2.81 (q, 1 H,
13
(
3
-
1
4
4
) 1702 (vs) cm ; MS (EI): 200 (M+,
OM9905198