Annulation selectivity in the coupling of Fischer carbene complexes with o-alkynylbiphenyl and o-alkynylstyrene derivatives

Article abstract of DOI:10.1016/S0040-4020(01)00227-7

The coupling of various Fischer carbene complexes with o-ethynylbiphenyl and an o-alkynylstyrene derivatives has been examined. In coupling reactions with methylcarbene and cyclopropylcarbene complexes, the major products are derived from C-H or C-C activation processes. In coupling reactions with phenylcarbene complexes, the major products are derived from the D?tz reaction.

Full text of DOI:10.1016/S0040-4020(01)00227-7

TETRAHEDRON
Pergamon
Tetrahedron 57 22001) 3859±3868
Annulation selectivity in the coupling of Fischer carbene
complexes with o-alkynylbiphenyl and
o-alkynylstyrene derivativesq
Thaddeus J. Jacksona and James W. Herndonb,p
aDepartment of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742-2021, USA
bDepartment of Chemistry and Biochemistry, New Mexico State University, MSC 3C, Las Cruces, NM 88003, USA
Received 3 January 2001; accepted 22 February 2001
AbstractÐThe coupling of various Fischer carbene complexes with o-ethynylbiphenyl and an o-alkynylstyrene derivatives has been
examined. In coupling reactions with methylcarbene and cyclopropylcarbene complexes, the major products are derived from C±H or
È
C±C activation processes. In coupling reactions with phenylcarbene complexes, the major products are derived from the Dotz reaction.
q 2001 Elsevier Science Ltd. All rights reserved.
1. Introduction
2Scheme 3) and o-alkynylstyrene derivative 17 are
examined. Unlike the conversion of 13 to 15 in Scheme 2,
placement of the central alkene within an aromatic ring is
detrimental to the success of the benzannulation reaction
pathway in these systems.
In recent papers, the coupling of carbene complexes with Z
phenylvinylacetylenes 2e.g. 1, Scheme 1)2 and dienyl-
acetylenes 2e.g. 7)3 was reported. These coupling reactions
afforded benzannulation products 2e.g. 6 and 9). In each
case, the anticipated phenol derivative 25 or 8) was unstable
under the reaction conditions, and ultimately resulted in
either the ketal or benzofuran derivatives, depending upon
the workup conditions. The design of the reaction processes
in Scheme 1 is based on the well-known benzannulation
that occurs in the coupling of alkynes with arylcarbene- or
2. Results
2.1. Synthesis of compounds 16 and 17
Compounds 16 and 17 were synthesized according to the
sequence of reactions depicted in Scheme 4. Compound 16
was prepared from 2-biphenylmethanol 218) via oxidation
to aldehyde 19 followed by Corey±Fuchs alkynylation.7
Styrenyl compound 17 was prepared from o-bromobenalde-
hyde 20 via Sonogashira coupling8 followed by Wittig
reaction.
alkenylcarbene±chromium complexes 210, Scheme 2),
È
4
commonly known as the Dotz reaction. Isolated dienyl-
carbene complexes 2e.g. 13) also lead to cyclization/benz-
annulation products under photochemical conditions.5 A
common feature of all of the reaction processes in Schemes
1 and 2 is the intermediacy of an a,b,g,d-unsaturated
carbene complex 2e.g. 3, 11, and 13), also known as a metal-
lahexatriene.6 Arylcarbene and alkenylcarbene complexes
2.2. Coupling of o-alkynylstyrene derivative 17 and
carbene complexes
È
both participate in the Dotz reaction with similar ef®ciency.
Derivatives of complex 13 where either one or both of the
double bonds of the a,b,g,d-unsaturated system are
contained within an aromatic ring undergo bennzannulation
reactions with similar ef®ciency. In this paper, the
analogous reaction processes involving the coupling of
carbene complexes with o-ethynylbiphenyl derivative 16
The coupling of carbene complex 2 with alkynylstyrene
derivative 17 afforded none of the expected benzannulation
products 26 or 27 2Scheme 5). A complex mixture of ®ve-
membered ring derivatives 22±25 was produced in this
reaction. Similar products were obtained from the coupling
of alkynylstyrene derivative 17 with cyclopropylcarbene
complex 28 using 99:1 dioxane/water as the solvent.
Related cyclopentenone structures have been obtained
from the coupling of simple alkynes with methylcarbene
complex 29 or cyclopropylcarbene complex 28,10 thus the
pendant alkene appears to have no effect on the reaction
processes in Scheme 5. Coupling of alkynylstyrene
q See Ref. 1.
Keywords: carbene complexes; alkynes; cycloaddition; cyclization; C±H
activation; ketenes.
p
Corresponding author. Fax: 11-505-646-2649;
e-mail: jherndon@nmsu.edu
0040±4020/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020201)00227-7

3860
T. J. Jackson, J. W. Herndon / Tetrahedron 57 32001) 3859±3868
OMe
CH3
Cr(CO)5
Cr(CO)4
CH3
OMe
2
3
1
OMe
CH3
OMe
MeO
CH3
CH3
OH
O
(OC)3Cr
O
6
4
5
OMe
CH3
CH3
O
Bu
Bu
Cr(CO)5
OMe
Bu
I2
CH3
OH
2
9
7
8
Scheme 1.
RL
RL
OH
RS
Cr(CO)5
RS
Cr(CO)4
RL-C C-RS
MeO
MeO
MeO
12
10
11
OMe
Cr(CO)5
OMe
OMe
Cr(CO)4
O
OH
hν
13
14
15
Scheme 2.
Bu
Cr(CO)5
OMe
Minimal
CH3
Benzannulation
Products
or
17
16
2
Scheme 3.
derivative 17 with phenylcarbene complex 29 led exclusively
È
to the Dotz benzannulation product 30 2Scheme 6). None of
the products from benzannulation onto the styrenyl system,
complex 2 led to a mixture of oxidized benzannulation
product 33A and cyclopentannulation product 34
2Scheme 7). Phenanthrene 33A is likely derived from air
oxidation of enol ether 35A or ketal 36A. In the initial
separation of the reaction mixture by ¯ash chromatography,
a fraction containing 33A and a compound consistent with
enol ether 35A could be isolated. Attempts to separate 33A
and 35A were not successful. Optimal weight recoveries
were obtained if the reaction mixture was separated by
naphthalenes 31 or 32, were observed in the reaction.
2.3. Coupling of 2-ethynylbiphenyl )16) with carbene
complexes
The reaction of 2-ethynylbiphenyl 216) with carbene

T. J. Jackson, J. W. Herndon / Tetrahedron 57 32001) 3859±3868
3861
CHO
CH2OH
1. CBr4 / PPh3 / Zn
PCC
2. 2 eq. BuLi
16
19
18
20
77%
90%
Bu
Bu
Br
O
H
hexyne / PdCl2 /
Ph3P=CH2
O
CH2
CuI / PPh3 / Et2NH
17
21
H
80%
76%
Scheme 4.
O
O
Bu
Cr(CO)5
OMe
OMe
+
2
OMe
CH3
Bu
Bu
+
21%
dioxane / 100 °C
4%
17
22
23
Hypothetical Benzannulation Products:
O
O
OMe
+
O
O
Bu
7%
Bu
2%
27
26
Bu
CH3
Bu
CH3
MeO
25
24
NOT OBSERVED
Bu
Cr(CO)5
OMe 28
22 - 38%
23 - 8%
25 - 6%
99:1 dioxane / water
100 °C
17
Scheme 5.
preparative TLC. Under these conditions only oxidized
product 33A and cyclopentenone 34 were obtained from
the reaction. Similar products were obtained from coupling
of alkyne 16 with cyclopropylcarbene complex 28; the yield
of cyclopentannulation product 34 was much higher in this
case. An unusual multiple benzannulation product 38 was
obtained from the coupling of phenylcarbene complex 29
and alkyne 16 2Scheme 8). This product is more likely
È
derived from Dotz benzannulation product 37 and not the
alternative benzannulation product 39 based on the more
appropriate location of the oxygens in 37 vs the oxygens
of 39. A trace amount of alternative benzannulation product
33C 22% yield) was also obtained from this reaction.
3. Discussion
3.1. Benzannulation vs cyclopentannulation in the
coupling of methylcarbene complex 2 or cyclopropyl-
carbene complex 28 with alkynes 16 and 17
The results in Schemes 5±8 all show that 2-ethynylbiphenyl
216) and o-alkynylstyrene 17 are very reluctant to undergo
benzannulation reactions with Fischer carbene complexes in
contrast to the systems depicted in Scheme 1. In the reac-
tions of Schemes 5 and 7, C±H or C±C activation processes
are preferred over benzannulation processes. Previous
Scheme 6.

3862
T. J. Jackson, J. W. Herndon / Tetrahedron 57 32001) 3859±3868
OMe
O
O
CH3
OMe
Cr(CO)5
OMe
O
2
CH3
+
22%
26%
dioxane / 100 °C
16
34
33A
O
O
CH3
OMe
Cr(CO)5
O
28
OMe
+
99:1 dioxane / water
100 °C
50%
26%
16
34
33B
R
R
R
O
CH3
CH3
OCH3
OH
O
O
air
35
36
33
33, 35, 36: A - R = CH3; B - R = cyclopropyl; C - R = Ph
Scheme 7.
reports of the cyclopentannulation reactions depicted in
Schemes 5 and 79,10 suggested mechanistic alternatives,
where the C±H activation process occurred at either the
vinylketene or vinylcarbene stages 2Scheme 9). No de®ni-
tive experiment was presented that could delineate which
intermediate was involved in the C±H2C±C) activation
event. Very strong evidence however supports the interme-
diacy of vinylketene complexes in the benzannulation
event.11
event at the vinylcarbene stage would likely result in similar
reaction pathways for the coupling of carbene complexes 2
or 28 with alkynes 16, 17, or 1. Since neither intermediate
40 nor intermediate 3 can directly undergo the benzannula-
tion event, the competition between CO insertion and
C±H2C±C) activation should be similar for these two
intermediates. The vinylketenes derived from these inter-
mediates 241 and 4) however differ greatly in the placement
of aromatic rings and cyclization to the phenols 243 or 5)
will likely occur at different rates. As noted in Ref. 2,
benzannulation is the exclusive reaction pathway for the
coupling of alkyne 1 with carbene complexes 2 and 28.
The observed results in Schemes 5±7 suggest that the
C±H2C±C) activation events occur at the vinylketene
stage. If the C±H2C±C) events occur at the vinylcarbene
stage, the competitive process is C±H2C±C) activation vs
CO insertion 2i.e. conversion of 40 to 42 vs conversion of 40
to 41, Scheme 9). Occurrence of the C±H2C±C) activation
The less facile benzannulation of vinylketene 41 relative to
vinylketene 4 is not consistent with a recent theoretical
12
study of the Dotz reaction. In the energetically most
È
Cr(CO)5
HO
vs
O
29
Ph
OMe
OMe
O
dioxane / 100 °C
16
37
38
52%
OMe
X
Ph
OH
39
Scheme 8.

T. J. Jackson, J. W. Herndon / Tetrahedron 57 32001) 3859±3868
3863
OMe
CH3
OMe
Bu
(OC)3Cr
Bu
Bu
Cr(CO)5
OMe
CH3
CH3
Cr(CO)5
O
17
2
41
40
OMe
Bu
OMe
Cr(CO)5
H
Bu
CH3
OH
Naphthalenes
26 or 27
42
43
OMe
Bu
OMe
O
H
Bu
H
(OC)3Cr
(OC)3Cr
Cyclopentenones
22-25
O
45
44
OMe
CH3
Cr(CO)4
OMe
CH3
Cr(CO)5
OMe
(OC)3Cr
CH3
O
2
3
1
4
X
Exclusive
Benzannulation
No C-H activation
Scheme 9.
reasonable pathway for this reaction, coordination of the
metal to the g,d-double bond of a dienylcarbene inter-
mediate was suggested as an important event. This event
should be more favorable for complex 40 than for complex 3
since coordination to the monosubstituted alkene of 40
would be more favorable than h2-coordination to the
aromatic ring in intermediate 3.13
carbene complex 47. An electronically favorable ligand
isomerization would then afford alternative vinylcarbene
complex intermediate 48. This isomerization is observed
when the A-ring is not aromatic, as in complexes derived
from alkyne 1, and thus the preferred reaction pathway is
isomerization of 47 to 48 followed by CO-insertion to give
vinylketene 51 and electrocyclic ring closure in the coordi-
nation sphere of chromium to afford phenol 52 and ulti-
mately benzofuran 53. When the A-ring is aromatic, as in
intermediates derived from alkynes 16 and 17, the isomer-
ization of 47 to 48 is disfavored since the isomerization step
involves the formation of a partially coordinated aromatic
ring.13 The observed reaction pathway in this case is conver-
sion of initially generated vinylcarbene complex 47 to
vinylketene 50 and electrocyclic ring closure in the coordi-
nation sphere of chromium to afford phenol 37 and ulti-
mately quinone 38. An alternative scenario for alkyne 17
is conversion of 47 to 49 and subsequent benzannulation
onto the vinyl group,12 however, this event does not seem
to be important since the only product of this reaction is also
derived from benzannulation onto the phenyl ring originat-
ing at the carbene complex 2naphthol 30, Scheme 6).
3.2. Competitive benzannulation in the coupling of
phenylcarbene complex 29with alkynes 16 and 17
The reaction of phenylcarbene complex 29 with alkynes 16
or 17 led to predominantly products derived from benz-
annulation onto the phenyl ring originating from the carbene
complex. Coupling of carbene complex 29 with alkyne 1
afforded predominantly benzofuran 53 2Scheme 10),2 which
is derived from benzannulation onto the phenyl ring origi-
nating from the enyne. The different reaction pathways of
alkynes 1 vs alkynes 16 and 17 can be attributed to ligation
preferences in the intermediate vinylcarbene complex inter-
mediates 2e.g. 47±49). The coupling of carbene complex 29
with generic alkyne 46 should initially produce vinyl-

3864
T. J. Jackson, J. W. Herndon / Tetrahedron 57 32001) 3859±3868
OMe
OMe
Ph
R
R
R
Cr(CO)5
Ph
Ph
OMe
Cr(CO)4
A
Cr(CO)4
A
A
29
B
B
B
47
46
48
1: A-cyclohexene, B-phenyl, R = H
16: A-phenyl, B-phenyl, R = H
17: A-phenyl, B-vinyl, R = Bu
Disfavored
Electronically
Disfavored
if A-ring is
Aromatic
OMe
OMe
OMe
Ph
R
R
R
(OC)3Cr
(OC)3Cr
A
O
Cr(CO)4
A
O
A
B
B
B
49
51
Disfavored
if B-ring is
Aromatic
50
OMe
Complexes 47-51
OMe
OH
Derived from 1: B-ring Aromatic
Derived from 16: A- and B-ring Aromatic
Derived from 17: A-ring Aromatic
Ph
OH
37
Ph
O
Ph
O
O
52
Observed Product
Observed Product
For 16 + 29
For 1 + 29
53
38
Scheme 10.
3.3. Formation of dibenzoanthraquinone 38 and not
naphthol 37
These series of events are surprising in that no deliberate
attempt to oxidize naphthol 37 to naphthoquinone 54 has
been attempted. In the ®rst attempt to purify the products of
this reaction by ¯ash chromatography, quinone 38 was
observed as the major product, contaminated with a
compound featuring a methoxy group and no protons in
In the coupling of alkyne 16 with phenylcarbene complex
29, the expected benzannulation product 37 was not
isolated. Only the double benzannulation product 38 was
obtained from the reaction. A possible reason for this
benzannulation is a secondary cyclization process emanat-
ing from naphthoquinone 54, as depicted in Scheme 11.14
È
the bay region. This product is likely the Dotz reaction
product 37, however, it could not be obtained free of anthra-
quinone 38.
OMe
Ph
O
OH
O
37
54
O
O
OH
OH
O
O
56
55
38
Scheme 11.

T. J. Jackson, J. W. Herndon / Tetrahedron 57 32001) 3859±3868
3865
4. Conclusion
sium sulfate, and the solvent was removed on a rotary
evaporator. Final puri®cation was achieved by ¯ash chro-
matography on silica gel using 9:1 hexane/ethyl acetate as
eluent. After solvent removal, a yellow oil identi®ed as
2-biphenylcarboxaldehyde 219) 22.40 g, 90%) was obtained.
1H NMR 2CDCl3): d 9.95 2s, 1H), 8.02 2m, 1H), 7.51 2m,
8H). The spectral data are in agreement with those
previously reported for this compound.16
The coupling of carbene complexes with phenylacetylene
derivatives featuring unsaturated ortho-substituents has
been explored. Benzannulation involving the unsaturated
acetylene system is never more than a minor reaction path-
way in these systems, which is in contrast to the ef®cient
benzannulation reactions previously reported for coupling
of carbene complexes and dienylacetylene derivatives
where the central alkene is not in an aromatic ring. The
reduced benzannulation ef®ciency has been attributed to
poorer ligation ability of an aromatic ring relative to a
simple alkene.
5.1.2. Synthesis of 2-ethynylbiphenyl )16). A mixture of
zinc dust 2220 mg, 3.29 mmol), triphenylphosphine
2860 mg, 3.29 mmol), and carbon tetrabromide 21.09 g,
3.29 mmol) in dichloromethane 2100 mL) was stirred at
room temperature under nitrogen for a 24 h period. To
this solution was added 2-biphenylcarboxaldehyde 219)
2300 mg, 1.65 mmol) and the reaction was allowed to stir
for a 2 h period. Pentane 2350 mL) was added and the
suspension was ®ltered. The solvent was removed from
the ®ltrate using a rotary evaporator; the residue after
evaporation was dissolved in THF 2100 mL), placed under
nitrogen, and cooled to 2788C. n-Butyllithium 22.06 mL of
a 1.6 M hexane solution, 3.30 mmol) was added and the
solution was kept at 2788C for 1 h. The reaction mixture
was then allowed to warm to room temperature and stirred
for 1 h. Water 21 mL) was added and the mixture was
poured into a mixture of water and pentane in a separatory
funnnel and shaken vigorously. The pentane layer was dried
over magnesium sulfate and the solvent was removed on a
rotary evaporator. Final puri®cation was achieved by ¯ash
chromatography on silica gel using 24:1 hexane:ethyl
acetate as eluent. After solvent removal, a colorless oil
identi®ed as 2-ethynylbiphenyl 216) 2230 mg, 77%) was
5. Experimental
5.1. General considerations
Nuclear magnetic resonance 21H and 13C) spectra were
recorded on a Bruker AF200 2200 MHz) or Bruker AF400
2400 MHz) spectrometer. Chemical shifts are reported in
parts per million 2d) down®eld from an internal tetramethyl-
silane reference. Coupling constants 2J values) are reported
in hertz 2Hz), and spin multiplicities are indicated by the
following symbols: s 2singlet), d 2doublet), t 2triplet), q
2quartet), m 2multiplet). Infrared spectra were recorded on
a Nicolet 5DXC FT-IR spectrometer. Band positions are
reported in reciprocal centimeters 2cm21). Band intensities
are reported relative to the most intense band and are listed
as: br 2broad), vs 2very strong), s 2strong), m 2medium), w
2weak). Only diagnostic bands occurring outside of the
region 2800±3100 cm21 are reported. Mass spectra 2MS)
were obtained on a VG 7070E spectrometer using electron
impact 2EI) or chemical ionization 2CI) or on a Hewlett-
Packard GC-Mass Spec 5970B with Mass Selection Detec-
tor; m/e values are reported, followed by the relative
intensity in parentheses. Flash column chromatography
was performed using thick-walled glass columns and
`¯ash grade' silica 2Bodmann 230±400 mesh). Routine
thin layer chromatography 2TLC) was performed by using
precoated 250 mm mm silica gel plates purchased from
Whatman. Preparative thin layer chromatography 2prep
TLC) was performed by using precoated 1000 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 reagents
and reactants were obtained in reagent grade and used with-
out puri®cation. All reaction solvents were distilled for
purity. Diethyl ether, THF and dioxane were distilled
from sodium-benzophenone ketyl, dichloromethane from
calcium hydride prior to use. All reactions were performed
in an inert atmosphere created by a slight positive pressure
2ca. 0.1 psi) of nitrogen. Carbene complexes were prepared
according to literature procedures.15
1
obtained. H NMR 2CDCl3): d 7.67±7.59 2m, 3H), 7.50±
7.32 2m, 6H), 3.05 2s, 1H); 13C NMR 2CDCl3): d 144.3,
140.3, 133.9, 129.6, 129.3, 129.0, 128.0, 127.6, 127.1,
120.7, 83.0, 80.1; IR 2CCl4): 3313 2s), 2106 2w) cm21
MS 2EI): 178 2M, 100), 151 217); HRMS: calcd for
C14H10Ð178.07825, found 178.07728.
;
5.1.3. Synthesis of butynylstyrene 17. A mixture of
methyltriphenylphosphonium iodide 26.84 g, 17.0 mmol),
aldehyde 218 22.10 g, 11.0 mmol), and sodium hydroxide
20.68 g, 17.0 mmol) in THF 2150 mL) and water 21 mL)
was heated to re¯ux for a 24 h period. The solution was
®ltered and the solvent was removed on a rotary evaporator.
Final puri®cation was achieved by ¯ash chromatography on
silica gel using pure hexane as eluent. After solvent
removal, a colorless oil identi®ed as alkyne 17 21.54 g,
1
76%) was obtained. H NMR 2CDCl3): d 7.56 2d, 1H,
Jˆ8.0 Hz), 7.39 2d, 1H, Jˆ8.0 Hz), 7.20 2m, 3H), 5.76 2d,
1H, Jˆ17.6 Hz), 5.31 2d, 1H, Jˆ11.0 Hz), 2.46 2t, 2H,
Jˆ6.9 Hz) 1.54 2m, 4H), 0.95 2t, 3H, Jˆ7.1 Hz); 13C
NMR 2CDCl3): d 138.9, 135.3, 132.5, 127.6, 127.4, 124.5,
115.0, 95.3, 78.9, 30.9, 22.0, 19.3, 13.6; IR 2CCl4): 2215 2w)
cm21; MS 2EI): 184 2M, 3), 154 2100), 141 249)128 224),
115 239); HRMS: calcd for C14H16Ð181.12520, found
181.12586.
5.1.1. Synthesis of 2-biphenylcarboxaldehyde )19). To a
suspension of Celite 26.25 g) and pyridinium chlorochro-
mate 26.25 g, 29.0 mmol) in dichloromethane 290 mL) was
added dropwise a solution of 2-biphenylmethanol 22.68 g,
15.0 mmol) in dichloromethane 220 mL). The mixture was
allowed to stir for a 12 h period and diluted with ether
250 mL). The mixture was then ®ltered, dried over magne-
5.1.4. General procedure for the coupling of alkynes with
carbene complexes. To a two-neck round bottom ¯ask
equipped with a re¯ux condenser, stirrer, and a septum
under nitrogen was added dioxane 210 mL). The dioxane
was brought to a gentle re¯ux. To this re¯uxing dioxane,

3866
T. J. Jackson, J. W. Herndon / Tetrahedron 57 32001) 3859±3868
with the aid of a syringe pump was added carbene complex
21.0 equiv.) and enyne 21.2 equiv.) in dioxane 210 mL)
dropwise over a 2 h period. After the addition was complete,
the mixture was allowed to re¯ux for a 24 h period. The
reaction mixture was then allowed to cool to room tempera-
ture and then concentrated in vacuo. Ethyl acetate 250 mL)
was added and the green chromium residue was ®ltered over
a bed of Celite. The solvent was removed on a rotary
evaporator. Final puri®cation was achieved by either ¯ash
chromatography on silica gel or prep TLC on silica gel. In
all reactions involving cyclopropylcarbene complex 28, the
reaction solvent was 99:1 dioxane/water.
2M, 100), 255 220), 227 233), 216 258), 215 260); HRMS:
calcd for C18H22O2Ð270.16199, found 270.16267.
Cyclopentenone 23. 1H NMR 2CDCl3): d 7.44 2m, 1H), 7.19
2m, 2H), 7.00 2m, 2H), 5.59 2dd, 1H, Jˆ17.2, 1.4 Hz), 5.45
2s, 1H), 5.29 2dd, 1H, Jˆ11.0, 1.4 Hz), 4.17 2d, 1H,
Jˆ7.4 Hz) 3.86 2s, 3H), 3.09 2q, 1H, Jˆ7.4 Hz), 2.64 2m,
1H), 1.26±0.83 2m, 5H), 0.60 2br t, 3H, Jˆ6.9 Hz); 13C
NMR 2CDCl3): d 205.3, 192.9, 138.9, 134.9, 129.8, 128.2,
127.5, 127.2, 126.3, 116.9, 104.1, 58.6, 44.8, 29.6, 29.2,
29.0, 22.4, 13.5; IR 2CCl4): 1705 2s), 1599 2vs) cm21
;
Mass spec 2EI): 270 2M, 100), 255 219), 227 228), 213
255); HRMS: calcd for C18H22O2Ð270.16199, found
270.16169.
5.1.5. Coupling of methylcarbene complex 2 with
butynylstyrene 17. The general procedure was followed
using carbene complex 2 244 mg, 0.14 mmol) and enyne
17 239 mg, 0.21 mmol). After puri®cation on prep TLC
using 9:1 hexane/ethyl acetate followed by 5:1 ethyl acetate
as the eluent, ®ve fractions were isolated. The product in the
®rst fraction was the starting enyne 17. The product in
the second fraction 23 mg, 7% yield) was identi®ed as
cyclopentenone 24. The product in the third fraction
21 mg, 2% yield) was identi®ed as cyclopentenone 25.
The product in the fourth fraction 210 mg, 21% yield) was
identi®ed as cyclopentenone 22. The product in the ®fth
fraction 22 mg, 4% yield) was identi®ed as cyclopentenone
23.
5.1.6. Coupling of cyclopropylcarbene complex 28 with
butynylstyrene 17. The general procedure was followed
using carbene complex 28 236 mg, 0.13 mmol) and enyne
17 228 mg, 0.15 mmol). After puri®cation on prep TLC
using 9:1 hexane/ethyl acetate followed by 5:1 ethyl acetate
as the eluent, four fractions were isolated. The product in the
®rst fraction was the starting enyne 17. The product in the
second fraction 22 mg, 6% yield) was identi®ed as cyclo-
pentenone 25. The product in the third fraction 213 mg, 38%
yield) was identi®ed as cyclopentenone 22. The product in
the fourth fraction 23 mg, 8% yield) was identi®ed as cyclo-
pentenone 23. The spectral data were identical to those
reported in the previous experiment.
1
Cyclopentenone 24: H NMR 2CDCl3): d 7.64 2dd, 1H,
Jˆ9.1, 2.5 Hz), 7.33 2m, 2H), 7.07 2dd, 1H, Jˆ9.0,
2.6 Hz), 6.57 2dd, 1H, Jˆ17.5, 11.0 Hz), 5.72 2d, 1H,
Jˆ17.5 Hz), 5.25 2d, 1H, Jˆ11.0 Hz), 2.74 2m, 2H), 2.52
2t, 2H, Jˆ4.2 Hz), 2.04 2t, 2H, Jˆ7.3 Hz), 1.18 2m, 4H),
0.71 2t, 3H, Jˆ7.1 Hz); 13C NMR 2CDCl3): d 209.5,
161.5, 156.1, 134.3, 134.2, 128.7, 127.8, 127.0, 126.1,
125.8, 115.8, 34.7, 32.2, 29.8, 23.5, 22.6, 13.7; IR 2CCl4):
1706 2s) cm21; MS 2EI): 240 2M, 18), 213 214), 198 215),
183 256), 141 2100); HRMS: calcd for C17H20OÐ
240.15141, found 240.15147.
5.1.7. Coupling of phenylcarbene complex 29with
butynylstyrene 17. The general procedure was followed
using carbene complex 29 247 mg, 0.15 mmol) and enyne
17 233 mg, 0.18 mmol). After puri®cation using ¯ash chro-
matography and 9:1 hexane/ethyl acetate as eluent, naphthol
1
30 228 mg, 57% yield) was isolated. H NMR 2CDCl3): d
8.21 2d, 1H, Jˆ8.1 Hz), 8.07 2d, 1H, Jˆ8.1 Hz), 7.79 2d, 1H,
Jˆ8.1 Hz), 7.47 2m, 4H), 7.28 2d, 1H, Jˆ7.1 Hz), 6.41 2dd,
1H, Jˆ17.4, 11.0 Hz), 5.73 2d, 1H, Jˆ17.5 Hz), 5.13 2d, 1H,
Jˆ11.0 Hz), 4.87 2s, 1H), 3.92 2s, 3H), 2.59 2dt, 1H, Jˆ14.4,
6.5 Hz), 2.33 2dt, 1H, Jˆ14.4, 6.5 Hz), 1.35 2m, 2H), 1.19
2quintet, 2H, Jˆ6.5 Hz), 0.67 2t, 3H, Jˆ6.5 Hz); 13C NMR
2CDCl3): d 147.3, 144.6, 137.8, 134.2, 133.3, 131.9, 130.6,
129.0, 128.4, 128.3, 126.4, 125.7, 124.8, 123.5, 122.7,
121.8, 120.7, 115.8, 62.2, 32.2, 27.5, 22.8, 13.5; IR
2CCl4): 3550 2m), 1594 2m) cm21; Mass spec 2EI): 332
2M, 100), 317 216), 275 222), 261 267), 260 246), 259
266); HRMS: calcd for C23H24O2Ð332.17764, found
332.17768.
Cyclopentenone 25. 1H NMR 2CDCl3): d 7.62 2d, 1H,
Jˆ8.0 Hz), 7.25 2m, 2H), 7.01 2m, 1H), 6.49 2m, 1H),
5.69 22 d's 1H, Jˆ17.0 Hz), 5.19 and 5.18 22 d's, 1H,
Jˆ11.0 Hz), 4.61 2m, 1H), 3.48 2s, 3H), 2.85 2dd, 1H,
Jˆ16.7, 5.0 Hz), 2.70±2.10 2m, 3H), 1.35 2m, 4H), 0.81
2t, 3H, Jˆ6.9 Hz) 2this compound appears to be a mixture
of diastereomeric rotamers based on the appearance of the
alkene Hs); 13C NMR 2CDCl3): d 200.1, 135.1, 134.9,
131.7, 130.5, 129.8, 128.8, 127.6, 125.7, 115.6, 104.9,
57.3, 41.2, 29.7, 29.4, 28.6, 22.6, 13.7; IR 2CCl4): 1706
2s) cm21; Mass spec 2EI): 270 2M, 18), 242 213), 240 220),
238 222), 212 273), 181 264), 156 295), 142 2100); HRMS:
calcd for C18H22O2Ð270.16199, found 270.16224.
5.1.8. Coupling of methylcarbene complex 2 with 2-
ethynylbiphenyl )16). The general procedure was followed
using carbene complex 2 248 mg, 0.19 mmol) and 2-
ethynylbiphenyl 216) 238 mg, 0.21 mmol). After puri®ca-
tion on prep TLC using 9:1 hexane/ethyl acetate followed
by 5:1 ethyl acetate as the eluent, two fractions were
isolated. The product in the ®rst fraction 211.5 mg, 22%
yield) was identi®ed the as the oxidized phenanthrene deri-
vative 33A. The product in the second fraction 213.2 mg,
26% yield) was identi®ed as cyclopentenone 34.
1
Cyclopentenone 22. H NMR 2CDCl3): d 7.45 2dd, 1H,
Jˆ9.1, 2.6 Hz), 7.20 2m, 2H), 7.00 2m, 1H), 6.92 2dd, 1H,
Jˆ17.0, 11.0 Hz), 5.62 2dd, 1H, Jˆ17.0, 1.4 Hz), 5.38 2s,
1H), 5.30 2dd, 1H, Jˆ11.0, 1.4 Hz), 3.89 2s, 3H), 3.63 2d,
1H, Jˆ3.1 Hz), 2.89 2m, 1H), 1.80 2m, 1H), 1.22 2m, 5H),
0.83 2br t, 3H, Jˆ6.9 Hz); 13C NMR 2CDCl3): d 204.6,
191.0, 144.9, 134.9, 131.2, 128.1, 128.0, 127.1, 126.9,
117.1, 103.5, 58.9, 55.5, 49.9, 31.3, 28.4, 22.6, 13.8; IR
2CCl4): 1705 2s), 1599 2vs) cm21; Mass spec 2EI): 270
1
Phenanthrene 33. H NMR 2CDCl3): d 8.85 2d, 1H, Jˆ
7.6 Hz), 8.75 2d, 1H, Jˆ7.6 Hz), 8.58 2d, 1H, Jˆ7.6 Hz),
8.41 2d, 1H, Jˆ7.6 Hz), 7.91 2t, 1H, Jˆ7.6 Hz), 7.65 2m,

T. J. Jackson, J. W. Herndon / Tetrahedron 57 32001) 3859±3868
3867
3H), 3.34 2s, 3H), 1.73 2s, 3H); 13C NMR 2CDCl3): d 217.0,
132.5, 129.1,127.8, 125.8, 125.7, 124.0, 123.8, 122.9, 111.8,
109.6, 55.3, 23.1; IR 2CCl4): 1703 2s) cm21; MS 2EI): 278
2M, 100), 263 211), 248 210), 247 213), 221 212), 204 235);
HRMS: calcd for C18H14O3Ð278.09430, found 278.09440.
are in agreement with those previously reported for this
compound.17
Phenanthrene 33C. 1H NMR 2CDCl3): d 8.83 2d, 1H,
Jˆ7.6 Hz), 8.70 2d, 1H, Jˆ7.6 Hz), 8.59 2d, 1H,
Jˆ7.6 Hz), 8.38 2d, 1H, Jˆ7.6 Hz), 7.80±7.30 2m, 9H),
3.39 2s, 3H); MS 2EI): 340 2M, 30), 311 223), 310 220),
281 223), 204 267), 176 2100); HRMS: calcd for
C23H16O3Ð340.10995, found 304.10953.
When the ®nal puri®cation was conducted using ¯ash chro-
matography, the following compound, contaminated with
33A, could also be isolated. This compound is consistent
with the enol ether structure 36A: 1H NMR 2CDCl3): d 8.70
2d, 1H, Jˆ7.6 Hz), 8.66 2d, 1H, Jˆ7.6 Hz), 8.12 2d, 1H,
Jˆ7.6 Hz), 7.99 2d, 1H, Jˆ7.6 Hz), 7.50 2m, 4H), 5.30 2br
s, 1H), 3.45 2s, 3H), 1.72 2s, 3H).
Acknowledgements
We thank the Petroleum Research Fund, Administered by
the American Chemical Society, for ®nancial support of this
research. We thank the University of Maryland for a
fellowship to Thaddeus Jackson.
1
Cyclopentenone 34. H NMR 2CDCl3): d 7.42±7.25 2m,
8H), 7.10 2d, 1H, Jˆ7.3 Hz), 5.38 2s, 1H), 3.88 2dd, 1H,
Jˆ6.4, 2.3 Hz). 3.85 2s, 3H), 2.91 2dd, 1H, Jˆ18.0,
6.4 Hz), 2.58 2dd, 1H, Jˆ18.0, 2.3 Hz); 13C NMR
2CDCl3): d 206.0, 190.1, 142.9, 141.2, 137.9, 130.2,
129.8, 128.1, 127.1, 126.7, 126.5, 104.3, 58.7, 48.0, 39.3;
IR 2CCl4): 1705 2s), 1603 2s) cm21; MS 2EI): 264 2M, 100),
263 223), 205 220), 203 223), 179 226), 177 230), 165 264);
HRMS: calcd for C18H16O2Ð264.11502, found 264.11592.
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È
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3868
T. J. Jackson, J. W. Herndon / Tetrahedron 57 32001) 3859±3868
È
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