Role of imino group in photochemical reactions of Fischer carbene complexes

Article abstract of DOI:10.1016/j.jorganchem.2005.11.025

The photochemical cycloaddition of Fischer iminecarbene complexes bearing two kinds of substituent, imine and alkoxy or amino, has been explored with alkenes and alkynes. It was found that annulated product without CO insertion is formed.

Full text of DOI:10.1016/j.jorganchem.2005.11.025

Journal of Organometallic Chemistry 691 (2006) 1075–1080
www.elsevier.com/locate/jorganchem
Note
Role of imino group in photochemical reactions
of Fischer carbene complexes
*
´
´
´
Pedro J. Campos, Mıriam Caro, Susana Lopez-Sola, Diego Sampedro, Miguel A. Rodrıguez
Departamento de Quı´mica, Universidad de La Rioja, Grupo de Sı´ntesis Quı´mica de La Rioja, Unidad Asociada al C.S.I.C.; Madre de Dios,
51, E-26006 Logron˜o, Spain
Received 29 September 2005; received in revised form 24 October 2005; accepted 9 November 2005
Available online 20 December 2005
Abstract
The photochemical cycloaddition of Fischer iminecarbene complexes bearing two kinds of substituent, imine and alkoxy or amino,
has been explored with alkenes and alkynes. It was found that annulated product without CO insertion is formed.
Ó 2005 Elsevier B.V. All rights reserved.
Keywords: Fischer iminecarbene; Photochemistry; Alkene; Alkyne
1. Introduction
bene complexes in the presence of alkenes, alkynes (Scheme
2) and heteroatom-containing double bonds [9], where the
CO moiety is not inserted into reaction products. This find-
ing prompted us to explore the photochemical behaviour of
carbene complexes bearing both kind of substituent (i.e.,
imine and alkoxy or amino). In this paper, we present
our results from related investigations.
Group VI carbene complexes have a rich photochemis-
try [1]. Photoinduced cycloaddition reactions with unsatu-
rated compounds have been used to generate a large
number of products. For example, irradiation of chromium
alkoxy- [2] or aminocarbenes [3] in the presence of a wide
range of acyclic and cyclic imines allows the preparation
of b-lactams. In a similar way, chromium alkoxycarbenes
lead to the formation of b-lactones with aldehydes [4] or
diazetidinones with azoarenes [5]. Regarding the carbon–
carbon double bond, the photoreaction of alkoxy- [6] or
aminocarbene [7] complexes with alkenes and dienes
produces cyclobutanones (Scheme 1), while Z-dienyl-
2. Results and discussion
Initially, we assessed the influence of the alkoxy group
on the carbenic carbon. The pentacarbonyl[diphenylmeth-
ylene-amino]ethoxy-methylene]chromium(0) complex (1)
was prepared according to the literature procedure [10].
We investigated the photoinduced reaction of 1 in the pres-
ence of unsaturated compounds (Scheme 3) [11]. The reac-
tion with methyl vinyl ketone or ethyl acrylate led to the
cyclopentannulated product 2 or 3, respectively, without
CO insertion. Irradiation of 1 in the presence of alkynes
also gave the five-membered ring compounds 4 or 5. These
results indicate that imino group fixes the structure of the
final product.
alkoxycarbene complexes are useful reagents for
a
photochemical variant of the Do¨tz benzannulation [8].
Interestingly, all of these photoinduced reactions undergo
a CO insertion procedure, which is consistent with the
prior formation of a short-lived metallacyclopropanone–
metal–ketene complex [1].
In contrast to these results, we previously described the
light-induced cyclopentannulation reactions of iminecar-
In order to further explore the photoreactivity of imine-
carbenes bearing an alkoxy group, we carried out the syn-
thesis of some of these complexes with a methoxy group
on the iminic carbenic carbon (carbenes 6–9, Scheme 4).
*
Corresponding author. Tel.: +34 941 299651; fax: +34 941 299621.
E-mail address: miguelangel.rodriguez@dq.unirioja.es (M.A. Rodrı-
´
guez).
0022-328X/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.11.025

1076
P.J. Campos et al. / Journal of Organometallic Chemistry 691 (2006) 1075–1080
1
OMe
Ph
OMe
Ph
R
N
Z
t-Bu
EtO
hν
N
R
hexane / hν
(CO) Cr
5
Z
(CO)5Cr
1
R
R = t-Bu
H
O
H
OEt
R =
Et
6
Z = OR, NR
2
10 48%
t-Bu
Ph
7
8
9
Scheme 1.
p-Tol
R3
R2
R4
R1
N
N
R1
hexane / hν
hexane / hν
(CO)5Cr
R2
R3
COMe
R4
hexane / hν
R5 R6
H
Ph
N
N
R
H
Ph
R
R1
OMe
COMe
H
COMe
R2
R3
R5
N
R4
R1
N
R3
R2
R =
11 33%
12a 28%
13 43%
14a 17%
-
Et
R6
12b 17%
-
t-Bu
Ph
Scheme 2.
14b 41%
p-Tol
Scheme 4.
The synthesis of these targets was achieved by heating pen-
tacarbonyl[methoxy(phenyl)carbene]chromium(0) in the
presence of the appropriate nitrile. The reaction involves
insertion of a carbon–nitrogen triple bond into the car-
bene–metal bond [12].
The configurational assignment of compounds 10–14 was
made on the basis of difference NOESY experiments and
comparison of their spectral data with those of similar
compounds whose X-ray structures are available [9].
We subsequently modified the structure of the imine-
carbene complex by including an amino instead of an alk-
oxy group on the carbenic carbon. In this respect, we
prepared carbene 15 from dimethylcyanamide [14] and
investigated its photochemical behaviour in the presence
of some unsaturated compounds (Scheme 5). Irradiation
of carbene 15 in the presence of methyl vinyl ketone or
ethyl acrylate led to the formation of the corresponding
pyrrole derivatives 16 or 17, respectively. Aminopyrroles
16 and 17 were obtained with a large amount of poly-
meric material and it was observed that they decompose
The corresponding cyclopentannulation reaction prod-
ucts were also obtained by irradiation of complexes 6–9
in the presence of unsaturated systems (Scheme 4) [13].
The photoreaction involving 7 and ethyl ethynyl ether gave
2H-pyrrole 10, while the reaction with alkenes led to a
mixture of 1-pyrrolines and the corresponding pyrrole –
resulting from spontaneous loss of methanol due to aroma-
tization. The pyrrolines were detected by 1H NMR
spectroscopy in all cases but they proved to be too unstable
to be purified – with the exception of 12b and 14b. In these
two cases, the pyrroline could be isolated and character-
ized. However, treatment of solutions of pyrrolines 12b
and 14b with one equivalent of HBF4 led to the quantita-
tive formation of the corresponding pyrrole in a few hours.
H
OMe
Ph
N
Me2N
Ph
R1
N
hexane / hν
(CO)5Cr
OEt
Ph
Ph
NMe2
H
15
R1
N
hexane / hν
1
N
(CO) Cr
R
5
OEt
R1 =
1
Ph
Ph
COMe 16 15%
CO2Et 17 10%
hexane / hν
1
R
H
OEt
1
R =
COMe
CO Et
2
3
60%
55%
hexane / hν
2
2
2
R
R
H
OMe
Ph
N
O
Ph
Ph
N
EtO
2
R =
H
CO Me
4
5
93%
53%
EtO
2
Et
2
2
R
R
18 40%
Scheme 3.
Scheme 5.

P.J. Campos et al. / Journal of Organometallic Chemistry 691 (2006) 1075–1080
1077
during the work up procedure (column chromatography,
hexane/ether), which explains the low yields. Moreover,
irradiation of carbene 15 in the presence of ethyl ethynyl
ether gave pyrrolone 18 in 40% yield, with the enamine
moiety being hydrolyzed during the course of the reac-
tion. This kind of compound has previously been synthe-
sized [15], was found to show a range of biological
activity [16] and has been used for the synthesis of differ-
ent natural products [17].
In an attempt to confirm the photochemical nature of
these transformations, we carried out the same processes
in the dark at room temperature for 3 h, but no reaction
took place. However, when compound 8 was heated at
80 °C in the dark for 36 h in the presence of methyl vinyl
ketone, the formation of pyrrole 13 (40% yield) was
detected. When complex 15 was heated in the presence
of the unsaturated systems shown in Scheme 5 only car-
bene decomposition products and polymeric material
were found.
The iminecarbenes 6 and 9 were prepared as follows.
The alkoxycarbene complex (3 mmol) was dissolved in
20 mL of deoxygenated toluene and the corresponding
nitrile (15 mmol) was added. The mixture was stirred at
80 °C until the carbene had been consumed (1–2 days,
TLC, hexane/ether 2:1). The solvent was removed under
vacuum. Purification of the residue by column chromatog-
raphy (silica gel, hexane or hexane/ether 9:1) and recrystal-
lization (hexane/ether) gave carbenes 6 and 9 as yellow and
orange solids, respectively.
4.3. Pentacarbonyl{[(methoxyphenylmethylene)amino]-
ethylmethylene}chromium(0) (6)
1
Yellow solid. Yield: 0.23 g, 21%. H NMR: d 1.02 (t,
J = 7 Hz, 3H, CH2CH3), 3.30 (q, J = 4 Hz, 2H, CH2CH3),
3.89 (s, 3H, OCH3), 7.49–7.62 (m, 5H, H arom.). 13C
NMR: d 11.3 (CH2CH3), 47.0 (CH2CH3), 55.6 (OCH3),
126.0, 127.5, 129.2, 132.2, 139.0, 217.5 (CO-cis), 223.8
(CO-trans), 254.2 (C@Cr). ES-MS (–): m/z 366 (MÀ1),
338 (MÀCOÀ1), 310 (MÀ2COÀ1). IR (CH2Cl2): m 1303
(w), 1601 (w), 1809 (m), 1922 (s), 1968 (sh), 2049 (m)
3. Conclusions
A thorough investigation into the photochemical behav-
iour of carbene complexes bearing two kinds of substituent
(imine and alkoxy or amino) with unsaturated systems has
been performed. It was found that the presence of the
imino group determines whether the annulated product
without CO insertion is formed. These results suggest that
the imino group inhibits the formation of transient metal-
ketene complexes and complete loss of one CO molecule
should occur after irradiation.
cmÀ1
.
UV (hexane):
k
226 nm (e ꢀ 30910), 249 nm
(e ꢀ 36768), 368 nm (e ꢀ 5607). Mp: 48–50 °C. Anal. Calc.
for C16H13NO6Cr: C, 52.33; H, 3.57; N, 3.81. Found: C,
52.40; H, 3.61; N, 3.75%.
4.4. Pentacarbonyl{[(methoxyphenylmethylene)amino]-
para-tolylmethylene}chromium(0) (9)
1
Orange solid. Yield: 0.51 g, 40%. H NMR: d 2.40 (s,
3H, CH3-C6H4), 4.00 (s, 3H, OCH3), 7.25 (d, J = 8 Hz,
2H, H arom.), 7.47–7.62 (m, 7H, H arom.). 13C NMR: d
21.6 (CH3-C6H4), 55.7 (OCH3), 126.6, 127.4, 128.4, 129.2,
129.5, 132.2, 138.1, 142.1, 142.7, 217.8 (CO-cis), 224.1
(CO-trans), 259.8 (C@Cr). ES-MS (À): m/z 428 (MÀ1),
400 (MÀCOÀ1), 372 (MÀ2COÀ1). IR (CH2Cl2): m 1264
(s), 1599 (w), 1796 (w), 1927 (s), 1972 (sh), 2054 (m)
cmÀ1. UV (hexane): k 208 nm (e ꢀ 192346), 255 nm
(e ꢀ 45408), 430 nm (e ꢀ 5177). Mp: 106–108 °C. Anal.
Calc. for C21H15NO6Cr: C, 58.75; H, 3.52; N, 3.26. Found:
C, 56.67; H, 3.47; N, 3.11%.
4. Experimental
4.1. General comments
All solvents were purified and dried by standard pro-
cedures and freshly distilled under dry Ar prior to use.
1H and 13C spectra were recorded on a Bruker ARX-
300 spectrometer in CDCl3 with TMS as internal stan-
dard. Electrospray mass spectra were obtained on an
HP 5989 B apparatus with an HP 59987 A interface in
either negative-ion mode or positive-ion mode. GC/MS
spectra were recorded on an HP G1800A apparatus.
IR spectra were obtained on a Perkin–Elmer 1000 spec-
trophotometer in CH2Cl2. UV spectra were recorded on
an HP 8451A spectrophotometer. Elemental analyses
were performed using a Model 1110 CE instrument.
4.5. General procedure for irradiation
The carbene complex (0.25 mmol) was dissolved in
50 mL of deoxygenated hexane. Ten equivalents of the
unsaturated compound were added and the mixture was
irradiated at room temperature under an Ar atmosphere
through Pyrex glass with a 125 W (2–5) or 400 W (10–14,
16–18) medium-pressure mercury lamp. Irradiation was
continued until the iminecarbene had been consumed (1–
2 h, TLC, hexane/ether 3:1). The solvent was removed
using a rotary evaporator and the crude product was fil-
tered through Celite to remove chromium residues. The
products were separated by column chromatography (silica
gel, hexane/ethyl acetate or hexane/ether).
Melting points were obtained on a Buchi SMP-20 appa-
¨
ratus and are uncorrected. Reagents were of commercial
grades.
4.2. General procedure for the preparation of iminecarbene
complexes 1, 6–9, and 15
The formation of compounds 1 [10], 7–8 [12], and 15 [14]
has been reported previously.

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P.J. Campos et al. / Journal of Organometallic Chemistry 691 (2006) 1075–1080
4.6. 4-Acetyl-2-ethoxy-5,5-diphenyl-1-pyrroline (2)
(t, J = 7.1 Hz, 3H, OCH2CH3), 2.31 (q, J = 7.5 Hz, 2H,
C@C–CH2), 2.40 (q, J = 7.6 Hz, 2H, C@C–CH2), 4.37 (q,
J = 7.1 Hz, 2H, OCH2), 7.20 (m, 10H, arom).13C NMR:
d 13.6 (CH3), 13.7 (CH3), 14.7 (CH3), 17.7 (CH2), 21.2
(CH2), 63.7 (OCH2), 83.9 (CPh2), 126.9, 128.1, 128.2,
132.3, 142.5, 165.9.6, 172.4 (C@N). GC–MS: m/z 319 (M,
17), 290 (MÀEt, 100), 262 (6), 180 (6), 165 (8), 129 (6),
105 (7), 77 (19), 29 (4). IR (CH2Cl2): m 1584 (m), 1658
(w) cmÀ1. Anal. Calc. for C22H25NO: C, 82.72; H, 7.89;
N, 4.38. Found: C, 82.61; H, 7.79; N, 4.27%.
Yellow oil. Yield: 46 mg, 60%. 1H NMR: d 1.30 (t,
J = 7.1 Hz, 3H, CH3), 1.48 (s, 3H, COCH3), 2.60 (dd,
J = 16.7 Hz, J = 8.6 Hz, 1H, H3a), 2.91 (dd, J = 16.7 Hz,
J = 3.9 Hz, 1H, H3b), 4.07 (dd, J = 8.6 Hz, J = 3.9 Hz,
1H, H4), 4.26–4.42 (m, 2H, OCH2), 7.06–7.20 (m, 6H,
arom), 7.28 (t, J = 7.9 Hz, 2H, arom), 7.55 (d,
J = 7.5 Hz, 2H, arom). 13C NMR: d 14.6 (CH3), 29.6
(CH3), 35.0 (N@C–CH2), 60.1 (CHCO), 64.8 (OCH2),
81.2 (CPh2), 127.0, 127.1, 127.3, 127.7, 128.1, 128.3,
144.1, 146.6, 170.9 (C@N), 208.2 (C@O). GC–MS: m/z
307 (M, 10), 278 (MÀEt, 31), 264 (8), 208 (52), 182 (100),
165 (42), 126 (83), 98 (42), 77 (50), 43 (25). IR (CH2Cl2):
m 1651 (s), 1708 (s) cmÀ1. Anal. Calc. for C20H21NO2: C,
78.15; H, 6.89; N, 4.56. Found: C, 78.05; H, 6.80; N, 4.44%.
4.10. 2-tert-Butyl-3-ethoxy-5-methoxy-5-phenyl-2H-pyrrole
(10)
1
Yellow oil. Yield: 33 mg, 48%. H NMR: d 1.36 [s, 9H,
C–(CH3)3], 1.36 (m, 3H, OCH2CH3), 3.27 (s, 3H, OCH3),
3.89 (m, 2H, OCH2CH3), 5.79 (s, 1H, CH), 7.23–7.34 (m,
3H, H arom.), 7.48–7.51 (m, 2H, H arom.). 13C NMR: d
14.6 (OCH2CH3), 27.6 [C–(CH3)3], 29.8 [C–(CH3)3], 51.5
(OCH3), 66.6 (OCH2CH3), 115.7 (CH), 126.4, 127.9,
128.3, 129.0, 139.9 (C–OEt), 155.8 (C@N). ES-MS (+):
m/z 274 (M+1). GC–MS: m/z 273 (M, 40), 244 (37),
216 (23), 188 (20), 161 (100), 126 (22), 115 (17), 105
(20), 102 (29), 77 (29), 69 (27), 28 (39). IR (CH2Cl2): m
1441 (m), 1461 (m), 1577 (m) cmÀ1. Anal. Calc. for
C19H19NO2: C, 74.69; H, 8.48; N, 5.12. Found: C,
74.58; H, 8.36; N, 4.98%.
4.7. 2-Ethoxy-4-ethoxycarbonyl-5,5-diphenyl-1-pyrroline
(3)
Yellow oil. Yield: 47 mg, 55%. 1H NMR: d 0.90 (t,
J = 7.1 Hz, 3H, CH3), 1.39 (t, J = 7.1 Hz, 3H, CH3), 2.73
(dd, J = 16.8 Hz, J = 9.5 Hz, 1H, H3a), 3.23 (dd,
J = 16.8 Hz, J = 6.2 Hz, 1H, H3b), 3.54 (m, 1H, COCH2),
3.69 (m, 1H, COCH2), 4.06 (dd, J = 9.5 Hz, J = 6.2 Hz,
1H, H4), 4.35–4.50 (m, 2H, OCH2), 7.09–7.20 (m, 5H,
arom), 7.27 (m, 1H, arom), 7.37 (m, 2H, arom), 7.79 (d,
J = 7.6 Hz, 2H, arom).13C NMR: d 13.8 (CH3), 14.7
(CH3), 35.3 (N@C–CH2), 53.7 (CHCO), 60.9 (OCH2),
64.8 (OCH2), 82.0 (CPh2), 126.9, 127.5, 127.6, 127.8,
128.2, 128.4, 130.2, 132.5, 144.2, 144.2, 170.2 (C@N),
172.2 (CO2). GC–MS: m/z 337 (M, 12), 308 (MÀEt, 48),
260 (10), 208 (100), 206 (65), 165 (48), 104 (27), 77 (69),
4.11. 3-Acetyl-5-ethyl-2-phenyl-1-pyrrole (11)
1
Yellow solid. Yield: 18 mg, 33%. H NMR: d 1.29 (t,
J = 7 Hz, 3H, CH2CH3), 2.29 (s, 3H, CO–CH3), 2.64 (q,
J = 7 Hz, 2H, CH2CH3), 6.39 (d, J = 3 Hz, 1H, CH),
7.33–7.44 (m, 3H, H arom.), 7.52–7.56 (m, 2H, H arom.),
8.48 (s, 1H, NH). 13C NMR: d 13.3 (CH2CH3), 20.6
(CO–CH3), 29.1 (CH2CH3), 107.7, 122.0, 128.5, 128.5,
129.2, 132.8, 134.2, 135.4, 194.7 (CO–CH3). ES-MS (+):
m/z 214 (M+1). GC–MS: m/z 213 (M, 42), 199 (15), 198
(100), 91 (17), 77 (13), 43 (18). IR (CH2Cl2): m 1654 (s),
51 (23), 29 (21). IR (CH2Cl2): m 1659 (s), 1731 (s) cmÀ1
Anal. Calc. for C21H23NO3: C, 74.75; H, 6.87; N, 4.15.
Found: C, 74.63; H, 6.80; N, 4.29%.
.
4.8. 2-Ethoxy-3,4-di(methoxycarbonyl)-5,5-diphenyl-2H-
pyrrole (4)
3424 (m) cmÀ1
.
Mp: 50–52 °C. Anal. Calc. for
1
Yellow solid. Yield: 88 mg, 93%. H NMR: d 1.40 (t,
C14H15NO: C, 78.84; H, 7.09; N, 6.57. Found: C, 78.75;
H, 7.12; N, 6.50%.
J = 7.1 Hz, 3H, CH3), 3.69 (s, 3H, CO2CH3), 3.88 (s, 3H,
CO2CH3), 4.45 (q, J = 7.1 Hz, 2H, OCH2), 7.28 (bs, 10H,
arom).13C NMR: d 14.4 (CH3), 52.5 (CO2CH3), 53.6
(CO2CH3), 65.6 (OCH2), 84.5 (CPh2), 127.9, 128.0, 128.2,
128.3, 132.5, 139.5, 160.6 (C@O), 162.5 (C@O), 165.6
(C@N). GC–MS: m/z 379 (M, 73), 350 (MÀEt, 37), 319
(100), 306 (19), 275 (8), 260 (12), 232 (56), 204 (29), 132
(56), 118 (81), 105 (25), 77 (52), 59 (42), 29 (23), 15 (12).
IR (CH2Cl2): m 1588 (m), 1644 (m), 1731 (s) cmÀ1. Mp:
95–97 °C. Anal. Calc. for C21H21NO5: C, 69.64; H, 5.58;
N, 3.69. Found: C, 69.51; H, 5.69; N, 3.60%.
4.12. 3-Acetyl-5-tert-butyl-2-phenyl-1-pyrrole (12a)
Yellow-brown solid. Yield: 25 mg, 41%. 1H NMR: d
1.34 [s, 9H, C–(CH3)3], 2.28 (s, 3H, CO–CH3), 6.40 (d,
J = 6 Hz, 1H, CH), 7.36–7.46 (m, 3H, H arom.), 7.55 (d,
J = 7 Hz, 2H, H arom.). 13C NMR: d 29.1 (CO–CH3),
30.3 [C–(CH3)], 31.4 [C–(CH3)], 105.9, 121.8, 128.5,
128.6, 129.3, 133.0, 135.3, 141.9, 194.9, (CO–CH3). ES-
MS (+): m/z 242 (M+1). GC–MS: m/z 242 (M+1, 12),
241 (70), 227 (16), 226 (97), 198 (44), 185 (15), 184 (100),
183 (34), 168 (20), 167 (13), 115 (15), 77 (16), 43 (64). IR
(CH2Cl2): m 1664 (m), 3436 (m) cmÀ1. Mp: 183–185 °C.
Anal. Calc. for C16H19NO: C, 79.63; H, 7.94; N, 5.80.
Found: C, 79.70; H, 8.00; N, 5.76%.
4.9. 2-Ethoxy-3,4-diethyl-5,5-diphenyl-2H-pyrrole (5)
1
Colourless oil. Yield: 42 mg, 53%. H NMR: d 0.51 (t,
J = 7.6 Hz, 3H, CH3), 1.14 (t, J = 7.5 Hz, 3H, CH3), 1.37

P.J. Campos et al. / Journal of Organometallic Chemistry 691 (2006) 1075–1080
1079
4.13. (4R*,5S*)-4-Acetyl-2-tert-butyl-5-methoxy-5-phenyl-
1-pyrroline (12b)
105 (100), 77 (44), 43 (20). IR (CH2Cl2): m 1618 (m), 1175
(m), 1708 (s) cmÀ1. Anal. Calc. for C20H21NO2: C, 78.15;
H, 6.89; N, 4.56. Found: C, 78.02; H, 6.80; N, 4.50%.
Colourless oil. Yield: 11.6 mg, 17%. 1H NMR: d 1.31 [s,
9H, C–(CH3)3], 2.22 (s, 3H, CO–CH3), 2.54 (dd, J = 6 Hz,
17 Hz, 1H, CH), 3.22–3.34 (m, 2H, CH2), 3.27 (s, 3H,
OCH3), 7.31–7.40 (m, 5H, H arom.). 13C NMR: d 28.4
(CH2), 31.3 (CO–CH3), 35.7 [C–(CH3)], 36.7 [C–(CH3)],
52.2 (OCH3), 108.0, 125.9, 127.9, 128.6, 143.2, 188.4
(C@N), 205.9 (CO–CH3). ES-MS (+): m/z 274 (M+1).
GC–MS: m/z 273 (M, 3), 230 (11), 147 (11), 138 (12), 136
(6), 123 (9), 115 (8), 106 (8), 105 (100), 77 (26), 43 (20).
IR (CH2Cl2): m 1134 (w), 1606 (w), 1654 (w) cmÀ1. Anal.
Calc. for C17H23NO2: C, 74.69; H, 8.48; N, 5.12. Found:
C, 74.60; H, 8.39; N, 5.04%.
4.17. 3-Acetyl-2-phenyl-5-(N,N-dimethylamino)-1-pyrrole
(16)
Yellow oil. Yield: 8.5 mg, 15%. 1H NMR: d 2.24 (s, 3H,
CO–CH3), 2.78 [s, 6H, N(CH3)2], 5.77 (d, 1H, J = 3 Hz,
CH), 7.38–7.42 (m, 3H, H arom.), 7.50–7.54 (m, 2H, H
arom.), 7.96 (s, 1H, NH). 13C NMR: d 29.1 (CO–CH3),
42.4 [N–(CH3)2], 91.5 (CH), 121.6, 143.9 (7C), 194.76
(CO–CH3). ES-MS (+): m/z 229 (M+1). GC–MS: m/z
228 (M, 100), 213 (52), 211 (180), 207 (12), 185 (14), 171
(19), 170 (21), 144 (15), 143 (13), 142 (14), 115 (22), 114
(12), 85 (25), 77 (20), 66 (16), 43 (40), 42 (21), 39 (11). IR
(CH2Cl2): m 1661 (m), 3426 (m) cmÀ1. Anal. Calc. for
C14H16N2O: C, 73.66; H, 7.06; N, 12.27. Found: C,
73.53; H, 7.14; N, 12.09%.
4.14. 3-Acetyl-5,5-diphenyl-1-pyrrole (13)
1
Pale yellow solid. Yield: 28 mg, 43%. H NMR: d 2.33
(s, 3H, CO–CH3), 6.95 (d, J = 3 Hz, 1H, CH), 7.25–7.31
(m, 1H, H arom.), 7.38–7.47 (m, 5H, H arom.), 7.51–7.61
(m, 4H, H arom.), 8.77 (s, 1H, NH). 13C NMR: d 28.9
(CO–CH3), 108.5 (CH), 123.3, 124.0, 127.2, 128.4, 128.8,
129.0, 129.1, 131.3, 131.7, 132.2, 137.0, 194.5 (CO–CH3).
ES-MS (+): m/z 262 (M+1). GC–MS: m/z 262 (M+1,
12), 261 (60), 247 (20), 246 (100), 217 (19), 115 (15), 109
4.18. 3-Ethoxycarbonyl-2-phenyl-5-(N,N-dimethylamino)-
1-pyrrole (17)
1
Yellow-brown oil. Yield: 6.5 mg, 10%. H NMR: d 2.78
[s, 6H, N(CH3)2], 1.26 (t, J = 7 Hz, 3H, CO2–CH2CH3),
4.21 (q, J = 7 Hz, 2H, CO2–CH2CH3), 5.83 (d, 1H,
J = 3 Hz, CH), 7.28–7.41 (m, 3H, H arom.), 7.55–7.59
(m, 2H, H arom.), 7.92 (s, 1H, NH). 13C NMR: d 14.5
(CO2–CH2CH3), 42.6 [N(CH3)2], 59.7 (CO2–CH2CH3),
92.4 (CH), 111.4, 127.8, 128.2, 128.9, 131.6, 132.5, 143.8,
165.2 (CO2–CH2CH3). ES-EM (+): m/z 259 (M+1). GC–
MS: m/z 258 (M, 50), 230 (15), 130 (27), 32 (29), 28
(190), 77 (11). IR (CH2Cl2): m 1671 (m), 3427 (w) cmÀ1
.
Mp: 180–182 °C. Anal. Calc. for C18H15NO: C, 82.73; H,
5.79; N, 5.36. Found: C, 82.68; H, 5.74; N, 5.30%.
4.15. 3-Acetyl-5-para-tolyl-2-phenyl-1-pyrrole (14a)
1
Pale-yellow solid. Yield: 12 mg, 17%. H NMR: d 2.36
(100). IR (CH2Cl2): m 1122 (w), 1723 (s), 3437 (w) cmÀ1
.
(s, 3H, CH3–C6H4), 2.38 (s, 3H, CO–CH3), 6.93 (d,
J = 3 Hz, 1H, CH), 7.21–7.26 (m, 2H, H arom.), 7.41–
7.48 (m, 5H, H arom.), 7.59–7.63 (m, 2H, H arom.), 8.57
(s, 1H, NH). 13C NMR: d 21.3 (CH3–C6H4), 29.21 (CO–
CH3), 108.1, 123.4, 124.1, 128.6, 128.7, 128.9, 129.3,
129.9, 132.1, 132.5, 136.9, 137.3, 194.7 (CO–CH3). ES-
MS (+): m/z 276 (M+1). GC–MS: m/z 275 (M, 74), 261
(20), 260 (100), 130 (12), 115 (11). IR (CH2Cl2): m 1178
(w), 1661 (s), 3436 (m) cmÀ1. Mp: 175–177 °C. Anal. Calc.
for C19H17NO: C, 82.88; H, 6.22; N, 5.09. Found: C, 82.80;
H, 6.28; N, 4.98%.
Anal. Calc. for C15H18N2O2 C, 69.74; H, 7.02; N, 10.84.
Found: C, 69.63; H, 6.91; N, 10.76%.
4.19. 3-Ethoxy-5-methoxy-5-phenyl-1,5-dihydropyrrole-2-
one (18)
Yellow oil. Yield: 23 mg, 40%. 1H NMR (CDCl3): d 1.43
(t, 3H, J = 7 Hz, OCH2CH3), 3.35 (s, 3H, OCH3), 3.96 (qd,
2H, J = 7, 2 Hz, OCH2CH3), 5.49 (d, 1H, J = 2 Hz, CH),
6.25 (s, 1H, NH), 7.33–7.39 (m, 3H, H arom.), 7.50–7.53
(m, 2H, H arom.). 13C NMR (CDCl3): d 14.3 (OCH2CH3),
50.5 (OCH3), 66.7 (OCH2CH3), 90.0 (COMePh), 111.9,
125.5, 128.8, 158.8, 139.8, 150.1 (C@N), 167.3 (C@O).
ES-EM (+Na): m/z 256 (M+23). IR (CH2Cl2): m 1260
(vs), 1423 (s), 1710 (w), 3420 (w) cmÀ1. Anal. Calc. for
C12H15NO3: C, 66.94; H, 6.48; N, 6.00. Found: C, 66.87;
H, 6.36; N, 5.92%.
4.16. (4R*,5S*)-4-Acetyl-5-phenyl-5-methoxy-2-para-tolyl-
1-pyrroline (14b)
1
Yellow oil. Yield: 32 mg, 41%. H NMR: d 2.27 (s, 3H,
CO–CH3), 2.44 (s, 3H, CH3–C6H4), 2.95 (dd, J = 8 Hz,
17 Hz, 1H), 3.36 (s, 3H, OCH3), 3.47–3.52 (m, 1H), 3.68
(dd, J = 5 Hz, 17 Hz, 1H), 7.26–7.46 (m, 7H, H arom.),
7.92 (d, 7H, H arom.). 13C NMR: d 21.7 (CH3–C6H4),
31.2 (CO–CH3), 37.0 (CH2), 52.4 (OCH3), 61.9 (CH),
108.5–143.2 (9C), 175.2 (CO–CH3), 205.5 (C@N). ES-MS
(+): m/z 308 (M+1). GC–MS: m/z 307 (M, 4), 292 (12),
264 (15), 233 (18), 275 (12), 172 (25), 129 (12), 115 (20),
5. Supplementary material
Crystallographic data for the 6 and 9 have been depos-
ited with the Cambridge Crystallographic Data Centre as
supplementary publication numbers CCDC 218076 and
218077, respectively. Copies of the data can be obtained,

1080
P.J. Campos et al. / Journal of Organometallic Chemistry 691 (2006) 1075–1080
[5] L.S. Hegedus, B.R. Lundmark, J. Am. Chem. Soc. 111 (1989) 9194;
L.S. Hegedus, A. Kramer, Organometallics 3 (1984) 1263.
[6] See, for example L.M. Reeder, L.S. Hegedus, J. Org. Chem. 64 (1999)
3306;
free of charge, on application to CCDC, 12 Union Road,
Cambridge, CB2 1EZ, UK [fax: +44 0 1223 336033 or
e-mail: deposit@ccdc.cam.ac.uk].
S. Koebbing, J. Mattay, Tetrahedron Lett. 33 (1992) 927;
L.S. Hegedus, R.W. Bates, B.C. Soderberg, J. Am. Chem. Soc. 113
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Acknowledgements
This work was supported by the Spanish MCyT/FED-
B. Soderberg, L.S. Hegedus, M.A. Sierra, J. Am. Chem. Soc. 112
(1990) 4363.
[7] See, for example I. Merino, L.S. Hegedus, Organometallics 14 (1995)
2522;
B.C. Soderberg, L.S. Hegedus, J. Org. Chem. 56 (1991) 2209.
[8] See, for example C.A. Merlic, D. Xu, B.G. Gladstone, J. Org. Chem.
58 (1993) 538;
´
ER (BQU2001-1625) and Comunidad Autonoma de La
Rioja (ACPI 2003/08). M.C. and S.L.-S. thank the Spanish
´
MEC for their fellowship. D.S. is financed by the Ramon y
Cajal program from the MEC.
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