Samarium diiodide promoted reactions of a diphenyl α-iminoketone, a new synthesis of some pyrrole derivatives

Article abstract of DOI:10.1016/S0040-4020(01)00416-1

The reduction of a diphenyl α-iminoketone with samarium diiodide has been studied. A fast two-electron transfer gives a samarium (Z)-enamidolate, which is protonated to afford an α-aminoketone or reacted with a variety of ketones to furnish pyrrole derivatives. Possible mechanisms are proposed.

Full text of DOI:10.1016/S0040-4020(01)00416-1

TETRAHEDRON
Pergamon
Tetrahedron 57 .2001) 4881±4888
Samarium diiodide promoted reactions of a diphenyl
a-iminoketone, a new synthesis of some pyrrole derivatives
Sorin Farcas and Jean-Louis Namyp
  Â
Laboratoire de Catalyse Moleculaire, associe au CNRS, ICMO, Bat 420, Universite Paris-Sud, 91405 Orsay, France
Dedicated to Professor H. B. Kagan on the occasion of his 70th birthday
Received 15 December 2000; revised 2 April 2001; accepted 9 April 2001
AbstractÐThe reduction of a diphenyl a-iminoketone with samarium diiodide has been studied. A fast two-electron transfer gives a
samarium .Z)-enamidolate, which is protonated to afford an a-aminoketone or reacted with a variety of ketones to furnish pyrrole derivatives.
Possible mechanisms are proposed. q 2001 Elsevier Science Ltd. All rights reserved.
1. Introduction
reported.5±7 However, products are slowly obtained with
moderate yields. In order to overcome this drawback, we
tried to extend a previously reported preparation of imines,8
to the synthesis of a-iminoketones. We were pleased to
succeed in preparing 1,2-diphenyl-2-propylimino-ethanone
1 and 4-propylimino-hexan-3-one 2, by the treatment of
propyl amine with LiAlH4, in THF followed by the addition
During the past 10 years, some studies have been devoted to
reactivity of samarium.II) compounds with a-diketones.
Thus, it has been demonstrated that benzil is reduced into
benzoin with 2 equiv. of samarium diiodide in the presence
of a proton source.1,2 Interestingly, with quinidine,
.R)-benzoin can be obtained with enantiomeric excess up
to 91%. A samarium .Z)-enediolate, generated by a two-
electron transfer from 2 equiv. of SmI2 to benzil is con-
sidered to be the intermediate of this reaction. Trapping of
this species has been achieved with acetic anhydride
.Scheme 1).1
Besides, samarium diiodide-mediated coupling reactions
between aliphatic a-diketones and aldehydes have been
performed, affording 2,3-dihydroxyketones in good yields.
This coupling probably proceeds through reaction of a
samarium enediolate with an aldehyde .Scheme 2).3
In addition, we have recently reported a similar trapping of
an enediolate, resulting of a samarium diiodide-mediated
coupling reaction between an ester and an acid chloride.4
Scheme 1.
These ®ndings prompt us to investigate the reactions of
samarium.II) compounds with versatile substrates such as
a-iminoketones which might give valuable compounds.
2. Results and discussion
Several routes for synthesis of a-iminoketones have been
Keywords: samarium diiodide; imino ketones; amino ketones; pyrroles;
coupling reactions; samarium enolates.
p
Corresponding author. Tel.: 133-1-69-15-4743; fax: 133-1-69-15-4680;
e-mail: jelonamy@icmo.u-psud.fr
Scheme 2.
0040±4020/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020.01)00416-1

4882
S. Farcas, J.-L. Namy / Tetrahedron 57 /2001) 4881±4888
Scheme 3.
Scheme 6.
NMRspectrum with those of the related products, . Z) and
.E)-O,O0-diacetyl-1,2-diphenylethen-1,2-diol,1 shows that
the formation of the .Z) isomer is likely .Scheme 4).15
It can therefore, be presumed that the reduction of this
a-iminoketone with 2 equiv. of SmI2 gives a dianionic
species 5 or 50 according to the process indicated in Scheme
5.
With the aim of preparing hydroxyaminoketones, 5 .or 50)
was quenched with a carbonyl compound .ketone or alde-
hyde). We were surprised at isolating pyrrole derivatives
instead, with good yields .Scheme 6).
Scheme 4.
of benzil or 3,4-hexanedione. The products were obtained
with excellent yields in a short reaction time .Scheme 3).
Results with ketones having a single methylene group or
2 equiv. methylene groups linked to the carbonyl group
are gathered in Table 1.
Reduction of a-iminoketones has been performed with a
variety of reducing agents. Either a-aminoketones or
aminoalcohols are obtained according to experimental
conditions.9±13 We found that samarium diiodide reacts
instantaneously with a-iminoketone 1, to give exclusively
1,2-diphenyl-2-propylamino-ethanone 3 after hydrolysis,
with an excellent yield .Scheme 4).
As reactions were slow at 208C, 4±10 equiv. of ketone were
used. However, ketone in excess was easily separated from
pyrrole. Better results were obtained that way than perform-
ing reactions at 608C with 1 equiv. ketone. Camphor and
cyclobutanone did not give pyrrole derivatives .entries 3
and 4). The procedure II .Table 1, note b) must be used
with aromatic ketones .entries 8±12), which are prone to
pinacolic coupling. It can just as well be used with aliphatic
ketones. With 4-propylimino-hexane-3-one 2 and acetone,
under the same experimental conditions, a similar reaction
occurred, giving the expected pyrrole .2,3-diethyl-5-
methyl-1-propyl-1H-pyrrole 16) but only in 20% yield
.the main product is 4-propylamino-hexan-3-one).
The reaction can be also achieved with ethanol as an in situ
proton source. However, small amounts of desoxybenzoin
arising from a reductive cleavage of the carbon±nitrogen
bond, according to a well-known process,14 were detected
under these conditions. In order to identify the samarium
species whose hydrolysis gives the aminoketone, we
allowed it to react with acetic anhydride in excess,
a-acetoxy-a0-.N-propylacetylamino)stilbene 4 was then
1
isolated as a single diastereomer. Comparison of its H
With ketones having two non-equivalent methylene groups
Scheme 5.

S. Farcas, J.-L. Namy / Tetrahedron 57 /2001) 4881±4888
Table 1. Synthesis of pyrroles from ketones with a single type of methylene group
4883
Entry
1a
R1; R2
x
Time .h)
Products and isolated yields .%)
6; 84
CH3; H
10
6
2a
i-Pr; H
10
12
7; 76
3a
4a
Camphor
±.CH2)2±
5
10
12
48
±
±
5a
±.CH2)3±
±.CH2)4±
6
6
12
12
8; 96
9; 73
6a
7a
±.CH2)6±
C6H5; C6H5
C6H5; H
5
4
6
6
6
6
12
6
10; 78
11; 72
12; 65
13; 68
14; 75
15; 62
8b
9b
12
12
6
10b
11b
C6H5; CH3
a-indanone
a-tetralone
12b
6
a
Procedure I: samarium diiodide was added dropwise over 10 min to a mixture of a-iminoketone and x equiv. ketone .see Section 4).
Procedure II: samarium diiodide was added dropwise over 10 min to a-iminoketone then x equiv. ketone were added .see Section 4).
b
a mixture of two pyrroles was obtained .Table 2), though
1-phenyl-2-propanone afforded a single product .entry 3).
Finally, an attempt at synthesis of a furane from benzil was a
failure, and benzoin was obtained instead after hydrolysis
.Scheme 8).
Interestingly, b-tetralone gave large predominance of one of
the two pyrroles .Scheme 7).
Syntheses of pyrroles derivatives have been recently
reviewed.19 In particular, the condensation of carbonyl
compounds with a-aminoketones gives pyrroles. It is
known as the Knorr pyrrole synthesis. The reaction proceeds
by initial enamine formation. However, in most examples
the carbonyl compounds are b-ketoesters or b-diketones
and the experimental conditions are very different from
ours. A plausible mechanistic pathway to pyrrole is illus-
trated in Scheme 9, though the details are unclear as yet.
Besides, diisopropyl ketone was unreactive under the same
experimental conditions as well as 3,4-hexanedione.
Aliphatic aldehydes .pentanal and hexanal) furnished a
complex mixture of products. The main ones .detected
by GC±MS), were 2,4,6-trialkyl-1,3,5-trioxacyclohexane
.mixture of stereomers) arising from a trimerization of alde-
hydes, esters resulting of a Tishchenko-type reaction, and
homo-aldol reaction products. It is known that these reac-
tions are ef®ciently catalyzed by lanthanide .III) salts.16±18
The species 5 that is generated by a two-electron transfer

4884
S. Farcas, J.-L. Namy / Tetrahedron 57 /2001) 4881±4888
Table 2. Synthesis of pyrroles from ketones with two non-equivalent methylene groups
Entry
1a
R1; R2
x
Time .h)
Products .A1B) and isolated yields .%)
A/B
CH3; H
10
12
60/40
2a
n-C5H11; H
6
6
6
6
62/38
100/0
3a
C6H5; H
a
Procedure I: samarium diiodide was added dropwise over 10 min to a mixture of a-iminoketone and x equiv. ketone.
from 2 equiv. of SmI2 to the a-iminoketone, reacts with
ketone to give an enolate C and the species 20. A subsequent
reaction furnishes adduct D which upon cyclization gives
product E whose hydrolysis leads to F, and then a fast
dehydration occurs that gives rise to a pyrrole. Such a
mechanism is in agreement with the lack of reactivity of
cyclobutanone, which is not prone to enolization, and diiso-
propyl ketone, which has no methylene groups. Assuming
this mechanism is true, it appears also that enolization invol-
ving the less hindered methylene group is the predominant
pathway .see Table 2 and Scheme 7). All these transforma-
tions might be facilitated by the presence of samarium.III)
salts.
3. Conclusion
In conclusion, two a-iminoketones have been readily pre-
pared from benzil or 3,4-ethanedione and a primary amine.
The diphenyl a-iminoketones undergoes a two-electron
transfer from 2 equiv. of SmI2 to give a dianionic species
5 .or 50) which can be trapped by acetic anhydride in excess
to give the corresponding diacetylated compound 4 having
the .Z) con®guration. Protonation of the dianionic species
furnishes the a-aminoketone 3, whereas reactions with a
variety of ketones give pyrrole derivatives with good yields.
With the aliphatic a-iminoketone, a pyrrole is also obtained,
though in modest yield .20%). Mechanistic schemes have
Scheme 7.
Scheme 8.

S. Farcas, J.-L. Namy / Tetrahedron 57 /2001) 4881±4888
4885
Scheme 9.
been proposed. We are currently studying preparation of
some others aromatic and aliphatic a-iminoketones and
reactions of these compounds, especially trapping of the
dianionic or radical±anionic species generated by electron
transfer from samarium.II) derivatives, with a variety of
substrates.
4.2. Preparation and reduction of iminoketones
4.2.1. 1,2-Diphenyl-2-propylimino-ethanone, 1. Propyl-
amine .40 mmol, 0.329 mL) was added dropwise, with
stirring to LiAlH4 .10 mmol) in THF .40 mL), at room
temperature. Stirring was maintained for 5 min, and then
benzil .40 mmol) in THF .10 mL) was added dropwise.
The mixture was stirred for 10 min. The work-up was
done by successive addition of H2O .2 mL), and 10%
NaOH .0.5 mL). After ®ltration and evaporation of the
solvent, 875 mg of crude product were obtained which
4. Experimental
4.1. General
1
from H and 13C NMRspectra contained only the desired
a-ketoimine .yield 87%). Attempt at puri®cation of the
product by ¯ash chromatography on silica gel results in
partial transformation .,15%) into benzil, distillation
under reduced pressure leads to degradation of the
product.
1H- and 13C NMRspectra were recorded at 250 and
63 MHz, respectively on a Bruker AM 250 instrument
.unless otherwise stated). Chemical shifts are reported in
part per million .d) down®eld from TMS. Infrared .IR)
spectra were recorded neat on a FTIRIFS 66 Bruker and
1
Yellow powder, yield: 87%. H NMR.CDCl ) d .ppm):
are reported in cm21
.
3
0.90 .3H, t, Jˆ7.3 Hz); 1.70 .2H, sext, Jˆ6.8 Hz); 3.39
Mass spectra .MS) were determined on a GC±MS
Ribermag R10-10 instrument. Electronic impact was
performed at 70 eV. High Resolution Mass Spectra were
performed on a GC±MS Finningan-MAT-95-S. Flash
chromatography was performed on silica gel .Merck 230±
240 mesh; 0.0040±0.0630 mm).
.2H, t, Jˆ6.8 Hz); 7.3±8.0 .10H, m). 13C NMR.CDCl ) d
3
.ppm): 11.8 .CH3); 24.2 .CH2) 55.6 .CH2N); 127.1; 128.6;
129.1; 130.7; 134.5; 134.6; 135.3; 166.2 .CvN); 199.1
.CvO). GC±MS m/z .% base peak): 43 .17); 51 .18); 77
.47); 104 .100); 146 .55); 251 .1). HRMS calcd for
C17H17NO: 251.1310, found: 251.1308.
All commercially available organic compounds were
distilled before use. Samarium was purchased from the
Acros Company. Tetrahydrofuran was distilled under
argon from sodium benzophenone ketyl. Samarium diiodide
was prepared as previously described.20
4.2.2. 4-Propylimino-hexan-3-one, 2. The compound is
prepared by the experimental procedure described above
for 1, it is puri®ed by distillation under reduced pressure.
1
Yellow oil, yield: 75%. H NMR.CDCl ) d .ppm): 0.90
3
.3H, t, Jˆ7.6 Hz); 0.91 .3H, t, Jˆ7.3 Hz); 1.02 .3H, t, Jˆ
7.3 Hz); 1.67 .2H, sext, Jˆ7.3 Hz); 2.44 .2H, q, Jˆ7.6 Hz);
2.82 .2H, q, Jˆ7.3 Hz); 3.43 .2H, t, Jˆ6.8 Hz). 13C NMR
All reactions were carried out under argon in Schlenk tubes
using standard vacuum line techniques.

4886
S. Farcas, J.-L. Namy / Tetrahedron 57 /2001) 4881±4888
.CDCl3) d .ppm): 7.9 .CH3); 10.8 .CH3); 11.9 .CH3); 18.7
.CH2); 23.8 .CH2); 29.8 .CH2); 53.4 .CH2N); 169.7 .CN);
203.0 .CO). GC±MS m/z .% base peak): 41.16); 43.17);
55.30); 56.100); 98.24); 155.1); 156.4). HRMS calcd for
C9H17NO: 155.1310, found: 155.1308.
color of SmI2 turned immediately yellow. Stirring was
continued for 3±12 h, The mixture was then quenched
with 20 mL of HCl .1 M) and stirred for 30 min to obtain
a clear solution and then extracted with ether. The combined
extracts were washed with sodium thiosulfate and brine.
The organic layer was dried over MgSO4 and the solvents
were removed under reduced pressure. The crude material
was puri®ed by ¯ash chromatography on silica gel.
4.2.3. 1,2-Diphenyl-2-propylamino-ethanone, 3. In a
Schlenk tube under argon, to 1 mmol of a-iminoketone in
10 mL of THF, were added dropwise in 10 min, 20 mL of a
0.1 M solution of SmI2 in THF, at 208C. The blue-green
color of SmI2 turned immediately yellow. Stirring was
maintained for 10 min. The mixture was then quenched
with HCl .0.1 M) and stirred for 30 min to obtain a clear
solution and then extracted with ether. The combined
extracts were washed with sodium thiosulfate and brine.
The organic layer was dried over MgSO4 and the solvents
were removed under reduced pressure. The crude material
was recrystallized from ether.
Procedure II. In a Schlenk tube under argon, to 1 mmol of
a-iminoketone in 10 mL of THF, were added dropwise in
10 min, 20 mL of a 0.1 M solution of SmI2 in THF, at 208C.
The blue-green color of SmI2 turned immediately yellow.
Stirring was maintained for 10 min, 4±10 mmol of ketone
were then added and stirring was continued for 3±12 h.
Work-up was performed as described above in procedure I.
4.3.1. 5-Methyl-2,3-diphenyl-1-propyl-1H-pyrrole, 6.
Puri®cation: eluent CH2Cl2/pentane .1/1), yellow oil,
White crystals, yield: 85%. 1H NMR.CDCl 3) d .ppm): 0.81
.3H, t, Jˆ7.3 Hz); 1.96 .2H, sext, Jˆ7.3 Hz); 2.92 .2H, t,
Jˆ8.3 Hz); 6.40 .1H, s); 7.2±8.0 .10H, m); 9.1 .1H, s). 13C
NMR.CDCl 3) d .ppm): 11.2 .CH3); 19.9 .CH2); 47.6
.CH2N); 66.2 .CH); 128.1; 128.9; 129.5; 130.0; 130.3;
130.7; 132.9; 134.5; 192.4 .CO). HRMS calcd for
C17H19NO: 253.1467, found: 253.1464.
1
yield: 84%. H NMR.CDCl ) d .ppm): 0.80 .3H, t, Jˆ
3
7.8 Hz); 1.59 .2H, sext, Jˆ7.8 Hz); 2.40 .3H, s); 3.74
.2H, t, Jˆ7.8 Hz); 6.26 .1H, s); 7.04±7.47 .10H, m). 13C
NMR.CDCl ) d .ppm): 11.11 .CH3); 12.4 .CH3); 24.3
3
.CH2); 45.6 .CH2N); 106.7 .C4); 121.4; 124.6; 127.3;
127.5; 127.9; 128.4; 128.5; 129.6; 131.3; 133.8; 136.6.
GC±MS m/z .% base peak): 217 .13); 232 .18); 246 .64);
260 .5); 275 .100). HRMS calcd for C20H21N: 275.1674,
found: 275.1673.
4.2.4. /Z)-a-Acetoxy-a0-/N-propylacetylamino)stilbene,
4. In a Schlenk tube under argon, to 1 mmol of a-imino-
ketone in 10 mL of THF, were added dropwise in 10 min,
20 mL of a 0.1 M solution of SmI2 in THF, at 208C. The
blue-green color of SmI2 turned immediately yellow.
Stirring was maintained for 10 min, 15 mmol of acetic
anhydride were then added and the mixture was stirred
during an additional period of 1.5 h. The mixture was then
quenched with HCl .0.1 M) and stirred for 30 min to obtain
a clear solution and then extracted with ether. The combined
extracts were washed with sodium thiosulfate and brine.
The organic layer was dried over MgSO4 and the solvents
were removed under reduced pressure. The crude material
was puri®ed by ¯ash chromatography on silica gel.
4.3.2. 5-Isopropyl-2,3-diphenyl-1-propyl-1H-pyrrole, 7.
Puri®cation: eluent CH2Cl2/pentane .1/1), yellow oil,
1
yield: 76%. H NMR.CDCl ) d .ppm): 0.78 .3H, t, Jˆ
3
7.3 Hz); 1.46 .6H, d, Jˆ6.8 Hz); 1.55 .2H, sext, Jˆ
7.3 Hz); 3.05 .1H, sept, Jˆ6.8 Hz); 3.81 .2H, t, Jˆ
7.8 Hz); 6.31 .1H, s); 7.05±7.5 .10H, m). 13C NMR
.CDCl3) d .ppm): 11.1 .CH3); 23.7 .CH3); 24.8 .CH2);
25.8 .CH); 45.4 .CH2N); 103.2 .C4); 121.5; 124.5; 127.3;
127.4; 127.8; 128.4; 129.2; 131.3; 133.9; 136.7; 140.0. GC±
MS: m/z .% base peak): 246 .10); 288 .100); 303 .52).
HRMS: calcd for C22H25N: 303.1987, found: 303.1986.
4.3.3. 2,3-Diphenyl-1-propyl-1,4,5,6-tetrahydrocyclo-
penta[b]pyrrole, 8. Puri®cation: eluent CH2Cl2/pentane
Puri®cation: eluent AcOEt/pentane .1/2), colorless oil,
yield: 72%. FTIR.®lm): 2967, 1768, 1653, 1493, 1446,
1391, 1368, 1296, 1276, 1242, 1198, 1128, 1068,
1
.1/1), yellow crystals, yield: 69%. H NMR.CDCl ) d
3
.ppm): 0.81 .3H, t, Jˆ7.3 Hz); 1.6 .2H, sext, Jˆ7.3 Hz);
2.53 .2H, q, Jˆ6.8 Hz); 2.83 .2H, t, Jˆ6.8 Hz); 2.91 .2H,
t, Jˆ6.8 Hz); 3.71 .2H, t, Jˆ7.3 Hz); 7.01±7.42 .10H, m).
1
1023 cm21. H NMR.CDCl ) d .ppm): 0.79 .3H, t, Jˆ
3
7.3 Hz); 1.4±1.7 .2H, m); 2.17 .3H, s); 2.19 .3H, s);
3.04±3.16 .1H, m, NCH2); 3.39±3.51 .1H, m, CH2N);
13C NMR.CDCl ) d .ppm): 11.2 .CH3); 24.4 .CH2); 25.1
3
7.12±7.23 .10H, m). 13C NMR.CDCl ) d .ppm): 11.4
.CH2); 26.2 .CH2); 28.6 .CH2); 47.2 .CH2N); 117.4 .C4);
124.4; 124.9; 127.2; 127.8; 128.4; 131.3; 132.7; 133.8;
136.7; 138.3. GC±MS: m/z .% base peak): 244 .12); 258
.21); 272 .46); 301 .100). HRMS calcd for C22H23N:
301.1830, found: 301.1828.
3
.CH3); 20.8 .CH3); 21.4 .CH2); 21.8 .CH3); 48.5 .CH2N);
128.2; 128.5; 128.8; 129.0; 129.6; 131.5; 134.3; 144.6;
168.7 .CO amide); 171.2 .CO ester). GC±MS m/z .%
base peak): 43 .41); 78 .34); 105 .63); 132 .10); 222 .13);
236 .4); 278 .100); 337 .1). HRMS calcd for C21H23NO3:
337.1678, found: 337.1676.
4.3.4. 2,3-Diphenyl-1-propyl-4,5,6,7-tetrahydro-1H-indole,
9. Puri®cation: eluent CH2Cl2/pentane .1/1), yellow
1
crystals, yield: 73%. H NMR.CDCl ) d .ppm): 0.77 .3H,
4.3. General procedures for samarium diiodide
promoted synthesis of pyrroles
3
t, Jˆ7.3 Hz); 1.48±1.64 .2H, m); 1.68±1.86 .2H, m); 1.88±
2.05 .2H, m); 2.55±2.75 .4H, m); 3.69 .2H, t, Jˆ7.8 Hz);
7.05±7.4 .10H, m). 13C NMR.CDCl 3) d .ppm): 11.2 .CH3);
22.5 .CH2); 23.0 .CH2); 23.4 .CH2); 23.8 .CH2); 24.6 .CH2);
45.5 .CH2N); 116.1 .C2, C4); 120.6; 124.7; 126.8; 127.6;
128.2; 129.6; 131.2; 133.4; 136.3. GC±MS m/z .% base
Procedure I. In a Schlenk tube under argon, to a mixture of
1 mmol of a-iminoketone and 4±10 mmol of ketone, in
10 mL of THF, were added dropwise in 10 min, 20 mL of
a 0.1 M solution of SmI2 in THF, at 208C. The blue-green

S. Farcas, J.-L. Namy / Tetrahedron 57 /2001) 4881±4888
4887
peak): 244 .11); 286 .34); 315 .100). HRMS calcd for
C23H25N: 315.1987, found: 315.1984.
4.3.10. 2,3-Diphenyl-1-propyl-4,5-dihydro-1H-benzo[g]-
indole, 15. Puri®cation: eluent CH2Cl2/pentane: .1/1),
1
yellow crystals, yield: 62%. H NMR.CDCl ) d .ppm):
3
4.3.5. 2,3-Diphenyl-1-propyl-4,5,6,7,8,9-hexahydro-1H-
cycloocta[b]pyrrole, 10. Puri®cation: eluent CH2Cl2/pen-
0.81 .3H, t, Jˆ7.8 Hz); 1.73 .2H, sext, Jˆ7.8 Hz); 2.77±
2.98 .4H, m); 4.19 .2H, t, Jˆ7.8 Hz); 7.12±7.53 .14H, m).
13C NMR.CDCl ) d .ppm): 10.9 .CH3); 21.3 .CH2); 24.3
1
tane .1/1), white crystals, yield: 78%. H NMR.CDCl ) d
3
3
.ppm): 0.72 .3H, t, Jˆ7.3 Hz); 1.4±1.8 .10H, m); 2.58 .2H,
t, Jˆ5.8 Hz); 2.8 .2H, t, Jˆ5.8 Hz); 3.74 .2H, t, Jˆ7.3 Hz);
7.0±7.3 .10H, m). 13C NMR.CDCl 3) d .ppm): 11.2 .CH3);
23.4 .CH2); 23.6 .CH2); 25.1 .CH2); 26.0 .CH2); 26.2 .CH2);
29.5 .CH2); 31.6 .CH2); 45.6 .CH2); 118.9 .C4); 122.2 .C2);
124.8; 126.4; 127.5; 127.9; 129.4; 130.5; 131.1; 133.8;
136.8. GC±MS m/z .% base peak): 202 .12); 230 .12);
244 .23); 258 .14); 274 .20); 288 .34); 314 .100);
343 .80). HRMS calcd for C25H29N: 343.2300, found:
343.2296.
.CH2); 31.3 .CH2); 47.2 .CH2N); 120.5; 120.9; 121.5; 124.6;
125.1; 126.5; 127.3; 127.7; 127.9; 128.2; 128.4; 129.7;
130.3; 131.5; 132.9; 133.5; 135.5; 136.9. GC±MS m/z .%
base peak): 320 .19); 334 .12); 363 .100). HRMS calcd for
C27H25N: 363.1987, found: 363.1987.
4.3.11. 2,3-Diethyl-5-methyl-1-propyl-1H-pyrrole, 16.
Puri®cation: eluent CH2Cl2/pentane: .1/1), yellow oil,
1
yield: 20%. H NMR.CDCl ) d .ppm): 0.94 .3H, t, Jˆ
3
7.3 Hz); 1.07±1.18 .6H, m); 1.54±1.74 .2H, m); 2.19 .3H,
s); 2.39 .2H, q, Jˆ7.3 Hz); 2.53 .2H, q, Jˆ7.3 Hz); 3.64
.2H, t, Jˆ7.8 Hz); 5.71 .1H, s). 13C NMR.CDCl 3) d .ppm):
11.4 .CH3); 12.3 .CH3); 15.7 .CH2); 16.0 .CH3); 17.7 .CH3);
19.1 .CH2); 24.8 .CH2); 45.2 .CH2N); 105.3 .C4). GC±MS
m/z .% base peak): 41.19); 53.5); 65.5); 77.7); 91.3);
107.7); 120.7); 122.11); 134.6); 136.4); 150.6); 164.100);
179.37). HRMS calcd for C12H21N: 179.1674, found:
179.1669.
4.3.6. 2,3,4,5-Tetraphenyl-1-propyl-1H-pyrrole, 11. Puri-
®cation: eluent CH2Cl2/pentane .1/1), yellow crystals, yield:
1
72%. H NMR.CDCl ) d .ppm): 0.58 .3H, t, Jˆ7.3 Hz);
3
1.39 .2H, sext, Jˆ7.3 Hz); 3.77 .2H, t, Jˆ7.8 Hz); 6.91±
7.05 .10H, m); 7.27±7.38 .10H, m). 13C NMR.CDCl ) d
3
.ppm): 11.1 .CH3); 24.5 .CH2); 46.3 .CH2N); 122.0; 124.9;
127.3; 127.3; 128.1; 130.9; 131.2; 131.4; 133.2; 135.6. GC±
MS m/z .% base peak): 265 .23); 293 .16); 308 .19); 384
.32); 413 .100). HRMS calcd for C31H27N: 413.2143, found:
413.2145.
4.3.12. 5-Ethyl-2,3-diphenyl-1-propyl-1H-pyrrole, 17
and 2,3-dimethyl-4,5-diphenyl-1-propyl-1H-pyrrole, 18.
Puri®cation: eluent CH2Cl2/pentane .1/1), yellow oil, yield
1
4.3.7. 2,3,5-Triphenyl-1-propyl-1H-pyrrole, 12. Puri®-
cation: eluent CH2Cl2/pentane .1/1), white crystals, yield:
84%, .mixture 60/40). H NMR.CDCl ) d .ppm): 0.6±0.9
3
.3H, m); 1.20±1.70 .3.8H, m); 2.11 .1.2H, s, CH3.16)); 2.31
.1.2H, s, CH3.16)); 2.70 .1.2H, q, Jˆ7.3 Hz, CH2.15));
3.65±3.80 .2H, m, CH2N); 6.24 .0.6H, s, CH.15)); 7.00±
7.5 .10H, m). 13C NMR.CDCl 3) d .ppm): 10.2; 11.2; 12.7;
19.8; 24.4; 24.6; 45.5; 45.9; 104.7 .C4, 15); 113.3 .C3, 16);
122.4; 124.6; 124.9; 125.1; 126.7; 127.3; 127.5; 127.6;
127.9; 128.0; 128.4; 129.6; 130.2; 130.6; 131.2; 131.4;
133.4; 133.8; 134.9; 136.5; 136.7. GC±MS m/z .% base
peak): 230 .12); 246 .20); 260 .58); 289 .100) .15), m/z
.% base peak): 232 .27); 260 .14); 274 .100); 289 .93)
.16). HRMS calcd for C21H23N: 289.1830, found:
289.1833 .15), found: 289.1829 .16).
1
65%. H NMR.CDCl ) d .ppm): 0.52 .3H, t, Jˆ7.3 Hz);
3
1.29 .2H, sext, Jˆ7.3 Hz); 3.93 .2H, t, Jˆ7.3 Hz); 6.51 .1H,
s); 7.1±7.6 .15H, m). 13C NMR.CDCl ) d .ppm): 10.8
3
.CH3); 24.0 .CH2); 46.5 .CH2); 109.4 .C4); 122.8; 125.0;
127.0; 127.3; 127.5; 127.6; 128.0; 128.4; 128.5; 129.0;
131.2; 133.5; 134.0; 135.1; 136.4. GC±MS m/z .% base
peak): 165 .13); 189 .37); 202 .11); 216 .11); 232 .18);
294 .28); 308 .58); 337 .100). HRMS calcd for C25H23N:
337.1830, found: 337.1822.
4.3.8. 3-Methyl-2,4,5-triphenyl-1-propyl-1H-pyrrole, 13.
Puri®cation: eluent CH2Cl2/pentane .1/1), yellow crystals,
1
yield: 68%. H NMR.CDCl ) d .ppm): 0.43 .3H, t, Jˆ
4.3.13. 5-Hexyl-2,3-diphenyl-1-propyl-1H-pyrrole, 19 and
2-methyl-3-pentyl-4,5-diphenyl-1-propyl-1H-pyrrole, 20.
Puri®cation: eluent CH2Cl2/pentane .1/1), yellow oil, yield:
3
7.3 Hz); 1.17 .2H, sext, Jˆ7.3 Hz); 2.07 .3H, s); 3.84
.2H, t, Jˆ7.3 Hz); 7.10±7.5 .15H, m). 13C NMR.CDCl )
3
1
d .ppm): 10.9 .CH3); 11.1 .CH3); 24.0 .CH2); 46.6
.CH2N); 115.9 .C3); 123.4; 125.0; 126.8; 126.9; 127.6;
128.2; 128.3; 130.3; 130.6; 131.1; 131.8; 132.2; 133.4;
133.5; 136.3. GC±MS m/z .% base peak): 308 .10); 322
.36); 351 .100). HRMS calcd for C26H25N: 351.1987,
found: 351.1975.
82%, .mixture 62/38). H NMR.CDCl ) d .ppm): 0.7±1.1
3
.6H, m, CH3); 1.15±2.05 .9.24H, m, CH2); 2.34 .1.14H, s,
CH3.18)); 2.51 .0.76H, t, Jˆ7.8 Hz, CH2.18)); 2.68 .1.24H,
t, Jˆ7.8 Hz, CH2.17)); 3.60±3.90 .2H, m, CH2N); 6.26
.0.62H, s, CH.17)); 7.0±7.5 .10H, m). 13C NMR.CDCl )
3
d .ppm): 10.3; 11.2; 14.1; 22.4; 22.6; 24.5; 24.7; 26.7; 28.6;
29.4; 31.4; 31.8; 31.9; 45.5; 45.8; 105.3 .C4, 17); 119.1;
121.4; 124.6; 124.9; 126.4; 127.3; 127.5; 127.9; 128.4;
129.4; 130.4; 131.1; 131.3; 133.6; 133.8; 136.7; 136.9.
GC±MS m/z .% base peak): 274 .100); 345 .34) .17), m/z
.% base peak): 288 .100); 345 .50) .18). HRMS calcd for
C25H31N: 345.2456, found: 345.2450 .17), found: 345.2441
.18).
4.3.9. 1,2-Diphenyl-3-propyl-3,8-dihydro-3-aza-cyclo-
penta[a]indene, 14. Puri®cation: eluent CH2Cl2/pentane
1
.1/1), yellow crystals, yield: 75%. H NMR.CDCl ) d
3
.ppm): 0.90 .3H, t, Jˆ7.3 Hz); 1.85 .2H, sext, Jˆ7.3 Hz);
3.82 .2H, s); 4.11 .2H, t, Jˆ7.3 Hz); 7.1±7.6 .14H, m). 13C
NMR.50.3 MHz-CDCl 3) d .ppm): 11.1 .CH3); 24.7 .CH2);
31.5 .CH2); 46.9 .CH2N); 116.3; 118.1; 123.0; 124.9; 125.3;
126.5; 127.7; 128.0; 128.5; 131.4; 133.1; 134.5; 135.6;
136.2; 137.9; 146.7. GC±MS m/z .% base peak): 304
.11); 320 .19); 349 .100). HRMS calcd for C26H23N:
349.1830, found: 349.1825.
4.3.14. 5-Benzyl-2,3-diphenyl-1-propyl-1H-pyrrole, 21.
Puri®cation: eluent CH2Cl2/pentane .1/1), yellow crystals,
1
yield: 85%. H NMR.CDCl ) d .ppm): 0.70 .3H, t, Jˆ
3
7.3 Hz); 1.45 .2H, sext, Jˆ7.8 Hz); 3.69 .2H, t, Jˆ7.8 Hz);

4888
S. Farcas, J.-L. Namy / Tetrahedron 57 /2001) 4881±4888
4.08 .2H, s); 6.17 .1H, s); 7.05±7.50 .15H, m). 13C NMR
.CDCl3) d .ppm): 11.1 .CH3); 24.4 .CH2); 33.4 .CH2); 45.7
.CH2N); 107.9 .C4); 121.5; 124.6; 126.3; 127.4; 127.9;
128.0; 128.4; 128.8; 130.2; 131.3; 131.5; 133.7; 136.5;
139.2. GC±MS m/z .% base peak): 91 .16); 232 .17); 274
.20); 322 .13); 351 .100). HRMS calcd for C26H25N:
351.1987, found: 351.1977.
5. Wheatley, W. B.; Fitzgibbon, W. E.; Cheney, L. C. J. Org.
Chem. 1953, 18, 1564±1571.
6. Jousseaume, B.; Vilcot, N.; Ricci, A.; Tiekink, E. R. T.
J. Chem. Soc., Perkin Trans. 1 1994, 2283±2287.
7. Barluenga, J.; Aznar, F.; Liz, R. J. Chem. Soc., Perkin Trans. 1
1983, 1093±1098.
Â
8. Solladie-Cavallo, A.; Bencheqroun, M.; Bonne, F. Synth.
Commun. 1993, 23, 1683±1687.
9. Alcaide, B.; Arjona, O.; De la Pradilla, R. F.; Plumet, J.;
Rodriguez-Campos, I. M.; Santesmases J. Chem. Res. Mini-
print 1988, 3, 932±957.
4.3.15. 2,3-Diphenyl-1-propyl-4,9-dihydro-1H-benzo[f]-
indole, 22. Puri®cation: eluent CH2Cl2/pentane .1/1),
1
yellow crystals, yield: 58%. H NMR.CDCl ) d .ppm):
3
10. Alcaide, B.; Escobar, G.; Gonzales-Simo, J. L.; Lopez-Mardo-
mingo, C.; Perez-Ossorio, R.; Plumet, J. Tetrahedron Lett.
1982, 23, 2033±2036.
0.84 .3H, t, Jˆ7.3 Hz); 1.65 .2H, sext, Jˆ7.3 Hz); 3.90
.2H, t, Jˆ7.3 Hz); 4.12 .4H, s); 7.16±7.5 .14H, m). 13C
NMR.CDCl 3) d .ppm): 11.2 .CH3); 24.6 .CH2); 27.5
.CH2); 28.5 .CH2); 45.7 .CH2N); 113.6 .C4); 120.2;
122.9; 123.8; 124.9; 125.6; 126.0; 127.1; 127.8; 128.2;
129.2; 129.4; 129.6; 130.7; 131.2; 133.2; 135.6; 136.2.
GC±MS m/z .% base peak): 286 .19); 363 .100). HRMS
calcd for C27H25N: 363.1987, found: 363.1978.
11. Alper, H.; Amaratunga, S. Tetrahedron Lett. 1981, 22, 3811±
3812.
12. Alcaide, B.; Lopez-Mardomingo, C.; Perez-Ossorio, R.;
Plumet, J. J. Chem. Soc., Perkin Trans. 2 1983, 1649±1653.
13. Shibata, I.; Moriuchi-Kawakami, T.; Tanizawa, D.; Suwa, T.;
Sugiyama, E.; Matsuda, H.; Baba, A. J. Org Chem. 1998, 63,
383±385.
14. Molander, G. A.; Stengel, P. J. Tetrahedron 1997, 53, 8887±
8912.
Acknowledgements
15. 1H NMRspectrum of product 4: 2.17 .3H, s, CH3CO); 2.19
.3H, s, CH3CO); 7.12±7.23 .10H, bs, aromatic) is very similar
to that of .Z)-O,O0-diacetyl-1,2-diphenylethen-1,2-diol: 2.20
.6H, s, CH3CO); 7.24 .10H, bs, aromatic) but different from
that of the .E) isomer: 2.08 .6H, s, CH3CO); 7.36 and 7.54
.10H, m, aromatic).
We thank the University of Paris-Sud and the CNRS for
 Â
their ®nancial support and the Societe de Secours des
Amis des Sciences for a studentship .S. F.).
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