Atom-economic, solvent-free, high yield synthesis of 2-(pyrrol-1-yl) propyldiorganylphosphines

Article abstract of DOI:10.1055/s-2005-861842

Free-radical addition of secondary phosphines to 1-isopropenylpyrroles (AIBN, 65°C) proceeds with 100% regioselectivity to give 2-(pyrrol-1-yl)propyldiorganylphosphines in 89-92% isolated yields. This constitutes a highly efficient, atom-economic, solvent-free ('green') synthesis of new promising ligands for metal complex catalysts, and potent building blocks for designing of drugs and advanced materials. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2005-861842

PAPER
965
Atom-Economic, Solvent-Free, High Yield Synthesis of 2-(Pyrrol-1-yl)propyl-
diorganylphosphines
S
ynthesis of 2-(P
o
yrrol-1-yl)pr
r
opyldior
i
ganylph
s
osphine
s
A. Trofimov,*a Nina K. Gusarova,a Boris G. Sukhov,a Svetlana F. Malysheva,a Olga A. Tarasova,a
Natalya A. Belogorlova,a Marina A. Maximova,a Sergey P. Tunikb
a
A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, 1 Favorsky Street, Irkutsk 664033,
Russia
Fax +7(3952)419346; E-mail: mal@irioch.irk.ru
Department of Chemistry, St.-Petersburg University, St.-Petersburg, Russia
b
Received 20 October 2004; revised 20 December 2004
to enantiomers. Such a reaction would open a straightfor-
Abstract: Free-radical addition of secondary phosphines to 1-iso-
ward atom-economic (‘green’) approach to the synthesis
of a new family of phosphorus-containing pyrroles, prom-
propenylpyrroles (AIBN, 65 °C) proceeds with 100% regioselectiv-
ity to give 2-(pyrrol-1-yl)propyldiorganylphosphines in 89–92%
isolated yields. This constitutes a highly efficient, atom-economic,
ising chelating P,N(p)-ligands for metal complex cata-
solvent-free (‘green’) synthesis of new promising ligands for metal lysts of a new generation,8 as well as reactive
complex catalysts, and potent building blocks for designing of
intermediates for the design of drugs and advanced mate-
drugs and advanced materials.
rials.
Key words: free-radical addition, 1-isopropenylpyrroles, phospho-
1-Isopropenylpyrroles 1a–c were found to add diorga-
rylation, regioselectivity, P,N-ligands, green chemistry
nylphosphines 2a–c regiospecifically in the presence of a
radical initiator, azoisobutyronitrile (AIBN), at 65 °C to
form 2-(pyrrol-1-yl)propyldiorganylphosphines 3a–e in
1-Isopropenylpyrroles 1a–c, now readily available thanks
89–92% yield (Scheme 1, Table 1).
to an efficient and convenient method for their synthesis
through isopropenylation of corresponding 1H-pyrroles
with propyne and (or) allene in the superbase system
KOH/DMSO,1 represent reactive building blocks for or-
ganic synthesis and prospective monomers. At the same
time, available data on the reactivity of 1-isopropenylpyr-
roles are limited to just one brief communication concern-
ing their interaction with thiols in the presence of radical
initiators giving anti-Markovnikov adducts.2 In the
present work, to gain a better understanding of the syn-
thetic potential of 1-isopropenylpyrroles and to further de-
velop the synthesis of tertiary phosphines by free-radical
addition reactions of diverse alkenes,3 we have studied the
free-radical reaction of 1-isopropenylpyrroles with sec-
Scheme 1
ondary phosphines, now directly prepared from elemental
phosphorus and electrophiles in superbase systems.4 Di-
Table 1 Hydrophosphination of 1-Isopropenylpyrroles with Sec-
alkylphosphinyl radicals are nucleophilic5 and the double
bond in N-vinylpyrroles is electron-rich due to the p-p
conjugation,6 hence the electron-donating methyl group at
the a-position of the ethenyl moiety is to be an additional
electronically unfavorable factor, let alone its anticipated
steric interference. Therefore, a preparatively meaningful
result of the addition of dialkylphosphines to 1-isoprope-
nylpyrroles, a new family of substituted N-vinylpyrroles,
was far from being predictable despite positive data for
unsubstituted N-vinylpyrroles.7 Meanwhile, to harness
this reaction would be a principal contribution to the tar-
geted synthesis of phosphines with pyrrole substituents
and an unsymmetrical carbon atom, capable of resolving
ondary Phosphinesa
Entry
Reactants (mmol)
Time
(h)
Prod- Yield
uct 3
(%)b
1-Isopropenyl-
pyrrole 1
(R4)2PH 2
1
2
3
4
5
1a (3.0)
1a (2.4)
1a (2.1)
1b (2.2)
1c (3.3)
2a (3.0)
2b (2.3)
2c (2.0)
2b (2.1)
2b (3.3)
288
21
3a
3b
3c
3d
3e
91
92
89
89
89
160
317
48
a All experiments were carried out under argon at 65 °C with AIBN
as an initiator (1–5 wt%).
SYNTHESIS 2005, No. 6, pp 0965–0970
Advanced online publication: 21.02.2005
DOI: 10.1055/s-2005-861842; Art ID: Z19504SS
x
x
.
x
x
.2
0
0
5
b Isolated yields.
© Georg Thieme Verlag Stuttgart · New York

966
B. A. Trofimov et al.
PAPER
As anticipated, the reaction conditions have proven to be,
for some pairs, substantially different (Table 1) from
those found for unsubstituted N-vinylpyrroles:7 in the
former case, up to 13 days (instead of 41 h) is required for
the completion of the reaction which is uncommon for
AIBN-initiated radical additions.
R2
R2
R1
Me
_
R3
P
R3
R1
Me
MeI
air
R4
R4
R4
R4
3b–d
Et2O, r.t., 1 h
N
N
I
P
O
Me
5b–d
4b–d
At the same time, the reaction of isopropenylpyrrole 1a
with bis(2-phenylethyl)phosphine 2b requires just 21
hours for its completion, whereas full conversion of
Scheme 4
dibenzylphosphine (2a) and bis[2-(pyridin-2-yl)eth- In summary, the addition of secondary phosphines to 1-
yl]phosphine (2c) is attained in 288 and 160 hours, respec- isopropenylpyrroles represents a straightforward atom-
tively (Table 1), thus implying unusually strong structural economic non-metal-catalyzed (‘green’) approach to C–P
effects. The reactivity of the phosphines in this process bond formation thus contributing to both pyrrole and
drops in the following order: 2b > 2c > 2a.
phosphine chemistry, especially to the hydrophosphina-
tion of heteroethenes (vinyl ethers,10 alkyl vinyl sulfides
and selenides,11 divinyl sulfide,12 N-vinylpyrroles7) under
free-radical conditions. Unlike N-vinylpyrrole-derived
phosphines,7 phosphines 3 containing an asymmetrical
carbon atom can be resolved to enantiomers by common
procedures and, therefore, are prospective chiral hemila-
bile ligands for enantioselective processes.13 The synthe-
sis of such ligands is usually complicated and requires the
use of organometallic compounds and aggressive highly
toxic phosphorus halides.14
Apart from steric hindrances, this fact can likely be ex-
plained by a lower stability of the dibenzylphosphinyl rad-
ical generated from dibenzylphosphine, as compared to
the corresponding bis(2-phenylethyl)- and bis[2-(pyridin-
2-yl)ethyl]phosphinyl radicals, for which a through space
stabilization with the formation of a five-membered ring
is conceivable (Scheme 2), as, e.g., it is observed for the
intermediate radicals formed in the N-vinylindole and
-carbazole radical polymerization.9
P
P
P
P
Diorganyl-2-(1-pyrrolyl)propylphosphines 3a–e; General Pro-
cedure
X
X
X
X
A mixture of secondary phosphine 24d,15 and 1-isopropenylpyrrole
(1)1 was heated at 65 °C in the presence of AIBN (1–5 wt% of the
total mass of reactants) in a sealed ampoule (reaction scale and time
are given in Table 1). The reaction was monitored using 31P NMR
by disappearance of signal of the starting secondary phosphine 2 in
the –70 ppm to –48 ppm region and appearance of new resonance
in the –32 ppm to –20 ppm interval, corresponding to tertiary phos-
phine 3 (for 31P monitoring, the ampoule was unsealed and a probe
of the reaction mixture was taken for analysis). The crude product,
a viscous undistillable liquid, was purified by column chromatogra-
phy (Al2O3, Et2O) to give the phosphine 3 (oil). Spectral character-
istics of compounds 3–5 are given in Table 2. All experiments were
carried out under argon.
X = CH, N
Scheme 2
In the case of dibenzylphosphinyl radical, such stabiliza-
tion may be realized, if any, only in a strained, hence, less
favorable four-membered structure (Scheme 3).
P
P
P
P
Scheme 3
[2-(2,3-Dimethyl-1H-pyrrol-1-yl)propyl]bis(phenylmeth-
yl)phosphine (3a)
Yield: 91%; light-yellow oil.
Comparative analysis of the hydrophosphination of iso-
propenylpyrroles 1a–c with the phosphine 2b indicates Anal. Calcd for C23H28NP: C, 79.06; H, 8.08; N, 4.00; P, 8.86.
Found: C, 79.21; H, 8.24; N, 3.80; P, 8.75.
(Table 1) that 1-isopropenyl-2,3-dimethylpyrrole (1a) is
the most reactive species in this reaction, while the least
[2-(2,3-Dimethyl-1H-pyrrol-1-yl)propyl]bis(2-phenyleth-
reactive is 1-isopropenyl-2-methyl-4,5,6,7-tetrahydroin-
yl)phosphine (3b)
dole (1b). This agrees with spatial structures of the pyr-
roles 1a–c and may be rationalized by steric hindrances.
Yield: 92%; light-yellow oil.
Anal. Calcd for C25H32NP: C, 79.54; H, 8.54; N, 3.71; P, 8.20.
Some preliminary information concerning the properties
of the polyfunctional compounds synthesized has been
obtained on phosphines 3b–d. Thus, methylation of 3b–d
with MeI proceeds under mild conditions (r.t., 1 h) to
quantitatively afford the phosphonium iodides 4b–d
(Scheme 4). When exposed to air, phosphines 3b,c quan-
titatively oxidize to phosphine oxides 5b,c (Scheme 4).
Under analogous conditions, conversion of the phosphine
3d to phosphine oxide 5d is just 10%.
Found: C, 79.65; H, 8.45; N, 3.84; P, 8.06.
[2-(2,3-Dimethyl-1H-pyrrol-1-yl)propyl]bis[2-(2-pyridinyl)eth-
yl]phosphine (3c)
Yield: 89%; light-yellow oil.
Anal. Calcd for C23H30N3P: C, 72.80; H, 7.97; N, 11.07; P, 8.16.
Found: C, 72.99; H, 8.08; N, 10.93; P, 7.95.
Synthesis 2005, No. 6, 965–970 © Thieme Stuttgart · New York

PAPER
Synthesis of 2-(Pyrrol-1-yl)propyldiorganylphosphines
967
Table 2 Spectral Data of Compounds 3–5a
Product
Structure
NMR, d, J (Hz)
1H
13C
31Pb
3ac
1.28 (d, 3 H, C7-H, 3J6,7 = 6.7), 9.32 and 9.52 (C3-CH3), 10.93
1.73–1.78 (m, 2 H, C8-H), 2.06 and 11.12 (C2-CH3), 22.39 and
–20.58
(s, 3 H, C3-CH3), 2.13 (s, 3 H,
22.49 (C7, 3JP,C = 9.4), 34.71,
C2-CH3), 2.37, 2.52, 2.63, 2.75 34.88 (C9, 1JP,C = 17.1), 36.08
(d, 4 H, C9-H, 2JH,H = 13.4),
(C8, 1JP,C = 20.1), 49.37 and
3.91–3.97 (m, 1 H, C6-H), 5.95 49.77 (C6, 2JP,C = 20.1 and
(d, 1 H, C4-H, 3J4,5 = 2.9), 6.55 21.0), 108.42 and 108.51 (C4),
(d, 1 H, C5-H), 7.07–7.32 (m,
10 H, C11–13-H)
113.71 and 113.84 (C5), 117.77
(C3), 123.67 (C2,), 125.44 and
125.58 (C13), 128.06 and
128.09 (C11), 128.69 and
128.91 (C12), 137.42 and
137.47 (C10, 2JP,C = 27.8 and
28.7)
3b
1.47 (d, 3 H, C7-H, 3J6,7 = 6.7), 9.95 (C3-CH3), 11.38 (C2-CH3), –31.29
1.51-1.80 (m, 6 H, C8,9-H), 2.0 23.00 (C7, 3JP,C = 8.6), 28.81
(s, 3 H, C3-CH3), 2.13 (s, 3 H,
and 29.38 (C9, 1JP,C = 15.1),
C2-CH3), 2.61-2.70 (m, 4 H,
32.15 and 32.29 (C10,
2
C10-H), 4.20-4.23 (m, 1 H, C6- JP,C = 14.7), 36.96 (C8,
H), 5.95 (d, 1 H, C4-H,
1JPC = 16.8), 50.05 (C6,
3J4,5 = 2.8), 6.55 (d, 1 H, C5-H), 2JP,C = 19.0), 108.95 (C4),
7.09-7.27 (m, 10 H, C12–14-H)
114.17 (C5), 114.37 (C3),
123.94 (C2), 125.94 and 126.03
(C14), 128.13, 128.43, 128.48,
128.73 (C12,13), 142.66 (C11,
3JP,C = 9.9)
3c
1.46 (d, 3 H, C7-H, 3J6,7 = 6.6), 9.57 (C3-CH3), 11.05 (C2-CH3), –31.38
1.60–1.84 (m, 6 H, C8,9-H), 22.73 (C7, 3JP,C = 8.1), 26.41
1.98 (s, 3 H, C3-CH3), 2.12 (s, 3 and 26.89 (C9, 1JP,C = 14.6 and
H, C2-CH3), 2.81-2.89 (m, 4
H, C10-H), 4.21-4.25 (m, 1 H,
C6-H), 5.91 (d, 1 H, C4-H,
13.7), 34.07 and 34.13 (C10,
2JP,C = 14.6), 36.59 (C8,
1JP,C = 17.1), 49.62 (C6,
3J4,5 = 2.9), 6.55 (d, 1 H, C5-H), 2JP,C = 18.8), 108.52 (C4),
7.05-7.09 (m, 4 H, C12,14-H),
7.50-7.51 (m, 2 H, C13-H),
8.47 (m, 2 H, C15-H)
113.80 (C5), 117.80 (C3),
120.75 and 120.80 (C14),
122.14 and 122.19 (C12),
123.50 (C2), 135.91 and 135.98
(C13), 148.81 and 148.87 (C15),
161.56 (C11, 3JP,C = 11.1)
3dd
1.51 (d, 3 H, C11-H,
11.88 and 11.65 (C2-CH3),
–28.66
3J10,11 = 7.2), 1.64–1.82 (m, 10 21.87, 22.55, 23.37, 23.48 (C4–
H, C5,6,12,13-H), 1.96 (s, 3 H, C2- 7), 23.42 (C11, 3JP,C = 11.0),
CH3), 2.42–2.48 (m, 4 H, C4,7
-
27.30 and 27.98 (C13,
H), 2.57–2.76 (m, 4 H, C14-H), 1JP,C = 14.6 and 14.1), 31.67
4.28–4.31 (m, 1 H, C10-H), 5.62 and 31.92 (C14, 1JP,C = 13.7),
(s, 1 H, C3-H), 7.15–7.21 (m,
34.10 (C12, 1JP,C = 14.6), 49.53
and 49.76 (C10, 2JP,C = 23.1 and
22.7), 107.95 (C3), 113.84 (C2),
115.95 (C9), 125.52 and 125.72
(C18), 126.18 (C8), 127.80,
128.03, 128.09, 128.32 (C16,17),
142.18 and 142.24 (C15,
10 H, C16–18
)
3JP,C = 10.0 and 10.7)
Synthesis 2005, No. 6, 965–970 © Thieme Stuttgart · New York

968
B. A. Trofimov et al.
PAPER
Table 2 Spectral Data of Compounds 3–5a (continued)
Product
Structure
NMR, d, J (Hz)
1H
13C
31Pb
–31.79
3e
1.43–1.59 (m, 4 H, C13-H), 1.58 22.47 (C11, 3JP,C = 8.5), 29.09
(d, 3 H, C11-H, 3J10,11 = 7.3), and 29.46 (C13, 1JP,C = 14.2),
1.88 and 2.07 (m, 2 H, C12-H), 32.32 and 32.39 (C14,
2.52-2.62 (m, 4 H, C14-H),
4.59-4.63 (m, 1 H, C10-H),
2JP,C = 14.1), 35.94 (C12,
1JP,C = 17.2), 50.63 (C10,
6.49 (d, 1 H, C3-H, 3J2,3 = 3.2), 2JP,C = 18.5), 101.98 (C3),
6.97-7.16 (m, 13 H, C2,5,6,16–18
-
109.95 (C7), 119.75 (C6),
121.43 (C4), 121.69 (C5),
H), 7.17 (d, 1 H, C7-H,
3J6,7 = 7.0), 7.21 (d, 1 H, C4-H, 124.30 (C2), 126.28 and 126.31
3J4,5 = 7.0)
(C18), 128.38, 128.41, 128.74
(C16,17), 129.01 (C9), 135.70
(C8), 142.78 (C15, 3JP,C = 8.5)
4b
1.48 (d, 3 H, C7-H, 3J6,7 = 5.8), 5.37 (C15, 1JP,C = 49.7), 10.25
30.28
1.79 (d, 3 H, C15-H,
(C3-CH3), 11.16 (C2-CH3),
21.91 and 22.34 (C9,
1JP,H = 13.4), 1.91 (s, 3 H, C3-
CH3), 2.09 (s, 3 H, C2-CH3),
2.31–2.71 (m, 4 H, C9-H),
2.80–2.89 (m, 4 H, C10-H),
1JP,C = 44.9 and 45.8), 24.84
(C7, 3JP,C = 14.1), 27.48 and
27.51 (C10, 2JP,C = 7.3 and 7.5),
3.11–3.50 (m, 2 H, C8-H), 4.42 29.22 (C8, 1JP,C = 48.4), 46.82
(m, 1 H, C6-H), 5.93 (s, 1 H, C4- (C6, 2JP,C = 7.3), 110.91 (C4),
H), 6.65 (s, 1 H, C5-H), 7.16–
7.27 (m, 10 H, C12–14-H)
115.66 (C5), 116.34 (C3),
122.97 (C2), 127.25 (C14),
128.14 and 128.26 (C12),
128.88 and 128.93 (C13),
137.96 and 138.0 (C11,
3JP,C = 12.9 and 11.2)
4c
1.53 and 1.54 (d, 3 H, C7-H,
6.10 (C16, 1JP,C = 51.0), 10.27
31.67
3J6,7 = 6.4), 1.70 (d, 3 H, C16-H, (C3-CH3), 11.0 (C2-CH3), 20.46
2JP,H = 13.6), 1.92 (s, 3 H, C3-
CH3), 2.17 (s, 3 H, C2-CH3),
2.61–2.95 (m, 6 H, C8,9-H),
3.16–3.47 (m, 4 H, C10-H),
and 20.55 (C9, 1JP,C = 49.7),
25.20 (C7, 3JP,C = 13.7), 29.84
(C10, 2JP,C = 5.1), 30.20 (C8,
1JP,C = 50.0), 46.91 (C6,
4.56-4.57 (m, 1 H, C6-H), 5.90 2JP,C = 9.0), 110.90 (C4), 115.63
(d, 1 H, C4-H, 3J4,5 = 2.4), 6.67 (C5), 116.27 (C3), 122.55 (C14),
(d, 1 H, C5), 7.17–7.20 (m, 2 H, 123.31 (C2), 123.84 and 123.88
C14-H), 7.38–7.41 (m, 2 H, C12- (C12), 137.50 (C13), 148.76
H), 7.64–7.68 (m, 2 H, C13-H), (C15), 157.40 and 157.52 (C11,
8.46 and 8.47 (d, 2 H, C15)
3JP,C = 8.6)
4d
1.54 (d, 3 H, C11-H,
5.94 (C19, 1JP,C = 49.9), 13.70
30.20
3J10,11 = 4.5), 1.64–1.74 (m, 4
(C2-CH3), 22.16 and 23.03 (C13,
H, C5,6-H), 1.80 (d, 3 H, C19-H, 1JP,C = 45.7 and 46.3), 23.54,
2JP,H = 13.8), 2.15 (s, 3 H, C2-
CH3), 2.20–2.40 (m, 8 H,
23.68 (C4–7), 23.61 (C11,
3JP,C = 13.6), 28.05 (C14,
C4,7,13-H), 2.50–2.75 (m, 2 H,
2JP,C = 12.9), 28.62 (C12,
C12-H), 2.80–2.95 (m, 4 H, C14- JP,C = 48.4), 46.23 (C10,
1
H), 4.50 (m, 1 H, C10-H), 5.61
(s, 1 H, C3), 6.97–7.37 (m, 10
H, C16–18-H)
2JP,C = 5.9), 107.94 (C3), 120.0
(C2), 126.22 (C8,9), 127.50 and
127.59 (C18), 128.20 and
128.43 (C16), 129.10 and
129.21 (C17), 137.93 and
138.02 (C15, 3JP,C = 12.0)
Synthesis 2005, No. 6, 965–970 © Thieme Stuttgart · New York

PAPER
Synthesis of 2-(Pyrrol-1-yl)propyldiorganylphosphines
969
Table 2 Spectral Data of Compounds 3–5a (continued)
Product
Structure
NMR, d, J (Hz)
1H
1.49 (d, 3 H, C7-H, 3J6,7 = 6.8), 9.69 (C3-CH3), 11.26 (C2-CH3), 45.06
13C
31Pb
5be
1.97 (s, 3 H, C3-CH3), 1.80–
24.65 (C7, 3JP,C = 9.9), 27.66
2.15 (m, 6 H, C8,9-H), 2.21 (s, 3 and 27.69 (C10, 2JP,C = 17.4 and
H, C2-CH3), 2.61–2.85 (m, 4 H, 17.1), 28.86 and 30.88 (C9,
1
C10-H), 4.63-4.67 (m, 1 H, C6- JP,C = 62.1 and 63.0), 36.75
H), 5.95 (d, 1 H, C4-H,
(C8, 1JP,C = 62.5), 45.67 (C6,
2JP,C = 3.9), 110.21 (C4), 113.81
(C5), 114.59 (C3), 124.50 (C2),
126.32 and 126.50 (C14),
127.94 and 128.06 (C12),
128.49 and 128.69 (C13),
140.71 and 140.75 (C11,
3JP,C = 12.8)
3J4,5 = 2.8), 6.52 (d, 1 H, C5),
7.01-7.22 (m, 10 H, C12–14
)
5ce
1.45 (d, 3 H, C7-H, 3J6,7 = 6.8), 9.30 (C3-CH3), 10.85 (C2-CH3), 45.60
1.56–1.70 (m, 4 H, C9-H), 1.88 24.10 (C7, 3JP,C = 9.4), 26.28
(s, 3 H, C3-CH3), 2.08–2.27 (m, and 28.20 (C9, 1JP,C = 63.8 and
2 H, C8-H), 2.17 (s, 3 H, C2-
64.7), 29.50 and 29.52 (C10,
CH3), 2.76-3.15 (m, 4 H, C10- 2JP,C = 24.4), 36.45 (C8,
H), 4.60-4.67 (m, 1 H, C6-H),
1JP,C = 62.6), 45.36 (C6,
5.84 (d, 1 H, C4-H, 3J4,5 = 2.4), 2JP,C = 3.9), 109.55 (C4), 113.48
6.48 (d, 1 H, C5-H), 6.96–7.28 (C5), 113.97 (C3), 121.05 and
(m, 4 H, C12,14-H), 7.50–7.53
121.19 (C14), 122.14 and
(m, 2 H, C13-H), 8.38–8.44 (m, 122.46 (C12), 124.13 (C2),
2 H, C15-H)
136.10 and 136.25 (C13),
148.66 and 148.88 (C15),
159.65 and 159.80 (C11,
3JP,C = 13.9 and 15.8)
a 1H, 13C and 31P NMR spectra were recorded on a Bruker DPX 400 spectrometer (400.13, 100.69 and 161.98 MHz, respectively) in CDCl3.
b 31P NMR for 5d: d = 49.02.
c Nonequivalence of all protons in P–C8H2 and P(C9H2)2 fragments in the 1H NMR spectrum is caused by the presence of a chiral center (C6).
Splitting of signals of CH3 groups (at C2, C3 and C6 carbon atoms) in the 13C NMR spectrum is likely to occur due to the ‘propeller’ asym-
metry of the phosphorus atom in the phosphine 3a (analogous to tribenzylamine16). The possibility of such diastereomerism is being studied.
d Splitting of signals of the atoms C2 and C10 and methyl groups attached thereto in the 13C NMR spectrum may be explained by hindered
rotation about the N–C10, C10–C12 and C12–P bonds owing to the steric effect of methyl groups at C2 and C10.
e IR spectra (Specord IR-75 spectrometer, KBr) of phosphine oxides 5b,c contain an absorption band at 1150 cm–1 (P=O).
[2-(2-Methyl-4,5,6,7-tetrahydro-1H-indol-1-yl)propyl]bis(2-
phenylethyl)phosphine (3d)
Yield: 89%; light-yellow oil.
Methyl [2-(2-Methyl-4,5,6,7-tetrahydro-1H-indol-1-yl)pro-
pyl]bis(2-phenylethyl)phosphonium Iodide (4d)
Yield: 97%; mp 180–181 °C (EtOH).
Anal. Calcd for C28H36NP: C, 80.54; H, 8.69; N, 3.35; P, 7.42.
Found: C, 80.56; H, 8.73; N, 3.49; P, 7.23.
Anal. Calcd for C29H39INP: C, 62.25; H, 7.03; I, 22.68; N, 2.50; P,
5.54. Found: C, 61.98; H, 6.86; I, 22.96; N, 2.77; P, 5.67.
[2-(1H-Indol-1-yl)propyl]bis(2-phenylethyl)phosphine (3e)
Yield: 89%; light-yellow oil.
Methyl [2-(2-Methyl-4,5,6,7-tetrahydro-1H-indol-1-yl)pro-
pyl]bis(2-phenylethyl)phosphonium Iodide (4d)
Yield: 97%; mp 180–181 °C (EtOH).
Anal. Calcd for C27H30NP: C, 81.17; H, 7.57; N, 3.51; P, 7.75.
Found: C, 81.10; H, 7.61; N, 3.68; P, 7.61.
Anal. Calcd for C29H39INP: C, 62.25; H, 7.03; I, 22.68; N, 2.50; P,
5.54. Found: C, 61.98; H, 6.86; I, 22.96; N, 2.77; P, 5.67.
Methyl [2-(2,3-Dimethyl-1H-pyrrol-1-yl)propyl]bis(2-phenyl-
ethyl)phosphonium Iodide (4b)
Yield: 97%; mp 186–188 °C (EtOH).
[2-(2,3-Dimethyl-1H-pyrrol-1-yl)propyl]bis(2-phenyleth-
yl)phosphine Oxide (5b)
Yield: 96%; light-yellow oil.
Anal. Calcd for C26H35INP: C, 60.12; H, 6.79; I, 24.43; N, 2.70; P,
5.96. Found: C, 60.35; H, 7.05; I, 24.39; N, 2.94; P, 5.68.
Anal. Calcd for C25H32NOP: C, 76.31; H, 8.20; N, 3.56; P, 7.87.
Found: C, 76.05; H, 8.00; N, 3.34; P, 7.60.
Methyl [2-(2,3-Dimethyl-1H-pyrrol-1-yl)propyl]bis[2-(2-pyrid-
inyl)ethyl]phosphonium Iodide (4c)
Yield: 97%; mp 110–111 °C (Et2O).
[2-(2,3-Dimethyl-1H-pyrrol-1-yl)propyl]bis[2-(2-pyridinyl)eth-
yl]phosphine Oxide (5c)
Yield: 96%; yellow oil.
Anal. Calcd for C24H33IN3P: C, 55.28; H, 6.38; I, 24.34; N, 8.06; P,
5.94. Found: C, 55.52; H, 6.46; I, 24.16; N, 8.17; P, 5.83.
Anal. Calcd for C23H30N3OP: C, 69.85; H, 7.65; N, 10.63; P, 7.83.
Found: C, 69.65; H, 7.55; N, 10.44; P, 7.58.
Synthesis 2005, No. 6, 965–970 © Thieme Stuttgart · New York

970
B. A. Trofimov et al.
PAPER
(8) (a) Jacobsen, E. N.; Pfaltz, A.; Yamamoto, H.
Acknowledgment
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1991, 417, 173. (c) Roucoux, A.; Suisse, I.; Devocelle, M.;
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D. J.; Slavin, M. Z.; Woollins, J. D. Chem. Commun. 2000,
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Tetrahedron Lett. 2000, 41, 5083. (f) Guo, R.; Li, X.; Wu,
J.; Kwok, W. H.; Chen, J.; Choi, M. C. K.; Chan, A. S. C.
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F. Angew. Chem. Int. Ed. 2001, 40, 680.
Financial support from the Ministry of Industry, Science and Tech-
nologies of Russian Federation (Grant No. NSH-2241.2003.3), and
from the Competition Center for Fundamental Natural Sciences
(grant No. E-02-5.0-60) is gratefully acknowledged.
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Synthesis 2005, No. 6, 965–970 © Thieme Stuttgart · New York