Synthesis of the first imidazolyl-triphosphines containing a Triphos unit

Article abstract of DOI:10.1016/j.ica.2006.07.056

Since biphasic liquid-liquid continuous-flow catalytic processes often require the use of cationic phosphine ligands for the metal sequestration in the polar phase, we have prepared the first imidazolyl triphosphines, named Triphosim and Triphosmim. These ligands contain the Triphos unit [-P(CH₂CH₂PPh₂)] which is linked to the imidazole fragment and have been obtained in three steps from imidazole (or 2-methylimidazole), diethylvinylphosphonate and diphenylvinylphosphine with global yields of 42-48%. The Triphosim ligand adopts a tridentate P-coordination mode in a palladium dichloride complex and the reaction of the dangling imidazole function with alkyl halides leads to a new kind of imidazolium-phosphine complexes.

Full text of DOI:10.1016/j.ica.2006.07.056

Inorganica Chimica Acta 360 (2007) 131–135
www.elsevier.com/locate/ica
Synthesis of the first imidazolyl-triphosphines containing a Triphos unit
*
`
Jacques Andrieu , Michele Azouri
` `
´ ´
Laboratoire de Synthese et Electrosynthese Organometalliques, UMR 5188 CNRS, Universite de Bourgogne, 9 avenue Alain Savary, 21000 Dijon, France
Received 15 June 2006; received in revised form 18 July 2006; accepted 19 July 2006
Available online 1 August 2006
Inorganic Chemistry – The Next Generation.
Abstract
Since biphasic liquid–liquid continuous-flow catalytic processes often require the use of cationic phosphine ligands for the metal
sequestration in the polar phase, we have prepared the first imidazolyl triphosphines, named Triphosim and Triphosmim. These ligands
contain the Triphos unit [-P(CH2CH2PPh2)] which is linked to the imidazole fragment and have been obtained in three steps from imid-
azole (or 2-methylimidazole), diethylvinylphosphonate and diphenylvinylphosphine with global yields of 42–48%. The Triphosim ligand
adopts a tridentate P-coordination mode in a palladium dichloride complex and the reaction of the dangling imidazole function with
alkyl halides leads to a new kind of imidazolium-phosphine complexes.
Ó 2006 Elsevier B.V. All rights reserved.
Keywords: Triphosphine; Imidazole; Imidazolium; Synthesis of polyphosphines; Tridentate ligand
1. Introduction
employed in hydroformylation of 1-octene and no Rh cata-
lyst leaching from the [BMIM](PF6) ionic phase to the
organic layer was observed [7]. In the same manner, the
presence of an imidazolium fragment on a chiral 1,4-
diphosphine has allowed the rhodium leaching in asym-
metric hydrogenation of N-acetylphenylethenamine to
decrease from 2% to less than 1 ppm [6]. On the other
hand, chelating polydentate phosphines, especially the
Triphos ligand [PhP(CH2CH2PPh2)2], offer advantages
over mono or diphosphines in homogeneous catalysis.
Indeed, the higher nucleophilic character of the metal cen-
tre due to the presence of three coordinated phosphorus
atoms (i) favours the C–H bond oxidative addition and
subsequently increases the catalytic activity of rhenium cat-
alysts in cyclooctane dehydrogenation [8] or of rhodium
catalysts in aldehydes decarbonylation [9] or (ii) increases
the reactivity of the metal-hydride bond towards the weak
polar carbonyl function of an ester [10].
The development of efficient continuous-flow catalytic
systems represents a major challenge in modern homoge-
neous catalysis. However, it requires a perfect immobilisa-
tion, or sequestration, of the catalytic species in one liquid
phase while the organic products are continuously
extracted from the catalytic medium by a mobile phase
[1,2]. For example, the association of a nonvolatile solvent
such as imidazolium salts with supercritical carbon dioxide
has given very good results in Rh catalysed olefins hydro-
formylation [3,4] or in Ni catalysed styrene hydrovinyla-
tion in continous-flow conditions [5]. Nevertheless, the
efficiency of the catalytic processes can still be increased
by introduction of a cationic imidazolium fragment on
the coordinated phosphines, which strongly decreases the
metal-phosphine leaching in the mobile phase [6]. For
example, imidazolium monophosphines salts obtained
from the neutral bis(1-imidazolylethyl)phosphines were
Imidazolyl- or imidazolium-triphosphines are thus very
appealing to perform the above catalyses in continuous-
flow conditions and we decided to investigate the elabora-
tion of a synthetic method allowing the open access to such
unprecedently described ligands, see Scheme 1.
*
Corresponding author.
E-mail address: Jacques.Andrieu@u-bourgogne.fr (J. Andrieu).
0020-1693/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2006.07.056

132
J. Andrieu, M. Azouri / Inorganica Chimica Acta 360 (2007) 131–135
O
(EtO)2P
PH2
N
N
- P'
- 2 P
N
N
N
O
(EtO)2P
N
H
N
path 1
P'
1) LiAlH4 in Et2O
reflux 18 hrs
N
N
R
R
R
P'
+ tBuOK in
N
N
N
2) Hydrolysis
path 2
P'
THF reflux 20 hrs
- 2 P
P
P
1a (R = H)
2a (R = H, 48%)
not isolated
P'
1b (R = CH3)
2b (R = CH3, 42%)
N
P
P
-
Scheme 2.
N
Scheme 1.
reaction does not lead then to free triphosphine ligand [20].
We thus applied a similar procedure to the primary phos-
phine 2b in the presence of diphenylvinylphosphine and a
t
2. Results and discussion
catalytic amount of BuOK (10 mol%) and heating under
THF or toluene reflux for 20 h. The 31P{1H} NMR spectra
of the crude product in C6D6 reveals the expected ligand 3b
with an unsatisfying conversion of 60%. Thus, an alternate
synthetic method has been attempted, based on the anti-
Markovnikov radical addition of primary phosphines to
vinyl derivatives. Indeed, the addition of phenylphosphine
to terminal fluorous olefins can be catalysed by AIBN at
about 80 °C to lead to the corresponding dialkyl-phenyl-
phosphine in good to excellent yields [21]. We used similar
conditions to achieve our transformation of ligand 2 into 3
with only 2 mol% of AIBN per mol of diphenylvinylphos-
phine, see Scheme 3.
Scheme 1 shows two possible pathways for the prepara-
tion of triphosphines bearing an imidazole moiety (or an
imidazolium group, omitted for the sake of clarity). In con-
trast to the di- or tri-phosphines which are rather difficult
to functionalise [11–13], many syntheses of polyphosphines
from monophosphines ligands are well known and some
examples are given below. Besides, in the last years, differ-
ent preparations of imidazolyl or imidazolium mono-
[7,14,15] and di-phosphines [7,15–17] have been described.
This literature examination drove us to choose path 1
(Scheme 1) to elaborate the first triphosphine imidazole
ligands.
The analysis of NMR phosphorus spectra of the crude
products obtained from 2a and 2b after reaction at 105 °C
for 20 h shows a complete and selective conversion to the
corresponding imidazolyl- and methylimidazolyl-triphos-
phine ligands 3a and 3b, which have been named, respec-
tively, Triphosim and Triphosmim (see Scheme 3) due to
their very close analogy with the Triphos ligand
[PhP(CH2CH2PPh2)2]. Their 31P{1H} NMR spectra confirm
unambiguously the formation of the two PCH2CH2P units
by the presence of a doublet at d = ꢀ0.11 ppm for the termi-
nal P in both 3a and 3b and a triplet at d = ꢀ12.63 ppm and
ꢀ12.83 ppm for the internal P of 3a and 3b, respectively,
with a 2J(P,P) coupling constant of 27 Hz.
The vinylphosphonate esters are interesting building
blocks in the synthesis of polyphosphines ligands since
the vinyl function can react with P–H bonds of primary
(or secondary) phosphines under specific conditions. More-
over, their phosphonate function can easily be reduced to
primary or secondary phosphines with LiAlH4 [18]. By
analogy with the Michael type addition, we wished to
extend the reactivity from the P–H bond to the N–H bond
of imidazoles. We have thus applied the procedure
described for the preparation of Ph2P(CH2)2PH2 (from
Ph2PH and CH2@CHP(@O)(OEt)2 [18]) to imidazole 1a
and 2-methylimidazole 1b (see Scheme 2). Both ligands
2a and 2b are obtained in good yields. The presence of
the PH2 group is confirmed by the existence of a triplet
at ꢀ136.17 and ꢀ137.60 ppm with a J(P,H) = 193 Hz,
respectively, for 2a and 2b in their phosphorus-proton cou-
pled NMR spectra.
The further addition of an equimolar amount of ligand
3a to [PdCl2(NCPh)2] leads to the air stable complex 4a
PH2
PPh2
PPh2
The above functional primary phosphines 2a and 2b are
excellent starting materials in the construction of polyphos-
phines ligands. Indeed, it was reported that the P–H bond
from aryl primary (or secondary) phosphines leads to the
PCH2CH2P unit by a base-catalysed addition to the C@C
double bond of vinylphosphines, phenyllithium and the
more efficient tBuOK [19] being the most common catalysts
to perform this reaction. It is also interesting to note that a
less basic organic catalyst like NEt3 can also be efficient in
this addition reaction, provided that the P–H bond is pre-
viously activated by a platinum coordination, although the
PPh2
P
+ 2
N
N
N
+ AIBN
2% mol
R
N
R
105˚C, 20 hrs
2a,b
3a (R = H, Triphosim)
3b (R = CH3, Triphosmim)
quantitative yield
Scheme 3.

J. Andrieu, M. Azouri / Inorganica Chimica Acta 360 (2007) 131–135
133
(see Scheme 4), which is characterised by a triplet at
d = 106.56 ppm and a doublet at d = 45.96 ppm with a
2J(P,P) = 7 Hz in a 1:2 ratio in its 31P{1H} NMR spectrum.
The phosphorus chemical shifts as well as the phosphorus-
phosphorus coupling constant of 4a are very similar to
those reported in the literature for its analogous triphos-
phine cationic complex [PdCl(Triphos)]Cl with a triplet at
d = 109.6 ppm and a doublet at d = 44.3 ppm with
2J(P,P) = 9.4 Hz [22] and are comparable to other cationic
triphosphine metal complexes like [NiCl(Triphos)]+,
[PtCl(Triphos)]+ or [Rh(CO)(Triphos)]+ [9,22,23]. More-
over, the tridentate chelating behaviour of triphosphine
has clearly been proved by X-ray structure analysis of com-
plexes [PtCl(Triphos)]Cl and [NiCl(Triphos)](BPh4) in
which the square-planar geometry around the metal centers
is slightly distorted with both P–M–P angles of 84° instead
of 90° as expected [22,23]. Therefore, ligand 3a in palla-
dium complex 4a acts as a tridentate chelating ligand with
a dangling imidazole fragment, available for a further func-
tionalisation. We have, therefore, investigated N-alkylation
reactions of 4a with different alkylating reagents and preli-
minary results are given hereafter.
our lower conversion rates could be due to the steric hin-
drance of the triphos fragment in complex 4a and/or to
the weak solubility of complex 4a in these solvents, we have
then used stronger alkylating reagents. Unfortunately, the
reaction between a solution of complex 4a in CH2Cl2 and
the methyliodide, or the Meerwein salt [(CH3)3O+,BF4ꢀ],
led to a mixture of palladium complexes which are not
yet identified. Optimisation of the N-alkylation reactions
is subsequently under investigation as, to the best of our
knowledge, complexes 5a and 6a represent the first triphos-
phine-metal compounds bearing a cationic fragment in the
ligand backbone. Such functionalisation should signifi-
cantly increase their solubility and retention in polar ionic
solvents (vs. for example scCO2) and subsequently render
this kind of complexes very promising for the biphasic
homogeneous catalyses.
3. Conclusions
We report in this paper the synthesis of the first Triphos
ligands bearing an imidazolyl moiety and the reactivity of
the related palladium complex toward different N-alkylat-
ing reagents. Since the corresponding imidazolium-triphos-
phines complexes are partially formed, their purification
and their complete characterization are currently being
investigated. However, other synthetic routes are also
being examined to avoid the use of transition metal as
phosphorus protecting group. On the other hand, we are
also examining the coordination properties of imidazo-
lium-Triphosim as a source of new tetradentate assembling
ligands as well as the potential of the N-alkylated Triphos-
mim ligands in the development of new continuous-flow
catalytic processes.
Since imidazoles can undergo a complete alkylation
reaction after 2 days of refluxing in BuCl [24], we have
applied similar conditions with complex 4a. In this case,
a conversion of only 36% is obtained which has been
increased to 76% by prolonging the heating period up to
7 days. In neat boiling EtBr, complex 4a is also partially
transformed to the related imidazolium-triphosphine com-
plex after 2 days (See Scheme 4).
Both corresponding N-alkylated products 5a and 6a
were characterized by the presence of new triplets in
the phosphorus NMR spectra recorded in CDCl3, at
102.93 ppm with 2J(P,P) = 9.3 Hz for 5a and at
2
104.83 ppm with J(P,P) = 7 Hz for 6a, and new doublets
at 45.32 ppm with 2J(P,P) = 8.5 Hz for 5a and at
4. Experimental
2
45.88 ppm with J(P,P) = 7 Hz for 6a, respectively. Since
4.1. General procedures and instrumentation
All manipulations were carried out under purified argon
using standard Schlenk techniques. All solvents were dried
and deoxygenated prior to use by standard methods. Stan-
dard pressure NMR measurements (1H, 13C{1H} and
31P{1H}) were carried out with a Bruker Avance 300 spec-
trometer at room temperature. Complete assignment was
achieved by use of DEPT and HMQC experiments. The
peak positions are reported with positive shifts in ppm
downfield of TMS as calculated from the residual solvent
peaks (1H and 13C{1H}) or downfield of external 85%
H3PO4 in water (31P). Elemental analyses were carried out
by the analytical service of the L.S.E.O. with a Fisons Instru-
ments EA1108 analyser. The commercial compounds imid-
azole 1a, 2-methylimidazole 1b, diphenylvinylphosphine,
diethyl vinylphosphonate, 1-chlorobutane, bromoethane,
-
PPh2
Cl
+
+ [PdCl2(NCPh)2]
CH2Cl2, 1 hr
Pd Cl
P
3a
N
PPh2
N
4a
+ R'X
-
PPh2
Cl
+
P
Pd Cl
N
+
PPh2
N
-
X
R'
5a (R' = Bu, X= Cl, 76% after 7 days at 80˚C)
6a (R' = Et, X= Br, 79% after 2 days at 40˚C)
t
LiAlH4, BuOK, AIBN (2,20-azobis(2-methyl-propionit-
rile)), CH3I, ½ðCH3Þ OþðBF ꢀÞꢁ and [PdCl2(NCPh)2] were
3
4
Scheme 4.
used as received.

134
J. Andrieu, M. Azouri / Inorganica Chimica Acta 360 (2007) 131–135
4.2. Syntheses of compounds
13C{1H} NMR d (C6D6, 75.47 MHz) = 139.20–118.24 (m,
12C, aromatics plus 2C from @CHN and 1C from NCHN),
43.74 (d, 1C, CH2N, 2J(P,C) = 22.6 Hz), 28.45 (d, 1C,
CH2P(CH2)2, J(P,C) = 18.9 Hz), 23.96 (t, 2C, CH2PCH2–
CH2, J(P,C) = 2J(P0,C) = 14 Hz with P and P0, respectively
for CH2P(CH2)2 and CH2PPh2, similar to Triphos ligand
[25]), 22.02 (t, 2C, CH2PPh2, J(P0,C) = 2J(P,C) = 16 Hz).
31P{1H} NMR d (C6D6, 121.49 MHz) = ꢀ0.11 (d, 2P,
J(P,P) = 26.7 Hz), ꢀ12.63 (t, 1P, J(P,P) = 26.7 Hz).
4.2.1. Synthesis of 1-(2-phosphino-ethyl)-imidazole (2a)
A mixture of imidazole (1.327 g, 19.49 mmol), diethyl
vinyl phosphonate (3.20 g, 19.49 mmol) and 30 mL of
t
THF was treated with BuOK (0.249 g, 2.21 mmol) and
heated under THF reflux for 20 h. The solvent was removed
in vacuo and the yellow residue obtained was dried for 1 h
at 70 °C. The residue was then cooled at 0 °C and 90 mL of
Et2O and LiAlH4 (1.31 g, 34.5 mmol) was rapidly added. A
strong gas evolution was immediately observed with an
increase of the temperature. When the exothermic reaction
was subsided, the mixture was boiled under Et2O reflux for
18 h. The gray suspension was cooled down to room tem-
perature and hydrolysed by 15 mL of deoxygenated water.
The organic phase was separated and the aqueous solution
was extracted twice with 25 mL of Et2O. All organic phases
were dried over K2SO4 and filtered. Evaporation of solvent
led to a colourless viscous oil which was dried for 2 h at
room temperature (1.20 g, 48%). 1H NMR d (C6D6,
300.13 MHz) = 7.22 (s, 1H, NCHN), 7.09 (s, 1H, @CHN),
6.38 (s, 1H, @CH0N), 3.12 (m, 2H, CH2N), 2.09 (dt, 2H,
PH2, J(P,H) = 193 Hz, 2J(H,H) = 4.8 Hz), 1.07 (m, 2H,
CH2P). 13C{1H} d NMR (C6D6, 75.47 MHz) = 135.69
(s, 1C, NCHN), 128.63 (s, 1C, @CHN), 116.80 (s, 1C,
@C0HN), 47.55 (s, 1C, CH2N), 14.93 (d, 1C, CH2P,
4.2.4. Synthesis of 1-{2-[bis-(2-diphenylphosphino-ethyl)-
phosphino]-ethyl}-2-methyl-imidazole (3b) (Triphosmim)
A mixture of ligand 2b (0.335 g, 2.357 mmol), diphenyl-
vinylphosphine (1.001 g, 4.712 mmol) and AIBN (15 mg,
0.091 mmol equivalent to 2% mol/mol) was heated at
105 °C for 20 h. Ligand 3b was purified by heating at
180 °C in vacuo for 2 h and obtained as a yellow waxy oil
(1.335 g, quantitative yield). 1H NMR
d
(C6D6,
300.13 MHz) = 7.51–7.10 (m, 20 H aromatics plus 1H from
@CHN), 6.50 (s, 1H, @CH0N), 3.33 (m, 2H, CH2N), 2.15 (s,
3H, CH3), 2.08 (m, 4H, CH2PPh2), 1.45 (m, 4H,
CH2P(CH2)2), 1.29 (m, 2H, CH2P(CH2)2). 13C{1H} NMR
d (C6D6, 75.47 MHz) = 143.70 (s, 1C, NCHN), 139.19–
118.35 (m, 12C, aromatics plus 2C from @CHN), 43.19
(d, 1C, CH2N, 2J(P,C) = 23.4 Hz), 28.53 (d, 1C,
CH2P(CH2)2, J(P,C) = 18.1 Hz), 24.22 (t, 2C, CH2PCH2–
CH2, J(P,C) = 2J(P0,C) = 14 Hz with P and P0, respectively
for CH2P(CH2)2 and CH2PPh2, similar to Triphos ligand
[25]), 22.46 (t, 2C, CH2PPh2, J(P’,C) = 2J(P,C) = 16 Hz),
13.19 (s, 1C, CH3). 31P{1H} NMR d (C6D6, 121.49
J(P,C) = 13.5 Hz). 31P{1H} NMR
d (C6D6, 121.49
MHz) = ꢀ136.17 (s, 1P), 31P NMR d (C6D6, 121.49
MHz) = ꢀ137.76 (t, 1P, J(P,H) = 193 Hz).
2
4.2.2. Synthesis of 2-methyl-1-(2-phosphino-ethyl)-
imidazole (2b)
MHz) = ꢀ0.11 (d, 2P, J(P,P) = 26.7 Hz), ꢀ12.83 (t, 1P,
2J(P,P) = 26.7 Hz).
Ligand 2b was prepared in an analogous manner to that
above given for 2a, starting from 2-methylimidazole 1b
(1.60 g, 19.49 mmol) and was obtained as a colourless
viscous oil (1.18 g, 42%). 1H NMR d (C6D6, 300.13
MHz) = 7.03 (s, 1H, @CHN), 6.37 (s, 1H, @CH0N), 3.12
(m, 2H, CH2N), 2.15 (dt, 2H, PH2, J(P,H) = 193 Hz,
2J(H,H) = 7.6 Hz), 1.97 (s, 3H, CH3N), 1.12 (m, 2H,
CH2P). 13C{1H} NMR d (C6D6, 75.47 MHz) = 142.35 (s,
1C, NCN), 129.97 (s, 1C, @CHN), 116.49 (s, 1C, @C0HN),
46.62 (s, 1C, CH2N), 14.46 (d, 1C, CH2P, J(P,C) =
13.6 Hz), 11.48 (s, 1C, CH3N). 31P{1H} NMR d (C6D6,
121.49 MHz) = ꢀ137.60 (s, 1P), 31P NMR d (C6D6,
121.49 MHz) = ꢀ137.60 (t, 1P, J(P,H) = 193 Hz).
4.2.5. Synthesis of Pd(II) complex (4a)
To a red suspension of [PdCl2(NCPh)2] (0.167 mg,
0.434 mmol) in 10 mL of CH2Cl2 was slowly added a solu-
tion of ligand 3a (0.240 g, 0.434 mmol) in 10 mL of
CH2Cl2. A white suspended solution was immediately
formed which became a clear yellow orange solution after
about 15 min. After stirring for 1 h, the solution was fil-
tered over Celite and the solvent was removed in vacuo.
A yellow orange powder was obtained which was washed
twice with 10 mL of Et2O and dried in vacuo at 50 °C for
2 h (0.273 g, 86%). 1H NMR
d
(CDCl3, 300.13
MHz) = 8.51–6.82 (m, 20 H aromatics plus 2H from
@CHN and @CH0N), 4.70 (m, br, 2H, CH2N), 3.26 (m,
br, 4H, CH2PPh2), 3.02 (m, br, 4H, CH2P(CH2)2), 2.13
(m, br, 2H, CH2P(CH2)2). 13C{1H} NMR d (CDCl3,
75.47 MHz) = 138.24–129.23 (m, 12C, aromatics plus 2C
from @CHN and 1C from NCHN), 44.01 (s, br, 1C,
CH2N), 29.95 (s, br, 1C, CH2P(CH2)2), 26.60 (s, br, 4C,
P(CH2)2P). 31P{1H} NMR d (CDCl3, 121.49 MHz) =
110.66 (s, br, 1P), 50.79 (s, br, 2P). 31P{1H} NMR d
(CH2Cl2/C6D6, 121.49 MHz) = 106.56 (t, 1P, 2J(P,P) =
7 Hz), 45.96 (d, 2P, 2J(P,P) = 7 Hz). C33H35N2P3PdCl2
requires: C, 54.30; H, 4.83, N 3.83. Found: C, 54.07; H,
4.97; N, 3.52%
4.2.3. Synthesis of 1-{2-[bis-(2-diphenylphosphino-ethyl)-
phosphino]-ethyl}-imidazole (3a) (Triphosim)
A mixture of ligand 2a (0.160 g, 1.249 mmol), diphenyl-
vinylphosphine (0.531 g, 2.502 mmol) and AIBN (8 mg,
0.049 mmol, 2% mol) was heated at 105 °C for 22 h. Ligand
3a was purified by heating at 180 °C in vacuo for 2 h and
obtained as a yellow waxy oil (0.691 g, quantitative yield).
1H NMR d (C6D6, 300.13 MHz) = 7.52–7.10 (m, 20 H aro-
matics plus 2H, from @CHN and NCHN), 6.47 (s, 1H,
@CH0N), 3.26 (m, 2H, CH2N), 2.05 (m, 4H, CH2PPh2),
1.41 (m, 4H, CH2P(CH2)2), 1.26 (m, 2H, CH2P(CH2)2).

J. Andrieu, M. Azouri / Inorganica Chimica Acta 360 (2007) 131–135
135
4.2.6. Synthesis of imidazolium Pd(II) salt (5a)
la Recherche Scientifique (CNRS) for financial support of
this work.
A suspension of complex 4a (46 mg, 0.063 mmol) in
20 mL of neat 1-chlorobutane was refluxed for 7 days. The
solvent was removed in vacuo and a conversion of 76%
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br, 2C, Ph2P(CH2)2), 19.51 (m, 1C, N(CH2)2CH2), 13.35
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d
(CDCl3,
2
121.49 MHz) = 102.93 (t, 1P, J(P,P) = 9.3 Hz), 45.32 (s,
br, 2P, 2J(P,P) = 9.3 Hz).
4.2.7. Synthesis of imidazolium Pd(II) salt (6a)
A suspension of complex 4a (64 mg, 0.088 mmol) in
15 mL of neat bromoethane was refluxed for 2 days. The
solvent was removed in vacuo and a conversion of 79%
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¨
was found in the NMR spectra of the crude product. H
103.
NMR d (CDCl3, 300.13 MHz) = 8.81 (s, 1H, NCHN),
7.93–7.02 (m, 20 H aromatics plus 2H from @CHN and
@CH0N), 5.16 (m, br, 2H, CH2N), 4.11 (q, 2H, NCH2CH3),
3.38 (m, br, 8H, P(CH2-CH2)2PPh2), 2.08 (m, br, 2H,
CH2P(CH2)2), 1.46 (t, 3H, NCH2CH3). 13C{1H} NMR
135.56–119.57 (m, 12C, aromatics plus 2C from @CHN
and 1C from NCHN), 44.32 (s, br, 1C, NCH2CH3), 43.02
(s, br, 1C, CH2N), 29.96 (m, br, 3C, CH2P(CH2)2), 24.56
(m, br, 2C, Ph2P(CH2)2), 14.24 (s, 1C, NCH2CH3).
31P{1H} NMR d (CDCl3, 121.49 MHz) = 104.83 (t, 1P,
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2
2J(P,P) = 7 Hz), 45.88 (s, br, 2P, J(P,P) = 7 Hz).
´
´
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´
´
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Acknowledgements
`
We are grateful to the Ministere de la Recherche for
support and for PhD fellowship to M.A. We also thank
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21 (1982) 1263.
´
the Universite de Bourgogne and the Centre National de
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