Modulating the propeller-like shape of a tripodal C(CH2PPh2)3 fragment by the size of the substituent at the pivotal carbon atom in macrobicyclic tri-λ5-phosphazenes

Article abstract of DOI:10.1016/j.tet.2007.03.076

The chiral macrobicyclic tri-λ⁵-phosphazenes formed by tripod-tripod coupling of tris(3-azidobenzyl)amines and 1,1,1-tris[(diphenylphosphino)methyl]methanes present helical topologies as a result of combining two propeller-shaped tripodal fragm

Full text of DOI:10.1016/j.tet.2007.03.076

Tetrahedron 63 (2007) 4450–4458
Modulating the propeller-like shape of a tripodal C(CH2PPh2)3
fragment by the size of the substituent at the pivotal carbon
atom in macrobicyclic tri-l5-phosphazenes
*
Mateo Alajarın, Carmen Lopez-Leonardo and Jose Berna
*
ꢀ
ꢀ
ꢀ
ꢀ
Departamento de Quꢀımica Orgaꢀnica, Facultad de Quꢀımica, Universidad de Murcia, Campus de Espinardo, E-30100 Murcia, Spain
Received 30 January 2007; revised 8 March 2007; accepted 12 March 2007
Available online 16 March 2007
Abstract—The chiral macrobicyclic tri-l5-phosphazenes formed by tripod–tripod coupling of tris(3-azidobenzyl)amines and 1,1,1-tris-
[(diphenylphosphino)methyl]methanes present helical topologies as a result of combining two propeller-shaped tripodal fragments with
the same sense of twist. The introduction of a series of Rpiv substituents of increasing size at the pivotal carbon of the lower tert-butane
fragment Rpiv–C(CH2PPh2)3 causes a gradual decrease of the helicity in the lower propeller. This phenomenon is revealed in their
CDCl3 solution NMR spectra, and the activation energies for the racemization process of the tri-l5-phosphazenes were calculated by
coalescence VT-NMR experiments.
Ó 2007 Elsevier Ltd. All rights reserved.
1. Introduction
stepwise triple extrusion of molecular nitrogen to afford tri-
l5-phosphazenes 3, which preserved the chiral, propeller-
like topology of their precursors5d,e (Fig. 1).
Macropolycyclic structures are the focus of a continuous and
intense research activity within the domain of supramolecu-
lar chemistry.1 Nevertheless, studies related to phosphorus-
containing macrobicycles have been scarce2 and most of
them have been limited to those bearing P-bridgehead
atoms.3 By contrast, the work presented here concerns about
the synthetic and structural studies of a more unusual kind of
molecular cages where the phosphorus atoms are embedded
into the arms of the macrobicycle.4
R3
R3
R5
R1
R5
R1
R4
R4
R2
X
N
N
R6
N
R6
N
N
R2
N
N
N
N
N
N
N
N
N
N
N
N
N
N
We have previously described5 the tripod–tripod coupling of
tris(2- and 3-azidobenzyl)amines with 1,1,1-tris[(diphenyl-
phosphino)methyl]ethane to give the first C3-symmetric, in-
trinsically chiral, macrobicyclic triphosphazides 1 and 2 in
racemic form by means of a Staudinger phosphane imination
reaction.6 These compounds were shown to possess propel-
ler-like topology and in all the cases studied, their molecular
self-assembly7 occurs with total stereoselectivity in favour of
the formation of the macrobicycle in which both propeller
units, the upper tribenzylamine core and the lower tert-pen-
tane fragment, present the same sense of twist. We proved
that such stereoselectivity was not influenced by thevariation
of R1–R6 substituents at the tribenzylamine fragment.5b,e The
heating of macrobicyclic cages 2 induced a remarkable
P
P
N
P
P
P
P
CH3
CH3
1 X = lp, O
R3
2
R5
R1
R4
N
R2
R6
N
N
N
N
P
P
P
CH3
= -N=N-N=P(Ph)2- or -N=P(Ph)2-
3
Keywords: Triphosphazides; Tri-l5-phosphazenes; Macrobicycles; Cage
compounds; Propellers; Tripod–tripod coupling.
* Corresponding authors. E-mail addresses: alajarin@um.es; melill@um.es
Figure 1. Structure of double propellers 1–3 and their schematic represen-
tation as viewed along their C3 axis, showing the same sense of twist of their
two pivotal subunits.
0040–4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.03.076

M. Alajarꢀın et al. / Tetrahedron 63 (2007) 4450–4458
4451
Recently we have reported8 that changing the CH3 group at
the pivotal carbon of the lower fragment by a larger Ph group
causes a considerable distortion in the optimal conformation
of that moiety by ‘pushing’ the pseudoaxial phenyls at phos-
phorus away from the sterically-demanding Ph. This defor-
mation occurs with the simultaneous decreasing of the
twisting degree of the lower propeller in both triphosph-
azides and tri-l5-phosphazenes (Fig. 2).
Table 1. Yields (%) of tris(phosphanes) 4b–f and their trichloride precursors
Rpiv
RpivC(CH2Cl)3
RpivC(CH2PPh2)3 (4)
H
459
—
4210 (4b)
4511 (4c)
6312 (4d)
71 (4e)
CH3CH2
C6H5CH2
(CH3)2CH
(CH3)3C
5312
80
85
42 (4f)
Further chloride substitution with the diphenylphosphide
anion gave rise to the tris(phosphanes) 4 (Table 1).
Ph
Ph
P
P
Ph
Ph
Ph
P
Ph
P
P
P
CH3
PPh2
PPh2
PPh2
Ph
H3C
changing CH3 by Ph
4a
OH
OH
OH
Cl
Cl
Cl
PPh2
PPh2
PPh2
i)
ii)
N
N
Rpiv
Rpiv
Rpiv
= -N=N-N=P(Ph)2- or -N=P(Ph)2-
4b Rpiv = H
Rpiv = CH3CH2
4c
4d
4e
4f
Figure 2. Two schematic representations of the deformation of the lower
propeller caused by the introduction of a pivotal Ph group.
Rpiv = C6H5CH2
Rpiv = (CH3)2CH
R
piv = (CH3)3C
Moreover, X-ray analysis of crystals of a tri-l5-phosphazene
with a pivotal Ph showed two diastereoisomeric macrobi-
cycles, one with the same sense of twist in both propellers,
upper and lower (that is, of P*,P* configuration) and the
other in which the sense of twist of the propellers is the
opposite (the P*,M* diastereoisomer)8 (Fig. 3).
Scheme 1. Synthesis of tris(phosphanes) 4. Reagents and conditions: (i)
SOCl2, pyridine, 0–115 ꢀC, 6 h; (ii) HPPh2, KOtBu, THF, reflux, 16 h.
2.2. Preparation of triphosphazides 5 and
tri-l5-phosphazenes 7
The new racemic triphosphazides 5 were obtained in moder-
ate yields by the self-assembly of triazides 6a and 6b with
tris(phosphanes) 4b, 4c, 4e, 4f (Scheme 2, Table 2). Unfor-
tunately, tris(phosphane) 4d (Rpiv¼CH2Ph) did not couple
efficiently with tris(3-azidobenzyl)amines 6 either under
standard conditions (diethyl ether, room temperature) or at
lower temperatures, these reactions always yielding unchar-
acterized oligomers. This failure may be caused either by the
thermodynamic instability of the putative triphosphazide,
bearing a benzyl group proximal to the three pseudoapical
N
N
P*,P*
P*,M*
Figure 3. Schematic representations of the two diastereoisomers present in
the crystals of a tri-l5-phosphazene obtained from PhC(CH2PPh2)3 and
a tris(3-azidobenzyl)amine.
R
These results led us to study more systematically the struc-
tural consequences of introducing substituents of different
size at the pivotal carbon of the tris(phosphane) fragment.
Here we disclose the results of such a study in which sub-
stituents of increasing size, Rpiv¼H, Me, Et, Pr, Bu, are
positioned at that carbon atom by using the corresponding
tris(phosphanes) of general formula RpivC(CH2PPh2)3 4 in
the self-assembly reactions with tris(3-azidobenzyl)amines.
R
R
PPh2
PPh2
N
i)
+
Ph2P
N3
Rpiv
i
t
N3
N3
6a R = H
6b R = Br
4
R
R
R
N
R
R
R
N
2. Results and discussion
N
N
N
N
N
N
N
N
2.1. Preparation of tris(phosphanes) 4
ii)
N
N
P
N
N
P
P
P
Tris(phosphane) 4a is commercially available. The known
tris(phosphanes) 4b–d were prepared following previously
reported procedures (see Refs. in Table 1), whereas the new
compounds 4e and 4f were prepared similarly. As outlined
in Scheme 1, their syntheses were achieved starting from
the corresponding triols, which were converted into their
respective trichlorides by reaction with thionyl chloride.
Rpiv
P
P
Rpiv
5
7
Scheme 2. Synthesis of triphosphazides 5 and tri-l5-phosphazenes 7.
Reagents and conditions: (i) Et2O, 25 ꢀC, 3 h; (ii) CDCl3, 60 ꢀC, 24 h.

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M. Alajarꢀın et al. / Tetrahedron 63 (2007) 4450–4458
Table 2. Triphosphazides 5 and tri-l5-phosphazenes 7 derived from 1,1,1-
tris(diphenylphosphanylmethyl)methanes 4b–f
5b derived from 4a (Rpiv¼CH3) is notably displaced at
higher field (d¼ꢁ0.26) in relation to the starting tris(phos-
phane) (d¼0.95).
Entry
Rpiv
R
Compound (yield %)
5
7
From the reaction of the triazide 6a and the triphosphane 4e
(Rpiv¼iPr) we could not isolate the corresponding triphos-
phazide (entry 7, Table 2) under the commonly used reaction
conditions, since, as shown by NMR, the equilibrium be-
tween reactants and product is not totally displaced to the
product side.14 However, the thermal treatment of the reac-
tion mixture in CDCl3 solution gave rise to the formation
of the tri-l5-phosphazene 7g, albeit in very low yield. By
contrast, the insolubility of the related triphosphazide 5h
(entry 8, Table 2) in diethyl ether allowed its isolation in me-
dium yield. Probably the accommodation of an isopropyl
group in the space delimited by the three pseudoaxial phenyl
rings causes a conformational variation in the lower frag-
ment such that these phenyl rings become notably deflected
from the pseudoaxial orientation, diminishing notably the
stability in solution of the expected triphosphazide. Taking
into account the results shown in entries 7 and 8, the triphos-
phane 4f, bearing a bulky tert-butyl group, was only reacted
with triazide 6b.
1
2
3
4
5
6
7
8
9
CH3
CH3
H
H
Br
H
Br
H
Br
H
5a (79)a
5b (63)a
5c (82)b
5db,c
5e (73)
5f (72)
5gb,c
7a (75)a
7b (74)a
7c (58)d
7d (63)
7e (74)
7f (81)
7g (7)
H
CH3CH2
CH3CH2
(CH3)2CH
(CH3)2CH
(CH3)3C
Br
Br
5h (56)
5i (43)
7h (72)
7i (56)
a
Compounds 5a, 5b, 7a and 7b have been described previously (Ref. 5e)
and are included here for a complete discussion of data.
The coupling reaction was carried out at 0 ꢀC.
Not isolated.
b
c
d
The extrusion of dinitrogen occurred at 25 ꢀC.
phenyl rings, or by the lower population of the optimal reac-
tive conformer of 4d for the self-assembly reaction. The tri-
pod–tripod coupling reactions were carried out under the
conditions shown in Scheme 2, except for the entries 3, 4
and 7 of Table 2, which were carried out at 0 ꢀC to obtain
the corresponding triphosphazides 5.
2.3. Conformational study of tri-l5-phosphazenes 7
In general compounds 5 were cleanly converted into the cor-
responding tri-l5-phosphazenes 7 by heating at 60 ꢀC in
CDCl3 solution, by stepwise triple extrusion of molecular ni-
trogen (Scheme 2). The dinitrogen expulsion from each PN3
unit is just the second mechanistic step of a Staudinger P(III)
imination reaction.6,13
Tri-l5-phosphazenes 7c and 7d show lower conformational
stability than the rest of the compounds 7 described in this
work. In solution at room temperature, their CH2N and
CH2P protons and the phenyl rings of their Ph2P fragments
1
do not appear as diastereotopic in their H and 13C NMR
spectra, respectively. At low temperature, in CDCl3 solution
1
at ꢁ50 ꢀC, their H NMR spectra show the splitting of the
Triphosphazides 5c and 5d (Rpiv¼H) are quite unstable, con-
verting at room temperature into the corresponding tri-l5-
phosphazenes, 7c and 7d, respectively. Such instability
may be due to the absence of CH/p interactions similar
CH2N and CH2P protons as two AB systems, indicating
that at room temperature 7c and 7d should be equilibrating
between the P,P and M,M15 enantiomeric forms. Both spec-
tra correspond to average structures of C3v symmetry, but on
cooling the interconversion becomes increasingly slower
and it is then possible to observe, in the NMR time-scale,
the signals corresponding to species of C3-symmetry.
to those contributing to the stability of the analogous Rpiv
CH3 derivatives 5a and 5b (Fig. 4), as we have previously
¼
proposed.5a,b
If these stabilizing interactions really exist they would ex-
plain why the extrusion of dinitrogen in compounds 5a or
5b requires a long thermal treatment. In contrast, their ab-
sence in 5c and 5d seems to allow their conversion into
the respective tri-l5-phosphazenes 7c and 7d under milder
conditions, at room temperature. The chemical shift of the
The analysis of the room temperature solution NMR data of
the rest of the tri-l5-phosphazenes 7 serves as the basis for
the discussion of the structural arrangement of their molec-
ular skeletons, taking the known triphosphazide 5b and tri-
l5-phosphazene 7b as reference models. To this end, we
have also related the larger or smaller shielding of the pro-
tons of the pivotal group of the rest of the macrobicyclic spe-
cies 5 and 7 with the chemical shift values of the same
1
pivotal hydrogen of 5c in its H NMR spectrum (d¼1.82),
deshielded 0.29 ppm when compared with that of the free
tris(phosphane) 4b (d¼1.53), is in accord with the absence
of shielding CH/p interactions involving that proton. In
contrast, the chemical shift of the protons of the pivotal
methyl group in the macrobicyclic triphosphazides 5a and
1
protons in the H NMR spectra of the starting tris(phos-
phanes) 4. The d values of the signals corresponding to the
protons of the pivotal group of some of the triphosphazides
5 and tri-l5-phosphazenes 7 prepared in this work, and their
precursor tris(phosphanes) 4 are shown in Table 3. The Dd
values of topologically similar hydrogens between tris(phos-
phanes) 4 and triphosphazides 5, Dd4ꢁ5, as well as between
tris(phosphanes) 4 and tri-l5-phosphazenes 7, Dd4ꢁ7, and
the differences in absolute value between these two incre-
ments, jDd7ꢁ5j, are also collected in that table.
Ph
Ph
P
P
Ph
P
Ph
Ph
P
Ph
P
P
H
H
H
H
5a,b Rpiv = CH3
5c,d Rpiv = H
The Dd value of the CH3 protons of the ethyl, isopropyl and
tert-butyl groups diminishes progressively in this order,
in both triphosphazides 5 and tri-l5-phosphazenes 7. The
Figure 4. Proposed stabilizing CH/p interactions in the lower fragment of
triphosphazides 5a and 5b but not in 5c and 5d.

M. Alajarꢀın et al. / Tetrahedron 63 (2007) 4450–4458
4453
Table 3. Selected 1H NMR data for the protons of pivotal groups in tris(phosphanes) 4, triphosphazides 5 and tri-l5-phosphazenes 7
a
a
a
Rpiv
4
d4(Rpiv
)
5
d5(Rpiv
)
7
d7(Rpiv
)
Dd4ꢁ5
Dd4ꢁ7
jDd7ꢁ5j
0.46
CH3
4a
4c
0.95b
0.50b
1.51c
5b
5f
ꢁ0.23b
7b
7f
ꢁ0.69b
1.18
1.64
CH3CH2
ꢁ0.68b
ꢁ0.79b
1.18
0.94
0.74
1.29
1.21
1.14
0.11
0.27
0.40
0.57c
0.30c
0.77c
0.37c
(CH3)2CH
4e
0.80b
5h
ꢁ0.05b
0.87d
7h
7i
ꢁ0.31b
ꢁ0.06b
1.03d
0.85
0.77
1.28
1.11
0.86
1.12
0.26
0.09
0.16
0.03b
2.15d
1.07b
(CH3)3C
4f
5i
0.36b
0.22b
0.71
0.85
0.14
a
Dd4ꢁ5¼d4(Rpiv)ꢁd5(Rpiv); Dd4ꢁ7¼d4(Rpiv)ꢁd7(Rpiv); jDd7ꢁ5j¼jd7ꢁd5j.
b
c
d
CH3.
CH2.
CH.
comparison of the Dd4ꢁ5 and Dd4ꢁ7 values for those protons
revealed that the shielding is larger in tri-l5-phosphazenes 7
than in triphosphazides 5. These data suggest that the pivotal
groups are closer to the pseudoaxial phenyl rings in com-
pounds 7 than in 5, as a consequence of the increasing rigid-
ity of the macrobicyclic skeleton after the extrusion of three
molecules of dinitrogen on passing from the triphosphazides
5 to triphosphazenes 7. This effect, in general, is attenuated
on going from ethyl to isopropyl to tert-butyl pivotal groups,
as revealed by the respective jDd7ꢁ5j values. These data are
in agreement with a gradual increment of the volume of the
cavity delimited by the three pseudoaxial phenyl groups to
accommodate a voluminous pivotal group. Such increment
results from a notable distortion of the lower fragment, grad-
ually deviating the three phenyl groups from their pseudo-
axial orientation (Fig. 5).
each pair of CH2P protons would be equivalent and should
appear as a singlet in the H NMR spectrum. Thus, we
1
have associated the higher or lower degree of magnetic in-
equivalence between the pair of protons of each CH2 group
with the corresponding degree of twist of the propeller they
belong to. The d values summarized in Table 4 reveal that
increasing the size of the pivotal group results in a gradual
reduction of the degree of twist at the lower tert-butane
propeller (Table 4, Ddlow being gradually smaller). This
loss of helicity is interpreted as a consequence of a gradual
and simultaneous rotation along the three pivotal carbon–
methylenic carbon bonds in the three arms (Fig. 6). In this
way, the pseudoaxial phenyl rings are moving gradually
towards positions more distant from the C3 pseudoaxis,
and the steric interactions between these phenyls and the
pivotal groups are alleviated. This effect is appreciable in
both the triphosphazides 5 and tri-l5-phosphazenes 7 series.
More information on how this distortion takes place can be
extracted by analyzing other NMR data such as the H
1
In contrast, the helicity of the upper tribenzylamine fragment
seems to remain approximately constant as long as the
volume of the pivotal group is increased [see Ddup values
in Table 4].
NMR chemical shifts of the CH2N and CH2P protons (Table
4). We have previously attributed the diastereotopicity of the
CH2N and CH2P protons to the propeller conformation of
the two tripodal units in macrobicycles 5 and 7, which situ-
ates each proton of these groups in a quite different chemical
environment (pseudoaxial and pseudoequatorial).5d,e In
other words, if the lower fragment is not propeller-shaped
Ph
H
Ph
Ph
Ph
H
Ph
H
H
P
H
H
Ph
Ph
P
P
Ph
Ph
P
Ph
H
H
H
H
Ph
Ph
H
P
Ph
H
H
P
H
P
H
Ph
Ph
P
Ph
Ph
P
Ph
Ph
Ph
P
P
P
Ph
R
= Phax
= Hax
R
= Rpiv of increasing size
Figure 5. Effect of the increasing size of the pivotal group on the conforma-
tion of lower fragment.
Figure 6. Structural distortion of the lower triphosphane unit of macro-
bicycles 5 and 7 by increasing the size of the pivotal group.
Table 4. Selected 1H NMR data of CH2N and CH2P protons of triphosphazides 5 and tri-l5-phosphazenes 7
Rpiv
Triphosphazides
d (CH2N)
Tri-l5-phosphazenes
d (CH2P)
d (CH2N)
d (CH2P)
a
b
a
b
Heq
Hax
Ddup
Heq
Hax
Ddlow
Heq
Hax
Ddup
Heq
Hax
Ddlow
CH3
5b
5f
5h
5i
3.83
3.74
3.65
3.58
4.05
4.00
3.87
3.86
0.22
0.26
0.22
0.28
3.52
3.71
3.87
3.84
3.86
3.84
3.87
3.93
0.34
0.13
0
7b
7f
7h
7i
3.45
3.24
3.17
2.86
3.65
3.45
3.40
3.25
0.20
0.21
0.23
0.39
3.23
3.48
3.75
4.02
3.95
4.00
4.00
3.89
0.72
0.52
0.25
ꢁ0.13
CH3CH2
(CH3)2CH
(CH3)3C
0.09
a
Ddup¼d(Hax)ꢁd(Heq) in the upper propeller.
Ddlow¼d(Hax)ꢁd(Heq) in the lower propeller.
b

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M. Alajarꢀın et al. / Tetrahedron 63 (2007) 4450–4458
1
O
High-temperature H NMR experiments demonstrated that
the inherently chiral tri-l5-phosphazenes 7 experience enan-
tioisomerization processes.1d These experiments show the
simultaneous coalescence of the CH2N and CH2P methylene
protons in the 1H NMR spectra, as well as that of the signals
corresponding to the two phenyl groups at the phosphorus
atom in the corresponding 13C{1H} NMR spectra. On cool-
ing to 25 ꢀC, these spectra recovered their original appear-
ance. The calculated activation energy for the racemization
process of compound 7b in o-Cl2C6D4 solution (DGz¼
20.8 kcal molꢁ1) was discussed in a previous communica-
tion.1d This barrier is slightly higher than those of some
tricyclic[4.4.4]propellanes16 and the 1-azonia[4.4.4]propel-
lane cation,17 and notably higher than the values found in
other bicyclic molecular propellers.18 When similar high-
temperature NMR experiments were carried out in DMSO-
d6 solution with the rest of the tri-l5-phosphazenes 7 the
calculated DGz values19 were comparable (Table 5), with
the exception of 7d which, as commented above, is less con-
formationally stable than the rest. It is remarkable that the
tri-l5-phosphazene with the highest enantioisomerization
barrier is 7b, bearing a pivotal CH3 group. This fact should
be a consequence of the special stabilization of the lower
fragment by the three stabilizing CH/p interactions be-
tween the methyl protons and the pseudoaxial P-phenyl
groups, in a similar situation to that represented in Figure 4.
O
O
8
Figure 7. A tricyclic propeller.
intermediate of C3v symmetry (with one rotation axis and
three vertical planes) whereas the involvement of, for in-
stance, a C3-symmetric species (only one rotation axis)
would render a less negative DSz value as a consequence
of a higher molecular disorder (less symmetry elements).
In contrast, a nearly zero value of DSz might be associated
with a stepwise process, arm after arm, where the entropic
variation of each step should be small. In order to determine
DSz, we carried out a line shape analysis20 of the VT-NMR
spectrum of 7b. The obtained DHz and DSz values were
11.39 kcal molꢁ1 and ꢁ24 cal Kꢁ1 molꢁ1, respectively.
The DSz is large enough to indicate that the process of enan-
tioisomerization may reasonably occur through a mechanism
like that represented in Scheme 3. This value is close to
others reported in the literature for similar processes, such
as the ꢁ16 cal Kꢁ1 molꢁ1 value of DSz corresponding to
the enantioisomerization of the P and M forms of the propel-
ler 8 (Fig. 7), which has been qualified as indicative of
a mechanism via a C3v intermediate.21
3. Conclusions
Table 5. Selected data of 1H NMR spectra of tri-l5-phosphazenes 7 at high
temperature and calculated activation energies for their enantioisomeriza-
tion processes
Tripod–tripod coupling of triphosphanes derived from the
tert-butane skeleton with tris(3-azidobenzyl)amines gave
rise to a series of chiral macrobicyclic triphosphazides,
which were converted by triple dinitrogen extrusion into
tri-l5-phosphazenes. The structure of these compounds con-
sists of two propellers linked by three P]N units. The intro-
duction of substituents of increasing size at the pivotal
carbon atom of the tris(phosphane) fragment causes a grad-
ual loss of helicity at the lower moiety of these double
propellers. These conformational changes could be followed
by examining some key 1H NMR data. The enantioisomeri-
zation barriers of the tri-l5-phosphazenes, determined by
VT-NMR experiments, show that by changing from a CH3
pivotal group to H, Et, iPr or tBu the macrobicycles become
less conformationally stable.
Compound Rpiv
J (Hz)a Dn (Hz)a Tc (K) DGz (kcal molꢁ1
)
7b
7d
7f
CH3
H
CH3CH2
12.7
12.9
14.4
51.39
51.50
19.57
66.00
117.41
408
303
363
358
408
20.17
14.79b
18.15
17.43
19.58
7h
7i
(CH3)3CH 16.0
(CH3)3C 15.9
a
Measured at the CH2N protons.
Data from experiments in CDCl3 solution.
b
We have proposed that the equilibrium, at the coalescence
temperature, between the two enantiomeric propeller-like
forms of 7 should occur via a labile conformation with
time-averaged C3v symmetry (Scheme 3).5d
4. Experimental
Ph
Ph
Ph2
P
Ph2
P
Ph
N
PPh2
N
Ph2P
Ph
N
4.1. General method
N
N
N
N
Coupling reactions were carried out under nitrogen and us-
ing solvents that were dried by routine procedures. Column
chromatography was performed with the use of silica gel
(70–200 mm) as the stationary phase. All melting points
were determined on a Kofler hot-plate melting point appara-
tus and are uncorrected. IR spectra were determined as Nujol
emulsions or films on a Nicolet Impact 400 spectrophoto-
meter. NMR spectra were recorded at 25 ꢀC on a Bruker
AC200 (200 MHz) or a Varian Unity 300 (300 MHz) spec-
trometer. 1H and 13C chemical shifts were reported in parts
per million downfield of internal tetramethylsilane (TMS)
and 31P chemical shifts were externally referenced to 85%
aqueous phosphoric acid or ammonium hydrogenphosphate.
Ph2P
PPh2
N
Ph
Ph
N
labile intermediate
of C3v symmetry
Scheme 3. Mechanism of enantioisomerization of tri-l5-triphosphazenes 7.
An alternative mechanism is also conceivable: the sequential
isomerization of the three arms, one after another, thus
involving species with a degree of symmetry, and in con-
sequence of energy, lower than that of the C3v species. In
this sense, a high negative value of DSz for the enantioisome-
rization process might support a mechanism through a labile

M. Alajarꢀın et al. / Tetrahedron 63 (2007) 4450–4458
4455
Abbreviations of coupling patterns are as follows: s, singlet;
d, doublet; t, triplet; q, quadruplet. Quaternary non-coupled
carbons are indicated by q. Mass spectra were recorded on
a Hewlett–Packard 5993C spectrometer (EI) or on a VG-
Autospec spectrometer (FAB+). Microanalyses were performed
on an EA 1108 Carlo Erba instrument.
removed under reduced pressure and the crude was chroma-
tographed (silica gel; diethyl ether/n-hexane 1:1).
4.4.1. 1,1,1-Tris(diphenylphosphanylmethyl)-2-methyl-
propane (4e). Yield: 71%; white oil; H NMR (300 MHz,
1
CDCl3): d¼0.80 (d, J(H,H)¼6.8 Hz, 6H; CH3), 2.15 (sept,
J(H,H)¼6.8 Hz, 1H; CH), 2.41 (br s, 6H; CH2), 7.20–7.30
(m, 30H; PhP); 13C{1H} NMR (75.4 MHz, CDCl3):
d¼18.59 (CH3), 36.56 (CH), 38.75 (m; CH2P), 44.32 [q,
2J(C,P)¼10.5 Hz; C(CH2PPh2)3], 128.04–128.30 (m; mC-
PhP+pC-PhP), 133.56 (d, 2J(C,P)¼19.9 Hz; oC-PhP),
4.2. Materials
Compounds 1,1,1-tris(diphenylphosphinomethyl)methane,9,10
1,1,1-tris(diphenylphosphinomethyl)propane,11 1,1,1-tris(di-
phenylphosphinomethyl)-2-phenylethane12 were prepared
following previously reported procedures.
1
140.32 (d, J(C,P)¼9.0 Hz; iC-PhP); IR (film): n¼2989,
1479, 1386, 1110, 1031, 745, 696 cmꢁ1; MS (70 eV, EI):
m/z (%)¼652 (14) [M+], 574 (96), 390 (99), 262 (62), 183
(100); C43H43P3 (652.72): calcd C 79.12, H 6.64; found C
79.03, H 6.54.
4.3. General procedure for the preparation of
trichlorides RpivC(CH2Cl)3
A solution of the corresponding 2-substituted 2-hydroxy-
methyl-1,3-propanediol (13.5 mmol) in pyridine (3 mL)
and thionyl chloride (5.06 g, 42.6 mmol) were simulta-
neously added dropwise to an ice-cooled round-bottom flask
containing pyridine (5 mL). When the addition was over, the
resultant mixture was allowed to warm to room temperature
(around 1 h) with stirring. Then it was heated at 50 ꢀC for 1 h
and at 115 ꢀC for 4 h more. After cooling to room tempera-
ture, the mixture was poured on ice/H2O and extracted with
CH2Cl2 (3ꢂ25 mL). The organic extracts were combined
and dried over anhydrous MgSO4. The solvent was removed
under reduced pressure, and the resulting material was chro-
matographed (silica gel; dichloromethane/n-hexane 1:1).
4.4.2. 1,1,1-Tris(diphenylphosphanylmethyl)-2,2-di-
methylpropane (4f). Yield: 42%; mp 152–154 ꢀC (colourless
prisms from chloroform/n-pentane); 1H NMR (300 MHz,
CDCl3): d¼1.07 (s, 9H; CH3), 2.45 (d, 2J(H,P)¼2.1 Hz, 6H;
CH2), 7.18–7.27 (m, 30H; PhP); 13C{1H} NMR (75.4 MHz,
CDCl3): d¼28.41 (q, 4J(C,P)¼5.0 Hz; CH3), 38.27
[C(CH3)3], 39.07 (m; CH2P), 47.68 [q, 2J(C,P)¼9.3 Hz;
C(CH2PPh2)3], 128.24 (pC-PhP), 128.32 (d, 3J(C,P)¼
7.0 Hz; mC-PhP), 133.11 (d, 2J(C,P)¼20.3 Hz; oC-PhP),
1465, 1378, 1093, 1025, 968, 736 cmꢁ1; MS (70 eV, EI):
m/z (%)¼666 (26) [M+], 586 (82), 404 (85), 389 (99), 262
(83), 181 (99), 106 (100); C44H45P3 (666.75): calcd C
79.26, H 6.80; found C 79.17, H 6.53.
1
140.39 (d, J(C,P)¼13.2 Hz; iC-PhP); IR (film): n¼2852,
4.3.1. 1-Chloro-2,2-bis(chloromethyl)-3-methylbutane
(Rpiv=iPr). Yield: 80%; colourless oil; 1H NMR
(300 MHz, CDCl3): d¼1.09 (d, J(H,H)¼7.1 Hz, 6H; CH3),
2.06 (sept, J(H,H)¼7.1 Hz, 1H; CH), 3.61 (s, 6H; CH2);
13C{1H} NMR (75.4 MHz, CDCl3): d¼17.75 (CH3), 30.77
(CH), 45.17 (q), 46.15 (CH2); IR (film): n¼2972, 1476,
1441, 843, 739, 705 cmꢁ1; MS (70 eV, EI): m/z (%)¼204
(8) [M++2], 202 (15) [M+], 124 (100); C7H13Cl3 (203.54):
calcd C 41.31, H 6.44; found C 41.19, H 6.40.
4.5. General procedure for the preparation of the
triphosphazides 5
Two solutions of the corresponding tris(3-azidobenzyl)-
amine 6 (1.5 mmol) in diethyl ether (10 mL) and the corre-
sponding triphosphane 4 in diethyl ether (10 mL) were
simultaneously added dropwise to a round-bottom flask
containing diethyl ether (15 mL) under nitrogen atmosphere
at room temperature over a period of 30 min with stirring.
The resulting mixture was then stirred for 3 h. The precipi-
tated pale yellow solid was filtered, washed with diethyl
ether (3ꢂ10 mL) and dried under vacuum.
4.3.2. 1-Chloro-2,2-bis(chloromethyl)-3,3-dimethyl-
1
butane (Rpiv=tBu). Yield: 85%; colourless oil; H NMR
(300 MHz, CDCl3): d¼1.19 (s, 9H; CH3), 3.81 (s, 6H; CH2);
13C{1H} NMR (75.4 MHz, CDCl3): d¼28.14 (CH3), 36.66
[C(CH3)3], 46.17 [C(CH2Cl)3], 47.21 (CH2); IR (film):
n¼2967, 1482, 1443, 965, 864 cmꢁ1; MS (70 eV, EI): m/z
(%)¼218 (6) [M++2], 216 (10) [M+], 124 (100); C8H15Cl3
(217.56): calcd C 44.16, H 6.95; found C 44.02, H 6.88.
4.5.1. Triphosphazide 5c. Yield: 82%; mp (decomp.) 306–
307 ꢀC (microcrystalline solid from diethyl ether); 1H
NMR (300 MHz, CDCl3): d¼1.82 (br s, 1H; CH), 3.39–
3.63 (m, 12H; CH2N+CH2P), 7.00 (d, J(H,H)¼7.4 Hz, 3H;
Harom), 7.27 (d, J(H,H)¼7.6 Hz, 3H; Harom), 7.15–7.50 (m,
24H; Harom), 7.56 (br d, J(H,H)¼8.1 Hz, 3H; Harom), 7.64
(dd, 6H, J(H,H),(H,P)¼10.2, 8.1 Hz; Harom), 7.76 (br s, 3H;
Harom); 13C{1H} NMR (75.4 MHz, CDCl3): d¼26.62 (br s;
CH), 31.90 (m; CH2P), 58.11 (CH2N), 118.61 (br s), 120.80
(br s), 124.20 (d, 1J(C,P)¼110.3 Hz; iC-PhP), 126.63,
4.4. General procedure for the preparation of
2-substituted 1,1,1-tris(diphenylphosphanyl-
methyl)propanes (4)
Diphenylphosphane (3 g, 16.5 mmol) was added to a suspen-
sion of potassium tert-butoxide (2.25 g, 20 mmol) in dry
THF (25 mL). The mixture was stirred for 15 min and a solu-
tion of the corresponding trichloride (5 mmol) in dry THF
(10 mL) was added at once. The reaction mixture was heated
at reflux temperature for 16 h. After cooling to room temper-
ature, H2O (75 mL) was added and the product was extracted
with CH2Cl2 (3ꢂ25 mL). The organic extracts were com-
bined and dried over anhydrous MgSO4. The solvent was
3
128.42, 128.90 (d, J(C,P)¼11.6 Hz; mC-PhP), 129.06 (d,
1
3J(C,P)¼12.1 Hz; mC-PhP), 129.25 (d, J(C,P)¼84.6 Hz;
iC-PhP), 130.91 (d, 2J(C,P)¼9.6 Hz; oC-PhP), 131.20
4
2
(d, J(C,P)¼2.0 Hz; pC-PhP), 132.17 (d, J(C,P)¼8.1 Hz;
4
oC-PhP), 132.20 (d, J(C,P)¼1.1 Hz; pC-PhP), 141.19 (q),
150.99 (q); 31P{1H} NMR (121.4 MHz, CDCl3): d¼18.20
(br s, Dn ¼303 Hz); IR (Nujol): n¼1467 (CP), 1113
½
(NP) cmꢁ1; MS (FAB+): m/z (%) 1044 (14) [M++Na], 1021

4456
M. Alajarꢀın et al. / Tetrahedron 63 (2007) 4450–4458
(6) [M+], 624 (100); C61H55N10P3 (1021.08): calcd C 71.75,
H 5.43, N 13.72; found C 71.72, H 5.56, N 13.70.
120.83 (br s), 128.43 (d, 1J(C,P)¼106.7 Hz; iC-PhP),
128.59 (br d, 3J(C,P)¼11.6 Hz; 2 mC-PhP), 129.69 (d,
1J(C,P)¼84.3 Hz; iC-PhP), 130.68 (d, 2J(C,P)¼9.1 Hz;
oC-PhP), 131.34 (br s; pC-PhP), 132.24 (br s; pC-PhP),
4.5.2. Triphosphazide 5e. Yield: 73%; mp 309–311 ꢀC (yel-
low prisms from dichloromethane/diethyl ether); H NMR
1
2
133.27, 133.35 (d, J(C,P)¼8.3 Hz; oC-PhP), 139.33 (q),
(300 MHz, CDCl3): d¼ꢁ0.60 (pseudot, J(H,H)¼6.8 Hz,
3H; CH3), 0.55 (pseudoq, J(H,H)¼7.7 Hz, 1H; CH3CHAHB),
0.70 (pseudoq, J(H,H)¼7.7 Hz, 1H; CH3CHAHB), 3.56 (d,
J(H,H)¼14.7 Hz, 3H; CHAHBN), 3.78–3.94 (m, 9H;
CHAHBN+CHAHBP+CHAHBP), 6.85–7.00 (m, 9H; Harom),
7.13 (t, J(H,H)¼7.1 Hz, 3H; Harom), 7.26 (t, J(H,H)¼7.6 Hz,
3H; Harom), 7.30–7.45 (m, 15H; Harom), 7.57 (d, J(H,H)¼
8.1 Hz, 3H; Harom), 8.00–8.10 (m, 9H; Harom); 13C{1H}
NMR (75.4 MHz, CDCl3): d¼9.21 (CH3CH2), 31.38
(CH3CH2), 39.72 (m; CH2P), 45.97 (q, 2J(C,P)¼3.5 Hz;
CH3CH2C), 57.16 (CH2N), 119.71 (br s, two signals),
149.25 (q); 31P{1H} NMR (121.4 MHz, CDCl3): d¼6.46
(br s, Dn ¼447 Hz); IR (Nujol): n¼1463 (CP), 1112
½
(NP) cmꢁ1; MS (FAB+): m/z (%) 1301 (11) [M++5], 1299
(13) [M++3], 666 (100); C64H58Br3N10P3 (1299.85): calcd
C 59.14, H 4.50, N 10.78; found C 58.99, H 4.43, N 10.69.
4.5.5. Triphosphazide 5i. Yield: 43%; mp 297–299 ꢀC (yel-
low prisms from dichloromethane/diethyl ether); H NMR
1
(300 MHz, CDCl3): d¼0.36 (br s, 9H; CH3), 3.58 (d, J(H,H)¼
16.4 Hz, 3H; CHAHBN), 3.84 (pseudoquint, J(H,H),(H,P)¼
12.0 Hz, 3H; CHAHBP), 3.86 (d, J(H,H)¼16.4 Hz, 3H;
CHAHBN), 3.93 (pseudot, J(H,H),(H,P)¼15.9 Hz, 3H;
CHAHBP), 6.65–6.72 (m, 6H; Harom), 7.22–7.50 (m, 24H;
Harom), 8.01–8.08 (m, 6H; Harom), 8.12 (br s, 3H; Harom);
13C{1H} NMR (75.4 MHz, CDCl3): d¼29.07 [(CH3)3C],
34.14 [(CH3)3C], 37.80 (m; CH2P), 57.92 [q, 2J(C,P)¼
3.0 Hz, (CH3)3CC], 58.15 (CH2N), 117.50 (br s), 119.49
1
125.55, 127.35 (d, J(C,P)¼94.0 Hz; iC-PhP), 128.56 (d,
3J(C,P)¼11.0 Hz; mC-PhP), 128.59, 128.61(d, 3J(C,P)¼
1
10.5 Hz; mC-PhP), 129.92 (d, J(C,P)¼84.1 Hz; iC-PhP),
131.09 (d, 2J(C,P)¼8.7 Hz; oC-PhP), 131.25 (br s;
pC-PhP), 132.18 (br s; pC-PhP), 132.99 (d, 2J(C,P)¼
7.0 Hz; oC-PhP), 141.49 (q), 150.24 (q); 31P{1H} NMR
3
(121.4 MHz, CDCl3): d¼5.80 (br s, Dn ¼1210 Hz); IR (Nu-
(q), 123.04 (br s), 128.12 (d, J(C,P)¼11.7 Hz; mC-PhP),
½
jol): n¼1440 (CP), 1109 (NP) cmꢁ1; MS (FAB+): m/z (%)
1072 (16) [M++Na], 1049 (12) [M+], 653 (100);
C63H59N10P3 (1049.13): calcd C 72.12, H 5.67, N 13.35;
found C 71.98, H 5.81, N 13.37.
128.30 (d, 3J(C,P)¼11.2 Hz; mC-PhP), 128.80 (d, 1J(C,P)¼
2
105.6 Hz; iC-PhP), 130.40 (d, J(C,P)¼9.0 Hz; oC-PhP),
130.67 (d, 1J(C,P)¼82.6 Hz; iC-PhP), 130.75 (br s;
pC-PhP), 131.79 (br s; pC-PhP), 133.10, 134.14 (d,
2J(C,P)¼7.3 Hz; oC-PhP), 139.31 (q), 148.83 (q); 31P{1H}
4.5.3. Triphosphazide 5f. Yield: 72%; mp 312–314 ꢀC (yel-
low prisms from chloroform); 1H NMR (300 MHz, CDCl3):
d¼ꢁ0.68 (pseudot, J(H,H)¼7.3 Hz, 3H; CH3), 0.57 (pseu-
doq, J(H,H)¼7.6 Hz, 1H; CH3CHAHB), 0.77 (pseudoq,
J(H,H)¼7.6 Hz, 1H; CH3CHAHB), 3.71 (m, 3H; CHAHBP),
3.74 (d, J(H,H)¼16.8 Hz, 3H; CHAHBN), 3.84 (pseudot,
J(H,H),(H,P)¼15.0 Hz, 3H; CHAHBP), 4.00 (d, J(H,H)¼
16.8 Hz, 3H; CHAHBN), 6.89–6.93 (m, 6H; Harom), 7.16–
7.28 (m, 9H; Harom), 7.37–7.44 (m, 15H; Harom), 8.05–8.07
(m, 6H; Harom), 8.18 (br s, 3H; Harom); 13C{1H} NMR
(75.4 MHz, CDCl3): d¼8.87 (CH3CH2), 31.22 (CH3CH2),
NMR (121.4 MHz, CDCl3): d¼7.00 (br s, Dn ¼242 Hz);
½
IR (Nujol): n¼1462 (CP), 1115 (NP) cmꢁ1; MS (FAB+):
m/z (%) 1314 (12) [M++4], 1312 (15) [M++2], 1310 (7)
[M+], 684 (100); C65H60Br3N10P3 (1313.87): calcd C
59.42, H 4.60, N 10.66; found C 59.30, H 4.52, N 10.45.
4.6. General procedure for the preparation of the
tri-l5-phosphazenes 7
A solution of the corresponding triphosphazide 5 (1 mmol)
in CDCl3 (10 mL) was heated at 60 ꢀC in an oil bath for
24 h. After cooling, the solvent was removed under reduced
pressure and the crude product was crystallized.
2
39.52 (m; CH2P), 46.18 (q, J(C,P)¼3.0 Hz; CH3CH2C),
58.19 (CH2N), 117.52 (br s), 119.70 (q), 120.65 (br s),
127.25 (dright; iC-PhP), 128.53 (d, J(C,P)¼12.2 Hz; mC-
3
3
PhP), 128.60 (d, J(C,P)¼11.0 Hz; mC-PhP), 129.54 (dleft
;
4.6.1. Tri-l5-phosphazene 7c. Yield: 58%; mp 210–212 ꢀC
(colourless prisms from chloroform/n-hexane); 1H NMR
(300 MHz, CDCl3): d¼1.16 (br s, 1H; CH), 3.39 (br s, 6H;
CH2P), 3.40 (br s, 6H; CH2N), 6.26 (s, 3H; Harom), 6.59
(d, J(H,H)¼7.2 Hz, 3H; Harom), 6.97 (d, J(H,H)¼7.8 Hz,
3H; Harom), 7.08 (dt, J(H,H),(H,P)¼8.1, 2.2 Hz, 3H; Harom),
7.10–7.45 (m, 30H; Harom); 13C{1H} NMR (75.4 MHz,
iC-PhP), 130.80 (d, 2J(C,P)¼9.3 Hz; oC-PhP), 131.40 (br s;
pC-PhP), 132.13 (br s; pC-PhP), 132.74 (d, 2J(C,P)¼7.0 Hz;
oC-PhP), 133.24, 139.32 (q), 149.22 (q); 31P{1H} NMR
(121.4 MHz, CDCl3): d¼4.76 (br s, Dn ¼484 Hz); IR (Nu-
½
jol): n¼1462 (CP), 1114 (NP) cmꢁ1; MS (FAB+): m/z (%)
1284 (7) [M++2], 655 (100); C63H56Br3N10P3 (1285.82):
calcd C 58.85, H 4.39, N 10.89; found C 58.94, H 4.48, N
10.87.
1
CDCl3): d¼26.17 (br s; CH), 27.05 (dt, J(C,P)¼46.6 Hz,
3J(C,P)¼8.0 Hz; CH2P), 58.03 (CH2N), 118.69, 123.20
(d, 3J(C,P)¼11.1 Hz; s-cis-CH]C–N]P), 124.87 (d,
3J(C,P)¼27.7 Hz; s-trans-CH]C–N]P), 128.41, 128.56
(br s; mC-PhP), 130.92 (br s; pC-PhP), 131.29 (br s; pC-
PhP), 142.04 (q), 151.52 (q), the resonance of the iC-PhP
was not observed; 31P{1H} NMR (121.4 MHz, CDCl3):
d¼1.11; IR (Nujol): n¼1465 (CP), 1115 (NP) cmꢁ1; MS
(FAB+): m/z (%)¼938 (55) [M++1], 937 (100) [M+], 936
(64) [M+ꢁ1]; C61H55N4P3 (937.04): calcd C 78.19, H
5.92, N 5.98; found C 78.05, H 5.79, N 5.87.
4.5.4. Triphosphazide 5h. Yield: 56%; mp (decomp.) 301–
303 ꢀC (yellow prisms from dichloromethane/diethyl ether);
1H NMR (300 MHz, CDCl3): d¼ꢁ0.05 [d, J(H,H)¼6.3 Hz,
3H; (CH3)A], 0.03 [d, J(H,H)¼6.0 Hz, 3H; (CH3)B], 0.87 (m,
1H; CH), 3.65 (d, J(H,H)¼16.5 Hz, 3H; CHAHBN), 3.77–
3.96 (m, 9H; CHAHBN+CH2P), 6.81–6.85 (m, 6H; Harom),
7.13–7.15 (m, 3H; Harom), 7.30–7.46 (m, 21H; Harom),
8.06–8.15 (m, 9H; Harom); 13C{1H} NMR (75.4 MHz,
CDCl3): d¼19.89 [(CH3)A], 20.48 [(CH3)B], 33.21
2
[(CH3)2CH], 37.82 (m; CH2P), 51.84 [q, J(C,P)¼3.4 Hz;
4.6.2. Tri-l5-phosphazene 7d. Yield: 63%; mp 171–173 ꢀC
(colourless prisms from chloroform); H NMR (300 MHz,
1
(CH3)2CHC], 58.15 (CH2N), 117.80 (br s), 119.88 (q),

M. Alajarꢀın et al. / Tetrahedron 63 (2007) 4450–4458
4457
CDCl3, 25 ꢀC): d¼1.48 (br s, 1H; CH), 3.33 (br s, 6H;
CH2P), 3.69 (br s, 6H; CH2N), 6.47 (d, J(H,H)¼2.7 Hz,
3H; Harom), 6.84 (dd, J(H,H)¼8.7, 3.0 Hz, 3H; Harom),
CH]C–N]P), 126.88 (d, 3J(C,P)¼27.8 Hz; s-trans-
CH]C–N]P), 128.48 (d, 3J(C,P)¼12.8 Hz; mC-PhP),
3
128.82 (d, J(C,P)¼11.0 Hz; mC-PhP), 130.80 (dright; iC-
1
2
7.23–7.52 (m, 33H; Harom); H NMR (300 MHz, CDCl3,
PhP), 131.00 (d, J(C,P)¼8.7 Hz; oC-PhP), 131.25 (br s;
60 ꢀC): d¼1.30 (pseudoq, J(H,H),(H,P)¼8.4 Hz, 1H; CH),
3.32 (br s, 6H; CH2P), 3.70 (s, 6H; CH2N), 6.49 (d,
J(H,H)¼2.7 Hz, 3H; Harom), 6.82 (dd, J¼8.7, 3.0 Hz,
3H; Harom), 7.23–7.44 (m, 33H; Harom); 13C{1H} NMR
pC-PhP), 131.57 (br s; pC-PhP), 131.92 (d, 2J(C,P)¼9.3 Hz;
oC-PhP), 132.86, 138.97 (q), 150.98 (q), the resonance of one
iC-PhP was not observed; 31P{1H} NMR (121.4 MHz,
CDCl3): d¼0.63; IR (Nujol): n¼1440 (CP), 1119 (NP) cmꢁ1
;
2
(75.4 MHz, CDCl3, 60 ꢀC): d¼26.18 (q, J(C,P)¼2.5 Hz;
MS (FAB+): m/z(%)¼1202 (95) [M++4], 1200 (100) [M++2],
1198 (31) [M+]; C63H56Br3N4P3 (1201.78): calcd C 62.96, H
4.70, N 4.66; found C 62.85, H 4.64, N 4.60.
1
3
CH), 28.12 (dt, J(C,P)¼46.4 Hz, J(C,P)¼8.2 Hz; CH2P),
56.96 (CH2N), 111.74 (q), 124.73 (d, 3J(C,P)¼10.4 Hz;
3
s-cis-CH]C–N]P), 126.86 (d, J(C,P)¼27.8 Hz; s-trans-
CH]C–N]P), 128.74 (d, 3J(C,P)¼12.2 Hz; mC-PhP),
4.6.5. Tri-l5-phosphazene 7g. Yield: 7%; mp 258–260 ꢀC
(colourless prisms from dichloromethane/diethyl ether); 1H
NMR (300 MHz, CDCl3): d¼ꢁ0.41 [d, J(H,H)¼7.0 Hz,
3H; (CH3)A], ꢁ0.21 [d, J(H,H)¼6.8 Hz, 3H; (CH3)B], 0.96
(m, 1H; CH), 2.81 (d, J(H,H)¼12.4 Hz, 3H; CHAHBN),
3.34 (d, J(H,H)¼12.4 Hz, 3H; CHAHBN), 3.66 (pseudoquint,
J(H,H),(H,P)¼7.6 Hz, 3H; CHAHBP), 3.94 (pseudot,
J(H,H),(H,P)¼15.9 Hz, 3H; CHAHBP), 6.37 (d, J(H,H)¼
7.0 Hz, 3H; Harom), 6.40 (br s, 3H; Harom), 7.02 (dt, J(H,H)¼
7.2, 1.8 Hz, 3H; Harom), 7.12 (d, J(H,H)¼6.9 Hz, 3H; Harom),
7.34–7.39 (m, 15H; Harom), 7.46–7.56 (m, 9H; Harom), 7.98–
8.03 (m, 6H; Harom); 13C{1H} NMR (75.4 MHz, CDCl3):
d¼19.53 [(CH3)A], 20.11 [(CH3)B], 35.48 [(CH3)2CH],
36.75 (dd, 1J(C,P)¼45.8 Hz, 3J(C,P)¼12.2 Hz; CH2P),
50.12 [q, 2J(C,P)¼3.1 Hz; (CH3)2CHC], 57.42 (CH2N),
2
4
131.05 (d, J(C,P)¼9.3 Hz; oC-PhP), 131.50 (d, J(C,P)¼
4
2.3 Hz; pC-PhP), 132.68 (d, J(C,P)¼4.1 Hz), 140.07 (q),
150.99 (q), the resonance of the iC-PhP was not observed;
31P{1H} NMR (121.4 MHz, CDCl3): d¼2.68; IR (Nujol):
n¼1474 (CP), 1116 (NP) cmꢁ1; MS (FAB+): m/z (%)¼
1175 (45) [M++5], 1173 (89) [M++3], 1171 (100) [M++1];
C61H52Br3N4P3 (1173.73): calcd C 62.42, H 4.47, N 4.77;
found C 62.34, H 4.38, N 4.81.
4.6.3. Tri-l5-phosphazene 7e. Yield: 74%; mp 321–323 ꢀC
(yellow prisms from chloroform/diethyl ether); H NMR
1
(300 MHz, CDCl3): d¼ꢁ0.92 (pseudot, J(H,H)¼7.3 Hz,
3H; CH3), 0.18 (pseudoq, J(H,H)¼7.3 Hz, 1H; CH3CHAHB),
0.32 (pseudoq, J(H,H)¼7.3 Hz, 1H; CH3CHAHB), 2.86 (d,
J(H,H)¼12.3 Hz, 3H; CHAHBN), 3.41 (pseudoquint,
J(H,H),(H,P)¼8.1 Hz, 3H; CHAHBP), 3.45 (d, J(H,H)¼
12.3 Hz, 3H; CHAHBN), 3.97 (pseudot, J(H,H),(H,P)¼
15.2 Hz, 3H; CHAHBP), 6.36–6.38 (m, 3H; HAr), 6.47 (d,
J(H,H)¼6.8 Hz, 3H; Harom), 7.00–7.60 (m, 30H; Harom),
7.90–7.96 (m, 6H; Harom); 13C{1H} NMR (75.4 MHz,
CDCl3): d¼8.98 (CH3CH2), 33.48 (CH3CH2), 36.98 (m;
CH2P), 44.53 (q, 2J(C,P)¼3.5 Hz; CH3CH2C), 57.56
(CH2N), 118.40, 122.64 (d, 3J(C,P)¼12.7 Hz; s-cis-
CH]C–N]P), 125.41 (d, 3J(C,P)¼27.8 Hz; s-trans-
CH]C–N]P), 128.22 (d, 4J(C,P)¼4.0 Hz), 128.36 (d,
3
118.14, 122.75 (d, J(C,P)¼12.8 Hz; s-cis-CH]C–N]P),
125.49 (d, 3J(C,P)¼27.8 Hz; s-trans-CH]C–N]P),
3
128.21, 128.30 (d, J(C,P)¼13.3 Hz; mC-PhP), 128.71 (d,
3J(C,P)¼11.0 Hz; mC-PhP), 130.69 (br s; pC-PhP), 131.10
(d, 1J(C,P)¼90.7 Hz; iC-PhP), 131.28 (br s; pC-PhP),
2
2
131.63 (d, J(C,P)¼8.7 Hz; oC-PhP), 132.45 (d, J(C,P)¼
1
9.3 Hz; oC-PhP), 132.80 (d, J(C,P)¼105.1 Hz; iC-PhP),
141.63 (q), 151.33 (q); 31P{1H} NMR (121.4 MHz,
CDCl3): d¼3.50; IR (Nujol): n¼1459 (CP), 1109 (NP) cmꢁ1
;
MS (FAB+): m/z (%)¼979 (100) [M+]; C64H61N4P3 (979.12):
calcd C 78.51, H 6.28, N 5.72; found C 78.38, H 6.15, N 5.61.
3
3J(C,P)¼12.8 Hz; mC-PhP), 128.70 (d, J(C,P)¼11.0 Hz;
4
mC-PhP), 130.94 (d, J(C,P)¼1.2 Hz; pC-PhP), 131.41 (d,
4.6.6. Tri-l5-phosphazene 7h. Yield: 72%; mp (decomp.)
328–330 ꢀC (colourless prisms from chloroform/diethyl
ether); 1H NMR (300 MHz, CDCl3): d¼ꢁ0.31 [d,
J(H,H)¼7.1 Hz, 3H; (CH3)A], ꢁ0.06 [d, J(H,H)¼7.0 Hz,
3H; (CH3)B], 1.03 (m, 1H; CH), 3.17 (d, J(H,H)¼16.0 Hz,
3H; CHAHBN), 3.40 (d, J(H,H)¼16.0 Hz, 3H; CHAHBN),
3.75 (pseudoquint, J(H,H),(H,P)¼7.7 Hz, 3H; CHAHBP),
4.00 (pseudot, J(H,H),(H,P)¼16.3 Hz, 3H; CHAHBP), 6.83
(d, J(H,H)¼2.4 Hz, 3H; Harom), 6.97 (dd, J(H,H)¼8.7,
2.4 Hz, 3H; Harom), 7.12 (dt, J(H,H)¼7.6, 2.9 Hz, 6H;
Harom), 7.20 (dd, J(H,H)¼8.4, 1.8 Hz, 3H; Harom), 7.24–
7.33 (m, 9H; Harom), 7.38–7.41 (m, 9H; Harom), 7.98–8.04
(m, 6H; Harom); 13C{1H} NMR (75.4 MHz, CDCl3):
d¼19.66 [(CH3)A], 19.84 [(CH3)B], 35.58 [(CH3)2CH],
2
4J(C,P)¼1.0 Hz; pC-PhP), 131.61 (d, J(C,P)¼8.7 Hz; oC-
PhP), 131.86 (d, 1J(C,P)¼91.5 Hz; iC-PhP), 132.23 (d,
2J(C,P)¼9.3 Hz; oC-PhP), 132.51 (d, 1J(C,P)¼88.9 Hz; iC-
PhP), 141.80 (q), 151.24 (q); 31P{1H} NMR (121.4 MHz,
CDCl3): d¼2.17; IR (Nujol): n¼1451 (CP), 1117 (NP) cmꢁ1
;
MS (FAB+): m/z (%)¼988 (12) [M++Na], 966 (100) [M++1];
C63H59N4P3 (965.09): calcd C 78.40, H 6.16, N 5.81; found C
78.29, H 6.11, N 5.92.
4.6.4. Tri-l5-phosphazene 7f. Yield: 81%; mp (decomp.)
348–350 ꢀC (yellow prisms from dichloromethane/diethyl
1
ether); H NMR (300 MHz, CDCl3): d¼ꢁ0.79 (pseudot,
J(H,H)¼7.4 Hz, 3H; CH3), 0.30 (pseudoq, J(H,H)¼7.4 Hz,
1H; CH3CHAHB), 0.37 (pseudoq, J(H,H)¼7.4 Hz, 1H;
CH3CHAHB), 3.24 (d, J(H,H)¼14.4 Hz, 3H; CHAHBN),
3.45 (d, J(H,H)¼14.4 Hz, 3H; CHAHBN), 3.48 (m, 3H;
CHAHBP), 4.00 (pseudot, J(H,H),(H,P)¼15.3 Hz, 3H;
CHAHBP), 6.68 (d, J(H,H)¼2.4 Hz, 3H; Harom), 6.81 (dd,
J(H,H)¼8.7, 2.7 Hz, 3H; Harom), 7.17–7.39 (m, 27H; Harom),
7.89–7.95 (m, 6H; Harom); 13C{1H} NMR (75.4 MHz,
CDCl3): d¼9.12 (CH3CH2), 33.62 (CH3CH2), 37.23 (m;
CH2P), 44.75 (q, 2J(C,P)¼3.4 Hz; CH3CH2C), 56.95
(CH2N), 111.04 (q), 122.77 (d, 3J(C,P)¼11.6 Hz; s-cis-
2
37.73 (m; CH2P), 50.38 [q, J(C,P)¼3.3 Hz; (CH3)2CHC],
57.75 (CH2N), 110.17 (q), 121.51 (d, 3J(C,P)¼11.0 Hz;
3
s-cis-CH]C–N]P), 126.31 (d, J(C,P)¼27.2 Hz; s-trans-
CH]C–N]P), 128.36 (d, 3J(C,P)¼12.8 Hz; mC-PhP),
128.69 (d, 3J(C,P)¼10.4 Hz; mC-PhP), 130.63 (d,
2J(C,P)¼8.1 Hz; oC-PhP), 130.75 (br s; pC-PhP), 131.23,
131.47 (d, 1J(C,P)¼92.4 Hz; iC-PhP), 131.76 (d,
4
2J(C,P)¼9.3 Hz; oC-PhP), 133.30 (d, J(C,P)¼3.2 Hz; pC-
PhP), 133.81 (dleft; iC-PhP), 138.12 (q), 151.29 (q);
31P{1H} NMR (121.4 MHz, CDCl3): d¼0.88; IR (Nujol):

4458
M. Alajarꢀın et al. / Tetrahedron 63 (2007) 4450–4458
n¼1446 (CP), 1116 (NP) cmꢁ1; MS (FAB+): m/z (%)¼
1216 (89) [M++4], 1214 (100) [M++2], 1212 (39) [M+];
C64H58Br3N4P3 (1215.81): calcd C 63.22, H 4.81, N 4.61;
found C 63.35, H 4.69, N 4.76.
ꢀ
Berna, J.; Ramırez de Arellano, M. C. Tetrahedron Lett.
1998, 39, 7807; (d) Alajarın, M.; Lopez-Leonardo, C.; Vidal,
ꢀ
ꢀ
ꢀ
ꢀ
A.; Berna, J.; Steed, J. W. Angew. Chem., Int. Ed. 2002, 41,
1205; (e) Alajarın, M.; Lopez-Leonardo, C.; Berna, J.
ꢀ
ꢀ
ꢀ
Tetrahedron 2006, 62, 6190.
4.6.7. Tri-l5-phosphazene 7i. Yield: 56%; mp (decomp.)
6. (a) Staudinger, H.; Meyer, J. Helv. Chim. Acta 1919, 2, 635; (b)
Gololobov, Y. G.; Zhmurova, I. N.; Kasukhin, L. F. Tetrahedron
1981, 37, 437; (c) Gololobov, Y. G.; Kasukhin, L. F.
Tetrahedron 1992, 48, 1353; Johnson, A. W. Ylides and
Imines of Phosphorus; Wiley: New York, NY, 1993; p 403.
7. (a) Lehn, J. M. Supramolecular Chemistry: Concepts and
Perspectives; VCH: New York, NY, 1995; p 140; (b) Steed,
J. W.; Atwood, J. L. Supramolecular Chemistry; Wiley: New
York, NY, 2000; p 461.
324–326 ꢀC (colourless prisms from chloroform/diethyl
1
ether); H NMR (300 MHz, CDCl3): d¼0.22 (s, 9H; CH3),
2.86 (d, J(H,H)¼15.9 Hz, 3H; CHAHBN), 3.25 (d, J(H,H)¼
15.9 Hz, 3H;CHAHBN), 3.89(pseudot, J(H,H),(H,P)¼16.4 Hz,
3H; CHAHBP), 4.02 (pseudoquint, J(H,H),(H,P)¼
7.8 Hz, 3H; CHAHBP), 6.88 (br s, 3H; Harom), 7.04 (dt,
J(H,H)¼7.7, 2.6 Hz, 9H; Harom), 7.17–7.21 (m, 6H; Harom),
7.28–7.37 (m, 15H; Harom), 8.10–8.14 (m, 6H; Harom);
13C{1H} NMR (75.4 MHz, CDCl3): d¼28.79 [(CH3)3C],
34.80 [(CH3)3C], 38.12 (m; CH2P), 56.24 [q, 2J(C,P)¼
3.1 Hz; (CH3)3CC], 57.83 (CH2N), 109.75 (q), 121.29
(d, 3J(C,P)¼10.4 Hz; s-cis-CH]C–N]P), 126.09 (d,
3J(C,P)¼29.7 Hz; s-trans-CH]C–N]P), 128.08 (d,
ꢀ
ꢀ
ꢀ
8. Alajarın, M.; Lopez-Leonardo, C.; Berna, J.; Steed, J. W.
Tetrahedron 2007, 63, 2078.
9. Global yield of a sequence of two reactions: (a) conversion
of 2-hydroxy-2-nitro-1,3-propanediol to 1,3-dichloro-2-chloro-
methyl-2-nitropropane (53%): Fort, G.; McLean, A. J. Am.
Chem. Soc. 1948, 1902; and (b) conversion of 1,3-dichloro-2-
chloromethyl-2-nitropropane to 1,3-dichloro-2-chloromethyl-
propane (84%): Latour, S.; Wuest, J. D. Synthesis 1987, 742.
10. Janssen, B. C.; Asam, A.; Huttner, G.; Sernau, V.; Zsolnai, L.
Chem. Ber. 1994, 127, 501.
11. Ott, J.; Venanzi, L. M.; Ghilardi, C. A.; Midollini, S.;
Orlandini, A. J. Organomet. Chem. 1985, 291, 89.
12. Janssen, B. C.; Sernau, V.; Huttner, G.; Asam, A.; Water, O.;
B€uchner, M.; Zsolnai, L. Chem. Ber. 1995, 128, 63.
13. For high level calculations on the mechanism of the Staudinger
3
3J(C,P)¼12.2 Hz; mC-PhP), 128.56 (d, J(C,P)¼10.4 Hz;
mC-PhP), 130.34 (br s; pC-PhP), 130.40 (d, 2J(C,P)¼8.1 Hz;
oC-PhP), 130.95 (br s; pC-PhP), 131.44 (d, 1J(C,P)¼
74.8 Hz; iC-PhP), 132.44 (d, 2J(C,P)¼8.7 Hz; oC-PhP),
1
133.02 (d, J(C,P)¼74.8 Hz; iC-PhP), 133.67, 137.71 (q),
151.67 (q); 31P{1H} NMR (121.4 MHz, CDCl3): d¼ꢁ0.02;
IR (Nujol): n¼1451 (CP), 1116 (NP) cmꢁ1; MS (FAB+):
m/z (%)¼1231 (100) [M++5], 1229 (97) [M++3], 1227 (18)
[M++1]; C65H60Br3N4P3 (1229.83): calcd C 63.48, H 4.92,
N 4.56; found C 63.51, H 4.78, N 4.47.
ꢀ
P(III) imination reaction see: (a) Alajarın, M.; Conesa, C.;
Rzepa, H. S. J. Chem. Soc., Perkin Trans. 2 1999, 1811; (b)
Acknowledgements
€
Widauer, C.; Grutzmacher, H.; Shevchenko, Y.; Gramlich, V.
Eur. J. Inorg. Chem. 1999, 1659; (c) Tian, W. Q.; Wang,
Y. A. J. Chem. Theory Comput. 2005, 1, 353.
This work was supported by the MEC and FEDER (Project
ꢀ
ꢀ
CTQ2005-02323/BQU) and Fundacion Seneca-CARM
(Project 00458/PI/04). J.B. also thanks the MEC for a
fellowship.
14. For examples of phosphazides that equilibrate in solution with
their phosphane and azide counterparts, see: (a) Leffler, J. E.;
Honsberg, U.; Tsuno, Y.; Forsblad, I. J. Org. Chem. 1961,
26, 4810; (b) Leffler, J. E.; Tsuno, Y. J. Org. Chem. 1963,
28, 902; (c) Leffler, J. E.; Temple, R. D. J. Am. Chem. Soc.
1967, 89, 5235.
References and notes
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P or M (helical twist sense) to the propeller units of the chiral
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equation: DGz¼(4.57ꢂ10ꢁ3)Tc(10.32+log(Tc2/pDn)) follow-
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Int. Ed. Engl. 1981, 20, 487; (d) Sandstrom, J. Dynamic
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NMR Spectroscopy; Academic: London, 1990.
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Lazaro, A.; Vidal, A.; Berna, J. Chem.—Eur. J. 1998, 4,
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ꢀ
ꢀ
ꢀ