Tripod-tripod coupling of triazides with triphosphanes. The synthesis, characterization, and stability in solution of new cage compounds: Chiral macrobicyclic triphosphazides

Article abstract of DOI:10.1002/(SICI)1521-3765(19981204)4:12<2558::AID-CHEM2558>3.0.CO;2-3

Several examples of a new type of cage compound, chiral macrobicyclic triphosphazides 15, have been prepared by tripod-tripod coupling of tris(2- azidobenzyl)amines with 1,1,1-tris[(diphenylphosphino)methyl] ethane (triphos). The structure determination of C₃ or pseudo-C₃-symmetric compounds 15 revealed their propellerlike topology, which accounted for their chirality, the rare Z configuration of the three phosphazide units, and a new conformation of the triphos fragment. Compounds 15 decomposed in solution with a phosphane arm-off mechanism, to give rise to complex mixtures instead of the expected tri-λ⁵-phosphazenes. The stability of 15 in solution was enhanced by the quaternization of the bridgehead nitrogen atom in the form of an N-oxide. Substituents either in the ortho position to the N termini of the phosphazide units or on the benzylic carbon atoms contributed to a decrease in the stability of macrobicycles 15, and in some cases even prevented their preparation.

Full text of DOI:10.1002/(SICI)1521-3765(19981204)4:12<2558::AID-CHEM2558>3.0.CO;2-3

FULL PAPER
Tripod ± Tripod Coupling of Triazides with Triphosphanes.
The Synthesis, Characterization, and Stability in Solution of New Cage
Compounds: Chiral Macrobicyclic Triphosphazides
Mateo Alajarín,* Antonia LoÂpez-LaÂzaro, Angel Vidal, and Jose BernaÂ
Dedicated to the memory of Derek H. R. Barton
Abstract: Several examples of a new
type of cage compound, chiral macro-
bicyclic triphosphazides 15, have been
prepared by tripod ± tripod coupling of
tris(2-azidobenzyl)amines with 1,1,1-
tris[(diphenylphosphino)methyl]ethane
(triphos). The structure determination
of C3 or pseudo-C3-symmetric com-
pounds 15 revealed their propellerlike
topology, which accounted for their
chirality, the rare Z configuration of
the three phosphazide units, and a new
conformation of the triphos fragment.
Compounds 15 decomposed in solution
with a phosphane arm-off mechanism, to
give rise to complex mixtures instead of
the expected tri-l5-phosphazenes. The
stability of 15 in solution was enhanced
by the quaternization of the bridgehead
nitrogen atom in the form of an N-oxide.
Substituents either in the ortho position
to the N termini of the phosphazide
units or on the benzylic carbon atoms
contributed to a decrease in the stability
of macrobicycles 15, and in some cases
even prevented their preparation.
Keywords: azides ´ cage compounds
´ chirality ´ macrocycles ´ phospha-
zides
major drawback of tripod ± tripod coupling is the occurrence
of extensive side reactions which minimize the yield of the
expected bicyclic product. Only in limited cases[4] have such
processes been carried out in synthetically useful yields,
provided that a fine tuning of reagents, reactions, and
conditions could be achieved.
Introduction
Control of self-organization at the molecular level is a field of
major interest in molecular design and engineering. Molec-
ular self-assembly, defined as the evolution towards spatial
confinement through spontaneous connection of a few compo-
nents, resulting in the formation of discrete entities at the
molecular, covalent level,[1] is in fact a special type of synthetic
procedure in which several reactions between several re-
agents occur in one experimental operation to yield the final
covalent structure. Molecular self-assembly requires firstly
complementary components containing two or more inter-
action sites capable of establishing multiple connections, and
secondly the reversibility of the connecting events in order to
allow the full exploration of the energy hypersurface of the
system.[2]
The imination reaction of tervalent phosphorus derivatives
with organic azides is known as the Staudinger reaction.[5] In
its classical form, the Staudinger reaction is a two-step process
involving the initial electrophilic addition of an azide to a PIII
center followed by dinitrogen elimination from the inter-
mediate phosphazide (R1)3PN3R2 giving the l5-phosphazene
1
2
ˆ
(R )3P NR . The primary imination products, phosphazides,
have only been isolated in a few instances.[5b] The X-ray
structural data of seven phosphazides[6] revealed the essen-
tially zwitterionic character of the PN3 framework
‡
ˆ
(P N N N ) and the almost exclusive E configuration of
Several synthetic strategies may be devised for the con-
struction of macrobicyclic systems. The more direct one is
tripod ± tripod coupling, a molecular self-assembly process
that requires the formation of three bonds in a single step.[3]
ˆ
the central N N bond.
In a previous communication[7] we reported the preparation
of the first two examples of chiral C3-symmetric, macro-
bicyclic triphosphazides by a coupling reaction between two
tripodal subunits by means of triple P ± N bond formation in a
Staudinger reaction, and without recourse to high-dilution
conditions. Such an unprecedented type of cage compound[8]
was shown to possess very rare, intracyclic PN3 units of Z
configuration, propellerlike topology, and a new conforma-
tion of the tripodal phosphane fragment.
A
Â
Â
Â
[*] Dr. M. Alajarín, A. Lopez-Lazaro, Dr. A. Vidal, J. Berna
Â
Departamento de Química Organica
Facultad de Química, Campus de Espinardo
Universidad de Murcia, E-30071 Murcia (Spain)
Fax : (‡ 34)968-364149
E-mail: alajarin@fcu.um.es
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2558±2570
R1
NH2
R2
N3
R1
4
R1
R1
R1
i)
ii)
iii)
NH
2
X
OH
OH
R2
R2
R2
R2
route A
N3
R1
N3
NH2
N3
5
vi)
1
2
3 X = Cl
3’ X = I
route B
v)
a R1 = R2 = H
NY
b R1 = CH3; R2 = H
c R1 = Cl; R2 = H
d R1 = H; R2 = CH3
R2
N3
3
Y = lp
6
iv)
Y = O
7
Scheme 1. Synthesis of C3-symmetric triazides 6 and 7. Reagents and conditions: i) NaNO2, dil. H2SO4, 08C, 30 min, then NaN3, 258C, 16 h; ii) SOCl2,
CH2Cl2, 08C, 3 h; iii) liq. NH3, sealed tube, 258C, 48 h; iv) mCPBA, CHCl3, 258C, 4 h; v) NaI, acetone, 258C, 12 h; vi) 3', dioxane, reflux, 4 h, then Et3N,
258C, 2 h.
Here we report on the preparation and spectroscopic
characterization of a variety of C3 and pseudo-C3-symmetric
macrobicyclic triphosphazides, along with the discussion of
the structural facts that determine their availability and
stability in solution. Attempts to explore the dynamic control
of the topological asymmetry of these species by the absolute
configuration of a stereogenic carbon atom in one of the arms
of the bicyclic skeleton are also reported.
tertiary amines 6 were not obtained in high yields (Table 1),
the simplicity of the method allowed their preparation in
multigram amounts (with the exception of 6c), and the major
Table 1. Synthesis of tris(2-azidobenzyl)amines 6 and their N-oxides 7.
Compound
Route[a]
Yield [%][b]
6a
A
B
A
A
B
37
59
40
0
27
21
68
87
63
80
6b
6c
Results and Discussion
6d
7a
7b
7c
7d
A
C3-Symmetric triazides 6 were prepared by standard proce-
dures, as outlined in Scheme 1, starting from the commercially
available 2-aminobenzyl alcohols 1a ± d, which were convert-
ed into the 2-azidobenzyl chlorides 3 and iodides 3' by well-
known methods. The alkylation of ammonia by the chlorides 3
gave rise to mixtures of primary, secondary, and tertiary
2-azidobenzyl amines 4, 5, and 6, respectively, in variable
yields, from which the pure components could be easily
separated by column chromatography. Although the desired
[a] For an explanation of routes A and B see Scheme 1. [b] Yield of the last
step in the reaction sequence.
components of the reaction mixtures, secondary amines 5,
could be either efficiently converted into 6 by reaction with
iodides 3' or used for the preparation of other triazides (e.g. 8,
Scheme 2). Subsequent oxidation of 6 with mCPBA yielded
N-oxides 7 in good yields.
CS-Symmetric triazides 8 and 11, and their respective N-
oxides 9 and 12, were obtained following similar method-
ologies (Scheme 2). Thus, alkylation of 5b with iodide 3'a
yielded 8 (77% yield), which was then oxidized to 9. The
amine 4b[9] was monoalkylated with 2-azidobenzyl bromide[10]
to give 10 (also used in the synthesis of 13, vide infra), which
reacted with 3'a to give 11 and then 12 by subsequent
oxidation.
Â
Abstract in Spanish: En este trabajo se describe la preparacion
de varios ejemplos de trifosfazidas macrobicíclicas quirales 15
por acoplamiento de especies de estructura tipo trípode: tris(2-
azidobencil)aminas y la trifosfina 1,1,1-[tris(difenilfosfino)me-
Â
til]etano. La determinacion estructural de estos compuestos
pone de manifiesto su topología helicoidal, responsable de su
Â
quiralidad, su simetría local C3 o pseudo-C3, la configuracion
Z de sus tres unidades fosfazida y un nuevo tipo de
Â
conformacion del fragmento trifosfina. Se discuten algunos
factores estructurales que determinan su estabilidad en
Asymmetric triazides 13 and 14 were prepared similarly
starting from the secondary amine 10 (Scheme 3).
Â
disolucion.
Chem. Eur. J. 1998, 4, No. 12
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2559

M. Alajarín et al.
FULL PAPER
R5
CH3
CH3
R1
X
N
i)
X
N
R6
PPh2
PPh2
NH
R3
PPh2
+
N3
R4
R2
N3
N3
N3
2
2
N3
CH3
5b
8 X = lp
9 X = O
N3
ii)
triphos
6-9, 11-14
Et2O, 25 °C, 2-4 h
CH3
CH3
R5
R1
R6
R3
iii)
H
N
X
N
NH2
N3
N3
N3
N
N
R2
R4
N
N
10
4b
N
N
N
i)
P
N
N
P
P
CH3
CH3
X
N
15
N3
N3
11 X = lp
12 X = O
Scheme 4. Synthesis of macrobicyclic triphosphazides 15.
2
ii)
were prepared in good yields, with the exception of 15g which
could not be obtained (Table 2). In this case, the material
isolated from the reaction corresponding to entry 7 of Table 2
seemed to be oligomeric, as indicated by its 1H, 13C, and
31P{1H} NMR spectra.
Scheme 2. Synthesis of CS-symmetric triazides 8 , 9, 11, and 12. Reagents
and conditions: i) 3'a, dioxane, reflux, 4 h, then Et3N, 258C, 2 h;
ii) mCPBA, CHCl3, 258C, 4 h; iii) 2-azidobenzyl bromide, dioxane, reflux,
3 h, then Et3N, 258C, 2 h.
The structure determination of compounds 15 was accom-
plished by means of their analytical and spectral data. Full
characterization of 15a and 15b was discussed in our previous
communication,[7] and the X-ray structure analysis of 15b was
described; it is shown here for convenience (Figure 1).
Selected physical data of the new triphosphazides 15c, 15e,
15i, 15k, and 15m/15m', as well as the triphosphazide N-
oxides 15d, 15 f, 15h, 15j, 15l, and 15n/15n' were essentially
coincident with those of the previously reported 15a and 15b,
respectively (Table 3). For this reason, tridimensional ar-
rangements of the new compounds 15 prepared here were
assumed to be similar to that of 15b, which has been
unequivocally determined by X-ray analysis: a propellerlike
shape, with the X, oxygen, or lone pair (lp), and CH3 groups
on the bridgehead atoms directed away from the bicyclic
CH3
Cl
H
N
+
I
N3
N3
N3
10
3’c
i)
Cl
CH3
X
N
N3
N3
N3
‡
cavity, and with three zwitterionic phosphazide units P ±
ˆ
ˆ
N N ± N of Z configuration around the central N N bond,
X = lp
X = O
13
14
ˆ
ˆ
ii)
which is s-cis in the P N ± N N canonical form.
The simplicity of the NMR data of C3-symmetric 15a ± f and
15h indicates high symmetry. The 31P{1H} NMR spectra of
these compounds show only one singlet at d ˆ 2.56 to 1.34,
shifted 25 ± 30 ppm downfield relative to that of the phos-
phane triphos d ˆ 27.3,[11] in accordance with previous
Scheme 3. Synthesis of asymmetric triazides 13 and 14. Reagents and
conditions: i) dioxane, reflux, 4 h, then Et3N, 258C, 2 h; ii) mCPBA,
CHCl3, 258C, 4 h.
1
The self-assembly of triazides 6 ± 9 and 11 ± 14 with 1,1,1-
tris[(diphenylphosphino)methyl]ethane (triphos) was carried
out in diethyl ether solution at room temperature. The
resulting macrobicyclic triphosphazides 15 (Scheme 4) pre-
cipitated from the reaction medium as yellow solids and
reports on acyclic phosphazides.[12] In the H and 13C NMR
spectra only one set of signals is observed for the three
equivalent arms of the bicyclic structure. The methylene
protons of the CH2N and CH2P groups are magnetically
inequivalent in the 1H NMR spectra, as a consequence of their
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Chem. Eur. J. 1998, 4, No. 12

Tris(phosphazide)s
2558±2570
Table 2. Synthesis of macrobicyclic triphosphazides 15.
Entry
Triazide
R1
R2
R3
R4
R5
R6
X
Product
Yield [%]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
6a
7a
6b
7b
6c
7c
6d
7d
8
H
H
CH3
CH3
Cl
Cl
H
H
CH3
CH3
CH3
CH3
Cl
H
H
H
H
H
H
CH3
CH3
H
H
H
H
H
H
H
CH3
CH3
Cl
Cl
H
H
CH3
CH3
H
H
CH3
CH3
H
H
H
H
H
H
CH3
CH3
H
H
H
H
H
H
H
H
H
H
H
H
H
CH3
CH3
H
H
H
H
H
lp
O
lp
O
lp
O
lp
O
lp
O
lp
O
lp
O
15a
15b
15c
15d
15e
15 f
15g
15h
15i
15j
15k
15l
15m/15m'
15n/15n'
66
85
98
95
42
73
0
27
41
88
57
75
60
93
CH3
CH3
Cl
Cl
H
H
H
H
H
9
11
12
13
14
H
H
H
Cl
H
H
H
Table 3. Selected NMR data of compounds 15.
Com-
1H NMR
13C NMR
31P{1H} NMR
pound
CH3C CH2N CH2P CH3C CH3C CH2N
CH2P
P
15a
15b
15c
15d
15e
15 f
15h
15i
0.13 3.66 3.92
3.88 4.24
0.03 4.18 3.85
4.96 4.10
0.13 3.66 3.92
3.86 4.23
0.06 4.14 3.80
4.89 4.07
0.15 3.59 3.92
3.82 4.14
0.06 4.85 3.75
4.16 ± 3.96
0.26 3.93 4.25[a] 26.21 39.80 64.94
5.12
0.12 4.25 ± 3.65
26.36 40.64 55.61
25.66 40.33 66.74
26.43 40.70 55.62
25.79 40.39 66.69
26.41 40.69 54.75
25.81 40.38 65.13
36.51
37.10
36.60
37.40
36.90
37.50
37.15
36.56
1.34
1.41
0.01
1.44
0.44
1.22
2.56
26.38 40.64 55.46
0.01[a]
0.39
55.54
55.77
25.73 40.34 66.58
66.70
15j
0.04 4.93 ± 3.76
37.28
1.46[a]
1.36
66.78
15k
15l
0.12 4.32 ± 3.59
0.03 4.95 ± 3.79
26.44 40.72 55.50
36.60
37.11
0.03
55.72[a]
0.36[a]
1.49
25.67 40.31 66.62
66.68
1.40[a]
66.80
15m/15m' 0.13 4.25 ± 3.50
26.43 40.69 54.98
55.17
36.62
0.27
0.21
0.14[a]
0.90
1.04
1.73
1.63
1.50
1.37
0.93
0.91
55.19
55.35[a]
55.66
15n/15n'
0.05 5.00 ± 3.60
25.77 40.37 67.00 ± 66.00 37.40
[a] Signals of double intensity.
at d ˆ 0.26 to 0.03, notably shifted upfield relative to those
in the phosphane (d ˆ 0.95[11]), contrary to the diastereotopic
CH2P protons appearing at d ˆ 3.50 ± 4.25, which are shifted
downfield from those in the phosphane (d ˆ 2.48[11]). This data
differs from that of most known triphos ± transition metal
complexes, where these protons appear in the ranges d ˆ
1.12 ± 2.09 (CH3) and d ˆ 2.06 ± 2.78 (CH2P).[13] The explan-
Figure 1. a) Molecular structure of compound 15b; b) a perspec-
tive view as projected along the threefold axis.
diastereotopic nature, and accounting for the chirality of these
propeller-shaped compounds (see Figure 1b).
1
In the H NMR spectra of compounds 15 described here,
the protons of the pivotal CH3 group appear as a broad singlet
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M. Alajarín et al.
FULL PAPER
ation for the peculiar chemical shifts of the protons belonging
to the triphos fragment of compounds 15 stems from the
unusual conformation of this subunit in the macrobicyclic
triphosphazides, which resembles a normal umbrella instead
of the characteristic inverted umbrella conformation found in
all the known triphos complexes in which the ligand is
coordinated in a h3-fashion.
b O_
H
OH
Hb
Ha
Ha
H
H
δ Ha 0.88 ppm
Hb 3.55 ppm
δ Ha 0.60 ppm
Hb 5.28 ppm
Ph
P
R1
R1
_
Ph
P
H6
H6
P
CH3
O
P
P
P
Ph
P
N
N+
Ph
Ph
R2
R2
Ph CH3
CH3
CH3-out
"inverted umbrella"
CH3-out
CH3-in
δ H6 8.85-9.13 ppm
δ H6 < 7.50 ppm
Scheme 5. Downfield shifts of protons resulting from through-space
deshielding effects of oxygen atoms in H NMR spectroscopy.
"normal umbrella"
1
To the best of our knowledge, this normal umbrella
conformation has no precedents and thus accounts for the
shielding of the CH3 protons by the three pseudoapical (vide
infra) PhP groups (C17 ± C22, Figure 1a) and the deshielding
of the CH2P protons by the remaining three pseudoequatorial
PhP rings (C23 ± C28). In this context, the CH3 carbon atom of
15 is also shielded in the 13C NMR spectra (d ˆ 25.66 ± 26.44,
d ˆ 29.5 and 36 ± 40 in the phosphane and its complexes,
respectively).[11, 13] Those relevant NMR shifts may be of
diagnostic value for this new type of conformation of the
triphos fragment.
Neither bicyclic compounds incorporating a triphos frag-
ment nor h3-monometallic triphos complexes showing a CH3-
in conformation have been reported to date. An open-chain
trimetallic complex incorporating a CH3-in triphos unit has
recently been characterized.[14]
With respect to the conformation of the triphos fragment,
the inspection of the X-ray crystallographic data of 15b[7]
reveals short atomic contacts H ± C(sp2) (2.95 and 3.01 Š)
between the pivotal methyl hydrogen atoms and the p-face of
the pseudoapical phenyl groups. These values are in the range
of interatomic distances that give rise to stabilizing [CH ´´´ p]
interactions,[15] which probably play a role in the preorganiza-
tion of triphos in the self-assembly process leading to 15, as
well as in the stability of the resulting products.
only two chemically identical arms, exhibit two singlets in a
1
2:1 intensity ratio in their 31P{1H} NMR spectra. The H and
13C spectra of these bicyclic compounds disclose the diaster-
eotopicity of the two chemically equivalent arms, and there
are separate signals for some of their atoms (see Table 3 and
Experimental Section).
Entries 13 and 14 of Table 2 merit special consideration.
The triphosphazides derived from the constitutionally chiral,
racemic amine 13 and N-oxide 14, like the rest of the chiral 15
prepared in this work, have been obtained in racemic form
but, in these two last cases, as an approximately equimolecular
mixture of two diastereoisomers in each case, 15m/15m' and
15n/15n', respectively. The two diastereoisomers were not
separated from their mixtures but analyzed as such, and the
diastereomeric composition of the product mixtures (1:1) was
deduced by NMR spectroscopy. Their 31P{1H} NMR spectra
show six singlets of equal intensity which correspond to the
three inequivalent phosphorus atoms of each diastereoisomer.
The equimolecular diastereomeric composition of the mix-
tures could also be inferred from some regions of their 1H and
13C NMR spectra, such as the CH2N signals in the 13C
spectrum of 15m/15m' and in the range d ˆ 8.7 ± 9.2 in the 1H
spectrum of 15n/15n'.
In the 1H NMR spectra of triphosphazide N-oxides 15 (X ˆ
O) the aromatic protons in the ortho position to the CH2N
sidechain appear with considerable downfield shifts (d ꢀ 9.0),
as a result of the through-space deshielding effect of the
oxygen atom. Similar effects have been reported before, as is
the case of the half-cage alcohol and the corresponding
alkoxide[16] represented in Scheme 5.
In the 13C NMR spectra of compounds 15, the two phenyl
rings linked to each phosphorus atom are magnetically
inequivalent, and show notable differences in the 1J(C,P)
coupling constants for their two ipso carbons (see Experi-
mental Section). This fact is a consequence of the environ-
ment of the phosphorus atoms,[7] which causes the differ-
entiation of the two PhP rings: one pseudoapical (C17 ± C22,
Figure 1a) and the other pseudoequatorial (C23 ± C28).
As expected, the NMR data of triphosphazides 15i ± n,
which lack the C3 symmetry axis, are more complex than those
of the C3-symmetric 15a ± f and 15h. Compounds 15i ± l, with
From a dynamic stereochemical point of view, the trans-
formations 13 !15m/15m' and 14 !15n/15n' took place
without any diastereoselectivity. This was not unexpected, as
one could hardly imagine how the chirality of the benzyl
amines 13 and 14, which results from the different substituents
Cl, CH3, and H at the 5, 5', and 5'' positions (far away from the
cavity of the macrocyclic products), would influence the
helicity of the self-assembled products.
The conformational rigidity and stability in solution of
compounds 15a and 15b were discussed in the communica-
tion preceding this paper.[7] The new compounds 15 prepared
here have similar properties: i) they do not experience
significant, dynamic processes in CDCl3 solution at room
temperature, as their 1H NMR spectra did not change
on cooling to 203 K; ii) triphosphazides 15 (X ˆ lp) are
instable in CDCl3 solutions at room temperature; they
totally decompose in less than 24 h (as monitored by NMR)
to give intractable mixtures, and iii) triphosphazides 15
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Tris(phosphazide)s
2558±2570
d ꢀ 1.0, close to the one of pure 15a,
which we attributed to the non-
dissociated phosphazide functions.
After 10 h both regions of the
spectrum contained plenty of sig-
nals.
O
N
+
"arm off"
N
N
N
N
N
N
N
Ph
Ph
P
P
CH3
CH3
Ph
Ph
The addition of 3 equivalents of
triphenylphosphane to a solution of
triphosphazide 15a in CDCl3 under
gentle refluxing led to the quantita-
tive formation of tri-l5-phospha-
zene 16, which was identical to a
sample prepared by reaction of
triazide 6a and PPh3, along with
an equivalent amount of triphos
(Scheme 6).
15a
15b
stable in solution
unstable in solution
+
N
N
N
N
pyramidal inversion at N
promotes decomposition
Ph2P
CH3
IR (CDCl3): 2100 cm-1 [N3]
31P{1H} NMR (CDCl3): - 27.1 ppm [Ph2PCH2]
~1.0 ppm [PN3]
This result accounted for the
dissociation, in solution, of the
phosphazide functions of 15a, thus
allowing the Staudinger reaction[5]
of the so-formed azido groups with
the externally added phosphane
PPh3, and the extrusion of dinitro-
gen from the new phosphazide units
to complete the formation of 16. To
our knowledge, such interchange of
3 PPh3, CDCl3,
3 PPh3, C6H6,
80 %
6a
N
N
CDCl3
71 %
PPh3
N
25 °C
Ph3P
triphos
N
PPh3
complex mixture
16
Scheme 6. Mechanistic proposal for the decomposition of compounds 15 (X ˆ lp) in CDCl3 solution,
and for the preparation of tri-l5-phosphazene 16.
phosphane fragments in phosphazides has no precedent in the
chemical literature.
(X ˆ O) are notably more stable; they remain unchanged
in CDCl3 solution at room temperature after several
weeks; high-temperature 1H NMR experiments (CDCl3,
from 298 to 330 K) showed no changes in their normal
spectra.
From this data, as well as from the spectral characteristics of
15, two consequences could be concluded. Firstly, the
propellerlike shape of the chiral macrobicycles is retained in
solution in the range of temperatures studied, and enantio-
merization processes via labile conformations with local C1
symmetry could be discarded. Secondly, the lability of 15
(X ˆ lp) in solution could be favored by the pyramidal
inversion of the bridgehead nitrogen atom, given that its
quaternization in the form of the N-oxides 15 (X ˆ O)
resulted in greater stability.
We reasoned that the lability of 15 (X ˆ lp) in solution could
result from the initial dissociation of one phosphazide
function into phosphane and azide, promoted by the simulta-
neous inversion of the pivotal nitrogen atom (Scheme 6). This
step is slightly reminiscent of the phosphane arm-off mech-
anism operative in some h3-triphos ± metal complexes by
which one phosphane arm temporarily detaches from the
metal.[17] Moreover, some phosphazides have been reported
to equilibrate in solution with their phosphane and azide
counterparts.[18] We have obtained some experimental evi-
dence that support, although not conclusively, the proposed
mechanism.
With regard to the factors that govern the stability of 15 in
solution, the unsuccessful attempt to prepare triphosphazide
15g was illustrative. We rationalized this failure to be a
consequence, presumably, of the instability of the expected
product 15g, and taking account of the low stability of its N-
oxide analogue 15h. Unlike the rest of the triphosphazide
N-oxides 15 (X ˆ O) in Table 2, which were stable in solution,
compound 15h decomposed in CDCl3 solution at room
temperature in less than 6 h. These particular properties of
15g and 15h when compared with the other compounds 15
(X ˆ lp) and 15 (X ˆ O), respectively, may be due to the
presence of three CH3 groups in the 3, 3', and 3'' positions of
the tribenzylamine fragment, which flank the azido groups.
This might cause a twisting of the trisubstituted aromatic rings
out of the phosphazide planes, in order to avoid the steric
interference of the methyl hydrogens with the lone pair on the
central nitrogen of the PN3 units, thus preventing the effective
conjugation of both p-systems and so enhancing the instability
of 15g and 15h. The effect of substituents R of increasing
bulkiness (H < CH3 < I) at the 6-position in the upfield
shifting of the methyl protons in the 1H NMR spectra of
2-methyl-6-R-substituted azobenzenes[19] has been rational-
ized in similar terms (N-aryl twisting), as summarized in
Scheme 7.
In this context, the observed chemical shift of the 3,3',3''-
(CH3)3 protons in the 1H NMR spectrum of 15h, d ˆ 1.71, may
be indicative of the N-aryl twisting proposed above to explain
its instability in solution.
With the aim of obtaining more information on the effect
that substituents in the ortho position to the -N3P groups have
on the stability of triphosphazides 15, we synthesized triazides
FT-IR experiments on aliquots of a CDCl3 solution of 15a
at room temperature after one hour displayed absorptions
1
near nÄ ˆ 2100 cm , which may be attributed to the N3 group
of the split PN3 unit. Similarly, 31P{1H} NMR spectra
contained one singlet at d ˆ 27.1, which is in the range of
the phosphane P atoms, along with some others signals at
Chem. Eur. J. 1998, 4, No. 12
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M. Alajarín et al.
FULL PAPER
in less than 24 h. In contrast, 21 is approximately as stable as
the other 15 (X ˆ O) compounds discussed above, with the
exception of 15h. These qualitative results indicate the
negligible effect of one methyl group ortho to the -N3P
functions on the stability in solution of the macrobicyclic
tris(phosphazide)s.
On the other hand, Canary et al. recently reported the
preparation of coordination complexes with propellerlike
chirality and C3-symmetrical arrangements, derived from the
tripodal ligand tris(2-pyridylmethyl)amine (TPA).[20] Surpris-
ingly, they found that the presence of an alkyl substituent on
the sp3 carbon atom of one arm of the ligand, in for example
amine a-MeTPA, gave rise to coordination complexes in
which the sense of twist (L or D) of their helical asymmetry
was dictated by the configuration of the chiral carbon atom (R
or S, respectively). A similar effect has been observed in the
preparation of a helical RhI complex of the new tripodal
ligand 1,3-bis(diphenylphosphino)-2-[(diphenylphosphino)-
methyl]-1-phenylpropane (heliphos).[21]
X
N
X
N
H3C
H3C
N
N
N
N
N
N
P
P
C
C
Ph2
Ph2
CH3
CH3
3
3
15g (X = lp)
15h (X = O)
H3C
R
H3C
R
N
N
N
N
R
δ CH3
H
Me
I
2.68
2.38
2.20
Scheme 7. N-Aryl twisting in triphosphazides 15g, 15h, and azobenzenes
caused by the steric interference of ortho substituents.
18 and 19 by standard methods, starting from the azidobenzyl
chloride 3d (Scheme 8). Both triazides, possessing only one
methyl group in the ortho position to the azido groups,
coupled efficiently with triphos to yield the new macrobi-
cycles 20 and 21.
With these results in mind, we prepared racemic triazide 23,
which bears a methyl substituent on a benzylic carbon, by
dialkylation of the known amine 22[9](Scheme 9).
We hoped that the methyl group of triazide 23 would
control the topological asymmetry of the triphosphazide,
which would result from its self-assembly with triphos, to give
rise to predominantly one of the two possible diastereoiso-
meric macrobicycles. Unfortunate-
The stability in solution of these two triphosphazides was
1
studied by H and 31P{1H} NMR spectroscopy in CDCl3 at
room temperature. The stability of compound 20 is similar to
all the previously described 15 (X ˆ lp); it totally decomposed
ly, 23 did not couple efficiently with
triphos either under standard con-
ditions (room temperature, diethyl
ether) or at lower temperatures;
these reactions always yielded un-
characterized oligomers. This fail-
ure, obviously associated with the
ii)
i)
NPhth
NH2
Cl
H3C
H3C
H3C
N3
17 Phth =
N3
N3
O
O
4d
3d
iii)
presence of the methyl substituent,
may be caused either by the ther-
modynamic instability of the puta-
X
N
X
N
H3C
tive triphosphazide, due to the
v)
N
N
N
methyl group placed in the steri-
cally congested interior of the cav-
ity, or by the lower population of
the optimally reactive conformer of
23 for the self-assembly reaction
when compared with the unsubsti-
tuted tribenzylamine 6a.[22]
In contrast to all phosphazides
reported hitherto, the macrobicyclic
triphosphazides 15, 20, and 21 did
not extrude dinitrogen to give
N
N
N
N
H3C
P
N
N
N3
N3
iv)
P
2
P
CH3
X = lp
X = O
18
19
20 X = lp, 51 %
X = O, 52 %
21
Scheme 8. Synthesis of triphosphazides 20 and 21. Reagents and conditions: i) Potassium phthalimide
(KNPhth), DMF, 808C, 12 h; ii) N2H4 ´ H2O, EtOH, reflux, 3 h; iii) 3'a, dioxane, reflux, 4 h, then Et3N,
258C, 2 h; iv) mCPBA, CHCl3, 258C, 4 h; v) triphos, Et2O, 258C, 2 h.
2564
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Chem. Eur. J. 1998, 4, No. 12

Tris(phosphazide)s
2558±2570
sterically congested than the former, with severe interactions
between the above-mentioned methylene groups (as a result
of the shortening of the P ± Ng bond), and also of the new
apical Ph groups with several atoms of the arm in their
vicinity. In the model of the final l5-phosphazene, only the
zone between the methylene carbons remained sterically
congested.
We are currently investigating which of the above con-
straints determine the inability of compounds 15 to yield tri-
l5-phosphazenes by the study of new macrobicyclic triphos-
phazides less sterically congested than 15.
i)
N
NH2
N3 CH3
N3
N3 CH3
2
22
23
Scheme 9. Synthesis of triazide 23. Reagents and conditions: i) 3'a,
dioxane, reflux, 4 h, then Et3N, 258C, 2 h.
the corresponding tri-l5-phosphazenes upon heating in sol-
ution.[5] Instead, such attempts gave only intractable mixtures
in which the corresponding tri-l5-phosphazenes could neither
be isolated nor spectroscopically detected, under a variety of
experimental conditions (solvent, temperature). In some way
not yet fully understood, the conformational constraints
imposed on these triphosphazides by their bicyclic skeletons
render difficult either the collapsing of the phosphazide units
to four-membered l5-triazaphosphetine rings or the Berry
pseudorotation[23] at the bipyramidal phosphorus atoms of
these phosphacycles, mechanistically mandatory to translate
the Na atom from equatorial to apical position, a prerequisite
to the fragmentation of the P Na bond that would achieve the
extrusion of dinitrogen (Scheme 10).
Conclusions
A wide range of examples of a new type of cage compound,
chiral macrobicyclic triphosphazides, has been prepared. The
relevant structural characteristics common to these com-
pounds are:
*
their propellerlike topology;
*
the rare s-cis configuration of their PN3 units (Z config-
‡
ˆ
uration of the P ± N N ± N canonical form),
*
and the unusual conformation of their triphos fragments.
The stability in solution of these species has been qual-
itatively evaluated and found to be related to the following
structural factors:
X
*
the quaternization of the pivotal nitrogen atom, in the form
X
N
of an N-oxide, increased their stability;
the presence of substituents flanking the N termini of the
phosphazide functions decreased their stability.
γ
N
*
N
γ
β
α
N
N
N
N
β
N
P
P
The reported method is not suitable for the synthesis of
macrobicyclic tri-phosphazides substituted at the benzylic
carbon atoms. These macrobicycles did not collapse to the
corresponding tri-l5-phosphazenes in the usual way following
the Staudinger reaction; instead they decompose in solution,
through an arm-off mechanism, to give complex mixtures.
C
C
Ph2
Ph
Ph
CH3
CH3
α
3
3
λ5-triazaphosphetine
pseudorotation
Experimental Section
X
N
X
N
All melting points were determined on a Kofler hot-plate melting point
apparatus and are uncorrected. IR spectra were obtained as Nujol
emulsions or films on a Nicolet Impact 400 spectrophotometer. NMR
spectra were recorded on a Bruker AC200 or a Varian Unity 300. Chemical
α
β
_ N N
γ
β
N
N
N
P
Ph
C
C
P
N
α
Ph2
1
CH3
CH3
Ph
shifts are given relative to tetramethylsilane (TMS) in the case of H and
13C spectra and to 85% aqueous phosphoric acid in the case of 31P.
Abbreviations of coupling patterns are as follows: s, singlet; d, doublet; t,
triplet; q, quadruplet. Mass spectra were recorded on a Hewlett-Pack-
ard5993C spectrometer (EI) or on a VG-Autospec spectrometer (FAB ‡ ).
Microanalyses were performed on a Carlo Erba EA-1108 instrument.
3
3
Scheme 10. Mechanistic pathway for the conversion of macrobicyclic
triphosphazides into tri-l5-phosphazenes.
Materials: Compounds 2-azidobenzyl alcohol (2a),[24] 2-azido-5-methyl-
benzyl alcohol (2b),[25] 2-azido-3-methylbenzyl alcohol (2d),[25] 2-azido-
benzyl chloride (3a),[26] 2-azido-5-methylbenzyl chloride (3b),[9] and
2-azido-a-methylbenzylamine (23)[9] were prepared following previously
reported procedures.
The inspection of molecular models of the species repre-
sented in Scheme 10 showed severe steric constraints in the
structure of the l5-triazaphosphetine initially formed, partic-
ularly that caused by the apical Ph groups and the methyl
hydrogen atoms, as well that caused by the proximity of both
methylene groups in each arm of the macrobicyclic skeleton.
The less constrained pseudorotation process at the phospho-
rus appeared to be that which involves the equatorial P ± CH2
bond as a pivot, so that the resulting structure seemed more
Preparation of 2-azido-5-chlorobenzyl alcohol (2c): A solution of sodium
nitrite (3.30 g, 48 mmol) in H2O (30 mL) was added dropwise to an ice-
cooled solution of 2-amino-5-chlorobenzyl alcohol (5.20 g, 33 mmol) in
H2O (40 mL) and concentrated sulfuric acid (7.3 mL). The mixture was
stirred at that temperature for 30 min. A solution of sodium azide (4.42 g,
68 mmol) in H2O (25 mL) was then added dropwise. After stirring for 16 h
Chem. Eur. J. 1998, 4, No. 12
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2565

M. Alajarín et al.
FULL PAPER
‡
at room temperature, the precipitated solid was isolated by filtration,
washed with H2O (100 mL), air dried, and recrystallized from abs. EtOH to
give 2c. Yield: 80%, colorless prisms. M.p. 61 ± 628C; 1H NMR (200 MHz,
CDCl3): d ˆ 2.61 (brs, 1H; OH), 4.55 (s, 2H; CH2), 7.04 (d, J(H,H) ˆ
8.4 Hz, 1H; H3), 7.25 (dd, J(H,H) ˆ 8.4, 2.4 Hz, 1H; H4), 7.35 (d,
J(H,H) ˆ 2.4 Hz, 1H; H6); 13C NMR (50.3 MHz, CDCl3): d ˆ 60.66
(CH2), 119.16, 128.65, 128.72, 130.31 (s), 133.57 (s), 136.03 (s); IR (Nujol):
EI): m/z (%) ˆ 410 (4) [M ], 77 (100); C21H18N10 (410.44): calcd C 61.45, H
4.42, N 34.12; found C 61.30, H 4.51, N 34.02.
2-Azido-5-methylbenzylamine (4b):[9] Yield: 20%.
Bis(2-azido-5-methylbenzyl)amine (5b): Yield: 35%; 1H NMR (200 MHz,
CDCl3): d ˆ 1.95 (brs, 1H; NH), 2.29 (s, 6H; CH3), 3.65 (s, 4H; CH2), 6.96 ±
7.21 (m, 6H); 13C NMR (50.3 MHz, CDCl3): d ˆ 20.67 (CH3), 48.85 (CH2),
117.78, 128.77, 130.91, 130.95 (s), 134.24 (s), 135.19 (s); IR (film): nÄ ˆ 3343
‡
nÄ ˆ 3211 (OH), 2123 (N3) cm 1; MS (70 eV, EI): m/z (%) ˆ 185 (7) [M ‡2],
(NH), 2121 (N3) cm 1; MS (70 eV, EI): m/z (%) ˆ 307 (5) [M ], 133 (100);
‡
‡
183 (22) [M ], 129 (31), 127 (100); C7H6ClN3O (183.60): calcd C 45.79, H
C16H17N7 (307.36): calcd C 62.52, H 5.57, N 31.90; found C 62.38, H 5.45, N
32.00.
3.29, N 22.89; found C 45.41, H 3.65, N 23.09.
General procedure for the preparation of the 2-azidobenzyl chlorides (3):
Thionyl chloride (4.16 g, 35 mmol) was added dropwise to an ice-cooled
solution of the corresponding 2-azidobenzyl alcohol 2 (30 mmol) in dry
CH2Cl2 (40 mL) and the reaction mixture was stirred at 08C for 3 h. The
solvent was removed under reduced pressure and the residue was purified
by column chromatography (silica gel; diethyl ether/n-hexane 1:1), to give
compounds 3 as yellow oils.
Tris(2-azido-5-methylbenzyl)amine (6b): Yield 40%; m.p. 113 ± 1158C
(colorless prisms from diethyl ether); 1H NMR (200 MHz, CDCl3): d ˆ 2.31
(s, 9H; CH3), 3.50 (s, 6H; CH2), 6.97 (d, J(H,H) ˆ 8.1 Hz, 3H), 7.03 (d,
J(H,H) ˆ 8.1 Hz, 3H), 7.33 (s, 3H); 13C NMR (50.3 MHz, CDCl3): d ˆ 20.95
(CH3), 53.04 (CH2), 117.80, 128.63, 130.44 (s), 131.51, 134.07 (s), 135.55 (s);
‡
IR (Nujol): nÄ ˆ 2122 (N3) cm 1; MS (70 eV, EI): m/z (%) ˆ 452 (6) [M ], 91
(100); C24H24N10 (452.52): calcd C 63.70, H 5.34, N 30.95; found C 63.51, H
5.23, N 30.90.
2-Azido-5-chlorobenzyl chloride (3c): Yield: 91%; 1H NMR (200 MHz,
CDCl3): d ˆ 4.45 (s, 2H; CH2), 7.00 (d, J(H,H) ˆ 8.5 Hz, 1H; H3), 7.26 (dd,
J(H,H) ˆ 8.5, 2.5 Hz, 1H; H4), 7.33 (d, J(H,H) ˆ 2.5 Hz, 1H; H6); 13C NMR
(50.3 MHz, CDCl3): d ˆ 40.55 (CH2), 119.44, 129.73, 129.94 (s), 130.02 (s),
130.60, 136.89 (s); IR (film): nÄ ˆ 2128 (N3) cm 1; MS (70 eV, EI): m/z (%) ˆ
2-Azido-5-chlorobenzylamine (4c): Yield: 14%; 1H NMR (200 MHz,
CDCl3): d ˆ 1.71 (brs, 2H; NH2), 3.74 (s, 2H; CH2), 7.04 (d, J(H,H) ˆ
8.4 Hz, 1H; H3), 7.24 (dd, J(H,H) ˆ 8.4, 2.4 Hz, 1H; H4), 7.29 (d, J(H,H) ˆ
2.4 Hz, 1H; H6); 13C (NMR (50.4 MHz, CDCl3): d ˆ 42.17 (CH2), 119.24,
127.94, 128.93, 130.09 (s), 136.04 (s), 136.30 (s); IR (film): nÄ ˆ 3375 (NH2),
‡
‡
‡
206 (5) [M ‡4], 204 (9) [M ‡2], 202 (18) [M ], 88 (100); C7H5Cl2N3
(202.04): calcd C 41.61, H 2.49, N 20.80; found C 41.29, H 2.22, N 21.04.
‡
3278 (NH2), 2121 (N3) cm 1; MS (70 eV, EI): m/z (%) ˆ 184 (2) [M ‡2],
2-Azido-3-methylbenzyl chloride (3d): Yield: 78%; 1H NMR (200 MHz,
CDCl3): d ˆ 2.42 (s, 3H; CH3), 4.63 (s, 2H; CH2), 7.00 ± 7.24 (m, 3H);
13C NMR (50.3 MHz, CDCl3): d ˆ 17.92 (CH3), 42.82 (CH2), 126.16, 128.53,
131.25 (s), 132.02, 133.21 (s), 136.98 (s); IR (film): nÄ ˆ 2130 (N3) cm 1; MS
‡
182 (6) [M ], 153 (100); C7H7ClN4 (182.61): calcd C 46.04, H 3.86, N 30.68;
found C 45.89, H 3.59, N 30.83.
1
Bis(2-azido-5-chlorobenzyl)amine (5c): Yield: 73%; H NMR (200 MHz,
CDCl3): d ˆ 3.68 (s, 4H; CH2), 7.06 (d, J(H,H) ˆ 8.4 Hz, 2H; H3), 7.27 (dd,
J(H,H) ˆ 8.4, 2.3 Hz, 2H; H4), 7.35 (d, J(H,H) ˆ 2.3 Hz, 2H; H6), the NH
proton was not observed; 13C NMR (50.3 MHz, CDCl3): d ˆ 48.47 (CH2),
119.34, 128.40, 130.19, 132.94 (s), 136.83 (s), a (s) carbon was not observed;
IR (film): nÄ ˆ 3290 (NH), 2133 (N3) cm 1; MS (70 eV, EI): m/z (%) ˆ 348
‡
‡
(70 eV, EI): m/z (%) ˆ 183 (61) [M ‡2], 181 (15) [M ], 153 (100);
C8H8ClN3 (181.62): calcd C 52.90, H 4.44, N 23.14; found C 53.13, H 4.81, N
22.81.
General procedure for the preparation of the 2-azidobenzyl iodides (3'):
Sodium iodide (2.85 g, 19 mmol) was added in one go to a solution of the
corresponding 2-azidobenzyl chloride 3 (13 mmol) in dry acetone (25 mL).
The reaction mixture was stirred at room temperature for 12 h. The
precipitated solid was separated by filtration. From the filtrate, the solvent
was removed under reduced pressure and the resulting material was
chromatographed (silica gel; diethyl ether/n-hexane 1:1).
‡
(26) [M ], 140 (100); C14H11Cl2N7 (348.19): calcd C 48.29, H 3.18, N 28.16;
found: 48.45, H 3.23, N 28.31.
Tris(2-azido-5-chlorobenzyl)amine (6c): Yield: 0%.
2-Azido-3-methylbenzylamine (4d): Yield: 12%; 1H NMR (200 MHz,
CDCl3): d ˆ 1.74 (brs, 2H; NH2), 2.30 (s, 3H; CH3), 3.70 (s, 2H; CH2),
6.90 ± 7.10 (m, 3H); 13C NMR (50.3 MHz, CDCl3): d ˆ 24.86 (CH3), 42.99
(CH2), 126.01, 126.67, 130.34, 132.64 (s), 136.08 (s), 149.72 (s); IR (film): nÄ ˆ
3375 (NH2), 3286 (NH2), 2130 (N3) cm 1; MS (70 eV, EI): m/z (%) ˆ 162
2-Azidobenzyl iodide (3'a): Yield: 83%; m.p. 85 ± 878C (colorless prisms
1
from n-hexane); H NMR (200 MHz, CDCl3): d ˆ 4.39 (s, 2H; CH2), 7.06
(m, 2H), 7.29 (m, 2H); 13C NMR (50.3 MHz, CDCl3): d ˆ 0.33 (CH2),
118.68, 125.07, 129.52, 130.28, 130.64 (s), 138.16 (s); IR (Nujol): nÄ ˆ 2120
‡
(21) [M ]; C8H10N4 (162.19): calcd C 59.24, H 6.21, N 34.54; found C 59.46,
H 6.02, N 34.31.
‡
(N3) cm 1; MS (70 eV, EI): m/z (%) ˆ 259 (3) [M ], 132 (100); C7H6IN3
Bis(2-azido-3-methylbenzyl)amine (5d): Yield: 51%; 1H NMR (300 MHz,
CDCl3): d ˆ 2.40 (s, 6H; CH3), 3.85 (s, 4H; CH2), 7.05 ± 7.07 (m, 4H), 7.18 ±
7.20 (m, 2H), the NH proton was not observed; 13C NMR (75.4 MHz,
CDCl3): d ˆ 18.11 (CH3), 49.85 (CH2), 125.82, 128.00, 130.38, 132.64 (s),
133.81 (s), 136.76 (s); IR (film): nÄ ˆ 3150 (NH), 2116 (N3) cm 1; MS (70 eV,
(259.05): calcd C 32.45, H 2.33, N 16.22; found C 32.31, H 2.24, N 16.37.
2-Azido-5-chlorobenzyl iodide (3'c): Yield: 86%; m.p. 45 ± 468C (yellow
1
prisms from diethyl ether); H NMR (200 MHz, CDCl3): d ˆ 4.32 (s, 2H;
CH2), 7.04 (d, J(H,H) ˆ 8.4 Hz, 1H; H3), 7.25 (dd, J(H,H) ˆ 8.4, 2.4 Hz,
1H; H4), 7.32 (d, J(H,H) ˆ 2.4 Hz, 1H; H6); 13C NMR (50.3 MHz, CDCl3):
‡
EI): m/z (%) ˆ 307 (10) [M ], 133 (100); C16H17N7 (307.36): calcd C 62.52,
d ˆ 1.44 (CH2), 119.93, 129.48, 130.12 (s), 130.45, 131.96 (s), 136.82 (s); IR
H 5.57, N 31.90; found C 62.26, H 5.60, N 31.73.
‡
(Nujol): nÄ ˆ 2125 (N3) cm 1; MS (70 eV, EI): m/z (%) ˆ 166 (18) [M
I],
Tris(2-azido-3-methylbenzyl)amine (6d): Yield: 21%; 1H NMR (200 MHz,
CDCl3): d ˆ 2.37 (s, 9H; CH3), 3.67 (s, 6H; CH2), 7.05 (m, 6H), 7.41 (dd,
J(H,H) ˆ 7.2, 2.1 Hz, 3H); 13C NMR (50.3 MHz, CDCl3): d ˆ 17.98 (CH3),
54.40 (CH2), 125.68, 128.22, 130.00, 132.50 (s), 132.91 (s), 136.99 (s); IR
102 (100); C7H5ClIN3 (293.49): calcd C 28.65, H 1.72, N 14.32; found C
28.86, H 2.05, N 14.57.
General procedure for the preparation of tris(2-azidobenzyl)amines (6):
Route A:
A
mixture of the corresponding 2-azidobenzyl chloride
3
‡
(film): nÄ ˆ 2114 (N3) cm 1; MS (70 eV, EI): m/z (%) ˆ 452 (8) [M ], 132
(40 mmol) and liquid ammonia (50 mL) was kept 48 h at room temperature
in a sealed tube. The excess ammonia was removed by evaporation,
followed by the addition of H2O (100 mL) and NaOH (20 mL, 2n). The
mixture was extracted with CH2Cl2 (3 Â 40 mL), and the organic extracts
were combined and dried over anhydrous MgSO4. The solvent was
removed under reduced pressure, and the residue, a mixture of amines 4, 5,
and 6, was separated by chromatography [silica gel; 1) ethyl acetate/n-
hexane 1:1, 2) ethanol].
(100); C24H24N10 (452.52): calcd C 63.70, H 5.34, N 30.95; found C 63.49, H
5.20, N 31.13.
Preparation of (2-azidobenzyl)(2-azido-5-methylbenzyl)amine (10): 2-Azi-
dobenzyl bromide[10] (0.57 g, 3 mmol) was added to a solution of 2-azido-5-
methylbenzylamine (4b, 0.65 g, 4 mmol) in dry dioxane (20 mL). The
mixture was heated at reflux temperature for 3 h. After cooling to room
temperature, triethylamine (0.40 g, 4 mmol) was added, and the mixture
then stirred for 2 h. The triethylammonium bromide was separated by
filtration, and the solvent removed under reduced pressure. The resulting
material was chromatographed (silica gel; ethyl acetate/n-hexane 2:3), to
give 10 as a pale oil.
2-Azidobenzylamine (4a):[27] Yield: 25%.
Bis(2-azidobenzyl)amine (5a):[9] Yield: 37%.
Tris(2-azidobenzyl)amine (6a): Yield: 37%; m.p. 64 ± 668C (colorless
1
prisms from diethyl ether); H NMR (200 MHz, CDCl3): d ˆ 3.55 (s, 6H;
(2-Azidobenzyl)(2-azido-5-methylbenzyl)amine (10): Yield: 39%;
1H NMR (200 MHz, CDCl3): d ˆ 1.26 (s, 1H; NH), 2.31 (s, 3H; CH3),
3.68 (s, 2H; CH2), 3.72 (s, 2H; CH2), 7.00 ± 7.15 (m, 4H), 7.27 ± 7.34 (m, 3H);
13C NMR (50.3 MHz, CDCl3): d ˆ 20.86 (CH3), 48.97 (CH2), 49.03 (CH2),
CH2), 7.09 (m, 6H), 7.23 (t, J(H,H) ˆ 7.6 Hz, 3H), 7.57 (d, J(H,H) ˆ 7.7 Hz,
3H); 13C NMR (50.3 MHz, CDCl3): d ˆ 52.94 (CH2), 118.04, 124.74, 128.14,
130.40, 130.86 (s), 138.40 (s); IR (Nujol): nÄ ˆ 2128 (N3) cm 1; MS (70 eV,
2566
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
0947-6539/98/0412-2566 $ 17.50+.50/0
Chem. Eur. J. 1998, 4, No. 12

Tris(phosphazide)s
2558±2570
118.01, 118.13, 124.75, 128.46, 128.99, 130.44, 131.04 (s), 131.10, 131.39 (s),
Tris(2-azido-5-chlorobenzyl)amine N-oxide (7c): Yield: 63%; m.p. 121 ±
122oC (colorless prisms from CHCl3/Et2O); 1H NMR (300 MHz, CDCl3):
d ˆ 4.17 (s, 6H; CH2), 7.11 (d, J(H,H) ˆ 8.6 Hz, 3H; H3), 7.39 (dd,
J(H,H) ˆ 8.6, 2.5 Hz, 3H; H4), 7.90 (d, J(H,H) ˆ 2.5 Hz, 3H; H6);
13C NMR (75.4 MHz, CDCl3): d ˆ 64.11 (CH2), 118.68, 123.57 (s), 130.25
(s), 130.91, 135.82, 138.43 (s); IR (Nujol): nÄ ˆ 2135 (N3) cm 1; MS (70 eV,
EI): m/z (%) ˆ 254 (6), 102 (100); C21H15Cl3N10O (529.78): calcd C 47.61, H
2.85, N 26.44; found C 47.49, H 2.99, N 26.52.
134.49 (s), 135.40 (s), 138.26 (s); IR (film): nÄ ˆ 2131 (N3) cm 1; MS (70 eV,
‡
EI): m/z (%) ˆ 293 (5) [M ], 133 (100); C15H15N7 (293.33): calcd C 61.42, H
5.15, N 33.42; found C 61.27, H 4.98, N 33.58.
General procedure for the preparation of tris(2-azidobenzyl)amines:
Route B: The appropriate 2-azidobenzyl iodide (1 mmol) was added to a
solution of the corresponding bis(2-azidobenzyl)amine (1 mmol) in dry
dioxane (20 mL), and the mixture was stirred at reflux temperature for 8 h.
After cooling to room temperature, triethylamine (0.15 g, 1.3 mmol) was
added, and the mixture was stirred for 3 h. The triethylammonium iodide
was separated by filtration. From the filtrate, the dioxane was evaporated
to dryness and the residue was purified by column chromatography (silica
gel; ethyl acetate/n-hexane 3:7).
Tris(2-azido-3-methylbenzyl)amine N-oxide (7d): Yield: 80%; m.p. 90 ±
91oC (colorless prisms from CHCl3/Et2O); 1H NMR (300 MHz, CDCl3):
d ˆ 2.47 (s, 9H; CH3), 4.40 (s, 6H; CH2), 7.08 ± 7.23 (m, 6H), 7.71 (dd,
J(H,H) ˆ 7.3, 1.4 Hz, 3H); 13C NMR (75.4 MHz, CDCl3): d ˆ 18.25 (CH3),
65.37 (CH2), 124.51 (s), 125.84, 132.45 (s), 132.74, 133.17, 138.54 (s); IR
‡
(Nujol): nÄ ˆ 2126 (N3) cm 1; MS (70 eV, EI): m/z (%) ˆ 468 (23) [M ], 235
Tris(2-azido-5-chlorobenzyl)amine (6c): Yield: 27%; 1H NMR (300 MHz,
CDCl3): d ˆ 3.50 (s, 6H; CH2), 7.00 (d, J(H,H) ˆ 8.5 Hz, 3H; H3), 7.21 (dd,
J(H,H) ˆ 8.5, 2.4 Hz, 3H; H4), 7.48 (d, J(H,H) ˆ 2.4 Hz, 3H; H6); 13C NMR
(75.4 MHz, CDCl3): d ˆ 53.34 (CH2), 119.22, 128.38, 130.09 (s), 130.80,
131.76 (s), 137.04 (s); IR (film): nÄ ˆ 2131 (N3) cm 1; MS (70 eV, EI): m/z
(100); C24H24N10O (468.48): calcd C 61.53, H 5.16, N 29.89; found C 61.48, H
5.28, N 29.76.
Bis(2-azido-5-methylbenzyl)(2-azidobenzyl)amine N-oxide (9): Yield:
38%; m.p. 118 ± 1208C (colorless prisms from CHCl3/Et2O); 1H NMR
(300 MHz, CDCl3): d ˆ 2.31 (s, 6H; CH3), 4.21 (s, 4H; CH2), 4.24 (s, 2H;
CH2), 7.04 ± 7.86 (m, 10H); 13C NMR (75.4 MHz, CDCl3): d ˆ 20.76 (CH3),
64.29 (CH2), 64.45 (CH2), 117.31, 117.44, 122.18 (s), 122.57 (s), 124.63,
130.48, 131.25, 134.39 (s), 136.17, 136.48, 137.02 (s), 139.79 (s); IR (Nujol):
‡
(%) ˆ 513 (13) [M ], 102 (100); C21H15Cl3N10 (513.78): calcd C 49.09, H
2.94, N 27.26; found C 48.87, H 2.81, N 27.19.
Bis(2-azido-5-methylbenzyl)(2-azidobenzyl)amine (8): Yield: 77%; m.p.
82 ± 848C (colorless prisms from diethyl ether); 1H NMR (200 MHz,
CDCl3): d ˆ 2.31 (s, 6H; CH3), 3.50 (s, 4H; CH2), 3.54 (s, 2H; CH2), 6.94 ±
7.55 (m, 10H); 13C NMR (50.3 MHz, CDCl3): d ˆ 21.05 (CH3), 53.08 (CH2),
117.89, 118.01, 124.62, 128.08, 128.74, 130.46 (s), 130.66, 130.97 (s), 131.42,
134.20 (s), 135.64 (s), 138.40 (s); IR (Nujol): nÄ ˆ 2126 (N3) cm 1; MS (70 eV,
‡
nÄ ˆ 2131 (N3) cm 1; MS (70 eV, EI): m/z (%) ˆ 454 (14) [M ], 118 (100);
C23H22N10O (454.50): calcd C 60.78, H 4.88, N 30.82; found C 60.59, H 4.99,
N 30.77.
Bis(2-azidobenzyl)(2-azido-5-methylbenzyl)amine N-oxide (12): Yield:
26%; m.p. 117 ± 1198C (colorless prisms from CHCl3/Et2O); 1H NMR
(300 MHz, CDCl3): d ˆ 2.31 (s, 3H; CH3), 4.21 (s, 2H; CH2), 4.24 (s, 4H;
CH2), 7.05 ± 7.46 (m, 8H), 7.64 (s, 1H), 7.85 (d, J(H,H) ˆ 7.0 Hz, 2H);
13C NMR (75.4 MHz, CDCl3): d ˆ 20.74 (CH3), 64.27 (CH2), 64.46 (CH2),
117.34, 117.47, 122.02 (s), 122.43 (s), 124.65, 130.54, 131.30, 134.41 (s),
136.16, 136.49, 137.03 (s), 139.82 (s); IR (Nujol): nÄ ˆ 2131 (N3) cm 1; MS
‡
EI): m/z (%) ˆ 438 (6) [M ], 91 (100); C23H22N10 (438.50): calcd C 63.00, H
5.06, N 31.94; found C 62.86, H 4.97, N 31.99.
Bis(2-azidobenzyl)(2-azido-5-methylbenzyl)amine (11): Yield: 76%;
1H NMR (200 MHz, CDCl3): d ˆ 2.31 (s, 3H; CH3), 3.51 (s, 2H; CH2),
3.54 (s, 4H; CH2), 6.95 ± 7.29 (m, 8H), 7.36 (s, 1H), 7.54 ± 7.59 (m, 2H);
13C NMR (50.3 MHz, CDCl3): d ˆ 21.10 (CH3), 52.91 (CH2), 52.98 (CH2),
117.88, 117.99, 124.66, 128.08, 128.74, 130.46, 130.81 (s), 130.86 (s), 131.14,
134.27 (s), 135.60 (s), 138.35 (s); IR (film): nÄ ˆ 2136 cm 1; MS (70 eV, EI):
‡
(70 eV, EI): m/z (%) ˆ 440 (12) [M ], 77 (100); C22H20N10O (440.47): calcd
C 59.99, H 4.57, N 31.80; found C 60.11, H 4.48, N 31.67.
‡
m/z (%) ˆ 424 (6) [M ], 77 (100); C22H20N10 (424.47): calcd C 62.25, H 4.75,
(2-Azidobenzyl)(2-azido-5-chlorobenzyl)(2-azido-5-methylbenzyl)amine
N-oxide (14): Yield: 58%; m.p. 83 ± 84oC (colorless prisms from CHCl3/
Et2O); 1H NMR (300 MHz, CDCl3): d ˆ 2.31 (s, 3H; CH3), 4.21 (s, 2H;
CH2), 4.23 (s, 2H; CH2), 4.25 (s, 2H; CH2), 7.00 ± 7.24 (m, 5H), 7.36 (dd,
J(H,H) ˆ 8.5, 2.4 Hz, 1H), 7.42 (t, J(H,H) ˆ 7.9 Hz, 1H), 7.63 (d, J(H,H) ˆ
1.5 Hz, 1H), 7.84 (dd, J(H,H) ˆ 7.8, 1.5 Hz, 1H), 7.93 (d, J(H,H) ˆ 2.5 Hz,
1H); 13C NMR (75.4 MHz, CDCl3): d ˆ 20.83 (CH3), 63.61 (CH2), 64.55
(CH2), 64.64 (CH2), 117.43, 117.57, 118.62, 121.73 (s), 122.12 (s), 124.06 (s),
124.82, 130.07 (s), 130.60, 130.78, 131.51, 134.62 (s), 135.74, 136.24, 136.55,
137.08 (s), 138.42 (s), 139.88 (s); IR (Nujol): nÄ ˆ 2129 (N3) cm 1; MS (70 eV,
N 33.00; found C 62.03, H 4.61, N 33.09.
(2-Azidobenzyl)(2-azido-5-chlorobenzyl)(2-azido-5-methylbenzyl)amine
(13): Yield: 58%; 1H NMR (200 MHz, CDCl3): d ˆ 2.31 (s, 3H; CH3), 3.49
(s, 2H; CH2), 3.51 (s, 2H; CH2), 3.54 (s, 2H, CH2), 6.96 ± 7.27 (m, 8H), 7.49
(dd, J(H,H) ˆ 8.4, 1.8 Hz, 1H), 7.64 (d, J(H,H) ˆ 2.4 Hz, 1H); 13C NMR
(50.3 MHz, CDCl3): d ˆ 19.2 (CH3), 52.65 (CH2), 53.28 (CH2), 53.34 (CH2),
117.97, 118.08, 119.04, 124.69, 127.88, 128.33, 129.00 (s), 130.15 (s), 130.46,
130.75, 131.54, 132.82 (s), 134.32 (s), 135.76 (s), 136.71 (s), 138.52 (s), one
arom CH carbon and one arom (s) carbon were not observed; IR (film):
‡
nÄ ˆ 2129 (N3) cm 1; MS (70 eV, EI): m/z (%) ˆ 458 (21) [M ], 104 (100);
‡
EI): m/z (%) ˆ 474 (41) [M ], 234 (100); C22H19ClN10O (474.91): calcd C
C22H19ClN10 (458.92): calcd C 57.58, H 4.17, N 30.52; found C 57.63, H 4.26,
N 30.41.
55.64, H 4.03, N 29.49; found C 55.47, H 4.19, N 29.40.
General procedure for the preparation of the triphosphazides (15): Two
solutions of the corresponding tris(2-azidobenzyl)amine (1.5 mmol) in
diethyl ether or CH2Cl2 (10 mL) and triphos (1.5 mmol) in diethyl ether
(10 mL) were simultaneously added to a round-bottom flask containing
diethyl ether (15 mL) under nitrogen at room temperature over a period of
30 min with stirring. The resulting mixture was then stirred for 2 h. The
precipitated pale yellow solid was filtered, washed with diethyl ether (3 Â
10 mL), and dried under vacuum.
General procedure for the preparation of tris(2-azidobenzyl)amine N-
oxides: A solution of mCPBA (0.26 g, 1.5 mmol) in CHCl3 (20 mL) was
added over a period of 1 h to a solution of the corresponding tris(2-
azidobenzyl)amine (1.5 mmol) in CHCl3 (25 mL) at 08C. The mixture was
allowed to warm to room temperature in about 4 h with stirring. The
solvent was then removed under reduced pressure and the residue purified
by column chromatography (neutral alumina; CHCl3).
Tris(2-azidobenzyl)amine N-oxide (7a): Yield: 68%; m.p. 113 ± 1158C
(colorless prisms from CHCl3/Et2O); 1H NMR (300 MHz, CDCl3): d ˆ 4.25
(s, 6H; CH2), 7.11 ± 7.20 (m, 6H), 7.42 (td, J(H,H) ˆ 7.7, 1.6 Hz, 3H), 7.82
(dd, J(H,H) ˆ 7.7, 1.3 Hz, 3H); 13C NMR (75.4 MHz, CDCl3): d ˆ 64.23
(CH2), 117.50, 122.17 (s), 124.67, 130.64, 136.15, 139.85 (s); IR (Nujol): nÄ ˆ
Triphosphazide 15a: Yield: 66%; m.p. 254 ± 2568C; 1H NMR (300 MHz,
CDCl3): d ˆ 0.13 (s, 3H; C-CH3), 3.66 (d, J(H,H) ˆ 12.9 Hz, 3H;
CHAHBN), 3.88 (d, J(H,H) ˆ 12.9 Hz, 3H; CHAHBN), 3.92 (m, 3H;
CHAHBP), 4.24 (pseudot, J(H,H), (H,P) ˆ 14.1 Hz, 3H; CHAHBP), 6.90 ±
7.40 (m, 30H), 7.59 (d, J(H,H) ˆ 7.5 Hz, 3H), 7.90 (d, J(H,H) ˆ 8.1 Hz, 3H),
8.05 ± 8.12 (m, 6H); 13C NMR (75.4 MHz, CDCl3): d ˆ 26.36 (brs; CH3),
36.51 (m; CH2P), 40.64 (q, 2J(P,C) ˆ 4.7 Hz; C-CH3), 55.61 (CH2N), 116.71,
‡
2125 (N3) cm 1; MS (70 eV, EI): m/z (%) ˆ 426 (10) [M ], 77 (100);
C21H18N10O (426.44): calcd C 59.15, H 4.25, N 32.84; found C 58.98, H 4.12,
N 32.97.
1
Tris(2-azido-5-methylbenzyl)amine N-oxide (7b): Yield: 87%; m.p. 134 ±
126.27, 127.30, 128.35 (d, J(P,C) ˆ 104.5 Hz; iC-PhP), 128.62 (d, 1J(P,C) ˆ
1
1368C (colorless prisms from CHCl3/Et2O); H NMR (300 MHz, CDCl3):
83.2 Hz; iC-PhP), 128.64 (d, 3J(P,C) ˆ 11.2 Hz; mC-PhP), 128.74 (d,
3J(P,C) ˆ 11.8 Hz; mC-PhP), 130.13 (d, 2J(P,C) ˆ 9.0 Hz; oC-PhP), 130.39,
131.30 (d, 4J(P,C) ˆ 2.9 Hz; pC-PhP), 131.86 (d, 4J(P,C) ˆ 2.3 Hz; pC-PhP),
132.45 (d, 2J(P,C) ˆ 7.8 Hz; oC-PhP), 132.88 (C1), 147.78 (C2); 31P
(121.4 MHz, CDCl3): d ˆ 1.34; IR (Nujol): nÄ ˆ 1437 (C ± P), 1112 (N ±
d ˆ 2.32 (s, 9H; CH3), 4.19 (s, 6H; CH2), 7.06 (d, J(H,H) ˆ 8.1 Hz, 3H; H3),
7.20 (dd, J(H,H) ˆ 8.1, 1.9 Hz, 3H; H4), 7.68 (d, J(H,H) ˆ 1.9 Hz, 3H; H6);
13C NMR (75.4 MHz, CDCl3): d ˆ 20.82 (CH3), 64.47 (CH2), 117.29, 122.41
(s) 131.18, 134.34 (s), 136.50, 136.99 (s); IR (Nujol): nÄ ˆ 2131 (N3) cm 1; MS
‡
‡
(70 eV, EI): m/z (%) ˆ 468 (11) [M ], 91 (100); C24H24N10O (468.52): calcd
P) cm 1; MS (FAB ‡ ): m/z ˆ 1036 [MH ]; C62H57N10P3 (1035.13): calcd C
C 61.53, H 5.16, N 29.89; found C 61.65, H 5.01, N 29.78.
71.94, H 5.55, N 13.53; found C 71.62, H 5.66, N 12.74.
Chem. Eur. J. 1998, 4, No. 12
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
0947-6539/98/0412-2567 $ 17.50+.50/0
2567

M. Alajarín et al.
FULL PAPER
Triphosphazide 15b: Yield: 85%; m.p. 270 ± 2728C (pale yellow prisms
from CHCl3/Et2O); 1H NMR (300 MHz, CDCl3): d ˆ 0.03 (brs, 3H,
CH3), 3.85 (pseudot, J(H,H), (H,P) ˆ 14.0 Hz, 3H; CHAHBP), 4.10 (m, 3H;
CHAHBP), 4.18 (d, J(H,H) ˆ 13.1 Hz, 3H; CHAHBN), 4.96 (d, J(H,H) ˆ
13.1 Hz, 3H; CHAHBN), 6.90 ± 7.43 (m, 30H), 8.05 (d, J(H,H) ˆ 8.4 Hz,
3H), 8.06 ± 8.15 (m, 6H), 9.00 (d, J(H,H) ˆ 7.8 Hz, 3H; H6); 13C NMR
(75.4 MHz, CDCl3): d ˆ 25.66 (brs, CH3), 37.10 (m, CH2P), 40.33 (q,
2J(P,C) ˆ 3.5 Hz, C-CH3), 66.74 (CH2N), 116.05, 126.22, 126.44 (C1), 127.67
(d, 1J(P,C) ˆ 81.6 Hz; iC-PhP), 127.70 (d, 1J(P,C) ˆ 109.3 Hz; iC-PhP),
128.89 (d, 3J(P,C) ˆ 11.1 Hz; mC-PhP), 129.01, 129.03 (d, 3J(P,C) ˆ
10.6 Hz; mC-PhP), 129.98 (d, 2J(P,C) ˆ 9.5 Hz; oC-PhP), 131.77 (d,
4J(P,C) ˆ 3.0 Hz; pC-PhP), 132.15 (d, 2J(P,C) ˆ 7.6 Hz; oC-PhP), 132.21
(d, 4J(P,C) ˆ 2.3 Hz; pC-PhP), 132.48, 147.87 (C2); 31P NMR (121.4 MHz,
CDCl3): d ˆ 1.41; IR (Nujol): nÄ ˆ 1444 (C ± P), 1108 (N ± P) cm 1; MS
(d, J(H,H) ˆ 2.2 Hz, 3H; H6); 13C NMR (75.4 MHz, CDCl3): d ˆ 25.81 (C-
2
CH3), 37.50 (m; CH2P), 40.38 (q, J(P,C) ˆ 3.5 Hz; C-CH3), 65.13 (CH2N),
117.41, 127.36 (C1), 127.41 (d, 1J(P,C) ˆ 81.1 Hz; iC-PhP), 127.42 (d,
1J(P,C) ˆ 108.7 Hz; iC-PhP), 129.11 (d, 3J(P,C) ˆ 11.1 Hz; mC-PhP),
3
2
129.26 (d, J(P,C) ˆ 12.1 Hz; mC-PhP), 129.66, 129.94 (d, J(P,C) ˆ 9.1 Hz;
oC-PhP), 131.93 (C5), 132.15, 132.25 (d, 4J(P,C) ˆ 3.0 Hz; pC-PhP), 132.26
(d, 4J(P,C) ˆ 9.1 Hz; oC-PhP), 132.52 (d, 2J(P,C) ˆ 2.5 Hz; pC-PhP), 146.61
(C2); 31P NMR (121.4 MHz, CDCl3): d ˆ 1.22; IR (Nujol): nÄ ˆ 1438 (C ±
‡
P), 1113 (N ± P); MS (FAB ‡ ): m/z ˆ 1154 [MH ]; C62H54Cl3N10OP3
(1154.47): C 64.51, H 4.71, N 12.14; found C 64.61, H 5.09, N 11.20.
Triphosphazide 15h: Yield: 27%; m.p. 290 ± 291oC; 1H NMR (300 MHz,
CDCl3): d ˆ 0.26 (s, 3H; CH3), 1.71 (s, 9H; Ar-3-CH3), 3.93 (d, J(H,H) ˆ
11.8 Hz, 3H; CHAHBN), 4.25 (brd, J(H,H) ˆ 13.4 Hz, 6H; CHAHBP ‡
CHAHBP), 5.12 (d, J(H,H) ˆ 11.8 Hz, 3H; CHAHBN), 7.01 (t, J(H,H) ˆ
7.5 Hz, 6H), 6.98 ± 7.47 (m, 24H), 7.59 (d, J(H,H) ˆ 7.8 Hz, 3H), 8.03 ±
8.10 (m, 6H); 13C (75.4 MHz, CDCl3): d ˆ 19.09 (Ar-3-CH3), 26.21 (C-
CH3), 37.15 (m; CH2P), 39.80 (q, 2J(P,C) ˆ 3.5 Hz;C-CH3), 64.94 (CH2N),
123.37 (s), 124.24, 127.56 (d, 1J(P,C) ˆ 80.1 Hz; iC-PhP), 127.80 (d, 1J(P,C) ˆ
108.3 Hz; iC-PhP), 128.80 (d, 3J(P,C) ˆ 11.6 Hz; mC-PhP), 128.87 (d,
3J(P,C) ˆ 11.6 Hz; mC-PhP), 130.28 (s), 130.88 (d, 2J(P,C) ˆ 9.6 Hz; oC-
PhP), 132.13 (d, 4J(P,C) ˆ 3.0 Hz; pC-PhP), 132.32 (d, 2J(P,C) ˆ 8.1 Hz; oC-
‡
(FAB ‡ ): m/z ˆ 1052 [MH ]; C62H57N10OP3 (1051.13): calcd C 70.84, H
5.46, N 13.32; found C 69.84, H 5.57, N 12.72.
Triphosphazide 15c: Yield: 98%; m.p. 287 ± 2898C; 1H NMR (300 MHz,
CDCl3): d ˆ 0.13 (s, 3H; C-CH3), 2.34 (s, 9H; ArCH3), 3.66 (d, J(H,H) ˆ
12.8 Hz, 3H; CHAHBN), 3.86 (d, J(H,H) ˆ 12.8 Hz, 3H; CHAHBN), 3.92
(m, 3H; CHAHBP), 4.23 (pseudot, J(H,H), (H,P) ˆ 14.3 Hz, 3H;
CHAHBP), 6.96 (td, J(H,H) ˆ 7.6, 3.1 Hz, 6H), 7.05 (dd, J(H,H) ˆ 8.4,
1.9 Hz, 3H), 7.16 (td, J(H,H) ˆ 7.8, 1.6 Hz, 3H), 7.25 ± 7.44 (m, 18H), 7.80 (d,
J(H,H) ˆ 8.1 Hz, 3H), 8.00 ± 8.20 (m, 6H); 13C NMR (75.4 MHz, CDCl3):
d ˆ 21.20 (ArCH3), 26.43 (C-CH3), 36.60 (m, CH2P), 40.70 (q, 2J(P,C) ˆ
PhP), 132.38, 132.39 (d, 4J(P,C) ˆ 2.5 Hz; pC-PhP), 133.71, 150.96 (C2); 31
P
(121.4 MHz, CDCl3): d ˆ 2.56; IR (Nujol): nÄ ˆ 1440 (C ± P), 1110 (N ±
‡
P) cm 1; MS (FAB ‡ ): m/z ˆ 1095 [MH ]; C65H63N10OP3 (1093.21): calcd C
3
71.41, H 5.81, N 12.81; found C 70.87, H 5.26, N 11.24.
3.5 Hz;C-CH3), 55.62 (CH2N), 116.57, 128.00, 128.67 (d, J(P,C) ˆ 11.6 Hz;
mC-PhP), 128.68 (d, 1J(P,C) ˆ 107.8 Hz; iC-PhP), 128.79 (d, 3J(P,C) ˆ
11.6 Hz; mC-PhP), 128.92 (d, 1J(P,C) ˆ 80.6 Hz; iC-PhP), 130.30 (d,
2J(P,C) ˆ 9.1 Hz; oC-PhP), 130.55, 131.30 (d, 4J(P,C) ˆ 3.0 Hz; pC-PhP),
Triphosphazide 15i: Yield: 41%; m.p. 282 ± 2848C; 1H NMR (300 MHz,
CDCl3): d ˆ 0.12 (s, 3H; C-CH3), 2.32 (s, 6H; ArCH3), 3.65 (d, J (H,H) ˆ
12.5 Hz, 2H; CHAHBN), 3.71 (d, J(H,H) ˆ 12.8 Hz, 1H; CHAHBN), 3.82 ±
4.02 (m, 6H), 4.25 (m, 3H), 6.88 ± 7.43 (m, 30H), 7.63 (d, J(H,H) ˆ 7.5 Hz,
1H), 7.82 (d, J(H,H) ˆ 8.4 Hz, 2H), 7.90 (d, J(H,H) ˆ 7.8 Hz, 1H), 8.10 (m,
6H); 13C NMR (75.4 MHz, CDCl3): d ˆ 21.16 (ArCH3), 26.38 (C-CH3),
4
2
131.84 (d, J(P,C) ˆ 2.0 Hz; pC-PhP), 132.43 (d, J(P,C) ˆ 7.5 Hz; oC-PhP),
132.82 (C5 or C1), 135.90 (C1 or C5), 145.73 (C2); 31P NMR (121.4 MHz,
CDCl3): d ˆ 0.01; IR (Nujol): nÄ ˆ 1442 (C ± P), 1109 (N ± P) cm 1; MS
‡
2
(FAB ‡ ): m/z ˆ 1078 [MH ]; C65H63N10P3 (1077.21): calcd C 72.48, H 5.89,
36.56 (m; CH2P), 40.64 (q, J(P,C) ˆ 3.5 Hz; C-CH3), 55.46 (CH2N), 55.54
N 13.00; found C 72.01, H 5.69, N 12.63.
(CH2N), 55.77 (CH2N), 116.48, 116.72, 126.14, 127.03, 127.7 ± 133.2 , 135.87
(s), 145.63 (s), 145.68 (s), 147.85 (s); 31P NMR (121.4 MHz, CDCl3): d ˆ
0.01, 0.39; IR (Nujol): nÄ ˆ 1438 (C ± P), 1112 (N ± P) cm 1; MS (FAB ‡ ): m/
Triphosphazide 15d: Yield: 95%; m.p. 272 ± 2748C; 1H NMR (300 MHz,
CDCl3): d ˆ 0.06 (s, 3H; C-CH3), 2.32 (s, 9H; ArCH3), 3.80 (pseudot,
J(H,H), (H,P) ˆ 14.3 Hz, 3H; CHAHBP), 4.07 (m, 3H; CHAHBP), 4.14 (d,
J(H,H) ˆ 13.1 Hz, 3H; CHAHBN), 4.89 (d, J(H,H) ˆ 13.1 Hz, 3H;
CHAHBN), 6.96 (td, J(H,H) ˆ 7.7, 3.1 Hz, 6H), 7.10 ± 7.42 (m, 21H), 7.93
(d, J(H,H) ˆ 8.4 Hz, 3H), 8.05 ± 8.13 (m, 6H), 8.85 (s, 3H; H6); 13C NMR
(75.4 MHz, CDCl3): d ˆ 21.34 (ArCH3), 25.79 (C-CH3), 37.40 (m, CH2P),
40.39 (q, 2J(P,C) ˆ 3.5 Hz; C-CH3), 66.69 (CH2N), 116.02, 126.58 (C5 or
C1), 128.14 (d, 1J(P,C) ˆ 109.2 Hz; iC-PhP), 128.16 (d, 1J(P,C) ˆ 81.0 Hz;
iC-PhP), 128.92 (d, 3J(P,C) ˆ 11.6 Hz; mC-PhP), 129.10 (d, 3J(P,C) ˆ
12.1 Hz; mC-PhP), 129.99, 130.10 (d, 2J(P,C) ˆ 9.1 Hz; oC-PhP), 131.78
(d, 4J(P,C) ˆ 3.0 Hz; pC-PhP), 132.16 (d, 4J(P,C) ˆ 2.5 Hz; pC-PhP), 132.27
(d, 2J(P,C) ˆ 7.6 Hz; oC-PhP), 132.67, 136.07 (C1 or C5), 145.91 (C2); 31P
NMR (121.4 MHz, CDCl3): d ˆ 1.44; IR (Nujol): nÄ ˆ 1470 (C ± P), 1108
‡
z ˆ 1064 [MH ]; C64H61N10P3 (1063.19): calcd C 72.30, H 5.78, N 13.17;
found C 72.01, H 5.58, N 12.88.
Triphosphazide 15j: Yield: 88%; m.p. 269 ± 2708C; 1H NMR (300 MHz,
CDCl3): d ˆ 0.04 (s, 3H; C-CH3), 2.36 (s, 6H; ArCH3), 3.76 ± 3.98 (m,
3H), 4.05 ± 4.25 (m, 6H), 4.92 (d, J(H,H) ˆ 12.8 Hz, 2H; CHAHBN), 4.93 (d,
J(H,H) ˆ 12.8 Hz, 1H; CHAHBN), 6.86 ± 7.45 (m, 27H), 7.94 (d, J(H,H) ˆ
8.4 Hz, 2H), 8.05 ± 8.13 (m, 8H), 8.82 (s, 2H), 9.05 (d, J(H,H) ˆ 7.8 Hz,
1H); 13C NMR (75.4 MHz, CDCl3): d ˆ 21.27 (ArCH3), 25.73 (C-CH3),
37.28 (m, CH2P), 40.34 (q, 2J(P,C) ˆ 3.5 Hz; C-CH3), 66.58 (CH2N), 66.70
(CH2N), 66.78 (CH2N), 115.97, 116.06, 126.1 ± 132.6, 136.05 (s), 145.74 (s),
145.86 (s), 148.00 (s); 31P NMR (121.4 MHz, CDCl3): d ˆ 1.36, 1.46; IR
(Nujol): nÄ ˆ 1440 (C ± P), 1112 (N ± P) cm 1; MS (FAB ‡ ): m/z ˆ 1080
‡
(N ± P) cm 1; MS (FAB ‡ ): m/z ˆ 1094 [MH ]; C65H63N10OP3 (1093.21):
‡
[MH ]; C64H61N10OP3 (1079.19): calcd C 71.23, H 5.70, N 12.98; found C
calcd C 71.41, H 5.81, N 12.81; found C 70.80, H 5.67, N 12.55.
70.55; H 5.55, N 12.43.
Triphosphazide 15e: Yield: 42%; m.p. 220 ± 2218C; 1H NMR (300 MHz,
CDCl3): d ˆ 0.15 (s, 3H; CH3), 3.59 (d, J(H,H) ˆ 12.8 Hz, 3H;
CHACHBN), 3.82 (d, J(H,H) ˆ 12.8 Hz, 3H; CHACHBN), 3.92 (m, 3H;
CHACHBP), 4.14 (pseudot, J(H,H), (H,P) ˆ 14.3 Hz, 3H; CHACHBP), 7.03
(td, J(H,H) ˆ 7.5, 3.1 Hz, 6H), 7.18 ± 7.42 (m, 21H), 7.55 (d, J(H,H) ˆ
2.2 Hz, 3H), 7.81 (d, J(H,H) ˆ 8.7 Hz, 3H), 8.00 ± 8.10 (m, 6H); 13C NMR
(75.4 MHz, CDCl3): d ˆ 26.41 (C-CH3), 36.90 (m, CH2P), 40.69 (q,
2J(P,C) ˆ 3.5 Hz; C-CH3), 54.75 (CH2N), 118.11 (C4 or C6), 127.61 (C6
or C4), 127.92 (d, 1J(P,C) ˆ 108.3 Hz; iC-PhP), 128.18 (d, 1J(P,C) ˆ 81.1 Hz;
iC-PhP), 128.90 (d, 3J(P,C) ˆ 11.1 Hz; mC-PhP), 128.98 (d, 3J(P,C) ˆ
11.5 Hz; mC-PhP), 129.69 (C3), 130.21 (d, 2J(P,C) ˆ 9.1 Hz; oC-PhP),
131.83 (d, 4J(P,C) ˆ 3.0 Hz; pC-PhP), 131.97 (C1), 132.24 (d, 4J(P,C) ˆ
2.8 Hz; pC-PhP), 132.38 (d, 2J(P,C) ˆ 7.6 Hz; oC-PhP), 134.01 (C5),
146.35 (d, 4J(P,C) ˆ 1.0 Hz; C2); 31P NMR (121.4 MHz, CDCl3): d ˆ 0.44;
IR (Nujol): nÄ ˆ 1465 (C ± P), 1112 (N ± P) cm 1; MS (FAB ‡ ): m/z ˆ 1138
Triphosphazide 15k: Yield: 57%; m.p. 280 ± 2828C; 1H NMR (300 MHz,
CDCl3): d ˆ 0.12 (s, 3H; C-CH3), 2.32 (s, 3H; ArCH3), 3.59 ± 3.74 (m,
3H), 3.82 ± 4.02 (m, 6H), 4.16 ± 4.32 (m, 3H), 6.85 ± 7.50 (m, 32H), 7.61 (t,
J(H,H) ˆ 8.1 Hz, 2H), 7.81 (d, J(H,H) ˆ 8.4 Hz, 1H), 7.90 (d, J(H,H) ˆ
8.1 Hz, 2H), 8.04 ± 8.20 (m, 4H); 13C NMR (75.4 MHz, CDCl3): d ˆ 21.22
(ArCH3), 26.44 (C-CH3), 36.60 (m; CH2P), 40.72 (q, 2J(P,C) ˆ 3.5 Hz; C-
CH3), 55.50 (CH2N), 55.72 (CH2N), 116.52, 116.74, 126.23, 127.11, 128.0 ±
134.0, 135.96 (s), 145.70 (s), 147.85 (s), 147.91 (s); 31P NMR (121.4 MHz,
CDCl3): d ˆ 0.03, 0.36; IR (Nujol): nÄ ˆ 1438 (C ± P), 1112 (N ± P) cm 1; MS
‡
(FAB ‡ ): m/z ˆ 1050 [MH ]; C63H59N10P3 (1049.16): calcd C 72.12, H 5.67,
N 13.35; found C 71.33, H 5.47, N 13.00.
Triphosphazide 15l: Yield: 75%; m.p. 278 ± 2808C; 1H NMR (300 MHz,
CDCl3): d ˆ 0.03 (s, 3H; C-CH3), 2.36 (s, 3H;ArCH3), 3.79 ± 3.90 (m,
3H), 4.00 ± 4.20 (m, 6H), 4.95 (brd, J(H,H) ˆ 13.0 Hz, 3H), 6.91 ± 7.42 (m,
30H), 7.96 (d, J(H,H) ˆ 8.4 Hz, 1H), 8.00 ± 8.15 (m, 7H), 8.80 (s, 1H), 9.03
(brd, J(H,H) ˆ 7.2 Hz, 2H); 13C NMR (75.4 MHz, CDCl3): d ˆ 21.24
(ArCH3), 25.67 (C-CH3), 37.11 (m; CH2P), 40.31 (q, 2J(P,C) ˆ 3.3 Hz; C-
CH3), 66.62 (CH2N), 66.68 (CH2N), 66.80 (CH2N), 116.03, 116.05, 126.0 ±
‡
[MH ]; C62H54Cl3N10P3 (1138.47): calcd C 65.41, H 4.78, N 12.30; found C
65.40, H 4.61, N 10.97.
Triphosphazide 15 f: Yield: 73%; m.p. 237 ± 2388C; 1H NMR (300 MHz,
CDCl3): d ˆ 0.06 (s, 3H, CH3), 3.75 (pseudot, J(H,H), (H,P) ˆ 14.0 Hz,
3H; CHAHBP), 3.96 ± 4.16 (m, 6H; CHAHBP ‡ CHAHBN), 4.85 (d,
J(H,H) ˆ 12.8 Hz, 3H; CHAHBN), 7.03 (td, J(H,H) ˆ 7.8, 3.1 Hz, 6H),
7.25 ± 7.44 (m, 21H), 7.96 (d, J(H,H) ˆ 9.0 Hz, 3H), 8.00 ± 8.11 (m, 6H), 9.01
133.0, 136.05 (s), 145.73 (s), 147.87 (s), 147.98 (s); 31P NMR (121.4 MHz,
1
CDCl3): d ˆ 1.49, 1.40; IR (Nujol); nÄ ˆ 1438 (C ± P), 1109 (N ± P) cm
;
‡
MS (FAB ‡ ): m/z ˆ 1066 [MH ]; C63H59N10OP3 (1065.16): calcd C 71.04, H
5.58, N 13.15; found C 71.55, H 5.37, N 12.87.
2568
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
0947-6539/98/0412-2568 $ 17.50+.50/0
Chem. Eur. J. 1998, 4, No. 12

Tris(phosphazide)s
2558±2570
1
Triphosphazide 15m/15m': Yield: 60%; H NMR (300 MHz, CDCl3): d ˆ
0.13 (s, 3H; CH3), 2.33 (s, 3H; Ar-5-CH3), 3.50 ± 4.02 (m, 9H; CH2N ‡
CHAHBP), 4.15 ± 4.25 (m, 3H; CHAHBP), 6.94 ± 7.30 (m, 29H), 7.58 ± 7.61
(m, 2H), 7.80 (d, J(H,H) ˆ 8.6 Hz, 2H), 7.89 (d, J(H,H) ˆ 8.1 Hz, 1H),
8.03 ± 8.12 (m, 6H); 13C NMR (75.4 MHz, CDCl3): d ˆ 21.22 (Ar-5-CH3),
chromatographed (silica gel; ethyl acetate/methanol 1:1) to give 2-azido-3-
methylbenzylamine (4d). Yield: 82%.
Preparation of tris(2-azidobenzyl)amines 18 and 23: 2-Azidobenzyl iodide
(1.03 g, 4 mmol) was added to a solution of the corresponding benzylamine
(2 mmol) in dioxane (30 mL), and the mixture heated at reflux temperature
for 4 h with stirring. After cooling to room temperature, an excess of
triethylamine (0.45 g, 4.5 mmol) was added in one go, and the mixture was
stirred for 2 h. The precipitated triethylammonium iodide was separated by
filtration, the dioxane removed under reduced pressure and the residue was
chromatographed (silica gel; ethyl acetate/n-hexane 1:4).
2
26.43 (C-CH3), 36.62 (m; CH2P), 40.69 (q, J(P,C) ˆ 3.5 Hz; C-CH3), 54.98
(CH2N), 55.17 (CH2N), 55.19 (CH2N), 55.35 (CH2N), 55.66 (CH2N), 116.44,
116.59, 116.65, 116.85, 118.07, 118.15, 126.34, 126.37, 133.1 ± 137.0, 134.61 (s),
134.76 (s), 136.11 (s), 136.14 (s), 145.64 (s), 146.38 (s), 146.39 (s), 146.43 (s),
146.44 (s), 147.79 (s), 147.81 (s), 147.84 (s) , 147.86 (s); 31P NMR (121.4 MHz,
CDCl3): d ˆ 0.27, 0.21, 0.14, 0.90, 1.04; IR (Nujol): nÄ ˆ 1438 (C ± P),
Bis(2-azidobenzyl)(2-azido-3-methylbenzyl)amine (18): Yield: 42%;
1H NMR (300 MHz, CDCl3): d ˆ 2.37 (s, 3H; CH3), 3.56 (s, 4H; CH2),
3.66 (s, 2H; CH2), 7.04 ± 7.13 (m, 6H), 7.24 (dt, J(H,H) ˆ 6.9, 2.4 Hz, 2H),
7.40 (m, 1H), 7.56 (dd, J(H,H) ˆ 7.8, 0.9 Hz, 2H); 13C NMR (75.4 MHz,
CDCl3): d ˆ 18.07 (CH3), 52.92 (CH2), 54.71 (CH2), 118.01, 124.66, 125.80,
128.16, 128.19, 130.04, 130.58, 130.70 (s), 132.65 (s), 133.32 (s), 137.15 (s),
138.42 (s); IR (film): nÄ ˆ 2133 (N3) cm 1; MS (70 eV, EI): m/z (%) ˆ 424
1
‡
1111 (N ± P) cm
;
MS (FAB ‡ ): m/z ˆ 1085 [MH ]; C63H58ClN10P3
(1083.60): calcd C 69.83, H 5.39, N 12.93; found C 66.11, H 4.51, N 11.36.
Triphosphazide 15n/15n': Yield: 93%; 1H NMR (300 MHz, CDCl3): d ˆ
0.05 (s, 6H; CH3), 2.36 (s, 3H; Ar-5-CH3), 2.37 (s, 3H; Ar-5-CH3), 3.60 ±
3.90 (m, 6H; CHAHBP), 4.00 ± 4.21 (m, 12H; CHAHBP ‡ CHAHBN), 4.83 ±
5.00 (m, 6H; CHAHBN), 6.93 ± 7.43 (m, 56H), 7.90 ± 8.14 (m, 18H), 8.71 (s,
1H; H6 of Ar-5-CH3), 8.75 (s, 1H; H6 of Ar-5-CH3), 8.94 (d, J(H,H) ˆ
7.8 Hz, 1H; H6 of Ar-5-H), 8.99 (d, J(H,H) ˆ 7.8 Hz, 1H; H6 of Ar-5-H),
9.13 (brs, 2H; H6 of Ar-5-Cl); 13C NMR (75.4 MHz, CDCl3): d ˆ 21.30 (Ar-
5-CH3), 25.77 (C-CH3), 37.40 (m; CH2P), 40.37 (q, 2J(P,C) ˆ 3.0 Hz; C-
CH3), 66.0 ± 67.0 (CH2N), 116.03, 116.12, 117.34, 125.0 ± 133.2, 136.21 (s),
136.27 (s), 145.81 (s), 146.57 (s), 146.67 (s), 147.94 (s), 148.08 (s); 31P NMR
(121.4 MHz, CDCl3): d ˆ 1.73, 1.63, 1.50, 1.37, 0.93, 0.91; IR
(Nujol): nÄ ˆ 1438 (C ± P), 1120 (N ± P) cm 1; MS (FAB ‡ ): m/z ˆ 1100
‡
(13) [M ], 159 (100); C22H20N10 (424.47): calcd C 62.25, H 4.75, N 33.00;
found C 62.51, H 4.42, N 33.17.
Bis(2-azidobenzyl)(2-azido-a-methylbenzyl)amine (23): Yield: 67%;
1H NMR (300 MHz, CDCl3): d ˆ 1.36 (d, J(H,H) ˆ 6.9 Hz, 3H), 3.49 (d,
J(H,H) ˆ 14.2 Hz, 2H), 3.59 (d, J(H,H) ˆ 14.2 Hz, 2H), 4.20 (q, J(H,H) ˆ
6.9 Hz, 1H), 7.01 ± 7.32 (m, 10H), 7.48 (d, J(H,H) ˆ 7.3 Hz, 2H); 13C NMR
(75.4 MHz, CDCl3): d ˆ 16.55 (CH3), 49.41 (CH2), 53.76 (CH), 117.75,
118.34, 124.41, 124.47, 127.80, 128.13, 128.46, 130.54, 131.80 (s), 134.65 (s),
137.98 (s), 138.33 (s); IR (film): nÄ ˆ 2131 (N3) cm 1; MS (70 eV, EI): m/z
‡
[MH ]; C63H58ClN10OP3 (1099.60): calcd C 68.82, H 5.31, N 12.73; found C
‡
(%) ˆ 424 (12) [M ], 77 (100); C22H20N10 (424.47): calcd C 62.25, H 4.75, N
68.23, H 5.54, N 11.42.
33.00; found: C 62.01, H 4.89, N 32.79.
Reaction of triphosphazide 15a with triphenylphosphane: A solution of
triphosphazide 15a (0.20 g, 0.2 mmol) and triphenylphosphane (0.15 g,
0.6 mmol) in CDCl3 (10 mL) was heated at reflux temperature for 5 h and
then cooled to room temperature. The solvent was removed under reduced
pressure, the resulting material was treated with diethyl ether (3 mL), and
the resulting solid then isolated by filtration and recrystallized from CHCl3.
Preparation of bis(2-azidobenzyl)(2-azido-3-methylbenzyl)amine N-oxide
(19): The N-oxide 19 was prepared following the procedure described
above for the preparation of the N-oxides 7, 9, 13, and 15.
Bis(2-azidobenzyl)(2-azido-3-methylbenzyl)amine N-oxide (19): Yield:
83%; 1H NMR (300 MHz, CDCl3): d ˆ 2.47 (s, 3H; CH3), 4.27 (s, 4H;
CH2), 4.36 (s, 2H; CH2), 7.05 ± 7.30 (m, 6H), 7.43 (td, J(H,H) ˆ 8.6, 1.5 Hz,
2H), 7.66 (dd, J(H,H) ˆ 7.5, 1.4 Hz, 1H), 7.85 (dd, J(H,H) ˆ 7.5, 1.4 Hz,
2H); 13C NMR (75.4 MHz, CDCl3): d ˆ 18.28 (CH3), 64.30 (CH2), 65.36
(CH2), 117.58, 122.22 (s), 124.60 (s), 124.77, 125.81, 130.73, 132.45 (s),
132.72, 133.32, 136.17, 138.60 (s), 139.90 (s); IR (film): nÄ ˆ 2119 cm 1; MS
Compound 16 was also prepared by reaction of tris(2-azidobenzyl)amine
6a and triphenylphosphane (3 equiv) in benzene at reflux temperature for
3 h.
Tris[2-(triphenylphosphoranylideneamino)benzyl]amine (16): Yield: 71%;
m.p. 343 ± 3458C (colorless prisms from CHCl3); 1H NMR (300 MHz,
CDCl3): d ˆ 4.23 (s, 6H; CH2), 6.37 (d, J(H,H) ˆ 7.8 Hz, 3H), 6.63 (t,
J(H,H) ˆ 7.2 Hz, 3H), 6.70 (td, J(H,H) ˆ 7.5, 1.5 Hz, 3H), 7.21 ± 7.27 (m,
18H), 7.31 ± 7.37 (m, 9H), 7.75 ± 7.78 (m, 18H), 7.86 (d, J(H,H) ˆ 7.2 Hz,
3H); 13C NMR (75.4 MHz, CDCl3): d ˆ 55.56 (CH2), 117.59, 120.46 (d,
3J(P,C) ˆ 9.9 Hz), 125.16 , 128.32 (d, 3J(P,C) ˆ 12.1 Hz; mC-PhP), 128.33,
131.10 (d, 4J(P,C) ˆ 2.0 Hz; pC-PhP), 132.05 (d, 1J(P,C) ˆ 98.6 Hz; iC-PhP),
‡
(70 eV, EI): m/z (%) ˆ 440 (52) [M ], 160 (100); C22H20N10O (440.47): calcd
C 59.99, H 4.58, N 31.80; found C 60.16, H 4.47, N 31.77.
Preparation of triphosphazides 20 and 21: These compounds were prepared
following the procedure described above for the preparation of the
phosphazides 15.
Triphosphazide 20: Yield: 51%; m.p. 234 ± 2358C; 1H NMR (300 MHz,
CDCl3): d ˆ 0.20 (s, 3H; CH3), 2.55 (s, 3H; Ar-3-CH3), 3.58 ± 4.01 (m, 9H;
CHAHBN ‡ CHAHBP), 4.04 ± 4.41 (m, 3H; CHAHBP), 7.03 ± 7.90 (m, 33H),
7.97 ± 8.12 (m, 8H); 13C NMR (75.4 MHz, CDCl3) d ˆ 20.64 (Ar-3-CH3),
132.54 (d, 2J(P,C) ˆ 9.5 Hz; oC-PhP), 135.47 (d, J(P,C) ˆ 20.5 Hz), 148.81
3
(s); 31P NMR (121.4 MHz, CDCl3): d ˆ 1.74; IR (Nujol): nÄ ˆ 1438 (C ± P),
1109 (N ± P) cm 1; MS (FAB ‡ ): m/z ˆ 1114 [MH ]; C75H63N4P3 (1113.29):
‡
2
26.78 (C-CH3), 36.64 (m; CH2P), 40.80 (q, J(P,C) ˆ 3.5 Hz; C-CH3), 53.75
calcd C 80.91, H 5.70, N 5.03; found C 81.03, H 5.54, N 4.75.
(CH2N), 54.05 (CH2N), 58.58 (CH2N), 116.24 (C6 of Ar-3-H), 116.31 (C6 of
Ar-3-H), 117.97 (C6 of Ar-3-CH3), 125.2 ± 130.3, 134.12 (s), 147.46 (d,
4J(P,C) ˆ 1.5 Hz; C2 of Ar-3-H), 148.02 (d, 4J(P,C) ˆ 1.5 Hz; C2 of Ar-3-H),
148.08 (C2 of Ar-3-CH3); 31P NMR (121.4 MHz, CDCl3): d ˆ 1.33, 0.39;
IR (Nujol): nÄ ˆ 1438 (C ± P), 1112 (N ± P) cm 1; MS (FAB ‡ ): m/z ˆ 1050
Preparation of 2-azido-3-methylbenzylamine (4d): A mixture of 2-azido-3-
methylbenzyl chloride (4.54 g, 25 mmol) and potassium phtalimide (5.56 g,
30 mmol) in dry DMF (30 mL) was stirred at 808C for 12 h. After cooling to
room temperature, the mixture was poured on ice/H2O (500 mL) and the
precipitated solid was isolated by filtration, washed with H2O (2 Â 100 mL),
and air-dried under vacuum. The solid was then recrystallized from CHCl3/
Et2O to give N-(2-azido-3-methylbenzyl)-phthalimide 17 (55%) as color-
less prisms. M.p. 114 ± 1158C; 1H NMR (300 MHz, CDCl3): d ˆ 2.42 (s, 3H;
CH3), 4.93 (s, 2H; CH2), 7.04 ± 7.10 (m, 3H), 7.69 ± 7.72 (m, 2H), 7.82 ± 7.87
(m, 2H); 13C NMR (75.4 MHz, CDCl3): d ˆ 18.00 (CH3), 37.97 (CH2),
123.47, 126.17, 126.83, 129.82 (s), 130.99, 131.74 (s), 132.13 (s), 133.10 (s),
‡
[MH ]; C63H59N10P3 (1049.16): calcd C 72.12, H 5.67, N 13.35; found C
71.68, H 6.05, N 11.61.
Triphosphazide 21: Yield: 52%; m.p. 240 ± 2418C; 1H NMR (300 MHz,
CDCl3): d ˆ 0.01 (s, 3H; CH3), 2.44 (brs, 3H; Ar-3-CH3), 3.80 ± 4.75 (m,
12H; CH2N ‡ CH2P), 6.90 ± 7.45 (m, 30H), 7.76 (brs, 3H), 8.08 ± 8.15 (m,
6H), 8.65 (brs, 2H); 13C NMR (75.4 MHz, CDCl3): d ˆ 23.02 (Ar-3-CH3),
25.81 (C-CH3), 36.20 ± 38.70 (m; CH2P), 40.30 (q, 2J(P,C) ˆ 3.0 Hz; C-CH3),
66.01 (CH2N), 66.77 (CH2N), 117.20, 117.50, 125.01, 125.7 ± 133.0, 148.80 (s);
31P NMR (121.4 MHz, CDCl3): d ˆ 2.12, 1.74, 1.67; IR (Nujol): nÄ ˆ
134.12, 168.05 (s); IR (Nujol): nÄ ˆ 2120 (N3), 1709 (C O) cm 1; MS (70 eV,
ˆ
‡
EI): m/z (%) ˆ 292 (5) [M ], 104 (100); C16H12N4O2 (292.30): calcd C 65.75,
1
‡
H 4.14, N 19.17; found C 65.84, H 4.39, N 18.95.
1438 (C ± P), 1109 (N ± P) cm
;
MS (FAB ‡ ): m/z ˆ 1066 [MH ];
C63H59N10OP3 (1065.16): calcd C 71.04, H 5.58, N 13.15; found C 69.52, H
5.98, N 11.52.
N2H4 ´ H2O (5 mL) was added to a solution of N-(2-azido-3-methylben-
zyl)phthalimide (17, 5.26 g, 18 mmol) in EtOH (75 mL) in one go. The
mixture was stirred at reflux temperature for 3 h. After cooling to room
temperature, NaOH 10% (50 mL) was added and the resulting solution
was extracted with CH2Cl2 (3 Â 50 mL). The combined organic extracts
were washed with brine (100 mL) and dried over anhydrous MgSO4. The
solvent was removed under reduced pressure and the resulting oil was
Acknowledgments: We gratefully acknowledge the financial support of the
Â
Â
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Direccion General de Investigacion Científica y Tecnica (Project no.:
PB95-1019).
Received: April 29, 1998 [F1128]
Chem. Eur. J. 1998, 4, No. 12
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2569

M. Alajarín et al.
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2570
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Chem. Eur. J. 1998, 4, No. 12