Design of neutral, mono- or di-cationic water-soluble trihydrazidophosphoradamantanes

Article abstract of DOI:10.1016/j.tetlet.2006.02.096

The versatile behavior of a trihydrazidophosphoradamantane allowing the synthesis of a variety of neutral, mono- or di-cationic water-soluble molecules of potential interest for biphasic catalysis is reported.

Full text of DOI:10.1016/j.tetlet.2006.02.096

Tetrahedron Letters 47 (2006) 2687–2690
Design of neutral, mono- or di-cationic water-soluble
trihydrazidophosphoradamantanes
Maria Zabłockaa,* and Carine Duhayonb
aCentre of Molecular and Macromolecular Studies, The Polish Academy of Sciences, Sienkiewicza 112, 90-363 Ło´dz´, Poland
bLaboratoire de Chimie de Coordination CNRS, UPR 8241, 205 route de Narbonne, 31077 Toulouse cedex 4, France
Received 19 January 2006; revised 8 February 2006; accepted 16 February 2006
Available online 6 March 2006
Abstract—The versatile behavior of a trihydrazidophosphoradamantane allowing the synthesis of a variety of neutral, mono- or
di-cationic water-soluble molecules of potential interest for biphasic catalysis is reported.
Ó 2006 Elsevier Ltd. All rights reserved.
The success of aqueous two-phase catalysis can be ex-
plained by the fact that water is a cheap and environ-
mentally friendly solvent and by the possibility of
overcoming two basic problems encountered in homoge-
neous catalysis, namely, the separation and subsequent
recycling of the catalyst.1 Among the different classes
of ligands used for this purpose, linear or cyclic phos-
phines occupy a special place because their hydrophilic-
ity can be tuned by grafting a variety of polar groups,
such as ammonium, carbohydrate, phosphonium, phos-
phonate, polyether, hydroxyalkyl, hydroxy, sulfonated
groups, etc. In contrast, very few water soluble cage-like
phosphines have been used in catalysis: the Verkade-
type bases 1 are efficient ligands in a number of organic
reactions2 while 1,3,5-triaza-7-phosphoradamantane 2
(PTA) discovered in 19743 has received renewed interest,
not only in homogeneous aqueous biphasic catalysis,4
but also for medicinal5 and photoluminescence uses.6,7
but with a higher resistance to oxidation and with
enhanced possibilities to tune the solubility in water.
We herein report the synthesis of a set of neutral
mono- or dicationic phosphoradamantanes derived
from trimethyl-4,6,9-thio-5-hexa-1,3,4,6,7,9-phospha-5-
tricyclo[3.3.1.13,7]decane 3a as well as the X-ray
structure determination of one of these phosphorada-
mantanes, the monocationic species 6a.
Compound 3a, a non-water-soluble phosphoradaman-
tane, was prepared according to the literature proce-
dure8 in 80% yield from thiophosphorhydrazide
S@P[N(CH3)NH2]3 and formaldehyde (Scheme 1).
Desulfuration of 3a using classical methods, for exam-
ple, (Me3Si)3SiH9 or P(NMe2)3 did not take place.
10
Reaction of 3a with a large excess of tributylphosphine
gave rise to the expected phosphine 48 but this method,
although efficient, did not afford 4 in a high enough yield
since the separation of 4 from the tributylphosphine
sulfide formed during the reaction and unreacted
H
N
P
P
NH
HN
N
N
N
N
Y
2 PTA
1
H3C
CH3
P
N
N
N
N
H3C
3a Y = S
3b Y = O
N
N
YP(NCH3NH2)3 + HCHO
H3C
We were particularly interested in developing new
water-soluble air-stable phosphines with a phosphorad-
amantane skeleton which, in principle, should present
overall reactivity comparable to classical phosphines
CH3
P
N
N
N
H3C
Ni Raney
N
N
4 THPA
3a
N
*
Scheme 1. Synthesis of phosphorus(III) or (V) adamantanes 3a,b and
4.
Corresponding author. Tel.: +48 42 680 3217; fax: +48 42 684
7126; e-mail: zabloc@bilbo.cbmm.lodz.pl
0040-4039/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2006.02.096

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M. Zabłocka, C. Duhayon / Tetrahedron Letters 47 (2006) 2687–2690
tributylphosphine is tedious. The best method we found
consists of the reduction of 3a with Raney Ni allowing
the isolation of 4 in 80% yield. Remarkably 4, for which
we have proposed the acronym THPA (trihydrazido-
phosphoradamantane), appears to be as water soluble
as its analog PTA, 2.
All attempts to reduce the corresponding oxide 3b which
is in marked contrast to 3a, soluble in water, have failed
up to now. One unique feature of 4 is its ability to be
chemoselectively alkylated (or protonated) at nitrogen
rather than at the phosphorus center. This can be
achieved with a strong alkylating reagent such as
CF3SO3CH3 (Scheme 2). Further, N-alkylation is ther-
modynamically less favorable, as changes in hybridiza-
tion of the nitrogen atoms, induce distortions in the
adamantane backbone decreasing the overall stability.
The water soluble monoalkylated phosphoradamantane
511 was characterized in 31P NMR by a singlet at
103.0 ppm (4, d 31P = 101.8 ppm) while the desymetriza-
tion of the structure due to monoalkylation is clearly
˚
Figure 1. X-ray structure of 6a. Selected bond distances (A) and angles
(deg): P1–S1 = 1.8999(13); P1–N1 = 1.721(3); P1–N2 = 1.674(3);
P1–N3 = 1.648(3); N1–N4 = 1.482(4); N2–N5 = 1.446(4); N3–N6 =
1.449(4); N3–P1–N2 = 104.27(15); N3–P1–N1 = 103.02(15); N2–P1–
N1 = 100.20(14).
1
observed in the H NMR (two types of doublets for
the P–N-CH3 groups) and in the 13C NMR (two dou-
blets for the PNCH3 groups and three singlets for the
CH2 groups). Monomethylation at the nitrogen atom
in the b-position relative to phosphorus was also proved
tane derivatives since alkylation can be envisaged both
at the b nitrogen atom, and at the sulfur of the P@S
unit. Indeed, it has already been demonstrated that
methylation of a P@N–P@S linkage easily occurs on
1
by the H NMR singlet at 2.96 ppm and the singlet at
46.16 ppm in the 13C NMR spectrum.
sulfur leading to ½P@N–PþSðCH3ÞꢀCF3SO3 units.16
ꢁ
Addition of 2 equiv of CF3SO3CH3 to 7 allows the
observation based on 31P NMR of the formation of
the three possible cationic species: the S-methylated
Methylation of 3a and 3b with CF3SO3CH3 also
proceeds smoothly giving rise to new water-soluble
phosphoradamantane monocationic species 6a and 6b
(Scheme 2).12,13 The structure of 6a was fully established
by X-ray diffraction studies (see the supporting informa-
tion for full details14). An ORTEP view is shown in
Figure 1. N-Methylation affects the bond distances asso-
ciated with the phosphorus center with a significant
compound 8 [d 31P = 26.10 (d, JPP = 47.4 Hz), and
2
2
9.32 (d, JPP = 47.4 Hz) ppm], the N-methylated species
9 [d 31P = 64.02 (d, JPP = 64 Hz), and ꢁ4.10 (d,
2
2JPP = 64 Hz) ppm], and the desired dicationic phos-
phoradamantane 10 [d 31P = 28.6 (d, JPP = 58.3 Hz),
2
and 2.75 (d, JPP = 58.3 Hz) ppm]. H and 13C NMR
spectra corroborate the coexistence of these three cat-
ionic species. Unfortunately, their instability prevented
their isolation and all attempts to direct such a reaction
to selectivity failed. Therefore, another strategy was
investigated with the aim of preparing stable and even-
tually water-soluble dicationic species incorporating a
phosphoradamantane skeleton and a [P@N@P]+Xꢁ
unit. Phosphonioimino phosphorane cations [P@N@P]+
have the advantageous property of forming readily
isolable salts of complex anions which are soluble in
organic solvents, making them widely useful in inor-
ganic chemistry.17 Moreover, some of these salts were
recently used as promising catalysts in halogen exchange
reactions (Halex reactions) where chloro- and bromo-
aromatics activated toward nucleophilic substitution
react with a fluoride source to yield the corresponding
fluoroarenes.18,19
2
1
˚
lengthening of the P1–N1 bond (1.7211(3) A), compared
˚
˚
to P1–N2 (1.674(3) A), and P1–N3 (1.648(3) A).
The reactivity of the N-alkylated THPA 5 differs from
that of THPA 4 itself. As an example, the Staudinger
reaction between
5 and the functionalized azide
N3P(S)(OC6H4CHO)2 does not take place even under
forcing conditions while this reaction occurs readily in
2 h at room temperature with 4 leading to the imino-
phosphoradamantane 7 (Scheme 3).15
The latter compound appears to be a good model for
obtaining unprecedented dicationic phosphoradaman-
H3C
CH3
P
N
N
N
N
H3C
CF3SO3
N
N
4 + CF3SO3CH3
CH3
5
Treatment of THPA 4 with Ph3P@NBr 11 (obtained
from the addition of 2 equiv of n-BuLi then Br2 to the
phosphonium salt [(Ph3P–NH2)+Clꢁ] overnight at room
temperature) gave the unique phosphonio iminophos-
phorane 12 in 90% yield after workup.20 The identity
of 12 was established by NMR. 31P NMR revealed the
presence of two characteristic doublets at 4.45 (NPN)
and 21.12 (P(C6H5)3) ppm with 2JPP = 29.6 Hz (Scheme
Y
H3C
CH3
P
N
N
N
H3C
CF3SO3
CH3
N
3a, 3b + CF3SO3CH3
N
N
6a Y = S
6b Y = O
Scheme 2. Selective N-alkylation of phosphoradamantanes 3a,b and 4.

M. Zabłocka, C. Duhayon / Tetrahedron Letters 47 (2006) 2687–2690
2689
S
O
CHO
P
2
N
P
H3C
CH3
N
N
N
H3C
N
N
4 + N3P(S)(OC6H4CHO)2
N
7
2 CF3SO3CH3
CH3
CH3
S
P
N
S
S
O
CHO
P
O
CHO
P
O
CHO
+
2
2
2
N
N
H3C
H3C
CH3
CH3
H3C
CH3
CH3
H3C
H3C
CH3
P
P
P
N
N
N
N
N
N
N
N
N
H3C
N
N
N
N
N
+
N
N
N
N
CF3SO3
CF3SO3
2 CF3SO3
9
10
8
Scheme 3. S- and N-alkylation of the iminophosphoradamantane 7.
H3C
References and notes
N
N
Ph3P
N
P
4 + Ph3P=NBr
N
N
1. For a recent review, see: Pinault, N.; Bruce, D. W. Coord.
Chem. Rev. 2003, 241, 1.
2. Verkade, J. G. Coord. Chem. Rev. 1994, 137, 233.
3. Daigle, D. J.; Pepperman, A. B.; Vail, S. L. J. Heterocycl.
Chem. 1974, 11, 407.
4. For a recent review, see: Phillips, A. D.; Gonsalvi, L.;
Romerosa, A.; Vizza, F.; Peruzzini, M. Coord. Chem. Rev.
2004, 248, 955.
5. See for example: Allardyce, C. S.; Dyson, P. J.; Ellis, D. J.;
Heath, S. L. Chem. Commun. 2001, 1396.
6. Assefa, Z.; McBurnett, B. G.; Staples, R. J.; Fackler, J. P.;
Assamann, B.; Angermaier, K.; Schmidbaur, H. Inorg.
Chem. 1995, 34, 75.
7. Assefa, Z.; Omary, M. A.; McBurnett, B. G.; Mohamed,
A. A.; Patterson, H. H.; Staples, R. J.; Fackler, J. P. Inorg.
Chem. 2002, 41, 6274.
8. Majoral, J. P.; Kraemer, R.; Navech, J.; Mathis, F.
Tetrahedron 1976, 32, 2633; Navech, J.; Kraemer, R.;
Majoral, J. P. Tetrahedron Lett. 1980, 21, 1449; Majoral,
J. P. Synthesis 1978, 8, 557; Jaud, J.; Benhamou, M.;
Majoral, J. P.; Navech, J. Z. Kristallogr. 1982, 160, 69.
9. Romeo, R.; Wozniak, L. A.; Chatgilialoglu, C. Tetra-
hedron Lett. 2000, 41, 9899.
11
Br
N
N
CH3
12
H3C
H3C
N
N
CF3SO3CH3
Ph3P
Br
N P
N
N
CH3
N
N
CH3
CF3SO3
H3C
13
Scheme 4. Synthesis of the water-soluble mono- and di-cationic
[P@N@P] compounds 12 and 13.
4). As expected, monoalkylation of 12 proceeded almost
quantitatively leading to 13, the first example of a dicat-
ionic species bearing a charged PNP unit and an N-
alkylated phosphoradamantane.21 The reaction was
monitored by 31P NMR with the disappearance of the
two doublets due to compound 12 on behalf of two
new doublets at ꢁ2.8 (NPN) and 24.8 (P(C6H5)3) ppm
(2JPP = 35.3 Hz). 1H and 13C NMR spectra corroborate
the formation of 13 with the appearance of new singlets
1
for the N–CH3 group at 3.88 ppm in the H NMR and
´
45.31 ppm in the 13C NMR accompanied with multipli-
city of the other signals (CH3 and CH2 signals) due to
the desymmetrization of the molecule. Remarkably, in
marked contrast with the [P@N@P]+ cations reported
in the literature, 12 was found to be fairly soluble in
water while 13 was only slightly soluble.
10. Omelanczuk, J.; Mikołajczyk, M. J. Am. Chem. Soc. 1979,
101, 7292.
11. Synthesis and characterization of 5: To a solution of 0.10 g
(0.5 mmol) of (CH2NMeN)3P in CH2Cl2 (3 mL) at room
temperature was added 0.082 g (57 lL) of CF3SO3CH3
using a microsyringe. The reaction mixture was stirred for
4 h at rt. Evaporation of the solvent under reduced
pressure afforded the expected compound as a white
powder in 96% yield. 31P{1H}NMR (81 MHz, CDCl3) d
103.0 (s); 1H NMR (200 MHz, CD2Cl2) d 2.86 (d,
3JPH = 15.0 Hz, 6H, CH3), 2.96 (s, 3H, CH3), 3.08 (d,
In summary, we have developed new classes of neutral,
monocationic, and dicationic constraint structures
based on trihydrazidophosphoradamantanes, most of
them being water soluble. These air-stable derivatives
are convenient to prepare, store, and handle22 and open
new possibilities in homogeneous catalysis. These prop-
erties will be illustrated in forthcoming letters.
2
3JPH = 15.0 Hz, 3H, CH3), 5.15 (d, JHH = 11.8 Hz, 3H,
2
CH2), 5.35 (d, JHH = 11.8 Hz, 3H, CH2); 13C NMR
2
(50 MHz, CDCl3) d 35.79 (d, JCP = 14.9 Hz, CH3),
2
38.80 (d, JCP = 19.8 Hz, CH3), 46.16 (s, CH3), 60.24 (s,
CH2), 66.40 (s, CH2), 76.40 (s, CH2), 121.25 (q, JCF
=
319.8 Hz, CF3). Anal. Calcd for C8H18N6O3PSF3: C,
26.23; H, 4.95; N, 22.94. Found: C, 26.16; H, 4.87; N,
22.90.
Acknowledgements
12. Synthesis and characterization of 6a: To a solution of
0.117 g (0.5 mmol) of (CH2NMeN)3P(S) in CH2Cl2 (3 mL)
at room temperature (0.082 g, 57 lL) of CF3SO3CH3 was
added via microsyringe. The reaction mixture was stirred
M.Z. thanks the Ministry of Science and Information
Society Technologies Poland for financial support
(Grant No. 3T09A 158 29).

2690
M. Zabłocka, C. Duhayon / Tetrahedron Letters 47 (2006) 2687–2690
for 2 h at rt, then the solvent was removed under reduced
18. Schanen, V.; Cristau, H. J.; Taillefer, M. WO Patent,
2002, 092226. Chem. Abstr. 137, 386310.
19. Pleschke, A.; Marhold, A.; Schneider, M.; Kolomeitsev,
A.; Ro¨schenthaler, G. V. J. Fluorine Chem. 2004, 125,
1031.
20. Synthesis and characterization of 12: To a suspension
containing 0.157 g (0.5 mmol) of (C6H5)3PNH2Cl in THF
(6 mL) at ꢁ50 °C was added dropwise a solution of
0.625 mL (1 mmol) of n-BuLi (1.6 M solution in hexane).
The reaction mixture was allowed to reach room
temperature and 0.257 mL (0.5 mmol) of Br2 was added.
pressure to afford the expected compound as a white
powder in 95% yield. 31P{1H}NMR (81.015 MHz,
1
CD2Cl2) d 67.42 (s); H NMR (200.133 MHz, CD2Cl2) d
2.95 (d, 3JPH = 13.3 Hz, 6H, CH3), 3.23 (d, 3JPH = 13.2 Hz,
4
3H, CH3), 3.25 (d, JPH = 0.89 Hz, 3H, CH3), 4.61 (d,
2
2JHH = 14.6 Hz, 1H, CH), 4.78 (d, JHH = 14.6 Hz, 1H,
2
CH), 5.30 (d, JHH = 11.5 Hz, 2H, CH2), 5.52 (d,
2JHH = 11.5 Hz, 2H, CH2); 13C NMR (50.323 MHz,
CDCl2) d 31.50 (s, CH3), 35.80 (s, CH3), 47.12 (s, CH3),
3
3
64.90 (d, JCP = 5.9 Hz, CH2), 67.80 (d, JCP = 5.9 Hz,
1
CH2), 76.90 (s, CH2), 120.6 (q, JCF = 320.1 Hz, CF3).
After 1 h,
a
solution of 0.101 g (0.5 mmol) of
Anal. Calcd for C8H18N6O3PS2F3: C, 24.12; H, 4.55; N,
21.10. Found: C, 24.07; H, 4.48; N, 21.19.
(CH2NMeN)3P in 3 mL THF was added via cannula.
The reaction mixture was stirred overnight at room
temperature and the resulting white precipitate was
filtered. The white solid was washed with a 1:1 ether/
THF solution. Compound 12 was obtained as a white
powder in 90% yield. 31P{1H}NMR (101 MHz, CDCl3) d
13. Synthesis and characterization of 6b: To a solution of
0.10 g (0.5 mmol) of (CH2NMeN)3P(O) in CH2Cl2 (3 mL)
at room temperature was added 0.082 g (57 lL) of
CF3SO3CH3 by microsyringe. The reaction mixture was
stirred for 2 h at rt. Removal of the solvent afforded the
expected compound as a white powder in 94% yield.
31P{1H}NMR (101 MHz, CD3CN) d 2.94 (s); 1H NMR
2
2
4.45 (d, JPP = 29.6 Hz, NPN), 21.12 (d, JPP = 29.6 Hz,
P(C6H5)3); 1H NMR (200 MHz, CDCl3) d 2.65 (d,
2
3JPH = 13.05 Hz, 9H, CH3), 4.61 (d, JHH = 12.6 Hz,
3
2
(250 MHz, CD3CN) d 2.86 (d, JPH = 10.7 Hz, 6H, CH3),
3H, CH2), 4.82 (d, JHH = 12.6 Hz, 3H, CH2), 7.67 (m,
3.04 (d, 3JPH = 10.1 Hz, 3H, CH3), 3.13 (d, 4JPH = 1.5 Hz,
15H, CH, C6H5); 13C NMR (63 MHz, CDCl3) d 35.04 (s,
2
3
3H, CH3), 4.34 (d, JHH = 14.2 Hz, 1H, CH), 4.69 (d,
CH3), 66.72 (d, JCP = 5.66 Hz, CH2), 123.10 (d,
2
1
2JHH = 14.2 Hz, 1H, CH), 5.11 (d, JHH = 12.1 Hz, 2H,
1JCP = 103.8 Hz, C, i-C6H5), 125.50 (d, JCP = 108.2 Hz,
2
CH2), 5.27 (d, JHH = 12.1 Hz, 2H, CH2); 13C NMR
C, i-C6H5), 129.51 (d, JCP = 13.2 Hz, CH, C6H5), 130.12
(d, JCP = 13.8 Hz, CH, C6H5), 131.90 (d, JCP = 11.9 Hz,
CH, C6H5), 133.25 (d, JCP = 11.9 Hz, CH, C6H5), 134.31
(63 MHz, CD3CN) d 29.10 (d, 2JCP = 2.5 Hz, CH3), 33.31
(s, CH3), 45.52 (s, CH3), 63.54 (s, CH2), 63.60 (s, CH2),
1
4
4
76.02 (s, CH2), 120.8 (q, JCF = 319.2 Hz, CF3). Anal.
(d, JCP = 3.1 Hz, CH, p-C6H5), 134.75 (d, JCP = 2.5 Hz,
CH, p-C6H5). Anal. Calcd for C24H30N7P2Br: C, 51.62;
H, 5.42; N, 17.56. Found: C, 51.58; H, 5.38; N, 17.60.
21. Synthesis and characterization of 13: To a solution of
0.28 g (0.5 mmol) of 12 in CH2Cl2 (3 mL) at room
temperature was added 0.82 g (56.6 lL) of CF3SO3CH3
using a microsyringe. The reaction mixture was stirred
overnight at rt. Evaporation of the solvent under reduced
pressure afforded the expected compound as a white
powder in 95% yield. 31P{1H}NMR (101 MHz, CDCl3) d
Calcd for C8H18N6O4PSF3: C, 25.13; H, 4.75; N, 21.98.
Found: C, 25.16; H, 4.67; N, 21.82.
14. Crystallographic data (excluding structure factors) for the
structure in this letter have been deposited with the
Cambridge Crystallographic Data Centre as supplemen-
tary publication number CCDC294642.
15. Synthesis and characterization of 7: To a solution of 0.10 g
(0.5 mmol) of (CH2NMeN)3P in 4 mL THF was added
N3P(S)(OC6H4CHO)2 (0.174 g, 0.5 mmol) in 3 mL THF
via cannula at room temperature. The reaction mixture
was stirred at rt for 2 h. After solvent removal under
reduced pressure, the product was obtained as a white
powder in 95% yield. 31P{1H}NMR (101 MHz, CDCl3) d
3.83 (d, 2JPP = 58.15 Hz, P@N), 48.10 (d, 2JPP = 58.15 Hz,
2
2
ꢁ2.8 (d, JPP = 35.3 Hz, NPN), 24.8 (d, JPP = 35.3 Hz,
P(C6H5)3); 1H NMR (250 MHz, CDCl3) d 2.75 (d,
3JPH = 12.4 Hz, 6H, CH3), 3.04 (d, JPH = 12.4 Hz, 3H,
3
2
CH3), 3.88 (s, 3H, CH3), 4.59 (d, JHH = 12.5 Hz, 1H,
2
CH), 4.78 (d, JHH = 12.5 Hz, 1H, CH), 5.43 (d,
P@S), 1H NMR (200 MHz, CD2Cl2)
d
2.81 (d,
2JHH = 12.6 Hz, 2H, CH2), 5.68 (d, JHH = 12.6 Hz, 2H,
2
2
3JPH = 12.7 Hz, 9H, CH3), 4.24 (d, JHH = 13.1 Hz, 3H,
CH2), 7.71 (m, 15H, CH, C6H5); 13C NMR (63 MHz,
2
2
CH2), 4.80 (d, JHH = 13.1 Hz, 3H, CH2), 7.45 (d,
CDCl3) d 30.64 (d, JCP = 3.8 Hz, CH3), 35.09 (s, CH3),
3
3JHH = 8.2 Hz, 4H, C6H4), 7.92 (d, JHH = 8.2 Hz, 4H,
45.31 (s, CH3), 64.26 (s, CH2), 76.34 (s, CH2), 120.4 (q,
C6H4), 9.99 (s, 2H, CHO); 13C NMR (63 MHz, CD2Cl2) d
1JCF = 320.1 Hz, CF3), 122.42 (d, JCP = 86.8 Hz, C,
1
1
34.98 (s, CH3), 66.41 (s, CH2), 122.0 (s, CH, C6H4), 131.17
i-C6H5), 124.5 (d, JCP = 91.8 Hz, C, i-C6H5), 129.7 (d,
(s, CH, C6H4), 133.24 (s, C, C6H4), 156.31 (d, JCP
=
JCP = 14.4 Hz, CH, C6H5), 130.40 (d, JCP = 13.8 Hz, CH,
C6H5), 132.20 (d, JCP = 11.9 Hz, CH, C6H5), 132.92 (d,
JCP = 11.3 Hz, CH, C6H5), 134.82 (d, JCP = 2.5 Hz, CH,
p-C6H5), 135.21 (d, JCP = 3.1 Hz, CH, p-C6H5). Anal.
Calcd for C26H33N7O3P2SBrF3: C, 43.22; H, 4.60; N,
13.57. Found: C, 43.14; H, 4.52; N, 13.48.
8.8 Hz, C, C6H4), 190.80 (s, CHO). Anal. Calcd for
C20H25N7O4P2S: C, 46.07; H, 4.83; N, 18.80. Found: C,
46.12; H, 4.79; N, 18.72.
16. Galliot, C.; Larre, C.; Caminade, A. M.; Majoral, J. P.
Science 1997, 277, 1981; Larre, C.; Caminade, A. M.;
Majoral, J. P. Angew. Chem., Int. Ed. 1997, 36, 596.
17. Ylides and Imines of Phosphorus; Johnson, A. N., Ed.;
John Wiley Sons, 1993; p 452.
22. No cleavage of the P–N bond was detected in all these
experiments confirming the rigidity brought about by the
adamantane skeleton.