Mixed phosphinine-ether macrocycles

Full text of DOI:10.1021/jo001378i

1054
J . Org. Chem. 2001, 66, 1054-1056
Ch a r t 1
Mixed P h osp h in in e-Eth er Ma cr ocycles
Nicolas Me´zailles, Nicole Maigrot, Sylvain Hamon,
Louis Ricard, Franc¸ois Mathey,* and Pascal Le Floch*
Laboratoire “He´te´roe´le´ments et Coordination”, UMR CNRS
7653, Ecole Polytechnique, 91128 Palaiseau Cedex, France
Sch em e 1
lefloch@poly.polytechnique.fr
Received September 18, 2000
In tr od u ction
It is now well established that the replacement of
nitrogen by phosphorus atoms in aromatic structures
causes dramatic changes in the resulting electronic
properties.1 Thus, molecules such as phosphinines show
a poorer σ-donating ability but an enhanced electron
π-accepting power not only with respect to their nitrogen
counterparts, pyridines, but also with respect to phos-
phines. The combination of these two effects proved to
be particularly efficient for the stabilization of reduced
transition metal centers. Though some advances have
been recently achieved in this direction with ligands such
as 2,2′-biphosphinines,2 there is still a lack of phos-
phinine-based structures able to encapsulate transition
metals with various geometries. Two years ago, we
developed a successful synthetic approach toward the
first sp2-hybridized phosphorus macrocycles, the silacalix-
[n]phosphinines (n ) 3 or 4, n meaning the number of
phosphinine subunits).3,4
Sch em e 2
As part of a program aimed at devising access to more
flexible structures having different cavity sizes, we
explored the synthesis of a new class of macrocycles
including two phosphinines subunits and two or four
ether functions.5,6 Herein, we report on these results.
the reactivity of 1,3,2-diazaphosphinines toward silyl-
substituted diynes incorporating one or two ether func-
tions. As previously noted, the presence of silyl groups
at the alkyne moieties is necessary to ensure a complete
regioselectivity in the cycloaddition processes.7 The gen-
eral route of this “one-pot” synthesis is presented in
Scheme 1. In a first step, 1 equiv of the selected diyne is
reacted with 2 equiv of 1,3,2-diazaphosphinine to afford
a bis(1,2-azaphosphinine) intermediate which did not
need to be isolated. In the second step, which has to be
performed under dilute conditions to minimize the for-
mation of linear oligomers, the cavity is closed by reacting
a second equivalent of diyne.
All of our experiments were conducted with the readily
available 4,6-bis(tert-butyl)-1,3,2-diazaphosphinine 1.8
The three diynes 2, 3, and 4 were synthesized in excellent
yields by reacting (phenylethynyl)chlorodimethylsilane9
with water or with the corresponding 1,2- or 1,3-diols in
THF, respectively (Scheme 2). Whereas diynes 3 and 4
were previously unknown, compound 2 had already been
Resu lts a n d Discu ssion
Following a strategy similar to the one devised for the
synthesis of silacalix[n]phosphinines,3 we investigated
(1) For general reviews on phosphinine chemistry, see: (a) Ma¨rkl,
G. In Multiple Bonds and Low Coordination in Phosphorus Chemistry;
Regitz, M., Scherer, O. J ., Eds.; Georg Thieme Verlag: New York, 1990;
p 220. (b) Hewitt, G. G. In Comprehensive Heterocyclic Chemistry II;
Katritzky, A. R., Rees, C. W., Scriven, E. F. V., Eds.; Pergamon: New
York, 1996; Vol. 5, p 639. (c) Dillon, K. B.; Mathey, F.; Nixon, J . F.
Phosphorus: The Carbon Copy; Wiley: Chichester, 1998.
(2) (a) Le Floch, P.; Mathey, F. Coord. Chem. Rev. 1999, 179-180,
771. (b) Rosa, P.; Me´zailles, N.; Ricard, L.; Mathey, F.; Le Floch, P.
Angew. Chem., Int. Ed. Engl. 2000, 39, 1823.
(3) (a) Avarvari, N.; Me´zailles, N.; Ricard, L.; Le Floch, P.; Mathey,
F. Science, 1998, 280, 1587. (b) Avarvari, N.; Maigrot, N.; Ricard, L.;
Mathey, F.; Le Floch, P. Chem. Eur. J . 1999, 5, 2109.
(4) Me´zailles, N.; Avarvari, N.; Maigrot, N.; Ricard, L.; Mathey, F.;
Le Floch, P.; Cataldo, L.; Berclaz, T.; Geoffroy, M. Angew. Chem., Int.
Ed. Engl. 1999, 38, 3194.
(5) For references concerning the synthesis of macrocycles including
phosphorus, see: (a) Pabel, M.; Wild, S. B. In Comprehensive Hetero-
cyclic Chemistry II; Katritsky, A. R., Rees, C. W., Scriven, E. F. V.,
Eds.; Pergamon: New York, 1996; Vol. 9, p 947. (b) Caminade, A.-M.;
Majoral, J . P. Chem. Rev. 1994, 94, 1183.
(6) For references concerning the synthesis of macrocycles including
oxygen atoms (ethers), see: (a) Dietrich, B. In Comprehensive Hetero-
cyclic Chemistry II; Katritsky, A. R., Rees, C. W., Scriven, E. F. V.,
Eds.; Pergamon: New York, 1996; Vol. 9, p 809. (b) Gokel, G. W.;
Fedders, M. F. In Comprehensive Heterocyclic Chemistry II; Katritsky,
A. R., Rees, C. W., Scriven, E. F. V., Eds.; Pergamon: New York, 1996;
Vol. 9, p 863.
(7) For a theoretical discussion concerning the mechanism of Diels-
Alder reactions between 1,2-aza and 1,3,2-diazaphosphinines with
alkynes, see: Frison, G.; Sevin, A.; Avarvari, N.; Mathey, F.; Le Floch,
P. J . Org. Chem. 1999, 5, 2109.
(8) Avarvari, N.; Le Floch, P. Ricard, L.; Mathey, F. Organometallics,
1997, 16, 4089.
(9) (a) Lang, H.; Lay, U. Z. Anorg. Allg. Chem. 1991, 596, 7. (b)
Wrackmeyer, B.; Kehr, G.; Su¨ss, J .Chem. Ber. 1993, 126, 2221.
10.1021/jo001378i CCC: $20.00 © 2001 American Chemical Society
Published on Web 01/16/2001

Notes
J . Org. Chem., Vol. 66, No. 3, 2001 1055
Sch em e 3
molecule presents a center of symmetry and the two
phosphinine rings are located in two parallel planes.
However this particular conformation is not maintained
in solution and 9 as well as 8 and 10 are totally fluxional
(all SiMe2 and CH2 groups of the spacer group being
1
magnetically equivalent in H and 13C NMR).
In summary, we report a one-pot synthesis of a new
class of phosphinine-based macrocycles incorporating
ether-containing linkers of variable length. Future work
will focus on their use in coordination chemistry and
catalysis either as chelate (in the case 8) or as encapsu-
lating ligand (9 and 10).
Exp er im en ta l Section
Sta r tin g Ma ter ia ls a n d Gen er a l P r oced u r es. All reactions
were routinely performed under an inert atmosphere of nitrogen
by using Schlenk techniques and dry deoxygenated solvents. Dry
THF, hexanes, and toluene were obtained by distillation from
Na/benzophenone. Dry Celite was used for filtration. Nuclear
magnetic resonance spectra were recorded on a Bruker AC-200
SY spectrometer operating at 200.13 MHz for 1H, 50.32 MHz
for 13C and 81.01 MHz for 31P. Chemical shifts are expressed in
parts per million downfield from external TMS (1H and 13C) and
85% H3PO4 (31P), and coupling constants are given in hertz. Mass
spectra were obtained at 70 eV with a HP 5989 B spectrometer
coupled a with HP 5890 chromatograph by the direct inlet
method. The following abbreviations are used: s, singlet; d,
doublet; t, triplet; m, multiplet. Elemental analyses were
performed by the “Service d’analyze du CNRS”, at Gif sur Yvette,
France.
Syn th esis of 1,3-Bis(p h en yleth yn yl)tetr a m eth yld isilox-
a n e 2. Water (1 mL, 55.6 mmol) was added dropwise to a
solution of phenylethynyldimethylchlorosilane (5.75 g, 29 mmol)
in THF (50 mL) at room temperature. After 2 h, magnesium
sulfate was added, and the reaction was stirred for 1 h. After
filtration and evaporation of the solvent, diyne 2 was recovered
as a colorless oil that was used without any further purification.
Yield: 3.7 g (78%). For characterizations see ref 10.
Gen er a l P r oced u r e for th e Syn th esis of Diyn es 3 a n d
4. Glycol or 2,2-dimethyl-1,3-propanediol (5.1 mmol) was added
dropwise to a solution of phenylethynyldimethylchlorosilane (2.0
g, 10.30 mmol) in THF at room temperature. After the complete
evaporation of HCl gas, the solvent was evaporated and diynes
3 and 4 were recovered as a colorless oils and used without any
further purification.
1,2-Bis(ph en yleth yn yldim eth ylsiloxy)eth an e 3. Yield: 3.70
g (95%). 1H NMR (CDCl3): δ 0.35 (s, 12H, 2 SiMe2), 3.90 (s, 4H,
CH2-O), 7.28-7.50 (m, 10H, CH of C6H5). 13C NMR (CDCl3): δ
0.7 (2 SiMe2), 65.0 (CH2-O), 92.1 (tCPh), 105.8 (s, tCSi),
123.1-132.6 (C6H5). MS: m/z 378 (M, 100).
synthesized through the reaction of copper(I) phenyl-
ethynilide with 1,3-dichlorotetramethyldisiloxane with a
lower yield (34%).10 New diynes 3 and 4 proved to be
difficult to obtain in pure form either by distillation or
classical solvent extraction. Attempts to purify them by
chromatographic separation resulted in loss of large
amounts of compound (more than 40%). Therefore, the
crude products were used in subsequent steps, their
purity being estimated to 97% by 1H and 13C NMR
spectroscopy.
Reaction of diazaphosphinine 1 with diynes proceeded
cleanly in toluene at 70 °C to afford bis-azaphosphinines
5-7, which were only identified by 31P NMR spectros-
copy. As previously mentioned, these intermediates were
not isolated because of the high reactivity of the PdN
double bond toward moisture. Each compound appears
as a singlet at very similar chemical shifts (δ ) 305.6
ppm for 5, 306.2 ppm for 6 and 306.8 ppm for 7). The
ring-closing step requires high dilution conditions to
minimize the formation of oligomers, and a series of
experiments showed the ideal concentration to be 7 ×
10-3 mol/L. We also found that reduction of the volume
to maintain a steady concentration of reagents is es-
sential for the success of these cyclizations. In each case,
at least 7 days were necessary to achieve a total conver-
sion (Scheme 3).
Due to the presence of siloxy groups, macrocycles 8-10
were found to be moisture sensitive and their purification
by chromatography proved to be difficult (loss of about
30%). Fortunately, they were found to be poorly soluble
in acetone and methanol and thus were easily separated
from oligomers. Macrocycle 8 was recovered with a yield
of 50% and 9 and 10 with yields of 25%. Interestingly,
we noted that formation of 8 is favored with regards to
that of oligomers. Though no mechanistic studies have
been performed yet, we believe that this result is partially
explained by the reduced flexibility of intermediate 5
compared to 6 and 7. Formulations of these new macro-
cycles were confirmed by NMR techniques, mass spec-
troscopy, elemental analysis and X-ray diffraction studies
1,3-Bis(p h en yleth yn yld im eth ylsiloxy)-2,2-d im eth ylp r o-
1
p a n e 4. Yield: 4.11 g (95%). H NMR (CDCl3): δ 0.32 (s, 12H,
2 SiMe2), 0.91 (s, 6H, 2 Me), 3.50 (s, 4H, CH2O), 7.28-7.50 (m,
10H, CH of C6H5). 13C NMR (CDCl3): δ 0.7 (2 SiMe2), 38.0 (s,
Me), 69.6 (CH2O), 92.8 (tCPh), 105.6 (s, tCSi), 123.5-132.7
(C6H5). MS: m/z 420 (M, 100).
Gen er a l P r oced u r e for Syn th eses of Ma cr ocycles 8-10.
Diyne 2, 3, or 4 (1 mmol) was added at room temperature to a
solution of diazaphosphinine 1 (2 mmol) in toluene (10 mL). The
resulting solution was then heated at 70 °C, and the formation
of intermediates 5, 7, or 8 was monitored by 31P NMR spectros-
copy. After 10 h, the reactions were complete, and a second
equivalent of diyne (1 mmol) was added. The volume of the
solution was made up to 120 mL by adding toluene, and the
mixture was heated at reflux. The formation of macrocycles was
monitored by 31P NMR spectroscopy. To maintain a steady
concentration of the intermediate and diyne, small volumes
(approximately 20 mL) of solvent were evaporated each day.
After 7 days, the intermediates had disappeared indicating the
end of the reaction. The resulting mixture was then quickly
filtered through silica gel with toluene as eluent. After evapora-
tion of toluene, addition of acetone (20 mL) to the brown residues
caused precipitation of macrocycles. After filtration and wash-
1
in all cases. As expected, the H and 13C NMR data of
compound 8 show a AXX′ spin-system pattern due to the
proximity of the two phosphinine nucleus (6J (P-P) * 0
Hz). On the contrary in spectra of 9 and 10 no coupling
is observed because of the remoteness of the two subunits.
X-ray diffraction study reveal that, in each case, the
(10) Sugita, H.; Hatanaka, Y.; Hiyama, T. Chem. Lett. 1996, 379.

1056 J . Org. Chem., Vol. 66, No. 3, 2001
Notes
ings with acetone (2 × 5 mL) and methanol (2 × 5 mL),
macrocycles 8-10 were recovered as white powders.
10. Yield: 0.23 g (25%). Mp: 220 °C dec. 31P NMR (CDCl3):
δ 279.7 (s). 1H NMR (CDCl3): δ 0.10 (s, 24H, 4 × SiMe2), 0.90
(s, 12H, Me), 3.60 (s, 8H, 4 × OCH2), 7.30 (s, 2H, H4 of
phosphinines), 7.40-7.50 ((m, 20H, 4 × C6H5). 13C NMR
(CDCl3): δ 1.1 (SiMe2), 22.3 (s, Me), 38.4 (s, CMe2), 69.0 (s,
OCH2), 128.1-129.8 (m, CH of C6H5), 133.1 (d, 3J (C-P) ) 20.1,
8. Yield: 0.38 g (50%). Mp: 220 °C dec. 31P NMR (CDCl3): δ
281.5 (s). 1H NMR (CDCl3): δ 0.08 (s, 24H, SiMe2), 7.40-7.50
(m, 21H, C6H5 and H4 of phosphinines). 13C NMR (CDCl3): δ
2.9 (s, SiMe2), 128.2-131.0 (m, CH of C6H5), 131.6 (virtual t,
AXX′, ΣJ (C-P) ) 23.4, C4 of phosphinines), 146.5 (s, Cipso of
C6H5), 153.3 (virtual t, AXX′, ΣJ (C-P) ) 12.3, C3,5 of phosphin-
ines), 161.2 (AXX′, ΣJ (C-P) ) 195.5, C2,6 of phosphinines). MS:
m/z 757 (M, 100). Anal. Calcd for C42H46O2P2Si4: C, 66.63; H,
6.12. Found: C, 66.48; H, 6.21.
2
C4 of phosphinine), 146.1 (s, Cipso of C6H5), 154.3 (d, J (C-P) )
10.6, C3,5 of phosphinines), 163.9 (d, 1J (C-P) ) 89.9, C2,6 of
phosphinines). MS: m/z 930 (M, 100). Anal. Calcd for C52H66O4P2-
Si4: C, 67.20; H, 7.16. Found: C, 67.12; H, 7.09.
9. Yield: 0.21 g (25%). Mp: 220 °C dec. 31P NMR (CDCl3): δ
Ack n ow led gm en t. The authors thank the CNRS
and the Ecole Polytechnique for support of this work.
1
279.7 (s). H NMR (CDCl3): δ 0.07 (s, 24H, 4 × SiMe2), 3.90 (s,
8H, 4 × OCH2), 7.31-7.37 (m, 22H, 4 × C6H5 and H4 of
phosphinines). 13C NMR (CDCl3): δ 1.5 (s, SiMe2), 64.7 (s,
OCH2), 128.2-129.6 (m, CH of C6H5), 133.5 (d, 3J (C-P) ) 20.6,
Su p p or tin g In for m a tion Ava ila ble: Copies of 1H and 13C
NMR spectra of compounds 3 and 4, X-ray data, and an
ORTEP view of macrocycle 9. This material is available free
of charge via the Internet at http://pubs.acs.org.
2
C4 of phosphinine), 145.4 (s, Cipso of C6H5), 154.5 (d, J (C-P) )
10.9, C3,5 of phosphinines), 163.6 (d, 1J (C-P) ) 89.5, C2,6 of
phosphinines). MS: m/z 846 (M, 100). Anal. Calcd for C46H54O4P2-
Si4: C, 63.57; H, 6.44. Found: C, 63.46; H, 6.38.
J O001378I