Phosphanorbornadienephosphonates as a new type of water-soluble phosphines for biphasic catalysis

Article abstract of DOI:10.1021/jo9521716

The reaction of (phenylethynyl)phosphonates or- phosphonamides with 1-phenyl-3,4-dimethylphosphole at 140°C affords the corresponding α-P(O)-substituted 1-phosphanorbornadienes (1-3). The corresponding PO₃Na₂ salt (5) displays some solubility in water (20 g/L) but is a poor ligand both for the rhodium-catalyzed hydrogenation and hydroformylation of olefinic bonds. The reaction of an unsubstituted ethynylphosphonamide with the same phosphole yields a 3:1 mixture of α- and β-P(O)-substituted 1-phosphanorbornadienes 7 and 8. The β-PO₃Na₂ salt (10) is a good ligand for the hydrogenation of (Z)-α-(N-acetamido)cinnamic acid and displays a high solubility in water (230 g/L). The chelation of rhodium by the α-P(O)-substituted 1-phosphanorbornadienes probably explains the loss of hydrogenation efficiency for [RhL₂]^- when L = 5.

Full text of DOI:10.1021/jo9521716

J . Org. Chem. 1996, 61, 3531-3533
3531
P h osp h a n or bor n a d ien ep h osp h on a tes a s a New Typ e of
Wa ter -Solu ble P h osp h in es for Bip h a sic Ca ta lysis
Ste´phane Lelie`vre, Franc¸ois Mercier, and Franc¸ois Mathey*
Laboratoire “He´te´roe´le´ments et Coordination” URA CNRS 1499, DCPH, Ecole Polytechnique,
91128 Palaiseau Cedex, France
Received December 6, 1995X
The reaction of (phenylethynyl)phosphonates or- phosphonamides with 1-phenyl-3,4-dimethylphos-
phole at 140 °C affords the corresponding R-P(O)-substituted 1-phosphanorbornadienes (1-3). The
corresponding PO3Na2 salt (5) displays some solubility in water (20 g/L) but is a poor ligand both
for the rhodium-catalyzed hydrogenation and hydroformylation of olefinic bonds. The reaction of
an unsubstituted ethynylphosphonamide with the same phosphole yields a 3:1 mixture of R- and
â-P(O)-substituted 1-phosphanorbornadienes 7 and 8. The â-PO3Na2 salt (10) is a good ligand for
the hydrogenation of (Z)-R-(N-acetamido)cinnamic acid and displays a high solubility in water (230
g/L). The chelation of rhodium by the R-P(O)-substituted 1-phosphanorbornadienes probably
explains the loss of hydrogenation efficiency for [RhL2]+ when L ) 5.
1-Phosphanorbornadienes have shown excellent quali-
ties as ligands in the rhodium-catalyzed hydrogenation1
and hydroformylation2 of alkenes. In view of the growing
academic and industrial interest in biphasic catalysis,3
water-soluble versions of these phosphanorbornadienes
represent a logical further development. In line with
this, the para-sulfonation of the phenyl substituents of
2,3,6-triphenyl-4,5-dimethyl-1-phosphanorbornadiene has
produced the so-called NORBOS which shows an out-
standing activity in the biphasic hydroformylation of
propene.4 We have decided to investigate another pos-
sible route to such species which involves the introduction
of the water-solubilizing functionality during the con-
struction of the bicyclic system. For synthetic conven-
ience, we have selected the phosphonate functionality
which has recently been introduced5,6 as a promising
alternative to the ubiquitous sulfonate group.
bond couplings, see later. Furthermore, the 13C spectra
show characteristic resonances for the C2 carbons as
doublets of doublets, e.g., for 3, δ C2 143.19, J (C-P) )
155 and 45.5 Hz (CDCl3). The acid hydrolysis of 2 or 3
quantitatively produces the expected phosphonic acid 4
whose sodium salt 5 is moderately water-soluble (20 g/L)
(eq 2). In spite of this rather poor solubility, we noticed
1
Resu lts a n d Discu ssion
Since the synthesis of 1-phosphanorbornadienes in-
volves the [4 + 2] cycloaddition of a transient 2H-
phosphole with an alkyne,7,8 we first decided to study the
reaction of various (phenylethynyl)phosphonic acid de-
rivatives with the transient 2-phenyl-3,4-dimethyl-5H-
phosphole as produced by thermal isomerization of
1-phenyl-3,4-dimethylphosphole (eq 1). The reaction
almost exclusively produces the phosphanorbornadiene
having the phosphoryl group located on C2. This regi-
oselectivity is demonstrated by the 31P NMR spectra
which display AX systems with J (A-X) values in the
range of 58-67 Hz, i.e., strictly incompatible with three-
that 5 is quantitatively extracted by water from a
saturated toluene solution (solubility ca. 10 g/L at 50 °C).
Thus, 5 was potentially of some interest as a substitute
to the sodium salt of triphenylphosphinemonosulfonic
acid which forms the basis of the new oxo process
developed by Union Carbide for the hydroformylation of
higher olefins.9 Consequently, we performed some pre-
liminary experiments in order to check the catalytic
activity of [RhL2]+ (L ) 1-3, 5) in the hydrogenation of
(Z)-R-(N-acetamido)cinnamic acid or 1-methylcyclohexene
(rt, p(H2) ) 3 bar, catalyst: substrate ) 1:100, THF for
1-3, water/toluene (1/1) or MeOH/H2O (1/4) for 5). In
all cases, the results were poor or extremely poor, in
contrast to the high activity observed for the nonfunc-
tional 1-phosphanorbornadiene 6.1 Poor results were also
observed in the hydroformylation of 1-hexene as cata-
lyzed by the [Rh(CO)2Cl]2 + 2L (L ) 5) systems. Since
X Abstract published in Advance ACS Abstracts, April 15, 1996.
(1) Mathey, F.; Neibecker, D.; Bre`que, A. (SNPE), Fr. Pat. 25 88 197,
Oct 3, 1985; Chem. Abstr. 1987, 107, 219468v.
(2) Neibecker, D.; Reau, R. Angew. Chem., Int. Ed. Engl. 1989, 28,
500.
(3) Herrmann, W. A.; Kohlpaintner, C. W. Angew. Chem., Int. Ed.
Engl. 1993, 32, 1524.
(4) Herrmann, W. A.; Kohlpaintner, C. W.; Manatsberger, R. B.;
Bahrmann, H.; Kottmann, H. J . Mol. Catal. A 1995, 97, 65.
(5) Ganguly, S.; Mague, J . T.; Roundhill, D. M. Inorg. Chem. 1992,
31, 3500.
(6) Schull, T. L.; Fettinger, J . C.; Knight, D. A. J . Chem. Soc., Chem.
Commun. 1995, 1487.
(7) Mathey, F.; Mercier, F.; Charrier, C.; Fischer, J .; Mitschler, A.
J . Am. Chem. Soc. 1981, 103, 4595.
(8) Laporte, F.; Mercier, F.; Ricard, L.; Mathey, F. Bull. Soc. Chim.
Fr. 1993, 130, 843.
(9) Haggin, J . Chem. Eng. News 1995, April 17, 25.
S0022-3263(95)02171-2 CCC: $12.00 © 1996 American Chemical Society

3532 J . Org. Chem., Vol. 61, No. 10, 1996
Lelie`vre et al.
we suspected that the catalytic cycles were blocked by
the formation of P,P(O)-chelates, we investigated more
Exp er im en ta l Section
General experimental information is identical to that previ-
ously reported.11 Phenylacetylene, (trimethylsilyl)acetylene,
(Z)-R-(N-acetamido)cinnamic acid, 1-hexene, and 1-methylcy-
clohexene were purchased from Aldrich. The 1-phenyl-3,4-
dimethylphosphole,12 (Et2N)2P(O)Cl,13 [O(CH2CH2)2N]2 P(O)-
precisely the reaction of 3 with [Rh(COD)2]+PF6 In 3,
-
.
the 31P parameters are δ(P) -6, δ(PdO)+22, J (P-P) )
58 Hz (CDCl3). The IR (PdO) stretching vibration occurs
at 1198 cm-1 (CH2Cl2). In the 1:1 rhodium complex, both
31P resonances are significantly shifted downfield and
P‚‚‚Rh couplings appear: δ(P) +35.5, δ(PdO) +38.5,
Cl,14 diethyl (phenylethynyl)phosphonate,15 N,N,N,N-tetra-
- 17
ethylethynylphosphinamine16 [Rh (COD)2]+ PF6
,
and [Rh-
1
2
(CO)2 Cl]218 were prepared according to literature procedures.
Dieth yl (4,5-Dim eth yl-3,6-d ip h en yl-1-p h osp h a n or bor -
n a d ien -2-yl)p h osp h on a te (1). A mixture of (phenylethynyl)-
phosphonate (2.5 g, 10.6 mmol) and phosphole (2.0 g, 10.6
mmol) was heated at 150 °C for 3 h in a sealed tube. The oily
product was chromatographed with 50/50 CH2Cl2/AcOEt as
eluent to yield a yellow oil (90% yield): 31P NMR (CDCl3) δ
18.0 (d, J ) 67.4 Hz), -7.6 (d, J ) 67.4 Hz); 1H NMR (CDCl3)
δ 0.98 (t, J ) 7.1 Hz, 3H), 1.12 (t, J ) 7.1 Hz, 3H), 1.32 (d, J
) 1.2 Hz, 3H), 2.08 (s, 3H), 2.15 (m, 2H), 3.70 (m, 2H), 3.9 (m,
2H); 13C NMR (CDCl3) δ 66.0, 73.5 (dd, J ) 6.0 Hz and 18.0
Hz), 140.5 (dd, J ) 41.6 Hz and 196.0 Hz), 182.48 (d, J ) 9.7
Hz); mass spectrum m/ z 426 (M+, 7), 239 (M - C12H12P, 100).
N,N,N,N-Tetr a eth yl(4,5-d im eth yl-3,6-d ip h en yl-1-p h os-
p h a n or bor n a d ien -2-yl)p h osp h on a m id e (2). A mixture of
alkynylphosphonamide (7.7 g, 0.03 mmol) and phosphole (5.6
g, 0.03 mmol) was heated at 140 °C for 15 min in a sealed
tube. Flash chromatography using 50/50 EtOAc/CH2Cl2 as
eluent gave 10.6 g of a yellow oil (80% yield): 31P NMR (CDCl3)
δ -6.5 (d, J ) 42 Hz), 25.5 (d, J ) 42 Hz); 1H NMR (CDCl3) δ
0.7 (t, J ) 7.2 Hz, 4H), 1.2 (s, 3H), 2.0 (m, 2H), 2.1 (s, 3H), 2.6
(m, 6H), 2.9 (m, 6H). 13C NMR (CDCl3) δ 66.4, 74.5 (dd, J )
4.6 Hz and 13.7 Hz), 146.0 (dd, J ) 44.3 Hz and 152.6 Hz),
179.8 (d, J ) 8.5 Hz); mass spectrum m/ z (relative intensity)
480 (M+, 6), 293 (M - C12H12P, 100).
J (P-P) ) 82.8 Hz, J (P-Rh) ) 155.7 Hz, J (P-O-Rh)
) 7.8 Hz. The IR (PdO) band also shifts to lower
frequency but is difficult to assign. These results fit quite
well the literature data on P,P(O)-chelates of Rh(I).10 For
an Rh:L ratio of 1:2, similar observations are made but
the precise data are more difficult to collect due to the
formation of diastereomeric complexes.
The detrimental effect of the R-P(O) groups on the
catalytic activity led us to investigate the synthesis of
the â-substituted phosphonate derivatives of 1-phospha-
norbornadienes. The reaction of an unsubstituted ethy-
nyl-phosphonamide with the same transient 2H-phosp-
hole as used previously yields a mixture of the two
possible regioisomers with a R/â ratio of 3:1 (eq 3). The
(4,5-Dim eth yl-3,6-d ip h en yl-1-p h osp h a n or bor n a d ien -2-
yl)p h osp h on a m id e (3). The product was prepared by the
same procedure as for 2. 3: white solid recrystallized in 80/
20 hexane/toluene (85% yield, mp 163 °C); 31P NMR (CDCl3)
δ -6 (d, J ) 58 Hz), 22 (d, J ) 58 Hz); 1H NMR (CDCl3) δ 1.27
(s, 3H), 2.10 (s, 3H), 2.15 (m, 2H), 2.66 (m, 4H), 2.93 (m, 4H),
3.21 (m, 4H), 3.49 (m, 4H); 13C NMR (CDCl3) δ 66.8 (dd, J )
6.3 Hz and J ) 19.5 Hz), 74.3 (dd, J ) 5.5 Hz and J ) 15.0
Hz), 143.2 (dd, J ) 45.5 Hz and 154.9 Hz), 183.1 (d, J ) 9.3
Hz); mass spectrum m/ z (relative intensity) 508 (M+, 3), 321
(M+ - C12H12P, 100). Anal. Calcd for C28H34O3N2P2: C, 66.1;
H, 6.73; N, 5.50; P, 12.18. Found: C, 65.97; H, 6.78; N, 5.28;
P, 11.59.
two regioisomers are easily separated by chromatography
on silica gel. The 31P spectrum of 7 displays a charac-
teristic AX spectrum, δA -4.6, δX +26.0, J (A-X) ) 49
Hz, indicative of an R-substitution whereas 8 displays
two singlets at -22.1 and + 26.1 (CDCl3). The hydrolysis
of 8 leads to the corresponding acid 9 whose sodium salt
10 is highly soluble in water (230 g/L) (eq 4). Using
(4,5-Dim eth yl-3,6-d ip h en yl-1-p h osp h a n or bor n a d ien -2-
yl)p h osp h on ic Acid (4). A mixture of 2 (2.5 g, 5.6 mmol)
and 3 N HCl (1 mL) in THF (15 mL) was heated at 70 °C for
18 h. The solution was concentrated, and the product was
extracted with CH2Cl2. It was recrystallized from 80/20
hexane/toluene to give a white solid (90% yield, mp 150 °C);
31P NMR (CDCl3) δ -10.5 (d, J ) 73.0 Hz), 18.4 (d, J ) 73.0
1
Hz); H NMR (CDCl3) δ 1.25 (3H), 2.0 (3H), 2.06 (m, 2H); 13C
ligand 10 under the same conditions as those previously
described for 5, (Z)-R-(N-acetamido)cinnamic acid is
quantitatively hydrogenated in 1 h at rt (note that no
hydrogenation is observed with 5). Our hypothesis on
the freezing of the catalytic cycle due to the chelation of
rhodium by the R-P(O) group of 5 is thus fully confirmed.
The improvement is less impressive in the hydroformy-
lation of 1-hexene as catalyzed by the [Rh(CO)2Cl]2 + 2L
(L ) 10) system. Using the following conditions, 80 °C,
p(H2) ) 10 bar, p(CO) ) 10 bar, catalyst:substrate )
1:100, water/toluene (1/1), we found that 10 is indeed
better than 5. Total yield of aldehydes: 89% (10) vs 66%
(5). The normal/iso ratio is almost the same 0.88 (10) vs
1 (5). In that case, the potential P(O)-chelation seems
to have a less significant effect on the catalytic cycle. This
may be due to the higher temperature used for the
hydroformylation experiments.
NMR (acetone-d6) δ 67.5, 75.0 (dd, J ) 5.5 Hz and J ) 16.8
Hz), 143.0 (dd, J ) 41.4 Hz and J ) 196.1 Hz), 180.6 (d, J )
10.2 Hz). Anal. Calcd for C20H20O3P2: C, 64.86; H, 5.44; P,
16.72. Found: C, 64.60; H, 5.49; P, 16.55.
Disod iu m (4,5-Dim eth yl-3,6-d ip h en yl-1-p h osp h a n or -
bor n a d ien -2-yl)p h osp h on a te (5). A solution of NaOH (0.5
N, 20 mL) was added to a solution of phosphonic acid 4 (1.85
g, 5 mmol) in CH2Cl2 (10 mL) and shaked for 5 min. After
decantation the water layer was separated and concentrated.
A white solvated solid crystallized. 5: 31P NMR (D2O) δ -8.8
(d, J ) 34 Hz), 8.7 (d, J ) 34 Hz); 1H NMR (D2O) δ 0.92 (3H),
(11) Laporte, F.; Mercier, F.; Ricard, L.; Mathey, F. J . Am. Chem.
Soc. 1994, 116, 3306.
(12) Breque, A.; Mathey, F.; Savignac, P. Synthesis 1981, 983.
(13) Cowley, A. H.; Pinnell, R. P. J . Am. Chem. Soc. 1965, 87, 4454.
(14) Ning, R. Y.; Fryer, R. I.; Madan, P. B.; Sluboski, B. C. J . Org.
Chem. 1976, 41, 2720.
(15) Chatta, M. S.; Aguiar, A. M. J . Org. Chem. 1971, 36, 2719.
(16) Fluck, E.; Kuhm, P. Phosphorus Sulfur Silicon 1989, 42, 123.
(17) Schrock, R. R.; Osborn, J . J . Am. Chem. Soc. 1971, 93, 3089.
(18) Mc Cleverty, J . A.; Wilkinson, G. Inorg. Synth. 1966, 8, 211.
(10) Wegman, R. W.; Abatjoglou, A. G.; Harrison, A. M. J . Chem.
Soc., Chem. Commun. 1987, 1891.

Water-Soluble Phosphines for Biphasic Catalysis
J . Org. Chem., Vol. 61, No. 10, 1996 3533
1.7 (3H), 1.9 (m, 2H); 13C NMR (D2O) δ 67.1, 72.8 (dd, J ) 4.4
Hz and J ) 14.0 Hz), 149.1 (dd, J ) 37.8 Hz and J ) 170.8
Hz). Anal. Calcd for C20H18Na2P2O3‚7 H2O: C, 44.48; H, 5.92;
P, 11.48. Found: C, 44.25; H, 5.51; P, 11.81.
(dd, J ) 47.2 Hz and J ) 149.4 Hz), 171.5 (d, J ) 7.3 Hz);
mass spectrum m/ z (relative intensity): 404 (M+, 16), 191 (M+
- C14H14P, 100).
(4,5-Dim eth yl-6-p h en yl-1-p h osp h a n or bor n a d ien -3-yl)-
p h osp h on ic Acid (9). This compound was obtained as an
oil by following the same procedure as for 4. 9: 31P NMR
N,N,N,N-Tetr a eth yl(4,5-d im eth yl-6-p h en yl-1-p h osp h a -
n or bor n a d ien -2-yl (a n d 3-yl))p h osp h on a m id e (7 a n d 8).
A mixture of ethynylphosphonamide (3.0 g, 14 mmol) and
phosphole (2.6 g, 14 mmol) was heated at 140 °C for 15 min.
The brown oil was chromatographed with 1/1 toluene/AcOEt
as eluent to give 8 as an oil (1.1 g, 18% yield). 8: 31P NMR
1
(CDCl3) δ -20.0, 17.5; H NMR (CDCl3) δ 1.72 (s, 3H), 1.96
(m, 5H), 8.0 (dd, J ) 14.8 Hz and J ) 43.9 Hz); 13C NMR
(CDCl3) δ 68.3, 70.7 (dd, J ) 5.7 Hz and J ) 18.5 Hz), 158.2
(d, J ) 185 Hz), 160.9 (dd, J ) 6.3 Hz and J ) 37.0 Hz).
1
(CDCl3) δ -22.1 and 26.1; H NMR (CDCl3) δ 1.0 (t, J ) 7.2
Disod iu m (4,5-Dim et h yl-6-p h en yl-1-p h osp h a n or b or -
Hz, 6H), 1.12 (t, J ) 7.2 Hz, 6H), 1.81 (s, 3H), 2.0 (m, 2H),
2.08 (s, 3H), 2.92 (m, 4H), 3.10 (m, 4H), 7.60 (dd, J ) 12.8 Hz
and J ) 44.3 Hz); 13C NMR (CDCl3) δ 67.3 (d, J ) 8.2 Hz),
71.7 (dd, J ) 4.8 Hz and J ) 16.0 Hz), 158.0 (dd, J ) 4.6 and
J ) 36.4 Hz), 162.1 (dd, J ) 4.6 Hz and J ) 146.6 Hz); mass
n a d ien -3-yl)p h osp h on a te (10). This salt was obtained as
1
a solvate (see 5). 31P NMR (D2O) δ -24.0 and 7.6; H NMR
(D2O) δ 1.6 (3H), 1.8 (m, 2H), 1.9 (3H); 13C NMR (D2O) δ 70.9,
72.9 (dd, J ) 5.0 Hz and 15.0 Hz), 150.2 (dd, J ) 7.2 Hz and
J ) 27.7 Hz), 171.1 (d, J ) 163.5 Hz).
spectrum m/ z (relative intensity) 404 (M+, 45), 286 (M+
-
C4H20ONP, 100). Anal. Calcd for C22H34ON2P2: C, 65.32; H,
8.47; N, 6.92; P, 15.31. Found: C, 65.11; H, 8.18; N, 6.78; P,
14.93.
Then with EtOAc as eluent 7 was obtained as an oil (3.3 g,
54% yield): 31P NMR (CDCl3) δ -4.6 (d, J ) 49.2 Hz), 26.0 (d,
J ) 49.2 Hz); 1H NMR (CDCl3) δ 0.78 (t, J ) 7.0 Hz, 6H), 1.07
(t, J ) 7.0 Hz, 6H), 1.61 (s, 3H), 1.98 (m, 5H), 2.73 (m, 4H),
3.13 (m, 4H), 7.99 (dd, J ) 6.5 Hz and J ) 12.5 Hz); 13C NMR
(CDCl3) δ 67.3, 68.9 (dd, J ) 5.0 Hz and J ) 14.1 Hz), 151.6
Su p p or tin g In for m a tion Ava ila ble: Additional prepara-
tions and copies of NMR spectra (17 pages). This material is
contained in libraries on microfiche, immediately follows this
article in the microfilm version of the journal, and can be
ordered from the ACS; see any current masthead page for
ordering information.
J O9521716