New water-soluble diamine complexes as catalysts for the hydrogenation of ketones under hydrogen pressure

Article abstract of DOI:10.1002/(SICI)1099-0690(199907)1999:7<1745::AID-EJOC1745>3.0.CO;2-B

New water-soluble rhodium and iridium complexes of 2,2'-bipyridines, functionalized with PO₃Na₂ groups, show very good catalytic activities in the reduction of various substituted acetophenones under hydrogen pressure in basic aqueous media. No significant loss of catalyst activity is observed after one use.

Full text of DOI:10.1002/(SICI)1099-0690(199907)1999:7<1745::AID-EJOC1745>3.0.CO;2-B

FULL PAPER
New Water-Soluble Diamine Complexes as Catalysts for the Hydrogenation of
Ketones Under Hydrogen Pressure
[a]
[a]
[a]
[a]
[a]
´
´
Virginie Penicaud, Celine Maillet, Pascal Janvier, Muriel Pipelier, and Bruno Bujoli*
Keywords: 2,2Ј-Bipyridines / C2-symmetric diamines / Sodium phosphonate / Water-soluble catalyst / Hydrogenation
New water-soluble rhodium and iridium complexes of 2,2Ј-
bipyridines, functionalized with PO3Na2 groups, show very
good catalytic activities in the reduction of various
substituted acetophenones under hydrogen pressure in basic
aqueous media. No significant loss of catalyst activity is
observed after one use.
Catalyst recovery and recycling is an important concern
in relation to chemical processes that are homogeneously
catalyzed by expensive transition metal complexes. For this
reason, much effort has been directed towards the synthesis
of new water-soluble catalytic species, the principal aim be-
ing to gain access to reusable catalytic systems that can be
easily separated from the reaction products by simple ex-
traction of the aqueous phase with an organic solvent. To
the best of our knowledge, most of the attention has been
focused on tertiary phosphanes,[1] with TPPTS (triphenyl-
phosphanetrisulfonate sodium salt) remaining the most
Scheme 1. Hydrosoluble ligands tested for the reduction of ketones
Precursors 1 and 2 were prepared as we have described
previously[7] (for details, see Experimental Section). Com-
pound 3 was synthesized by reaction of (1R,2R)-diaminocy-
clohexane with the functionalized isocyanate prepared in
two steps (Scheme 2) from diethyl 4-nitrophenylphosphon-
ate.[8] The phosphonate groups were then converted into
their acidic form under mild conditions using McKennaЈs
method.[9]
widely used. A wide variety of polar functional substituents
ϩ
[e.g. SO3Na, OSO3Li, CO2Na, OH, PMe3ϩ, NMe3
,
P(O)(ONa)2, polyethers][2] have been incorporated in order
to render the desired ligands water-soluble. Among these,
the disodium phosphonate moiety is of particular interest
since the reactivity of this group towards a wide range of
metal salts, to yield metal phosphonates,[3] also offers the
possibility of heterogenizing catalytic complexes as phos-
phonate-based organic/inorganic hybrid solids, as first
shown by our group in the (porphyrin)manganese(III)
series.[4]
The use of various N-containing ligands (based for ex-
ample on 2,2Ј-bipyridines,[5aϪ5c] phenanthrolines,[5d] or C2-
symmetric diamines[5eϪ5h]) as an alternative to phos-
phanes[6] in the asymmetric hydrogenation of prochiral ke-
tones is well documented in the literature, mainly in the
context of transfer hydrogenation. To the best of our
knowledge, however, there have been no reports of the prep-
aration of water-soluble diamine complexes that might al-
low this reaction to be carried out under hydrogen pressure
in water. In this context, we have recently reported in a pre-
liminary communication[7] the facile synthesis of 2,2Ј-bi-
pyridine-based bis(phosphonic)acids. In the present paper,
we wish to report the catalytic properties of such ligands
and related compounds in the hydrogenation of aromatic
ketones in aqueous media. The three diamines 1, 2 and 3
(Scheme 1) were selected for this study.
Scheme 2. Conditions: i) 5% Pd/C, HCO2H, NEt3 (82%); ii)
(CCl3O)2CO, NEt3, CH2Cl2, then (1R,2R)-diaminocyclohexane
(75%); iii) Me3SiBr, CH2Cl2, room temp., then MeOH, room
temp., (quant.)
The catalytic activities of the three ligands 1؊3 in the
hydrogenation of various aromatic ketones in water under
hydrogen pressure (40 atm H2) were then studied. Solutions
of the neutral tetrasodium forms of the ligands were first
treated with [Ir(COD)Cl]2 (ligand/Ir: 4-fold excess of the
ligand to ensure the stability of the complex under H2 pres-
sure). The substrate was then added (neat if liquid or dis-
solved in ethyl acetate if solid) so as to give a 5% Ir/sub-
strate molar ratio. At the end of the reaction, the products
could easily be separated from the catalyst by simple extrac-
tion of the aqueous phase with ethyl acetate. In the case of
ligand 1, good catalytic activity was observed in the re-
duction of aromatic oxo esters and ketones (Table 1, entries
1, 3, 6), but the presence of electron-donating substituents
[a]
`
Laboratoire de Synthese Organique, UMR CNRS 6513,
`
B. P. 92208, 2, rue de la Houssiniere, F-44322 Nantes Cedex 03,
France
Fax: (internat.) ϩ 33-2/51125412
E-mail: bujoli@chimie.univ-nantes.fr
Eur. J. Org. Chem. 1999, 1745Ϫ1748
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
1434Ϫ193X/99/0707Ϫ1745 $ 17.50ϩ.50/0
1745

´
V. Pe nicaud, C. Maillet, P. Janvier, M. Pipelier, B. Bujoli
FULL PAPER
in the para position (entries 7Ϫ9) or the use of a lower catalyst can be recycled intact. As previously, ligand 2 per-
metal/substrate ratio (entry 4) led to a significant retar- formed better than bipyridine 1 under similar reaction con-
dation of the reduction. It is worth noting that the aqueous ditions (entry 25). In order to assess to what extent the reac-
catalytically active complex could be quantitatively reco- tion time could be reduced, the degree of conversion was
vered after carrying out the extraction in air with no par- measured as a function of time in the experiments corre-
ticular precautions. Its stability is evidently quite good since sponding to entries 20 and 21 (Table 2, entries 20a and 21a).
the aqueous phase could be reused with only a slight loss After 1 h, the conversion was very low (3Ϫ6%), but then
of activity (entry 2). However, if rhodium was used instead sharply increased to over 90% after 8 h.
of iridium, the catalytic activity was very low (entry 11).
Based on the commonly accepted mechanism together
Moreover, in the case of iridium, ligand 2 exhibited a higher with observations made in the literature,[13] the main role
activity than 1 (entries 5, 10), in contrast to the chiral of the added base might be to deprotonate the intermediate
[(1R,2R)-diurea]iridium complex derived from (1R,2R)-di- A, obtained by insertion of the ketone into one of the
aminocyclohexane, which is not stable under the reaction RhϪH bonds, while water could protonate the alkoxide li-
conditions and precipitates black metal (entry 12). The gand (Scheme 3).
higher efficiency of ligand 2 compared to 1 might stem from
steric hindrance to good complexation of the iridium ion
by the 2,2Ј-bipyridine core due to the CONHC3H6PO3Na2
chains. Another explanation invokes the higher electron
density present on the nitrogen atoms in 2 compared to
those in 1, as established by semiempirical calculations
(AM1 and PM3 methods).[10] Finally, the water-soluble sys-
tem gave better results than the related ligand (phosphonate
ester form) in a homogeneous methanolic medium (entry
13), despite the better solubility of hydrogen in methanol
compared to water. A possible explanation might be the
presence of a cationic complex in water, with one phos-
phonate group in the PO3NaϪ form acting as the coun-
teranion to the iridium ion.[11] In fact, some acceleration
of reaction rates for cationic phosphaneϪmetal complexes
compared to the corresponding neutral species has pre-
viously been reported in the literature.[12]
In the light of these results and taking into account the
catalytic properties (for the hydrogenation of ketones) re-
ported in the literature for (2,2Ј-bipyridine)rhodium com-
plexes in basic methanolic media (no activity detected un-
der neutral conditions),[5a] the activity of the (1)rhodium
complex in the reduction of acetophenone at pH ϭ 9 (by
addition of sodium hydroxide) was re-examined. Under
Scheme 3. Proposed effect of NaOH in the catalytic site of Rh-
catalyzed hydrogenation of ketones in water under hydrogen pres-
sure; S ϭ H2O
these conditions, complete conversion was achieved (Table
This push-pull process would favor the reductive elimin-
2, entry 14) and the aqueous catalytic phase could be reused ation of A, allowing the oxidative addition of hydrogen to
with only a slight loss of activity (entry 15). In addition, a regenerate B, thereby accelerating the reaction rate. The
strong activity enhancement of the water-soluble system amount of base necessary to observe this reactivity en-
based on ligand 1 was observed in basic media, since aceto- hancement (30 equiv. of OHϪ based on Ir or Rh in entries
phenones substituted at the 4Ј-position by electron-donat- 14Ϫ25) was not optimized and might be reduced, since a
ing groups (ethyl, methoxy) were easily reduced to the cor- 98% conversion was still obtained in entry 22 with only 5
responding alcohols, using iridium as well as rhodium (en- equiv. of OHϪ added (based on Ir). Similarly, in the case of
tries 16, 17, 19, 20). As 4Ј-methoxyacetophenone is a solid entry 25, 4Ј-methoxyacetophenone was converted in 95%
substrate, it first had to be dissolved to carry out the cata- yield with only 1.5 equiv. of OHϪ added (based on Ir), thus
lytic test. The choice of solvent proved to be important; showing that the role of the promoter is probably catalytic.
diethyl ether gave good results whereas ethyl acetate led
In summary, we have synthesized new water-soluble 2,2Ј-
only to low conversions (entry 18). Decreasing the ligand/ bipyridine ligands. In the hydrogenation of various aceto-
Ir ratio to 2:1 had no significant effect on the degree of phenones in water under hydrogen pressure, the Rh and Ir
conversion (entry 22), but decreasing the Ir/substrate ratio complexes of these ligands show remarkable catalytic activi-
slowed down the reaction and gave the alcohol with only ties in basic media, in the absence of any phase-transfer
70% conversion (entry 23). However, when the aqueous agent. We are currently trying to extend these results to chi-
phase from this latter experiment was reused and the cata- ral diamines, known to be stable under hydrogen pressure,
lytic test was run for a longer period (64 h; entry 24), the by functionalization of these ligands with PO3Na2 moieties.
reduction was almost quantitative, again showing that the Moreover, the heterogenization of such systems as insoluble
1746
Eur. J. Org. Chem. 1999, 1745Ϫ1748

New Water-Soluble Diamine Complexes as Catalysts
FULL PAPER
ray Spectroscopy (EDXS) measurements were made on a Jeol JM-
35C SEM with a Tracor TN5500 micro Z attachment.
metal phosphonates for supported catalysis is also being in-
vestigated.
General Procedure for Hydrogenation: In a 25-mL Schlenk tube,
0.12 mmol of ligand 1؊3 and 0.48 mL of 1  aq. sodium hydroxide
solution were added to 5 mL of water under argon and the mixture
was degassed. After complete dissolution of the ligand, 0.015 mmol
of [M(COD)Cl]2 (M ϭ Ir, Rh) was added. After stirring for 24 h
at room temperature, the deep-red (Ir) or yellow (Rh) solution was
transferred to a 30-mL stainless steel glass-coated autoclave, and
0.6 mmol of substrate (neat when liquid or dissolved in 0.5 mL of
solvent when solid; see Tables) was added. The autoclave was
purged 3 times with argon, then 3 times with hydrogen, and the
final H2 pressure was adjusted to 40 atm. The mixture was stirred
at room temperature for 21 h and then extracted with ethyl acetate.
The aqueous phase was separated and reused, while the colorless
organic layer was concentrated and analysed by gas chromatogra-
phy and 1H NMR to determine the conversions and reaction yields,
using nonane (0.1 mmol) as an internal standard. No metal (Ir or
Rh) could be detected on performing EDXS experiments on the
residue from the organic phase. GC analyses of the aqueous phase
confirmed that all the reaction products had been removed during
the extraction process. The tests corresponding to entries 22 and
23 were run twice and the error limits were estimated as ±2%.
Table 1. Hydrogenation of aryl ketones in the presence of water-
soluble diamine-complexed transition metals (neutral pH)[a]
Entry Metal Diamine[b]
Substrate
Conversion[c]
1
2
Ir
Ir
1
methyl phenylglyoxylate > 99%
1 (after 1 use) methyl phenylglyoxylate 96%
3
4
5
6
7
8
Ir
1
1
2
1
1
1
1
2
1
3
acetophenone
acetophenone
acetophenone
> 99%
24%
> 99%
Ir[d]
Ir
Ir
Ir
Ir
Ir
Ir
Rh
Ir
4Ј-nitroacetophenone[e] > 99%
4Ј-chloroacetophenone 88%
4Ј-ethylacetophenone
4Ј-ethylacetophenone
4Ј-ethylacetophenone
acetophenone
38%
64%
95%
5%
9[f]
10
11
12
acetophenone
unstable complex;
metal precipitation[g]
4%
13[h] Ir
1 (phosphonate 4Ј-ethylacetophenone
ester form)
[a]
Conditions: diamine/metal ϭ 4:1; metal/substrate (neat) ϭ 5%;
[b]
40 atm H2; water; reaction time ϭ 21 h. Ϫ In its neutral sodium
form. Ϫ [c] Yield in the corresponding alcohol ϭ 100%. Ϫ [d] Metal/
[e]
[f]
substrate ϭ 1%. Ϫ
Dissolved in 0.5 mL of ethyl acetate. Ϫ
Reaction time ϭ 66 h. Ϫ [g] Same result when rhodium used instead
Compound 1: This ligand was prepared from the 5,5Ј-dimethyl-2,2Ј-
bipyridine derivative (easily obtained according to Lemaire et al. by
coupling of 2-bromo-5-methylpyridine).[14] The methyl substituents
were oxidized to carboxylic acid groups (CrO3/H2SO4, 70%), then
converted into acyl chlorides (SOCl2, quantitative). To a solution
of diethyl 3-aminopropylphosphonate (2.84 g, 14 mmol) in freshly
distilled dichloromethane (200 mL) and triethylamine (2.05 mL,
14 mmol), a solution of 5,5Ј-bis(chlorocarbonyl)-2,2Ј-bipyridine
(1.02 g, 3.6 mmol) in 300 mL of dichloromethane was added drop-
wise. The reaction mixture was stirred at room temperature for
18 h. After hydrolysis (water) and extraction (dichloromethane),
the solvent was evaporated from the combined organic solutions to
give a yellow oil, which was purified by column chromatography
(SiO2; 10% EtOH/CH2Cl2). The desired compound was obtained
as a colorless oil in 75% yield. Ϫ 1H NMR (200 MHz, CDCl3):
δ ϭ 1.32 (t, 12 H, 3J ϭ 7 Hz, CH3 ethyl), 1.9 (m, 8 H, CH2CH2P),
of iridium. Ϫ Same conditions as for[a], but with water replaced
[h]
by methanol.
Table 2. Hydrogenation of aryl ketones in the presence of water-
soluble diamine-complexed transition metals (basic medium)[a]
Entry Metal Diamine[b]
Substrate
Conversion[c]
14
15
16
17
18
19
20
20a
21
21a
22
23
24
25
Rh
Rh
Rh
Ir
1
acetophenone
> 99%
93%
> 99%
> 99%
7%
96%
> 99%
1 (after 1 use) acetophenone
1
1
1
1
1
4Ј-ethylacetophenone
4Ј-ethylacetophenone
Rh
Rh
Ir
4Ј-methoxyacetophenone[d]
4Ј-methoxyacetophenone[e]
4Ј-methoxyacetophenone[e]
conversion versus time for entry 20: 3% (1 h), 30% (3 h), 90% (8 h)
Ir
2
4Ј-methoxyacetophenone[e]
> 99%
3
3
3
3.6 (q, 4 H, J ϭ 6 Hz, NHCH2), 4.1 (quint, 8 H, JHH ϭ JHP
ϭ
conversion versus time for entry 21: 6% (1 h), 95% (8 h)
Ir[f]
Ir[g]
1
1
4Ј-methoxyacetophenone[e]
4Ј-methoxyacetophenone[e]
98%
7 Hz, CH2 ethyl), 7.9 (t, 2 H, 3J ϭ 6 Hz, CONH), 8.3 (dd, 2 H,
70%
3J ϭ 8 Hz, J ϭ 2.3 Hz, bipyridine), 8.5 (dd, 2 H, J ϭ 8 Hz, J ϭ
4
3
5
Ir[g] 1 (after 1 use) 4Ј-methoxyacetophenone[e]
96%[h]
93%
4
5
0.8 Hz, bipyridine), 9.2 (dd, 2 H, J ϭ 2.3 Hz, J ϭ 0.8 Hz, bipyri-
dine). Ϫ 31P NMR (81 MHz, CDCl3): δ ϭ 31.6. Ϫ MS (EI); m/z
(%): 598 (1) [Mϩ·], 377 (100). Ϫ The tetraethyl ester form of ligand
1 thus obtained was converted into the corresponding bis(phos-
phonic acid) using bromotrimethylsilane, as described in the syn-
thesis of compound 3 (see below). Ϫ 1H NMR (200 MHz, DMSO):
δ ϭ 1.7 (m, 8 H, CH2CH2P), 3.3 (q, 4 H, 3J ϭ 6 Hz, NHCH2), 8.4
(dd, 2 H, 3J ϭ 8 Hz, 4J ϭ 2 Hz, bipyridine), 8.5 (d, 2 H, 3J ϭ 8 Hz,
bipyridine), 8.9 (t, 2 H, 3J ϭ 6 Hz, CONH), 9.1 (d, 2 H, 4J ϭ 2 Hz,
bipyridine). Ϫ 31P NMR (81 MHz, DMSO): δ ϭ 26.5.
Ir[f,g]
2
4Ј-methoxyacetophenone[e]
[a]
Conditions: diamine/metal ϭ 4:1; metal/substrate (neat) ϭ 5%;
[b]
40 atm H2; water; reaction time ϭ 21 h; NaOH/metal ϭ 30:1. Ϫ
[c]
In its neutral sodium form. Ϫ Yield in the corresponding alco-
hol ϭ 100%. Ϫ [d] Dissolved in 0.5 mL of ethyl acetate. Ϫ [e] Dissol-
[f]
[g]
ved in 0.5 mL of diethyl ether. Ϫ Diamine/metal ϭ 2:1. Ϫ
[h]
Metal/substrate ϭ 1%. Ϫ Reaction time ϭ 64 h.
Experimental Section
Diethyl 4-Aminophenylphosphonate: 5.23 mL of formic acid
(136 mmol) was added dropwise to a stirred mixture of 10.7 g
(41.3 mmol) of diethyl 4-nitrophenylphosphonate,[8] 23.5 mL (181
mmol) of triethylamine, and 100 mg of 5% Pd/C. The mixture was
refluxed for 1 h, then poured into water and extracted with di-
chloromethane. The combined organic layers were washed with
brine, dried (MgSO4), and concentrated. The desired compound
was crystallized from toluene (pale-yellow crystals; 82% yield). Ϫ
M.p. 131°C. Ϫ 1H NMR (200 MHz, CDCl3): δ ϭ 1.3 (t, 6 H, 3J ϭ
7 Hz, CH3 ethyl), 4.05 (m, 6 H, CH2 ethyl and NH2), 6.7 (dd, 2 H,
General: 1H- and 31P-NMR spectra were recorded with a Bruker
AC-200 spectrometer with tetramethylsilane (1H) and external 85%
H3PO4 (31P) as references. High-resolution mass spectra were ob-
tained with a Hewlett-Packard HP 5889A instrument. Gas chroma-
tographic analyses were performed using a Hewlett-Packard HP
6890 gas-chromatograph with a J. & W. Scientific DB-1701 column
(l ϭ 30 m, i.d. ϭ 0.25 mm). Melting points were determined with
a Reichert-Kofler hotplate apparatus. Optical rotations were meas-
ured with a PerkinϪElmer 341 polarimeter. Energy Dispersive X-
Eur. J. Org. Chem. 1999, 1745Ϫ1748
1747

´
V. Pe nicaud, C. Maillet, P. Janvier, M. Pipelier, B. Bujoli
FULL PAPER
3J ϭ 8 Hz, 4JHP ϭ 3.5 Hz, phenyl), 7.6 (dd, 2 H, 3J ϭ 8 Hz, 3JHP ϭ
13 Hz, phenyl). Ϫ 31P NMR (81 MHz, CDCl3): δ ϭ 20.5. Ϫ MS
(EI); m/z (%): 229 (63) [Mϩ·], 173 (49), 156 (39), 93 (100).
[2c]
Chim. Fr. 1987, 3, 480Ϫ486. Ϫ
Y. Amrani, L. Lecomte, D.
Sinou, J. Bakos, I. Toth, B. Heil, Organometallics 1989, 8,
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542Ϫ547. Ϫ
hedron: Asymmetry 1990, 1, 913Ϫ930. Ϫ
Mague, D. M. Roundhill, Inorg. Chem. 1992, 31, 3500Ϫ3501.
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[2e]
S. Ganguly, J. T.
T. L. Schull, J. C. Fettinger, D. A. Knight, Inorg. Chem.
Compound 3: 125 mg of triphosgene (0.42 mmol) was dissolved in
2.3 mL of dichloromethane under argon. To this, a solution of
diethyl 4-aminophenylphosphonate (265 mg, 1.15 mmol, in 4 mL
of dichloromethane and 0.17 mL of triethylamine) was slowly ad-
ded by means of a syringe pump (4 mL/h). The reaction mixture
was stirred for 30 min and then a solution of (1R,2R)-diaminocy-
clohexane (66 mg, 0.57 mmol, in 6 mL of dichloromethane and
0.17 mL of triethylamine) was rapidly added. The resulting mixture
was stirred for a further 1 h and then concentrated under reduced
pressure. The crude residue obtained was redissolved in chloro-
form, the resulting solution was washed with water, and the organic
layer was dried and concentrated to give a white solid, which was
rinsed with acetone and collected by filtration (75% yield). Ϫ M.p.
[2f]
Ϫ
[2g]
1996, 35, 6717Ϫ6723. Ϫ
H Gulyas, P. Arva, J. Bakos, J.
[2h]
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[3]
A. Clearfield in Progress in Inorganic Chemistry (Ed.: K. D.
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[4] [4a]
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[4c]
Pinel, B. Bujoli, New J. Chem. 1998, 22, 901Ϫ905. Ϫ
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also, D. Villemin, P. A. Jaffres, B. Nechab, F. Courivaud, Tetra-
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[5]
[5a]
See, for example:
G. Mestroni, G. Zassinovich, A. Camus,
[5b]
J. Organomet. Chem. 1977, 140, 63Ϫ72. Ϫ
C. Botteghi, G.
20
1
255°C. Ϫ [α]D ϭ ϩ61 (c ϭ 1, CHCl3). Ϫ H NMR (200 MHz,
DMSO): δ ϭ 1.2 (t, 12 H, 3J ϭ 7 Hz, CH3 ethyl), 1.3 (m, 4 H,
NCHCH2CH2 cyclohexyl), 1.65 (m, 2 H, NCHCH2 cyclohexyl),
1.95 (m, 2 H, NCHCH2 cyclohexyl), 3.45 (m, 2 H, NCH cyclo-
Chelucci, G. Chessa, G. Delogu, S. Gladiali, F. Soccolini, J.
[5c]
Organomet. Chem. 1986, 304, 217Ϫ225. Ϫ
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tin, G. Zassinovich, G. Mestroni, Tetrahedron: Asymmetry 1990,
3
3
[5e]
hexyl), 3.95 (quint, 8 H, JHH ϭ JHP ϭ 7 Hz, CH2 ethyl), 6.2 (d,
2 H, 3J ϭ 7 Hz, CHNHCO), 7.5 (m, 8 H, phenyl), 8.85 (s, 2 H,
CONHC6H4). Ϫ 31P NMR (81 MHz, DMSO): δ ϭ 18.7. Ϫ MS
(EI); m/z (%): 395 (38) [Mϩ·], 229 (66), 199 (100). Ϫ The tetraethyl
ester form of compound 3 (210 mg, 0.33 mmol) was suspended in
5.5 mL of dichloromethane and bromotrimethylsilane (0.35 mL,
2.6 mmol) was added. The resulting clear yellow solution was
stirred for 24 h at room temperature under argon. After evapo-
ration of the solvent, 20 mL of methanol was added and the re-
sulting solution was stirred for 18 h, whereupon a white precipitate
was gradually deposited. This white solid was isolated by filtration,
washed with dichloromethane, and dried in vacuo to afford a quan-
titative yield of ligand 3. Ϫ 1H NMR (200 MHz, DMSO): δ ϭ
1.2 (m, 4 H, NCHCH2CH2 cyclohexyl), 1.65 (m, 2 H, NCHCH2
cyclohexyl), 1.95 (m, 2 H, NCHCH2 cyclohexyl), 3.4 (m, 2 H, NCH
cyclohexyl), 6.15 (d, 2 H, 3J ϭ 6 Hz, CHNHCO), 7.45 (m, 8 H,
phenyl), 8.7 (s, 2 H, CONHC6H4). Ϫ 31P NMR (81 MHz, DMSO):
δ ϭ 13.8.
1, 635Ϫ648. Ϫ
P. Gamez, F. Fache, M. Lemaire, Tetra-
[5f]
hedron: Asymmetry 1995, 6, 705Ϫ718. Ϫ
P. Gamez, B.
[5g]
Dunjic, M. Lemaire, J. Org. Chem. 1996, 61, 5196Ϫ5197. Ϫ
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and references therein. Ϫ
H. Doucet, T. Ohkuma, K. Mu-
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[6]
[7]
For a recent review, see: V. Fehring, R. Selke, Angew. Chem.
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[8]
T. Hirao, T. Masunaga, O. Yoshiro, T. Agawa, Synthesis 1981,
56Ϫ57.
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C. E. McKenna, M. T. Higa, N. H. Cheung, M. C. McKenna,
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[10]
All calculations were performed with a Silicon Graphics Indy
workstation using the program package Spartan 4.0 wave func-
tion, Inc., 18401 von Karman, #210, Irvine, CA, USA.
Such features have been reported in the case of diphosphane
functionalized with sulfate SO4Li or sulfonate SO3Na groups.
See ref.[2g] and C. Lensink, J. G. de Vries, Tetrahedron: Asym-
metry 1992, 3, 235Ϫ238.
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P. A. Wender, H. Takahashi, B. Witulski, J. Am. Chem. Soc.
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[1b]
E. G. Kunz, Chemtech 1987, 570Ϫ575. Ϫ
For a review,
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Q. Jiang, Y. Jiang, D. Xiao, P. Cao, X. Zhang, Angew. Chem.
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[1c]
See also: Aqueous Phase
Organometallic Catalysis (Eds.: B. Cornils, W. A. Herrmann),
Wiley-VCH, Weinheim, 1998.
V. Penalva, J. Hassan, L. Lavenot, C. Gozzi, M. Lemaire, Tetra-
hedron Lett. 1998, 39, 2559Ϫ2560.
[2]
[2a] R. G. Nuzzo, S. L. Haynie, M. E. Wilson, G. M. Whitesides,
Received November 5, 1998
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J. Org. Chem. 1981, 46, 2861Ϫ2867. Ϫ
D. Sinou, Bull. Soc.
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Eur. J. Org. Chem. 1999, 1745Ϫ1748