A synthetic route to a new surface-active phosphine ligand: 12-DPDP (12-diphenylphosphinododecylphosphonate)

Article abstract of DOI:10.1016/S0040-4020(00)00546-9

A water-soluble phosphonate-functionalized phosphine ligand Na₂[Ph₂P(CH₂)₁₂PO₃] (8), was prepared in eight steps from cyclododecanone. Phosphine 8 reacts with [Rh(COD)Cl]₂ in methanol to give the new complex Na₂[Rh(COD)(Ph₂P(CH₂)₁₂PO₃)Cl] (9). Complex 9 is inactive in the catalytic hydrogenation of 1-hexene and cyclohexene due to the decomposition of 9 to rhodium metal in the presence of hydrogen gas. Hydrogenation of decene using [Rh(COD)₂]BF₄ and 3 equiv. of 8 in an aqueous emulsion was achieved using 1 atm H₂. ³¹P NMR studies on 8 suggest a lack of well-defined aggregation in water, which has been ascribed to the steric bulk of the diphenylphosphino group. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4020(00)00546-9

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 7093–7097
A Synthetic Route to a New Surface-Active Phosphine Ligand:
12-DPDP (12-Diphenylphosphinododecylphosphonate)
†
,‡
*
´
Terence L. Schull, L. Renee Olano and D. Andrew Knight
Department of Chemistry, The George Washington University, 725 21st Street NW, Washington, DC 20052, USA
Received 29 January 2000; accepted 15 June 2000
Abstract—A water-soluble phosphonate-functionalized phosphine ligand Na2[Ph2P(CH2)12PO3] (8), was prepared in eight steps from
cyclododecanone. Phosphine 8 reacts with [Rh(COD)Cl]2 in methanol to give the new complex Na2[Rh(COD)(Ph2P(CH2)12PO3)Cl] (9).
Complex 9 is inactive in the catalytic hydrogenation of 1-hexene and cyclohexene due to the decomposition of 9 to rhodium metal in the
presence of hydrogen gas. Hydrogenation of decene using [Rh(COD)2]BF4 and 3 equiv. of 8 in an aqueous emulsion was achieved using
1 atm H2. 31P NMR studies on 8 suggest a lack of well-defined aggregation in water, which has been ascribed to the steric bulk of the
diphenylphosphino group. ᭧ 2000 Elsevier Science Ltd. All rights reserved.
Introduction
or a bilayer, and the possibility of micro-environmental
control of the catalytic transition metal centers becomes
viable. As such, micellar micro-reactors are related to the
new catalytic systems based on metallo-dendrimers which
are currently in vogue.4
The field of aqueous and biphasic homogeneous catalysis
has been dominated by the hydrophilic sulfonated phos-
phine, TPPTS (‘triphenylphosphine trisulfonate’). Early
work on the use of TPPTS in aqueous phase hydroformyl-
ation and hydrogenation has spurred intense interest in
applying the technique to alternative homogeneous transi-
tion metal reactions such as Suzuki coupling, allylic sub-
stitution, hydrodimerization and aqueous enantioselective
catalysis.1,2 The attraction of using water as a solvent is
obvious from the environmental aspect, but a further advan-
tage is the easy separation of the water-soluble catalyst from
water-insoluble organic products. The limitation of low
aqueous solubility for the majority of organic compounds
may be circumvented by using either a biphasic organic–
aqueous system where reactivity takes place at the interface,
or the addition of a polar organic co-solvent to allow
adequate partitioning of reactants, products and catalyst.
The solubility of substrates may also be increased by adding
a suitable surfactant which solubilizes hydrophobic organic
compounds, and additional potential benefits such as the
increase in catalytic reaction rates and improvements in
selectivities (regio-selective and enantioselective) have
been suggested and realized in a few isolated cases.3 If the
correct surfactant system is chosen, metal complexes may
form part of a discrete aggregate structure such as a micelle
As part of our on-going research into the use of water-
soluble organometallic compounds in aqueous phase
homogeneous catalysis, we have recently investigated the
transition metal coordination chemistry of the highly water-
soluble, phosphonylated phosphine, TPPMP (‘triphenyl-
phosphine monophosphonate’) in the aqueous phase.5 We
have also reported the use of TPPMP as a ligand in the
palladium catalyzed carbonylation of benzyl halides in
water.6
Experimental
General data
All reactions were conducted under dry, pre-purified N2
using standard Schlenk-line and catheter-tubing techniques
unless otherwise stated. IR spectra were recorded on a
1
Mattson Galaxy 6020 (FT) spectrometer. All H and 31P
NMR spectra were recorded on a Bruker AC-300 spectro-
meter and referenced to internal tetramethylsilane or resi-
dual CHCl3 (1H), and external H3PO4 (31P). Mass spectra
were recorded on a Hewlett–Packard 5971A/5870 GC-mass
spectrometer equipped with a 20 m×0.22 mm HP fused
silica column, with a stationary phase of cross-linked 5%
phenylmethylsilicone, or were performed by Mass
Consortium, San Diego, CA.
Keywords: phosphine; amphipathic; rhodium; phosphonate.
* Corresponding author. Tel.: ϩ1-504-865-2269; fax: ϩ1-504-865-3269;
e-mail: daknight@loyno.edu
Present address: Center for Biomolecular Science and Engineering, Code
6950, Naval Research Laboratories, 4555 Overlook Avenue SW, Washing-
ton, DC 20375, USA.
†
‡
Present address: Department of Chemistry, Loyola University, New
Solvents were purified as follows: THF and ether, distilled
Orleans, LA 70118, USA.
0040–4020/00/$ - see front matter ᭧ 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(00)00546-9

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T. L. Schull et al. / Tetrahedron 56 (2000) 7093–7097
from sodium/benzophenone; hexane, hexanes and CH2Cl2,
distilled from CaH2; ethyl acetate, methanol, acetone, acetic
acid (Fisher), ethanol (Aaper Alcohol and Chemical Co.),
anhydrous DME (Aldrich), CDCl3, acetone-d6 and D2O
(Cambridge Isotope Laboratories), used as received. Silica
gel (Scientific Products, 230–400 mesh), magnesium sulfate
and sodium sulfate (Fisher) were used as received.
over a period of 20–30 min. The ice-bath was removed and
the mixture stirred overnight at room temperature. The reac-
tion mixture was cooled to 0ЊC (ice-bath) and water was
carefully added (375 mL). The reaction mixture was then
poured into ether (500 mL) and the two phases separated.
The aqueous phase was washed with ether (200 mL) and the
organic fractions combined and dried over anhydrous
Na2SO4. Then, the ether solution was concentrated using
rotary evaporation to give a yellow oil which solidified on
standing. The residue was taken up in hexane and chroma-
tographed on a 50 mm diameter column (179 g silica gel,
ether–hexane). The solvent was removed from the eluate to
give 2 as spectroscopically pure colorless oil (22.01 g,
77%). IR (NaCl, thin film): n(O–H) 3321 cmϪ1, n(C–O)
Reagents were obtained as follows: cyclohexene, 1-hexene,
1-decene, 2,4,6-collidine, sodium dodecyl sulfate, trityl
chloride, sodium hydroxide (Aldrich), hydrogen (MG
Industries), 10% palladium–charcoal (MC&B), sodium
borohydride, tetraethylammonium perchlorate (Fluka),
TiCl4, perchloric acid, hydriodic acid, triethylamine
(Fisher), LiPPh2, prepared according to Ref. 21; p-toluene-
sulfonyl chloride (Aldrich), recrystallized before use;
di-n-butylphosphosphite (Aldrich), vacuum distilled prior
to use; m-CPBA was purified according to the literature
procedure.7 [Rh(COD)2]BF4 was synthesized according to
the literature procedure.8
1
1051 cmϪ1. H NMR (CDCl3): d 3.64 (t, 2H, HOCH2–),
3.19 (2H, t, ICH2), 1.82 (m, 2H, HOCH2CH2–), 1.63–1.23
(m, 20H, CH2).
12-Iodododecan-1-ol trityl ether (3). A 250 mL Schlenk
flask was equipped with magnetic stirrer bar and charged
with 2 (15.61 g, 50.00 mmol), trityl chloride (13.94 g,
50.00 mmol), and Et4NClO4 (11.49 g, 50.00 mmol) and
CH2Cl2 (200 mL). Then, 1.5 equiv. of 2,4,6-collidine
(9.9 mL, 7.5 mol) was added via syringe and the solution
was stirred for ca. 30 min. Water (200 mL) was added and
the two phases were separated. The organic phase was
washed with water and dried over anhydrous MgSO4.
Then, the solution was concentrated using rotary evapora-
tion and the resulting oil chromatographed on a 50 mm
diameter column (201 g silica gel, ether–hexane). The
solvent was removed from the eluate to give 3 as an orange
oil (24.30 g, 90%). 1H NMR (CDCl3): d 7.54–7.16 (m, 15H,
3C6H5), 3.17 (2H, t, ICH2), 3.03 (2H, t, CH2OC–), 1.80 (m,
2H, ICH2CH2–), 1.61 (m, 2H, C–OCH2CH2–), 1.44–1.06
(m, 18H, CH2).
12-Iodododecan-1-oic acid (1). A 500 mL flask was
charged with cyclododecanone (27.35 g, 0.1500 mol),
m-CPBA (43.97 g, 0.255 mol) and CH2Cl2 (200 mL).
Then, trifluoroacetic acid (0.12 mL, 1.5 mmol) was added
and the mixture was refluxed for 45 h. The reaction was
allowed to cool to room temperature and the resulting
white solid was filtered off. The filtrate was diluted with
CH2Cl2 (800 mL), washed successively with K2CO3 solu-
tion (2×250 mL), water (250 mL) and sodium thiosulfate
solution (250 mL). The organic phase was dried over
anhydrous MgSO4 and the solvent removed via rotary
evaporation. The residue was dissolved in 95% EtOH
(100 mL) and NaBH4 (0.378 g, 0.010 mmol) in EtOH
(10 mL) was added and the reaction mixture was stirred
for 30 min. Then, 1 M hydrochloric acid solution
(100 mL) and ether (200 mL) were added. Solvent was
removed from the organic phase via rotary evaporation and
the resulting residue was transferred to a 500 mL round-
bottom flask equipped with a reflux condensor and stirrer
bar. Hydriodic acid (100 mL, 0.76 mol, 57%) was added via
syringe and immediately followed by acetic acid (100 mL).
The solution was refluxed for 3 h during which time the color
changed from orange to pale yellow. The solution was
allowed to cool to room temperature and separated into two
phases. The mixture was poured onto water (1000 mL) and a
precipitate immediately formed, which was collected by filtra-
tion, air-dried and then dried under oil-pump vacuum. Crystal-
lization from hexanes (300 mL) gave 1 as pink flakes
(30.85 g, 63%), mp 69–71ЊC. IR (KBr disk): n(CvO)
12-Di-n-butylphosphonododecan-1-ol trityl ether (4). A
500 mL Schlenk flask was equipped with a mechanical
stirrer, pressure-equalizing addition funnel, reflux con-
denser and charged with sodium metal (1.27 g,
55.0 mmol) and hexane (125 mL). The mixture was heated
to reflux and a solution of di-n-butylphosphite (10.7 mL,
55.0 mmol) in hexane (25 mL) was added dropwise with
stirring. The mixture was refluxed overnight and then
allowed to cool to room temperature. A solution of 3
(21.45 g, 39.50 mmol) in hexane (50 mL) was added drop-
wise. The mixture was refluxed overnight, allowed to cool
to room temperature and quenched with 10% NaCl solution
(100 mL). Ether (100 mL) was added and the two phases
separated. The organic phase was washed with a portion of
10% NaCl solution (100 mL) and the aqueous phase
extracted with ether (100 mL). The ether fractions were
combined, dried (anhydrous Na2SO4) and solvent removed
on a rotary evaporator. The resulting residue was chromato-
graphed on a 50 mm diameter column (150 g silica gel,
ethyl acetate). The solvent was removed from the eluate
to give 4 as a pale yellow oil (22.64 g, 92%). IR (NaCl,
1
1691 cmϪ1. H NMR (CDCl3): d 3.19 (t, 2H, ICH2–), 2.35
(t, 2H, HO2CCH2–), 1.82 (m, 2H, HO2CH2CH2–), 1.63 (m,
2H, ICH2CH2–), 1.45–1.25 (m, 14H, CH2). MS (EI-MS): m/e
199 (100%) (M Ϫ127).
12-Iodododecan-1-ol (2). A 1 L three-neck, round-bottom
flask was equipped with a mechanical stirrer, septum and a
pressure-equalized dropping funnel. The flask was charged
with sodium borohydride (11.45 g, 0.3030 mol) and
anhydrous DME (350 mL). The flask was then cooled in
an ice bath and TiCl4 (11.1 mL, 0.101 mol) was added via
syringe. Then, a solution of 1 (30.00 g, 92.00 mmol) in
anhydrous DME (150 mL) was added via a dropping funnel
1
thin film): n(PO3) 1071, 1026, 1003, 978 cmϪ1. H NMR
(CDCl3): d 7.30–7.50 (m, 15H, 3C6H5), 4.05 (m, 4H,
2CH2OP) 3.05, (2H, t, CH2OC–), 1.80–1.20 (m, 22H,
CH2), 0.93 (t, 6H, 2CH3). 31P NMR (CDCl3): d 33.3 (s).
12-Di-n-butylphosphonododecan-1-ol (5). A 1 L Parr

T. L. Schull et al. / Tetrahedron 56 (2000) 7093–7097
7095
Scheme 1. Reagents and conditions: (i) NaBH4, TiCl4; (ii) Ph3CCl, Et4Nϩ ClO4Ϫ, 2,4,6-collidine; (iii) Na, HP(O) (OBu)2; (iv) H2, Pd–C, HClO4; (v) TsCl,
Et3N, 0ЊC; (vi) LiPPh2, Ϫ78ЊC; (vii) Me3SiBr, H2O, NaOH.
bomb was charged with a solution of 4 (22.54 g,
36.30 mmol), 70% perchloric acid (1 mL) in 95% ethanol
(200 mL) and a stirrer bar. The bomb was flushed with N2
and 10% Pd/C (3.38 g, 15 wt%) was added. The bomb was
pressurized with 60 psi hydrogen and the solution stirred for
16 h. Then the reaction mixture was filtered though a pad of
Celite and the solvent removed on a rotary evaporator. The
resulting residue was chromatographed on a 50 mm
diameter column (144 g silica gel, methanol–CH2Cl2).
The solvent was removed from the eluate to give 5 as a
pale yellow oil (12.03 g, 88%). IR (NaCl, thin film): n(O–
bath removed. The reaction was allowed to warm to room
temperature and the solvent was removed under oil-pump
vacuum. Dichloromethane (2×25 mL) was added and the
suspension chromatographed on a 20 mm diameter column
(50 g Florosil, CH2Cl2–THF). The solvent was removed
from the eluate to give 7 as a pale yellow oil (1.704 g,
89%). IR (NaCl, thin film): n(PO3) 1068, 1024, 1001,
1
978 cmϪ1. H NMR (CDCl3): d 7.8–7.2 (m, 10H, 2C6H5),
4.05 (m, 4H, 2CH2OP), 1.95–1.20 (m, 32H, 16CH2), 0.95 (t,
6H, 2CH3). 31P NMR (CDCl3): d 33.3 (s, PO), Ϫ15.5 (s, P).
1
H) 3420 cmϪ1, n(PO3) 1067, 1024, 981 cmϪ1. H NMR
12-Diphenylphosphinododecylphosphonate disodium salt
Na2[12-DPDP] (8). A 100 mL Schlenk flask was charged
with 7 (1.70 g, 3.10 mmol), CH2Cl2 (20 mL) and a stirrer
bar. Then bromotrimethylsilane9 (1.6 mL, 12 mmol) was
added via syringe with stirring. The reaction was stirred
for 4 h and the solvent was removed under oil-pump
vacuum. A solution of water (0.23 mL, 13 mmol) in acetone
(10 mL) was added and the solution was stirred for a further
20 min. The solvent was removed under oil-pump vacuum
and the residue was taken up in MeOH (10 mL). A Schlenk
tube was charged with sodium hydroxide (0.258 g,
6.45 mmol) and water (1.0 mL) and the resulting solution
was transferred via cannula to the methanolic solution of
12-DPDP. The solvent was removed under oil-pump
vacuum and THF (30 mL) and added to the resulting residue
and stirred for several minutes. The resulting white suspen-
sion was filtered to give a white solid which was extracted
with methanol and the solvent removed under oil-pump
vacuum to give 8 as a white solid (0.986 g, 66%). IR (KBr):
n(O–H) 3406 cmϪ1, n(C–H) 2922, 2851 cmϪ1, n(P–O)
1066 cmϪ1. 31P NMR (CDCl3): d 25.5 (s, PO), Ϫ15.4 (s, P).
(CDCl3): d 4.01 (m, 4H, 2CH2OP) 3.62, (2H, t, CH2OC–
), 1.79–1.20 (m, 32H, 16CH2), 0.94 (t, 6H, 2CH3). 31P NMR
(CDCl3): d 33.3 (s).
12-Di-n-butylphosphonododecan-1-tosylate (6). A 100 mL
Schlenk flask was charged with 5 (2.026 g, 5.000 mmol),
CH2Cl2 (20 mL) and a stirrer bar, and cooled to 0ЊC (ice
bath). Then, p-toluenesulfonyl chloride (1.122 g,
6.000 mmol) and Et3N (0.89 mL, 6.4 mmol) were added,
the cold bath was removed and the reaction mixture was
stirred overnight. A solution of 1 M HCl was added and
the organic layer was separated and washed with aqueous
NaHCO3, water and dried over anhydrous Na2SO4. The
solvent was removed on a rotary evaporator and the result-
ing residue was chromatographed on a 20 mm diameter
column (25 g silica gel, ether–hexane). The solvent was
removed from the eluate to give 6 as a yellow oil (2.19 g,
76%). IR (NaCl, thin film): n(PO3) 1097, 1068, 1024,
1
976 cmϪ1. H NMR (CDCl3): d 7.55 (dd, 4H, C6H4), 4.05
(m, 4H, 2CH2OP), 2.46 (s, ArCH3), 1.85–1.15 (m, 32H,
16CH2), 0.95 (t, 6H, 2CH2CH3). 31P NMR (CDCl3): d
33.3 (s). MS (ES-MS): m/e 379 (MHϩ).
Synthesis of Na2[12-DPDP]
12-Di-n-butylphosphonododec-1-yldiphenylphosphine (7).
A 100 mL Schlenk flask was charged with 6 (1.86 g,
3.49 mmol), THF (25 mL), a stirrer bar, and cooled to
Ϫ78ЊC (CO2/i-propanol). Then a solution of LiPPh2
(4.0 mL, 4.0 mmol, 1 M in THF) was added via syringe
with stirring. The reaction was stirred for 1 h and the cold
The synthetic route to Na2[12-DPDP] was largely dictated
by consideration of the cost of starting materials and
reagents, but there was a conscious decision to develop
the chemistry of a,v-functionalized alkanes where the
endgroups are chemically distinct. All attempts to sequen-
tially introduce the phosphonate and phosphine groups

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T. L. Schull et al. / Tetrahedron 56 (2000) 7093–7097
using the traditional methods of the Michaelis–Arbuzov
reaction, the action of lithium diphenylphosphide on 1,
12-dibromododecane and the formation of a secondary
phosphonium salt10 either gave poor product yields or
were hampered by purification problems. The addition of
diphenylphosphine11 to 1-bromododec-12-ene was avoided
due to the lack of a commercial source of the olefin.
Synthesis was ultimately accomplished in eight steps from
cyclododecanone in 14% overall yield and the synthetic
route is shown in Scheme 1. The requisite a,v-function-
alized dodecane was obtained from the Baeyer–Villiger
oxidation of cyclododecanone to give an intermediate
lactone which was subsequently hydrolyzed, and halo-
genated using mineral acid to give 12-iododecanoic acid
1. Several methods were attempted for the oxidation of
the ketone, including peroxymonosulfuric acid,12 peracetic
acid,13 and m-chloroperbenzoic acid.8 The method using
peracetic acid (from 30% hydrogen peroxide and acetic
acid) or perbenzoic acid gave the best results, however the
use of hydrogen peroxide–acetic acid was preferable in
terms of operational simplicity. In the subsequent conver-
sion of the lactone to the v-halogeno acid, it was found that
the use of 48% hydrobromic acid in the presence of concen-
trated sulfuric acid was inferior to 57% HI in acetic acid,
which is in agreement with the literature reports.14 It was
found that treatment of the crude lactone with sodium boro-
hydride in ethanol gave a cleaner reaction upon treatment
with acid. The borohydride is likely to serve two purposes:
destruction of any residual oxidant, and reduction of any
remaining ketone to the corresponding alcohol. The removal
of residual oxidant is important, as halide ion present in the
hydrolysis step can be oxidized to molecular halogen. In the
presence of the strong acids, the halogen thus produced can
react with enolized carbonyl groups to give a-halocarbonyl
compounds. By using sodium borohydride reduction
followed by HI–AcOH, acid 1 was obtained in 77% overall
yield. Following reduction of 1 to the corresponding alcohol
2 with low-valent titanium (formed in situ from sodium
borohydride and TiCl4 in DME),15 it was necessary to
protect the alcohol group prior to introduction of the
dibutylphosphonate group. The use of protecting groups
introduced by nucleophilic alkylation reactions, e.g. benzyl
ethers, seemed inappropriate due to the possibility of self-
alkylation involving the iodo group.16 Under the circum-
stances a reasonable choice was to introduce a trityl group
using freshly prepared trityl chloride17 and tetraethyl-
ammonium perchlorate in collidine to give the trityl ether
3 in 90% yield.18 The spectroscopic properties (NMR and
IR) of 1–3 and all subsequent compounds are listed in the
Experimental section.
required conversion of the alcohol 5 into the corresponding
tosylate 6.20 This is a routine reaction but is worth mention-
ing that the use of tosyl chloride in dichlormethane in the
presence of triethylamine gave superior results to the
conventional method of tosyl chloride in pyridine. Reaction
of 6 with lithium diphenylphosphide21 in THF gave the
expected product 7 cleanly as evidenced by 31P NMR: the
spectrum of 7 contains only two peaks at Ϫ15.5 and
33.3 ppm which correspond to the phosphine and phos-
phonate moieties, respectively. No evidence for dealkyl-
ation of the phosphonate ester by the nucleophilic lithium
diphenylphosphide was observed. Complete dealkylation of
the phosphonate ester using bromotrimethylsilane in
dichloromethane and neutraliztion of the acid using
sodium hydroxide gave the desired amphiphilic phosphine
12-DPDP (8). As expected, phosphine 8 is highly water-
soluble, although careful measurements of solubility were
not made. In addition to aqueous solubility, the ligand foams
considerable on contact with water indicating its highly
surface active properties.
31P NMR studies on Na2[12-DPDP] in solution
The amphipathic nature of 12-DPDP gives rise to the possi-
bility that the ligand could form, or be included in micelles
or other aggregate structures such as surface monolayers or
lamellar bilayers. The formation of such supramolecular
assemblies can have considerable influence the rate or selec-
tivity of an organic reaction. While enantioselectivity has
been demonstrated in transition metal catalyzed reactions
using reverse micelles,22 it has also been shown that the
microenvironment of the hydrophobic interior of micelles
allows for molecular interaction which would otherwise be
‘swamped out’ by solvent–solute interactions.23 Physical
measurements for determination of the molecular dynamics
of amphipathic molecules are numerous. Two of the most
common methods are light-scattering and NMR measure-
ments, which can be further divided into chemical shift24
and relaxometry studies.25 Before the possibility of aggre-
gation in metal complexes could be investigated, prelimin-
ary NMR studies on free 12-DPDP ligand were made.
Studies were conducted on 12-DPDP using serial dilutions
in degassed water and no significant changes in chemical
shift were observed across a wide concentration range
(0.01–0.5 M) which could possibly be associated with
aggregate formation. In addition, T1 and T2 measurements
were inconclusive. No further studies on the aggregation of
12-DPDP were performed and our conclusion is that the
bulky hydrophobic diphenylphosphino-group of 12-DPDP
is preventing aggregation in aqueous solution and it is
unlikely that metal complexes of 12-DPDP will form aggre-
gate structures. Further studies on the use of a co-surfactant
such as sodium dodecylsulfate to assist in micelle formation
are currently underway.
The introduction of the phosphonate group using standard
Michaelis–Arbuzov conditions (triethylphosphite in reflux-
ing toluene) gave the resulting phosphonate 4 in 50% yield.
This is unacceptably low for the introduction of a protecting
group in the middle of a multi-step synthesis. Using the
Michaelis–Becker reaction (sodium dibutylphosphite in
hexane), 4 was obtained in 92% yield. The 31P NMR spec-
trum of 4 contained one resonance at 33.3 ppm which is
typical for the dialkyl ester of a phosphonic acid. Cleavage
of the trityl either protecting group was achieved by hydro-
genolysis over palladium–charcoal, with perchloric acid as
a promoter.19 Introduction of the diphenylphosphino group
Coordination chemistry and catalytic hydrogenation
Preliminary investigations on the coordination of 12-DPDP
to a metal center were made. The addition of 2 equiv. of
12-DPDP to a methanolic solution of [Rh(COD)Cl]2
resulted in halide bridge cleavage and the formation of a
new rhodium phosphine species in solution as evidenced by
31P NMR. The 31P NMR spectrum contained two peaks, a

T. L. Schull et al. / Tetrahedron 56 (2000) 7093–7097
7097
see: (a) Cornils, B. J. Mol. Cat. A: Chem. 1999, 143, 1. (b) Driessen-
broad singlet at 26 ppm due to the uncoordinated phospho-
nate group and a new doublet at 27 ppm which we have
assigned to the rhodium coordinated phosphine in
complex 9. The chemical shift and coupling constant
(1JRh–Pˆ154 Hz) are both consistent with this assignment.26
No other peaks were present in the spectrum.
´
´
´
¨
Holscher, B. Adv. Cat. 1998, 42, 473. (c) Joo, F.; Katho, A. J. Mol.
Cat. A: Chem. 1997, 116, 3. (d) Katti, K. V.; Gali, H. Main Group
Chem. News 1999, 7, 21.
2. Cornils, B.; Herrmann, W. A. In Applied Homogeneous
Catalysis with Organometallic Compounds, Cornils, B.,
Herrmann, W. A., Eds.; VCH: Weinheim, 1996; Vol. 2, p 575.
3. Organic Reactions in Aqueous Media, Li, C.-J., Chan, T.-H.,
Eds.; Wiley-Interscience: New York, 1997.
4. Gorman, C. Adv. Mater. 1998, 10, 295.
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7. Schwartz, N. N.; Blumbergs, J. H. J. Org. Chem. 1964, 29,
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P. B.; Boucher, H.; Whelan, W.; Bosnich, B. Inorg. Chem. 1985,
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Res. 1999, 32, 9 (and references therein).
12. For the use of peroxymonosulfuric acid in organic oxidations
see: (a) Kennedy, R. J.; Stock, A. M. J. Org. Chem. 1960, 25, 1901.
(b) Monson, R. S. Advanced Organic Synthesis; Acadmic: New
York, 1972; p 10.
13. Mehta, G.; Pandey, P. N. Synthesis 1975, 404.
14. Large ring lactones are difficult to hydrolyze with hydro-
bromic acid, HI–AcOH being preferred: Kruizinga, W. H.; Kellog,
R. M. J. Chem. Soc., Chem. Commun. 1979, 286.
15. Kano, S.; Tanaka, Y.; Sugino, E.; Hibino, S. Synthesis 1980,
695.
The catalytic hydrogenation of a mixture of olefins,
1-hexene and cyclohexene was attempted using compound
9. An aqueous mixture of both alkenes, along with toluene
as an internal standard, was stirred under hydrogen (10 psi)
in the presence of 0.1 mol% of 9 at room temperature.
Aliquots were taken at 10, 30, 60 and 240 min and analyzed
by gas chromatography. No hydrogenation products were
detected and the solution had turned black indicating
decomposition of the complex. The facile decomposition
which explains the lack of catalytic activity for complex 9
is ascribed to the reduction of 9 to rhodium metal and
cyclooctane.26 Successful hydrogenation was achieved
however, using 3 equiv. of phosphine ligand per metal
center. 12-DPDP and [Rh(COD)2]BF4 were combined in a
3:1 ratio in water and decene was added as the substrate
(catalyst loading: 2.5 mol%, concentration of decene:
6 mmol per 5 ml water). After bubbling hydrogen gas,
through the emulsion overnight via a glass frit, analysis of
the mixture indicated quantitative reduction of the olefin.
Further studies are underway to define the catalytic species
present in the emulsion.
16. For typical reaction conditions see: Heathcock, C. H.;
Ratcliffe, R. J. J. Am. Chem. Soc. 1971, 44, 1438.
17. Horning, E. C., Ed.; Org. Synth. Coll., Vol. 3; Wiley: New
York, 1955; p 841.
18. Reddy, M. P.; Rampal, J. B.; Beaucage, S. L. Tetrahedron
Lett. 1986, 28, 23.
19. The reaction does not proceed in the absence of a promoter.
For use of promoters in the hydrogenolysis of benzyl ethers,
Rylander, P. N., Ed.; Catalytic Hydrogenation in Organic
Synthesis: Academic Press: New York, 1979, p 274.
20. Kagan, H. B.; Dang, T.-P. J. Am. Chem. Soc. 1972, 94, 6429.
Summary
A new water-soluble surfactant-like phosphine, 12-DPDP,
has been synthesized from the inexpensive precursor cyclo-
dodecanone in a multi-step sequence. 12-DPDP coordinates
to rhodium in the complex [Rh(COD)(12-DPDP)Cl] which
is inactive for catalytic hydrogenation of olefins due to the
reduction to rhodium metal by molecule hydrogen. An in
situ combination of 12-DPDP and [Rh(COD)2]BF4 in a 3:1
ratio is catalytically active for the hydrogenation of decene.
´
21. Veriot, G.; Collet, A. Acros Organics Acta 1995, 1, 40.
Acknowledgements
22. Buriak, J. M.; Osborn, J. A. Organometallics 1996, 15, 3161.
23. Nowick, J. S.; Chen, J. S.; Noronha, G. J. J. Am. Chem. Soc.
1993, 115, 7636 (and references therein).
24. For the use of NMR chemical shifts in CMC measurements
see: (a) Huc, I.; Oda, R. J. Chem. Soc., Chem. Commun. 1999,
2025. (b) Kresheck, G. C.; Jones, C. J. Colloid Interface Sci.
1980, 77, 278. (c) Muller, N.; Birkhan, R. H. J. Phys. Chem.
1967, 71, 957.
The donors of the Petroleum Research Fund (PRF 31395-
G3) administered by the American Chemical Society are
thanked for support of this work. We would also like to
thank Dr Todd Johnson for the synthesis of [Rh(COD)Cl]2
and one of the referees for suggestions for the hydrogenation
experiment.
25. Bratt, P. J.; Gillies, D. G.; Sutcliffe, L. H.; Williams, A. J.
J. Phys. Chem. 1990, 94, 2727.
References
26. Renaud, E.; Russell, R. B.; Fortier, S.; Brown, S. J.; Baird,
M. C. J. Organomet. Chem. 1991, 419, 403.
1. For recent reviews of aqueous biphasic homogeneous catalysis