Supramolecular hydrogen-bonding tautomeric sulfonamido-phosphinamides: A perfect p-chirogenic memory

Article abstract of DOI:10.1002/ejic.201100811

P-chirogenic, supramolecular hydrogen-bonding C₁-symmetrical sulfonamido-phosphinamides (METAMORPhos) have been successfully prepared. They were all found to possess a characteristic prototropic equilibrium between the P^III and the P

Full text of DOI:10.1002/ejic.201100811

FULL PAPER
DOI: 10.1002/ejic.201100811
Supramolecular Hydrogen-Bonding Tautomeric Sulfonamido–Phosphinamides:
A Perfect P-Chirogenic Memory
Frederic W. Patureau,[a] Maxime A. Siegler,[b] Anthony L. Spek,[b] Albertus J. Sandee,[a]
Sylvain Jugé,[c] Sarwar Aziz,[d] Albrecht Berkessel,[d] and Joost N. H. Reek*[a]
Keywords: Tautomerism / Rhodium / Hydrogenation / Phosphorus / Chirality
P-chirogenic, supramolecular hydrogen-bonding C1-sym-
metrical sulfonamido–phosphinamides (METAMORPhos)
have been successfully prepared. They were all found to pos-
sess a characteristic prototropic equilibrium between the PIII
and the PV tautomers that is slow on the NMR spectroscopic
timescale. Despite the dynamic and reversible protonation of
the P centre, the P-chirogenic information was found to be
retained in the tautomerization process, even in a protic sol-
vent environment. Several strategies to access the corre-
sponding enantiopure compounds were investigated, such as
diastereoselective crystallization, or enantioselective synthe-
sis. It was possible to resolve such a class of chiral ligands
with up to 99% ee, and apply them in the Rh-catalyzed
asymmetric hydrogenation of alkenes. These ligands are
interesting new building blocks in the area of acid/base-type
noninnocent ligand catalysis.
chirality in this field has been neglected so far. In general,
the resolution and use of P-chirogenic phosphanes has re-
mained marginal over the past five decades, although some
interesting examples have shown their potential in asym-
metric transition-metal catalysis.[1–3] Even more scarce are
the examples of PIII-chirogenic phosphinites/phosphin-
amides,[4] partly because of the well-documented configura-
tional instability of the P-chirogenic chlorophosphanes
from which they are usually derived.[5] Despite this prob-
lem, the concept of P-chirogenic sulfonamido–phosphin-
amides appealed to us, as it represents a class of recently
introduced hydrogen-bonding tautomeric ligands that have
been successfully applied in the field of cooperative and
supramolecular hydrogenation catalysis.[6] Sulfonamido–
phosphinamides are a versatile class of ligands, which exist
as a unique equilibrium between the PIII and the PV tauto-
mers that is shown on the NMR spectroscopic timescale in
CDCl3 (see ligand 1, Figure 1), hence the name META-
MORPhos.[6a]
Introduction
The field of organometallic chemistry and catalysis with
noninnocent ligands is dominated by achiral ligand scaf-
folds, and in most examples the noninnocence involves re-
dox chemistry of the particular ligand. Extension to chiral
ligands for asymmetric conversions as well as other types
of functional noninnocent behaviour of ligands is highly
interesting. The field of supramolecular hydrogen-bonding
ligand-mediated transition-metal catalysis typically involves
such cooperative and noninnocent effects as the functional
groups of the ligands may be reversibly deprotonated dur-
ing the catalytic cycle, opening up novel mechanistic path-
ways for certain reactions. Also, simple reversible hydrogen-
bond formation to a substrate, in addition to coordination
to a transition metal, could be considered as a form of non-
innocent behaviour of the ligand, moderating the activity
and selectivity of the complex. The application of P-centred
The pivotal question in this enterprise is to determine
whether the enantio-configuration of the chiral phosphorus
centre is retained or not in the course of the tautomeri-
zation. Here we show that P-chirogenic sulfonamido–phos-
phinamides are configurationally stable despite the dynamic
tautomeric equilibrium, even after prolonged exposure to
protic solvents such as iPrOH. The synthesis of three chiral
sulfonamido–phosphinamides has been achieved, with a
resolution method on a P-chirogenic sulfonamido–phos-
phinamide that affords greater than 99% ee. A small study
on the derived Rh complexes and the preliminary results in
the Rh-catalyzed asymmetric hydrogenation of alkenes is
presented.
[a] Van’t Hoff Institute for Molecular Sciences,
Postbus 94720, 1090 GE Amsterdam, The Netherlands
Fax: +31-20-5255604
E-mail: J.N.H.Reek@uva.nl
[b] Bijvoet Center for Biomolecular Research, Crystal and
Structural Chemistry, Utrecht University,
Padualaan 8, 3584CH Utrecht, The Netherlands
[c] Institut de Chimie Moléculaire de l’Université de Bourgogne
(ICMUB) - UMR 5260,
Université de Bourgogne, UFR Sciences et Techniques,
9 avenue Alain Savary, BP 47870, 21078 Dijon, France
[d] Department of Chemistry, University of Cologne,
Greinstrasse 4, 50939 Köln, Germany
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201100811 or from
the author.
496
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Tautomeric Sulfonamido–Phosphinamides
gand 3 was to be resolved by diastereomer separation of
(aR,R)-3 and (aR,S)-3 (using the enantiopure binaphthyl
substituent). For comparison, ligand 4 was prepared, which
does not need resolution, although chirality is incorporated
in the two appending (aR)-2,2Ј-dimethoxy-1,1Ј-binaphthyl
units. As expected, ligands 3 and 4 also exist as a tauto-
meric equilibrium between the PIII and PV isomers that is
slow on the NMR spectroscopic timescale in CDCl3.[7]
The first encouraging clue concerning the P-configura-
tional stability of sulfonamido–phosphinamides came from
the fact that ligand 3 was not obtained as a 50:50 dia-
stereomeric mixture, but with an initial 12% diastereomeric
excess (de) that did not change over time. This stereochemi-
cal stability was further confirmed by the separation ob-
tained on chiral analytical HPLC (ODH and AD for ligand
2, ODH for ligand 3), even while using protic iPrOH as a
cosolvent, a proton source that does not seem to affect the
stability nor the chirality in the prototropic equilibrium.
Interestingly, ligand rac-2 crystallizes as a hydrogen-
bonded “head-to-tail” dimer of (R)-2 with (S)-2 (see X-ray
structure in Figure 2). Likewise, crystallization of a dia-
stereomeric mixture of (aR,R)-3 + (aR,S)-3 revealed that
(aR,R)-3 and (aR,S)-3 also cocrystallize in a 1:1 ratio, in
an analogous “head-to-tail” disposition in which the two
diastereomers are strongly hydrogen bonded to one another
Figure 1. Tautomeric equilibrium of ligand 1 and 31P NMR spec-
troscopy profile (202.3 MHz, 223 K) of a 12.6 mm solution in
CDCl3.
Results and Discussion
Ligand Synthesis
For the purpose of our study, the METAMORPhos race-
mic ligand rac-2 was designed with a phenyl group and
an anisyl group, as it is one of the easiest and cheapest P-
chirogenic structures available (Scheme 1).[7] As in the case
of ligand 1, rac-2 also exists as an equilibrium between the
PIII and the PV tautomers (2a and 2b, respectively) that is
slow on the NMR spectroscopic timescale in CDCl3.[7] Li-
gand 3 was designed with an analogous electronic structure
to ligand 2, although with an extra chiral element based on
C2-chiral (aR)-2,2Ј-dimethoxy-1,1Ј-binaphthyl appending
the P-chirogenic centre (Scheme 1).[7] While we anticipated
resolving ligand rac-2 by using “external” chiral agents, li-
Figure 2. X-ray structure of ligand rac-2 (ORTEP view), 30% prob-
ability level, protons omitted for clarity. Selected atomic distances
[Å]: N1–P1 1.7321(15), N1–S1 1.6183(15), N1–H1 0.851(18), and
the full dimeric hydrogen-bonded structure (beneath).
Scheme 1. Synthesis of chiral METAMORPhos ligands rac-2,
(aR,R)-3 + (aR,S)-3 and (aR,aR)-4.
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(Figure 3). Interestingly, several distances vary significantly All first fractions were therefore combined and the Hex/
from one diastereomer to another. For example, N1A–S1A iPrOH solvents were evaporated. After a short filtration
[aR,R diastereomer, 1.628(3) Å] is longer than N1B–SIB through silica gel in ethyl acetate, a white powder could be
[aR,S diastereomer, 1.610(3) Å], and angle S1A–N1A–P1A obtained and characterized as (–)-2 (cumulated isolated
[125.12(17)°] is larger than S1B–N1B–P1B [123.28(18)°, yield: 7%).
Figure 3]. The hydrogen-bonding behavior between (aR,R)-
A very simple experiment to accurately measure the en-
3 and its diastereomer (aR,S)-3 is clear from the short dis- antiopurity of ligand (–)-2 was devised. When rac-2 was
tances: O1B–H1A 2.10(3) and O1A–H1B 2.18(3) Å (Fig- combined with the sulfonamido–phosphoramidite (aR)-
ure 3). Although it is usual for chiral compounds to cocrys- [5][Et3NH] and [Rh(acac)(CO)2] (a typical catalyst precur-
tallize both enantiomers in a 1:1 ratio, it is quite unusual to sor in hydroformylation, 1:1:1 respectively; acac = acetyl-
obtain crystals containing two different diastereomers, with acetonate) in CD2Cl2, a one-to-one mixture of square-
a consequently very low symmetry level in the crystal. We planar (aR,R)-[Rh(2c)(5H)(CO)] and (aR,S)-[Rh(2c)-
therefore appreciate the beauty and rarity of such a struc- (5H)(CO)] was formed by loss of [Et3NH][acac], with dis-
ture, but it is clear that a diastereomeric separation through tinctively different signals in the 1H and the 31P NMR spec-
crystallization is probably not feasible. Unfortunately, and tra (Figure 4). When resolved (–)-2 was combined with
in spite of many attempts, the diastereomeric mixture (aR)-[5][Et3NH] and [Rh(acac)(CO)2], only one set of sig-
(aR,R)-3 + (aR,S)-3 could not be separated by silica gel nals was obtained in the 1H and the 31P NMR spectra,
chromatography.
thereby indicating the formation of pure (aR,R)-[Rh(2c)-
(5H)(CO)] or (aR,S)-[Rh(2c)(5H)(CO)]. Although it is not
yet determined of which absolute configuration (–)-2 is, the
ligand was isolated with more than 99% ee.[7]
Figure 3. X-ray structure of ligand (aR,R)-3 and (aR,S)-3 (ORTEP
view, 50% probability level, protons omitted for clarity). Selected
atomic distances [Å]: N1A–P1A 1.728(3), N1B–P1B 1.735(3),
N1A–S1A 1.628(3), N1B–S1B 1.610(3), N1A–H1A 0.84(3), N1B–
H1B 0.84(3), O1B–H1A 2.10(3), O1A–H1B 2.18(3). Selected
atomic angles [°]: S1A–N1A–P1A 125.12(17), S1B–N1B–P1B
123.28(18); selected atomic torsion angles [°]: H1–N1B–S1B–O1B
+25(3), H1A–N1A–S1A-O1A –33(3).
Figure 4. 31P NMR (202.3 MHz, 298 K) spectroscopic profile of
(aR,R)-[Rh(2c)(5H)(CO)] and (aR,S)-[Rh(2c)(5H)(CO)] (phosphin-
amide area half spectrum, top), and of diastereopure [Rh{(–)-
2c}{(aR)-5H}(CO)] (beneath), both at 15.5 mm of [Rh] in CD2Cl2.
δ = 64.28 [dd, JP(–2),Rh = 113 Hz, JP(–2),P5 = 489 Hz, P of (–)-2],
62.10 [dd, 1JP(+2),Rh = 113 Hz, 2JP(+2),P5 = 488 Hz, P of (+)-2] ppm.
We were fortunately more successful with ligand rac-2,
which could be resolved using a chiral preparative HPLC
system, eluting with n-hexane/iPrOH (75:25) at a flow of
100 mLmin–1, in cycles of 50 mg of starting material dis-
solved in 10 mL of injection volume. Fraction collection
was monitored manually according to “real-time” UV de-
tection. The first fraction was typically collected between
1
2
An enantioselective synthesis of ligand 2 using (+)-eph-
26.5 and 29.2 min from the injection, for a total of 37 min edrine as chiral inductor was also attempted according to
per run. Unfortunately, due to a heavy tailing of both the methodology described by Jugé and co-workers.[3q] It is
enantiomers, only the first fraction was found enantiopure unclear why the condensation failed when using the de-
according to the post-run HPLC analysis of all fractions. scribed procedure with BuLi as a base. This could be attrib-
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Tautomeric Sulfonamido–Phosphinamides
uted to the low nucleophilicity and/or the steric hindrance
of the lithium salt. However, using a soft base such as Et3N
did allow the reaction to proceed, but yielded only racemic
product rac-2 in the resulting crude product (Scheme 2). We
assume that Et3N increases the lability of the chloride
anion, making the chiral chlorophosphane precursor less
enantiostable under the reaction conditions.
Scheme 3. Coordination modes of ligand 1, rac-2 and (aR,aR)-4 to
[Rh(acac)(CO)2] and [Rh(nbd)2BF4].
Rh-Catalyzed Asymmetric Hydrogenation
Sulfonamido–phosphinamides are known to alter the
mechanism of the Rh-catalyzed asymmetric hydrogenation
reaction of alkenes through supramolecular hydrogen-
bonding interactions and cooperative effects, which can be
monitored through kinetic order measurements.[6a] There-
fore, preliminary Rh-catalyzed asymmetric hydrogenation
experiments were performed on methyl 2-acetamidoacrylate
(MAA), based on enantiopure METAMORPhos (–)-2 and,
Scheme 2. Attempted enantioselective synthesis of P-chirogenic
METAMORPhos ligand 2 using the methodology based on (+)-
ephedrine.
Rh Complexation Studies
Preliminary complexation studies with [Rh(nbd)2BF4] (a for comparison, enantiopure (aR,aR)-4 {[Rh(nbd)2BF4]:
typical asymmetric hydrogenation catalyst precursor; nbd 1 mol-% and 1 mm, ligand: 2.2 mol-%, CH2Cl2, 50 bar H2,
= norbornadiene) showed that ligand rac-2 could furnish 298 K, 17 h}. Unfortunately only a very modest 25% ee
[Rh(2a)2(nbd)(BF4)], analogously to [Rh(1a)2(nbd)(BF4)]. could be obtained with ligand (–)-2, albeit with full conver-
In contrast, ligand (aR,aR)-4 was too bulky to form the sion. The application of ligand (aR,aR)-4 resulted in only
analogous cis-coordinated complex, and formed the μ-(P– traces of the hydrogenation product. We attribute this loss
N–S=O) hemilabile [Rh(4a)(nbd)(BF4)], leaving the extra of activity to the sheer bulk of the ligand, which likely
equivalent of ligand
4 uncoordinated. When using shields the active metal centre from the substrate, also with
[Rh(acac)(CO)2], however, trans-coordinated complexes of only one equivalent of ligand per Rh. Furthermore, full
the type [Rh(La)(Lc)(CO)] could be obtained by loss of conversion could be obtained for the analogous substrate
acac–H (L = ligand 1–4). The very broad NMR spec- methyl 2-acetamido-3-phenylacrylate using (–)-2 as the li-
troscopy signals observed for [Rh(4a)(4c)(CO)] suggest ste- gand, but the product was found to be racemic. With the
ric congestion at the metal centre.[7] Pressurization with H2 trisubstituted cyclic substrate, N-(3,4-dihydronaphthalen-2-
gas of [Rh(1a)2(nbd)(BF4)] leads to [Rh(1a)2(BF4)] by hy- yl)acetamide, neither ligands (–)-2 nor (aR,aR)-4 led to any
drogenation of the nbd, as indicated by NMR spectroscopy significant conversion (identical conditions). Elaborated
and mass spectrometry, in which case each ligand 1a coor- screening is required to identify the substrate classes, which
dinates the square-planar cationic RhI centre in a hemi-la- may lead to high activity and selectivity in the Rh-catalyzed
bile μ-(P–N–S=O) fashion, a likely resting state for the hy- asymmetric hydrogenation with P-chirogenic META-
drogenation reaction (Scheme 3).[7]
MORPhos ligands.
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129.22 (CH), 129.11 (CH), 129.01 (CH), 128.90 (CH), 128.62 (CH),
128.56 (CH), 128.25 (CH), 126.85 (s, CH), 126.42 (CH), 125.82 (s,
CH), 35.47 [s, (C3H7)–CH2–Ar], 33.21 [s, (C2H5)–CH2–CH2–Ar],
Conclusion
In conclusion, it has been shown that sulfonamido–phos-
phinamides (METAMORPhos), which exist as an equilib- 22.15 [s, CH3–CH2–(C2H4)–Ar], 13.86 [s, CH3–(C3H6)–Ar] ppm.
rium between the PIII and the PV tautomers that is slow on
Note: in these concentrated conditions, most of the above-men-
tioned lines belong to major tautomer 1a. (1H,15N)-HMQC NMR
the NMR spectroscopic timescale in CDCl3, could be made
P-chirogenic and subsequently resolved. Specifically, the
(30.42 MHz, 332 mm in CDCl3, at natural abundance, 298 K): δ =
1
1
–270.5 (dd, JN,H = 84 Hz, JN,P = 63 Hz, tautomer 1a) ppm. MS
(FAB+): m/z calcd. for C22H25NO2PS+ [M + H]+: 398.1344; found
398.1340.
resolution of P-chirogenic sulfonamido–phosphinamide 2
was found possible with more than 99% ee; as far as we
know, the first P-chirogenic enantiopure METAMORPhos
ligand. The prototropic equilibrium, although involving the
reversible protonation of the C1-chiral phosphorus centre,
does not lead to racemization. This means the prototropic
equilibrium involves the protonation of systematically the
same face of the phosphorus atom (chiral memory process),
and that neither the PIII nor the PV tautomers are suscepti-
ble to inversion, even under prolonged exposure to a protic
solvent such as iPrOH. We expect that this discovery will
have an impact on phosphorus-mediated asymmetric catal-
Racemic METAMORPhos rac-2: 2-Bromoanisole (44 mmol) was
dissolved in THF (15 mL) and was cooled to –78 °C. A solution of
nBuLi (2.5 m in hexanes, 44 mmol) was added dropwise, and the
solution was stirred at room temp. for 1 h. The resulting solution
was added dropwise on a solution of racemic 1-chloro-N,N-diethyl-
1-phenylphosphinamine (44 mmol in 400 mL of Et2O, –78 °C) and
left to stir back to room temp. The solvents were evaporated and
the crude product was extracted with CH2Cl2/H2O. The organic
layers were dried on MgSO4 and evaporated to give a very viscous
light yellow oil: racemic N,N-diethyl-1-(2-methoxyphenyl)-1-phen-
ysis, especially that which involves cooperative or supra- ylphosphinamine (93% isolated yield). The substance (8.3 mmol)
molecular hydrogen-bonding ligands.[6]
was exposed to saturated HCl in toluene (80 mL) and stirred at
room temp. for 1 h (conversion to the chlorophosphane was moni-
tored by 31P NMR spectroscopy). A third of the solution was then
evaporated, hexanes (40 mL) were added and the resulting turbid
solution was filtered. 4-Butylbenzenesulfonamide (8.3 mmol) was
Experimental Section
General Procedures: All reactions were carried out in dry glassware
under an argon or nitrogen atmosphere. Every solution addition or
transfer was performed by means of syringes. All solvents were
dried and distilled with standard procedures. NMR spectroscopy
experiments were performed either on a Varian Inova500 spectrom-
eter (1H: 500 MHz, 31P: 202.3 MHz, 13C: 125.7 MHz) or on a Var-
ian Mercury300 (1H: 300.1 MHz, 19F: 282.4 MHz). Chemical shifts
are referenced to the solvent signal (δ = 7.26 ppm in 1H and
77.0 ppm in 13C NMR for CDCl3). Chemical shifts in the 31P NMR
spectroscopic experiments are referenced from H3PO4 as an exter-
nal standard. The 15N NMR spectroscopic experiment was re-
corded using a (1H,15N) HMQC sequence on a Bruker DRX-300
operating a 30.42 MHz 15N frequency.[8] The chemical shift is refer-
enced to nitromethane = 0 ppm. Conversions and enantiomeric ex-
cess for the asymmetric hydrogenation reactions were determined
by gas chromatography on a Focus CHIRALSIL DEX-CB and/or
on a Ph Betadex FT. The chiral preparative HPLC system was
CHIRALPAK AD, 5 cm inside diameter, 50 cm length, particle size
20 micron from Daicel Chemical Industries. Ligands 1 and 5 were
prepared according to the literature.[6a] 4-Butylbenzenesulfonamide
and (R)-2,2Ј-dimethoxy-1,1Ј-binaphthyl were always dried by co-
evaporation in dry and distilled toluene before use.
dissolved in THF (15 mL) and Et3N (32.5 mmol). The previous
chlorophosphane solution was added dropwise at room temp. and
left to stir overnight. The solvents were evaporated and the prod-
uct, racemic METAMORPhos rac-2, was purified by silica gel
chromatography (toluene/ethyl acetate, 9:1). The product was iso-
lated as a white powder in 34% isolated yield, characterized by X-
ray crystallography (Figure 2). Crystallization method: slow dif-
fusion of hexanes on top of a CH2Cl2 solution in a closed glass
pipette (+4 °C). 31P NMR (202.3 MHz, 8.9 mm in CDCl3, 223 K):
2
δ = +32.50 (br. d, JP,H = 5 Hz, 58% of the integration: tautomer
1
2a), –2.16 (br. d, JP,H = 509 Hz, 42% of the integration, tautomer
2b) ppm. 31P{1H} NMR (202.3 MHz, CD2Cl2, 298 K): δ = +31.79
1
(s, tautomer 2a), –1.53 (s, tautomer 2b) ppm. H NMR (500 MHz,
CD2Cl2, 298 K): δ = 8.26 (d, 1JH,P = 509 Hz, P–H of tautomer 2b),
2
7.9–6.8 (dense aromatic signal range), 6.20 (d, JH,P = 5 Hz, NH
of tautomer 2a), 3.73 (small s, methoxy unit of tautomer 2b), 3.56
(large s, methoxy unit of tautomer 2a), 2.63 (t, 3J = 8 Hz, CH2–Ar
3
of tautomer 2a), 2.59 (t, J = 8 Hz, CH2–Ar of tautomer 2b), 1.58
(m, CH2–CH2–Ar of 2a and 2b), 1.32 (m, CH2–CH2–CH2–Ar of
2a and 2b), 0.93 (t, 3J = 7.5 Hz, CH3–C3H6–Ar of 2a and 2b) ppm.
13C NMR (125.7 MHz, CD2Cl2, 298 K): δ = 161.29 (br. s, Cquat),
148.84 (s, Cquat), 139.65 (s, Cquat), 139.14 (d, JC,P = 11 Hz, Cquat),
136.20–126.19 (aromatic signal range, exclusively CH lines), 124.60
(d, JC,P = 17 Hz, Cquat), 122.03–111.78 (aromatic signal range, ex-
clusively CH lines), 56.28 (very small s, methoxy unit of 2b), 56.07
(s, methoxy unit of 2a), 35.96 (s, CH2–Ar of 2a), 35.88 (very small
s, CH2–Ar of 2b), 33.98 (very small s, CH2–CH2–Ar of 2b), 33.82
(s, CH2–CH2–Ar of 2a), 22.76 (s, CH2–CH2–CH2–Ar, 2a and 2b),
14.21 (s, CH3–C3H6–Ar, 2a and 2b) ppm. Note: under these con-
centrated conditions, the lines of tautomer 2b are very small. For
the Cquat, only the lines of 2a are visible.
METAMORPhos Ligand 1: See the ref.[6a] 31P NMR (202.3 MHz,
2
12.6 mm in CDCl3, 223 K): δ = 33.99 (d, JP,H = 7 Hz, tautomer
1
1a), 6.66 (dm, JP,H = 490 Hz, tautomer 1b) ppm. The tautomeric
1
ratio 1a/1b was found at 0.85 according to integrations. H NMR
1
(500 MHz, 1.7 mm in CDCl3, 223 K): δ = 8.14 (d, JH,P = 490 Hz,
PH of tautomer 1b), 7.79–7.04 (aromatic region: tautomer 1a and
1b), 5.53 (d, 2JH,P = 7 Hz, NH of tautomer 1a), 2.67 [t, 3J = 7.5 Hz,
(C3H7)–CH2–Ar of tautomer 1a], 2.53 [t, 3J = 7.5 Hz, (C3H7)–
CH2–Ar of tautomer 1b], 1.57 [m, (C2H5)–CH2–CH2–Ar of tauto-
mer 1a], 1.47 [m, (C2H5)–CH2–CH2–Ar of tautomer 1b], 1.33–1.20
[m, CH3–CH2–(C2H4)–Ar, of tautomer 1a and tautomer 1b], 0.93–
0.88 [m, CH3–(C3H6)–Ar, of tautomer 1a and tautomer 1b] ppm.
13C NMR (125.7 MHz, CDCl3, 298 K): δ = 148.25 (s, Cquat), 138.81
Resolution of Enantiopure METAMORPhos (–)-2: See main text.
[α]2D2 = –55.1 (c = 0.2, CH2Cl2).
Mixture (aR,R) + (aR,S)-3: Crystalline (R)-2,2Ј-dimethoxy-1,1Ј-bi-
(s, Cquat), 137.41 (d, JC,P = 12.7 Hz, Cquat), 133.48 (s, CH), 131.98 naphthyl (15.9 mmol) was slowly dissolved in THF (315 mL). A
(CH), 131.89 (CH), 131.44 (CH), 131.27 (CH), 129.68 (s, CH), solution of nBuLi (2.5 m in hexanes, 16.7 mmol) was added drop-
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Tautomeric Sulfonamido–Phosphinamides
wise at room temp. and with strong stirring. The resulting dark
brown solution was stirred at room temp. for 1 h. Racemic 1-
chloro-N,N-diethyl-1-phenylphosphinamine (15.9 mmol in 140 mL
of Et2O) was added to it dropwise at room temp. The resulting
solution was left to stir at room temp. for 1 h, and the solvents
were evaporated. The crude product was extracted with CH2Cl2/
H2O, the organic layers were dried with MgSO4 and the solvents
were evaporated. The crude product was added to Et2O (150 mL)
yielding a white suspension that was filtered off. The organic layers
were combined and solvents were evaporated to give a light yellow
oil. The product was subjected to a silica gel purification in
CH2Cl2, and then collected by flushing the silica gel with ethyl
acetate. The resulting white crispy powder was identified as the
corresponding P-chirogenic secondary phosphane derivative: com-
pound A (Scheme 1); isolated yield: 25%. 31P NMR (202.3 MHz,
methoxy unit of tautomer 3a), 2.62 (very br. s, methoxy unit of
tautomer 3a), 2.56 (br. m, CH2–Ar signal range), 1.54–0.84 (broad
alkyl signal range) ppm. Note: the signals of tautomer 3b are small
and broad. 13C NMR (125.7 MHz, CD2Cl2, 298 K): δ = 157.14
(very br., Cquat), 155.59 (Cquat), 155.40 (Cquat), 149.08 (Cquat),
149.04 (Cquat), 139.91 (Cquat), 139.85 (Cquat), 139.66 (Cquat), 139.57
(Cquat), 135.98 (Cquat), 135.60–113.47 (dense aromatic signal
range), 60.55 (br. s, methoxy unit, possibly 2 signals overlapping),
56.94 (s, methoxy unit), 56.60 (s, methoxy unit), 35.94 (s, CH2–Ar),
33.71 (s, CH2–CH2–Ar), 22.79 (s, CH2–CH2–CH2–Ar, first dia-
stereomer of 3a), 22.73 (s, CH2–CH2–CH2–Ar, other diastereomer
of 3a), 14.20 (s, CH3–C3H6–Ar, first diastereomer of 3a), 14.14 (s,
CH3–C3H6–Ar, other diastereomer of 3a) ppm. Note: in this case
the lines of tautomer 3b are too small to be accurately reported.
(aR,aR)-4:
Crystalline
(R)-2,2Ј-dimethoxy-1,1Ј-binaphthyl
1
CDCl3, 298 K): δ = +17.24 (br. d, JP,H = 499 Hz, major dia-
(28.6 mmol) was slowly dissolved in THF (250 mL). A solution of
nBuLi (2.5 m in hexanes, 29.2 mmol) was added dropwise at room
temp. and with strong stirring. The resulting dark brown solution
was stirred at room temp. for 1 h. The solution was cooled to 0 °C
and a solution of 1,1-dichloro-N,N-diethylphosphinamine in Et2O
(14.3 mmol in 150 mL) was added dropwise. The resulting clear
solution was left to stir at room temp. overnight. The solvents were
evaporated and the crude product was directly purified by silica gel
chromatography in CH2Cl2. The product was then recovered by
flushing the silica with ethyl acetate, and the solvent was evapo-
rated to a white solid (the corresponding secondary phosphane ox-
ide). Isolated yield: 25%. 31P NMR (121.5 MHz, CDCl3, 298 K): δ
1
stereomer), +16.86 (br. d, JP,H = 500 Hz, minor diastereomer)
1
ppm. 1H NMR (300 MHz, CDCl3, 298 K): δ = 8.34 (d, JH,P
=
1
500 Hz, PH of minor diastereomer), 8.33 (d, JH,P = 499 Hz, PH
3
of major diastereomer), 8.56 (d, JH,P = 15 Hz, aromatic H of
3
naphthyl unit ortho to P, minor diastereomer), 8.53 (d, JH,P
=
16 Hz, aromatic H of naphthyl unit ortho to P, major dia-
stereomer), 8.01–7.03 (aromatic region), 3.76 (s, methoxy unit of
major diastereomer), 3.74 (s, methoxy unit of minor diastereomer),
3.05 (s, other methoxy unit of major diastereomer), 2.98 (s, other
methoxy unit of minor diastereomer) ppm. According to the rela-
tive integration of the last two signals, the diastereomeric ratio is
64:36 (de = 28%). Compound A was dissolved in PCl3 (15 mL) and
heated at +100 °C for 2 h. The solution was then evaporated, and
the crude product was dissolved in toluene (5 mL). The solution
was again evaporated to a white foam. The product was finally
dissolved in THF (25 mL). 31P NMR (121.5 MHz, unlocked,
298 K): δ = +78.3 (s, first diastereomer), +77.3 (s, second dia-
stereomer) ppm, the diastereomeric ratio is 1:1 (de = 0%). NMR
spectroscopic yield: quantitative. 4-Butylbenzenesulfonamide
(4.2 mmol) was dissolved in THF (50 mL) and a solution of nBuLi
(2.5 m in hexanes, 4.2 mmol) was added dropwise at 0 °C under
strong stirring. The resulting white suspension was stirred for 1 h
and the previous solution was added dropwise at 0 °C, which led
to an almost clear solution that was stirred at room temp. over-
night. The solvents were evaporated, and the product was purified
by silica gel chromatography (toluene/ethyl acetate 9:1). A white
powder was obtained; isolated yield: 48%. Characterized by X-ray
crystallography (Figure 3). Crystallization method: slow diffusion
of hexanes on top of a CH2Cl2 solution in a closed glass pipette
(+4 °C). 31P NMR (202.3 MHz, CDCl3, 298 K): δ = +33.75 (br. s,
tautomer 3a), +32.78 (s, tautomer 3a of corresponding dia-
1
3
1
= +11.36 (dt, d: JP,H = 516 Hz, t: JP,H = 16 Hz) ppm. H NMR
(300 MHz, CDCl3, 298 K): δ = 8.60 (d, 1JH,P = 516 Hz, P–H), 8.50
3
3
(d, JH,P = 16 Hz, aromatic H ortho to P), 8.45 (d, JH,P = 16 Hz,
other aromatic H ortho to P, diastereotopic to the previous), 8.00–
7.02 (aromatic area), 3.73 (s, methoxy unit), 3.67 (s, methoxy unit),
3.12 (s, methoxy unit), 3.07 (s, methoxy unit) ppm. The product
(3.4 mmol) was dissolved in PCl3 (40 mL) and heated at +100 °C
for 1 h. The solution was then evaporated, and the crude product
was dissolved in toluene (5 mL). The solution was again evaporated
to a white foam. The product was then dissolved in THF (20 mL).
31P NMR (121.7 MHz, unlocked, 298 K): δ = +74.57 (s) ppm.
NMR spectroscopic yield: quantitative. 4-Butylbenzenesulfon-
amide (7.44 mmol) was dissolved in THF (100 mL) and a solution
of nBuLi (2.5 m in hexanes, 7.44 mmol) was added dropwise at 0 °C
under strong stirring. The resulting white suspension was stirred
for 1 h and the previous solution was added dropwise, which led to
an almost clear solution that was stirred at room temp. overnight.
The solvents were evaporated, and the product was purified by sil-
ica gel chromatography in 100% CH2Cl2. A white powder was ob-
tained; isolated yield: 53%. (Note: the large excess amount of acti-
vated sulfonamide is required because the previous chlorophos-
phane is less reactive due to steric congestion). HRMS (FAB+): m/z
1
stereomer), +0.03 (d, JP,H ≈ 502 Hz, tautomer 3b of the dia-
1
stereomer at +33.75 ppm), –0.30 (d, JP,H = 502 Hz, tautomer 3b
of diastereomer at +32.78) ppm. Peak assignment was determined
by 31P NMR spectroscopic analysis of a diastereomerically en-
riched sample recovered from the mother solution of crystalli-
zation: lines at +33.75 and +0.03 ppm slightly but significantly de-
creased together relative to the two other lines and correspond
therefore to the same diastereomer. The diastereomeric excess is
therefore measured at de = 12% in the original batch, according to
integrations. 31P{1H} NMR (202.3 MHz, CD2Cl2, 298 K): δ =
+32.45 (s, 3a), +31.12 (s, other diastereomer of 3a), +0.35 (s, 3b),
calcd. for C54H49NO6PS+ [M + H]+: 870.3018; found 870.3021. 31
NMR (202.3 MHz, 13.4 mm in CDCl3, 298 K): δ = +27.44 (dt, d:
P
3
2JPNH = 3 Hz, t: JP,H = 10 Hz, 83% of the integration, tautomer
1
3
4a), –5.80 (dt, d: JP,H = 524 Hz, t: JP,H = 17 Hz, 17% of the
integration, tautomer 4b) ppm. 31P{1H} NMR (202.3 MHz,
13.4 mm in CDCl3, 298 K): δ = +27.43 (s, tautomer 4a), –5.80 (s,
tautomer 4b) ppm. 1H NMR (500 MHz, 13.4 mm in CDCl3,
1
298 K): δ = 8.71 (d, JH,P = 524 Hz, P–H of tautomer 4b), 8.44 (d,
3
3JH,P = 17 Hz, aromatic H ortho to P, tautomer 4b), 8.38 (d, JH,P
+0.19 (s, other diastereomer of 3b) ppm. 1H NMR (500 MHz,
= 17 Hz, H ortho to P, diastereotopic to the previous, 4b), 8.20–
2
2
CD2Cl2, 298 K): δ = 9.01–6.86 (aromatic area), 6.30 (d, JH,P
=
6.81 (aromatic area), 6.70 (d, JH,P = 3 Hz, NH of tautomer 4a),
2
6 Hz, NH of tautomer 3a), 6.23 (d, JH,P = 5 Hz, NH of tautomer
3a of corresponding diastereomer), 3.78 (s, methoxy unit of tauto-
mer 3a), 3.76 (s, methoxy unit of tautomer 3a), 2.66 (very br. s,
3.74 (small s, methoxy unit of tautomer 4b), 3.73 (large s, methoxy
unit of tautomer 4a), 3.63 (large s, methoxy unit of tautomer 4a),
3.59 (small s, methoxy unit of tautomer 4b), 3.03 (small s, methoxy
Eur. J. Inorg. Chem. 2012, 496–503
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
501

J. N. H. Reek et al.
FULL PAPER
unit of tautomer 4b), 2.99 (small s, methoxy unit of tautomer 4b),
2.74 (large s, methoxy unit of tautomer 4a), 2.73 (large s, methoxy
unit of tautomer 4a), 2.52 (small t, 3J = 8 Hz, CH2–Ar of tautomer
unit), 3.48 (s, methoxy unit), 2.68–0.84 (broad and crowded alkyl
region). Note: the 4 methoxy groups are of approximately equal
intensity at 298 K (the 2 diastereomeric complexes are in equal
amounts), but one of the diastereomers seems to be favored at
3
4b), 2.39 (≈t, J = 8 Hz, CH2–Ar of tautomer 4a), 1.54–0.78 (alkyl
region) ppm. 13C NMR (125.7 MHz, 13.4 mm in CDCl3, 298 K): δ 223 K in a roughly 2:1 ratio according to the 1H NMR spec-
= 156.86 (Cquat), 156.78 (Cquat), 156.67 (Cquat), 156.60 (Cquat), troscopy integrations of the methoxy units. The structure of the
154.93 (Cquat), 154.83 (Cquat), 147.86 (Cquat), 139.13 (Cquat), complex was assigned by analogy with [Rh(1a)(1c)(CO)] (see
134.93–123.54 (dense aromatic area, Cquat and CH), 118.51 (Cquat),
above).[6a]
118.44 (Cquat), 113.70 (CH), 113.08 (CH), 60.71 (small s, CH3–O
[Rh(3a)(3c)(CO)]: Diastereomeric mixture (aR,R)
+ (aR,S)-3
of tautomer 4b), 60.69 (small s, CH3–O of tautomer 4b), 60.39 (d,
(0.0388 mmol) was added to [Rh(acac)(CO)2] (0.0194 mmol) and
dissolved in CD2Cl2 (0.5 mL). 31P{1H} NMR (202.3 MHz,
39.9 mm in CD2Cl2, 298 K): δ = +71.10–57.47 (very br. m, lines of
3a and 3c) ppm. No free ligand was observed. 1H NMR (500 MHz,
39.9 mm in CD2Cl2, 298 K): δ = +15.54 (s, H of free acac–H) ppm.
The rest of the spectrum is extremely broad.
4
4JC,P = 1 Hz, CH3–O ortho to P of tautomer 4a), 60.19 (d, JC,P
=
1 Hz, CH3–O ortho to P of tautomer 4a, diastereotopic from pre-
vious), 56.38 (s, CH3–O of tautomer 4a), 56.34 [small s, CH3–O of
tautomer 4b (the 4th methoxy of 4b is overlapping)], 56.19 (s, CH3–
O of tautomer 4a), 35.39 (small s, CH2–Ar of tautomer 4b), 35.30
(s, CH2–Ar of tautomer 4a), 33.23 (small s, CH2–CH2–Ar of tauto-
mer 4b), 32.90 (s, CH2–CH2–Ar of tautomer 4a), 22.24 (small s,
CH2–C2H4–Ar of tautomer 4b), 22.15 (s, CH2–C2H4–Ar of tauto-
mer 4a), 13.87 (small s, CH3–C3H6–Ar of tautomer 4b), 13.77 (s,
CH3–C3H6–Ar of tautomer 4a) ppm.
[Rh(4a)(4c)(CO)]: (aR,aR)-4 (0.0194 mmol) was added to
[Rh(acac)(CO)2] (0.0097 mmol) and dissolved in CD2Cl2 (0.6 mL).
31P{1H} NMR (202.3 MHz, 16.1 mm in CD2Cl2, 298 K): δ =
+80.49–48.41 (very br. m, lines of 4a and 4c) ppm. No free ligand
1
was observed. H NMR (500 MHz, 16.1 mm in CD2Cl2, 298 K): δ
[Rh(2c)(5H)(CO)]: Racemic ligand rac-2 or enantiopure ligand (–)-
= +15.53 (s, H of free acac–H), 9.71–6.63 (very broad and dense
aromatic region), 6.40 (br. s, possibly the NH of 4a), 5.35 (s, acac–
H), 3.75 (very br. s, methoxy area), 3.70 (very br. s, methoxy area),
3.45 (extremely br. s, methoxy area), 2.85 (very br. s, methoxy area),
2.70 (very br. s, methoxy area), 2.56 (very br. s, CH2–Ar area),
2.39–0.76 (broad and dense alkyl area) ppm.
2
(0.0078 mmol) was combined with ligand (R)-[5][Et3NH]
(0.0081 mmol) and [Rh(acac)(CO)2] (0.0078 mmol) and sub-
sequently dissolved in CD2Cl2 (0.5 mL). 31P NMR (202.3 MHz,
15.5 mm in CD2Cl2, 298 K): δ = +149.14 [dd, 1JP,Rh = 195 Hz, 2JP,P
1
= 489 Hz, P of (R)-5H associated with (+)-2], +148.69 [dd, JP,Rh
2
= 196 Hz, JP,P = 488 Hz, P of (R)-5H associated with (–)-2],
[Rh(1a)2(nbd)(BF4)]: Ligand 1 (0.0134 mmol) and [Rh(nbd)2BF4]
(0.0067 mmol) were combined and dissolved in CDCl3 (0.6 mL).
31P{1H} NMR (202.3 MHz, 11.1 mm in CD2Cl2, 298 K): δ =
1
2
+64.28 [dd, JP,Rh = 113 Hz, JP,P = 489 Hz, P of (–)-2 associated
1
2
with (R)-5H], +62.10 [dd, JP,Rh = 113 Hz, JP,P = 488 Hz, P of
(–)-2 associated with (R)-5H] ppm. H NMR (500 MHz, 15.5 mm
1
1
1
+60.46 (d, JP,Rh = 167 Hz) ppm. H NMR (500 MHz, 11.1 mm in
CD2Cl2, 298 K): δ = 7.84–7.04 (br. and dense aromatic region).
6.76 (very br. s, alkene H of free nbd, possibly overlapping with
NH of 1a), 4.74 (coordinated nbd), 4.71 (coordinated nbd), 4.39
(s, coordinated nbd), 3.79 (s, coordinated nbd), 3.58 (s, coordinated
nbd), 2.66 (t, 3J = 7.5 Hz, CH2–Ar of 1a), 1.98 (br. s, free nbd),
in CD2Cl2, 298 K): δ = 15.55 (s, acidic H of [acac][Et3NH]), 9.35
(very br. s, NH of 5H), 8.05–6.79 (dense aromatic signal range),
5.56 (s, middle CH of [acac][Et3NH]), 3.62 [s, methoxy unit of (–)-
2 associated with (R)-5H], 3.51 [s, methoxy unit of (+)-2 associated
with (R)-5H], 2.84–0.83 (alkyl region) ppm.
3
1.65–1.07 (alkyl region), 0.95 (t, J = 7 Hz, CH3–C3H6–Ar of 1a)
[Rh(1a)(1c)(CO)]: METAMORPhos ligand 1 (0.0350 mmol) and
[Rh(acac)(CO)2] (0.0174 mmol) were combined and dissolved in
CDCl3 (2.76 mL) leading to a clear yellow solution (6.3 mm of
[Rh]). A sample of this solution (600 μL) was transferred to an
NMR spectroscopy tube. 31P{1H} NMR (202.3 MHz, 13.5 mm in
ppm.
[Rh(2a)2(nbd)(BF4)]: Ligand rac-2 (0.0160 mmol) was added to
[Rh(nbd)2BF4] (0.0080 mmol) and dissolved in CD2Cl2 (0.5 mL).
31P{1H} NMR (202.3 MHz, 16.1 mm in CD2Cl2, 298 K): δ =
1
2
2
CDCl3, 223 K): δ = 69.79 (dd, JPc,Rh = 113.2 Hz, JPc,Pa
=
=
+59.84 {d, JP,Rh = 170 Hz, rac- or meso-[Rh(2a)2(nbd)(BF4)]},
1
2
2
335.6 Hz, P of 1c), 66.49 (dd, JPa,Rh = 129.4 Hz, JPa,Pc
+58.41 {d, JP,Rh = 169 Hz, meso- or rac-[Rh(2a)2(nbd)(BF4)]}
335.6 Hz, P of 1a) ppm. 1H NMR (500 MHz, 6.3 mm in CDCl3,
223 K): δ = 7.86–7.32 (br. aromatic region), 7.14 (d, J = 8 Hz, Ar
H), 6.83 (d, J = 8 Hz, Ar H), 6.77 (d, J = 8.5 Hz, Ar H), 6.73 (d,
2JH,P = 16 Hz, NH of 1a), 5.58 (s, acac–H), 2.63 [t, 3J = 8 Hz,
(C3H7)–CH2–Ar: 1a], 2.50 [t, 3J = 7.5 Hz, (C3H7)–CH2–Ar: 1c],
2.09 (s, acac–H), 1.56 [m, (C2H5)–CH2–CH2–Ar: 1a], 1.47 [m,
(C2H5)–CH2–CH2–Ar: 1c], 1.34–1.24 [m, CH3–CH2–(C2H4)–Ar, 1a
and 1c], 0.92–0.88 [m, CH3–(C3H6)–Ar of both 1a and 1c] ppm.
ppm. The ratio between the former and the latter diastereomers is
approximately 1.2:1, respectively, under these conditions. 1H NMR
(500 MHz, 16.1 mm in CD2Cl2, 298 K): δ = 7.86–6.78 (br. aromatic
region), 6.41 (br. s, NH of rac or meso diastereomer), 6.34 (br. s,
NH of meso or rac diastereomer), 4.52 (br. s), 4.41 (br. s), 3.86 (br.
s), 3.64 (s, possibly CH3–O, with overlapping), 3.63 (s, possibly
CH3–O, with overlapping), 3.61 (s, possibly CH3–O, with overlap-
3
ping), 2.71 (br. m, CH2–Ar), 2.00–1.31 (alkyl region), 1.00 (t, J =
7 Hz, CH3–C3H6–Ar) ppm.
[Rh(2a)(2c)(CO)]: Racemic ligand rac-2 (0.0194 mmol) was added
to [Rh(acac)(CO)2] (0.0099 mmol) and dissolved in toluene (1 mL),
and then evaporated. The process was repeated thrice (removal of
acac–H) and the complex was finally dissolved in CDCl3 (0.53 mL).
[Rh(4a)(nbd)(BF4)]. Procedure A: Ligand (aR,aR)-4 (0.0135 mmol)
was added to [Rh(nbd)2BF4] (0.0067 mmol) and dissolved in
CD2Cl2 (0.55 mL). 31P{1H} NMR (202.3 MHz, 12.1 mm in
31P NMR (202.3 MHz, 18.6 mm in CDCl3, 223 K): δ = +67– CD2Cl2, 298 K): δ = +79.77 (d, JP,Rh = 264 Hz, presumably a
1
60 ppm (very br. m, lines of 2a and 2c) ppm. No free ligand ob-
mono-coordinated species), +56.2 (very br. m, also a mono-coordi-
nated species), +25.4 (very br. s, free ligand tautomer 4a), –5.18 (s,
free ligand tautomer 4b) ppm.
served. From the tips of certain lines above the broad multiplet,
2
one of the trans JP,P can be estimated at approximately 352 Hz,
1
and one of the JP,Rh of 2a can be estimated at approximately
Procedure B: Ligand (aR,aR)-4 (0.0080 mmol) was added to
[Rh(nbd)2BF4] (0.0080 mmol) and dissolved in CD2Cl2 (0.5 mL).
31P{1H} NMR (202.3 MHz, 16.1 mm in CD2Cl2, 298 K): δ =
1
119 Hz. H NMR (500 MHz, 18.6 mm in CDCl3, 223 K): δ = very
broad spectrum: 8.20–6.74 (br. aromatic region), 6.53 (br. s, NH of
2a), 3.58 (s, methoxy unit), 3.55 (s, methoxy unit), 3.50 (s, methoxy
1
+67.24 {br. d, JP,Rh = 181 Hz, [Rh(4a)(nbd)(BF4)]} ppm. 1H
502
www.eurjic.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 496–503

Tautomeric Sulfonamido–Phosphinamides
Knowles, M. J. Sabacky, B. D. Vineyard, J. Chem. Soc., Chem.
Commun. 1972, 10; p) J.-M. Camus, J. Andrieu, P. Richard, R.
Poli, C. Darcel, S. Jugé, Tetrahedron: Asymmetry 2004, 15,
2061; q) C. Bauduin, D. Moulin, E. B. Kaloun, C. Darcel, S.
Jugé, J. Org. Chem. 2003, 68, 4293; r) F. Chaux, S. Frynas, H.
Laureano, C. Salomon, G. Morata, M.-L. Auclair, M. Stephan,
R. Merdes, P. Richard, M.-J. Ondel-Eymin, J.-C. Henry, J. Bay-
ardon, C. Darcel, S. Jugé, C. R. Chim. 2010, 13, 1213; s) J. J.
Gammon, P. O’Brien, B. Kelly, Org. Lett. 2009, 11, 5022; t) Z.-
C. Duan, X.-P. Hu, C. Zhang, Z. Zheng, J. Org. Chem. 2010,
75, 8319; u) J. Deng, Z.-C. Duan, J.-D. Huang, X.-P. Hu, D.-
Y. Wang, S.-B. Yu, X.-F. Xu, Z. Zheng, Org. Lett. 2007, 9,
4825; v) W. Chen, S. M. Roberts, J. Whittall, A. Steiner, Chem.
Commun. 2006, 2916. For a review, see: w) A. Grabulosa, J.
Granell, G. Muller, Coord. Chem. Rev. 2007, 251, 25.
For examples of P-chirogenic phosphonites and phosphinam-
ides, see: a) B. Pugin, M. Lotz, H. Landert, A. Wyss, R. Aar-
doom, B. Gschwend, A. Pfaltz, F. Spindler, PCT Int.
Appl. 2009, WO 2009065784 A1 20090528; b) B. Pugin, H.
Landert, B. Gschwend, A. Pfaltz, F. Spindler, PCT Int.
Appl. 2009, WO 2009065783 A1 20090528; c) C. Darcel, D.
Moulin, J.-C. Henry, M. Lagrelette, P. Richard, P. D. Harvey,
S. Jugé, Eur. J. Org. Chem. 2007, 13, 2078; d) D. Moulin, C.
Darcel, S. Jugé, Tetrahedron: Asymmetry 1999, 10, 4729.
NMR (500 MHz, 16.1 mm in CD2Cl2, 298 K): δ = 8.47–7.00 (dense
aromatic region), 6.77 (d, JH,P = 8.5 Hz, NH of coordinated 4a),
5.03 (very br. signal), 4.15 (br. s), 3.88–0.91 (dense alkyl region)
2
ppm. Distinct signals: δ = 3.82 (s, CH3–O), 3.73 (s, CH3–O), 2.70
3
(t, J = 8 Hz, CH2–Ar), 2.61 (br. s, CH3–O), 2.49 (br. s, CH3–O)
ppm.
Asymmetric Hydrogenation Experiments: Typically, a 15 mL pres-
sure reactor containing a glass insert was subsequently charged,
under inert conditions, with a solution of ligand (1 mL), a solution
of [Rh(nbd)2BF4] (0.5 mL), and a solution of the substrate (1 mL),
all in dichloromethane at the needed concentrations. The solution
was then exposed to 50 bar of H2, and left to stir at room tempera-
ture (298 K) for 17 h (vortex-type stirring: 300 rpm). Conversions
and enantioselectivities were determined by chiral GC.
[4]
CCDC-836862 (for 2) and -836863 (for 3) contain the supplemen-
tary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
Supporting Information (see footnote on the first page of this arti-
1
cle): H, 31P and 13C NMR spectroscopic data.
[5]
[6]
For a comprehensive study on the tendency of P-chirogenic
chlorophosphanes to racemize, see: S. Humbel, C. Bertrand, C.
Darcel, C. Bauduin, S. Jugé, Inorg. Chem. 2003, 42, 420.
Acknowledgments
Dr. Tatiana Besset and Dr. Mathieu Branca are acknowledged for
discussions. The National Research School, Combination Catalysis
Controlled by Chemical Design (NRSC Catalysis), BASF Neder-
land B.V., The Netherlands, and the Fonds der Chemischen Indus-
trie are acknowledged for financial support. This work was also
supported in part (A. L. S.) by the Council for the Chemical Sci-
ences of The Netherlands Organization for Scientific Research
(CW-NWO). Han Peeters is acknowledged for the mass spectrome-
try experiments, and Jan Meine Ernsting for the 15N NMR spec-
troscopy characterization of ligand 1.
For our previous works concerning sulfonamido–phosphorus
ligands, see: a) F. W. Patureau, M. Kuil, A. J. Sandee, J. N. H.
Reek, Angew. Chem. 2008, 120, 3224; Angew. Chem. Int. Ed.
2008, 47, 3180. Highlight: b) H. Yamamoto, P. Li, Synfacts
2008, 7, 0721; c) F. W. Patureau, S. de Boer, M. Kuil, J. Meeu-
wissen, P.-A. R. Breuil, M. A. Siegler, A. L. Spek, A. J. Sandee,
B. de Bruin, J. N. H. Reek, J. Am. Chem. Soc. 2009, 131, 6683.
For a review about secondary interactions between chiral li-
gands and substrates, see: d) M. Sawamura, Y. Ito, Chem. Rev.
1992, 92, 857. For selected examples of hydrogen-bonding co-
operative supramolecular ligands, see: e) P.-A. R. Breuil, F. W.
Patureau, J. N. H. Reek, Angew. Chem. Int. Ed. 2009, 48, 3180;
f) B. Breit, W. Seiche, J. Am. Chem. Soc. 2003, 125, 6608; g)
M. Weis, C. Waloch, W. Seiche, B. Breit, J. Am. Chem. Soc.
2006, 128, 4188; h) C. Waloch, J. Wieland, M. Keller, B. Breit,
Angew. Chem. 2007, 119, 3097; Angew. Chem. Int. Ed. 2007,
46, 3037; i) A. C. Laungani, B. Breit, Chem. Commun. 2008,
844; j) M. N. Birkholz, N. V. Dubrovina, H. Jiao, D. Michalik,
J. Holz, R. Paciello, B. Breit, A. Börner, Chem. Eur. J. 2007,
[1] P. W. N. M. Van Leeuwen, in: Homogeneous Catalysis, Under-
standing the Art, Kluwer Academic Publishers, Dordrecht, The
Netherlands, 2004.
[2] For the popular C2-chiral phosphorus ligands (not P-chirog-
enic) in asymmetric hydrogenation and the quadrant theory,
see: a) Handbook of Homogeneous Hydrogenation (Eds.: J. G.
de Vries, C. J. Elsevier), Wiley-VCH, 2007; b) J. M. Brown,
P. L. Evans, Tetrahedron 1988, 44, 4905.
ˇ
13, 5896; k) T. Smejkal, B. Breit, Angew. Chem. 2008, 120,
[3] The applications involving P-chirogenic phosphanes that are
C1-symmetrical are especially scarce. For selected examples,
see: a) W. Chen, W. Mbafor, S. M. Roberts, J. Whittall, J. Am.
Chem. Soc. 2006, 128, 3922; b) R. Aznar, G. Muller, D. Sainz,
M. Font-Bardia, X. Solans, Organometallics 2008, 27, 1967; c)
I. V. Komarov, A. Spannenberg, J. Holz, A. Börner, Chem.
Commun. 2003, 17, 2240; d) R. Romeo, L. A. Wozniak, C.
Chatgilialoglu, Tetrahedron Lett. 2000, 41, 9899; e) S. R. Gil-
bertson, D. G. Genov, A. L. Rheingold, Org. Lett. 2000, 2,
2885; f) J. Albert, J. M. Cadena, S. Delgado, J. Granell, J. Or-
ganomet. Chem. 2000, 603, 235; g) M. Al-Masum, G. Kumaras-
wamy, T. Livinghouse, J. Org. Chem. 2000, 65, 4776; h) T. Wat-
anabe, I. D. Gridnev, T. Imamoto, Chirality 2000, 12, 346; i)
V. V. Dunina, L. G. Kuz’mina, M. Y. Rubina, Y. K. Grishin,
Y. A. Veits, E. I. Kazakova, Tetrahedron: Asymmetry 1999, 10,
4010; Angew. Chem. Int. Ed. 2008, 47, 3946; l) A. Börner, Chi-
rality 2001, 13, 625; m) A. Börner, Eur. J. Inorg. Chem. 2001,
327; n) J. Meeuwissen, M. Kuil, A. M. van der Burg, A. J.
Sandee, J. N. H. Reek, Chem. Eur. J. 2009, 15, 10272; o) L.
ˇ
Diab, T. Smejkal, J. Geier, B. Breit, Angew. Chem. 2009, 121,
8166; Angew. Chem. Int. Ed. 2009, 48, 8022; p) A. C. Laungani,
M. Keller, J. M. Slattery, I. Krossing, B. Breit, Chem. Eur. J.
2009, 15, 10405; q) J. Meeuwissen, A. J. Sandee, B. de Bruin,
M. A. Siegler, A. L. Spek, J. N. H. Reek, Organometallics 2010,
29, 2413; r) J. Meeuwissen, J. N. H. Reek, Nature Chemistry
2010, 2, 615; s) P. Dydio, W. I. Dzik, M. Lutz, B. de Bruin,
J. N. H. Reek, Angew. Chem. Int. Ed. 2011, 50, 396; t) S. Car-
boni, C. Gennari, L. Pignataro, U. Piarulli, Dalton Trans. 2011,
40, 4355.
[7] See the Experimental Section.
1483; j) P.-H. Leung, H. Lang, A. J. P. White, D. J. Williams, [8] a) R. E. Hurd, B. K. John, J. Magn. Reson. 1991, 91, 648; b)
Tetrahedron: Asymmetry 1998, 9, 2961; k) B. Wolfe, T. Liv-
inghouse, J. Am. Chem. Soc. 1998, 120, 5116; l) P.-H. Leung,
S.-K. Loh, K. F. Mok, A. J. P. White, D. J. Williams, Chem.
Commun. 1996, 5, 591; m) V. V. Dunina, E. B. Golovan’, Tetra-
hedron: Asymmetry 1995, 6, 2747; n) Q. Jiang, H. Rüegger,
L. M. Venanzi, J. Organomet. Chem. 1995, 488, 233; o) W. S.
J. Ruiz-Cabello, G. W. Vuister, C. T. W. Moonen, P. van Geld-
eren, J. S. Cohen, P. C. M. van Zijl, J. Magn. Reson. 1992, 100,
282; c) W. Wilker, D. Leibfritz, W. Kerssebaum, W. Bermel,
Magn. Reson. Chem. 1993, 31, 287.
Received: August 1, 2011
Published Online: September 28, 2011
Eur. J. Inorg. Chem. 2012, 496–503
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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