P-stereogenic wide bite angle diphosphine ligands

Article abstract of DOI:10.1016/j.tet.2018.10.070

Two modular synthetic approaches for the preparation of novel wide bite angle diphosphine ligands containing stereogenic P-atoms have been developed, leading to compounds (S,S)-2,2′-bis(methylphenylphosphino)diphenyl ether (L1) and (S,S)-2,2′-bis(ferrocen

Full text of DOI:10.1016/j.tet.2018.10.070

Tetrahedron xxx (xxxx) xxx
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
P-stereogenic wide bite angle diphosphine ligands
Christine F. Czauderna a, Alexandra M.Z. Slawin a, David B. Cordes a,
, c, *
Jarl Ivar van der Vlugt b, Paul C.J. Kamer a
a EaStCHEM, School of Chemistry, University of St Andrews, Purdie Building, North Haugh, St Andrews KY16 9ST United Kingdom
b van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, the Netherlands
c
€
Leibniz-Institut für Katalyse e. V. an der Universitat Rostock, Albert-Einstein-Str. 29a, 18059 Rostock, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Two modular synthetic approaches for the preparation of novel wide bite angle diphosphine ligands
containing stereogenic P-atoms have been developed, leading to compounds (S,S)-2,20-bis(methylphe-
nylphosphino)diphenyl ether (L1) and (S,S)-2,20-bis(ferrocenylphenylphosphino)diphenyl ether (L2) in
very good diastereomeric ratios. Both protocols involve diphenyl ether as backbone and (2RP,4SC,5RC)-
(þ)-3,4-dimethyl-2,5-diphenyl-1,3,2-oxazaphospholidine borane (RP)-5 as initial auxiliary to induce
chirality at phosphorus. The absolute configuration of intermediates (S,S)-9-(BH3)2 and (R,R)-10-(BH3)2 as
well as the ligands (S,S)-L1-BH3 and (S,S)-L2 was determined by X-ray crystallographic analysis.
© 2018 Elsevier Ltd. All rights reserved.
Received 24 September 2018
Received in revised form
22 October 2018
Accepted 25 October 2018
Available online xxx
Keywords:
P-stereogenic ligand
Wide bite angle ligand
Ephedrine
Phosphinite borane
Oxazaphospholidine
1. Introduction
The use of phosphine borane complexes has been explored as
versatile precursors for the synthesis of P-stereogenic phosphines
Chiral diphosphorus ligands are widely used in asymmetric
homogeneous catalysis [1]. Many of these ligands feature stereo-
[9]. This methodology has provided access to P-stereogenic mono-
and diphosphine ligands, but not many triaryl compounds, espe-
cially often desired bulky structures, have been accessible with this
method to date (Scheme 1) despite the abundance of triar-
ylphosphines used as ligands in homogeneous catalysis [10,11].
genic carbon atoms (e.g. Chiraphos, based on
a chiral 2,3-
dimethylpentane backbone), some form of planar chirality (e.g.
Josiphos) or chiral atropisomerism, as present in e.g. binaphthyl-
ꢀ
based scaffolds, with BINAP as
a
well-known example [2].
Juge explored a more versatile method based on an enantiomeri-
Diphosphine ligands bearing P-stereogenic centers have also been
widely explored [3e6]. It is assumed that the close proximity of the
P-stereogenic atom to the catalytically active metal centre offers
high potential for asymmetric induction [7]. Several methods for
the synthesis of the P-stereogenic phosphine ligands have been
developed, including resolution of racemates, synthesis by asym-
metric catalysis and also stereoselective synthesis [6,8]. However,
the synthesis of P-stereogenic phosphines remains challenging,
typically involves multiple steps, generating products that gener-
ally display at least some degree of oxidation-sensitivity and also
because the free P-stereogenic phosphines are potentially prone to
racemisation at phosphorus.
cally pure methyl phosphinite derived from a heterocyclic oxaza-
phospholidine borane, which has enabled the synthesis of a range
of monophosphines and several diphosphine ligands, including
triaryl substituted, in high enantiomeric purity [12e14]. Despite
recent advances [12b,c], The synthesis is often hampered by steric
bulk of the substituents around the phosphorus atom, which makes
the synthesis of bulky P-stereogenic diphosphine ligands still very
challenging.
Diphosphine ligands with a wide bite angle of 102e110ꢀ can
enforce excellent regioselectivity in several catalytic reactions, e.g.
hydroformylation and allylic substitution [15]. Up to now, few
diphosphine ligands are known that combine the concepts of
Pestereogenicity and wide bite angle backbone design [16e18]
€
Recently, a breakthrough has been reported by Borner et al. who
ꢀ
adapted the well-established Juge method for Xantphos analogues
* Corresponding author. EaStCHEM, School of Chemistry, University of St
Andrews, Purdie Building, North Haugh, St Andrews KY16 9ST United Kingdom.
E-mail address: paul.kamer@catalysis.de (P.C.J. Kamer).
[19]. Still, it would be very desirable if more general methods for the
preparation of the class of wide bite angle P-stereogenic
https://doi.org/10.1016/j.tet.2018.10.070
0040-4020/© 2018 Elsevier Ltd. All rights reserved.
Please cite this article as: C.F. Czauderna et al., P-stereogenic wide bite angle diphosphine ligands, Tetrahedron, https://doi.org/10.1016/
j.tet.2018.10.070

2
C.F. Czauderna et al. / Tetrahedron xxx (xxxx) xxx
Scheme 2. Unsuccessful route to P-stereogenic DPEPhos.
Scheme 1. Synthetic route tp alkyl substituted P-stereogenic diphosphine ligands.
diphosphorus ligands would become available. Aiming at access to
bulky bidentate ligands we expanded on the synthetic methodol-
ogy using chlorophosphines as more reactive electrophiles
compared to methylphosphinites. We herein describe two com-
plementary synthetic procedures to realize wide bite angle P-
stereogenic ligands based on diphenyl ether (Fig. 1), thereby
providing chiral analogues of the widely employed diphosphine
ligand DPEPhos [20e22].
Scheme 3. Synthetic route to diphosphinite diborane adduct (R,R)-10-(BH3)2.
2. Results and discussion
2.1. Synthesis of novel P-stereogenic ligands: small substituents
The anticipated synthesis of P-stereogenic DPEPhos analogues
involved the P-stereogenic precursor (2RP,4SC,5RC)-(þ)-3,4-
dimethyl-2,5-diphenyl-1,3,2-oxazaphospholidine borane (RP)-5
[12,23]. Unfortunately, methylphosphinite borane (R)-7, which is
accessible by ring-opening of the oxazaphospholidine borane 5
with 1-lithionaphthalene under retention of configuration to give
(SP)-6 and subsequent acidic methanolysis with inversion of
configuration, [24] proved unreactive toward 2,8-dilithiodiphenyl
ether (Scheme 2), likely because of unfavorable steric interference
of the diphenyl ether with the bulky borane intermediate [14].
Reactions of related dilithium species such as 1,10-dilithioferrocene
resulted in low enantiomeric excess or the formation of mono-
substituted product only [13,25,26]. The low selectivity of these
reactions has been attributed to the second nucleophilic attack,
which is hampered by the increased steric bulk as well as deacti-
vation of the monosubstituted intermediate formed [25]. We
therefore opted to react the diphenyl ether backbone directly with
oxazaphospholidine borane (RP)-5 to generate intermediate (SP,SP)-
9-(BH3)2 and after acidic methanolysis the related diphosphinite
diborane (R,R)-10-(BH3)2 (Scheme 3) [25].
Single crystals of (SP,SP)-9-(BH3)2, obtained by recrystallization
from chloroform, were suitable for single crystal X-ray analysis. The
resulting molecular structure for (SP,SP)-9-(BH3)2, depicted in Fig. 2,
confirmed the retention of configuration during the ring-opening
reaction of the oxazaphospholidine borane (RP)-5 with dilithiodi-
phenyl ether. The two phenyl rings of the diphenyl ether backbone
are not coplanar due to free rotation around the CPh-O bond.
Because both phosphorus atoms are four-coordinated borane ad-
ducts, the intramolecular distance between the two phosphorus
atoms (6.002(5)Å) is larger than for borane-free wide bite angle
diphosphine ligands such as Xantphos (4.080 Å) [21]. The P-B bonds
(1.908(13) and 1.897(12) Å) of both phosphorus groups are almost
indistinguishable and similar to previous reported phosphine bo-
ranes [26,27]. With C-P-X angles (X ¼ B, C, N) between 105.7(5) and
114.3(5) the two phosphorus atoms are close to ideal tetrahedral
geometry.
Fig. 2. Thermal ellipsoid plot of compound (SP,SP)-9-(BH3)2. Displacement ellipsoids
are drawn at the 50% probability level. All hydrogen atoms not bound to boron are
omitted for clarity. Selected bond lengths (Å), angles (ꢀ) and P/P distances (Å): P1-N13
1.656(9), P1-C7 1.813(11), P1-C1 1.823(10), P1-B1 1.908(13), P31-N43 1.654(9), P31-C37
1.815(11), P31-C31 1.841(12), P31-B31 1.897(12); N13-P1-C7 107.5(5), N13-P1-C1
109.0(5), C7-P1-C1 105.7(5), N13-P1-B1 114.3(5), C7-P1-B1 108.6(5), C1-P1-B1 111.4(5),
N43-P31-C37 104.1(5), N43-P31-C31 107.8(5), C37-P31-C31 106.9(5), N43-P31-B31
113.0(5), C37-P31-B31 113.0(6), C31-P31-B31 111.6(6); P1/P31 6.002(5).
The acidic methanolysis of bis(aminophosphine) diborane
(SP,SP)-9-(BH3)2 required three days and subsequently, the BH3-
groups were removed by DABCO at 60 ꢀC. A sharp signal at
d 107.3
was observed in the 31P NMR spectrum and we do not observe the
formation of any meso-compound. Also the 1H NMR spectrum of
(R,R)-10 does not indicate any meso-isomer, hence we propose that
€
no epimerization of the P-centers occurs. Borner and co-workers
recently reported P-stereogenic Xantphos and DPEPhos ana-
logues, wherein removal of BH3 was the key to obtain these com-
pounds [19]. Single crystals of (R,R)-10-(BH3)2 were obtained by
recrystallization from slow diffusion of hexane in a concentrated
solution in ethyl acetate, The molecular structure of compound
(R,R)-10-(BH3)2 (Fig. 3), resulting from an X-ray crystallographic
analysis, confirmed that the acidic methanolysis proceeded via an
SN2-type reaction with inversion of the configuration of (SP,SP)-9-
(BH3)2, similar to the formation of the mono-methylphosphinite
borane (SP)-7. The P-Cbackbone bond lengths (1.813(7) Å and
1.810(7) Å) are similar to the values found for other wide bite angle
Fig. 1. Proposed strategy to novel P-stereogenic wide bite angle diphosphine ligands.
Please cite this article as: C.F. Czauderna et al., P-stereogenic wide bite angle diphosphine ligands, Tetrahedron, https://doi.org/10.1016/
j.tet.2018.10.070

C.F. Czauderna et al. / Tetrahedron xxx (xxxx) xxx
3
The molecular structure (depicted in Fig. 4) confirmed that the
reaction proceeds with inversion of configuration. As for the pre-
vious molecular structures, the observed intramolecular distance
between the two phosphorus atoms (5.672(11)Å) is larger than for
free wide bite angle diphosphine ligands such as Xantphos
(4.080 Å). The P-C bond lengths and P-B bonds are similar to the
previous cases. With C-P-X angles (X ¼ B, C) between 104.04(11)
and 114.94(13)ꢀ, the two phosphorus atoms are only slightly dis-
torted from ideal tetrahedral geometry.
The free ligand (S,S)-L1 was obtained by deprotection of (S,S)-
L1-(BH3)2 with methanol under reflux, whereafter the trimethyl
borate is effectively removed under high vacuum (Scheme 4). This
alternative deprotection method was preferred as work-up of this
sensitive product was more straightforward. Without further pu-
rifications the final ligand (S,S)-L1 was obtained in quantitative
yield as a sticky, oxygen-sensitive solid with 65% diastereomeric
excess (S:S/R:S ¼ 87:12). Given the 12% of meso-compound, which
was already present, racemisation is negligible, if occurring at all.
Fig. 3. Thermal ellipsoid plot of compound (R,R)-10-(BH3)2. Displacement ellipsoids
are drawn at the 50% probability level. All hydrogen atoms not bound to boron are
omitted for clarity. Selected bond lengths (Å), angles (ꢀ)and P/P distances (Å): P1-O13
1.604(5), P1-C1 1.813(7), P1-C7 1.823(7), P1-B1 1.892(7), P21-O33 1.599(5), P21-C21
1.810(7), P21-C27 1.819(7), P21-B21 1.915(8); O13-P1-C1 97.5(3), O13-P1-C7 106.3(3),
C1-P1-C7 106.1(3), O13-P1-B1 112.6(3), C1-P1-B1 117.7(3), C7-P1-B1 114.8(3), O33-P21-
C21 110.4(3), O33-P21-C27 107.6(3), C21-P21-C27 105.9(3), O33-P21-B21 108.0(3), C21-
P21-B21 112.2(4), C27-P21-B21 112.7(4); P1/P21 5.796(3).
2.2. Synthesis of novel P-stereogenic ligands: large substituents
In literature, chlorophosphines are rarely applied in P-stereo-
genic chemistry because of the limited number of methods avail-
able
to
synthesize
enantioenriched
P-stereogenic
chlorophosphines and their tendency to racemize [29,30]. Chlor-
ophosphine boranes have been synthesized from aminophosphine
borane (SP)-6 in optically enriched form, although the resulting
chlorophosphine boranes are generally sensitize to racemisation,
especially in case of small P-atom substituents [31].
Upon replacing the 1-naphthyl substituent in these phosphine
species by ferrocene, we discovered that the resulting compound
(R)-12 is completely stable towards racemisation. Treatment of
oxazaphospholidine borane (RP)-5 with lithioferrocene, available
via lithiation of 1-bromo-ferrocene, afforded the aminophosphine
borane (SP)-11 in good yield (Scheme 5). Just as for the previously
synthesized aminophosphine boranes (SP)-6 (featuring a naphthyl
group), ring opening of the oxazaphospholidine borane (RP)-5
proceeded with retention of the configuration at phosphorus. Un-
fortunately, the subsequent reaction of dilithiodiphenyl ether with
ligands such as Xantphos [20]. The intramolecular distance be-
tween the two phosphorus atoms (5.796(3) Å) is larger than in
Xantphos (4.080 Å), which is likely due to the additional BH3-co-
ordination. The P-B bonds (1.892(7) and 1.915(8) Å) of both phos-
phorus groups are almost indistinguishable and similar to previous
reported phosphine boranes [27]. The tetrahedral geometry is
distorted around both phosphorus centers, judging from e.g. the B-
P-C angles.
Transformation of bismethylphosphinite borane (R,R)-10-(BH3)2
into the desired P-stereogenic diphosphine ligands was dependent
on the nature of the nucleophile. Reaction with either phenyl-
lithium or biphenyllithium did not lead to successful introduction
of the aryl substituent despite screening several reaction condi-
tions. Furthermore, only small alkyl substituents (Me, nBu) were
smoothly introduced in the bis-methylphosphinite borane (R,R)-10-
(BH3)2 at ꢁ78 ꢀC, while tert-butyl and sec-butyl fragments were
inaccessible. Similar limitations for the construction of P-stereo-
genic phosphinoborane compounds have previously been reported
for related bulky diarylmethylphosphinite boranes as starting ma-
terial [28].
Reaction of bis-methyl phosphinite borane (R,R)-10-(BH3)2 and
methyllithium (Scheme 4) led to a diastereomeric ratio of (S,S)-L1-
(BH3)2/(R,S)-L1-(BH3)2 (87:12) as determined by 1H and 31P NMR
spectroscopy, which was verified by comparing the spectra with an
independently synthetized (rac,meso)-mixture of L1-(BH3)2 (vide
infra). As the amount of meso-compound was only 12% it is
reasonable to assume that (R,R)-L1-(BH3)2 has only be formed in
small amounts (<5%). Recrystallization of (S,S)-L1-(BH3)2 by slow
diffusion of diethyl ether in a concentrated CH2Cl2 solution resulted
in single crystals suitable for X-ray crystallography.
Fig. 4. Thermal ellipsoid plot of compound (S,S)-L1-(BH3)2 Displacement ellipsoids are
drawn at the 50% probability level. All hydrogen atoms not bound to boron are omitted
for clarity. Selected bond lengths (Å), angles (ꢀ)and P/P distances (Å): P1-C13 1.805(3),
P1-C7 1.812(2), P1-C11.831(2), P1-B11.919(3), P21-C27 1.810(2), P21-C211.811(2), P21-
C33 1.811(2), P21-B21 1.920(3); C13-P1-C7 105.39(11), C13-P1-C1 107.21(11), C7-P1-C1
104.04(11), C13-P1-B1 114.94(13), C7-P1-B1 112.59(12), C1-P1-B1 111.86(11), C27-P21-
C21 105.80(10), C27-P21-C33 106.70(11), C21-P21-C33 107.42(11), C27-P21-B21
113.25(12), C21-P21-B21 113.10(12), C33-P21-B21 110.17(12); P1/P21 5.6472(11).
Scheme 4. Nucleophilic substitution of methyl phosphinite (SP,SP)-10-(BH3) with MeLi
and deprotection of the phosphine-borane with MeOH to generate (S,S)-L1.
Please cite this article as: C.F. Czauderna et al., P-stereogenic wide bite angle diphosphine ligands, Tetrahedron, https://doi.org/10.1016/
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4
C.F. Czauderna et al. / Tetrahedron xxx (xxxx) xxx
Fig. 5. Thermal ellipsoid plot of compound (S,S)-L2. Displacement ellipsoids are drawn
Scheme 5. Synthetic procedure of (S,S)-L2 via phenylphosphinite borane (S)-13.
at the 50% probability level. All hydrogen atoms are omitted for clarity. Selected bond
lengths (Å), angles (ꢀ)and P/P distances (Å): P1-C13 1.819(5), P1-C1 1.835(5), P1-C7
1.844(5), P31-C43 1.816(5), P31-C37 1.837(5), P31-C31 1.839(5); C13-P1-C1 100.9(2),
C13-P1-C7 100.7(2), C1-P1-C7 101.3(2), C43-P31-C37 100.1(2), C43-P31-C31 100.3(2),
C37-P31-C31 102.6(2); P1/P31 5.5458(19).
chlorophosphine borane (R)-12 was unsuccessful under various
temperatures in different solvents and thus exchanging the leaving
group from methoxy (in species (R,R)-10-(BH3)2) to a chloride did
not enhance the overall reactivity of the P-stereogenic unit. Direct
substitution of the ephedrine unit in aminophosphine borane (SP)-
11 with sodium phenolate was also not successful.
12 with dilithiodiphenyl ether were unsuccessful. This problem was
overcome by reaction of the (2RP,4SC,5RC)-oxazaphospholidine
borane (SP)-5, which is more reactive toward nucleophilic substi-
tution, with the dilithiodiphenyl ether. This reaction was followed
up by acidic methanolysis and reaction with methyllithium led to
the desired ligand L1. During the reaction sequence the final ligand
L1 was only obtained with a diastereomeric ratio (dr) of 87:12. As
an alternative protocol, we explored the use of phenylphosphinite
(S)-13 as an intermediate, via the acidolysis of (2RP,4SC,5RC)-oxa-
zaphospholidine borane (SP)-5, reaction with sodium phenolate
and removal of the BH3-group. This building block was successfully
coupled to the wide bite angle backbone diphenyl ether. Unfortu-
nately, the final ligand L2 slowly racemized during purification and
as a shelved solid. However, the phenyl phosphinite building block
(S)-13, which proved to be stable towards racemisation, provides
facile access to a previously undeveloped class of P-stereogenic
diphosphine ligands as well as bulky monophosphine ligands.
Gratifyingly, this problem could be circumvented by reacting
chlorophosphine borane (R)-12 with sodium phenolate (Scheme 5).
The 31P NMR spectrum of the reaction mixture showed full con-
version after two hours and the product (S)-13-(BH3) was easily
purified by flash chromatography. The enantiopurity of (S)-13-
(BH3) was established to be greater than 72% by HPLC. The BH3
group is easily removed by heating (S)-13-(BH3) in toluene in the
presence of DABCO at 60 ꢀC overnight with retention of configu-
ration and with high ee (>72%). The free phenylphosphinite com-
pound (S)-13 proved to be relatively stable, e.g. it withstands
filtration over silica under Ar atmosphere. Treatment of phenyl
phosphinite (S)-13 with dilithiodiphenyl ether-TMEDA at ꢁ78 ꢀC
afforded ligand L2 as a mixture of three stereoisomers (rac vs. meso)
in a ratio of 84:16, as established by 31P NMR spectroscopy, which
corresponds to a diastereomeric purity of 68% de. We thus estab-
lished the coupling of an unprotected P-stereogenic compound
with a dilithiated co-reagent to afford selective double substitution.
4. Experimental section
€
The group of Borner recently and independently reported the same
approach to furnish xanthene and diphenyl ether-based P-stereo-
All reactions were carried out using standard Schlenk tech-
niques under an atmosphere of purified argon. Toluene was
distilled from sodium, THF and Et2O from Na/benzophenone, hex-
ane from Na/benzophenone/triglyme, methanol and ethanol from
Mg and DCM from CaH2 under argon atmosphere. NMP, stored over
molecular sieves, was purchased from Fluka. Chemicals were pur-
chased from Acros Organics, Sigma-Aldrich and Alfa Aesar. Dieth-
ylamine and triethylamine were distilled from K2CO3. ClPPh2 and
PCl3 were distilled under argon atmosphere before use. Compounds
bis(diethylamino)phenylphosphine [32], (RP)-5 [12], dilithiodi-
phenyl ether [33], (2RP,4SC,5RC)-(ꢁ)-N-methyl-N-(1-hydroxy)-1-
phenyl)prop-2-yl-P-(1-naphthyl)-P-(phenyl)-phosphinamide
genic (aryl)(aryl0)diphosphines [19].
Fractional crystallization by vapor phase diffusion of diethyl
ether into a CH2Cl2 solution led to elucidation of the molecular
structure of (S,S)-L2 (Fig. 5). As expected the two phenyl rings of the
backbone are not co-planar. The P-C bond lengths (between
1.819(5) Å and 1.844(5) Å) are in the same range as the related
diphosphine ligand L1. The intramolecular distance of the two
phosphorus atoms (5.5458(19) Å) is larger than for other wide bite
angle diphosphine ligands, but smaller than in the above described
(S,S)-L1-(BH3)2. The sum of the C-P-C angles (302.9ꢀ and 303.0ꢀ) is
similar to previous reported P-stereogenic diphosphine ligands
[13]. Unfortunately, the final ligand (S,S)-L2 slowly racemized
during storage.
borane
((SP)-6)
[13],
(S)-(þ)-methyl-(1-naphthyl)-phenyl-
phosphinite borane ((R)-7) [13], were synthesized according to
literature procedures. Washing solutions (water, brine) were
degassed by three freeze-pump-thaw cycles and all precursors
were dried azeotropically. Silica and aluminium oxide were
degassed under vacuum before use. Column chromatography was
carried out under argon atmosphere with flame dried glassware.
TLC analysis was executed using silica F254 TLC plates from VWR.
Silica gel 60 (0.063e0.2 mm; Fluka) was used for flash chroma-
tography. Melting points were determined on a Gallenkamp MF-
370 melting point apparatus in open capillaries. 1H, 13C, and 31P
3. Conclusions
Two modular synthetic approaches to afford the novel wide bite
angle diphosphine ligands L1 and L2 containing stereogenic P-
atoms have been established, starting from the chiral heterocyclic
precursor (2RP,4SC,5RC)-oxazaphospholidine borane (SP)-5, which is
derived from ephedrine. Synthetic pathways involving coupling of
methylphosphinite borane (R)-7 or chlorophosphinite borane (R)-
Please cite this article as: C.F. Czauderna et al., P-stereogenic wide bite angle diphosphine ligands, Tetrahedron, https://doi.org/10.1016/
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C.F. Czauderna et al. / Tetrahedron xxx (xxxx) xxx
5
spectra were measured on
a
Bruker Advance II 400 (1H:
CD2Cl2, 296 K)
d
(ppm) 104.2 (P-BH3). Minor product: 1H NMR
3
400.13 MHz; 13C: 100.6 MHz; 31P: 162.0 MHz) or a Bruker Advance
(400 MHz, CDCl3, 296 K)
d
(ppm) 7.7.75 (ddd, 2H, JHH ¼ 10.9 Hz,
300 NMR spectrometer (1H: 300.13 MHz; 13C: 75.5 MHz; 31P:
4JHH ¼ 1.3 Hz, JPH ¼ 6.7 Hz), 7.48e7.15 (m, 20H; PheH), 6.27 (ddd,
3
3
4
3
121.5 MHz). Chemical shifts (
d
) are given in parts per million (ppm).
2H, JHH ¼ 8.0 Hz, JHH ¼ 1.2 Hz, JPH ¼ 3.8 Hz), 3.68 (d, 6H,
Broad band decoupling was used for 13C and 31P NMR spectra. 1H
3JPH ¼ 12.2 Hz, OCH3), 1.3-0.3 (m, 6H, BH3). 31P NMR (162 MHz,
and 13C spectra were measured relative to the signal of the solvent
CD2Cl2, 296 K)
d (ppm) 108.0 (broad, P-BH3).
(CDCl3: 1H: d, 7.27 ppm, 13C: d, 77.2 ppm) in which the sample was
analysed and are reported relative to Me4Si. 31P NMR spectra were
referenced externally respectively to 85% H3PO4. CDCl3 was
distilled over CaH2 and stored over K2CO3 under argon. Other
deuterated solvents were degassed by three freeze-pump-thaw
cycles. Optical rotations were measured in a Perkin-Elmer 341
polarimeter which is regulated by a thermostat at T ¼ 20 ꢀC with
l ¼ 10 cm in air at 589 nm (sodium D line) and concentrations (c)
are reported in g/100 mL. (Note: Highly sensitive compounds are
not measured). Mass spectra were collected using a Micromass GC
mass spectrometer or a Thermo Scientific DSQ II Single Quadrupole
GC/MS spectrometer. FTIR measurements were carried out on a
Nicolet 6700 spectrometer (Thermo Fisher Scientific) in trans-
mission mode with a CsI pellet in a N2-filled glovebox.
4.3. (R,R)-10
A solution of DABCO (11.27 mg, 0.1 mmol, azeotropically dried)
was added to a solution of (R,R)-10-(BH3)2 (9.48 mg, 0.02 mmol) in
toluene (5 mL) at r.t. The reaction mixture was heated for 20 h at
60 ꢀC. The volatiles were removed in vacuo and the crude reaction
mixture was analysed by 1H NMR and 31P NMR spectroscopy
without further purification. Yield: 0.240 g (0.50.5 mmol, 51%). 1H
NMR (400 MHz, CDCl3, 296 K)
d (ppm) 7.48-7.43 (m, 6H; PheH),
7.26-7.22 (m, 20H; PheH), 7.11-7.08 (m, 6H; PheH), 3.65 (d, 6H,
3JPH ¼ 14.0 Hz, OCH3).31P NMR (162 MHz, CD2Cl2, 296 K)
d (ppm)
107.3.
4.1. (SP,SP)-9-(BH3)2
4.4. (S,S)-L1-(BH3)2
A solution of dilithiodiphenyl ether TMEDA-adduct (4.707 g,
11.35 mmol) in a mixture of diethyl ether (25 mL) and tetrahydro-
furan (25 mL) was added slowly to a solution of (RP)-5 (7.14 g,
24.9 mmol) in tetrahydrofuran (100 mL) at ꢁ78 ꢀC. The reaction
was allowed to warm slowly to r.t. overnight. The solution was
quenched with water and the solvent was evaporated to dryness
under high vacuum. The white precipitate was extracted with
dichloromethane and purified by a short column (SiO2, eluent:
toluene:ethyl acetate 9:1). (SP,SP)-9-(BH3)2 was obtained as white
solid (yield: 3.78 g, 5.10 mmol, 45%). 1H NMR (400 MHz, CD2Cl2,
MeLi (2.3 mL, 3.4 mmol, 1.5 M in diethylether, freshly titrated)
was added to a solution of (R,R)-10-(BH3)2 (744 mg, 1.55 mmol) in
tetrahydrofuran (1 M) at ꢁ100 ꢀC. The reaction mixture was slowly
warmed up to r.t. overnight. The reaction mixture was quenched
with water at room temperature. The product was extracted with
dichloromethane and purified by column chromatography (SiO2,
eluent: CH2Cl2:hexane 1:1) to give (S,S)-L1-(BH3)2 as white solid
20
(yield: 0.240 g, 0.54 mmol, 35%). [
a
]
(c ¼ 0.201, CHCl3) ¼ þ3.4ꢀ.
D
m.p. 159 ꢀC. MS LC-TOF: m/z calculated for [C26H30B2OP2þNa]þ:
m ¼ 465.1856 (MþNa)þ, obs.: 465.1859 (MþNa)þ. Major product:
296 K)
d
(ppm) 7.75-7.67 (m, 2H, PhH), 7.40e7.7.05 (m, 20H, PhH),
1H NMR (400 MHz, CD2Cl2, 296 K):
d (ppm) 7.83-7.78 (m, 2H, PhH),
6.69-6.57 (m, 6H, PhH), 4.7 (d, 2H, 3JHH ¼ 6.3 Hz), 4.18-4.09 (m, 2H),
7.35-7.29 (m, 6H), 7.48-7.28 (m, 12H), 7.22-7.12 (m, 4H), 6.04-6.00
3
3
3
3.12 (s, 2H, OH), 1.91 (d, 6H, JPH ¼ 8.0 Hz), 1.15, (d, 6H,
(m, 2H), 6.51 (broad dd, 1H, JHH ¼ 8.1 Hz, JHP ¼ 2.98 Hz), 1.65 (d,
3JHH ¼ 6.7 Hz), 1.8-0.2 (m, 6H; BH3). 13C NMR (100 MHz, CD2Cl2,
1H, JPH ¼ 10.2 Hz), 1.4-0.3 (broad q, BH3). 13C NMR (100 MHz,
2
296 K)
d
(ppm) 159.9 (d, JPC ¼ 2.3 Hz, Ph), 143.2, 135.6-121.9 (m, Ph),
CD2Cl2, 296 K):
d
(ppm) 160.0, 136.2 (d, JPC ¼ 11.8 Hz), 134.8 (d,
78.7 (d, JPC ¼ 6.9 Hz; CH), 58.3 (d, JPC ¼ 10.8 Hz, CH), 30.3 (d,
JPC ¼ 11.0 Hz), 143.7, 134.5, 132.6 (d, JPC ¼ 10.0 Hz), 131.9, 131.6 (d,
JPC ¼ 2.1 Hz), 131.4, 129.6 (d, 1JPC ¼ 10.2 Hz), 125.0 (d, 1JPC ¼ 10.4 Hz),
122.5 (d, JPC ¼ 23.4 Hz),121.4 (d, JPC ¼ 4.2 Hz),11.8 (d, 1JPC ¼ 40.9 Hz).
JPC ¼ 4.1 Hz; CH3), 13.7 (CH3). 31P NMR (162 MHz, CD2Cl2, 296 K)
d
(ppm) 69.4 (broad s, P-BH3). [
a
þ
]
D (c ¼ 0.261, CHCl3) ¼ þ56.3ꢀ. m.p.
91e95 ꢀC. Mass (FT-MS
p
NSI) m/z calculated for
31P NMR{1H} (161 MHz, CD2Cl2, 296 K):
d (ppm) 7.4 (broad d,
[C44H52B2N2O3P2þH]þ 739.3765 (MþH)þ, obs.: 739.3785 (MþH)þ
and [C44H52B2N2O3P2ꢁВH2]ꢁ 727.3390 [MꢁВH-2]þ, obs.: 727.3387
[MꢁВH2] ꢁ (mixture of [MþH]þ and [MꢁВHꢁ2 ]þ was observed).
1JPB ¼ 64.1 Hz, P-BH3). Minor product: 1H NMR (400 MHz, CD2Cl2,
296 K):
d (ppm) 7.69-7.64 (m, 4H), 7.35-7.29 (m, 6H), 7.48-7.28 (m,
12H), 7.22-7.12 (m, 2H), 6.68-6.65 (m, 2H),1.66 (d,1H, 2JPH ¼ 4.1 Hz),
1.4-0.3 (broad q, BH3). 31P NMR{1H}(161 MHz, CD2Cl2, 296 K):
4.2. (R,R)-10-(BH3)2
d
(ppm) 7.4 (broad d, 1JPB ¼ 64.1 Hz, P-BH3).
(S,S)-L1. (S,S)-L1-(BH3)2 (100 mg, 0.23 mmol) was suspended in
Methanol (80 mL, degassed, dry) and concentrated H2SO4
(0.205 g, 2.09 mmol) were added to a solution of (SP,SP)-9-(BH3)2
(0.780 g, 0.99 mmol) in THF (20 mL) whilst cooling the mixture in
an ice-bath. After slowly warming to room temperature, the reac-
tion mixture was followed by 31P NMR spectroscopy. After
completion, the solvent was evaporated. The product was subjected
to column chromatography (SiO2, eluent: hexane:ethyl acetate 9:1)
to give (R,R)-10-(BH3)2 as white solid (yield: 0.240 g, 0.505 mmol,
methanol and heated at 80 ꢀC overnight. Full deprotection was
observed by 31P NMR. All volatiles were removed in vacuo. No
further purification was necessary and (S,S)-L1 was obtained as
white sticky solid (yield: 84 mg, 0.202 mmol, 90%). MS LC-TOF: m/z
calculated for [C26H24OP2þNa]þ: m ¼ 437.1200 (MþNa)þ, obs.:
437.1192 (MþNa)þ. Major product: 1H NMR (400 MHz, CD2Cl2,
296 K):
d (ppm) 7.43-7.41 (m, 4H), 7.31-7.27 (m, 6H), 7.15-7.11 (m,
3
4H), 7.02-6.98 (m, 2H), 6.44 (broad dd, 1H, JHH ¼ 8.1 Hz,
51%). [
a
]
20 (c ¼ 0.252, CHCl3) ¼ ꢁ32ꢀ. m.p. 118e120 ꢀC. Mass (FT-MS
2JPH ¼ 2.98 Hz), 1.58 (d, 1H, JPH ¼ 4.1 Hz). 13C NMR (100 MHz,
2
D
ESIþ) m/z calculated for [C26H30B2O3P2þNa]þ: m ¼ 497.1754
CD2Cl2, 296 K)
d
(ppm) 159.7 (d, JPC ¼ 14.6 Hz), 139.9.7 (d,
(MþNa)þ, obs.: 497.1760 (MþNa)þ. Major product: 1H NMR
JPC ¼ 12.3 Hz), 133.4 (d, JPC ¼ 19.8 Hz), 132.6 (d, JPC ¼ 3.6 Hz), 130.6,
(400 MHz, CDCl3, 296 K)
d (ppm) 7.75-7.67 (m, 2H; PheH),
129.2, 129.1 (d, JPC ¼ 7 Hz),124.3, 118.7, 11.8 (d, JPC ¼ 12.7 Hz). 31P
3
7.48e7.15 (m, 20H; PheH), 6.07 (ddd, 2H, JHH ¼ 7.8 Hz,
NMR{1H} (161 MHz, CD2Cl2, 296 K):
d
(ppm) ꢁ36.0. Minor product:
3
3
4JHH ¼ 1.6 Hz, JPH ¼ 3.8 Hz), 3.69 (d, 6H, JPH ¼ 12.3 Hz, OCH3), 1.3-
1H NMR (400 MHz, CD2Cl2, 296 K):
d (ppm) 7.43-7.41 (m, 4H), 7.31-
0.3 (m, 6H, BH3). 13C NMR (100 MHz, CD2Cl2, 296 K)
d
(ppm) 159.9
7.27 (m, 6H), 7.15-7.11 (m, 4H), 7.02-6.98 (m, 2H), 6.50 (broad dd,
(d, JPC ¼ 2.3 Hz; Ph-C), 143.2, 135.6-121.9 (m, Ph-C), 78.7 (d,
1H, 3JHH ¼ 8.1 Hz, 2JPH ¼ 2.98 Hz), 1.52 (d, 1H, 2JPH ¼ 4.1 Hz). 31P NMR
JPC ¼ 6.9 Hz; CH-C), 48.3 (d, JPC ¼ 8.8 Hz; CH-C). 31P NMR (162 MHz,
{1H} (161 MHz, CDCl3, 296 K):
d
(ppm) ꢁ36.4.
Please cite this article as: C.F. Czauderna et al., P-stereogenic wide bite angle diphosphine ligands, Tetrahedron, https://doi.org/10.1016/
j.tet.2018.10.070

6
C.F. Czauderna et al. / Tetrahedron xxx (xxxx) xxx
4.5. (SP)-11
found to be >72% (column: AD-H, eluent: hexane (95%), IPA (5%),
flow:
0.5 mL minꢁ1
,
(S)-13-(BH3) ¼ 16.8 min,
(R)-13-
(ppm) 8.03-
tert-Butyllithium (1.6 M in Et2O; 13.3 mL, 21.25 mmol) was
(BH3) ¼ 21.5 min). 1H NMR (500 MHz, CD2Cl2, 296 K)
d
added slowly to a solution of bromoferrocene (2.82 g, 10.62 mmol)
in diethyl ether (60 mL) at ꢁ78 ꢀC and the solution was stirred for
30 min. The solution was warmed to 0 ꢀC and stirred for an addi-
tional 15 min to generate FcLi. Completion of the lithiation was
checked by quenching a sample with H2O and monitoring it by GC/
MS. A solution of (R)-5 (3.18 g, 11.16 mmol) in THF (70 mL) was
cooled to ꢁ78 ꢀC, and the FcLi solution was added via cannula. The
solution was allowed to warm to 10 ꢀC and stirred overnight. The
reaction mixture was quenched with water (3 mL) and all volatiles
were removed in vacuo. The crude product was suspended in
CH2Cl2. The organic layer washed with water and brine, dried with
MgSO4, filtered, and concentrated in vacuo. The crude residue was
purified via gradient column chromatography (SiO2,eluent: 100%
toluene, gradient increased to toluene:ethyl acetate 9:1) to give
diastereomerically pure (SP)-11 as orange powder (yield: 4.57 g,
7.99 (m, 2H, PhH), 7.62-7.53 (m, 3H, PhH), 7.23 (t, 2H, 3JHH ¼ 7.3 Hz),
7.09 (t,1H, 3JHH ¼ 7.4 Hz), 6.99 (d, 2H, 3JHH ¼ 7.8 Hz), 4.7 (broad s,1H,
cp), 4.55 (broad s, 1H, cp), 4.51 (broad s, 1H, cp), 4.39 (broad s, 1H,
cp), 4.13 (broad s, 5H, cp), 1.8-0.8 (broad m, 3H; BH3). 13C NMR
(126 MHz, CD2Cl2, 296 K)
d
(ppm) 153.3(d, JPC ¼ 5.9 Hz), 133.1, 133.0
(d, JPC ¼ 2.1 Hz), 132.6, 132.0 (d, JPC ¼ 11.3 Hz), 130.0, 129.3 (d,
JPC ¼ 10.4 Hz), 125.2, 122.1 (d, JPC ¼ 3.9 Hz), 73.4 (d, JPC ¼ 8.2 Hz, CH),
72.2 (d, JPC ¼ 13.3 Hz, Cp), 73.0 (d, JPC ¼ 8.7 Hz, Cp), 72.5 (d,
JPC ¼ 10.3 Hz), 71.8 (d, JPC ¼ 77 Hz, Cp), 70.9 (Cp). 31P NMR{1H}
(162 MHz, CD2Cl2, 296 K)
d
(ppm) 110.3 (q, JPB ¼ 71.5 Hz, P-BH3).
20
m.p. 38e41 ꢀC. [
a
]
D
(c ¼ 0.258, CHCl3) ¼ ꢁ84.2ꢀ. Mass (TOF-MS
ESIþ) m/z calculated for [C22H22BFeOPþNa]þ423.0748 [MþNa]þ,
obs.: 423.0753 [MþNa]þ.
4.8. (S)-13
9.7 mmol, 92%). 1H NMR (500 Mhz, CD2Cl2, 296 K)
d (ppm) 7.41-7.28
(m, 10H, PhH), 4.83-4.81 (m, 1H, CH), 4.54 (broad s, 1H, cp), 4.50
(broad s,1H, cp), 4.46 (broad s,1H, cp), 4.25 (s, 5H, cp), 4.20 (broad s,
1H, cp), 4.18-4.11 (m, 1H, CH), 2.31 (d, 3H, 3JHH ¼ 8.2 Hz), 1.19 (d, 3H,
3JHH ¼ 6.8 Hz),1.8-0.8 (broad m, 3H; BH3). 13C NMR (126 MHz,
A solution of DABCO (1.68 g, 14.95 mmol) in toluene (40 mL) was
added to a solution of (S)-13-(BH3) (1.50 g, 3.73 mmol, azeotropi-
cally dried with toluene) in diethylether (100 mL). The reaction
mixture was heated for 20 h at 60 ꢀC. After cooling to r.t., toluene
was removed in vacuo. Purification by filtration over silica (SiO2;
eluent: ethyl acetate) resulted in a light orange solid that was used
without further purification (yield: 1.24 g, 3.6 mmol, 96%). 1H NMR
CD2Cl2, 296 K)
d
(ppm) 143.3, 133.7, 133.1, 131.80 (d, JPC ¼ 10.1 Hz),
130.8 (d, JPC ¼ 1.9 Hz), 128.7, 128.5 (d, JPC ¼ 10.2 Hz), 128.0, 127.1,
79.1 (d, JPC ¼ 5.7 Hz, Cp), 72.9 (d, JPC ¼ 7.3 Hz, Cp), 72.5, 72.4 (d,
JPC ¼ 12.8 Hz, Cp), 71.9, 71.6 (d, JPC ¼ 7.8 Hz), 71.5 (d, JPC ¼ 6.7 Hz,
Cp), 58.2 (d, JPC ¼ 9.3 Hz), 30.7 (d, JPC ¼ 3.0 Hz), 13.3. 31P NMR{1H}
(500 MHz, CD2Cl2, 296 K) d (ppm) 7.77-7.74 (m, 2H, PhH), 7.46e8.42
3
3
(m, 3H, PhH), 7.26 (t, 2H, JHH ¼ 7.7 Hz), 7.10 (d, 2H, JHH ¼ 7.7 Hz),
3
(162 MHz, CD2Cl2, 296 K)
d
(ppm) 69.5 (d, JPB ¼ 82.0 Hz, P-BH3). m.p.
6.98 (t, 1H, JHH ¼ 7.3 Hz), 4.53 (broad s, 1H, cp), 4.45 (broad s, 1H,
20
84e88 ꢀC. [
a
]
D
(c ¼ 0.252, CHCl3) ¼ ꢁ106.9ꢀ. Mass (TOF-MS ESIþ)
cp), 4.36 (broad s, 1H, cp), 4.41 (s, 5H, cp), 4.01 (broad s, 1H, cp). 13
C
m/z calculated for [C26H31BFeNOPþNa]þ494.1483 [MþNa]þ, obs.:
NMR (126 MHz, CD2Cl2, 296 K)
d
(ppm) 156.63(d, JPC ¼ 9.2 Hz),139.8
494.1480 [MþNa]þ.
(d, JPC ¼ 17.2 Hz), 129.7 (d, JPC ¼ 23.1 Hz), 129.0, 128.6, 127.4 (d,
JPC ¼ 7.6 Hz), 121.3, 117.8 (d, JPC ¼ 11.2 Hz), 78.1 (d, JPC ¼ 12.7 Hz, Cp),
71.6 (d, JPC ¼ 22.6 Hz, Cp), 70.9 (d, JPC ¼ 5.6 Hz, Cp), 70.4, 70.3 (d,
JPC ¼ 15.5 Hz, Cp), 68.2 (Cp). 31P NMR{1H} (162 MHz, CD2Cl2, 296 K)
4.6. (R)-12
A 2M HCl solution in Et2O (30.4 mL, 60.74 mmol) was added
under stirring at r.t. to a solution of aminophosphine borane (SP)-11
(4.77 g, 10.1262 mmol) in toluene (155 mL), After 1.5 h, the reaction
mixture turned cloudy and full conversion of the starting material
was observed by 31P NMR spectroscopy. The reaction mixture was
filtered (Schlenk filter; glass frit P4) and the excess of HCl was
removed by several vacuum argon cycles. The crude product (R)-12
d
(ppm) 107.02 (s, P-BH3).
4.9. L2
A suspension of dilithiodiphenyl ether (515 mg, 1.25 mmol) in
Et2O (30 mL) was cooled to ꢁ78 ꢀC before THF (15 mL) was added.
The suspension was slowly added via cannula to a solution of (S)-13
(1.01 g, 2.6 mmol) in THF (85 mL) at ꢁ78 ꢀC. After 1 h at ꢁ78 ꢀC, the
reaction mixture was allowed to warm to 12 ꢀC and stirred for an
additional 14 h at this temperature. The reaction mixture was
quenched with methanol (3e4 mL) and all volatiles were removed
in vacuo. The crude product was suspended in THF and the organic
layer washed with water and brine, dried with MgSO4, filtered, and
concentrated in vacuo. The crude residue was purified by column
chromatography (SiO2, eluent: hexane:CH2Cl2 1:1, gradient
increased to hexane:CH2Cl2 1:2) to give L2 as orange precipitate
(yield: 3.33 g, 8.32 mmol, 82%). Recrystallization by slow diffusion
was used in solution without evaporation of the solvent. 31P NMR
1
(162 MHz, CD2Cl2, 296 K)
BH3).
d
(ppm) 94.9 (broad d, JPB ¼ 45.5 Hz, P-
4.7. (S)-13-(BH3)
A solution of phenol (70.87 g, 6.67 mmol) in THF (15 mL) was
slowly added to a suspension of NaH (1.7 g, 70.87 mmol) in THF
(20 mL) at 0 ꢀC over 20 min. After 20 min at 0 ꢀC, the reaction
mixture was allowed to warm to r.t., where after it was stirred for
an additional 2 h to generate sodium phenolate. The solution of
sodium phenolate (max. 70.87 mml) in THF (35 mL) was slowly
added via cannula to a solution of chlorophosphine borane (R)-12
(max. 3.47 g, 10.12 mmol) in toluene (155 mL) at ꢁ78 ꢀC and the
solution was stirred for 30 min at ꢁ78 ꢀC. The solution was warmed
to r.t. and stirred overnight. The reaction mixture was quenched
with water (3e4 mL) and all volatiles were removed in vacuo. The
crude product was suspended in CH2Cl2, the organic layer washed
with water and brine, dried with MgSO4, filtered, and concentrated
in vacuo. The crude residue was purified by column chromatog-
raphy (SiO2,eluent: 100% toluene) to give (S)-13-(BH3) as orange
solid (yield: 3.33 g, 8,32 mmol, 82%). The enantiomeric excess of
(S)-13-(BH3) was determined using chiral HPLC measurements and
of Et2O into a solution of L2 in CH2Cl2 yielded single crystals that
20
were suitable for X-ray crystallographic analysis. [
a
]
(c ¼ 0.252,
D
CHCl3) ¼ 163.2ꢀ. m.p. 179 ꢀC (decomposition). Mass (TOF-MS ESIþ)
m/z calculated for [C44H36Fe2OP2þNa]þ777.0838 [MþNa]þ, obs.:
777.0831 [MþNa]þ. Major: 1H NMR (400 MHz, CD2Cl2, 296 K)
d
(ppm) 7.40-7.23 (m, 10H, PhH), 7.06-6.9 (m, 6H), 6.22 (dd, 2H,
3JHH ¼ 7.6 Hz, JPH ¼ 3.5 Hz, PhH), 4.42-4.40 (m, 2H, Cp), 4.36-4.33
3
(m, 4H, Cp), 4.09 (s, 5H, Cp), 3.89-3.88 (m, 5H, Cp). 13C NMR
(100 MHz, CD2Cl2, 296 K)
d
(ppm) 159.9 (d, JPC ¼ 18.3 Hz), 138.7 (d,
JPC ¼ 9.7 Hz), 135.12, 134.9, 134.6 (d, JPC ¼ 10.65 Hz), 132.4 (d,
JPC ¼ 16.3 Hz),130.6, 129.2, 129.7-128.7, (m), 123.9, 118.8, 76.2 (d,
JPC ¼ 6.7 Hz, Cp), 74.9 (d, JPC ¼ 26.8 Hz, CH), 73.0, 71.9, 71.3, 69.9. 31
P
NMR (162 MHz, CD2Cl2, 296 K)
d
(ppm) ꢁ29.9 (s). Minor: 1H NMR
Please cite this article as: C.F. Czauderna et al., P-stereogenic wide bite angle diphosphine ligands, Tetrahedron, https://doi.org/10.1016/
j.tet.2018.10.070

C.F. Czauderna et al. / Tetrahedron xxx (xxxx) xxx
7
(400 MHz, CD2Cl2, 296 K)
d
(ppm) 7.40-7.23 (m, 10H, PhH), 7.06-6.9
4.13. N,N-diethylamino-1-ferrocenyl-1-phenylphosphine borane
(17)
3
3
(m, 6H), 6.34 (dd, 2H, JHH ¼ 7.6 Hz, JPH ¼ 3.5 Hz, PhH), 4.42-4.40
(m, 2H, Cp), 4.38-4.36 (m, 4H, Cp), 4.05 (s, 5H, Cp), 3.82-3.81 (m, 5H,
Cp). 31P NMR (162 MHz, CD2Cl2, 296 K)
d
(ppm) ꢁ28.7 (s).
tBuLi (11.6 mL, 18.58 mmol, 1.6 M in pentane) was added to a
solution of bromoferrocene (2.459 g, 9.28 mmol) in diethylether
(50 mL) via cannula at ꢁ78 ꢀC. The reaction mixture was stirred
at ꢁ78 ꢀC for 1.5 h before it was placed into an ice-bath for 30 min.
The reaction mixture was cooled again to ꢁ78 ꢀC before being
4.10. L2-(BH3)2
L2 was azeotropically dried with toluene (3 ꢂ 20 mL) and dis-
solved in THF (100 mL) before adding a 2M BH3.SMe2 solution in
THF (14.12 mL, 28.34 mmol). After 1 h, the reaction mixture was
concentrated and the precipitate was azeotropically dried with
toluene (3 ꢂ 20 mL) to remove excess BH3SMe2. The precipitate was
suspended in DCM and washed with brine (50 mL) and water
(50 mL). The organic layer was dried over MgSO4 and the solvent
was removed in vacuo to give L2-(BH3)2 as orange solid (yield:
added to
a solution of 1-chloro-N,N-diethylamino-1-phenyl-
phosphine 15 in diethylether (50 mL) at ꢁ78 ꢀC. The reaction
mixture was stirred at ꢁ78 ꢀC for 1 h before being placed into an
ice-salt mixture (ꢁ18 ꢀC) and allowed to warm to r.t. overnight. The
conversion was monitored by 31P NMR spectroscopy. At r.t. a so-
lution of BH3.SMe2 (9.28 mL, 18.56 mmol, 2 M in THF) was added to
the reaction mixture. After 1 hour, solvent and excess of BH3.SMe2
were removed under high vacuum. The reaction mixture was sus-
pended in CH2Cl2, extracted with water, the organic phase was
dried over MgSO4 and the solvent removed in vacuo. The crude
product was purified by column chromatography (SiO2, eluent:
hexane:ethyl acetate 25:1, gradient increased to hexane:ethyl ac-
etate 25:2). 17 was obtained as orange solid (yield: 3.05 g,
5.43 g, 11.44 mmol, 81%). 1H NMR (400 MHz, CD2Cl2, 296 K)
d (ppm)
3
4
4
7.55 (ddd, 2H, JHH ¼ 7.7 Hz, JHH ¼ 1.53 Hz, JPH ¼ 12.8 Hz, PhH),
7.38-7.32 (m, 4H, PhH), 7.30-7.23 (m, 6H, PhH), 7.19-7.15 (m, 2H,
3
PhH), 7.07-7.04 (m, 2H, PhH), 6.21 (ddd, 2H, JHH ¼ 8.3 Hz,
3
4JHH ¼ 0.7 Hz, JPH ¼ 3.9 Hz, PhH), 4.51-4.49 (m, 2H, Cp), 4.43-4.39
8.04 mmol, 84%). 1H NMR (400 MHz, CDCl3, 296 K)
d (ppm) 7.72
(m, 4H, Cp), 4.14-4.13 (m, 2H, Cp), 4.03 (s, 5H, Cp), 1.8-0.8 (broad m,
6H; BH3). 13C NMR (100 MHz, CD2Cl2, 296 K)
d (ppm) 160.7, 135.0 (d,
(broad s, 2H, PhH), 7.45 (s, 3H, PhH), 4.56 (broad s, 1H, cp), 4.52
(broad s, 1H, Cp), 4.48 (broad s, 1H, Cp), 4.39 (broad s, 1H, Cp), 4.31
(broad s, 5H, Cp), 3.16-3.09 (m, 4H, CH2), 1.04 (broad s, 6H, CH3) 1.8-
JPC ¼ 10.4 Hz), 133.3, 132.8 (d, JPC ¼ 10.8 Hz), 131.0, 130.8, 130.4,
128.5 (d, JPC ¼ 10.8 Hz), 123.9 (d, JPC ¼ 10.2 Hz), 122.6 (d,
JPC ¼ 4.8 Hz), 122.5, 122.0, 74.0 (d, JPC ¼ 9.4 Hz, Cp), 73.5 (d,
JPC ¼ 10.8 Hz, CH), 72.5 (d, JPC ¼ 7.9 Hz, Cp), 71.7 (d, JPC ¼ 7.8 Hz, Cp),
0.8 (broad m, 3H; BH3). 13C NMR (100 MHz, CD2Cl2, 296 K)
d (ppm)
134.5, 133.9, 131.5 (d, JPC ¼ 5.9 Hz), 130.5, 128.2 (d, JPC ¼ 5.9 Hz), 72.8
(d, JCPC ¼ 70.8 Hz), 72.7 (d, JPC ¼ 9.9 Hz), 71.8 (d, JPC ¼ 10.4 Hz), 71.2
(d, JPC ¼ 7.5 Hz), 71.0 (d, JPC ¼ 7.3 Hz), 70.0. m.p. 54e58 ꢀC. Mass
(TOF-MS ESIþ) m/z calculated for [C20H27BNFePþNa]þ [MþNa]þ
402.1221, obs.: 402.1215 [MþNa]þ.1H NMR (400 MHz, CDCl3,
70.2 (Cp), 69.2 (d, JPC ¼ 70.8 Hz, Cp). 31P NMR (162 MHz, CD2Cl2,
20
296 K)
d a]
(ppm) 12.83 (broad, P-BH3). m.p. 190e194 ꢀC. [
D
(c ¼ 0.252, CHCl3) ¼ 163.2ꢀ. Mass (TOF-MS ESIþ) m/z calculated for
[C44H42B2Fe2OP2þNa]þ 805.1494 [MþNa]þ, obs.: 805.1486
[MþNa]þ.
296 K):
d (ppm) 7.35-7.25 (m, 3H), 7.20-7.18 (m, 2H), 2.96-2.91 (m,
2
3
4H, CH2), 1.42 (d, 3H, JPH ¼ 5.72, CH3), 1.00 (t, 6H, JHH ¼ 7.1 Hz,
CH3). 13C NMR (100 MHz, CDCl3, 296 K):
d
(ppm) 144.5 (d,
4.11. Chloro(N,N-diethylamino)phenylphosphine (15)
JPC ¼ 14.6 Hz), 129.6 (d, JPC ¼ 15.9 Hz), 128.0 (d, JPC ¼ 4.1 Hz), 127.2,
43.7 (d, JPC ¼ 14.7 Hz), 15.3 (d, JPC ¼ 3.1 Hz), 14.2 (d, JPC ¼ 18.4 Hz).
Chloro(N,N-diethylamino)phenylphosphine was synthesized
31P NMR (161 MHz, CDCl3, 296 K):
d (ppm) 83.2 (broad).
according to literature [34]. To
ophenylphosphine (26.96 g, 150.68 mmol) in diethylether (250 mL)
was added solution of diethylamine (31.2 mL, 22.04 g,
a
solution of dichlor-
a
301.4 mmol) in diethylether (50 mL) dropwise at 0 ꢀC. The reaction
mixture was stirred overnight. The reaction mixture was filtered
over a glass frit to remove ammonium salts and the diethylether
was removed by distillation under argon. The residue was distilled
under high vacuum to give 15 as clear oil (yield: 28.4 g, 131.4 mmol,
4.14. Synthesis of racemic L1
At ꢁ78 ꢀC dilithiodiphenyl ether (as the TMEDA-adduct) (0.75 g,
1.085 mmol) was suspended in diethyl ether (30 mL). After another
15 min at ꢁ78 ꢀC THF (15 mL) was added. Chloro(methyl)(phenyl)
phosphine (0.63 g, 3.9 mmol, 2.2 Eq.) dissolved in THF (50 mL) was
added via cannula at ꢁ78C. The reaction mixture was allowed to
warm to room temperature overnight. The reaction mixture was
quenched with degassed water (2 mL) and the solvent was
removed under vacuum. After azeotropically drying with toluene
(3 ꢂ 5 mL) the crude product was purified by filtration over silica
(SiO2, eluent: CH2Cl2:hexane 1:1 gradient increased to
CH2Cl2:hexane 2:1). The product was obtained as white oily solid
(yield: m ¼ 0.89 g, 2.145 mmol, 74%). 1H NMR (400 MHz, CDCl3,
88%). 1H NMR (400 MHz, C6D6, 296 K):
d (ppm) 7.83 (broad s, 2H),
7.23-7.18 (m, 3H), 3.04-2.95 (m, 4H, CH2), 0.94 (broad t, 6H,
3JHH ¼ 7.1 Hz, CH3). 13C NMR (100 MHz, C6D6, 296 K):
d (ppm) 140.0
(d, JPC ¼ 29.4 Hz), 131.0 (d, JPC ¼ 20.3 Hz), 129.8, 128.6 (d,
JPC ¼ 3.9 Hz), 44.1 (d, JPC ¼ 12.5 Hz, CH2), 14.1 (broad s, CH3). 31P
NMR (161 MHz, C6D6, 296 K):
(0.13 mbar).
d
(ppm) 141.0. b.p. 67e72 ꢀC
4.12. (N,N-diethylamino)(methyl)(phenyl)phosphine (16)
296 K):
d (ppm) 7.50-7.45 (m, 4H), 7.35-7.29 (m, 6H), 7.20-7.10 (m,
3
(N,N-diethylamino)(methyl)(phenyl)phosphine 16 was synthe-
sized via a modified literature procedure [35]. At ꢁ78 ꢀC, MeLi
(32.6 mL, 52.1 mmol, 1.6 M in diethylether) was added to a solution
of chloro(N,N-diethylamino)phenylphosphine (10.21 g, 47.4 mmol)
in diethylether (60 mL) at ꢁ78 ꢀC. During addition a white precip-
itate was formed. The reaction mixture was stirred at ꢁ78 ꢀC for 1 h
before the reaction mixture was placed in an ice/salt bath (ꢁ15 ꢀC)
and warmed up to r.t. overnight. The reaction mixture was filtered
over a P4 frit and the solution was concentrated under high
vacuum.
4H), 7.04-7.00((m, 2H), 6.59 (broad dd, 1H, JHH ¼ 8.1 Hz,
2JPH ¼ 2.98 Hz), 6.51(broad dd, 1H, JHH ¼ 8.1 Hz, JHP ¼ 2.98 Hz),
3 3
2
2
1.64 (d, 1H, JPH ¼ 4.1 Hz), 1.55 (d, 1H, JPH ¼ 4.1 Hz). 13C NMR
(100 MHz, CDCl3, 296 K):
d
(ppm) 158.0 (d, JPC ¼ 5.5 Hz), 157.8 (d,
JPC ¼ 4.7 Hz), 137.8 (d, JPC ¼ 5.8 Hz),137.7(d, JPC ¼ 5.0 Hz), 131.8, 131.7,
131.6, 131.5, 131.1, 130.8, 130.7, 130.5 (d, JPC ¼ 16.5 Hz), 130.3 (d,
JPC ¼ 17.5 Hz), 128.8, 128.7, 127.5, 127.4, 127.31, 127.27, 127. 127.25,
127.2, 122.4, 122.3, 117.0, 116.97, 10.2 (d, JPC ¼ 3.5 Hz), 10.1 (d,
JPC ¼ 4.1 Hz).
(ppm) ꢁ35.4, ꢁ35.6.
31P
NMR
(161 MHz,
CDCl3,
296 K):
d
Please cite this article as: C.F. Czauderna et al., P-stereogenic wide bite angle diphosphine ligands, Tetrahedron, https://doi.org/10.1016/
j.tet.2018.10.070

8
C.F. Czauderna et al. / Tetrahedron xxx (xxxx) xxx
4.15. L1-(BH3)2
(q, JPB ¼ 71.5 Hz, P-BH3). m.p. 44e48 ꢀC. Mass (TOF-MS ESIþ) m/z
calculated for [C22H22BFeOPþNa]þ423.0748 [MþNa]þ, obs.:
423.0753 [MþNa]þ.
The product L1 was dissolved in THF (50 mL) and BH.3SMe2
(3.97 mmol, 2 M in toluene)was added. After stirring for 16 h, sol-
vent and excess of BH.3SMe2 were removed in high vacuum. The
reaction mixture was solved in CH2Cl2, washed with water and
dried with MgSO4. After removal of the solvent, the product was
obtained as white powder (0.95 g, 2.145 mmol, 100%). No further
purification was carried out. 1H NMR (400 MHz, CDCl3, 296 K):
4.17. (rac)-13
A solution of DABCO (1.29 g, 11.58 mmol) in toluene (40 mL) was
added to a solution of (rac)-13-BH3 (1.15 g, 2.88 mmol, azeotropi-
cally dried with toluene) in diethyl ether (100 mL). The reaction
mixture was heated for 20 h at 60 ꢀC. After cooling down to r.t.,
toluene was removed in vacuo. Purification by filtration over silica
(SiO2, eluent: ethyl acetate) resulted in an orange solid that was
used without further purification (yield: 1.04 g, 2.69 mmol, 94%). 1H
3
4
4
d
(ppm) 8.00 (ddd, 1H, JHH ¼ 7.7 Hz, JHH ¼ 1.7 Hz, JPH ¼ 13.3 Hz,
3 4
PhH), 7.84-7.74 (m, 3H), 7.65 (ddd, 1H, JHH ¼ 7.7 Hz, JHH ¼ 1.7 Hz,
4JHP ¼ 12.8 Hz, PhH), 7.52-7.05 (m, 34H), 6.67 (ddd, 1H,
3JHH ¼ 7.9 Hz, JHH ¼ 0.9 Hz, JPH ¼ 3.5 Hz, PhH), 6.37 (ddd, 1H,
4
3
3JHH ¼ 8.2 Hz, JHH ¼ 1.0 Hz, JPH ¼ 3.0 Hz, PhH), 6.00 (ddd, 2H,
4
3
3JHH ¼ 7.8 Hz, JHH ¼ 1.4 Hz, JPH ¼ 3.5 Hz, PhH), 5.67 (ddd, 1H,
NMR (500 MHz, CD2Cl2, 296 K) d (ppm) 7.77-7.74 (m, 2H, PhH),
4
3
3JHH ¼ 8.0 Hz, JHH ¼ 1.3 Hz, JPH ¼ 3.4 Hz, PhH), 1.82 (d, 3H,
7.46e8.42 (m, 3H, PhH), 7.26 (t, 2H, JHH ¼ 7.7 Hz), 7.10 (d, 2H,
3JHH ¼ 7.7 Hz), 6.98 (t, 1H, 3JHH ¼ 7.3 Hz), 4.53 (broad s, 1H, Cp), 4.45
(broad s, 1H, Cp), 4.36 (broad s, 1H, Cp), 4.41 (s, 5H, cp), 4.01 (broad
4
3
3
3JPH ¼ 10.2 Hz, CH3), 1.64 (d, 6H, JPH ¼ 10.2 Hz, CH3), 1.47 (d, 3H,
3
3JPH ¼ 10.4 Hz,CH3), 1.4-0.3 (broad m, 6H; BH3). 13C NMR (100 MHz,
1
CDCl3, 296 K):
d
(ppm) 160.1, 159.5, 135.8 (d, 6H, JCP ¼ 14.9 Hz),
s, 1H, Cp). 13C NMR (126 MHz, CD2Cl2, 296 K)
d (ppm) 156.63 (d,
3
135.2 (d, JPC ¼ 12.8 Hz), 134.2, 134.1, 133.8, 133.7, 132.2, 131.9 (d,
JPC ¼ 9.2 Hz), 139.8 (d, JPC ¼ 17.2 Hz), 129.7 (d, JPC ¼ 23.1 Hz), 129.0,
128.6, 127.4 (d, JPC ¼ 7.6 Hz), 121.3, 117.8 (d, JPC ¼ 11.2 Hz), 78.1 (d,
JPC ¼ 12.7 Hz, Cp), 71.6 (d, JPC ¼ 22.6 Hz, Cp), 70.9 (d, JPC ¼ 5.6 Hz,
Cp), 70.4, 70.3 (d, JPC ¼ 15.5 Hz, Cp), 68.2 (Cp). 31P NMR{1H}
3JPC ¼ 10.1 Hz), 131.8, 131.6 (d, JPC ¼ 9.8 Hz), 131.5, 131.4 (d,
3
3JPC ¼ 10.6 Hz), 131.3, 130.9, 130.8, 130.2, 129.3 (d, JPC ¼ 10.2 Hz),
3
3
3
129.0 (d, JPC ¼ 10.3 Hz), 128.7 (d, JPC ¼ 10.3 Hz), 124.6 (d,
3JPC ¼ 11.8 Hz), 124.4 (d, JPC ¼ 11.0 Hz), 124.3 (d, JPC ¼ 10.8 Hz),
(162 MHz, CD2Cl2, 296 K) d (ppm) 107.02 (s, P-BH3).
3
3
122.7, 122.1, 121.2, 120.7, 120.65, 120.6, 120.4 (d, 3JPC ¼ 3.9 Hz), 120.1
(d, JPC ¼ 3.9 Hz), 11.1 (d, JPC ¼ 41.4 Hz, CH3), 9.6 (d, 1JPC ¼ 42.1 Hz,
3
1
CH3). 31P NMR{1H}(161 MHz, CDCl3, 296 K):
d
(ppm) 9.7 (broad, P-
4.18. Synthesis of racemic L2
BH3), 7.4(broad, P-BH3). m.p. ¼144e148 ꢀC. LCTOF: m/z calculated
for [C26H30B2OP2þNa]þ: m ¼ 465.1856 (MþNa)þ, obs.: 486.1859
(MþNa)þ.
At ꢁ78 ꢀC, dilithiodiphenyl ether (as the TMEDA-adduct)
(0.409 g, 0.987 mmol) was suspended in diethyl ether (30 mL). Af-
ter 15 min at ꢁ78 ꢀC, THF (15 mL) was added. A solution of (rac)-13
(0.801 g, 2.07 mmol, 2.2 Eq.) in THF (50 mL) was added at ꢁ78 ꢀC via
cannula. The reaction mixture was slowly warmed to room tem-
perature overnight. The reaction mixture was quenched with
degassed water (2 mL) and the solvent was removed under vac-
uum. The precipitate was suspended in CH2Cl2 and washed with
water and brine, dried over MgSO4 and the solvent was removed.
The crude product was purified by filtration over silica (SiO2,
eluent: CH2Cl2:hexane 1:1 gradient increased to CH2Cl2:hexane
2:1) to give L2 as orange solid (yield: 618 mg, 0.81 mmol, 83%). 1H
4.16. (rac)-13-(BH3)
HCl (18.49 mL, 37.0 mmol, 2M in Et2O) was added to a solution of
18-BH3 (2.34 g, 6.16 mmol, azeotropically dried with toluene) at
0 ꢀC. The reaction mixture was allowed to warm to r.t. over the
course of 30 min. After 1.5 h full conversion was reached, as indi-
cated by 31P NMR spectroscopy. The reaction mixture was filtered
over a glass frit (P4) and solvent was removed. The crude product
was dissolved in diethyl ether (50 mL) and the precipitate was
removed by filtration over a glass frit (P4). (31P NMR (162 MHz,
NMR (400 MHz, CD2Cl2, 296 K)
d (ppm) 7.40-7.23 (m, 20H, PhH),
3
3
CD2Cl2, 296 K)
d
(ppm) 94.9 (broad, 1JPB ¼ 45.5 Hz, P-BH3)). A solu-
7.06-6.9 (m, 12H), 6.34 (dd, 2H, JHH ¼ 7.6 Hz, JPH ¼ 3.5 Hz, PhH),
3 3
tion of phenol (4.062 g, 4.316 mmol, azeotropically dried with
toluene) in tetrahydrofuran (20 mL) was slowly added via cannula
to a suspension of NaH (4.062 g, 4.316 mmol) at 0 ꢀC. The reaction
mixture was stirred at 0 ꢀC for 30 min and for 2 h at r.t. The
phenolate solution was added to the second (phosphorus-con-
taining) solution in tetrahydrofuran (90 mL) at ꢁ78 ꢀC via cannula.
The reaction mixture was allowed to warm to r.t. overnight. After
quenching the solution with water, the solvent was removed and
the product was extracted with water and dichloromethane. The
organic layer was dried over MgSO4, filtered and the solvent was
removed. The crude product was purified by column chromatog-
raphy (SiO2, eluent: 100% toluene) to give (rac)-13-BH3 as orange
solid (yield: 1.29 g, 3.3 mmol, 75%). 1H NMR (500 MHz, CD2Cl2,
6.20 (dd, 2H, JHH ¼ 7.6 Hz, JPH ¼ 3.5 Hz, PhH), 4.42-4.40 (m, 2H,
Cp), 4.37-4.32 (m, 4H, Cp), 4.07 (s, 5H, Cp), 4.02 (s, 5H, Cp), 3.87-
3.86 (m, 1H, Cp), 3.80-3.79 (m, 1H, Cp). 13C NMR (100 MHz, CD2Cl2,
296 K)
d
(ppm) 159.8 (d, JPC ¼ 18.3 Hz), 159.1 (d, JPC ¼ 16.9 Hz),
139.0-138.2 (m), 134.9 (d, JPC ¼ 7.0 Hz), 135.1, 134.9, 134.8, 134.6 (d,
JPC ¼ 11.8 Hz), 134.2, 132.3 (d, JPC ¼ 16.4 Hz), 130.6, 130.3, 129.2,
128.7-128.55 (m),123.8 (d, JPC ¼ 12.6 Hz),118.8,118.2, 76.1-76.0 (m),
75.4, 75.1 (d, JPC ¼ 26.7 Hz, Cp), 76.1 (d, JPC ¼ 26.8 Hz, CH), 73.0, 72.8,
72.0-71.9 (m), 71.3, 71.2, 69.9, 69.8. 31P NMR (162 MHz, CD2Cl2,
296 K)
d
(ppm) ꢁ28.8 (s), ꢁ29.9 (s). m.p.178 ꢀC. Mass (TOF-MS ESIþ)
m/z calculated for [C44H36Fe2OP2þNa]þ 777.0838 [MþNa]þ, obs.:
777.0831[MþNa]þ.
296 K) d (ppm) 8.03-7.99 (m, 2H, PhH), 7.62-7.53 (m, 3H, PhH), 7.23
3
3
(t, 2H, JHH ¼ 7.3 Hz), 7.09 (t, 1H, JHH ¼ 7.4 Hz), 6.99 (d, 2H,
3JHH ¼ 7.8 Hz), 4.7 (broad s, 1H, cp), 4.55 (broad s, 1H, Cp), 4.51
(broad s, 1H, Cp), 4.39 (broad s, 1H, Cp), 4.13 (broad s, 5H, Cp), 1.8-
4.19. L2-(BH3)2
BH.3SMe2 (50
mL, 0.1 mmol, 2 M in THF) was added to a solution
0.8 (broad m, 3H; BH3). 13C NMR (126 MHz, CD2Cl2, 296 K)
d
(ppm)
of L2 (15 mg, 0.02 mmol) in THF (5 mL). After stirring for 16 h,
solvent and excess of BH3. SMe2 were removed in high vacuum.
(rac)-L2-(BH3)2 was only used for NMR spectroscopy and not
further purified. (Yield: 15 mg, 0.019 mmol, 100%). 31P NMR
(162 MHz, CD2Cl2, 296 K)
P-BH3).
153.3(d, JPC ¼ 5.9 Hz), 133.1, 133.0 (d, JPC ¼ 2.1 Hz), 132.6, 132.0 (d,
JPC ¼ 11.3 Hz), 130.0, 129.3 (d, JPC ¼ 10.4 Hz), 125.2, 122.1 (d,
JPC ¼ 3.9 Hz), 73.4 (d, JPC ¼ 8.2 Hz, CH), 72.2 (d, JPC ¼ 13.3 Hz, Cp),
73.0 (d, JPC ¼ 8.7 Hz, Cp), 72.5 (d, JPC ¼ 10.3 Hz), 71.8 (d, JPC ¼ 77 Hz,
d (ppm) 15.2 (broad, P-BH3), 12.6 (broad,
Cp), 70.9 (Cp). 31P NMR{1H} (162 MHz, CD2Cl2, 296 K
d (ppm) 110.3
Please cite this article as: C.F. Czauderna et al., P-stereogenic wide bite angle diphosphine ligands, Tetrahedron, https://doi.org/10.1016/
j.tet.2018.10.070

C.F. Czauderna et al. / Tetrahedron xxx (xxxx) xxx
9
[3] Early examples: a) W.S. Knowles, M.J. Sabacky, B.D. Vineyard, J. Chem. Soc.
Chem. Commun. (1972) 10e11;
4.20. X-ray crystallography
b) W. S. Knowles, M. J. Sabacky, B. D. Vineyard, US Patent 4005127, 1977. c)
B.D. Vineyard, W.S. Knowles, M.J. Sabacky, G.L. Bachman, D.J. Weinkauff, J. Am.
Chem. Soc. 99 (1977) 5946e5952.
X-ray diffraction data for all compounds were collected at 93 K
by using a Rigaku MM007 High-brilliance RA generator/confocal
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O.I. Kolodiazhnyi, Top. Curr. Chem. 360 (2014) 161e236;
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K
a
radiation
and 4
(l
¼ 0.71075 Å). Intensity data were collected using both
u
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b) M. Dutartre, J. Bayardon, S. Juge, Chem. Soc. Rev. 45 (2016) 5771e5794;
c) P. Bagi, V. Ujj, M. Czugler, E. Fogassya, G. Keglevich, Dalton Trans. 45 (2016)
1823e1842;
steps accumulating area detector images spanning at least a
hemisphere of reciprocal space. All data were corrected for Lorentz
polarization effects and a multiscan absorption correction was
applied by using CrystalClear [36]. Structures were solved by direct
(SIR2002 [37] or SIR2004 [38]) or Patterson (PATTY [39]) methods
and refined by full-matrix least-squares against F2 (SHELXL-2013
[40]). Non-hydrogen atoms were refined anisotropically, and
hydrogen atoms were refined using a riding model. The positions of
boron-bound hydrogens were located from the difference Fourier
map, and the riding model applied from these positions. All cal-
culations were performed using the CrystalStructure [41] interface.
CCDC 1516737-1516740 contains the supplementary crystallo-
graphic data for this paper. The data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via www.ccdc.
cam.ac.uk/structures.
d) Y.-M. Cui, Y. Lin, L.-W. Xu, Coord. Chem. Rev. 330 (2017) 37e52.
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W. Zhang, Org. Lett. 15 (2013) 5476e5479;
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b) E. Cristobal-Lecina, P. Etayo, S. Doran, M. Reves, P. Martín-Gago,
A. Grabulosa, A.R. Costantino, A. Vidal-Ferran, A. Riera, X. Verdaguer, Adv.
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c) H. Fernandez-Perez, J. Benet-Buchholz, A. Vidal-Ferran, Chem. Eur. J. 20
(2014) 15375e15384;
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Crystal Data for (R,R)-10-BH3 (M ¼ 859.85 g/mol): orthorhombic,
P212121 (no. 19), a ¼ 9.608(3) Å, b ¼ 18.042(7) Å, c ¼ 25.956(11) Å,
V ¼ 4499(3) Å3, Z ¼ 4,
m
¼ 0.316 mmꢁ1, Dcalc ¼ 1.269 g/cm3, 28747
l) O. Berger, J.-L. Montchamp, Org. Biomol. Chem. 14 (2016) 7552e7562;
m) R. Bigler, R. Huber, A. Mezzetti, Synlett 27 (2016) 831e847;
reflections measured, 8176 unique (Rint ¼ 0.1593) which were used
ꢁ
n) C. Schmitz, K. Holthusen, W. Leitner, G. Francio, ACS Catal. 6 (2016)
in all calculations. The final R1 was 0.0830 (I > 2s(I)) and wR2 was
1584e1589;
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o) J. Bayardon, Y. Rousselin, S. Juge, Org. Lett. 18 (2016) 2930e2933.
0.2178 (all data). CCDC 1516737.
[6] a) A. Grabulosa, P-stereogenic Ligands in Enantioselective Catalysis, Royal
Society of Chemistry, 2011;
Crystal Data for (R,R)-10-(BH3)2 (M ¼ 474.09 g/mol): ortho-
rhombic, P212121 (no. 19), a ¼ 8.711(4) Å, b ¼ 14.700(5) Å,
€
b) T. Imamoto, in: A. Borner (Ed.), Synthesis of P-stereogenic Phosphines via
c ¼ 20.045(8) Å, V ¼ 2566.6(18) Å3, Z ¼ 4,
m
¼ 0.194 mmꢁ1
,
Enantioselective Alkylation in Phosphorus Ligands in Asymmetric Catalysis,
Wiley, 2008, p. p1201;
Dcalc ¼ 1.227 g/cm3, 16296 reflections measured, 4681 unique
(Rint ¼ 0.0903) which were used in all calculations. The final R1 was
ꢀ
€
c) C. Darcel, J. Uziel, S. Juge, in: A. Borner (Ed.), Synthesis of P-stereogenic
Phosphorus Compounds Based on Chiral Amino Alcohols as Chiral Auxiliary in
in Asymmetric Catalysis, Wiley, 2008.
0.0844 (I > 2s(I)) and wR2 was 0.2315 (all data). CCDC 1516738.
[7] W.S. Knowles, Angew. Chem. 114 (2002) 2096e2107. Angew. Chem., Int. Ed.
Engl. 41 (2002) 1998-2007.
Crystal Data for (S,S)-L1-(BH3)2 (M ¼ 442.09 g/mol): ortho-
rhombic, P212121 (no. 19), a ¼ 10.781(2) Å, b ¼ 13.320(2) Å,
[8] A. Grabulosa, J. Granell, G. Muller, Coord. Chem. Rev. 251 (2007) 25e90.
[9] T. Imamoto, T. Kusumoto, N. Suzuki, K. Sato, J. Am. Chem. Soc. 107 (1985)
c ¼ 17.524(3) Å, V ¼ 2516.5(7) Å3, Z ¼ 4,
m
¼ 0.188 mmꢁ1
,
́
Dcalc ¼ 1.167 g/cm3, 15815 reflections measured, 4565 unique
(Rint ¼ 0.0274) which were used in all calculations. The final R1 was
5301e5303.
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Crystal Data for (S,S)-L2 (M ¼ 754.41 g/mol): orthorhombic,
P212121 (no. 19), a ¼ 9.459(2) Å, b ¼ 14.416(2) Å, c ¼ 25.888(5) Å,
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ꢀ
b) T. Leon, A. Riera, X. Verdaguer, J. Am. Chem. Soc. 133 (2011) 5740e5743;
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c) H. Zijlstra, T. Leon, A. de Cozar, C. Fonseca Guerra, D. Byrom, A. Riera,
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M. Lutz, J. Org. Chem. 64 (1999) 3996e4004. See also:;
in all calculations. The final R1 was 0.0426 (I > 2s(I)) and wR2 was
0.675 (all data). CCDC 1516740.
b) U. Nettekoven, M. Widhalm, P.C.J. Kamer, P.W.N.M. van Leeuwen,
K. Mereiter, M. Lutz, A.L. Spek, Organometallics 19 (2000) 2299e2309;
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Acknowledgements
This work was supported by an EASTCHEM fellowship. We
would like to acknowledge the European Union for additional
funding through a Marie Curie Excellence Grant MEXT-2004-
014320 and COST action CM0802 PhoSciNet..
d) U. Nettekoven, M. Widhalm, H. Kalchhauser, P.C.J. Kamer, P.W.N.M. van
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Appendix A. Supplementary data
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1e15. Recent examples from our group;
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.tet.2018.10.070.
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Please cite this article as: C.F. Czauderna et al., P-stereogenic wide bite angle diphosphine ligands, Tetrahedron, https://doi.org/10.1016/
j.tet.2018.10.070