Asymmetric synthesis of P-stereogenic o-hydroxyaryl-phosphine (borane) and phosphine-phosphinite ligands

Article abstract of DOI:10.1016/S0957-4166(00)00372-4

The first asymmetric synthesis of P-stereogenic 2-hydroxyarylphosphine ligands is described, using borane complexation methodology. This synthesis is based on the highly stereoselective preparation of bromoarylphosphinite boranes, leading to the 2-hydroxyarylphosphine derivatives, by an intramolecular ortho Fries-like rearrangement mediated in basic conditions. The o-anisyl-2-hydroxynaphthylphenylphosphine borane has been decomplexed in EtOH, affording the P(III)-stereogenic hydroxyarylphosphine ligand with 84% yield. The interest of the hydroxyarylphosphine borane is also demonstrated by the preparation of a new class of phosphine-phosphinite ligands, by trapping the rearrangement products first with chlorodiphenylphosphine, Ph₂PCl, then with borane. The corresponding phosphine-phosphinites are obtained and purified as diborane complexes, with the decomplexation of these borane complexes being achieved by heating with dabco, to afford the free hybrid ligands with retention of the configuration at the P-atom (isolated yield up to 53%). Copyright (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0957-4166(00)00372-4

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 11 (2000) 3939–3956
Asymmetric synthesis of P-stereogenic o-hydroxyaryl-
phosphine (borane) and phosphine-phosphinite ligands†
Dominique Moulin, Se´bastien Bago, Christophe Bauduin, Christophe Darcel and
Sylvain Juge´*
Unite´ mixte Universite´ de Cergy-Pontoise/ESCOM-Synth. Org. Se´lect. et Chim. Organome´t., FRE CNRS 2126,
5 mail Gay Lussac, 95031 Cergy-Pontoise Cedex, France
Received 25 July 2000; accepted 14 September 2000
Abstract
The first asymmetric synthesis of P-stereogenic 2-hydroxyarylphosphine ligands is described, using
borane complexation methodology. This synthesis is based on the highly stereoselective preparation of
bromoarylphosphinite boranes, leading to the 2-hydroxyarylphosphine derivatives, by an intramolecular
ortho Fries-like rearrangement mediated in basic conditions. The o-anisyl-2-hydroxynaphthylphenylphos-
phine borane has been decomplexed in EtOH, affording the P(III)-stereogenic hydroxyarylphosphine
ligand with 84% yield. The interest of the hydroxyarylphosphine borane is also demonstrated by the
preparation of a new class of phosphine-phosphinite ligands, by trapping the rearrangement products first
with chlorodiphenylphosphine, Ph2PCl, then with borane. The corresponding phosphine-phosphinites are
obtained and purified as diborane complexes, with the decomplexation of these borane complexes being
achieved by heating with dabco, to afford the free hybrid ligands with retention of the configuration at
the P-atom (isolated yield up to 53%). © 2000 Elsevier Science Ltd. All rights reserved.
1. Introduction
During the last three decades, considerable developments have been made for asymmetric
transition-metal catalyzed reactions1 and more precisely in the synthesis of numerous chiral
ligands.2 In this area, the most commonly used P(III)-organophosphorus ligands (diphosphines,3
diphosphinites, diphosphites,4 aminophosphine-phosphinites,5 chelating monophosphines or
P(III) derivatives)6 generally bear the chirality on the carbon backbone. Since the asymmetric
* Corresponding author. Fax: 33 1 34 25 70 67; e-mail: sylvain.juge@chim.u-cergy.fr
†
This work has been presented in part at the 10th IUPAC Symposium on Organo-Metallic Chemistry directed
towards Organic Synthesis (OMCOS), Versailles, France, July 19–22, 1999.
0957-4166/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
PII: S0957-4166(00)00372-4

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synthesis of P(III)-organophosphorus compounds has made important progress by the use of
borane as a protecting group,7–9 P-stereogenic phosphorus ligands have revived interest in
catalysis.10 Thus, it is now possible to study new kinds of bulky,11 hybrid or functionalized
phosphorus ligands,12 bearing the chirality close to the metal center, for the study of new
catalytic species. Moreover, P-stereogenic centers may amplify the influence of the chiral carbon
backbone, to increase the asymmetric induction of the catalyst.13
Recently, chiral organophosphorus derivatives bearing an o-hydroxyaryl substituent have
gained attention because these compounds, could be used either as ligands14 or catalysts in
various asymmetric reactions.15 The preparation of these compounds could be achieved by
demethylation of a methoxy substituent,15a,16 or by trapping a C,O-phenol dilithium reagent
with a chlorophosphine.17 A more convenient method has been developed on the basis of the
ortho Fries-like rearrangement of the corresponding aryl phosphoric ester 1.18 This method,
which proceeds with complete retention of the configuration at the phosphorus center,19 has
been particularly studied by Buono et al. in order to prepare various P-stereogenic o-hydroxy-
aryl phosphonic derivatives 220 (Scheme 1).
Scheme 1.
Continuing our research on asymmetric synthesis of organophosphorus compounds, we have
reported the synthesis of chiral chlorophosphine boranes 3, which are useful electrophilic blocks
for the preparation of P-stereogenic cyclopentadienyl methyl phenyl phosphine (borane) 4,7f or
aminophosphine-phosphinite ligands 5 (Fig. 1).13 Herein, we wish to report a convenient
synthesis of 2-bromoarylphosphinites (borane) 6 from 3, and their application in the first
preparation of P-stereogenic o-hydroxyarylphosphines 7 with high enantiomeric excesses.
Figure 1.

D. Moulin et al. / Tetrahedron: Asymmetry 11 (2000) 3939–3956
3941
2. Results and discussion
The chlorophosphine boranes 3 are prepared in two steps from the (+)-ephedrine derived
oxazaphospholidine borane 8, which is the starting complex for the P-stereogenic asymmetric
synthesis methodology.7 Thus, the acidolysis of the aminophosphine boranes 9, which are
prepared as pure diastereomers by reaction of complex 8 with organolithium reagents R1Li,
leads to chlorophosphines 3a–c (Scheme 2). After simple filtration of the ephedrine hydrochlo-
ride, the chlorophosphine boranes 3 are directly used without further purification, and react with
the corresponding bromophenate salt 10 to afford the corresponding arylphosphinite boranes 6
in 66–73% overall yields (Table 1). The enantiomeric excesses of the compounds 6 have been
determined by HPLC on a chiral column, of their derivative phosphine boranes 11 and 12,
which result from their reaction with o-anisyllithium or t-butyllithium, respectively (Schemes 2
and 3). The results are summarized in Table 1.
Scheme 2.
Table 1
Preparation of the arylphosphinite borane complexes 6
Entry
R1
ArONa 10
Arylphosphinite BH3 6
Yielda (%)
E.e. (%)
1
2
3
4
5
CH3
2-Bromophenate 10a
‘‘
‘‘
1-Bromo-2-naphthoate 10b
‘‘
6a
6b
6c
6d
6e
71
71b
80c
–
o-An
o-Tol
CH3
70
66
66
73
91d
100d
o-An
a Isolated yield from 9.
b Determined by HPLC with Chiralcel OK, from the PAMP·BH3 11 which results from the reaction with
o-anisyllithium.
c Determined by HPLC with Chiralcel OK from the derivative 12b.
d Determined by HPLC with Chiralcel OK, from the corresponding derivative 12d or 12e.
When methyllithium reacts with complex 8, the aminophosphine borane 9a is obtained with
retention of the configuration at the phosphorus atom.7e The reaction of 9a with dry HCl then
gives the methyl phenyl chlorophosphine borane 3a, which is trapped with the sodium
2-bromophenate 10a to afford the phosphinite borane 6a in 71% yield (Table 1, entry 1). The
HPLC analysis on a chiral column of the PAMP borane 11, which results from the reaction of
6a with o-anisyllithium, indicates an R absolute configuration and 71% e.e. (Scheme 3, Table 1,
entry 1). In the same way, the 2-bromoarylphosphinite borane complexes 6b and 6c have been

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D. Moulin et al. / Tetrahedron: Asymmetry 11 (2000) 3939–3956
Scheme 3.
prepared in 70 and 66% yields, respectively, by reaction of the o-anisyl or o-tolyllithium reagents
with complex 8, and trapping the chlorophosphine borane intermediates 3b and 3c with sodium
2-bromophenate 10a (entries 2, 3). If the chlorophosphine boranes 3a or 3b are trapped by the
sodium 1-bromo-2-naphthoate 10b, the phosphinite complexes 6d or 6e are obtained in 66 and
73% yields, respectively (entries 4, 5). It should be pointed out that the enantiomeric excesses of
6d, 6e (91–100% e.e.) have been determined from the hydroxyarylphosphine boranes 12d and
12e, which result from their intramolecular rearrangement, as described below. We think that
the variation of stereoselectivity observed for the arylphosphinite boranes 6 prepared must arise
either from the aminophosphine borane acidolysis step,21 or from reaction of the phenates 10a
(or 10b) with the chlorophosphine boranes 3, rather than from the reactions leading to their
derivatives 11 or 12.
On the other hand, the absolute configuration of the phosphinite borane 6d has been
established as S, by X-ray crystallography, owing to the presence of the bromine atom which
results in differences between the intensities of Friedel reflections (Fig. 2). This stereochemistry
is in good agreement with an inversion of configuration in the aminophosphine borane 9a
acidolysis step,21 and for the substitution of the chlorophosphine borane 3a by the naphthoate
salt 10b (Scheme 2). Moreover, it also confirms that the o-anisyllithium reaction of 6d, leading
to the (R)-PAMP BH3 11, proceeds with inversion of configuration (entry 4).
We have also studied the rearrangement of these arylphosphinite boranes 6, after formation
of the anion ortho to the aryloxy substituent, by halogen–metal exchange (Scheme 3). This
rearrangement was realized by reaction of the complex 6a–e with t-BuLi at −78°C, and after
increasing the temperature to 0°C, the corresponding o-hydroxyphosphine boranes 12a–e were
obtained in 48–96% yields (Table 2).
The rearrangement of the 2-bromophenylphosphinite borane 6a gives the o-hydroxy-
methylphenylphosphine borane 12a in 75% yield (Table 2, entry 1). After deprotonation of the

D. Moulin et al. / Tetrahedron: Asymmetry 11 (2000) 3939–3956
3943
,
Figure 2. Crystal structure of the 2-bromonaphthylphosphinite borane 6d. Selected bond lengths (A) angles (°),
dihedral angles (°): P(1)ꢀB(1) 1.92(1), P(1)ꢀO(1) 1.626(8), P(1)ꢀC(1) 1.79(1), P(1)ꢀC(2) 1.77(1), O(1)ꢀC(8) 1.35(2),
Br(1)ꢀC(9) 1.90(1); O(1)ꢀP(1)ꢀB(1) 114.3(6), B(1)ꢀP(1)ꢀC(1) 113.9(7), B(1)ꢀP(1)ꢀC(2) 114.6(7), O(1)ꢀP(1)ꢀC(2)
105.4(5), P(1)ꢀO(1)ꢀC(8) 122.8(7); C(3)ꢀC(2)ꢀP(1)ꢀB(1) 15.49, C(9)ꢀBr(1)ꢀP(1)ꢀB(1) 84.33
hydroxy group by NaH, then alkylation with CH3I, 12a leads to the (S)-PAMP·BH3 11
(Scheme 3; entry 1). As the phosphinite borane 6a leads directly or via the hydroxyphosphine
borane 12a to the two enantiomers of the PAMP·BH3 11 with the same enantiomeric purity,
this proves the stereospecificity of the rearrangement which proceeds with complete retention
of configuration at the P-center (Scheme 3). Consequently, these results show similar
stereospecificity of the rearrangement for the phosphinite borane complexes, with respect to
the phosphate series.19 In the case of the o-anisyl or o-tolylphosphinite borane 6b or 6c, the
rearrangement leads to the corresponding o-hydroxyarylphosphine boranes 12b and 12c in
good yields (>60%, entries 2, 3). The enantiomeric excess of the hydroxyarylphosphine com-
plex 12b has been established by HPLC on a chiral column of its (S)-(−)-O-acetyllactyl
derivative (80% e.e., entry 2). Finally, when the 1-bromo-2-naphthylphosphinite borane 6d or
6e are treated with t-BuLi, the rearrangement affords the corresponding 2-hydroxy-
napthylphosphine borane 12d or 12e, in 96 and 48% yields, respectively, and with enantiomeric
excesses up to 100% e.e. (entries 4, 5).
In order to explain the retention of configuration during the rearrangement of the com-
plexes 6, we have examined the stereochemical pathway of all pentacoordinate intermediates,
which result from the intramolecular nucleophilic attack, using the topological
representation22a shown in Fig. 3. In this topological representation, each top corresponds to
the possible pentacoordinate stereoisomers, while the lines represent the stereopermutations
(Berry or turnstile rotation), allowing the passage from one stereoisomer to another. It should
be pointed out that each pentacoordinate intermediate could isomerize into a maximum of
three others stereoisomers by one stereopermutation (Berry or TR).

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D. Moulin et al. / Tetrahedron: Asymmetry 11 (2000) 3939–3956
Table 2
Rearrangement of the arylphosphinites 6 into o-hydroxyarylphosphine boranes 12
The possible pentacoordinate intermediates are defined by the substituents in the apical
positions following the normal convention.23 Usually, the substituents are numbered arbitrarily
or by taking into account their electronegativity22b or the existence of a ring.22a Here, the

D. Moulin et al. / Tetrahedron: Asymmetry 11 (2000) 3939–3956
3945
substituents of the phosphorus atom are ranked from 1 to 5 following their ‘relative stereo-
apicophilicity’.24 This ranking considers the apicophilicity25 and steric hindrance of the five
substituents, including the nucleophile, around the phosphorus center, thus leading to the
increasing order of the series: OAr>Ar>Ph>R>BH3. Consequently, this ranking corresponds to
the relative aptitude of the substituents to occupy an apical position in the P-stereogenic
pentacoordinate intermediate. As the substituents ranked 1 and 2 are borne by the same group,
the formation of the two pentacoordinate intermediates {12} and {12} could not be observed
and are not represented in Fig. 3.
Figure 3.
On this basis, the three initial pentacoordinate intermediates which could arise from the
intramolecular nucleophilic attack of the ortho-anion on the accessible side faces of the
tetrahedral phosphorus center of 6 are {23}, {25} and {24} (Scheme 4).
Scheme 4.
Although it was generally assumed that the nucleophilic attack on the edges of the tetrahedral
phosphorus center requires higher energy,26 three other early pentacoordinate intermediates
could also be envisaged from this approach (i.e. {14}, {13}, {15}). If we examine Fig. 3, we

3946
D. Moulin et al. / Tetrahedron: Asymmetry 11 (2000) 3939–3956
notice that the six possible early pentacoordinate intermediates occupy the same side of the
topological representation. Consequently, a minimum of low energy permutations leads to the
last intermediate {13}, which affords the hydroxyarylphosphine borane 12 with retention of
configuration, by PꢀO bond cleavage (Scheme 4). The same stereochemistry is also obtained, if
we consider {14} (or {15}), as the last pentacoordinate intermediates with a PꢀO bond in the
axial position (Fig. 3).
On the contrary, a reverse stereochemistry for the rearrangement requires the formation of the
pentacoordinate enantiomer {13}, which is located on the other side of the topological
representation (Fig. 3). The interconversion could not occur easily, since the permutation of the
early pentacoordinate species toward {13} get through isomers as {45}. This last one is
energetically unfavorable due to the presence of a four-membered ring in the equatorial position,
and electron donor substituents in the apical position (Fig. 3).
We can see that the stereospecificity of the rearrangement arises from the impossibility of
making a four-membered ring pentacoordinate intermediate, which locks the racemization.
On the other hand, the borane could not be removed from the hydroxyaryl borane complexes
12 by exchange with dabco,13 because numerous by-products arise during the reaction. However,
we have succeeded in obtaining the free o-hydroxyarylphosphine 13e in 84% isolated yield, by
stirring the corresponding borane complex 12e in ethanol during 24 h at room temperature
(Scheme 3).
Finally, the 2-hydroxyarylphosphine boranes 12d, 12e have been used for the preparation of
a new class of phosphine-phosphinite ligand 14a,b (Scheme 5). Thus, when the rearrangement
products of 6d (or 6e) are trapped with chlorodiphenylphosphine Ph2PCl, then with borane, the
corresponding phosphine-phosphinites 14a (or 14b) are obtained in 54 or 25% yields, respec-
tively, as diborane complexes (Scheme 5). Decomplexation of borane complex 14a or 14b is
achieved by heating with dabco,27 giving the free phosphine-phosphinites 15a (R1=Me) (or 15b,
R1=o-An) in 80 (or 85%) isolated yields, respectively, with retention of the configuration at the
P-center (Scheme 5).
Scheme 5.
3. Conclusion
We have described herein, the first asymmetric synthesis of P-stereogenic 2-hydroxyaryl
phosphine ligands 13, using borane complexation methodology. This synthesis is based on two
key steps: firstly, the highly stereoselective preparation of a chlorophosphine borane which
allows the preparation of the arylphosphinite borane derivatives 6a–e; secondly, the intramolec-

D. Moulin et al. / Tetrahedron: Asymmetry 11 (2000) 3939–3956
3947
ular rearrangement of the complexes 6, affording the 2-hydroxyarylphosphine boranes 12a–e
without loss of enantiomeric purity. The o-anisyl-2-hydroxynaphthylphenylphosphine borane
12e has been decomplexed in EtOH, affording the first example of a P-stereogenic hydroxy-
arylphosphine ligand 13e. The interest of the hydroxyarylphosphine boranes 12 is also demon-
strated by the preparation of a new class of phosphine-phosphinite ligand 15, by trapping the
rearrangement products first with chlorodiphenylphosphine Ph2PCl, then with borane. The
corresponding phosphine-phosphinites 14a,b are then obtained and purified as diborane com-
plexes. When necessary, the decomplexation was achieved by heating with dabco, to afford the
free phosphine-phosphinite hybrid ligands 15a,b with retention of the configuration at the
P-center (yield up to 85%). Studies of these new classes of ligands in asymmetric catalysis are
under way in our laboratory.
4. Experimental section
4.1. General
All reactions were carried out under an argon or nitrogen atmosphere in dried glassware.
Solvents were dried and freshly distilled under a nitrogen atmosphere over sodium/benzo-
phenone for THF, toluene and benzene, P2O5 for CH2Cl2 and sodium ethoxide for EtOH.
Hexane, ethanol and isopropanol for HPLC were of chromatographic grade and used without
further purification. Methyllithium, t-butyllithium, chlorodiphenylphosphine, 2-bromoanisole,
2-bromotoluene, 1-bromo-2-naphthol, 2-bromophenol, BH3·S(CH3)2 and dabco were purchased
from Aldrich, Acros and Avocado. Commercially available 2-bromoanisole and 2-bromotoluene
were distilled before use. The toluenic HCl solution was obtained by bubbling gas, and the
titration of the resulting solution was realized with NaOH and phenolphthalein as indicator.
HPLC analyses were performed on a Gilson 305/306 chromatograph equipped with an UV 116
detector. The enantiomeric excess of the borane complexes 6, 11, 12 was determined using a
Chiralcel OK column (Daicel), with a hexane/iPrOH or EtOH mixture as the mobile phase (flow
rate 1 mL min−1), and the UV detection at u=254 nm. Flash chromatography was performed
on silica gel (60ACC, 35–70 mm; SDS) or neutral aluminum oxide (Carlo Erba; ref. 417241). All
NMR spectra data were obtained on Bruker DPX 250 spectrometer using TMS as internal
1
reference for H (250 MHz) and 13C NMR (62.9 MHz) and 85% phosphoric acid as external
reference for 31P NMR (101.3 MHz). Melting points were measured on a Bu¨chi melting point
apparatus and are uncorrected. Optical rotation values were determined at 20°C on a Perkin–
Elmer 241 polarimeter. Infrared spectra were recorded on a Bruker Equinox 55. Mass spectral
analyses were performed on a JEOL MS 700 at the Mass Spectroscopy Laboratories of ENS
Paris. The major peak m/z is mentioned with the intensity as a percentage of the base peak in
brackets. Elemental analyses were measured with a precision superior to 0.3% at the Microanal-
ysis Laboratories of P. & M. Curie University (Paris).
4.2. Synthesis of phosphinite boranes 6
4.2.1. Preparation of phenate reagents
In a two-necked flask equipped with a magnetic stirrer and an argon inlet, 288 mg of NaH (12
mmol) was added and washed several times with small amounts of pentane. 10 mL of dry THF

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D. Moulin et al. / Tetrahedron: Asymmetry 11 (2000) 3939–3956
was then added. The mixture was allowed to cool to 0°C, a solution of one equivalent (12 mmol)
of phenol in a minimum of dry THF was slowly added with a syringe and the reaction was
stirred during 2 hours at 0°C. Then, the phenate was used after solubilization of the possible
precipitate in a minimum of anhydrous THF.
4.2.2. Preparation of the phosphinite boranes
4.2.2.1. Typical procedure for the methylphosphinite boranes 6a, 6d. In a 250 mL three-necked
flask equipped with a magnetic stirrer and an argon inlet, 4 mmol of aminophosphine borane 9a
(or 9d) were dissolved in anhydrous toluene. Then, 8.4 mmol (2.1 equiv.) of a freshly titrated
toluene solution of dry HCl was added at room temperature under stirring (the final concentra-
tion of aminophosphine borane 9a or 9d, must be 20 mM). The reaction was stirred at room
temperature for one hour and the ephedrine hydrochloride precipitate was filtered off using a
Millipore 4 mm filter. The resulting solution of chlorophosphine borane 3a (or 3d) was then
collected in a 500 mL flask and cooled at −78°C. The flask was then put under an argon
atmosphere and 3 equivalents (12 mmol) of previously prepared phenate (Section 4.2.1) were
added to the solution. The resulting mixture was then stirred for 2 hours and warmed to room
temperature. The reaction was monitored by TLC over silica (toluene), and was hydrolyzed with
20 mL of water. The aqueous phase was extracted several times with CH2Cl2. The combined
organic layers were dried over MgSO4 and the solvent was removed. The residue was purified
by chromatography on silica gel using toluene as eluent yielding the phosphinite borane 6a, 6d
in 66–73% yield. When the separation between the phenol and the phosphinite borane is quite
difficult, a washing of the organic layer with a 0.5 M solution of KOH can be carried out
without alteration of the phosphinite borane.
The enantiomeric excess and the absolute configuration of the aryl phosphinite boranes 6a
have been determined by HPLC analysis on a Chiralcel OK Daicel column of the crude PAMP
borane 11, which results from their reaction at low temperature (<−50°C), with o-anisyllithium;
eluent: hexane/EtOH 70:30; (R) enantiomer tR=11.1 min; (S) enantiomer tR=21.4 min.
4.2.2.2. Typical procedure for the phosphinite boranes 6b, 6c, and 6e. In a 250 mL three-necked
flask equipped with a magnetic stirrer and an argon inlet, 24 mmol (6 equiv.) of freshly titrated
toluene solution of dry HCl were added to 4 mmol of aminophosphine borane 9b (or 9c). The
reaction was stirred at room temperature for 1 hour, and the ephedrine hydrochloride precipi-
tate was filtered off using a Millipore 4 mm filter. The resulting solution of chlorophosphine
borane 3b,c, was collected in a 250 mL flask and cooled at −78°C. The flask was then put under
an argon atmosphere and 28 mmol of phenate (7 equiv.), previously prepared according to the
procedure described in Section 4.2.1, was added. The resulting mixture was then stirred for 2
hours, warmed to room temperature and monitored by TLC over silica (toluene). After
hydrolysis with 20 mL of water, the mixture was extracted several times with CH2Cl2. The
combined organic layers were dried over MgSO4 and the solvent was removed. The residue was
purified by chromatography on silica gel using toluene as eluent, yielding the phosphinite borane
6b (or 6c, 6e) in 66–73% yield. The excess of phenol could be recovered from the residue by
extracting the organic layer with a 0.5 M solution of KOH, without alteration of the phosphite
borane.

D. Moulin et al. / Tetrahedron: Asymmetry 11 (2000) 3939–3956
3949
4.2.2.3. (S)-(−)-Methyl-(2-bromophenyl)phenylphosphinite borane 6a. Yield=71%; white oil;
Rf=0.75 (toluene); [h]2D0=−32.3 (c 1.7, CHCl3) for 71% e.e.; IR (neat, w cm−1): 3061–2920 (w),
1
2381 (m, BꢀH), 1578 (w), 1472 (s), 1438 (m), 1225 (s), 1119 (m), 1046 (w), 905 (s), 747 (m); H
2
NMR (CDCl3): l 0.2–1.60 (3H, br, BH3), 1.93 (3H, d, JHCP=8.8, CH3), 6.80–6.90 (1H, m, H
arom.), 7.07–7.20 (3H, m, H arom.), 7.40–7.55 (4H, m, H arom.), 7.80–7.95 (1H, m, H arom.);
1
13C NMR (CDCl3): l 16.9 (d, JCP=44.2, CH3), 115.3 (d, JCP=4.2, CBr), 121.7 (d, JCP=4.2, C
arom.), 125.6 (C arom.), 128.2 (C arom.), 128.8 (d, JCP=10.3, C arom.), 130.9 (d, JCP=12.1, C
arom.), 131.6 (C arom.), 132.6 (d, JCP=1.8, C arom.), 133.3 (C arom.), 149.5 (d, JCP=5.5, C
1
arom.); 31P NMR (CDCl3): l +121.2 (q, JPB=63.6); MS (DCI, CH4) m/z (relative intensity):
309 (M+−H; 80), 307 (M+−H; 100), 305 (M+−3H; 20), 227 (90), 217 (40), 173 (30), 141 (35), 125
(70), 107 (70); HRMS (DCI, CH4) calcd for C13H14BBrOP [M+−H]: 307.0061; found: 307.0060.
4.2.2.4. (S)-(−)-o-Anisyl-(2-bromophenyl)phenylphosphinite borane 6b. Yield=70%; white pow-
der; mp=122°C; Rf=0.6 (toluene); [h]D20=−12.5; (c 1, CHCl3) for 80% e.e.; IR (neat, w cm−1):
3071–2838 (w), 2403 (m, BꢀH), 2347 (m, BꢀH), 1588 (m), 1575 (m), 1474 (s), 1438 (s), 1430 (s),
1
1279 (m), 1267 (m), 1252 (m), 1229 (s), 1109 (m), 1045 (m), 1018 (m), 911 (s), 742 (s); H NMR
(CDCl3): l 0.2–1.60 (3H, br, BH3), 3.52 (3H, s, OCH3), 6.77–6.91 (2H, m, H arom.), 7.00–7.12
3
(3H, m, H arom.), 7.30–7.50 (5H, m, H arom.), 7.84–7.93 (2H, ddd, J=1.7, J=7.8, J HP=12.6,
3
H arom.), 8.03–8.11 (1H, ddd, J=1.7, J=7.6, JHP=11.4, H arom.); 13C NMR (CDCl3): l 55.4
(s, CH3O), 111.6 (d, JCP=5.0, C arom.), 115.4 (d, JCP=5.3, C arom.), 119.0 (d, JCP=60.4, C
arom.), 120.9 (d, JCP=11.4, C arom.), 121.4 (d, JCP=4.4, C arom.), 125.1 (C arom.), 128.0 (d,
JCP=7.4, C arom.), 128.3 (C arom.), 131.3 (d, JCP=12.1, C arom.), 131.6 (d, JCP=2.3, C arom.),
132.4 (C arom.), 133.4 (C arom.), 134.4 (d, JCP=12.1, C arom.), 134.6 (d, JCP=1.7, C arom.),
150.0 (d, JCP=3.9, C arom.), 160.9 (d, JCP=3.2, C arom.); 31P NMR (CDCl3): l +112.1 (q,
1JPB=73.3); MS (DCI, CH4) m/z (relative intensity): 401 (M+−H; 90), 399 (M+−H; 100), 389
(M++H−BH3; 30), 387 (M++H−BH3; 30), 281 (10), 279 (10), 215 (35); HRMS (DCI, CH4) calcd
for C19H18PBO2Br [M+−H]: 399.0321; found: 399.0303; anal. calcd for C19H19BBrO2P: C, 56.90;
H, 4.78; found: C, 56.91; H 4.78.
4.2.2.5. (R)-(+)-(2-Bromophenyl)phenyl-(o-tolyl)phosphinite borane 6c. Yield: 66%; uncrystal-
lized, white; Rf=0.75 (toluene); [h]D20=+21.7 (c 1.5, CHCl3); IR (neat, w cm−1): 2383–2338 (s,
BꢀH), 1622, 153, 1561, 1497, 1458, 1437, 1398, 1353, 1326, 1314, 1295, 1251, 1228, 1154, 1131,
1
1115, 1058, 994, 951, 905; H NMR (CDCl3): l 0.3–1.8 (br, 3H, BH3), 2.30 (3H, s, CH3),
6.80–7.20 (5H, m, H arom.), 7.30–7.60 (5H, m, H arom.), 7.70–7.90 (2H, m, H arom.), 8.10–8.30
(1H, m, H arom.); 13C NMR (CDCl3): l 21.4 (d, JCP=4.2, CH3), 115.3 (d, JCP=5.3, C arom.),
121.2 (d, JCP=4.7, C arom.), 125.4 (C arom.), 126.0 (d, JCP=12.4, C arom.), 128.7 (d,
JCP=10.8, C arom.), 131.2 (d, JCP=11.6,C arom.), 131.9 (C arom.), 132.9 (d, JCP=2.3, C
arom.), 133.6, 134.2 (d, JCP=17.5, C arom.), 142.0 (d, JCP=7, C arom.), 149.6 (d, JCP=3.6, C
1
arom.); 31P NMR (CDCl3): l +115.9 (q, JPB=68.3); MS (DCI, CH4) m/z (relative intensity):
383 (M+−H; 100 ), 373 (60), 371 (60), 295 (25), 293 (25), 281 (25), 279 (25), 199 (65); HRMS
(DCI, CH4) calcd for C19H18BBrOP, [M+−H]: 383.0372; found: 383.0307; calcd for C19H17OBrP,
[M++H−BH3]: 371.0200; found: 371.0213.
4.2.2.6. (S)-(−)-Methyl-(1-bromo-2-naphthyl)phenylphosphinite borane 6d. Yield=66%; white
powder; mp=67–68°C; Rf=0.7 (toluene); [h]2D0=−38.4 (c 2.0, CHCl3) for 91% e.e.; IR (neat, w
cm−1): 2410, 2383, 2338 (m, BꢀH), 1622 (w), 1593 (m), 1497 (m), 1458 (m), 1437 (m), 1353 (m),

3950
D. Moulin et al. / Tetrahedron: Asymmetry 11 (2000) 3939–3956
1251 (m), 1228 (s), 1115 (m), 1058 (m), 994 (s), 951 (s), 905 (s); 1H NMR (CDCl3): l 0.3–1.8 (br,
2
3H, BH3), 1.99 (3H, d, JHP=8.8, PCH3), 7.10–7.20 (1H, m, H arom.), 7.25–7.63 (7H, m, H
arom.), 7.9–8.0 (2H, m, H arom.), 8.1–8.2 (1H, m, H arom.); 13C NMR (CDCl3): l 17.1 (d,
1JCP=44, CH3), 113.8 (d, JCP=5.4, C arom.), 120.7 (d, JCP=3.7, C arom.), 126.3 (d, JCP=64,
C arom.), 127.9 (d, JCP=19.6, C arom.), 128.5 (C arom.), 128.8 (d, JCP=10.6, C arom.), 130.9
(C arom.), 131.0 (d, JCP=14.8, C arom.), 131.4 (C arom.), 131.8 (C arom.), 132.7 (d, JCP=2.2,
1
C arom.), 147.7 (d, JCP=5.6, C arom.); 31P NMR (CDCl3): l +121.3 (q, JPB=68.3); MS (DCI,
+
+
NH3) m/z (relative intensity): 378 (M+NH4 ; 5), 376 (M+NH4 ; 5), 158 (30), 141 (10), 125 (100);
HRMS (DCI, CH4) calcd for C17H16BBrOP [M+−H]: 357.0218; found: 357.0219; anal. calcd for
C17H17BBrOP (359.0): C, 56.88; H, 4.77; found C, 56.74; H 4.81.
Crystal data for compound 6d: formula C17H17Br1P1O1B1; F.W. 359.01; crystal system:
,
,
,
orthorhombic; a (A)=6.593(2); b (A)=6.336(3); c (A)=34.912(9); h (°)=90; i (°)=90, k
3
,
(°)=90; V (A )=1688.5(9); Z=4; space group: P212121; crystal shape: parallelepiped; linear
absorption coefficient v (cm−1): 24.98; density z (g cm3)=1.41; diffractometer: CAD4-Enraf
,
Nonius; radiation: Mo Ka (u=0.71069 A); scan type: ꢀ/2q; scan range (°): 0.8+0.345 tgq; q
limits (°): 1–30; temp.: rt; octants collected: 0.9; 0.10; 0.49; Nb of data collected: 2883; Nb of
unique data used for refinement: 999 (Fo)2>3|(Fo)2; decay of standard reflections%: 3.2;
2 1/2
R=SIFo−IFcII/SFo: 0.0686; R*=[Sw(Fo−IFcI)2/SwFo ] =0.0782; secondary extinction coeffi-
w
−3
−3
,
,
cient: 980.8; goodness of fit: 1.12; Nb of variables: 192; Dzmin (e A ): −0.45; Dzmax (e A ): 0.79.
4.2.2.7. (R)-(+)-o-Anisyl-(1-bromo-2-naphthyl)phenyl phosphinite borane 6e. Yield=73%; yellow
solid; mp=102°C; Rf=0.67 (toluene); [h]2D0=+40.8 (c 1, CHCl3); IR (w cm−1): 3066 (w), 2923 (s),
2403 (s, BꢀH), 1623 (m), 1588 (s), 1576 (s), 1501 (m), 1477 (s), 1457 (s), 1437 (s), 1354 (m), 1280
(s), 1253 (s), 1228 (s), 1110 (s), 1083 (m), 1063 (m), 1017 (m), 994 (s), 946 (m), 821 (s), 805 (s),
1
793 (s), 753 (s), 744 (s), 69 (s); H NMR (CDCl3): l 0.2–1.8 (br, 3H, BH3), 3.37 (3H, s, OCH3),
6.85–6.90 (1H, dd, H arom.), 7.09–7.77 (10H, m, H arom.), 7.96–8.04 (2H, m, H arom.),
8.15–8.24 (2H, m, H arom.); 13C NMR (CDCl3): l 55.3 (s, OꢀCH3), 111.7 (d, JCP=4.9, C
arom.), 113.7 (d, JCP=5.5, C arom.), 119.3 (d, JCP=60.6, C arom.) 120.7 (d, JCP=4, C arom.),
121.0 (d, JCP=11.4, C arom.), 126.2 (d, JCP=81.1, C arom.), 127.9 (d, JCP=26, C arom.),
128.1–128.5 (C arom.), 128.7 (d, JCP=92.8, C arom.), 131.3 (d, JCP=12.1, C arom.), 131.4 (d,
JCP=19, C arom.), 131.7 (d, JCP=17.8, C arom.), 134.3 (d, JCP=12, C arom.), 134.7 (d,
JCP=1.6, C arom.), 148.3 (d, JCP=4.1, C arom.), 161.0 (d, JCP=3.2, C arom.); 31P NMR
1
(CDCl3): l +112.6 (q, JPB=51); MS (DCI, CH4) m/z (relative intensity): 439 (M+; 55), 437 (M+;
55), 359 (20), 357 (20), 331 (15), 329 (15), 217 (80), 215 (100), 172 (20), 154 (50), 144 (50);
HRMS (DCI, CH4) calcd for C23H19BrO2P [M++H−BH3]: 439.0286; found: 439.0293.
4.2.3. Preparation of the hydroxyphosphine boranes 12a–e by rearrangement of the
arylphosphinite boranes 6a–e
In a 100 mL three-necked flask equipped with a magnetic stirrer and an argon inlet, 3 mmol
of phosphinite borane 6a–e was dissolved in 30 mL of anhydrous THF. The mixture was then
cooled at −78°C and 2.7 equiv. of t-BuLi (1.5 M in pentane) was slowly added. The resulting
mixture was then stirred for 1 hour and warmed to 0°C. The reaction was monitored by TLC
over silica (toluene/petroleum ether 7:3), and finally was hydrolyzed with 3 mL of water. The
THF was removed under reduced pressure and the aqueous layer was extracted several times
with CH2Cl2. The combined organic phases were dried over MgSO4 and the solvent was
removed. The residue was purified by chromatography on silica gel, using a mixture of

D. Moulin et al. / Tetrahedron: Asymmetry 11 (2000) 3939–3956
3951
toluene/petroleum ether as eluent, yielding the hydroxyphosphine boranes 12a–d in 60–90%
yield.
4.2.3.1. (S)-(−)-Methyl-(2-hydroxyphenyl)phenylphosphine borane 12a. Yield=75%; white solid;
mp=49–50°C; Rf=0.3 (toluene); [h]D20=−16.1 (c 1.8, CHCl3) for e.e.=72%; IR (neat, w cm−1):
3415 (s, OꢀH), 3078 (w), 2922 (s), 2852 (s), 2374 (m, BꢀH), 2347 (s, BꢀH), 1595 (s), 1581 (m),
1
1444 (s), 1337 (m), 1290 (m), 1195 (m), 1076 (s), 896 (s), 836 (m), 757 (s); H NMR (CDCl3): l
2
0.3–1.9 (3H, br, BH3), 1.86 (3H, d, JHP=10.4, CH3), 6.80–7.00 (2H, m, H arom.), 7.30–7.55
1
(5H, m, H arom.); 7.60–7.85 (2H, m, H arom.); 13C NMR (CDCl3): l 11.8 (d, JCP=43, CH3),
112.9 (d, JCP=56.6, C arom.), 117.9 (d, JCP=5.7, C arom.), 120.9 (d, JCP=8.5, C arom.), 128.8
(d, JCP=10.4, C arom.), 130.1 (d, JCP=60, C arom.), 131.1 (d, JCP=9.7, C arom.), 133.0 (d,
JCP=5.4, C arom.), 133.8 (d, JCP=2.1, C arom.), 159.9 (d, JCP=6.8, C arom.); 31P NMR
1
(CDCl3): l +5.0 (q, JPB=68); MS (EI) m/z (relative intensity): 227 (M+−3H; 100), 216
(M+−BH3; 70), 215 (25), 183 (55), 169 (10), 149 (15), 121 (20), 107 (30), 91 (15), 77 (30), 69 (10),
51 (15); HRMS (EI) calcd for C13H13OP, [M+−BH3]: 216.0704; found: 216.0707.
The enantiomeric excess of the o-hydroxyphenylphosphine borane 12a was determined by
HPLC on a Chiralcel OK Daicel column, with hexane/EtOH 75:25 as eluent (flow rate 1 mL
min−1; major (S)-enantiomer tR=15.45 min; minor (R)-enantiomer tR=8.87 min).
4.2.3.2. (S)-(+)-o-Anisyl-(2-hydroxyphenyl)phenylphosphine borane 12b. Yield=87%; white pow-
der; mp=103–104°C; Rf=0.35 (toluene); [h]2D0=+3.3 (c 0.5, CHCl3) for e.e.=80%; IR (neat,
w cm−1): 3304 (s, OꢀH), 3058 (w), 2933 (m), 2837 (w), 2396 (m, BꢀH), 2348 (m, BꢀH), 1615 (s),
1601 (m), 1588 (s), 1570 (m), 1564 (m), 1512 (s), 1477 (s), 1461 (s), 1436 (s), 1428 (s), 1396 (s),
1280 (s), 1265 (m), 1250 (s), 1221(s), 1209 (m), 1163 (m), 1132 (s), 1076 (m), 1060 (s), 1017 (s),
821 (s), 800 (m), 777 (m), 750 (s), 704 (m); 1H NMR (CDCl3): l 0.5–1.8 (3H, br, BH3), 3.56 (3H,
s, OCH3), 6.70–7.05 (5H, m, H arom.), 7.20–7.70 (8H, m, H arom.); 13C NMR (CDCl3): l 55.6
(d, JCP=4.4, OCH3), 111.9 (d, JCP=4.8, C arom.), 112.1 (d, JCP=60, C arom.), 115.6 (d,
JCP=60.7, C arom.), 118.2 (d, JCP=6, C arom.), 120.3 (d, JCP=8, C arom.), 121.3 (d, JCP=11.1,
C arom.), 128.1 (d, JCP=64.9, C arom.), 128.6 (d, JCP=10.6, C arom.), 131.0 (d, JCP=2.5, C
arom.), 132.6 (d, JCP=9.9, C arom.), 133.4 (d, JCP=2, C arom.), 134.2 (C arom.), 135.2 (d,
JCP=2.8, C arom.), 160.1 (d, JCP=8.9, C arom.), 161.4 (C arom.); 31P NMR (CDCl3): l +11.9
(q, 1JPB=69.9); MS (EI) m/z (relative intensity): 319 (M+−3H; 90), 317 (M+−BH3; 100), 291 (15),
277 (15), 199 (50), 183 (75), 152 (20), 107 (20), 91 (20), 77 (20), 63 (15); HRMS (EI) calcd for
C19H17O2P, [M+−BH3]: 308.0966; found: 308.0969.
The enantiomeric excess of the o-hydroxyphenylphosphine borane 12b was determined by
derivatization with (S)-(−)-O-acetyllactyl chloride. This derivative was prepared by trapping the
rearrangement product with (S)-O-acetyllactyl chloride, before hydrolysis of the reaction
1
mixture: Rf=0.55 (toluene); H NMR (CDCl3): l 0.5–1.8 (3H, br, BH3), 0.95 (3H, d, JHH=7,
CH3), 2.0 (3H, s, CH3CO), 3.4 (3H, s, CH3O), 4.8 (1H, q, JHH=7, CH), 6.8–7.9 (13H, m, H
arom.); 31P NMR (CDCl3): l +17.6; 13C NMR (CDCl3): major stereoisomer l 15.7 (CH3CH),
20.6 (CH3CO), 55.0, 68.5, 111.5, 116.3 (d), 121.0–133.9 (C arom.), 151.8 (d, JCP=3.5, C arom.),
161.0, 168.3, 170.2; minor stereoisomer l 16.7, 20.6, 55.4, 68.1, 111.5, 116.3 (d), 121.0–133.9,
151.0 (d), 160.9, 168.2, 170.3.
The diastereoisomeric ratio of the (S)-O-acetyllactyl derivative was determined by HPLC
analysis on a Chiralcel OK Daicel column, with hexane/i-PrOH 98:2 as eluent (flow rate 1 mL
min−1; major stereoisomer tR=17.8 min; minor stereoisomer tR=8.9 min). The minor stereoiso-

3952
D. Moulin et al. / Tetrahedron: Asymmetry 11 (2000) 3939–3956
mer has been identified by comparison with the corresponding derivative of (S)-o-anisyl-(2-
hydroxyphenyl)phenylphosphine borane 12b, prepared from (−)-ephedrine.
4.2.3.3. (R)-2-Hydroxyphenyl-phenyl(o-tolyl)phosphine borane 12c. Yield=60%; white powder;
Rf=0.35 (toluene); IR (w cm−1): 3367 (s, OꢀH), 3062–2923 (m), 2408 (m, BꢀH), 2379 (m, BꢀH),
2296 (m, BꢀH), 1601 (m), 1588 (m), 1575 (s), 1473 (s), 1453 (s), 1435 (s), 1299 (m), 1279 (m),
1
1255 (m), 1214 (m), 1128 (m), 1067 (m), 742 (m), 692 (m); H NMR (CDCl3): l 0.5–1.8 (3H, br,
3
BH3), 2.26 (3H, s, CH3), 6.70–7.60 (13H, m, H arom.); 13C NMR (CDCl3): l 22.5 (d, JCP=5,
CH3), 111.8 (d, JCP=58.4, C arom.), 118.7 (d, JCP=6, C arom.), 120.7 (d, JCP=7.8, C arom.),
125.8–133.9 (C arom.), 142.9 (d, JCP=11.6, C arom.), 160.5 (d, JCP=9.1, C arom.); 31P NMR
1
(CDCl3): l +14.2 (q, JPB=67); MS (DCI, CH4) m/z (relative intensity): 305 (M+−H; 100), 293
(100), 215 (15), 201 (15); HRMS (DCI, CH4): calcd for C19H19BOP, [M+−H]: 305.1267; found
m/z: 305.1270.
4.2.3.4. (S)-(+)-Methyl-1-(2-hydroxynaphthyl)phenylphosphine borane 12d. Yield=96%; white
powder; mp=125°C; Rf=0.5 (toluene); [h]2D0=+1.47 (c 0.7, CHCl3) for e.e.=91%; IR (neat, w
cm−1): 3323 (s, OꢀH), 2412 (s, BꢀH), 2382 (s, BꢀH), 1616 (m), 1603 (m), 1568 (m), 1512 (m),
1
1463 (m), 1436 (m), 1397 (m), 1266 (m), 1219 (s), 1131 (s), 1107, 1065 (s); H NMR (CDCl3):
2
l 0.3–2.0 (3H, br, BH3), 2.08 (3H, d, JHP=10.2, PCH3), 7.1–7.5 (9H, m, H arom.), 7.70 (1H,
d, JHH=9, H arom.), 7.87 (1H, d, JHH=9, H arom.), 9.12 (1H, s, OH); 13C NMR (CDCl3): l
1
12.4 (d, JCP=43.4, CH3), 98.8 (d, JCP=55.7, C arom.), 120.3 (d, JCP=7.5), 123.5 (C arom.),
125.1 (d, JCP=5.2, C arom.), 127.1 (C arom.), 129.0–130.5 (C arom.), 131.7 (d, JCP=62.6, C
arom.), 133.5 (C arom.), 135.9 (C arom.), 163.4 (d, JCP=11.7, C arom.); 31P NMR (CDCl3): l
1
−0.46 (q, JPB=64); MS (EI) m/z (relative intensity): 277 (M+−3H; 75), 266 (M+−BH3; 50), 233
(20), 83 (100); HRMS (DCI, CH4) calcd for C17H17OPB, [M+-H]: 279.1113; found: 279.1121;
anal. calcd. for C17H18OPB (280.1134): C, 72.89; H, 6.48; found C, 72.76; H, 6.62.
The enantiomeric excess of the o-hydroxyphenylphosphine borane 12d was determined by
HPLC on a Chiralcel OK Daicel column, with hexane/EtOH 75:25 as eluent (flow rate 1 mL
min−1; minor enantiomer tR=10.5 min; major enantiomer tR=20.2 min).
4.2.3.5. (R)-(+)-o-Anisyl-1-(2-hydroxynaphthyl)phenylphosphine borane 12e. Yield=48%; white
powder; mp=118–120°C; Rf=0.26 (toluene/cyclohexane, 1:1); [h]2D0=+94.5 (c 1, CHCl3); IR (w
cm−1): 3304 (s, OꢀH), 3059–2837 (w), 2396 (m, BꢀH), 2350 (m, BꢀH), 1615 (m), 1601 (m), 1588
(m), 1564 (m), 1512 (m), 1476 (s), 1462 (s), 1436 (s), 1428 (s), 1396 (m), 1280 (m), 1265 (m), 1250
(s), 1221 (s), 1163 (m), 1132 (m), 1060 (m), 1016 (s), 821 (s), 777 (m), 751 (s); 1H NMR (CDCl3):
l 0.3–1.9 (3H, br, BH3), 3.50 (3H, s, OCH3), 6.78–7.86 (1H, m, H arom.), 6.93–7.07 (2H, m, H
arom.), 7.10–7.30 (2H, m, H arom.), 7.35–7.58 (6H, m, H arom.), 7.60–7.78 (3H, m, H arom.),
7.90 (1H, d, JHH=9, H arom.), 9.30 (1H, s, OH); 13C NMR (CDCl3): l 55.2 (s, OCH3), 99.1 (d,
JCP=58.2, C arom.), 111.8 (d, JCP=5.3, C arom.), 117.4 (d, JCP=62.4, C arom.), 119.9 (d,
JCP=7.7, C arom.), 120.5 (d, JCP=9.8, C arom.), 122.7 (C arom.), 125.5 (d, JCP=5.3, C arom.),
125.8 (C arom.), 126.6 (C arom.), 127.7 (C arom.), 128.0 (d, JCP=10.6, C arom.), 128.5 (C
arom.), 128.8 (d, JCP=5.2, C arom.), 130.3 (d, JCP=2.4, C arom.), 131.7 (d, JCP=5.5, C arom.),
132.5 (C arom.), 132.8 (d, JCP=9.4, C arom.), 133.7 (s, C arom.), 134.7 (d, JCP=1.7, C arom.),
160.5 (d, JCP=5, C arom.), 162.4 (d, JCP=11.9, C arom.); 31P NMR (CDCl3): l +6.07 (br); MS
(EI) m/z (relative intensity): 369 (M+−3H; 100), 358 (M+−BH3; 90), 327 (20), 249 (55), 233 (45),
202 (45), 183 (30), 157 (35), 127 (25), 91 (25), 84 (70); HRMS (EI): calcd for C23H19O2PB,
[M-3H]: 369.1220; found m/z: 369.1227.

D. Moulin et al. / Tetrahedron: Asymmetry 11 (2000) 3939–3956
3953
The enantiomeric excess of the o-hydroxynapththylphosphine borane 12e was determined by
HPLC on a Chiralcel OK Daicel column, with hexane/EtOH 90:10 as eluent (flow rate 1 mL
min−1; minor enantiomer tR=36.6 min; major enantiomer tR=48.9 min).
4.2.4. Typical procedure for the preparation of phosphine-phosphinite diborane ligands 14
In a 100 mL two-necked flask equipped with a magnetic stirrer and an argon inlet, 2.8 mmol
of phosphinite borane 6d (or 6e) was dissolved in 28 mL of anhydrous toluene. The mixture was
then cooled at −78°C and 2.7 equivalents of t-BuLi (7.56 mmol, 1.5 M in pentane) were slowly
added. The resulting mixture was then stirred for 1 hour, warmed to 0°C, and the reaction was
monitored by TLC over silica (toluene). Then, 2.7 equivalents of chlorodiphenylphosphine (7.56
mmol, 1.67 g, 1.36 mL) were slowly added at 0°C, and the resulting mixture was stirred 1 hour
and warmed to room temperature. After addition of 10 equivalents of borane dimethylsulfide
(27.8 mmol, 2.78 mL), the mixture was stirred for 1 hour, and the THF was removed under
reduced pressure. The residue was hydrolyzed with 10 mL of water, and the mixture extracted
several times with CH2Cl2. The combined organic phases were dried over MgSO4 and the
solvent was removed under vacuum. The residue was purified by chromatography on silica gel
using a mixture of toluene/petroleum ether 1:1 as eluent, yielding the phosphine-phosphinite
diborane ligand 14a (or 14b) in 54 (or 25%) isolated yield.
4.2.4.1. (S)-(+)-Methyl-1-[2-(diphenylphosphinito borane)naphthyl]phenylphosphine borane 14a.
Yield=54%; white powder; mp=154–156°C; Rf=0.5 (toluene); [h]2D0= +17.6 (c 0.96, CHCl3);
IR (neat, w cm−1): 3434 (m, OꢀH), 3054–2800 (w), 2395 (s, BꢀH), 2340 (s, BꢀH), 1590 (m), 1507
(m), 1460 (s), 1436 (s), 1319 (m), 1221 (s), 1213 (s), 1150 (m), 1114 (m), 1061 (s), 1009 (s), 965
1
(s), 820 (s), 811 (s), 738 (s), 694 (s); H NMR (CDCl3): l 0.3–2.0 (6H, br, BH3), 1.64 (3H, d,
2JHP=10.1, CH3), 7.00–7.90 (20H, m, H arom.), 8.75 (1H, d, J=12.1, H arom.); 13C NMR
1
(CDCl3): l 16.0 (d, JCP=42.2, CH3), 125.4–134 (C arom.); 31P NMR (CDCl3): l +8.9 (br,
PhMeP), +111.0 (br, Ph2PO); MS (DCI, CH4) m/z (relative intensity): 477 (M+−H; 5), 465 (20),
451 (20), 339 (25), 294 (35), 279 (90), 277 (100), 267 (90), 216 (55), 187 (90), 125 (30), 109 (50);
HRMS (DCI, CH4): calcd for C29H29OP2B2, [M+−H]: 477.1880; found: 477.1890; Anal. calcd for
C29H30OP2B2 (478.125): C, 72.85; H, 6.32; found C, 72.85; H, 6.33.
4.2.4.2. (R)-(+)-o-Anisyl-1-[2-(diphenylphosphinito borane)naphthyl]phenylphosphine borane 14b.
Yield=25%; white powder; mp=165–168°C; Rf=0.26 (toluene); [h]2D0=+72.9 (c 1, CHCl3); IR
(neat, w cm−1): 3050–2850 (w), 2440–2330 (s), 1625 (w), 1590 (s), 1508 (s), 1474 (s), 1462 (s), 1437
(s), 1435 (m), 1429 (m), 1320 (w), 1275 (m), 1245 (m), 1215 (s), 1210 (s), 1110 (m), 1060 (m),
1
1000 (s), 960 (s), 808 (s), 778 (m), 757 (m), 700 (s); H NMR (CDCl3): l 0.3–2.0 (6H, br, BH3),
3.22 (3H, s, OCH3), 6.40–6.65 (m, 2H, H arom.), 7.05–7.90 (22H, m, H arom.), 7.91 (1H, d,
J=8.8, H arom.); 13C NMR (CDCl3): l 55.0 (s, OCH3), 110.7 (d, JCP=4.8, C arom.),
118.3–120.2 (C arom.), 121.0 (d, JCP=13.0, C arom.), 124.7 (C arom.), 126.2 (C arom.), 126.5
(d, JCP=6.7, C arom.), 128.1 (d, JCP=11.0, C arom.), 128.4–133.0 (C arom.), 153.7 (d, JCP=4.4,
C arom.), 159.9 (C arom.); 31P NMR (CDCl3): l +12.8 (br, AnPhPꢀAr), +106.9 (br, Ph2PꢀO);
MS (DCI, CH4) m/z (relative intensity): 555 (M+−BH3−H; 55), 443 (M+−2BH3+H; 100), 465
(10), 436 (10), 422 (10), 369 (45), 359 (60), 340 (25), 215 (20), 187 (40), 109 (20); HRMS (DCI,
CH4): calcd for C35H30O2P2B2, [M+−BH3−H]: 555.1820; found: 555.1819; calcd for C35H29O2P2,
[M+−2BH3+H]: 543.1643; found: 543.1648.

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D. Moulin et al. / Tetrahedron: Asymmetry 11 (2000) 3939–3956
4.2.5. Typical procedure for the decomplexation of phosphine-phosphinite diboranes 14a,b
In a three-necked flask equipped with a reflux condenser, a magnetic stirrer and an argon
inlet, 1 equivalent of phosphine-phosphinite diborane ligand 14a,b (0.075 mmol) was charged.
Diazabicyclooctane (4 equivalents, 0.3 mmol) was added, the flask was purged with three cycles
of argon and 3 mL of dry toluene were added. The mixture was heated at 60°C for 15 h. The
crude product was rapidly filtered off on a neutral alumina column (15 cm height, 2 cm
diameter) using toluene/AcOEt, 9:1, as eluent. Phosphine-phosphinite 15a,b was recovered in
80–84% isolated yields.
4.2.5.1. (S)-(−)-Methyl-1-[2-(diphenylphosphinito)naphthyl]phenylphosphine 15a. Yield=80%;
uncrystallized; [h]2D0= −4.0 (c 0.25, CHCl3); IR (neat, w cm−1): 3050 (w), 2970–2850 (w), 1457
1
2
(w), 1436 (w), 1261 (s), 1096 (s), 1026 (s), 806 (s); H NMR (CDCl3): l 1.50 (3H, d, JHP=4.3,
CH3), 6.90–7.40 (18H, m, H arom.), 7.75 (2H, m, H arom.), 8.85 (1H, m, H arom.); 13C NMR
(CDCl3): l 9.1 (d, 1JCP=13.5, CH3), 117.9 (d, JCP=23.1, C arom.), 124.0 (d, JCP=2.1, C arom.),
126.2 (C arom.), 126.5–127.2 (C arom.), 127.9–132.4 (C arom.), 138.7–139.4 (C arom.), 141.9 (d,
JCP=10.9, C arom.), 158.5 (d, JCP=9.5, C arom.); 31P NMR (CDCl3): l −44.3 (s, MePhPꢀC),
+111.7 (s, Ph2PꢀO); MS (EI) m/z (relative intensity): 450 (M+, 20), 465 (M+−CH3, 100), 373 (55),
358 (10), 281 (20), 265 (30), 249 (15), 201 (30), 183 (40); HRMS (EI): calcd for C29H24OP2 [M]:
450.1302; found: 450.1300.
4.2.5.2. (R)-(−)-o-Anisyl-1-[2-(diphenylphosphinito)naphthyl]phenylphosphine 15b. Yield=84%;
uncrystallized; [h]2D0=−6.3 (c 0.26, CHCl3); IR (neat, w cm−1): 3050–2850 (w), 1264 (s), 1095 (s),
1
1022 (s), 809 (s), 696 (m); H NMR (CDCl3): l 3.53 (3H, s, OCH3), 6.50–7.75 (m, 24H, H
arom.), 8.75 (1H, m, H arom.); 13C NMR (CDCl3): l 55.5 (s, OCH3), 110.2 (C arom.), 117.9 (d,
JCP=23.9, C arom.), 121.0 (C arom.), 123.9–132.8 (C arom.), 161.0 (d, JCP=16.6, C arom.); 31P
NMR (CDCl3): l −33.0 (d, JPP=3.1, AnPhP), +113.3 (Ph2PO); MS (EI) m/z (relative intensity):
542 (M+; 40), 465 (100), 435 (30), 358 (40), 357 (20), 327 (10), 249 (35), 201 (40), 183 (40), 169
(15), 108 (10), 84 (20), 77 (10); HRMS (DCI): calcd for C35H28O2P2, [M]: 542.1565; found:
542.1561.
4.2.6. (R)-(−)-o-Anisyl-1-(2-hydroxynaphtyl)phenylphosphine 13e by decomplexation of 12e
In a two-necked flask equipped with a reflux condenser, a magnetic stirrer and an argon inlet,
1 equivalent (0.075 mmol) of hydroxyphosphine borane ligand 6e was charged. The flask was
purged with three cycles of argon and 3 mL of dry ethanol were added. The mixture was stirred
at room temperature for 24 h. The crude product was rapidly filtered off on silica column using
toluene/AcOEt, 9:1, as eluent to yield the hydroxyphosphine 13e.
Yield=80%; white solid; [h]2D0=−1.7 (c 0.9, CHCl3); IR (neat, w cm−1): 3446 (m), 3301 (m),
3064–2833 (m), 1616 (w), 1567 (w), 1464 (m), 1457 (s), 1429 (s), 1261 (m), 1241 (m), 1127 (m),
1
1100 (m), 1067 (m), 1019 (s), 822 (m), 801 (m), 742 (m); H NMR (CDCl3): l 3.70 (3H, s,
OCH3), 6.70–8.10 (m, 15H, H arom.); 13C NMR (CDCl3): l 55.7 (s, OCH3), 110.6 (d, JCP=1.9,
C arom.), 118.0 (d, JCP=1.8, C arom.), 121.1 (d, JCP=6.2, C arom.), 121.3 (d, JCP=1.8, C
arom.), 123.2 (C arom.), 126.4–126.8 (C arom.), 128.1 (C arom.), 128.6 (d, JCP=6.3, C arom.),
128.7 (C arom.), 129.6 (d, JCP=4, C arom.), 130.8 (C arom.), 131.0 (d, JCP=17, C arom.), 132.7
(d, JCP=3, C arom.), 133.6 (C arom.), 133.7 (d, JCP=6, C arom.), 136.5 (d, JCP=10, C arom.),
160.4 (d, JCP=13.0, C arom.), 161.2 (d, JCP=15.0, C arom.); 31P NMR (CDCl3): l −45.9; MS
(EI) m/z (relative intensity): 358 (M+; 100), 327 (20), 249 (60), 220 (20), 202 (40), 183 (20), 157

D. Moulin et al. / Tetrahedron: Asymmetry 11 (2000) 3939–3956
3955
(25), 127 (20), 115 (25), 77 (10); HRMS (EI): calcd for C23H19O2P, [M]: 358.1123; found:
358.1132.
Acknowledgements
We thank Mrs N. Morin for her help in mass analysis, the Ministry of Research and the
CNRS for financial support to our group.
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