Totally diastereoselective synthesis of new P-chirogenic o-trimethylsiloxyaryl diazaphospholidines and o-hydroxyaryl diazaphospholidine-borane complexes

Article abstract of DOI:10.1016/S0022-328X(01)01314-6

The totally diastereoselective synthesis of several P(III)-chirogenic o-trimethylsiloxyaryl diazaphospholidines 4 was achieved by exchange reactions in refluxing toluene from the key intermediates, o-trimethylsiloxyaryl bis(dimethylamino) phosphines 2, and various chiral diamines 3. In the case of the use of a non-C₂-symmetric chiral auxiliary such as (S)-2-anilinomethylpyrrolidine (3a), compounds 4a-g, containing a stereogenic phosphorus atom, were obtained in diastereomerically pure form as the thermodynamic anti-diastereomers. Complexation of the diazaphospholidines 4 by borane-dimethylsulfide and subsequent methanolysis of the siloxy ether function lead to the formation of the desired o-hydroxyaryl diazaphospholidine-borane complexes 5 in good yields, ranging from 71 to 86%.

Full text of DOI:10.1016/S0022-328X(01)01314-6

Journal of Organometallic Chemistry 643–644 (2002) 237–246
www.elsevier.com/locate/jorganchem
Totally diastereoselective synthesis of new P-chirogenic
o-trimethylsiloxyaryl diazaphospholidines and o-hydroxyaryl
diazaphospholidine–borane complexes
Christian J. Ngono, Thierry Constantieux, Ge´rard Buono *
Laboratoire de Synthe`se Asyme´trique, UMR 6516 CNRS ‘Synthe`se, Catalyse, Chiralite´’, Uni6ersite´ d’Aix-Marseille III,
Faculte´ des Sciences et Techniques de St Je´roˆme, ENSSPICAM, A6enue Escadrille Normandie Nie´men, 13397 Marseille Cedex 20, France
Received 29 June 2001; accepted 26 September 2001
Dedicated to Professor Franc¸ois Mathey on the occasion of his 60th birthday
Abstract
The totally diastereoselective synthesis of several P(III)-chirogenic o-trimethylsiloxyaryl diazaphospholidines 4 was achieved by
exchange reactions in refluxing toluene from the key intermediates, o-trimethylsiloxyaryl bis(dimethylamino) phosphines 2, and
various chiral diamines 3. In the case of the use of a non-C2-symmetric chiral auxiliary such as (S)-2-anilinomethylpyrrolidine
(3a), compounds 4a–g, containing a stereogenic phosphorus atom, were obtained in diastereomerically pure form as the
thermodynamic anti-diastereomers. Complexation of the diazaphospholidines 4 by borane-dimethylsulfide and subsequent
methanolysis of the siloxy ether function lead to the formation of the desired o-hydroxyaryl diazaphospholidine-borane complexes
5 in good yields, ranging from 71 to 86%. © 2002 Elsevier Science B.V. All rights reserved.
Keywords: Hemilabile ligands; Bidentate PꢀO ligands; P-stereogenic o-phosphinophenols; Phosphine–borane complexes; Intramolecular 1,3-car-
banionic rearrangement
tronic and steric properties may be modulated by vary-
ing substituents at the phosphorus atom and on the
1. Introduction
aromatic ring. Until now, only few synthetic ap-
proaches to o-phosphinophenols have been developed.
These compounds can be obtained by deprotection of
suitable o-phosphinoaryl ethers or trimethylsilyl ethers,
which in turn were synthesized from o-lithiated aryl
ethers and diphenylchlorophosphine [10a,10b,11]. They
can also be prepared via intramolecular 1,3-carbanionic
rearrangement of o-metallated phenoxyphosphorus
compounds [12]. Another general way consists in trap-
Multidentate chelate ligands, offering a selection of
hard-soft donor atoms that are capable of adapting to
the character of the metal center, are increasingly im-
portant in organometallic chemistry [1]. In this area,
hemilabile PꢀO ligands have been extensively studied in
coordination chemistry [2], and have found applications
in important catalytic processes such as oligomerization
of olefins [3,4], carbonylation [5] and carbon dioxide
activation [6], hydrogenation [7] or dehydrogenation
[8]. Among them, o-phosphinophenols are ambident
molecules which possess two different nucleophilic sites,
a hard oxygen atom and a soft phosphorus atom. They
may undergo reactions either at oxygen, phosphorus or
both nucleophilic sites and, thus, are of interest in
catalysis [9] and in complex chemistry [10]. Their elec-
ping of
a C,O-phenol dilithium reagent with a
chlorophosphine [13]. Recently, the first asymmetric
synthesis of P-stereogenic 2-hydroxyarylphosphine lig-
ands, using borane complexation methodology, and
based on an intramolecular ortho Fries-like rearrange-
ment mediated in basic conditions of enantioenriched
o-bromoarylphosphinite boranes, was reported [14].
Nevertheless, only one o-hydroxyaryl phosphine borane
complex could be obtained in pure enantiomeric form
by this method. In this paper, we wish to report a
* Corresponding author. Tel.: +33-491-288681; fax: +33-491-
282742.
E-mail address: buono@spi-chim.u-3mrs.fr (G. Buono).
0022-328X/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)01314-6

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Scheme 1. General procedure for the synthesis of the o-hydroxyaryl diazaphospholidine–borane complexes 5.
Scheme 2. Synthesis of the key intermediates, o-trimethylsiloxyaryl bis(dimethylamino) phosphines 2.
totally diastereoselective synthesis of new P(III)-chiro-
genic o-trimethylsiloxyaryl diazaphospholidines and o-
lithium lead to the formation of the corresponding
C,O-dilithio reagents, which can react with one equiva-
lent of chlorobis(dimethylamino)phosphine, affording
the expected phosphinophenolate derivatives. Subse-
quent reaction with chlorotrimethylsilane gives the silyl
ethers 2a–g in moderate to good yields (Scheme 2 and
Table 1).
In order to explain the selective C-phosphinylation of
these C,O-dilithio reagents, the reaction with 2-bro-
mophenol (entry 1) was monitored by 31P-NMR spec-
hydroxyaryl
diazaphospholidines,
using
their
borane-complex form [15], according to the following
general procedure (Scheme 1). Synthesis of the chiral
complexes 5 may be achieved in three steps from o-
trimethylsiloxyaryl diazaphospholidines 4, prepared by
exchange reaction in refluxing toluene from the key
intermediates, o-trimethylsiloxyaryl bis(dimethylamino)
phosphines 2 and various chiral diamines 3. Complexa-
tion of diazaphospholidines 4 by borane-dimethyl-
sulfide and subsequent methanolysis of the siloxy ether
function may lead to the formation of the desired
complexes 5.
Table 1
Synthesis of the key intermediates, o-trimethylsiloxyaryl bis(dimethy-
lamino) phosphines 2a–g
Entry
R1
R2
Product (yield a)
2. Results and discussion
1
2
3
4
5
6
7
H
H
H
H
Methyl
t-Butyl
t-Butyl
H
2a (50%)
2b (42%)
2c (47%)
2d (42%)
2e (58%)
2f (57%)
2g (60%)
Methyl
Phenyl
Cl
H
H
2.1. Synthesis of the key intermediates,
o-trimethylsiloxyaryl bis(dimethylamino) phosphines (2)
The key intermediates 2a–g were easily prepared as
described in the literature [13a,13b]. Treatment of the
o-bromophenols 1a–g with two equivalents of n-butyl-
t-Butyl
a Isolated yield after purification by distillation.

C.J. Ngono et al. / Journal of Organometallic Chemistry 643–644 (2002) 237–246
239
Scheme 3. Proposed mechanism for the formation of compound 2a.
Scheme 4. Synthesis of the o-trimethylsiloxyaryl diazaphospholidines 4.
troscopy. Analysis of the reaction mixture just at the
end of the addition of the chlorophosphine revealed the
presence of only one organophosphorus compound,
with a lP value of 134.3 ppm. After 2 h at ambient
temperature, a second compound appeared in the reac-
tion mixture, with l31P 99.6 ppm. The reaction was
complete after about 12 h. These observations led us to
propose the following mechanism for the formation of
precursors 2a–g (Scheme 3). The C,O-dilithio com-
pound A produced from 2-bromophenol and two
equivalents of n-butyllithium, reacts, with one equiva-
lent of chlorophosphine, preferably at the oxygen atom,
to give the organophosphorus compound B. The pres-
ence of a PꢀO bond in compound B is in accordance
with l31P value. A subsequent intramolecular 1,3-car-
banionic PꢀO to PꢀC rearrangement is then observed
leading to the formation of phenolate C, which can be
transformed to the silyl ether 2a by quenching the
reaction with trimethylchlorosilane.
dimethyl (1S,2S)-diphenylethanediamine (3c) [18], with
moderate to high isolated yields varying from 43 to
86% (Scheme 4 and Table 2). In the case of the use of
non-C2-symmetric chiral auxiliaries (entries 8–14),
compounds 4a–g, containing a stereogenic phosphorus
atom, were obtained in diastereomerically pure form as
the thermodynamic anti-diastereomer. All these P(III)-
chirogenic compounds were purified by distillation and
are quite stable to air and moisture. They represent a
new class of chiral bidentate PꢀO ligands which could
be of great interest in coordination chemistry [1,19].
Table 2
Synthesis of the o-trimethylsiloxyaryl diazaphospholidines 4a–j
Entry
R1
R2
Diamine
Product (% yield a)
8
9
H
H
H
H
methyl
t-Butyl
t-Butyl
H
Me
H
H
Methyl
Phenyl
Cl
H
H
t-Butyl
H
H
H
3a
3a
3a
3a
3a
3a
3a
3b
3b
3c
4a (80)
4b (80)
4c (58)
4d (78)
4e (68)
4f (82)
4g (86)
4h (50)
4i (60)
4j (43)
10
11
12
13
14
15
16
14
2.2. Synthesis of the o-trimethylsiloxyaryl
diazaphospholidines (4)
Compounds 4a–j were readily available, from the
exchange reaction in refluxing toluene between the pre-
cursors 2a–g and various chiral diamines such as (S)-2-
anilinomethylpyrrolidine (3a) [16], N,N%-dimethyl
(1R,2R)-cyclohexanediamine (3b) [17] and N,N%-
a Isolated yield after purification by distillation.

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C.J. Ngono et al. / Journal of Organometallic Chemistry 643–644 (2002) 237–246
Scheme 5. Methanolysis of the silyl ether function in diazaphospholidines 4.
Scheme 6. Synthesis of the o-hydroxyaryl diazaphospholidine–borane complexes 5.
2.3. Synthesis of the o-hydroxyaryl
diazaphospholidine–borane complexes (5)
complexes are obtained in diastereomerically pure
form, and in good yields ranging from 71 to 86%
(entries 15–19 and 24). However, methanolysis is not
so effective in the case of the use of diazaphospholidi-
nes derived from N,N%-dimethyl (1R,2R)-cyclohexane-
diamine (entries 22 and 23), or when a substituent is
present in ortho position on the phenol moiety (entries
20 and 21). Mixtures containing only small amounts of
the desired product were obtained, due to the forma-
tion of other uncharacterised organophosphorus
compounds.
On the basis of Heinicke’s published results
[13a,13b], methanolysis of the silyl ether function in
diazaphospholidines 4 may lead to the formation of the
corresponding free phosphanylphenols. Unfortunately,
all attempts to cleave these ethers by gentle heating
with an excess of absolute ethanol or methanol gave
complex mixtures of unidentified organophosphorous
compounds. However, when the methanolysis was con-
ducted at ambient temperature, formation of a major
product was observed, which was not the expected free
phosphanylphenol but the oxide 6 (Scheme 5). Experi-
ments are still in progress to determine the mechanism
of this reaction [20].
Table 3
Synthesis of the o-hydroxyaryl diazaphospholidines 5a–h
Entry R1
R2
Precursor
Product (% yield a)
To bypass this problem, we decided to protect the
phosphine moiety before the methanolysis reaction,
using borane complex methodology. Thus, the diaza-
phospholidines 4a–j react with 1.2 equivalent of
BH3ꢀSMe2 in toluene for 30 min at ambient tempera-
ture, affording quantitatively the corresponding phos-
phine–borane complexes after evaporation of the
solvent. Suspensions of these crude products in absolute
methanol are then stirred at ambient temperature until
complete dissolution of the solids (Scheme 6 and Table
3). After purification by chromatography on silica-gel,
the expected o-hydroxyaryl diazaphospholidine–borane
15
16
17
18
19
20
21
22
23
24
H
H
H
H
Methyl
t-Butyl
t-Butyl
H
Me
H
H
Methyl
Phenyl
Cl
H
H
t-Butyl
H
H
H
4a
4b
4c
4d
4e
4f
4g
4h
4i
5a (86)
5b (71)
5c (76)
5d (76)
5e (76)
b
b
5h (45)
5i (38)
5j (75)
4j
a Isolated yield after purification by column chromatography.
b Numerous unidentified products, but no traces of the expected
free phosphinophenol.

C.J. Ngono et al. / Journal of Organometallic Chemistry 643–644 (2002) 237–246
241
3. Conclusion
4.2.1. 2-Bromophenol (1a)
Yield: 62%; colourless oil; Rf=0.8 (petroleum ether);
1H-NMR l 7.6–6.5 (m, 4H), 5.4 (s, 1H); 13C-NMR l
152.1, 129.1, 116.1, 131.9, 121.7, 110.1.
In summary, we have developed a simple and highly
diastereoselective approach for the preparation of new
P(III)-chirogenic o-trimethylsiloxyaryl diazaphospho-
lidines. These compounds represent a new class of
chiral bidentate PꢀO ligands which could be of great
interest in coordination chemistry. Moreover, through
reaction with borane–dimethylsulfide and subsequent
cleavage of the silyl ethers, they are good precursors for
the synthesis of o-hydroxyaryl diazaphospholidines, in
the form of their borane complexes. To our knowledge,
this methodology represents the first accurate and to-
tally diastereoselective synthesis of P-stereogenic 2-hy-
droxyarylphosphine ligands. We are currently
extending the synthesis of such ligands using diols and
aminoalcohols as chiral auxiliaries. Investigations of
their catalytic ability as ligands or non-metallic cata-
lysts in enantioselective processes are still in progress.
4.2.2. 2-Bromo-4-methylphenol (1b)
Yield: 65%; colourless oil; Rf=0.9 (ethyl acetate–
1
petroleum ether, 20:80); H-NMR l 7.3 (m, 1H), 7.1–
6.9 (m, 2H), 5.7 (s, 1H), 2.3 (s, 3H); 13C-NMR l 149.8,
132.0, 131.2, 129.5, 115.7, 109.6, 19.9.
4.2.3. 3-Bromo-4-hydroxybiphenyl (1c)
Yield: 65%; white solid; m.p. 95 °C; Rf=0.9
1
(petroleum ether); H-NMR l 7.9–7.0 (m, 8H), 5.9 (s,
1H); 13C-NMR l 151.6, 139.3, 135.3, 130.4, 128.8,
127.9, 127.2, 126.7, 116.3, 110.6.
4.2.4. 2-Bromo-6-methylphenol (1e)
Yield: 58%; colourless oil; Rf=0.8 (petroleum ether);
1H-NMR l 7.2–7.1 (m, 1H), 6.9–6.8 (m, 1H), 6.6–6.4
(m, 1H), 5.3 (s, 1H), 2.2 (s, 3H); 13C-NMR l 150.3,
130.3, 129.3, 125.9, 121.1, 110.1, 16.5.
4. Experimental
4.2.5. 2-Bromo-6-tert-butylphenol (1f)
4.1. General considerations
Yield: 60%; colourless oil; Rf=0.7 (petroleum ether);
1H-NMR l 7.2–6.4 (m, 3H), 5.6 (s, 1H), 1.2 (s, 9H);
13C-NMR l 150.4, 137.6, 129.6, 126.5, 120.9, 112.3,
35.3, 29.3.
4.1.1. General
All reactions are conducted under dry argon using
Schlenk technique. Diethyl ether and tetrahydrofuran
(THF) were dried and freshly distilled over sodium
wire. Toluene was dried and freshly distilled over cal-
cium hydride. Methanol was dried and freshly distilled
over magnesium. The purity of all reagents was checked
by NMR spectroscopy. All melting points were taken
4.2.6. 2-Bromo-4,6-ditert-butylphenol (1g)
Yield: 59%; white solid; m.p. 56 °C; Rf=0.8
1
(petroleum ether); H-NMR l 7.2–6.9 (m, 2H), 5.4 (s,
1H), 1.2 (s, 9H), 1.1 (s, 9H); 13C-NMR l 148.1, 143.7,
136.8, 126.4, 123.7, 112.0, 35.7, 34.5, 31.6, 29.6.
1
on a Bu¨chi apparatus, and are uncorrected. H- and
4.3. Synthesis of chlorobis(dimethylamino)phosphine
13C-NMR spectra were recorded in CDCl3 solution at
200.00 and 50.30 MHz on a Bruker AC200 spectrome-
ter; 31P-NMR spectra were recorded in CDCl3 solution
at 40.50 MHz on a Bruker AC100 spectrometer (the
usual abbreviations are used: s, singlet; d, doublet; t,
triplet; q, quadruplet; m, multiplet). The chemical shift
values are given in ppm, and were determined, relative
to Me4Si (1H), CDCl3 (13C), and 85% H3PO4 (31P). IR
spectra were recorded on a Perkin–Elmer 298 IR spec-
trometer. Optical rotations were determined on a
Perkin–Elmer 241 MC polarimeter.
Chlorobis(dimethylamino)phosphine was prepared
according to a procedure described in the literature [22].
One equivalent of PCl3 was added dropwise at 0 °C to
two equivalents of P(NMe2)3. The mixture was warmed
to 100 °C and stirred for 1 h, the formation of the
product was monitored by 31P-NMR spectroscopy. The
product was not purified and used directly in the next
step. 31P-NMR l 161.9.
4.4. General procedure for the synthesis of the
o-trimethylsiloxyaryl bis(dimethylamino) phosphines
(2a–g)
4.2. Synthesis of the substituted o-bromophenols
2-Bromo-4-chlorophenol (1d) was purchased from
Acros Organics. The method of Pearson [21] was used
to prepare from the corresponding phenols, the substi-
tuted o-bromophenols 1a–c and 1e–g, which were not
commercially available. Products were purified by chro-
matography on silica-gel.
A solution of o-bromophenol 1 in dry ether was
cooled to −78 °C. Two equivalents of n-butyllithium
(10 M solution in n-hexane) were added dropwise with
stirring. The reaction mixture was then allowed to
warm slowly to room temperature (r.t.) and stirring was
continued for 4 h. The generated o-lithiophenolate

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C.J. Ngono et al. / Journal of Organometallic Chemistry 643–644 (2002) 237–246
precipitated. The mixture was cooled to −78 °C and a
slight excess (1.1 equivalents) of pure chlorobis(-
dimethylamino)phosphine was added dropwise. Stirring
was continued overnight at r.t. to complete the forma-
tion of the phosphine. Subsequently, 1.2 equivalents of
Me3SiCl were added dropwise at r.t. and the mixture
was stirred at least for 1 h. The precipitate was filtered
and washed several times with dry ether. The solvent
was evaporated under reduced pressure and the residue
distilled in vacuo.
4.4.6. 2-[Bis(dimethylamino)phosphanyl]-6-tert-butyl-
phenyl trimethylsilyl ether (2f)
Yield: 57%; colourless oil; b.p. 131 °C (0.02 mbar);
1H-NMR l 7.3–6.8 (m, 3H), 2.6 (d, J=9 Hz, 12H), 1.3
(s, 9H), 0.3 (s, 9H); 13C-NMR l 155.8 (d, J=19 Hz),
140.7, 132.6 (d, J=14 Hz), 129.9 (d, J=6 Hz), 128.0,
120.8, 41.0 (d, J=16 Hz), 34.9, 30.8, 2.6 (d, J=10 Hz);
31P-NMR l 97.4.
4.4.7. 2-[Bis(dimethylamino)phosphanyl]-4,6-di-
tert-butylphenyl trimethylsilyl ether (2g) [13d]
Yield: 60%; colourless oil; b.p. 140 °C (0.005 mbar);
1H-NMR l 7.3–7.0 (m, 2H), 2.5 (d, J=9 Hz, 12H), 1.3
(s, 9H), 1.20 (s, 9H), 0.2 (s, 9H); 13C-NMR l 153.7 (d,
J=18 Hz), 139.9, 130.9 (d, J=15 Hz), 127.0 (d, J=
6Hz), 125.2, 124.5, 41.2 (d, J=15 Hz), 35.5, 37.7, 31.2,
29.4, 2.9 (d, J=10 Hz); 31P-NMR l 97.8.
4.4.1. 2-[Bis(dimethylamino)phosphanyl]phenyl
trimethylsilyl ether (2a)
Yield: 50%; colourless oil; b.p. 90 °C (0.05 mbar);
1H-NMR l 7.5–6.8 (m, 4H), 2.7 (d, J=18 Hz, 12H),
0.3 (s, 9H); 13C-NMR l 156.9 (d, J=17 Hz), 132.3 (d,
J=6 Hz), 130.9 (d, J=7 Hz), 129.2, 120.9, 118.7, 41.4
(d, J=18 Hz), 0.6; 31P-NMR l 95.5.
4.5. General procedure for the synthesis of the
o-trimethylsiloxyaryl diazaphospholidines 4a–g
4.4.2. 2-[Bis(dimethylamino)phosphanyl]-4-methylphenyl
trimethylsilyl ether (2b)
To a solution of 2 in dry toluene was added one
equivalent of a solution of the chiral diamine 3. The
mixture was refluxed for 2 h. The solvent was then
removed by evaporation under reduced pressure and
the residue distilled in vacuo.
Yield: 42%; colourless oil; b.p. 99 °C (0.005 mbar);
1H-NMR l 7.4–6.6 (m, 3H), 2.6 (d, J=18 Hz, 12H),
2.3 (s, 3H), 0.2 (d, J=3 Hz, 9H); 13C-NMR l 154.6 (d,
J=17 Hz), 132.6 (d, J=6 Hz), 130.3 (d, J=6 Hz),
129.9, 129.7, 119.1, 41.7 (d, J=18 Hz), 20.9, 0.6 (d,
J=3 Hz); 31P-NMR l 96.0.
4.5.1. (2S,5S)-2-(2-Trimethylsiloxyphenyl)-3-
phenyl-1,3-diaza-2-phosphabicyclo[3.3.0]-octane (4a)
Yield: 80%; yellow viscous oil; b.p. 200 °C (0.005
4.4.3. 2-[Bis(dimethylamino)phosphanyl]-4-phenylphenyl
trimethylsilyl ether (2c)
1
mbar); [h]2D0= −398 (c=1, CH2Cl2); H-NMR l 7.3–
Yield: 47%; colourless oil; b.p. 150 °C (0.015 mbar);
1H-NMR l 7.6–7.1 (m, 6H), 6.8–6.7 (m, 2H), 2.7 (d,
J=18 Hz, 12H), 0.2 (d, J=2 Hz, 9H); 13C-NMR l
156.3 (d, J=16 Hz), 141.0 (d, J=10 Hz), 134.2 (d,
J=20 Hz), 130.9 (d, J=2 Hz), 130.8 (d, J=3 Hz),
128.4, 127.9, 127.7, 126.5, 126.3 (d, J=6 Hz), 120.1,
118,8, 41.4 (d, J=18 Hz), 0.5 (d, J=2 Hz); 31P-NMR
l 95.4.
7.0 (m, 4H), 6.9–6.6 (m, 5H), 4.0–3.9 (m, 1H), 3.6 (t,
J=7 Hz, 1H), 3.5–3.3 (m, 1H), 3.2–3.0 (m, 2H),
2.1–1.7 (m, 4H), 0.4 (s, 9H); 13C-NMR l 157.6 (d,
J=19 Hz), 147.2 (d, J=14 Hz), 132.1 (d, J=21 Hz),
130.3 (d, J=2 Hz), 129.0, 121.1, 119.2, 117.5 (d, J=13
Hz), 116.2, 115.0 (d, J=4 Hz), 64.0 (d, J=9 Hz), 53.6
(d, J=4 Hz), 52.5 (d, J=27 Hz), 25.6 (d, J=6 Hz),
17.5 (d, J=2 Hz), 0.6; 31P-NMR l 95.6.
4.4.4. 2-[Bis(dimethylamino)phosphanyl]-4-chlorophenyl
trimethylsilyl ether (2d)
4.5.2. (2S,5S)-2-(2-Trimethylsiloxy-5-methylphenyl)-3-
phenyl-1,3-diaza-2-phosphabicyclo[3.3.0]-octane (4b)
Yield: 80%; yellow viscous oil; b.p. 189 °C (0.01
Yield: 42%; colourless oil; b.p. 138 °C (0.002 mbar).
1H-NMR l 7.3–6.6 (m, 3H), 2.7 (d, J=18 Hz, 12H),
0.3 (d, J=2 Hz, 9H); 13C-NMR l 155.3 (d, J=17 Hz),
133.3 (d, J=11 Hz), 131.9 (d, J=6 Hz), 128.8, 126.2,
119.9, 41.5 (d, J=18 Hz), 0.5 (d, J=3 Hz); 31P-NMR
l 94.3.
1
mbar); [h]2D0= −327 (c=1, CH2Cl2); H-NMR l 7.3–
7.2 (m, 2H), 7.0–6.0 (m, 1H), 6.9–6.7 (m, 5H), 4.0–3.9
(m, 1H), 3.6–3.5 (m, 1H), 3.4–3.0 (m, 3H), 2.1 (s, 3H),
2.1–1.8 (m, 4H), 0.3 (s, 9H); 13C-NMR l 155.3 (d,
J=17 Hz), 147.4 (d, J=17 Hz), 131.8 (d, J=20 Hz),
130.8, 130.4, 130.3 (d, J=9 Hz), 129.0, 119.0, 117.4,
115.0 (d, J=14 Hz), 64.0 (d, J=9 Hz), 53.6 (d, J=5
Hz), 52.4 (d, J=30 Hz), 30.4, 25.6 (d, J=8 Hz), 20.8,
0.5; 31P-NMR l 96.4.
4.4.5. 2-[Bis(dimethylamino)phosphanyl]-6-methylphenyl
trimethylsilyl ether (2e)
Yield: 58%; colourless oil; b.p. 100 °C (0.015 mbar);
1H-NMR l 7.2–6.8 (m, 3H), 2.6 (d, J=18 Hz, 12H),
2.2 (s, 3H), 0.2 (d, J=3 Hz, 9H); 13C-NMR l 155.6 (d,
J=17 Hz), 131.5 (d, J=6 Hz), 131.3, 129.7 (d, J=6
Hz), 128.9, 121.2, 40. 4 (d, J=18 Hz), 18.0, 1.4 (d,
J=6 Hz); 31P-NMR l 96.4.
4.5.3. (2S,5S)-2-(2-Trimethylsiloxy-5-phenylphenyl)-3-
phenyl-1,3-diaza-2-phosphabicyclo[3.3.0]-octane (4c)
Yield: 58%; yellow viscous oil; b.p. 214 °C (0.004
1
mbar); [h]2D0= −328 (c=1, CH2Cl2); H-NMR l 7.6–

C.J. Ngono et al. / Journal of Organometallic Chemistry 643–644 (2002) 237–246
243
7.0 (m, 10H), 6.9–6.5 (m, 3H), 3.9 (m, 1H), 3.6–2.9 (m,
4H), 2.1–1.3 (m, 4H), 0.3 (s, 9H); 13C-NMR l 156.4 (d,
J=18 Hz), 148.3, 147.2 (d, J=15 Hz), 141.0, 134.5,
134.0, 132.2, 129.3, 129.1 (d, J=2 Hz), 128.7, 128.5,
126.7, 120.3, 117.4 (d, J=16 Hz), 115.1 (d, J=22 Hz),
112.9, 64.1 (d, J=8 Hz), 53.7 (d, J=4 Hz), 52.4 (d,
J=30 Hz), 30.7, 25.7 (d, J=6 Hz), 0.7; 31P-NMR l
95.9.
Hz), 141.6, 132.3 (d, J=20 Hz), 128.9, 128.4 (d, J=3
Hz), 121.2, 117.1, 115.2 (d, J=15 Hz), 112.9, 63.8 (d,
J=8 Hz), 54.0 (d, J=5 Hz), 52.2 (d, J=26 Hz), 35.6,
34.5, 31.4, 30.6, 29.4, 25.3 (d, J=6 Hz), 2.7 (d, J=10
Hz); 31P-NMR l 97.8.
4.5.8. (1R,5R)-2,4-Dimethyl-3-(2-Trimethylsiloxy-
phenyl)-2,4-diaza-3-phosphabicyclo[4.3.0]-nonane (4h)
Yield: 50%; yellow viscous oil; b.p. 189 °C (0.003
1
4.5.4. (2S,5S)-2-(2-Trimethylsiloxy-5-chlorophenyl)-3-
phenyl-1,3-diaza-2-phosphabicyclo[3.3.0]-octane (4d)
Yield: 78%; yellow viscous oil; b.p. 197 °C (0.005
mbar); [h]2D0= +49 (c=1, CH2Cl2); H-NMR l 7.6–
6.6 (m, 4H), 2.6 (d, J=10 Hz, 3H), 2.5 (d, J=9 Hz,
3H), 2.3–2.2 (m, 2H), 2.2–1.6 (m, 4H), 1.5–1.2 (m,
4H), 0.4 (m, 9H); 13C-NMR l 157.9 (d, J=3 Hz),
134.1 (d, J=3 Hz), 129.9, 120.2, 118.9 (d, J=13 Hz),
117.4 (d, J=10 Hz), 71.1 (d, J=3 Hz), 64.9 (d, J=4
Hz), 31.3 (d, J=9Hz), 29.1 (d, J=2 Hz), 28.4 (d, J=6
Hz), 28.2 (d, J=6 Hz), 24.1, 23.9, 0.3; 31P-NMR l
103.2.
1
mbar); [h]2D0= −313 (c=1, CH2Cl2); H-NMR l 7.2–
6.6 (m, 8H), 3.96 (m, 1H), 3.9–3.8 (m, 1H), 3.4–3.6 (m,
3H), 2.1 (m, 4H), 0.3 (s, 9H); 13C-NMR l 156.1 (d,
J=18 Hz), 147.1 (d, J=17 Hz), 134.8 (d, J=28 Hz),
130.1, 129.7 (d, J=7 Hz), 129.1, 126.4, 120.4, 117.9,
115.2 (d, J=14 Hz), 64.1 (d, J=9 Hz), 53.5 (d, J=5
Hz), 52.5 (d, J=31 Hz), 30.5, 23.6 (d, J=6 Hz), 0.5;
31P-NMR l 94.2.
4.5.9. (1R,5R)-2,4-Dimethyl-3-(2-trimethylsiloxy-3-
methylphenyl)-2,4-diaza-3-phosphabicyclo[4.3.0]-nonane
(4i)
4.5.5. (2S,5S)-2-(2-Trimethylsiloxy-3-methylphenyl)-3-
phenyl-1,3-diaza-2-phosphabicyclo[3.3.0]-octane (4e)
Yield: 68%; yellow viscous oil; b.p. 210 °C (0.02
Yield: 60%; yellow viscous oil; b.p. 164 °C (0.02
1
mbar); [h]2D0= +119 (c=1, CH2Cl2); H-NMR l 7.6–
1
mbar); [h]2D0= −234 (c=1, CH2Cl2); H-NMR l 7.3–
6.7 (m, 3H), 2.7 (d, J=10 Hz, 3H), 2.6 (d, J=9 Hz,
3H), 2.4–2.3 (m, 2H), 2.2 (s, 3H), 2.1–1.6 (m, 4H),
1.5–1.1 (m, 4H), 0.4 (m, 9H); 13C-NMR l 157.9 (d,
J=2 Hz), 147.2 (d, J=8 Hz), 136.2 (d, J=8 Hz),
133.9 (d, J=20 Hz), 128.5 (d, J=2 Hz), 117.4 (d, J=4
Hz), 69.5 (d, J=3 Hz), 65.6 (d, J=4 Hz), 31.9 (d,
J=6Hz), 29.5 (d, J=2 Hz), 29.1 (d, J=6 Hz), 28.7 (d,
J=5 Hz), 24.5, 23.4, 16.2 (d, J=2 Hz), 1.2; 31P-NMR
l 103.6.
7.1 (m, 3H), 6.9–6.8 (m, 5H), 4.0–3.9 (q, J=7 Hz,
1H), 3.7–3.4 (t, J=8 Hz, 1H), 3.4–3.3 (m, 1H), 3.2–
3.0 (m, 2H), 2.3 (s, 3H), 2.1–1.8 (m, 4H), 0.5 (d, J=7
Hz, 9H); 13C-NMR l 156.1 (d, J=19 Hz), 147.0 (d,
J=14 Hz), 132.4, 131.3 (d, J=21 Hz), 128.9 (d, J=2
Hz), 128.9, 121.3, 117.4, 114.8 (d, J=13 Hz), 112.7 (d,
J=4 Hz), 63.9 (d, J=9 Hz), 53.4 (d, J=4 Hz), 52.2
(d, J=27 Hz), 29.8, 25.1 (d, J=6 Hz), 17.5 (d, J=2
Hz), 1.2 (d, J=6 Hz); 31P-NMR l 96.6.
4.5.10. (3S,4S)-2,5-Dimethyl-1-(2-trimethylsiloxy-
phenyl)-2,5-diaza-4-phospholidine (4j)
4.5.6. (2S,5S)-2-(2-Trimethylsiloxy-3-tert-butylphenyl)-
3-phenyl-1,3-diaza-2-phosphabicyclo[3.3.0]-octane (4f)
Yield: 82%; yellow viscous oil; b.p. 190 °C (0.02
mbar); [h]2D0= −249 (c=1.05, CH2Cl2); 1H-NMR l
7.4–6.8 (m, 8H), 4.0 (m, 1H), 3.7–3.1 (m, 2H), 2.2–1.8
(m, 2H), 2.1–1.8 (m, 4H), 1.7 (s, 9H), 0.6 (d, J=3 Hz,
9H); 13C-NMR l 156.5 (d, J=21 Hz), 146.8 (d, J=16
Hz), 149.7, 132.1 (d, J=24 Hz), 129.1, 128.5 (d, J=3
Hz), 120.9, 117.6, 115.1 (d, J=13 Hz), 112.8, 63.6 (d,
J=8 Hz), 53.4 (d, J=4 Hz), 51.9 (d, J=25 Hz), 34.9,
30.7, 29.5, 25.2 (d, J=6 Hz), 2.9 (d, J=12 Hz);
31P-NMR l 96.4.
Yield: 43%; yellow viscous oil; b.p. 194 °C (0.008
1
mbar); [h]2D0= +15.8 (c=1, CH2Cl2); H-NMR l 7.3–
6.8 (m, 13H), 3.9–3.7 (m, 2H), 2.6 (d, J=15 Hz, 3H),
2.2 (d, J=15 Hz, 3H), 0.3 (s, 9H); 13C-NMR l 158.8
(d, J=20 Hz), 139.0, 138.2 (d, J=5 Hz), 132.0, 130.4,
128.5, 128.2, 122.0 (d, J=3 Hz), 127.8, 127.5 (d, J=11
Hz), 120.7, 118.3, 75.0 (d, J=10 Hz), 32.2 (d, J=7
Hz), 0.5 (d, J=2 Hz); 31P-NMR l 107.5.
4.6. Methanolysis of the silyl ether function in compound
4f
4.5.7. (2S,5S)-2-(2-Trimethylsiloxy-3,5-di-tert-butyl-
phenyl)-3-phenyl-1,3-diaza-2-phosphabicyclo[3.3.0]-
octane (4g)
A suspension of compound 4f in dry methanol is
stirred overnight at r.t. The solvent is then evaporated
under reduced pressure and the major product formed,
i.e. oxide 6 is precipitated after the addition of
petroleum ether.
Yield: 86%; yellow viscous oil; b.p. 198 °C (0.02
1
mbar); [h]2D0= −254 (c=1, CH2Cl2); H-NMR l 7.3–
6.9 (m, 7H), 4.1 (m, 1H), 3.9–3.7 (m, 2H), 3.3–3.1 (m,
2H), 2.2–1.9 (m, 4H), 1.2 (s, 9H), 1.1 (s, 9H), 0.2 (s,
9H); 13C-NMR l 156.6 (d, J=17 Hz), 146.8 (d, J=15
6: White solid; 1H-NMR l 10.1 (s, 1H), 7.6 (d,
J=530 Hz, 1H), 7.3–6.5 (m, 8H), 3.5 (m, 1H), 3.3 (m,
2H), 3.1–2.8 (m, 3H), 1.9–1.5 (m, 4H), 1.4 (s, 9H);

244
C.J. Ngono et al. / Journal of Organometallic Chemistry 643–644 (2002) 237–246
13C-NMR l 159.5 (d, J=5 Hz), 147.6, 137.2 (d, J=8
Hz), 130.3, 129.4 (d, J=10 Hz), 129.3, 121.1, 118.7 (d,
J=14 Hz), 117.8, 112.9, 59.3, 44.6 (d, J=13 Hz), 35.0,
31.7, 29.4, 27.9, 23.6; 31P-NMR l 18.2.
4.7.3. (2S,5S)-2-(2-Hydroxy-5-phenylphenyl)-3-phenyl-
1,3-diaza-2-phosphabicyclo[3.3.0]-octane–borane
complex (5c)
Yield: 76%; white solid; m.p. 132–134 °C; Rf=0.3
(ethyl acetate–petroleum ether, 5:95); [h]2D0= −172
1
(c=1, CH2Cl2); H-NMR l 9.9 (s, 1H), 7.9–6.7 (m,
4.7. General procedure for the synthesis of the
o-hydroxyaryl diazaphospholidine–borane complexes
5a–g
13H), 4.2–3.9 (m, 1H), 3.9–3.5 (m, 2H), 3.5–3.1 (m,
2H), 2.4–2.6 (m, 4H), 1.5–1.1 (m, 2H), 0.9 (m, 1H);
13C-NMR l 158.6 (d, J=3 Hz), 141.8 (d, J=7 Hz),
139.6, 132.7, 132.4, 130.3 (d, J=15 Hz), 129.2, 128.4,
122.5, 119.2, 117.9, 116.2 (d, J=55 Hz), 115.7 (d, J=3
Hz), 115.2, 114.7, 113.2, 60.0, 52.0, 48.8, 31.7, 26.3;
31P-NMR l 107.6 (br); IR (neat, cm−1): 3470 (s, OH),
3095 (m), 2975 (m), 2950 (m), 2883 (m), 2387 (s, BH),
2348 (m, BH), 1630 (m), 1602 (s), 1501 (s), 1310 (s),
1287 (s), 1187 (s).
To a solution of the chiral phosphine 4 in dry THF
is added a slight excess (1.2 equivalents) of BH3ꢀSMe2.
The solution is stirred for at least 30 min at r.t.
Subsequently, the solvent is evaporated under reduced
pressure and the residue is suspended in dry methanol.
The suspension is stirred overnight at r.t. to complete
the formation of 5 which is soluble in methanol. The
solvent is then evaporated under reduced pressure and
the product is purified by flash chromatography on
silica-gel.
4.7.4. (2S,5S)-2-(2-Hydroxy-5-chlorophenyl)-3-phenyl-
1,3-diaza-2-phosphabicyclo[3.3.0]-octane–borane
complex (5d)
Yield: 76%; white solid; m.p. 80–85 °C; Rf=0.4
(ethyl acetate–petroleum ether, 20:80); [h]2D0= −171.8
(CH2Cl2); 1H-NMR l 9.2 (s, 1H), 7.4–6.7 (m, 8H),
4.2–4.0 (m, 1H), 3.9–3.5 (m, 2H), 3.4–3.0 (m, 2H),
2.2–1.7 (m, 4H), 1.2–0.1 (m, 3H); 13C-NMR l 157.7
(d, J=3 Hz), 141.7 (d, J=10 Hz), 133.8, 131.2 (d,
J=15 Hz), 129.4, 124.8 (d, J=15 Hz), 122.5, 119.3 (d,
J=5 Hz), 118.7 (d, J=4 Hz), 118.0 (d, J=50 Hz),
62.0, 52.5, 48.5 (d, J=4 Hz), 31.8, 26.3; 31P-NMR l
105.1 (br); IR (neat, cm−1): 3470 (s, OH), 3095 (m),
2975 (m), 2950 (m), 2883 (m), 2387 (s, BH), 2348 (m,
BH), 1630 (m), 1602 (s), 1501 (s), 1310 (s), 1287 (s),
1187 (s), 650 (m).
4.7.1. (2S,5S)-2-(2-Hydroxyphenyl)-3-
phenyl-1,3-diaza-2-phosphabicyclo[3.3.0]-octane–borane
complex (5a)
Yield: 86%; white solid; m.p. 115–122 °C; Rf=0.3
(ethyl acetate–petroleum ether, 20:80); [h]2D0= −164.2
1
(c=1, CH2Cl2); H-NMR l 9.8 (s, 1H), 7.6–6.7 (m,
9H), 4.1–4.0 (m, 1H), 3.9–3.6 (m, 2H), 3.4–3.1 (m,
2H), 2.2–1.7 (m, 4H), 1.1–0.1 (m, 3H); 13C-NMR l
159.2, 142.0 (d, J=7 Hz), 134.0, 132.1 (d, J=15 Hz),
129.1, 122.3, 119.8 (d, J=19 Hz), 118.9 (d, J=4 Hz),
117.7 (d, J=5 Hz), 116.5 (d, J=35 Hz), 61.9 (d, J=3
Hz), 52.4 (d, J=3 Hz), 48.6 (d, J=4 Hz), 31.7, 26.3 (d,
J=4 Hz); 31P-NMR l 106.5 (br); IR (neat, cm−1):
3470 (s, OH), 3095 (m), 2975 (m), 2950 (m), 2883 (m),
2387 (s, BH), 2348 (m, BH), 1630 (m), 1602 (s), 1501
(s), 1310 (s), 1287 (s), 1187 (s).
4.7.5. (2S,5S)-2-(2-Hydroxy-3-methylphenyl)-3-phenyl-
1,3-diaza-2-phosphabicyclo[3.3.0]-octane–borane
complex (5e)
Yield: 76%; white solid; m.p. 124–126 °C; Rf=0.25
(ethyl acetate–petroleum ether, 5:95); [h]2D0= −187.5
1
(c=1, CH2Cl2); H-NMR l 9.9 (s, 1H), 7.3–6.7 (m,
4.7.2. (2S,5S)-2-(2-Hydroxy-5-methylphenyl)-3-phenyl-
1,3-diaza-2-phosphabicyclo[3.3.0]-octane–borane
complex (5b)
8H), 3.9 (m, 1H), 3.7–3.5 (m, 2H), 3.3–3.0 (m, 2H), 2.0
(s, 3H), 2.0–1.6 (m, 5H), 1.5–0.5 (m, 2H); 13C-NMR l
157.4 (d, J=3 Hz), 142.2 (d, J=6 Hz), 135.0 (d, J=2
Hz), 129.7 (d, J=15 Hz), 129.1, 126.5 (d, J=5 Hz),
122.3, 119.5 (d, J=12 Hz), 118.9 (d, J=4 Hz), 115.5
(d, J=56 Hz), 61.9 (d, J=3 Hz), 52.4, 48.6 (d, J=4
Hz), 31.7 (d, J=3 Hz), 26.3 (d, J=4 Hz), 16.0; 31P-
NMR l 107.6 (br); IR (neat, cm−1): 3470 (s, OH), 3095
(m), 2975 (m), 2950 (m), 2883 (m), 2387 (s, BH), 2348
(m, BH), 1630 (m), 1602 (s), 1501 (s), 1310 (s), 1287 (s),
1187 (s).
Yield: 71%; white solid; m.p. 70–75 °C; Rf=0.4
(ethyl acetate–petroleum ether, 20:80); [h]2D0= −90.9
1
(c=1, CH2Cl2); H-NMR l 8.9 (s, 1H), 7.1–6.2 (m,
8H), 3.9 (m, 1H), 3.7–3.4 (m, 2H), 3.4–2.9 (m, 2H), 1.9
(s, 3H), 1.9–1.4 (m, 4H), 1.3–0.5 (m, 3H); 13C-NMR l
156.7 (d, J=3 Hz), 142.1 (d, J=7 Hz), 134.6 (d, J=2
Hz), 131.9 (d, J=6 Hz), 128.9 (d, J=4 Hz), 128.7 (d,
J=8 Hz), 121.7, 118.3 (d, J=4 Hz), 117.2 (d, J=6
Hz), 116.2 (d, J=56 Hz), 61.7 (d, J=2 Hz), 52.3 (d,
J=3 Hz), 41.8 (d, J=5 Hz), 31.4 (d, J=2 Hz), 26.0
(d, J=4 Hz), 20.2; 31P-NMR l 105.6 (br); IR (neat,
cm−1): 3470 (s, OH), 3095 (m), 2975 (m), 2950 (m),
2883 (m), 2387 (s, BH), 2348 (m, BH), 1630 (m), 1602
(s), 1501 (s), 1310 (s), 1287 (s), 1187 (s).
4.7.6. (1R,5R)-2,4-Dimethyl-3-(2-hydroxyphenyl)-2,4-
diaza-3-phosphabicyclo[4.3.0]-nonane–borane
complex (5h)
Yield: 45%; white solid; m.p. 97–98 °C; Rf=0.45
(ethyl acetate–petroleum ether, 20:80); [h]2D0= −35.4

C.J. Ngono et al. / Journal of Organometallic Chemistry 643–644 (2002) 237–246
245
1
(c=1, CH2Cl2); H-NMR l 10.8 (s, 1H), 7.6–6.7 (m,
4H), 2.7 (d, J=9 Hz, 3H), 2.6–2.5 (m, 2H), 2.3 (d,
J=8 Hz, 3H), 2.2–1.8 (m, 4H), 1.4 (m, 5H), 1.0–0.1
(m, 2H); 13C-NMR l 160.9 (d, J=3 Hz), 134.8, 134.5
(d, J=4 Hz), 129.0 (d, J=30 Hz), 119.8 (d, J=12
Hz), 117.3 (d, J=4 Hz), 67.4, 65.4 (d, J=3 Hz), 31.6
(d, J=6 Hz), 29.1 (d, J=3 Hz), 28.7 (d, J=8 Hz),
28.4 (d, J=6 Hz), 24.0, 23.7; 31P-NMR l 116.3 (br); IR
(neat, cm−1): 3470 (s, OH), 3095 (m), 2975 (m), 2950
(m), 2883 (m), 2387 (s, BH), 2348 (m, BH), 1630 (m),
1602 (s), 1501 (s), 1310 (s), 1287 (s), 1187 (s).
References
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4.7.7. (1R,5R)-2,4-Dimethyl-3-(2-hydroxy-3-methyl-
phenyl)-2,4-diaza-3-phosphabicyclo[4.3.0]-nonane–
borane complex (5i)
Yield: 38%; white solid; m.p. 122–124 °C; Rf=0.45
(ethyl acetate–petroleum ether, 20:80); [h]2D0= −52.3
1
(c=1, CH2Cl2); H-NMR l 10.3 (s, 1H), 7.9–6.9 (m,
3H), 2.5 (d, J=36 Hz, 3H), 2.2 (d, J=21 Hz, 3H),
1.7–1.2 (m, 6H), 1.2–1.1 (m, 4H), 1.2 (s, 3H), 1.0–0.6
(m, 3H); 13C-NMR l 160.9 (d, J=2 Hz), 146.7 (d,
J=8 Hz), 137.8 (d, J=8 Hz), 133.6 (d, J=20 Hz),
127.9 (d, J=2 Hz), 119.4 (d, J=4 Hz), 68.3 (d, J=3
Hz), 66.3 (d, J=4 Hz), 31.7 (d, J=4 Hz), 29.6 (d,
J=2 Hz), 29.1 (d, J=8 Hz), 28.7 (d, J=6 Hz), 24.5
(d, J=2 Hz), 23.9 (d, J=2 Hz), 16.2 (d, J=2 Hz);
31P-NMR l 117.9 (br); IR (neat, cm−1): 3470 (s, OH),
3095 (m), 2975 (m), 2950 (m), 2883 (m), 2387 (s, BH),
2348 (m, BH), 1630 (m), 1602 (s), 1501 (s), 1310 (s),
1287 (s), 1187 (s).
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4.7.8. (3S,4S)-2,5-dimethyl-1-(2-hydroxyphenyl)-
2,5-diaza-4-phospholidine–borane complex (5j)
Yield: 75%; white solid, m.p. 65–75 °C; Rf=0.3
(ethyl acetate–petroleum ether, 20:80); [h]2D0= −20.1
1
(c=1, CH2Cl2); H-NMR l 10.4 (s, 1H), 8.2–7.8 (m,
4H), 7.6–6.9 (m, 10H), 4.3–4.0 (m, 2H), 2.5 (d, J=12
Hz, 3H), 2.2 (d, J=12 Hz, 3H), 1.4–0.5 (m, 3H);
13C-NMR l 160.9 (d, J=2 Hz), 138.4, 136.6 (d, J=9
Hz), 135.3 (d, J=4 Hz), 134.9, 128.9, 128.8, 128.5,
128.4, 127.9 (d, J=10 Hz), 120.2, 117.4 (d, J=4 Hz),
75.2 (d, J=3 Hz), 31.7 (d, J=7 Hz), 14.2; 31P-NMR l
117.5 (br); IR (neat, cm−1): 3470 (s, OH), 3095 (m),
2975 (m), 2950 (m), 2883 (m), 2387 (s, BH), 2348 (m,
BH), 1630 (m), 1602 (s), 1501 (s), 1310 (s), 1287 (s),
1187 (s).
(h) C. Hollatz, A. Schier, H. Schmidbaur, Z. Naturforsch. 54b
(1999) 30;
(i) J. Heinicke, U. Jux, Inorg. Chem. Commun. 2 (1999) 55.
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[12] (a) J. Heinicke, E. Nietzschmann, A. Tzschach, J. Organomet.
Chem. 243 (1983) 1;
(b) J. Heinicke, A. Tzschach, Phosphorus Sulfur 25 (1985) 345;
(c) J. Heinicke, E. Nietzschmann, A. Tzschach, J. Organomet.
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(d) J. Heinicke, R. Kadyrov, J. Organomet. Chem. 520 (1996)
131.
[13] (a) J. Heinicke, R. Kadyrov, M.K. Kindermann, M. Kloss, A.
Fischer, P.G. Jones, Chem. Ber. 129 (1996) 1061;
(b) J. Heinicke, R. Kadyrov, M.K. Kindermann, M. Koesling,
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Acknowledgements
We thank Inspec Fine Chemical Company and Dr
Brigitte Saliva for financial support. C.J.N. thanks the
CNRS and Region PACA for a doctoral fellowship.
Thanks are also due to Dr J.-M. Brunel for fruitful
discussions.
(c) J. Heinicke, U. Jux, R. Kadyrov, M. He, Heteroatom Chem.
8 (1997) 383;
(d) J. Heinicke, M. He, R. Kadyrov, P.G. Jones, Heteroatom
Chem. 9 (1998) 183.

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[15] Phosphine–borane reagents are used in synthesis where the
borane moiety serves as a protecting group for the phosphine
and can be displaced in a non-racemizing decomplexation step.
For some recent reviews, see: (a) J.M. Brunel, B. Faure, M.
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1391;
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[16] For a large scale synthesis of this diamine, see J.M. Brunel,
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8940.
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76 (1998) 23.
[19] Direct reaction beetween these ligands and halogenated metal
complexes, followed by elimination of Me3SiX (see Ref. [2e]),
could lead to the formation of PꢀO chelate complexes containing
a P chiral atom very close to the metal center.
[20] Similar results have been already reported by Heinicke et al. (see
Ref. [13d]), but without any experimental or mechanistic details.
[21] D.E. Pearson, R.D. Wysong, C.V. Breder, J. Org. Chem. 32
(1967) 2358.
[22] R.B. King, W.F. Masler, J. Am. Chem. Soc. 99 (1977) 4001.