Synthesis and characterisation of monophosphines and aminophosphines bearing chiral phosphetane units

Article abstract of DOI:10.1055/s-2001-18064

Enantiomerically pure monophosphines bearing phosphetane units have been prepared from primary phosphines and the cyclic sulfates of anti-1,3-diols. Various substituents have been introduced on both the phosphorus and the ring carbon atoms, thus showing t

Full text of DOI:10.1055/s-2001-18064

PAPER
2095
Synthesis and Characterisation of Monophosphines and Aminophosphines
Bearing Chiral Phosphetane Units
S
ynthesis of Chira
n
l
P
hosphetan
g
es ela Marinetti,*a Sébastien Jus,a Francis Labrue,a Aude Lemarchand,a Jean-Pierre Genêt,a Louis Ricardb
a
Laboratoire de Synthèse Sélective Organique et Produits Naturels - ENSCP -, 11, rue Pierre et Marie Curie, 75231 Paris Cedex 05, France
b
Laboratoire Hétéroéléments et Coordination, Ecole Polytechnique, 91128 Palaiseau Cedex, France
Fax +33(1)44071062; E-mail: marinet@ext.jussieu.fr
Received 1 June 2001; revised 17 July 2001
alytic applications and, therefore, new variations of the
general structure I are highly desirable. In this context we
present here the synthesis and characterisation of new
monodentate phosphetanes as well as the first examples of
Abstract: Enantiomerically pure monophosphines bearing phos-
phetane units have been prepared from primary phosphines and the
cyclic sulfates of anti-1,3-diols. Various substituents have been in-
troduced on both the phosphorus and the ring carbon atoms, thus
showing the high flexibility of the synthetic approach. The same P–N heterobidentate phosphetanes.
synthetic method has been applied to the preparation of P–N heter-
obidentate ligands bearing phosphetane and azetidine rings. The fi-
nal products have been characterised by X-ray diffraction studies.
R
R
Key words: phosphorus, heterocycles, metallocenes, transition
metals, asymmetric catalysis
P
P
R
R
P
X
R
R
Structural modularity is a key feature for chiral ligands in
order to be broadly useful in enantioselective catalysis.
Thus, whenever a new efficient synthon or concept for
ligand design has been highlighted, the versatility of the
corresponding synthetic approach must be checked in a
systematic fashion to ensure optimisation of the properties
of these ligands for any given purpose. This is the case for
the chiral synthons I, namely the 2,4-disubstituted phos-
phetane moieties, which are easily accessible from enan-
tiomerically pure 1,3-diol derivatives. They have already
been used for the synthesis of diphosphine ligands, II,
highly efficient in enantioselective ruthenium and rhodi-
um catalysed hydrogenations.1 The nature of the phosphe-
tane-connecting scaffold in II modulates the catalyst
efficiency and opens, for instance, specific application
fields to the bis-phosphetanoferrocenes (X = 1,1’-fer-
rocenediyl) with respect to the bis-phosphetanobenzenes
(X = 1,2-phenylene) or bis-phosphetanoethanes (X = 1,2-
ethanediyl) (Figure 1).
I
II
X = 1,2-phenylene, 1,2-ethanediyl,
1,1'-ferrocenediyl
Figure 1 Structures of model chiral phosphetane units I and II
Generally speaking, the successful use of bidentate
ligands in many asymmetric catalytic reactions obscures
the field of chiral monodentate phosphines. Nevertheless,
recent literature data provide clear evidence for the specif-
ic catalytic applications of monodentate phosphorus
ligands and point out the crucial need for efficient chiral
phosphines of this family.3 In this context, monodentate
phosphetanes could be interesting tools as they are readily
available from virtually any primary phosphine and a
number of 1,3-diols, according to the synthetic approach
shown in Scheme 1. Consequently, after our initial report
on the synthesis of 1a (R’ = Ph, R = Me) and 2
(R’ = Mesityl, R = Me),1a the general synthetic method
has been widely developed and the catalytic potential of
monodentate phosphetanes has been proven, as shown
hereafter.4
Within a single family of bis-phosphetanes II, the steric
properties of the ligands have been finely tuned by varia-
tions of the R substituents, as the chiral anti-1,3-diols re-
quired for their synthesis are very easily available via
asymmetric hydrogenation of the corresponding 1,3-dike-
tones.2
The cyclic sulfates of several anti-1,3-diols were em-
ployed in the reaction with dilithiated phenylphosphine to
afford the corresponding phosphetane-borane complexes
8a–e in moderate to good yields (40–80%). Notably, even
the highly hindered 2,2,6,6-tetramethylheptane-3,5-diol
cyclic sulfate afforded the phosphetane borane 8e in ac-
ceptable yield (46%). However, the attempted synthesis
of (S,S)-1,2,4-triphenylphosphetane from the bis-mesy-
late of (R,R)-1,3-diphenylpropane-1,3-diol, led to the un-
desired meso-isomer of the expected phosphetane.5
Racemisation of the benzylic carbon atoms takes place
under basic reaction conditions to afford the more stable
As application field for chiral phosphetanes, previous
work considered mainly catalytic hydrogenations, which
founded the choice of bidentate, C2-symmetric phos-
phines as target structures. However, phosphetane-based
ligands could also be designed for a number of other cat-
Synthesis 2001, No. 14, 26 10 2001. Article Identifier:
1437-210X,E;2001,0,14,2095,2104,ftx,en;T03901SS.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

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A. Marinetti et al.
PAPER
ate, bulky primary phosphines as starting materials. This
has been demonstrated in this work by applying both sub-
stituted arylphosphines, that is mesityl-, o-anisyl- and o-
tolylphosphine, and very bulky ferrocene-derived phos-
phines to the synthesis of phosphetanes. In addition, tri-
alkyl phosphetanes have been prepared from
ferrocenylmethylphosphine and cyclohexylphosphine.
Figure 2 Essential structural features of chiral monodentate phos-
phetane ligands
Phosphetanes 2–7 have been obtained as their borane
complexes 9–14 following a two-steps procedure: the
monolithiated phosphine was reacted at –78 °C to 0 °C
with the cyclic sulfate of the enantiomerically pure 1,3-di-
ol, then addition of one equivalent of s-BuLi allowed
deprotonation of the remaining PH function and cyclisa-
tion. Complexation of phosphorus with BH3 was per-
formed by adding an excess BH3◊SMe2 to the crude
reaction mixture (see experimental section). Yields for all
isolated phosphetane borane complexes, including 11 and
12, were satisfying, thus showing that even monosubsti-
tuted ferrocenyl moieties are fully compatible with the
phosphetane synthesis above. Other bulky organometallic
fragments can also be reasonably envisaged as phospho-
rus substituents in monodentate phosphetanes.
Scheme 1
anti-anti isomer.6 Phosphetanes 1a–e were obtained then
quantitatively from their borane complexes 8a–e by reac-
tion with an excess DABCO in benzene at 40 °C.
+
–
Stable rhodium complexes (COD)Rh(L*)2 PF6 were iso-
lated for L* = 1a–d by reacting two equivalents of the
corresponding phosphetanes with (COD)2RhPF6 in
dichloromethane at room temperature. They proved to be
efficient catalyst precursors for hydrogenation reactions
of model substrates (see experimental section). Especial-
ly, in the hydrogenation of N-acetyldehydrophenylala-
nine, phosphetanes 1a (R = Me) and 1d (R = CH2Ph)
afforded enantiomeric excesses of 80% and 86% respec-
tively. These values compare favourably with the ee at-
tained in the hydrogenation of the same acid, or the
corresponding ester, by other monodentate phosphines
(CAMP: 85% ee;7 [2-(4-methoxymethyl-1,3-dioxan-2-
yl)ferrocenyl]diphenylphosphine: 87% ee;8 1,2,5-triphe-
nylphospholane: 82% ee;6b 2,5-dimethyl-1-phenylphos-
pholane: 60% ee9) and suggest a promising potential for
these ligands. Their catalytic efficiency should be related
to the relative conformational rigidity of the four-mem-
bered ring and to the presence of a chirotopic10 phospho-
rus atom. The chirotopic phosphorus centre in 1 creates a
highly asymmetric environment around the metal atom –
just as if it were stereogenic (see Figure 2) – while avoid-
ing the usual drawbacks of P-chiral ligands, e.g. challeng-
ing synthesis and easy racemisation.
The trivalent phosphetanes 1–3,6,7 are air sensitive oils,
while 4 and 5 are easy to handle, air stable solids.
The procedures for the preparation of phosphetanes 1–7
are only few, nevertheless representative examples show
the high flexibility of the synthetic approach to enantio-
merically pure, monodentate phosphetanes. These mono-
phosphines should find specific use in reactions which
require monodentate ligands for the generation of catalyt-
ically active species (e.g. palladium-promoted hydrosily-
lation of olefins,11 reduction of allylic carbonates,12 ene-
type carbocyclisations,13 nickel promoted hydrovinyla-
tion,14 etc). Moreover, new applications should emerge
from recent studies showing the peculiar properties of hin-
dered monophosphines in transition metal catalysis. Nota-
bly, tri-tert-butylphosphine, tri-o-tolylphosphine and their
palladacycles, di-tert-butylferrocenylphosphine and dicy-
clohexyl(biaryl)phosphines display very high catalytic ac-
tivities in various palladium- and rhodium-promoted
reactions.15 Phosphetanes should afford potentially use-
ful, chiral analogues of these species. Studies toward the
catalytic applications of chiral monodentate phosphetanes
are in progress.
Figure 2 also shows that, with monodentate phosphetanes
devoid of any functional group, chiral induction should
come from the different, relative sterical hindrance of the
R and R' substituents. Improvement of their efficiency
should result from the choice of phosphorus substituents
(R') with suitable steric properties, however in an unpre-
dictable manner. The sterical hindrance of the phosphorus
substituent can be increased easily by the use of appropri-
Next in this work, P–N heterobidentate, phosphetane
based ligands have been selected as synthetic targets, giv-
Synthesis 2001, No. 14, 2095–2104 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Synthesis of Chiral Phosphetanes
2097
en that aminophosphines represent a well established The yield of borane complex 16 was very low (7%, in the
class of chiral auxiliaries with known application fields. usual conditions of phosphetane synthesis), the major
For instance, carbon–carbon bond formations via allylic product of the cyclisation reaction being the 1-(2-ami-
substitutions (Pd) or cross coupling reactions (Ni) should nophenyl)phosphetane 17 (43% yield). Nevertheless,
be mentioned as significant applications.16 Relevant liter- complex 16 was isolated and its structure was unambigu-
ature reports show that in all current chiral aminophos- ously established by X-ray crystallography (Figure 4).
phines the two coordinating centres have different steric
and electronic properties, so that both effects are superim-
posed and, therefore, not distinguishable.17 Consequently,
it would be worthwhile to prepare and study bidentate P–
N ligands having comparable steric environments at the
two coordinating centres. Purely electronic effects will be
evidenced in catalytic processes by comparing them with
the analogous, C2-symmetrical N–N or P–P bidentate
ligands. Following this concept we designed the synthesis
of azetidino-phosphetanes with an overall “C2-symmet-
ric” geometric structure and especially that of III and IV
(Figure 3), which are analogues of the CnrPHOS [chiral
bis(phosphetano)benzenes]1a–c and BPE-4 [1,2-bis(phos-
phetano)ethanes]1f ligands previously reported.
R
P
Figure 4 ORTEP drawing of 16. Selected bond distances (Å): P–
R
R
R
R
C(1) 1.855(2), P–C(3) 1.849(2), C(1)–C(2) 1.561(2), C(2)–C(3)
1.550(2), P–C(7) 1.814(2), N–C(4) 1.504(2), N–C(6) 1.486(2), C(4)–
C(5) 1.549(2), C(5)–C(6) 1.545(2), N–C(8) 1.395(2). Selected bond
angles (°): C(1)–P–C(3) 78.33(7), P(1)–C(3)–C(2) 87.3(1), P–C(1)–
C(2) 86.8(1), C(3)–C(2)–C(1) 97.5(1), C(4)–N–C(6) 91.7(1), N–
C(4)–C(5) 87.4(1), N–C(6)–C(5) 88.2(1), C(4)–C(5)–C(6) 87.8(1).
N
P
N
R
R
R
IV
III
Figure 3 Structures of azetidino-phosphetanes III and IV
The azetidine ring displays a nearly square-planar geom-
etry with N–C and C–C bond distances varying from 1.48
Å to 1.54 Å and intracyclic bond angles between 87.4°
and 91.7°, while the phosphetane ring shows a very dis-
torted geometry with long P–C bonds (1.85 Å, vs. 1.55Å
for C–C), acute C–P–C angle (78.3°) and large C–C–C in-
tracyclic angle (97.5°).
Comparison between the CnrPHOS or BPE-4 ligands and
the corresponding azetidino-phosphetanes III and IV, re-
spectively, would hopefully afford information on the role
of electronic effects in selected catalytic reactions.
The first azetidino-phosphetane, 15, was prepared from
(2-aminophenyl)phosphine18 and the cyclic sulfate of
(S,S)-pentane-2,4-diol, following the usual cyclisation
procedure (Scheme 2).
The azetidino-phosphetane 15 was released quantitatively
from its borane complex by reaction with 1.5 equivalents
of DABCO. It has been unambiguously characterised, but
the conditions of its synthesis need to be improved before
applications in asymmetric catalysis would be reasonably
envisaged. According to the reagents used in Scheme 2,
the limiting step is the cyclisation reaction on nitrogen
which is impeded by the low nucleophilic character of the
lithium arylamide. Incidentally, it must be noted that the
attempted synthesis of the analogous pyrrolidine-phos-
pholane by the same approach led to 18 (Figure 5) in
equally low yield (less than 5%).
Me
H3B
BH3
PH2
NH2
Me
P
Me
N
i.
P
+
Me
Me
Me
NH2
(R,R)-17 43%
(R,R)-16 7%
DABCO
45°C, 2h
Me
Me
P
N
Me Me
2. s-BuLi 3. BH3 SMe2
(R,R
)-15
BH3
SO2
O
N
P
O
Reagents: i. 1. n-BuLi,
Me
Me
Scheme 2
18
Figure 5 Structure of the pyrrolidine analogue 18
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2098
A. Marinetti et al.
PAPER
The (2-azetidinoethyl)phosphetanes IV, are available
through a multistep procedure which avoids the use of the
highly volatile and potentially toxic 2-aminoethylphos-
phine. As shown in Scheme 3, the method implied forma-
tion of the azetidine and phosphetane rings in two separate
steps. At first, the (R,R)-2,4-dimethylazetidinium acetate
was prepared according to the published procedure19 and
was reacted then with 2-bromoethylphosphonate20 to af-
ford 19. The phosphonate function of 19 served as precur-
sor for the primary phosphino group which was required
for phosphetane syntheses. The cyclisation reaction be-
tween 20 and (S,S)-2,4-pentanediol cyclic sulfate, fol-
lowed
by
borane
addition,
led
to
the
(azetidinoethyl)phosphetane as its bis-borane complex 22
in acceptable yield (25%, under non-optimised condi-
tions).
Figure 6 ORTEP drawing of 22. Selected bond distances (Å): P–
C(1) 1.828(2), P–C(3) 1.837(2), C(1)–C(2) 1.550(3), C(2)–C(3)
1.546(3), P–C(6) 1.809(2), N–C(8) 1.536(3), N–C(10) 1.574(2),
C(8)–C(9) 1.531(3), C(9)–C(10) 1.530(3), N–C(7) 1.488(2). Selected
bond angles (°): C(1)–P–C(3) 79.6(1), P(1)–C(3)–C(2) 87.7(1), P–
C(1)–C(2) 87.9(1), C(3)–C(2)–C(1) 98.5(1), C(8)–N–C(10) 88.0(1),
N–C(8)–C(9) 90.2(2), N–C(10)–C(9) 88.8(2), C(8)–C(9)–C(10)
89.8(1).
i.
+
AcO-
ii.
NH2
N
N
P(O)(OEt)2
PH2
19
20
iii.
expected to afford air-stable, easy to handle analogues of
21.
BH3.SMe2
P
25%
P
H3B
In summary, this work proves the versatility of the syn-
thetic approach to chiral phosphetanes from primary
phosphines and enantiomerically pure 1,3-diol deriva-
tives. Especially, its efficiency for the preparation of fer-
rocenyl substituted phosphetanes with tunable steric
properties has been demonstrated. Moreover, the first ex-
amples of azetidinophosphetanes have been described,
which represent a new class of P–N bidentate ligands.
Utility of all these ligands in asymmetric catalysis will be
reported later.
BH3
Dabco
N
N
65°C, 6h
22
21
Reagents: i. BrCH2CH2P(O)(OEt)2, NEt3, 90°C, 70%
ii. LiAlH4, ether, 18h, 63%
SO2
O
O
3. BH3 SMe2
iii. 1. n-BuLi,
Me
2. s-BuLi
Me
Scheme 3
The structure of the (azetidinoethyl)phosphetane 22 was
established by X-ray crystallography (see Figure 6).
All reactions were performed under inert atmosphere (Ar). NMR
spectra were recorded on either a Bruker AM 400 or a Bruker AM
200 spectrometer. Selected NMR data are given hereafter for all
new compounds. o-Tolylphosphine21 and o-anisylphosphine22 were
prepared by reduction of the corresponding diethylphosphonate
with a LiAlH4/TMSCl mixture.23 Diethyl phosphonates were pre-
pared by NiCl2-catalysed coupling of the corresponding aryl bro-
mides with triethyl phosphite.24,25 Ferrocenylphosphine was
The phosphetane and azetidine rings in 22 are structurally
very similar to the corresponding rings in 16. In both com-
pounds the structural parameters - bond angles and dis-
tances - of the azetidine ring differ significantly from
those of the phosphetane unit thus creating a slightly dif-
ferent steric environment around the phosphorus and ni- obtained from ferrocene in a two-step reaction: ferrocene was lithi-
ated in THF at –78 °C with t-BuLi (1 equiv)/t-BuOK (0.12 equiv)26
and reacted then with ClP(OEt)2. The crude ferrocenylphosphonite
trogen centres respectively. This must be taken into
account in further studies, when comparing the catalytic
was reduced then with LiAlH4/TMSCl (THF, 12 h at r.t.) to give the
properties of these P–N bidentate ligands with the corre-
primary phosphine which was purified by filtration on a short alu-
sponding, symmetric diphosphines or diamines.
mina column (Et2O as eluent).27 Ferrocenylmethylphosphine was
prepared according to the literature procedure.28
Decomplexation of 22 was performed in a sealed NMR
tube, with an excess DABCO and the final (azetidinoeth-
yl)phosphetane 21 was characterised in the crude mixture.
Phosphetane 17 is an extremely air sensitive compound
which requires manipulation in a strictly inert atmosphere.
Previous experiments on the analogous BPE-4 ligands1f
Phosphetane-Borane Complexes 8a–e; General Procedure
A solution of phenylphosphine (0.11 mL, 1.0 mmol) in THF (4 mL)
was cooled to –78 °C and BuLi (3.0 mL, 1.6 M solution in hexane,
2.2 mmol) was added. Once warmed to r.t., the mixture was stirred
for 1 h to afford dilithiated phenylphosphine. The yellow-orange
suggest that air oxidation should be reduced if the phos- suspension was added slowly at –40 °C to a solution of cyclic sul-
fate of the suitable chiral 1,3-diol (1 mmol) in THF (40 mL). After
warming to r.t. and stirring for about 30 min, an excess BH3◊Me2S
(about 2 mmol) was added. After hydrolysis the solvent was evap-
phetane ring bears more bulky substituents. Especially,
the use of cyclohexyl groups as substituents of the rings is
Synthesis 2001, No. 14, 2095–2104 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Synthesis of Chiral Phosphetanes
MS: m/z (%) = 262 (M – BH3, 90), 136 (100).
2099
orated and the residue extracted with Et2O, washed with H2O and
dried (MgSO4). The final products 8 were purified by chromatogra-
phy on an alumina column with a 5% Et2O–cyclohexane mixture as
eluent and were obtained as colourless solids.
Phosphetane-Borane Complexes 9–14; General Procedure
The primary phosphine (1 mmol) was lithiated at –78 °C in THF (5
mL), by addition of BuLi (1.1 equiv). After addition of the 1,3-diol
cyclic sulfate (1.1 equiv, in 20 mL THF), the mixture was warmed
up to r.t. and stirred for about 20 min. (For the synthesis of 9 and 10
the lithiated phosphine was added to a cooled THF solution of the
cyclic sulfate). s-BuLi (1 equiv, 1.3 N solution in hexane) was add-
ed then at –78 °C. The mixture was warmed up to r.t. and treated as
above for the preparation of 8a–e. The synthesis of 14 was per-
formed at 0–25 °C.
(S,S)-2,4-Diisopropyl-1-phenylphosphetane Borane Complex
8b
The (R,R)-2,6-dimethylheptane-3,5-diol cyclic sulfate1b was used in
the synthesis; yield: 50%; [a]D –70 (c 0.5, CHCl3).
31P NMR (CDCl3): d = 43 (br).
1H NMR (C6D6): d = 0.46 (d, J = 6.4 Hz, 3 H, CH3), 0.53 (dd,
J = 6.5, 0.9 Hz, 3 H, CH3), 0.78 (dd, J = 6.3, 1.2 Hz, 3 H, CH3), 0.94
(d, J = 6.1 Hz, 3 H, CH3), 7.0 (m, 3 Harom), 7.8 (m, 2 Harom).
(S,S)-2,4-Diisopropyl-1-(o-tolyl)phosphetane Borane Complex
13C NMR (CDCl3): d = 19.9 (d, J = 11.8 Hz, CH3), 20.3 (d, J = 13.9
Hz, CH3), 21.0 (d, J = 3.3 Hz, CH3), 21.8 (d, J = 4.6 Hz, CH3), 29.1
(d, J = 5.8 Hz, CH), 29.6 (CH), 30.0 (d, J = 15.2 Hz, CH2) 39.8 (d,
J = 38.8 Hz, CH), 42.3 (d, J = 40.0 Hz, CH), 128.1 (d, J = 31.3 Hz,
CP).
10
o-Tolylphosphine and (R,R)-2,2,6,6-tetramethylheptane-3,5-diol
cyclic sulfate were used in this synthesis; yield: 36%; [a]D –13 (c 1,
CHCl3).
31P NMR (CDCl3): d = 41 (JP-B = 55 Hz).
1H NMR (CDCl3): d = 0.75 (d, J = 6.6 Hz, 6 H, CH3), 0.97 (dd,
J = 6.6, 1.2 Hz, 3 H, CH3), 1.02 (d, J = 6.6 Hz, 3 H, CH3),1.8 (m, 1
H), 2.1–2.5 (m, 4 H), 2.56 (s, 3 H, CH3), 2.8 (m, 1 H), 7.1–7.5 (m,
4 H).
MS: m/z = 234 (M – BH3, 100).
Anal. Calcd for C15H26BP: C, 72.60; H, 10.56. Found: C, 72.48; H,
10.74.
13C NMR (CDCl3): d = 19.0 (d, J = 5.7 Hz, CH3), 19.9 (d, J = 14.5
Hz, CH3), 21.6 (d, J = 8.1 Hz, CH3), 22.4 (d, J = 5.3 Hz, CH3), 22.5
(s, CH3), 27.0 (d, J = 12.5 Hz, CH2), 28.1 (d, J = 7.0 Hz, CH), 29.6
(CH), 41.6 (d, J = 36.6 Hz, CH), 42.1 (d, J = 38.8 Hz, CH), 125.8
(d, J = 8.3 Hz, CH), 128.9 (d, J = 26.5 Hz, CP), 130.6 (d, J = 6.8 Hz,
CH), 130.9 (CH), 131.2 (d, J = 8.0 Hz, CH), 141.7 (d, J = 9.9 Hz,
C).
(S,S)-2,4-Dicyclohexyl-1-phenylphosphetane Borane Complex
8c
The (R,R)-1,3-dicyclohexylpropane-1,3-diol cyclic sulfate1b was
used in the synthesis; yield: 86%; [a]D –6 (c 1, CHCl3)
31P NMR (C6D6): d = 59 (br).
13C NMR (C6D6): d = 25.7, 25.9, 26.0, 26.2, 26.3, 26.7 (CH2), 28.4
(d, J = 15.6 Hz, CH2), 30.3 (d, J = 11.1 Hz, CH2), 31.1 (d, J = 13.2
Hz, CH2), 31.7 (CH2), 32.4 (d, J = 4.4 Hz, CH2), 38.4 (d, J = 5.8 Hz,
CH), 38.8 (d, J = 37.9 Hz, CH), 38.9 (CH), 41.1 (d, J = 39.4 Hz,
CH), 129.4 (d, J = 29.8 Hz, CP).
MS: m/z (%) = 248 (M – BH3, 40), 233 (63), 178 (70), 78 (100).
Anal. Calcd for C16H28BP: C, 73.30; H, 10.77. Found: C, 71.48; H,
10.52.
MS (CI): m/z = 346 (M + NH4).
(R,R)-2,4-Dimethyl-1-ferrocenylphosphetane Borane Complex
11
Ferrocenylphosphine and the (S,S)-pentane-2,4-diol cyclic sulfate
were used in this synthesis. The phosphetane borane complex 11
was obtained as a yellow solid in 50% yield; [a]D +130 (c 0.5,
CH2Cl2).
Anal. Calcd for C15H26BP: C, 76.83; H, 10.40. Found: C, 76.35; H,
10.13.
(S,S)-2,4-Dibenzyl-1-phenylphosphetane Borane Complex 8d
The (R,R)-1,5-diphenylpentane-2,4-diol1c cyclic sulfate was used in
the synthesis; yield 82%; [a]D = +75 (c 1, CH2Cl2).
31P NMR (C6D6): d = 48.7 (br).
1H NMR (C6D6): d = 2.2–2.6 (m, 4 H), 2.8–3.3 (m, 4 H), 6.83 (d,
J = 6.5 Hz, 1 H), 7.0–7.5 (m, 14 H).
13C NMR (CDCl3): d = 31.2 (d, J = 14.6 Hz, CH2), 33.5 (d, J = 38.5
Hz, CH), 35.0 (d, J = 38.7 Hz, CH), 36.3 (CH2),127.3 (d, J = 32.2
Hz, CP), 138.5 (d, J = 9.9 Hz, C), 139.7 (d, J = 10.2 Hz, C).
31P NMR (CDCl3): d = 49 (JP-B = 54 Hz).
1H NMR (CDCl3): d = 0.99 (dd, JH-P = 15.6 Hz, J = 7.4 Hz, 3 H,
CH3), 1.45 (dd, JH-P = 18.7 Hz, J = 7.4 Hz, 3 H, CH3), 2.1–2.5 (m, 2
H), 2.5–2.7 (m, 1 H), 2.7–2.9 (m, 1 H), 4.27 (s, 5 H, Cp), 4.42 (br,
1 H), 4.53 (br, 2 H), 4.61 (br, 1 H).
13C NMR (C6D6): d = 15.5 (d, J = 6.4 Hz, CH3), 15.7 (CH3), 28.1 (d,
J = 46.3 Hz, CH), 28.9 (d, J = 43.7 Hz, CH), 35.4 (d, J = 15.5 Hz,
CH2), 69.8 (Cp), 70.9 (CH), 72.0 (d, J = 5.5 Hz, CH), 72.5 (d,
J = 7.6 Hz, CH), 75.1 (d, J = 14.5 Hz, CH).
MS: m/z (%) = 330 (M – BH3, 80), 91 (100).
Anal. Calcd for C23H26BP: C, 80.25; H, 7.61. Found: C, 80.12; H,
7.61.
MS: m/z (%) = 300 (M, 17), 286 (M – BH3, 100).
Anal. Calcd for C15H22BFeP: C, 60.06; H, 7.39. Found: C, 59.73; H,
7.38.
(R,R)-2,4-Di-tert-butyl-1-phenylphosphetane Borane Complex
8e
The (S,S)-2,2,6,6-tetramethylheptane-3,5-diol cyclic sulfate1c was
used in this synthesis; yield: 46%.
(R,R)-2,4-Dimethyl-1-ferrocenylmethylphosphetane Borane
Complex 12a
(Ferrocenylmethyl)phosphine and the (S,S)-pentane-2,4-diol cyclic
sulfate were used in this synthesis. The phosphetane borane com-
plex 12a was obtained as a yellow solid in 72% yield.
31P NMR (C6D6): d = 55 (JP-B = 50 Hz).
1H NMR (C6D6): d = 0.81 (dd, JH-P = 14.6 Hz, J = 7.5 Hz, 3 H,
CH3), 1.05 (dd, JH-P = 17.8 Hz, J = 7.3 Hz, 3 H, CH3), 1.5 (m, 1 H),
1.8 (m, 1 H), 1.9 (m, 1 H), 2.2 (m, 1 H), 2.63 (ABX, JA-B = 14.5 Hz,
31P NMR (C6D6): d = 43 (br).
1H NMR (C6D6): d = 0.61 (s, 9 H, t-C4H9), 1.09 (s, 9 H, t-C4H9),
2.0–2.3 (m, 2 H), 2.6–2.8 (m, 2 H), 7.0 (m, 3 H), 7.9 (m, 2 H).
13C NMR (C6D6): d = 25.1 (d, J = 12.8 Hz, CH2), 27.7 [d, J = 5.9
Hz, C(CH3)3], 28.2 [d, J = 6.2 Hz, C(CH3)3], 33.0 [C(CH3)3], 33.2
[d, J = 6.1 Hz, C(CH3)3], 43.6 (d, J = 35.0 Hz, CH), 48.8 (d,
J = 36.5 Hz, CH), 130.1 (d, J = 28.4 Hz, CP).
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JH-P = 10.9 Hz, 1 H, PCH2), 2.69 (ABX, JH-P = 7.4 Hz, 1 H, PCH2),
3.7–3.8 (m, 3 H, CH), 3.86 (5 H, Cp), 4.1 (br, 1 H, CH).
13C NMR (C6D6): d = 14.8 (d, J = 6.5 Hz, CH3), 15.2 (CH3), 25.0 (d,
J = 13.0 Hz, PCH2), 26.0 (d, J = 39.3, CH), 27.9 (d, J = 37.0, CH),
35.6 (d, J = 15.6 Hz, CH2), 68.0 (CH), 68.5 (CH), 69.2 (Cp), 69.3
(d, J = 1.5 Hz, CH), 69.8 (d, J = 1.9 Hz, CH), 79.5 (C).
31P NMR (CDCl3): d = 57 (JP-B = 49 Hz).
1H NMR (CDCl3): d = 1.22 (dd, JH-P = 17.4 Hz, J = 7.2 Hz, 3 H,
CH3), 1.28 (dd, JH-P = 14.1, 7.5 Hz, 3 H, CH3), 1.2–1.9 (m, 9 H),
2.0–2.4 (m, 3 H), 2.5 (m, 2 H).
13C NMR (C6D6): d = 15.3 (d, J = 6.5 Hz, CH3), 15.6 (CH3), 25.1
(CH2), 25.8 (CH2), 26.1 (d, J = 41.4, PCH), 26.3 (d, J = 11.1 Hz,
CH2), 26.6 (d, J = 11.2 Hz, CH2), 26.8 (CH2), 27.2 (d, J = 39.0 Hz,
PCH), 32.8 (d, J = 18.0, PCH), 35.8 (d, J = 15.5 Hz, CH2).
MS (CI): m/z = 332 (M + NH4).
Anal. Calcd for C16H24BFeP: C, 61.20; H, 7.70. Found: C, 61.15; H,
7.83.
MS: m/z (%) = 184 (M – BH3, 44), 142 (C8H15P, 100).
Anal. Calcd for C11H24BP: C, 66.69; H, 12.21. Found: C, 66.76; H,
12.22.
(S,S)-2,4-Diisopropyl-1-ferrocenylmethylphosphetane Borane
Complex 12b
(Ferrocenylmethyl)phosphine and the (R,R)-2,6-dimethylheptane-
3,5-diol cyclic sulfate were used in this synthesis. The phosphetane
borane complex 12b was obtained as a yellow solid in 40% yield;
[a]D +35 (c 1, CHCl3).
Displacement of Phosphetanes 1–9 from Their Borane
Complexes; General Procedure
The phosphine-borane complex (0.5 mmol) was treated with DAB-
CO (1.1 equiv) in benzene (2 mL) at 45 °C for about 3 h. According
to 31P NMR of the reaction mixture, phosphetanes were displaced
quantitatively from their complexes. They were purified by filtra-
tion under argon on a short alumina column with a cyclohexane–
Et2O mixture (1–2%) as eluent. Note: in a few cases prolonged con-
tact with alumina induced formation of byproducts.
31P NMR (C6D6): d = 53.
1H NMR (C6D6): d = 0.63 (d, J = 6.4 Hz, 3 H, CH3), 0.71 (d, J = 6.5
Hz, 3 H, CH3), 0.85 (d, J = 6.5 Hz, 3 H, CH3), 0.86 (d, J = 6.5 Hz,
3 H, CH3), 1.5–2.1 (m, 6 H), 2.93 (ABX, JA-B = 14.2 Hz, J = 11.2
Hz, 1H, CH2), 2.98 (ABX, J = 7.3 Hz, 1H, CH2), 3.92 (br, 2H, CH),
3.98 (s, 5H, Cp), 4.01 (br, 1H, CH), 4.32 (br, 1H, CH).
13C NMR (C6D6): d = 20.3 (d, J = 11.9 Hz, CH3), 20.7 (d, J = 12.5
Hz, CH3), 22.2 (d, J = 4.2 Hz, CH3), 22.4 (CH3), 25.4 (d, J = 15.4
Hz, PCH2), 29.5 (CH), 29.9 (CH), 30.4 (d, J = 12.6 Hz, CH2), 38.5
(d, J = 36.3 Hz, CH), 41.2 (d, J = 37.5 Hz, CH), 68.1 (CH), 68.7
(CH), 69.4 (Cp), 69.7, CH), 70.5 (CH), 79.8 (C).
(S,S)-2,4-Diisopropyl-1-phenylphosphetane (1b)
Colourless oil; [a]D –26 (c 0.5, CH2Cl2).
31P NMR (C6D6): d = 21.6.
1H NMR (C6D6): d = 0.61 (d, J = 6.5 Hz, 3 H, CH3), 0.67 (d, J = 6.4
Hz, 3 H, CH3), 0.97 (d, J = 6.0 Hz, 3 H, CH3), 1.09 (d, J = 6.2 Hz,
3 H, CH3), 1.3 (m, 1 H), 1.7–2.1 (m, 3 H), 2.3–2.7 (m, 2 H), 7.0 (3
H), 7.6 (2 H).
13C NMR (C6D6): d = 19.4 (d, J = 4.6 Hz, CH3), 20.7 (d, J = 6.1 Hz,
CH3), 20.8 (d, J = 6.8 Hz, CH3), 21.2 (d, J = 12.4 Hz, CH3), 30.3 (d,
J = 3 Hz, CH), 31.7 (d, J = 19.0 Hz, CH), 33.8 (d, J = 2.7 Hz, CH2),
35.7 (d, J = 8.0 Hz, CH), 37.9 (d, J = 5.0 Hz, CH), 137.3 (d, J = 34.2
Hz, CP).
Anal. Calcd for C20H32BFeP: C, 64.91; H, 8.71. Found: C, 64.96; H,
8.79.
(S,S)-1-(o-Anisyl)-2,4-diisopropylphosphetane Borane
Complex 13
o-Anisylphosphine and the (R,R)-2,6-dimethylheptane-3,5-diol cy-
clic sulfate were used in this synthesis. The phosphetane borane
complex 13 was obtained as a colourless solid in 58% yield;
[a]D –43 (c 1, CHCl3).
(S,S)-2,4-Dicyclohexyl-1-phenylphosphetane (1c)
Colourless solid.
31P NMR (C6D6): d = 21.5.
13C NMR (C6D6): d = 26.0, 26.2, 26.69, 26.72, 26.8, 27.2 (CH2),
30.0 (d, J = 4.6 Hz, CH2), 31.45, 31.48, 31.51, 31.61, 31.64, 31.77
(CH2), 32.67 (d, J = 2.4Hz, CH2), 35.0 (d, J = 7.8 Hz, CH), 36.7 (d,
J = 4.9 Hz, CH), 39.7 (d, J = 3.4 Hz, CH), 41.2 (d, J = 17.2 Hz,
CH), 137.6 (d, J = 34.6 Hz, CP).
31P NMR (C6D6): d = 43 (JP-B = 62 Hz).
1H NMR (CDCl3): d = 0.61 (d, J = 6.5 Hz, 3 H, CH3), 0.79 (d,
J = 6.6 Hz, 3 H, CH3), 0.90 (d, J = 6.5 Hz, 3 H, CH3), 0.91 (dd,
J = 6.5, 1.3 Hz, 3 H, CH3), 1.9–2.0 (m, 1 H), 2.1–2.2 (m, 1 H), 2.3–
2.6 (m, 3 H), 2.8–2.9 (m, 1 H) 3.91 (s, 3 H, OCH3), 6.94 (dd, J = 8.1
Hz, JH-P = 3.2 Hz, 1 H), 7.05 (tt, J = 7.4, 1.4 Hz, 1 H), 7.49 (tm,
J = 7.4 Hz, 1 H), 7.84 (ddd, JH-P = 12.7 Hz, J = 7.6 Hz, J = 1.7 Hz,
1 H).
(S,S)-2,4-Dibenzyl-1-phenylphosphetane (1d)
Colourless oil; [a]D +75 (c 0.5, CH2Cl2).
31P NMR (C6D6): d = 21.2.
1H NMR (C6D6): d = 2.3 (m, 2 H), 2.5 (m, 1 H), 2.6 (m, 1 H), 2.7–
2.8 (m, 2 H), 2.9–3.1 (m, 2 H), 6.9–7.4 (C6H5).
13C NMR (C6D6): d = 30.0 (CH), 32.6 (d, J = 10.0 Hz, CH), 34.0
(CH2), 38.1 (d, J = 3.6 Hz, CH2), 40.9 (d, J = 20.7 Hz, CH2), 137.9
(d, J = 34.3 Hz, C), 140.8 (d, J = 3.5 Hz, C), 141.4 (d, J = 8.3 Hz,
C).
13C NMR (CDCl3): d = 20.1 (d, J = 10.9 Hz, CH3), 20.4 (d, J = 15.4
Hz, CH3), 21.6 (d, J = 5.2 Hz, CH3), 22.1 (d, J = 4.4 Hz, CH3),
29.6–29.9 (CH, CH2), 40.4 (d, J = 39.5 Hz, PCH), 43.0 (d, J = 40.9
Hz, CH), 55.2 (OCH3), 110.9 (d, J = 3.6 Hz, CH), 117.0 (d, J = 26.5
Hz, C), 121.2 (d, J = 1.5 Hz, CH), 133.5 (CH), 135.6 (d, J = 11.5
Hz, CH), 161.5 (C).
MS: m/z (%) = 264 (M – BH3, 48), 138 (AnisylP, 100).
Anal. Calcd for C16H28BOP: C, 69.08; H, 10.15. Found: C, 68.94;
H, 10.22.
(R,R)-1-Cyclohexyl-2,4-dimethylphosphetane Borane Complex
14
(R,R)-2,4-Di-tert-butyl-1-phenylphosphetane (1e)
Colourless oil; [a]D –98 (c 0.5, CH2Cl2).
Cyclohexylphosphine and the (S,S)-pentane-2,4-diol cyclic sulfate
were used in this synthesis. The deprotonation steps were per-
formed at 0–25 °C. The reaction mixture was stirred overnight at r.t.
before addition of the BH3◊SMe2 complex. The phosphetane borane
complex 14 was obtained as a colourless solid in 73% yield;
[a]D +6 (c 0.5, CHCl3).
31P NMR (C6D6): d = 17.4.
1H NMR (C6D6): d = 0.68 [s, 9 H, t-C4H9], 1.09 (s, 9 H, t-C4H9),
2.3–2.5 (m, 3 H), 2.6–2.8 (m, 1 H), 7.1 (m, 3 H, C6H5), 7.7 (m, 2 H,
C6H5).
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Synthesis of Chiral Phosphetanes
2101
13C NMR (C6D6): d = 27.7 [C(CH3)3], 27.8 [C(CH3)3], 28.3 (CH2),
32.3 [d, J = 13.9 Hz, C(CH3)3], 34.3 [d, J = 3.8 Hz, C(CH3)3], 39.1
(d, J = 7.0 Hz, CH), 42.3 (CH), 138.1 (d, J = 37.0 Hz, C).
1H NMR (C6D6): d = 0.69 (d, J = 6.6 Hz, 3 H, CH3), 0.83 (d, J = 6.4
Hz, 3 H, CH3), 0.97 (d, J = 6.3 Hz, 3 H, CH3), 1.07 (d, J = 6.5 Hz,
3 H, CH3), 1.5–1.6 (m, 1 H), 1.9–2.2 (m, 3 H), 2.3–2.4 (m, 1 H),
2.4–2.6 (m, 1 H), 3.30 (s, 3 H, OCH3), 6.50 (ddd, J = 8.2, 3.9, 0.7
Hz, 1 H, CH), 6.94 (td, J = 7.4, 1.1 Hz, 1 H, CH), 7.14 (td, J = 7.8,
1.5 Hz, 1 H, CH), 7.53 (ddd, J = 7.4, 3.4, 1.7 Hz, 1 H, CH).
13C NMR (C6D6): d = 19.8 (d, J = 3.4 Hz, CH3), 20.8 (d, J = 10.2
Hz, CH3), 21.5 (d, J = 11.2 Hz, CH3), 21.8 (CH3), 30.1 (d, J = 3.9
Hz, CH), 31.8 (CH2), 32.4 (d, J = 20.1 Hz, CH), 36.6 (d, J = 6.9 Hz,
CH), 38.4 (CH), 54.8 (OCH3), 110.1 (CH), 121.0 (CH), 126.6 (d,
J = 39.6 Hz, PC), 129.7 (CH), 132.1 (CH), 161.8 (d, J = 13.8 Hz,
CH).
MS: m/z (%) = 262 (M, 60), 247 (M – Me, 100).
(S,S)-2,4-Diisopropyl-1-(o-tolyl)phosphetane (3)
Colourless oil; [a]D –89 (c 0.5, CH2Cl2).
31P NMR (C6D6): d = 2.4.
1H NMR (C6D6): d = 0.61 (d, J = 6.5 Hz, 3 H, CH3), 0.76 (d, J = 6.6
Hz, 3 H, CH3), 1.03 (d, J = 6.6 Hz, 3 H, CH3), 1.07 (d, J = 6.6 Hz,
3 H, CH3), 1.6 (m, 1 H), 1.9–2.5 (m, 5 H), 2.61 (Ar-CH3), 7.0–7.2
(m, 3 H), 7.7 (m, 1 H).
13C NMR (C6D6): d = 19.9 (d, J = 3.2 Hz, CH3), 20.6 (d, J = 10.7
Hz, CH3), 21.1 (d, J = 10.3 Hz, CH3), 21.4 (Ar-CH3), 21.5 (d,
J = 23.4, CH3), 29.6 (d, J = 4.1 Hz, CH), 31.1 (CH2), 33.2 (d,
J = 19.5 Hz, CH), 37.5 (CH), 37.9 (d, J = 7.4 Hz, CH), 136.4 (d,
J = 37.2 Hz, C), 142.8 (d, J = 24.5, C).
(R,R)-1-Cyclohexyl-2,4-dimethylphosphetane (7)
[a]D +18 (c 1, CH2Cl2).
31P NMR (CDCl3): d = 28.1.
1H NMR (C6D6): d = 1.07 (t, JH-P = J = 6.9 Hz, 3 H, CH3), 1.24 (dd,
JH-P = 16.0, J = 7.2 Hz, 3 H, CH3).
(R,R)-2,4-Dimethyl-1-ferrocenylphosphetane (4)
Yellow-orange solid; [a]D +33 (c 1, CHCl3).
31P NMR (C6D6): d = 18.4.
1H NMR (C6D6): d = 0.88 (dd, JH-P = 8.2 Hz, J = 6.9 Hz, 3 H, CH3),
1.42 (dd, JH-P = 17.9 Hz, J = 7.2 Hz, 3 H, CH3), 2.3–2.5 (m, 4 H),
4.06 (5 H, Cp), 4.17 (br, 3 H), 4.30 (br, 1 H).
13C NMR (C6D6): d = 17.3 (d, J = 3.9 Hz, CH3), 20.8 (d, J = 24.1
Hz, CH3), 23.3 (d, J = 6.9 Hz, CH), 24.6 (d, J = 11.7 Hz, CH), 39.6
(CH2), 69.0 (Cp), 70.7 (CH), 70.8 (CH), 71.5 (d, J = 7.0 Hz, CH),
74.6 (d, J = 32.4 Hz, CH), 76.5 (d, J = 32.6 Hz, CH).
13C NMR (C6D6): d = 15.4 (d, J = 4.3 Hz, CH3), 20.2 (d, J = 20.1
Hz, CH3), 20.6 (d, J = 2.9 Hz, CH), 24.2 (d, J = 8.0 Hz, CH), 25.6
(d, J = 8.0 Hz, CH2), 25.8 (CH2), 26.1 (d, J = 9.1 Hz, CH2), 27.4 (d,
J = 14.1 Hz, CH2), 30.2 (d, J = 18.0 Hz, CH2), 33.3 (d, J = 24.2,
PCH), 38.0 (CH2).
(COD)Rh(L*)2PF6 complexes (L* = 1a–d); General Procedure
The rhodium complexes were prepared by adding (COD)2RhPF6
(0.5 equiv) to a solution of phosphetane (0.5 mmol) in CH2Cl2 (2
mL). The pure complexes were recovered after crystallisation from
CH2Cl2–Et2O mixtures and fully characterised. Some selected data
are given below.
(R,R)-2,4-Dimethyl-1-ferrocenylmethylphosphetane (5a)
Yellow-orange solid.
31P NMR (C6D6): d = 25.5.
1H NMR (C6D6): d = 1.02 (dd, JH-P = 10.4 Hz, J = 7.5 Hz, 3 H,
CH3), 1.22 (dd, JH-P = 16.5, J = 7.4 Hz, 3 H, CH3), 1.85 (m, 1 H),
2.1–2.4 (m, 3 H), 2.76 (AB, 2 H, CH2), 3.95 (m, 2 H, CH), 4.0 (m,
2 H, CH), 4.06 (5 H, Cp).
13C NMR (C6D6): d = 16.2 (d, J = 3.8 Hz, CH3), 20.4 (d, J = 21.4
Hz, CH3), 21.8 (d, J = 4.2 Hz, CH), 24.8 (d, J = 30.1 Hz, PCH2),
25.4 (d, J = 8.0 Hz, CH), 39.2 (CH2), 67.6, 67.8 (CH), 69.1 (Cp),
85.7 (d, J = 13.0 Hz, C).
(COD)Rh[(S,S)-1a]2PF6
[a]D +66 (c 0.2, CHCl3).
31P NMR (CDCl3): d = 67.4 (d, JP-Rh = 144 Hz).
(COD)Rh[(S,S)-1b]2PF6
[a]D = +134 (c 0.2, CHCl3).
31P NMR (CDCl3): d = 53.6 (d, JP-Rh = 145 Hz).
(COD)Rh[(S,S)-1c]2PF6
[a]D +123 (c 1, CHCl3).
31P NMR (CDCl3): d = 54.8 (d, JP-Rh = 143 Hz).
(S,S)-2,4-diisopropyl-1-ferrocenylmethylphosphetane (5b)
Yellow-orange solid; [a]D +116 (c 0.5, CH2Cl2).
31P NMR (C6D6): d = 22.2.
Anal. Calcd for C50H74F6P3Rh: C, 60.97; H, 7.57. Found: C, 60.97;
H, 7.40.
(COD)Rh[(S,S)-1d]2PF6
1H NMR (C6D6): d = 0.76 (d, J = 6.2 Hz, 3 H, CH3), 0.84 (d, J = 6.2
Hz, 3 H, CH3), 0.92 (d, J = 6.5 Hz, 3 H, CH3), 1.05 (d, J = 6.6 Hz,
3 H, CH3), 1.7–1.9 (m, 4 H), 2.4–2.5 (m, 1 H), 2.6–2.7 (m, 1 H),
2.96 (2 H, CH2), 3.96 (br, 2 H, CH), 4.08 (?, 5 H, Cp), 4.12 (br, 1 H,
CH), 4.16 (br, 1 H, CH).
13C NMR (C6D6): d = 19.8 (d, J = 4.6 Hz, CH3), 20.9 (d, J = 8.8 Hz,
CH3), 21.2 (d, J = 4.6 Hz, CH3), 21.3 (d, J = 4.2 Hz, CH3), 24.1 (d,
J = 28.2 Hz, PCH2), 30.4 (d, J = 2.3 Hz, CH), 31.4 (d, J = 16.4 Hz,
CH), 33.8 (d, J = 2.7 Hz, CH2), 35.8 (d, J = 5.7 Hz, CH), 36.5 (d,
J = 6.5 Hz, CH), 67.5, 67.8, 69.0 (CH), 69.1 (Cp), 69.3 (CH), 85.9
(d, J = 13.7 Hz, C).
31P NMR (CD2Cl2): d = 65.3 (d, JP-Rh = 147 Hz).
Anal. Calcd for C54H58F6P3Rh: C, 63.78; H, 5.75. Found: C, 60.47;
H, 6.18.
Rhodium Complexes as Catalysts in Model Hydrogenation
Experiments; General Procedure
Hydrogenations of a-acetamido cinnamic acids were performed an
a 1 mmol scale, in MeOH at r.t., with 1% rhodium catalyst under 3–
5 bar of H2. Reactions were allowed to proceed overnight. Quanti-
tative conversions were obtained. Enatiomeric excesses (80% with
phosphetane 1a, 10% with 1b and 86% with 1d) were measured on
the corresponding methyl esters by HPLC (OD-H column).
Anal Calcd for C20H29FeP: C, 67.43; H, 8.20. Found: C, 66.06; H,
8.32.
Aminophosphetane Borane Complexes 16 and 17
(S,S)-1-(o-Anisyl)-2,4-diisopropylphosphetane (6)
[a]D –240 (c 0.5, CH2Cl2).
31P NMR (C6D6): d = 9.1.
To a solution of 2-(aminophenyl)phosphine (510 mg, 4 mmol) in
THF (8 mL) cooled to –78 °C was added BuLi (2.5 N in hexane, 3.6
mL, 2.2 equiv). After warming to r.t. and stirring for 30 min, the re-
sulting solution was added to a solution of (S,S)-pentane-2,5-diol
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A. Marinetti et al.
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cyclic sulfate (1.3 g, 2 equiv) in THF (150 mL) at –78 °C. After 3 h
at r.t., s-BuLi (1.3 N in hexane, 6.9 mL) was added at –78 °C. The
mixture was stirred overnight at r.t., then an excess of BH3◊SMe2 (4
equiv) was added. After hydrolysis, evaporation and extraction with
Et2O, the mixture was separated by column chromatography on alu-
mina with a cyclohexane–Et2O gradient.
a short alumina column under argon with Et2O as eluent; colourless
oil.
31P NMR (C6D6): d = 19.0.
1H NMR (C6D6, at 55 °C): d = 1.11 (d, J = 6.0 Hz, 6 H, CH3), 1.12
(t, JH-P = J = 7.1 Hz, 3 H, CH3), 1.31 (dd, JH-P = 16.7 Hz, J = 7.0 Hz,
3 H, CH3), 1.7 (br, 2 H, CH2), 2.07 (dt, JH-P = 33.4 Hz, J = 9.5 Hz,
1 H, CH2), 2.3 (m, 1 H), 2.4 (m, 1 H), 2.8 (m, 1 H), 4.3 (br, 2 H,
NCH), 6.53 (dd, J = 8.0, 3.2 Hz, 1 H, CH), 6.92 (t, J = 7.3 Hz, 1 H,
CH), 7.15 (1H), 7.24 (m, 1H).
13C NMR (C6D6): d = 15.9 (d, J = 5.3 Hz, CH3), 18 (br, CH3), 19.3
(d, J = 21.4 Hz, CH3), 24.0 (d, J = 2.3 Hz, CH), 27.4 (d, J = 7.6 Hz,
CH), 31.1 (CH2), 35.9 (CH2), 54.0 (br, NCH), 146.8 (d, J = 10.7 Hz,
CN).
(R,R)-1-{2-[(R,R)-2,4-Dimethylazetidino]phenyl}-2,4-
dimethylphosphetane Borane Complex 16
Colourless solid; yield: 83 mg (7%); Rf 0.7 (cyclohexane–Et2O,
90:10); [a]D –234 (c 1, CHCl3).
31P NMR (CDCl3): d = 48 (JP-B = 53 Hz).
1H NMR (CDCl3, at 55 °C): d = 1.19 (d, J = 6.1 Hz, 6 H, 3 H, CH3),
1.40 (dd, JH-P = 17.4 Hz, J = 6.9 Hz, 3 H, CH3), 1.42 (dd, JH-P = 14.8
Hz, J = 7.4 Hz, 3 H, CH3), 2.0 (br, 2 H), 2.06 (dt, JH-P = 47.2 Hz,
J = 10.7 Hz, 1 H, CH2), 2.5 (m, 1 H, CH2), 2.63 (m, J = 6.4 Hz, 1
H), 2.98 (m, 1 H), 4.42 (m, J = 6.2 Hz, 2 H, NCH), 6.71 (dd, J = 7.4,
4.0 Hz, 1 H), 6.93 (t, J = 7.4 Hz, 1 H), 7.11 (1 H), 7.30 (1 H).
13C NMR (CDCl3): d = 14.3 (CH3), 16.4 (d, J = 8.0 Hz, CH3), 18.9
(br, 2 CH3), 30.6 (d, J = 37.7, CH), 32.2 (d, J = 42.6 Hz, CH), 32.5
(CH2), 35.6 (d, J = 12.5 Hz, CH2), 116.1 (d, J = 5.6 Hz, CH), 120.3
(d, J = 9.2, CH), 122.9 (d, J = 26.9 Hz, C), 130.8 (CH), 131.4 (d,
J = 8.4 Hz, CH), 148.8 (d, J = 3.2 Hz, C).
(R,R)-1-{2-[(R,R)-2,5-Dimethylpyrrolidino]phenyl}-2,5-
dimethylphospholane Borane Complex 18
31P NMR (C6D6): d = 42 (JP-B = 65 Hz).
1H NMR (C6D6): d = 0.60 (d, J = 6.5 Hz, 3 H, CH3), 0.68 (dd, JH-
P = 13.5 Hz, J = 7.3 Hz, 3 H, CH3), 0.92 (d, J = 6.0 Hz, 3 H, CH3),
1.42 (dd, JH-P = 15.3 Hz, J = 7.0 Hz, 3 H, CH3), 1.2–1.8 (6 H), 2.0
(m, 1 H), 2.2 (m, 1 H), 2.5 (m, 1 H), 3.0 (m, 1 H), 3.3 (m, 1 H), 4.2
(m, 1 H), 6.9 (m, 2 H), 7.0 (m, 1 H), 7.7 (m, 1 H).
13C NMR (C6D6): d = 14.9 (d, J = 3.4 Hz, CH3), 15.8 (d, J = 4.5 Hz,
CH3), 17.0 (CH3), 19.3 (CH3), 30.1 (d, J = 34.9 Hz, PCH), 30.8
(CH2), 32.4 (CH2), 32.9 (d, J = 7.8 Hz, CH2), 33.5 (d, J = 4.2 Hz,
CH2), 35.5 (d, J = 36.4 Hz, PCH), 53.0 (NCH), 60.2 (NCH), 123.8
(d, J = 9.5 Hz, CH), 125.4 (d, J = 5.3 Hz, CH), 130.9 (d, J = 1.5 Hz,
CH), 136.0 (d, J = 9.1 Hz, CH), 151.8 (C).
MS: m/z = 261 (M – BH3, 25), 190 (100).
Anal. Calcd for C16H27BNP: C, 69.84; H, 9.89; N, 5.09. Found: C,
69.74; H, 9.94; N, 5.09.
(R,R)-1-(2-Aminophenyl)-2,4-dimethylphosphetane Borane
Complex 17
Colourless solid; yield: 360 mg (43%); Rf 0.25 (cyclohexane–Et2O,
90:10); [a]D –93 (c 1, CHCl3).
MS (CI): m/z = 304 (M + H, 100%).
2-[(R,R)-2,4-Dimethylazetidino]ethylphosphine (20)
31P NMR (C6D6): d = 45 (JP-B = 39 Hz).
A solution containing (R,R)-2,4-dimethylazetidinium acetate19
(2.1g, 14 mmol), diethyl 2-bromoethylphosphonate (5.1g, 21
mmol), Et3N (4 mL) and toluene (4 mL) was heated overnight at
80 °C. The crude mixture was diluted with Et2O and the ammonium
salt was removed by filtration. After evaporation, the residue was
distilled at 60 °C (2 mbar) to remove the excess of diethyl 2-bromo-
ethylphosphonate and the main side-product, diethyl vinylphospho-
nate. The residue (2.5 g) contained mainly 19, which was used for
the next step without further purification.
1H NMR (CDCl3, at 55 °C): d = 0.79 (dd, J = 15.1, 7.3 Hz, 3 H,
CH3), 1.20 (dd, J = 18.5, 7.0 Hz, 3 H, CH3), 1.6 (ddt, JH-P = 36.4 Hz,
J = 9.9 Hz, J = 3.1 Hz, 1 H, CH2), 2.2 (m, 1 H), 2.4 (m, 1 H), 2.6 (m,
1 H), 4.04 (br, 2 H, NH2), 6.1 (m, 1 H), 6.6 (m, 1 H), 6.9 (m, 1 H),
7.0 (m, 1 H).
13C NMR (C6D6): d = 14.6 (CH3), 15.4 (d, J = 7.2 Hz, CH3), 26.6 (d,
J = 41.6 Hz, CH), 28.8 (d, J = 38.9 Hz, CH), 35.0 (d, J = 14.1 Hz,
CH2), 112.0 (d, J = 31.2 Hz, C), 116.7 (d, J = 5.7 Hz, CH), 118.3 (d,
J = 8.0 Hz, CH), 131.3 (d, J = 4.6 Hz, CH), 132.3 (d, J = 2.3 Hz,
CH), 150.3 (d, J = 6.9 Hz, C).
19
31P NMR (CDCl3): d = 30.2.
1H NMR (CDCl3): d = 1.29 (t, J = 6.5 Hz, 6 H, CH2CH3), 1.29 (d,
J = 6.5 Hz, 6 H, CH3), 2.0 (m, 4 H), 2.9 (m, 2 H), 3.83 (m, J = 6.7
Hz, 2 H, NCH), 4.06 (m, J = 7.0 Hz, 4 H, OCH2).
MS: m/z (%) = 193 (M – BH3, 85), 136 (100).
Anal. Calcd for C11H19BNP: C, 63.81; H, 9.25; N, 6.76. Found: C,
64.10; H, 9.44; N, 6.39.
13C NMR (CDCl3): d = 16.2 (d, J = 5.9 Hz, CH3), 17.3 (CH3), 23.6
(d, J = 139.3 Hz, CH2P), 32.2 (CH2), 42.2 (CH2), 57.2 (NCH), 61.7
(d, J = 6.2 Hz, OCH2).
X-Ray Structure Determination of 16
Molecular formula: C16H27BNP. Molecular weight 275.17. Colour-
less cube, dimensions: 0.20 ¥ 0.20 ¥ 0.20 mm; crystal system: tri-
clinic, space group: P21. a(Å) = 8.251(4), b(Å) = 9.481(2),
An Et2O solution of the crude phosphonate 19 was added to a cooled
(–78 °C) suspension of LiAlH4 (2.3 g, 6 equiv) in Et2O (40 mL).
The mixture was warmed up, stirred overnight at r.t., then hydroly-
sed with H2O and NaOH (20% aq solution) until a colourless solid
separated from the organic phase. The organic phase was trans-
ferred under argon in a round bottomed flask, dried successively
with MgSO4 and CaH2, filtered on a Celite pad and distilled in a
Kugelrohr apparatus (70 °C, 0.3 bar) to afford 0.91 g (63%) of 20
containing small amounts (<10%) of side products; colourless oil.
c(Å) = 11.121(2),
a(°) = 90.001(10),
b(°) = 104.992(15)
g(°) = 90.073(15), V(Å3) = 840.4(4), Z = 2; d (gcm–3) = 1.087. Dif-
fractometer KappaCCD, X-Ray source Mo Ka (l = 0.71070 Å),
graphite monochromator. T(K) 150.0(1). Reflections measured:
4971. Independent reflections: 3096. Refinement type Fsqd. Hydro-
gen atoms mixed Parameters refined 176. wR2 0.0811; R1 0.0287;
GoF 1.041. D peak/hole (e Å–3) 0.259/–0.175.
(R,R)-1-{2-[(R,R)-2,4-Dimethylazetidino]phenyl}-2,4-
dimethylphosphetane (15)
Displacement of phosphetane 15 from its borane complex was
achieved by reacting 16 with DABCO (1.5 equiv) in benzene solu-
tion at 45 °C for 2 h. The crude mixture was purified by filtration on
31P NMR (CDCl3): d = –143.9.
1H NMR (CDCl3): d = 1.15 (d, J = 6.4 Hz, 6 H, CH3), 1.5 (m, 2 H,
PCH2), 1.81 (t, J = 6.4 Hz, 2 H, CH2-azet), 2.5–2.7 (m, 2 H), 2.60
(m, JH-P = 195.0 Hz, J = 7.1 Hz, 2 H, PH2), 3.5 (m, 2 H, NCH).
Synthesis 2001, No. 14, 2095–2104 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Synthesis of Chiral Phosphetanes
2103
13C NMR (CDCl3): d = 13.1 (d, J = 8.4 Hz, PCH2), 18.3 (CH3), 32.9
(CH2), 52.8 (NCH2), 56.5 (NCH).
References
(1) (a) Marinetti, A.; Kruger, V.; Buzin, F.-X. Tetrahedron Lett.
1997, 38, 2947. (b) Marinetti, A.; Genêt, J.-P.; Jus, S.;
Blanc, D.; Ratovelomanana-Vidal, V. Chem. Eur. J. 1999, 5,
1160. (c) Marinetti, A.; Jus, S.; Genêt, J.-P.; Ricard, L.
Tetrahedron 2000, 56, 95. (d) Marinetti, A.; Labrue, F.;
Genêt, J.-P. Synlett 1999, 1975. (e) Berens, U.; Burk, M. J.;
Gerlach, A.; Hems, W. Angew. Chem., Int. Ed. 2000, 39,
1981. (f) Marinetti, A.; Jus, S.; Genêt, J.-P.; Ricard, L. J.
Organomet. Chem. 2001, 624, 162.
(2) (a) Kitamura, M.; Ohkuma, T.; Inoue, S.; Sayo, N.;
Kumobayashi, H.; Akutagawa, S.; Ohta, T.; Takaya, H.;
Noyori, R. J. Am. Chem. Soc. 1988, 110, 629. (b) Kawano,
H.; Ishii, Y.; Saburi, M.; Uchida, Y. J. Chem. Soc., Chem.
Commun. 1988, 87. (c) Blanc, D.; Ratovelomanana-Vidal,
V.; Marinetti, A.; Genêt, J.-P. Synlett 1999, 480.
(3) For a recent review on chiral monophosphines, see: Lagasse,
F.; Kagan, H. B. Chem. Pharm. Bull. 2000, 48, 315.
(4) Concurrently with this work, the synthesis and catalytic
applications of some monodentate phosphetanes have been
described: (a) Berens, U. WO Patent 9802445 A1 , 1998
(Chiroscience Limited). (b) Chem. Abstr. 1998, 128,
154219. (c) The synthetic approach of Scheme 1 has been
applied also to the preparation of 1-adamantyl-2,4-
dimethylphosphetane: Ohashi, A.; Matsukawa, S.; Imamoto,
T. Heterocycles 2000, 52, 905.
MS: m/z (%) = 145 (M, 19), 98 (100).
(R,R)-1-{2-[(R,R)-2,4-Dimethylazetidino]ethyl}-2,4-
dimethylphosphetane Bis-borane Complex 22
The cyclisation reaction between 20 (2.8 mmol) and (S,S)-pentane-
2,4-diol cyclic sulfate affording 22, was performed as described
above for the synthesis of the phosphetane borane complexes 9–14.
The final product was purified by column chromatography on alu-
mina with cyclohexane–Et2O (80:20) as eluent; Rf 0.4; yield: 0.16g
(25%); colourless solid; [a]D –38 (c = 1, CHCl3).
31P NMR (CDCl3): d = 55 (JP-B = 53 Hz).
1H NMR (C6D6): d = 1.25 (dd, JH-P = 7.5 Hz, J = 5.1 Hz, 3 H, CH3),
1.29 (t, JH-P = J = 7.5 Hz, 3 H, CH3), 1.40 (d, J = 7.2 Hz, 3 H, CH3),
1.41 (d, J = 6.5 Hz, 3 H, CH3), 1.80 (m, 1 H, CH2-azet), 2.13 (qd,
J = 7.0, 4.7 Hz, 1 H, CH2P), 2.3–2.5 (m, 5 H), 2.6 (m, 1 H, PCH),
2.8–3.0 (m, 2 H, NCH2), 3.8 (m, 1 H, NCH), 3.9 (m, 1 H, NCH).
13C NMR (CDCl3): d = 15.0 (d, J = 6.5 Hz, CH3), 15.4 (CH3), 16.0
(CH3), 17.1 (CH3), 18.3 (d, J = 17.7 Hz, PCH2), 26.5 (d, J = 40.1
Hz, PCH), 27.1 (d, J = 39.3 Hz, PCH), 30.9 (CH2), 36.3 (d, J = 16.9
Hz, CH2), 51.3 (d, J = 5.5 Hz, NCH2), 63.7 (NCH), 66.1 (NCH).
MS (CI): m/z = 259 (M + NH4, 100%).
Anal. Calcd for C12H30B2NP: C, 59.81; H, 12.55; N, 5.81. Found: C,
59.91; H, 12.69; N, 5.65;
(5) 31P NMR (CDCl3): d = 56. 1H NMR (CDCl3): d = 2.9–3.4 (m,
2 H), 4.0–4.3 (m, 2 H), 7.1–7.9 (C6H5). 13C NMR (CDCl3):
d = 31.7 (d, J = 10.6 Hz, CH2), 40.5 (d, J = 36.6 Hz, CH).
(6) This contrasts with the observed behaviour of the analogous
1,2,5-triphenylphospholane oxides which isomerise in basic
medium to the more stable syn-anti isomers: (a) Fiaud, J.-
C.; Legros, J.-Y. Tetrahedron Lett. 1991, 32, 5089.
(b) Guillen, F.; Fiaud, J.-C. Tetrahedron Lett. 1999, 40,
2939.
(7) Knowles, W. S.; Sabacky, M. J. J. Chem. Soc., Chem.
Commun. 1968, 1445.
(8) Riant, O.; Samuel, O.; Flessner, T.; Taudien, S.; Kagan, H.
B. J. Org. Chem. 1997, 62, 6733.
X-Ray Structure Determination of 22
Molecular formula: C12H30B2NP. Molecular weight 240.96. Co-
lourless cube, dimensions: 0.24 ¥ 0.24 ¥ 0.24 mm; crystal system:
monoclinic, space group: C2: a(Å) = 21.586(5) b(Å) = 6.896(5),
c(Å) = 13.923(5),
a(°) = 90.000(5),
b(°) = 129.060(5)
g(°) = 90.000(5), V(Å3) = 1609.3(14), Z = 4; d (gcm–3) = 0.995.
Diffractometer KappaCCD, X-Ray source MoKa (l = 0.71069 Å),
graphite monochromator. T(K) 150.0(1). Reflections measured:
5362. Independent reflections: 3974. Refinement type Fsqd. Hydro-
gen atoms mixed. Parameters refined 151. wR2 0.1118; R1 0.0402;
GoF 1.056. D peak/hole (e Å–3) 0.262/–0.263.
(9) Burk, M. J.; Feaster, J. E.; Harlow, R. L. Tetrahedron:
Asymmetry 1991, 2, 569.
(10) Mislow, K.; Siegel, J. J. Am. Chem. Soc. 1984, 106, 3319.
(11) (a) Hayashi, T. Acc. Chem. Res. 2000, 33, 354.
(b) Pedersen, H. L.; Johannsen, M. Chem. Commun 1999,
2517; and references cited therein.
(12) (a) Oshima, M.; Shimizu, I.; Yamamoto, A.; Ozawa, F.
Organometallics 1991, 10, 1221. (b) Hayashi, T.; Iwamura,
H.; Naito, M.; Matsumoto, Y.; Uozumi, Y.; Miki, M.;
Yanagi, K. J. Am. Chem. Soc. 1994, 116, 775. (c) Fuji, K.;
Sakurai, M.; Kinoshita, T.; Kawabata, T. Tetrahedron Lett.
1998, 39, 6323.
(13) Gomez-Bengoa, E.; Cuerva, J. M.; Echavarren, A. M.;
Martorell, G. Angew. Chem., Int. Ed. Engl. 1997, 36, 767.
(14) (a) Nandi, M.; Jin, J.; Rajanbabu, T. V. J. Am. Chem. Soc.
1999, 121, 9899. (b) Rajanbabu, T. V.; Nomura, N.; Jin, J.;
Radetich, B.; Park, H.; Nandi, M. Chem. Eur. J. 1999, 5,
1963.
(15) For a few selected examples, see: (a) Herrmann, W. A.;
Brossmer, C.; Ofele, K.; Reisinger, C.-P.; Riermeier, T. H.;
Beller, M.; Fischer, H. Angew. Chem. Int., Ed. Engl. 1995,
34, 1844. (b) van Strijdonck, G. P. F.; Boele, M. D. K.;
Kamer, P. C. J.; de Vries, J. G.; van Leeuwen, P. W. N. M.
Eur. J. Inorg. Chem. 1999, 1073. (c) Wolfe, J. P.;
Buchwald, S. L. Angew. Chem, Int. Ed. 1999, 38, 2413.
(d) Shaughnessy, K. H.; Kim, P.; Hartwig, J. F. J. Am. Chem.
Soc. 1999, 121, 2123. (e) Mann, G.; Incarvito, C.;
Rheingold, A. L.; Hartwig, J. F. J. Am. Chem. Soc. 1999,
(R,R)-1-{2-[(R,R)-2,4-Dimethylazetidino]ethyl}-2,4-
dimethylphosphetane (21)
The azetidine-phosphetane 21 was released from its bis-borane
complex by heating with an excess DABCO in C6D6 at 65 °C for 6
h. The trivalent phosphetane is an extremely air sensitive com-
pound, consequently the decomplexation reaction was performed in
a sealed NMR tube and the final product was characterised by NMR
of the crude reaction mixture.
31P NMR (C6D6): d = 21.1.
1H NMR (C6D6): d (selected data) = 1.11 (t, JH-P = J = 7.3 Hz, 3 H,
CH3), 1.17 (d, J = 6.3 Hz, 6 H, CH3), 1.39 (dd, JH-P = 16.8 Hz,
J = 7.3 Hz, 3 H, CH3), 1.73 (t, J = 6.3 Hz, 2 H, CH2-azet), 3.50 (m,
J = 6.3 Hz, 1 H, NCH).
13C NMR (C6D6): d = 16.2 (d, J = 3.8 Hz, CH3), 18.3 (CH3), 20.5 (d,
J = 22.0 Hz, CH3), 21.1 (d, J = 6.4 Hz, CH), 24.3 (d, J = 27.6 Hz,
PCH2), 26.2 (d, J = 9.1 Hz, CH), 33.4 (CH2), 39.5 (CH2), 46.9 (d,
J = 20.5 Hz, NCH2), 56.3 (NCH).
Synthesis 2001, No. 14, 2095–2104 ISSN 0039-7881 © Thieme Stuttgart · New York

2104
A. Marinetti et al.
PAPER
Stranne, R.; Vasse, J.-L..; Moberg, C. Org. Lett. 2001, 3,
121, 3224. (f) Aranyos, A.; Old, D. W.; Kiyomori, A.;
Wolfe, J. P.; Sadighi, J. P.; Buchwald, S. L. J. Am. Chem.
Soc. 1999, 121, 4369. (g) Wolfe, J. P.; Singer, R. A.; Yang,
B. H.; Buchwald, S. L. J. Am. Chem. Soc. 1999, 121, 9550.
(h) Littke, A. F.; Fu, G. C. Angew. Chem, Int. Ed. 1998, 37,
3387. (i) Littke, A. F.; Fu, G. C. Angew. Chem, Int. Ed. 1999,
38, 2411. (j) Littke, A. F.; Dai, C.; Fu, G. C. J. Am. Chem.
Soc. 2000, 122, 4020. (k) Fox, J. M.; Huang, X.; Chieffi, A.;
Buchwald, S. L. J. Am. Chem. Soc. 2000, 122, 1360.
(l) Quan, L. G.; Lamrani, M.; Yamamoto, Y. J. Am. Chem.
Soc. 2000, 122, 4827. (m) Ueda, M.; Miyaura, N. J. Org.
Chem. 2000, 65, 4450; and references cited therein.
2525.
(18) (a) Cadogan, J. I. G.; Sears, D. J.; Smith, D. M. J. Chem. Soc.
1969, 1314. (b) Issleib, K.; Brünner, H.-U.; Oehme, H.
Organometal. Chem. Synth. I 1970/1971, 161.
(19) Marinetti, A.; Hubert, P.; Genêt, J.-P. Eur. J. Org.Chem.
2000, 1815.
(20) (a) Kosolapoff, G. M. J. Am. Chem. Soc. 1944, 66, 109.
(b) Kosolapoff, G. M. J. Am. Chem. Soc. 1948, 70, 1971.
(21) Maier, L.; Daly, J. J. Helv. Chim. Acta 1967, 50, 1747.
(22) Budzelaar, P. H. M.; van Doorn, J. A.; Meijboom, N. Recl.
Trav. Chim. Pays-Bas 1991, 110, 420.
(16) (a) Hayashi, T.; Konishi, M.; Fukushima, M.; Mise, T.;
Kagotani, M.; Tajika, M.; Kumada, M. J. Am. Chem. Soc.
1982, 104, 180. (b) Pfaltz, A. Acc. Chem. Res. 1993, 26,
339. (c) Sprinz, J.; Helmchen, G. Tetrahedron Lett. 1993,
34, 1769. (d) Dawson, G. J.; Frost, C. G.; Williams, J. M. J.;
Coote, S. J. Tetrahedron Lett. 1993, 34, 3149.
(23) Kyba, E. P.; Liu, S. T.; Harris, R. L. Organometallics 1983,
2, 1877.
(24) Tavs, P. Chem. Ber. 1970, 103, 2428.
(25) Grabiak, R. C.; Miles, J. A.; Schwenzer, G. M. Phosphorus
Sulfur 1980, 9, 197.
(26) Sanders, R.; Mueller-Westerhoff, U. T. J. Organomet.
Chem. 1996, 512, 219.
(e) Kamikawa, T.; Hayashi, T. Tetrahedron 1999, 55, 3455.
(f) Cammidge, A. N.; Crépy, K. V. L. Chem. Commun. 2000,
1723.
(27) Ferrocenylphosphine: 31P NMR (C6D6): d = –145. 1H NMR
(C6D6): d = 3.80 (d, JH-P = 199 Hz, PH), 3.96 (s, 5 H, Cp),
4.01 (m, 2 H, CH), 4.10 (m, 2 H, CH).
(17) (a) As far as we know the only example of “symmetrical” P–
N bidentate ligand is a recently reported analogue of Diop:
Robert, F.; Delbecq, F.; Nguefack, C.; Sinou, D. Eur. J.
Inorg. Chem. 2000, 351. (b) After submission of this work,
the synthesis of “pseudo-C2-symmetric” bidentate P–N
ligands based on phosphepino moieties has been reported:
(28) (a) Goodwin, N. J.; Henderson, W.; Nicholson, B. K. Chem.
Commun. 1997, 31. (b) Goodwin, N. J.; Henderson, W.;
Nicholson, B. K.; Sarfo, J. K.; Fawcett, J.; Russel, D. R. J.
Chem. Soc., Dalton Trans. 1997, 4377.
Synthesis 2001, No. 14, 2095–2104 ISSN 0039-7881 © Thieme Stuttgart · New York