Enantioselective catalysis 113: New menthylphosphane ligands differing in steric and electronic properties

Article abstract of DOI:10.1055/s-1998-1996

A concept for bisphosphane ligands was developed, in which chirality is derived from the optically active (1R,3R,4S)-menthyl substituents in PMen₂ groups and the backbone between the phosphorus units is varied (o-phenylene, 2,2'-biphenylene, 1,1'-ferrocenediyl); one of the two PMen₂ groups was also replaced by a PPh₂ unit. The synthesis and characterisation of seven new menthylphosphanes is described. Emphasis is put on the NMR assignment of the menthyl protons by two-dimensional methods and ¹³C-¹H shift correlation. The ligands have been used in Rh and Ni complexes in several model reactions of enantiosclective catalysis giving optical inductions in the low to middle range.

Full text of DOI:10.1055/s-1998-1996

4
5
PAPERS
1
Enantioselective Catalysis 113: New Menthylphosphane Ligands Differing
in Steric and Electronic Properties
*
H. Brunner, M. Janura
Institut für Anorganische Chemie, Universität Regensburg, D-93040 Regensburg, Germany
Fax +49(941)9434439; E-mail: henri.brunner@chemie.uni-regensburg
Received 16 June 1997
A concept for bisphosphane ligands was developed, in which chiral- from the ligand to the catalytically active metal center via
ity is derived from the optically active (1R,3R,4S)-menthyl substitu-
the arrangement of the phenyl rings of the diphenylphos-
ents in PMen2 groups and the backbone between the phosphorus
phanyl groups. Our intention was to develop a series of
units is varied (o-phenylene, 2,2¢-biphenylene, 1,1¢-ferrocenediyl);
easily accessible optically active chelate phosphanes, hav-
ing the menthyl chirality next to the phosphorus atoms.
one of the two PMen groups was also replaced by a PPh unit. The
2
2
synthesis and characterisation of seven new menthylphosphanes is
described. Emphasis is put on the NMR assignment of the menthyl
protons by two-dimensional methods and 1 C– H shift correlation.
3
1
In the chelating menthylphosphanes the isopropyl group
of the menthyl unit is close to the phosphorus atom. Hence
The ligands have been used in Rh and Ni complexes in several model
reactions of enantioselective catalysis giving optical inductions in the there should be a direct interaction with the pocket of the
low to middle range.
catalyst, in which the enantioselective reaction takes
place. The backbone between the two dimenthylphospho-
rus units was varied (o-phenylene, 2,2¢-biphenylene, 1,1¢-
ferrocenediyl). One dimenthylphosphanyl group was re-
placed by a diphenylphosphanyl group to change the ste-
ric and electronic properties of the ligands. A correlation
between the structure of the ligands and their reactivity
and selectivity in asymmetric catalysis is expected.17
Introduction
Menthyl derivatives play a prominent role in the synthesis
of optically active compounds. In particular, in the early
days of catalytic asymmetric C–C bond formation, the
highest optical yields were obtained using phosphanes
2
with menthyl substituents. Meanwhile dozens of men-
thylphosphanes have been synthesised and used in differ-
3
Synthetic Strategy
ent transition-metal-catalysed asymmetric homogeneous,
4
5
heterogeneous and two-phase reactions. Menthyl-sub-
stituted phosphanes have been used for studying the
epimerisation and halogen exchange at the phosphorus
For the preparation of the menthylphosphanes the follow-
ing strategy was chosen. To introduce the dimenthylphos-
phanyl unit, (–)-chlorodimenthylphosphane18 was used. It
was prepared from the Grignard derivative of (–)-menthyl
6
atom and have been the object of extensive NMR inves-
7
chloride19 and PCl . Starting from dihaloarene com-
tigations. The menthyl unit is also used for stabilising
3
8
diphosphenes, for the synthesis of chiral 1,1-diphos-
pounds the tetramenthylbisphosphanes should be accessi-
ble by quenching the appropriate organometallic
derivative with two equivalents of the chlorodimen-
thylphosphane. Using this strategy, only one side product,
the corresponding monosubstituted dimenthylphosphanyl
arene, is eventually obtained. The purification of the prod-
ucts should occur by flash chromatography or recrystalli-
sation. For the preparation of the mixed dimenthyl-
phosphanyl-diphenylphosphanyl ligands a successive
substitution of the bromo substituents of a dibromoarene
compound was considered.
9
phanes, phosphiranes and phosphetanes and it is part of a
chirally modified zirconocene catalyst used successfully
in asymmetric carbomagnesiation of unactivated alk-
enes.10
Most of the optically active chelate phosphanes, such as
1
1
12
13
14
15
diop, prophos, bppfa, biphemp, binap, or nor-
phos,16 involve a chiral skeleton bearing two diphenyl-
phosphanyl groups. The chiral information is transferred
Dimenthylphosphanyl-diphenylphosphanylarenes
The precursor for the mixed bisphosphanebenzene 1a was
(2-bromophenyl)diphenylphosphane 4. It was synthesised
by Pd-catalysed coupling of diphenyl(trimethylsi-
lyl)phosphane and bromoiodobenzene according to a pro-
cedure discovered by Stille.20 Bromoiodobenzene was
prepared from 2-bromoaniline via a Sandmeyer reac-
tion.21 Compound 4 was treated with butyllithium at
–
70°C and quenched with ClPMen to give 1a in 66%
2
yield after chromatography on silica gel (Scheme 2).
For the preparation of the ferrocenyl- and biphenyl-
bridged dimenthylphosphanyl-diphenylphosphanyl lig-
ands a successive substitution of the bromo substituents of
the corresponding dibromoarene was performed. For di-
bromoferrocene the procedure developed by Lai and
Scheme 1

4
6
Papers
SYNTHESIS
Scheme 2
(
a) 1. BuLi, THF, –70°C, 2. ClPMen , Et O, –30°C ® reflux; (b) 1. BuLi, THF, –50°C, 2. 5a: ClPPh , THF, –40°C ® r.t.; 2d: ClPMen , THF,
2 2 2 2
40°C ® reflux; (c) 1. BuLi, hexane, TMEDA, r.t., 85%. 2. PhPCl , hexane, –70°C ® r.t., 41%; (d) 1. PhLi, Et O, r.t., 2. ClPMen , THF,
–
–
–
2
2
2
50°C ® reflux; (e) 1. t-BuLi, Et O, –78°C, 2. ClPMen , THF, –70°C ® reflux; (f) 1. PPh Br , MeCN, 60°C, 2. 280°C; (g) 1. BuLi, THF,
2
2
3
2
75°C, 2. ClPPh , Et O, –70°C ® r.t.; (h) 1. BuLi, THF, –75°C, 2. ClPMen , THF, –75°C ® r.t.
2
2
2
Dong was chosen22 which could be extended to the biphe- phanylferrocene, which was reacted with chlorodi-
nyl system. Up to now, the required 2,2¢-dibromo-1,1¢-bi- menthylphosphane to give 1-dimenthylphosphanyl-1¢-
2
3
phenyl 7 was prepared starting from expensive materials
diphenylphosphanylferrocene 2a in 48% yield after chro-
or in multistep reactions,2
4, 25
e.g. from 1-iodo-2-nitroben- matography on silica gel. Alternatively, 2a could be syn-
zene, by an Ullmann coupling followed by a catalytic re- thesised by using a ring-opening reaction of (1,1¢-
duction of the nitro to the amino groups and a Sandmeyer ferrocenediyl)phenylphosphane 628 with phenyllithium
reaction to transform the amino to the bromo functions.24 performed by Seyferth and Withers. The intermediate 1-
Here a new one-pot synthesis starting from inexpensive lithio-1¢-diphenylphosphanylferrocene was treated as de-
29
2
,2¢-dihydroxy-1,1¢-biphenyl is presented. It is a modified scribed above to give 2a. In addition, the iodo analogue of
procedure used by Takaya et al. to prepare the binap pre- 5a was synthesised by Pd-catalysed coupling of one
26
cursor 2,2¢-dibromo-1,1¢-binaphthyl. On a 0.2 mol scale equivalent of diphenyl(trimethylsilyl)phosphane and 1,1¢-
colourless crystals of 7 were obtained in 48% yield after diiodoferrocene (see also preparation of 1a). As expected,
chromatography and recrystallisation from methanol.
the two iodo-substituted cyclopentadienyl rings reacted
independently in the coupling reaction. Hence the product
distribution is close to the ideal case of 1:2:1 for recovered
starting material, the desired 1-iodo-1¢-diphenylphospha-
nylferrocene (5b) and the bissubstituted bis(diphe-
nylphosphanyl)ferrocene. The synthetically useful
ferrocenyl derivative 5b has been isolated so far only as a
The monolithiation of 1,1¢-dibromoferrocene and 2,2¢-di-
bromo-1,1¢-biphenyl 7 proceeded smoothly at low tem-
perature (–70 to –40°C) in THF to give 1-bromo-1¢-
lithioferrocene and 2-bromo-2¢-lithio-1,1¢-biphenyl, re-
spectively, which were quenched with ClPPh2 and
ClPMen to give the bromo-phosphanyl derivatives 2d
2
29b
27
byproduct.
(67%), 5a (83%) and 8 (49%), respectively, after purifi-
cation by chromatography on silica gel or alumina As biphenyl-based bisphosphanes are an important class
Scheme 2). The subsequent lithiation of compound 5a re- of chiral ligands, the systematic synthesis of menthyl-
quired tert-butyllithium to give 1-lithio-1¢-diphenylphos- phosphanes was extended to the 1,1¢-biphenyl backbone.
(

January 1998
SYNTHESIS
47
In particular, the atropisomeric bisphosphanes of the modeling program sybil2 (Figure 1 left).34 In the calculat-
14
30
biphemp /bichep ligand family served as model com- ed structure one phenyl ring of the diphenylphosphanyl
pounds. Though much effort has been made on the prepa- unit is adjusted parallel to the bromo-substitutued bi-
ration and variation of these axially dissymmetric phenyl moiety. This geometry should also be favourable
ligands,31 the synthesis still requires many steps and a res-
for the above discussed reaction mode. Thus, it is not pos-
sible to prepare 2-dimenthylphosphanyl-2¢-diphenylphos-
olution procedure. With the chirality in the menthyl sub-
stituents, a resolution step is not necessary.
phanyl-1,1-biphenyl (3a) by reaction of
8 with
butyllithium and ClPMen2.
Compound 8 was treated with one equivalent of butyllith-
ium in THF at –75 °C to perform a halogen–metal ex-
change. After stirring at this temperature for 30 minutes,
the 2-lithio-2¢-diphenylphosphanyl-1,1¢-biphenyl was
Bis(dimenthylphosphanyl)arenes
Only very few general and efficient homogeneous catalyt-
ic methods are known for the reduction of aldehydes and
quenched with ClPMen . Surprisingly, not the expected
2
bisphosphane 3a, but the P-phenyl-dibenzophosphole 9 ketones.35 One example is the achiral cationic rhodium(I)
was isolated after chromatography on silica gel using a catalyst with 1,1¢-bis(diisopropylphosphanyl)ferrocene,
petroleum ether/Et O gradient (Scheme 2). Also 9 was which hydrogenates a broad range of aldehydes and ke-
2
isolated, when other electrophiles such as DMF or CO2 tones under mild conditions,36 the important factors for
were added to 2-lithio-2¢-diphenylphosphanyl-1,1¢-biphe- catalytic efficiency being backbone flexibility and elec-
nyl or when the Grignard compound was used instead of tron-rich (di- or trialkyl-substituted) phosphorus atoms.
the lithio species. Recently Schlosser et al. published their To combine these requirements with chirality, the isopro-
results and mechanistic studies concerning the unsuccess-
ful attempts to prepare Uehara’s bpbp.32 They showed,
that the product of quenching 2,2¢-dilithiobiphenyl with
chlorodiphenylphosphane is not bpbp, but a 1:1 mixture
of 5-phenyl-5H-dibenzophosphole (9) and triphenylphos-
phane. Obviously, the monolithio-monophosphane
formed in the first step of the reaction of 2,2¢-dilithiobi-
phenyl with ClPPh or by halogen–metal exchange of 8
2
with one equivalent of butyllithium underwent an in-
tramolecular ring closure, affording the cyclic phosphane
9
and phenyllithium which eventually reacted with
ClPPh or ClPMen , respectively. However, the reaction
2
2
of ClPPh2 with 2,2¢-dilithio-6,6¢-dimethylbiphenyl or
,2¢-dilithio-1,1¢-binaphthyl smoothly proceeded to form
2
14
33
the bisphosphanes biphemp or binap, respectively.
Hence, special steric and electronic requirements seem to
be necessary for the observed ring closure. Schlosser et al.
tentatively postulated a concertedness for the substitution
at the phosphorus atom (Figure 1 right).32
Figure 1
A skew geometry showing an antiparallel orientation of
the organometallic bond with respect to the phosphorus
lone pair explains the observed reaction mode. The col-
linear attack which is characteristic for nucleophilic sub-
stitution at carbon centers is replaced by a winding-in
motion that couples the shortening of the distance be-
tween phosphorus and the metal-bearing ortho-carbon
atom to a rotation around the central biphenyl axis. A sim-
ilar geometry which is consistent with Schlosser’s results
(
®
®
a) 1. BuLi, hexane, TMEDA, r.t., 85%, 2. ClPMen , THF, –78°C
2
reflux, 62%; (b) 1. BuLi, THF, –78°C, 2. ClPMen , THF, –70°C
2
reflux; (c) Na/Hg, Et O, r.t.; (d) Li, Et O, r.t.; (e) ClPMen , Et O,
2
2
2
2
was calculated for the precursor 8 with the molecular –60°C ® r.t.; (f) BuLi, Et O, 0°C; (g) ClPMen , THF, –l5 °C ® r.t.
2
2

4
8
Papers
SYNTHESIS
pyl units in 1,1¢-bis(diisopropylphosphanyl)ferrocene were guide to the ligand basicity and the s-donor property of
exchanged by the optically active menthyl units (Scheme 3). the phosphane ligand.2
7, 41
The o-phenylene- and 2,2¢-bi-
phenylene-substituted phosphorus nuclei resonate at low-
er field than the 1,1¢-ferrocenediyl-substituted nuclei. The
same trend is evident for mono- and bisphosphanes, re-
spectively, although the difference for the ferrocenyl
phosphanes 2c and 2b is 0.8 ppm, whereas it is 10.0 ppm
between 1c and 1b. The dimenthyl-substituted phosphane
units in turn are observed at higher field than their phenyl
analogues which indicates their higher basicity.
1
1
,1¢-Bis(dimenthylphosphanyl)ferrocene 2b was thought
to be accessible from the known 1,1¢-dilithioferroce-
ne–TMEDA adduct37 and chlorodimenthylphosphane. In
the first attempts a 1:1 mixture of the mono- and disubsti-
tuted ferrocenes resulted (determined by 31P NMR inte-
gration) not separable by chromatography or re-
crystallisation. The two singlets in the 31P NMR at d–23.3
and –24.1 could not be assigned. After prolonged reflux-
ing of dilithioferrocene–TMEDA adduct with 2.2 equ- Emphasis was put on the complete assignment of the H
ivalents of ClPMen in a THF/petroleum ether 80:110 and 13C resonances of the menthyl fragments by means of
2
solvent mixture, pure 2b (d–24.1) was obtained.
two-dimensional NMR techniques and reference to the
3a,3g,7,31
literature,
e.g. with (–)-dimenthylmethylphos-
For the synthesis of the monosubstituted dimenthylphos-
phanylferrocene 2c the procedure published by Kagan
7a
phane. The menthyl groups in dimenthylphosphanyl-
substituted compounds are diastereotopic. Consequently,
all menthylphosphanes (except 3c, the only monomenth-
ylmonophosphane) have 20 non-equivalent carbon atoms
was applied. Tributylstannylferrocene 10 was treated with
butyllithium to generate the pure monolithiumferrocene,38
which was quenched with ClPMen to give 2c in reason-
2
(
which all are separated, see experimental part) and 26
able yields after chromatography on alumina and recrys-
tallisation from pentane.
1
non-equivalent hydrogen atoms. At a glance, all the H
NMR spectra of the ligands 3c, 1a and 2a shown in Figure
For preparing the 1,2-bis(dimenthylphosphanyl)benzene 2 seem to be similar. However, only H-8 resonates always
1b), the starting material 1,2-dilithiobenzene (12) was ob- at lowest field. The sequence of the other protons depends
(
tained through transmetallation from o-phenylenemercu- on the substitution pattern. Especially the signal for the
ry (11).39 After quenching with ClPMen and workup the equatorial H-2 shows large chemical shift differences: in
2
side-product tetramenthylbisphosphane could be isolated 3c it appears at d 0.76, in 2a at d 2.02 and ca. 1.2. The fer-
and characterised by spectroscopic means. The second rocenyl-substituted menthylphosphanes 2a–d exhibit typ-
1
side-product, the monosubstituted dimenthylphosphanyl- ical patterns in their H NMR spectra. Therefore, starting
1
benzene 1c could not be separated from 1b by chromatog- from 2a it was possible to assign the H NMR spectra of
31
raphy or recrystallisation. Thus, a 1:1 mixture ( P NMR the ligands 2b–d completely.
integration) of 1b and 1c was obtained and used as such.
The reason for the formation of 1c may be partial hydrol-
ysis during the preparation of 12.
Catalytic Results
Rhodium complexes, generated in situ from [Rh(cod)Cl]2
The synthesis of the biphenyl-bridged tetramenthylbis-
phosphane 3b was thought to be analogous to the prepara-
tion of one of the first axial chiral bisphosphanes,
and the ligands 1a, 1b, 2a, 2b, 3c, were used as catalysts
in the asymmetric homogeneous hydrogenation of (Z)-a-
42
acetamidocinnamic acid, methyl pyruvate, and keto-
Uehara’s
2,2¢-bis(diphenylphosphanyl)-1,1¢-biphenyl
43
bpbp.24 Starting from a solution of 2,2¢-dibromo-1,1¢-bi-
pantolactone and in the hydrosilylation of acetophenone
44
with diphenylsilane. The Grignard cross-coupling of 1-
phenyl 7 in anhydrous diethyl ether, 2.2 equivalents of but-
yllithium were added to form the corresponding 2,2¢-di-
lithio-1,1¢-biphenyl, which precipitated. When a solution
45
phenylethylmagnesium chloride with vinyl bromide
was catalysed with nickel complexes generated in situ.
of chlorodimenthylphosphane in THF was added, after The results of the asymmetric hydrogenations are sum-
workup not the expected 2,2¢-bis(dimenthylphosphanyl)- merised in the Table. Methanol is the most favourable sol-
1
,1-biphenyl 3b but the 5-menthyl-5H-dibenzophosphole vent in these hydrogenations, though toluene is necessary
(
3c) was isolated in 26% yield. The same product was ob- to increase the solubility of the ligands and to prepare the
tained, when ClPMen was added at –78 °C and the solu- catalysts. In the hydrogenation of ketopantolactone tolu-
2
tion was refluxed for 15 hours. This result is consistent ene was used as the standard solvent.43
with our observations described above and those made by
The in situ catalysts exhibited good to high hydrogenation
Schleyer, who also obtained a dibenzophosphole deriva-
activity, when (Z)-a-acetamidocinnamic acid was used as
tive after quenching the 2,2¢-dilithiobiphenyl with chlo-
rotrimethylstannane.40 Following this sequence, it was not
a substrate. Ligand 1a needed about 20 h to hydrogenate
the dehydroamino acid with 23% optical yield. Higher
possible to prepare 2,2¢-bis(dimenthylphosphanyl)-1,1-
pressure enhanced the hydrogenation rate, the enantio-
biphenyl (3b).
meric excess remaining unchanged (runs 1 and 2). The
most active ligand was 2a, which completed the reaction
under smooth conditions (r.t., 1 bar) within a few hours
NMR Spectra
(run 4). When the molar ratio substrate/Rh was lowered
All the new compounds were characterised by NMR and from 50:1 to 100:1 and 200:1 the catalyst activity de-
mass spectroscopy and elemental analysis. In general, the creased while the selectivity increased from 12 to 24% ee
relative position of the 31P resonances may be taken as a (S) (runs 4–6). With higher pressures the reaction was

January 1998
SYNTHESIS
49
Figure 2
Table. Enantioselective Hydrogenation of Substrate (4 mmol) in Solvent (11 mL) at 25°C
Entry Substratea Ligand
Ratio/Rh /Ligand
Substrate
b
Solventc
Pressure
(bar)
Time
(h)
Yieldd
(%)
e.e. (%) e
(Config. )
1
2
3
4
5
6
7
8
9
0
A
A
A
A
A
A
A
A
A
B
B
C
C
C
1a
1a
1b
2a
2a
2a
2a
2a
3c
2a
3c
1a
2a
2b
100:l:l.1
100:l:l.1
100:1:1.1
50:1:1.1
100:1:1.1
200:1:1.1
100:1:1.1
50:1:1.1
100:1:2.2
200:1:l.1
200:1:1.1
100:1:1.1
100:1:1.1
100:l:l.1
MeOH/toluene
MeOH/toluene
MeOH/toluene
MeOH/toluene
MeOH/toluene
MeOH/toluene
MeOH/toluene
MeOH/toluene
MeOH/toluene
MeOH/toluene
MeOH/toluene
toluene
1
20
3
20
3
12
17
1
> 95
> 95
50
23 (S)
24 (S)
9 (R)
10
10
1
f,g
> 95
> 95
> 95
> 95
> 95
> 95
> 99
70
12 (R)
22 (R)
24 (R)
25 (R)
18 (R)
22 (S)
11 (S)
20 (S)
9 (R)
1
10
30
10
30
30
30
50
50
50
1
3
h
1
19
20
40
65
40
h
i
1
1
1
1
1
2
3
4
10
> 99
95
i
i
toluene
toluene
20 (S)
12 (S)
a
A = (Z)-a-acetamidocinnamic acid; B = methyl pyruvate, C = ketopantolactone.
Prepared in situ with [Rh(cod)Cl]2.
b
MeOH/toluene 10:1 mL or toluene 11 mL.
c
d
1
The yield was checked by H NMR (80 MHz), see also footnotes h and i.
e
f
The enantiomeric excess of N-acetylphenylalanine was determined by polarimetry, [a]D + 46.8 (c = 1.95, EtOH).50
The 1:1 mixture of 1b and 1c was used as the ligand.
g
h
Deposition of a small amount of rhodium was observed.
Substrate (8 mmol) was hydrogenated; the chemical yield was determined by H NMR spectroscopy (80 MHz), the opticalyieldby GC (Chirasil-
1
L-Val, 25 m).
i
Substrate (4 mmol) was hydrogenated at 50°C; the chemical and optical yields were determined by GC.43

5
0
Papers
SYNTHESIS
complete in less than 1 h, but the selectivity diminished used. The intensities are relative to the basic peak (I = 100%), pos-
sible interpretations are given within brackets. Optical rotations were
(
runs 6–8). About 5–10 min after dissolving 2b and
measured with a Perkin–Elmer model 241 polarimeter on the speci-
fied solutions in 1 dm cells at r.t. Elemental analyses were performed
by the Mikroanalytisches Labor of the Universität Regensburg.
[
Rh(cod)Cl] in 1 mL of toluene a pink solid precipitated
2
which was catalytically inactive. The in situ catalyst ob-
1
tained with the 1:1 mixture of 1b and 1c exhibited a low
H NMR spectra were recorded using the following spectrometers:
hydrogenation activity (run 3). In all hydrogenation reac- FT 80 A (80 MHz, Varian), AC 250 (250 MHz, Bruker), ARX 400
tions using this mixture a deposition of small amounts of (400 MHz, Bruker) and AMX 500 (500 MHz, Bruker). The chemical
shifts are given in units of the d scale relative to internal TMS. The
rhodium was observed. This is consistent with observa-
same standard was used for the 13C NMR spectra (including DEPT
tions made in other groups, working with this class of
sequences), performed on AC 250 (63 MHz), ARX 400 (101 MHz),
and AMX 500 (125 MHz). Data are reported as follows: chemical
shift, multiplicity (s = singlet, d = doublet etc, dd = doublet from dou-
ligands.3
g, 31
In general, the observed enantiomeric excess-
es were lower than the values obtained with the similar
ligand 2,3-bis(dimenthylphosphanyl)maleic anhydride, blet. ddd = doublet from doublet from doublet etc., m = multiplet, cm
which produced up to 70% ee with (Z)-a-acetamidocin- = centered multiplet, b = broad, p = pseudo). coupling constant in Hz,
namic acid.3g
integration and assignment. Peak assignments were possible after
two-dimensional experiments (COSY, ECOSY, TOCSY, HMBC and
When methyl pyruvate was hydrogenated with Rh cata- HMQC experiments). For the 31P NMR spectra ( H-decoupled). the
ARX 400 (162 MHz), external standard 85% H PO , was used.
1
lysts to methyl lactate only 2a and 3c showed catalytic ac-
tivity (runs 10 and 11). Ligand 1a was completely
inactive. Similar results were obtained when ketopanto-
lactone was reduced to pantolactone (runs 12–14). With
3
4
BuLi was purchased from Aldrich and used directly. The compounds
1
8
19
(
–)-chlorodimenthylphosphane,
(–)-menthyl chloride,
diphe-
20
nyl(trimethylsilyl)phosphane, (2-bromophenyl)diphenylphosphane
20
21
(4),
1-bromo-2-iodobenzene,
(1,1¢-ferrocenediyl)phenylphos-
37
28
1
a as a ligand, only 10% conversion was achieved after 40 phane (6), 1,1-dilithioferrocene (TMEDA adduct), diiodofer-
hours (run 12), whereas 2a catalysed the reaction com- rocene,37 dibromoferrocene, tributylstannylferrocene (10), 1,2-
37 38
3
9
47
dilithiobenzene (12), o-phenylenemercury (11) and bis(acetoni-
pletely within 65 hours (run 13). Interestingly, in all cases
observed, 1a and 2a, both diphenylphosphanyl-dimenthyl-
phosphanyl ligands, differing only in the bridge between
the two phosphorus atoms, yielded the products in oppo-
site configuration (compare runs 1, 2 and 4–8, 12 and 13).
48
trile)palladium chloride (MeCN) PdCl2 were prepared according to
2
literature methods.
Preparation of 1¢-Substituted 1-Bromoferrocenes and 2¢-Substi-
tuted 2-Bromobiphenyls; General Procedure:
To a cooled (–50°C) 0.2 M solution of dibromoferrocene or 2,2¢-di-
bromo-1,1¢-biphenyl in freshly distilled THF was added dropwise 1.6
M BuLi in hexane (1.05 equiv). The resulting solution was stirred at
this temperature for about 30 min, during which time1-bromo-1¢-
lithioferrocene gradually precipitated (2-bromo-2¢-lithio-1,1¢-biphe-
In the hydrosilylation of acetophenone with diphenyl-
silane44 almost quantitative hydrosilylation and chemical
yields (97–99% and 92–97%, respectively) were obtained
with 1a, 2a, and 3c. Only 1b and 2b, both tetramenthyl-
substituted bisphosphanes, gave 33% and 38% of silyl- nyl did not precipitate). Then a 1 M solution of the chlorophosphane
enol ether, respectively, which on hydrolysis reverts to ac- ClPR
(1.1 equiv) in THF was added slowly and the reaction mixture
2
was allowed to warm up to r.t. When ClPMen was added, the solu-
etophenone. Obviously, this is a consequence of the
bulkiness of the ligands. After hydrolysis, the monophos-
phane 3c yielded 24% ee of (S)-1-phenylethanol in 97%
chemical yield. All the bisphosphanes produced racemic
2
tion was refluxed for another hour. After hydrolysis with degassed
1
1
M HCl, the mixture was directly evaporated onto silica gel (2 g per
g expected product, degassed before use). The coated silica gel was
loaded onto the top of a column and chromatography was performed
1
-phenylethanol within the limits of error (< 0.5% ee).17
with a gradient PE ® PE/Et O.
2
In the nickel-catalysed Grignard cross-coupling of 1-phe-
(
(
(
+)-1-(Dimenthylphosphanyl)-2-(diphenylphosphanyl)benzene
1a):
2-Bromophenyl)diphenylphosphane (4) was prepared by the Pd-
45
nylethylmagnesium chloride with vinyl bromide to form
-phenylbut-1-ene, the 1:1 mixture of the bisphosphane lb
3
and the monophosphane 1c gave the highest enantiomeric catalysed coupling of 1-bromo-2-iodobenzene (which can be ob-
excessofthementhylphosphanesdescribedhere[32%(S)], tained by a Sandmeyer reaction of freshly distilled 2-bromoaniline)
whereas 1a, 2a and 2b produced only low ee’s.17
with (trimethylsilyl)diphenylphosphane following the procedure de-
veloped by Stille.20 To a cooled (–70 °C) solution of 4 (2.09 g,
6
.1 mmol) in THF (100 mL) was added dropwise 1.6 M BuLi in hex-
All manipulations involving phosphanes were performed under ex-
clusion of air using standard Schlenk techniques under purified N . If
ane (3.85 mL, 6.2 mmol). The solution immediately turned purple. It
was stirred for 30 min, when a solution of chlorodimenthylphosphane
(2.29 g, 6.64 mmol) in Et O (20 mL) was added dropwise. The solu-
2
organometallic reagents were involved, H O was also excluded. Sol-
2
46
vents were dried and degassed according to standard procedures and
stored under nitrogen. THF was dried from potassium benzophenone
2
tion was allowed to warm to r.t. and was stirred under reflux for 15 h.
The mixture was then directly evaporated onto silica gel (~ 5 g, de-
gassed before use) and the coated silica gel was loaded onto the top
of a silica gel packed column (3´20 cm). The chromatography was
ketyl and freshly distilled before use. H O and solvents for chroma-
2
tography were degassed by bubbling N through the fluids for at least
2
8
h. Chromatographic materials (silica gel 60, 65–200 mm, Merck),
and alumina 90 (neutral, activity II-III, Merck) were saturated with
N . TLC was performed on Merck silica gel 60 F plates (visualisa-
performed with a gradient PE ® PE/Et O 20:1. The solvents were re-
2
2
254
moved to yield 2.3 g of the colourless product 1a (4.0 mmol, 66%);
mp 51–53 °C; R (silica gel, PE/Et O 20:1) = 0.54.
tion with UV light and KMnO solution). Three acronyms will be
4
ƒ
2
used successively: Men for the (1R,3R,4S)-menthyl fragment, Fc for
ferrocene and PE for petroleum ether (bp 40–60°C).
1
3
4
H NMR (CDCl . 400 MHz): d = 7.75 (cm, J = 7.7 Hz, J = 1.0 Hz,
3
3
1
H, H-6), 7.34–7.15 (m, 12 H, H-4, H-5 and PPh ), 7.07 (ddpt, J
2 PH
4 3 4
Melting points were determined using SMP-20 (Büchi) and were not
corrected. Vibrational spectra were recorded on a Beckman spectro-
meter IR 4240 or a Bio-Rad FT-IR FTS 155 in CH Cl solution or as
= J = 3.3 Hz. J = 7.6 Hz, J = 1.4 Hz, 1 H, H-3), 3.13 (cm, 1 H,
PH
3
3
3
HMen-8¢), 2.18–2.10 (cm, J
= J
= 12.1 Hz, J
=
3¢ax,2¢ax
3¢ax,4¢ax
3¢ax,2¢eq
2
2
2
3.5 Hz, 1 H, HMen-3¢ ), 1.84 (br d, J
ax
2¢eq,2¢ax
= 12.7 Hz, 1 H, HMen-
KBr pellets. For MS, the MAT 311 A (electron impact deionisation)
and the MAT 95 (field desorption) apparatus (both Finnigan) were
2¢ ), 1.79–1.70 (m, 3 H, H -3 , H -2 , H -6 ), 1.62–1.54 (m,
eq Men ax Men eq Men eq
3 H, H -5 , H -5¢ , H -6¢ ), 1.53–1.42 (m, 2 H, H -1 ,
Men eq
Men eq
Men eq
Men ax

January 1998
SYNTHESIS
51
HMen-8), 1.33–1.25 (m, 1 H, H -1¢ ), 1.23–1.16 (m, 1 H, H -4 ), 20 cm) yielded large orange-red crystals (7.3 g, 16.3 mmol, 82%); mp
Men ax
Men ax
3
3
1
.11–0.81 (m, J7 = J
= 6.8 Hz, 14 H, H -4¢ , 104–106°C.
,1
7¢,1¢ = 6.5 Hz, 3J9¢,8¢
Men ax
1
HMen-2¢ , H -5 , H -5¢ , H 3M en-7, H -7¢, H -9¢, HMen-6 ),
ax
Men ax
.76–0.59 (2 dpq + dd, J
Men ax
Men
Men
ax
H NMR (CDCl , 400 MHz): d = 7.39–7.31 (m, 10 H, PPh ), 4.42 (t,
3 2
3
3
3
0
5
J2¢ax,1¢ax = 12.5 Hz, J
= 6.5 Hz,
= 6.8 Hz, 3 H,
2
¢ax,3¢ax =
10¢,8¢
2 H, H-3¢, H-4¢), 4.33 (t, 2 H, H-2, H-5), 4.16 (q, J = 1.9 Hz, 2 H,
PH
3
H, HMen-2¢ , H -6¢ , H -10¢), 0.47 (d, J
ax
Men ax
Men
10,8
H-2¢, H-5¢), 3.99 (t, 2 H, H-3, H-4).
3
H
-10), 0.11 (d, J = 6.7 Hz. 3 H. HMen-9).
13
1
Men
9,8
C NMR (CDCl , 100 MHz): d = 138.7 (d, J = 9.5 Hz, 2 C, C-1² of
13
3
C NMR (CDCl , 100 MHz): d = 144.5 (dd, J = 9.3 and 34.2 Hz, 1
C, C-1 or C-2), 144.2 (dd, J = 22.7 and 34.5 Hz, 1 C, C-2 or C-1),
2
3
PPh ), 133.5 (d, J = 19.5 Hz. 4 C, C-2² of PPh ), 128.6 (s, 2 C, C-4²
2
2
3
1
of PPh ), 128.2 (d, J = 6.9 Hz, 4 C, C-3² of PPh ), 77.8 (d, J = 7.8
2
2
1
1
6
39.4 (dd, J = 8.4 and 16.7 Hz, 1 C, Cquart-1¢), 138.3 (dd, J = 3.1 and
2
Hz, 1 C, C-1¢), 77.7 (s, 1 C, C-1), 75.0 (d, J = 14.5 Hz, 2 C, C-2¢, C-
5.7 Hz, 1 C, Cquart-1²), 135.7 (dd, J = 7.1 and 2.5 Hz, 1 C, C-3 or C-
3
5
¢), 74.2 (d, J = 3.7 Hz, 2 C, C-3¢, C-4¢), 71.1 (s, 2 C, C-3, C-4), 68.5
), 135.4 (dd, J = 7.5 and 1.0 Hz, 1 C, C-6 or C-3), 133.6 and 133.3
n
(d, J = 1.2 Hz. 2 C, C-2, C-5).
2
(
2 d, J = 19.9 and 18.5 Hz, 4 C, C-2¢, C-6¢, C-2², C-6² of PPh ),
31
2
P NMR (CDCl , 162 MHz): d = –17.1 (s).
3
1
1
1
=
(
=
28.3–128.1 (m, 6 C, C-4 and C-5, C-3¢, C-5¢, C-3², C-5² of PPh ),
2
IR (KBr): n = 3050, 3017 (ar. C-H); 1775; 1641; 1585 (ar. C=C);
1
MS (FD, CH Cl ):m/z = 449.7/447.7 M .
2
27.7 and 127.2 (2 s, 2 C, C-4¢, C-4² of PPh ), 49.4 (d, J = 24.0 Hz,
–1
2
476, 1431 (P-ar.); 1407; 1345; 1155; 1024; 815; 745 cm .
2
C, C -4), 42.7 (dd, J = 11.5 and 1.5 Hz, 1 C, C -4¢), 39.4 (d, J
+
Men
Men
2
2
2
3.5 Hz, 1 C, CMen-2), 38.2 (d, J = 5.5 Hz, 1 C, C -2¢), 36.2–35.7
Men
3
C H BrFeP calcd
(449.1)
C
58.84
58.78
H
4.04 Br
4.29
17.80
17.29
22 18
m, 2 C, CMen-3, CMen-3¢), 34.9 (2 s, 2 C, CMen-6, CMen3-6¢), 34.0 (d, J
found
5.1 Hz, 1 C, CMen-1), 33.7 (s, 1 C, C -l¢), 28.2 (d, J = 13.1 Hz, 1
Men
3
C, CMen-8), 27.9 (dd, J = 18.5 and 7.5 Hz, 1 C, CMen-8¢), 25.4 (d, J =
3
1
1.0 Hz, 1 C, CMen-54), 25.2 (d, J = 8.0 Hz, 1 C, C -5¢), 23.1 (s, 1
Men
1-Diphenylphosphanyl-1¢-iodoferrocene (5b):
Into a flask were placed 1,1¢-diiodoferrocene (5.30 g, 12.1 mmol) and
MeCN) PdCl (77 mg, 0.30 mmol, 0.025 equiv). The flask was eva-
C, CMen-7), 22.7 (d, J = 11.0 Hz, 1 C, C -7¢), 21.8 and 21.5 (2 s, 2
Men
C, CMen-10, CMen-10¢), 15.4 (2 s, 2 C, CMen-9, C
9¢).
Men
(
31
3
2
2
P NMR (CDCl , 162 MHz): d = –13.7 (d, J = 156.2 Hz, PPh2);
18.5 (d, J = 156.2 Hz, PMen ).
PP 2
3
PP
cuated and filled with Ar three times. Enough benzene (20 mL) was
added to make a 0.5 M solution ofthe iodo compound and (trimethyl-
3
–
IR (KBr): n = 3075, 3057 (ar. C-H); 2923, 2868 (al. C-H); 1951; silyl)diphenylphosphane (3.33 mL, 13.0 mmol) was added via syrin-
89l; 1812; 1587; 1575; 1481; 1462, 1445, 1437 (P-ar.); 1385; 1368; ge. The deep purple solution was heated to 60°C for 5 d. After cooling
1
1
–1
180; 1087; 736; 685 cm .
to r.t., CHCl (100 mL) was added. The organic layer was washed
3
+
+
MS (EI, 70 eV): m/z (%) = 570.6 (6, M ), 431.5 (100, [M–Men] ), with sat. aq NaHCO
93.2 (92, [M–2xMen] ), 215.0 (35, [M–2xMen–Ph] ), 183.0 (74, (ca. 10 g) was added, before the solvents were removed. The coated
, H
3
O and brine and dried (MgSO ). Alumina
2 4
+
+
2
[
[
1
+
M–2xMen–PhP] ).
alumina was loaded onto the top of a column (alumina, 3 ´
0 cm) and chromatographed with PE ® PE/toluene l:0 ® 4:l to give
2
a] (c = 1, CH Cl ): 15.7 (589 nm), 17.6 (578 nm), 27.6 (546 nm),
l
2
2
successively recovered 1,1¢-diiodoferrocene (1.09 g, 21%) and the
desired product 5b, a yellow powder (1.85 g, 38% calcd rel. to con-
verted starting material), mp 82–83°C. With acetone of a third frac-
tion was isolated, identified as 1,1¢bis(diphenylphosphanyl)ferrocene
61 (436 nm).
C H P
8 52 2
calcd
found
C
79.96
79.79
H
9.18
8.96
3
(570.8)
(
1.30 g. 19%).
(
–)-1,2-Bis(dimenthylphosphanyl)benzene (1b):
1
H NMR (CDCl , 400 MHz): d = 7.39–7.31 (m 10 H. PPh ), 4.37 (t,
According to the literature, 1,2-dilithiobenzene (12) was prepared
3
2
3
47
2 H, H-3, H-4), 4.32 (t, 2 H, H-2¢, H-5¢), 4.12 (q, J = 1.8 Hz, 2 H,
from o-phenylenemercury (11) (5.2 g, 18.8 mmol) in freshly dis-
PH
39
H-2, H-5), 4.03 (t, 2 H, H-3¢, H-4¢).
tilled Et O (100 mL). The deep purple ethereal solution was shown
by the Gilman test to be 77% in organic bound lithium. It can be
stored at –30°C for about two weeks without loss of activity.
To a cooled (–60°C) solution of ClPMen (4.5 g. 13.0 mmol) in fresh-
ly distilled Et O (100 mL) was added dropwise the ethereal dil-
ithiobenzene 12 solution (40 mL, 5.7 mmol). The mixture was
allowed to warm slowly to r.t. and it was hydrolysed with degassed
H O. The remaining suspension was distributed between H O and
2
31
P NMR (CDCl , 162 MHz): d = –l7.2 (s).
3
IR (KBr): n = 3067 (ar. C-H); 1780; 1639; 1585 (ar. C=C); 1477,
1
MS (EI, 70 eV): m/z (%) = 496.0 (100, M ), 369.0 (37, [M–I] ).
C H FeIP calcd
–
1
431 (P-ar.); 1403; 1343; 1308; 1159; 1024; 861; 820; 742; 697 cm .
+ +
2
2
C
53.26
53.79
H
3.66
3.84
22 18
(496.1)
found
2
2
Et O. While evaporating the organic layer, a pale gray precipitate
2
2
,2¢-Dibromo-1,1¢-biphenyl (7):
formed. It was filtered off and characterised as the side-product tetra-
menthylbisphosphane. The remaining oily residue was dissolved in
hexane (20 mL), silica gel was added, and the hexane was removed.
The coated silica gel was loaded onto the top ofa flash column (silica
The brominating agent dibromo(triphenyl)phosphorane Ph PBr was
3
2
prepared in situ from triphenylphosphane (240 g, 0.92 mol) and bro-
mine (153 g, 49 mL, 0.96 mol) in MeCN (500 mL) according to the
26
literature. To the yellowish suspension of Ph PBr in MeCN was
3
2
gel, 4 ´ 20 cm) and eluted with PE ® PE/Et O 20:1. The solvents
2
added in several portions 2,2¢-dihydroxy-1,1¢-biphenyl (79 g, 0.42
mol). The viscous slurry was stirred at 60°C for 1 h and the solvent
was evaporated. Last traces of MeCN were removed in vacuo using a
bath temperature of 100°C. The temperature was gradually raised to
were removed and the remaining residue was treated with MeOH to
give a 1:l mixture of the product 1b and dimenthylphenylphosphane
1
c, which could not be separated. The mixture was dried in vacuo to
yield an off-white solid (1.48 g, 24% calcd rel. to 1b, 48% calcd rel.
to 1:1 mixture); mp 83–86°C.
2
1
80°C by means of a heating mantle over a period of 1 h. At about
40°C the strongly fuming MeCN · HBr adduct was formed and dis-
3
1
P NMR (CDCl , 162 MHz): d = –8.4 (s, 1c), –l8.4 (s, 1b) (l:1).
3
tilled off. At 220°C the melt became clear and evolution of HBr oc-
curred. The temperature of 280°C was kept for 30 min to complete
the reaction. After cooling, at a temperature of 100 °C Celite (ca. 200
g) and toluene (300 mL) were added. The suspension was allowed to
cool to r.t. under vigorous mechanica1 stirring. It was loaded onto the
top of a silica gel column (10 ´ 10 cm) and the product was separated
from triphenylphosphane oxide by filtration. About 2 L of a PE/
EtOAc 15:1 mixture were needed to elute the product. The solvents
were removed and the resulting viscous yellow residue was recry-
stallised from EtOH (90 mL) yielding colourless crystals of 7 (63 g,
IR (KBr): n = 3052, 3045 (ar. C-H); 2948, 2918. 2861 (al. C-H); 1452,
1
MS (FD, CH Cl ): m/z = 694.5 (1b ), 386.2 (1c ).
–1
431 (P-ar.);1382; 1367; 1172; 991; 850; 748; 738; 697 cm .
+ +
2
2
[
(
a] (c = 0.72, CH Cl ): –112 (589 nm), –116 (578 nm), –130
l
2
2
546 nm).
C H P 1b/C H P 1c (1:1) calcd
C
79.95
78.47
H
11.46
11.06
46
80
2
26 43
(695.1) + (386.6)
found
1
-Bromo-1¢-(diphenylphosphanyl)ferrocene (5a):
According to the General Procedure on a 19.8 mmol scale relative to 0.2 mol, 48%); mp 74–76°C; R (silica gel, toluene) = 0.7; R (silica
ƒ
ƒ
1
,1¢-dibromoferrocene with ClPPh . Chromatography (alumina, 3 ´ gel, PE/toluene) = 0.65.
2

5
2
Papers
SYNTHESIS
1
1
H NMR (CDCl , 400 MHz): d = 7.69–7.66 (m, 2 H, H-3,3¢), 7.40
H NMR (CDCl , 400 MHz): d = 7.43–7.29 (m, 10 H, PPh ),
3
3
2
–
7.35 (m, 2 H, H-5,5¢), 7.28–7.23 (m, 4 H, H-4,4¢, H-6,6¢).
4.42–4.41 (m, 1 H, H ), 4.38–4.37 (m, 1 H, H ), 4.24–4.22 (cm, 1
H, H ), 4.15–4.12 (m, 3 H, H ), 4.07–4.05 (cm, 1 H, H ), 3.93 (cm,
Fc Fc Fc
1 H. H ), 2.83–2.68 (cm. J = 7.0 Hz, J = J = J
Fc Fc
IR (KBr): n = 3056 (ar. C-H); 1453, 1426 (P-ar.); 1025; 1003; 758;
7
MS (EI, 70 eV): m/z (%) = 313.6/311.6/309.6 (8/17/9, M ), 232.7/
2
–1
4
3
3
3
3
24; 668 cm .
= J
=
Fc
PH
8,10
8,9
8¢,10¢
8¢,9¢
+
2
6.9 Hz, 2 H, HMen-8, H -8¢), 2.02 (br d, J
= 12.9 Hz, 1 H,
Men
2eq¢,2ax¢
+
+
3
3
30.7 (31/32, [M-Br] ), 151.9 (100, [M-2Br] ).
HMen-2¢ ), 1.85 (pt, J
= J = 11.2. Hz, 1 H, HMen-3ax),
eq
3ax,4ax
3ax,2ax
1
.79–1.76 (m, 2 H, H -6 , H -5 ), 1.68–1.60 (m, 2 H, H -6¢ ,
Men eq Men eq Men eq
3 3 3
C H Br calcd
C
46.20
46.01
H
2.58 Br
2.68
51.22
51.20
12
8
2
HMen-5¢ ), 1.38–0.88 (m J
= J
= 6.8 Hz, J = 6.5 Hz, 19
10¢,8¢ 7,1
(312.0)
found
eq
10,8
H. HMen-1 , H -3¢ , H -2 , H -1¢ , H -4¢ , H -2¢ ,
ax
Men ax
Men eq
Men ax
Men ax
Men ax
HMen-4 , H -6 , H -5 , H -5¢ , HMen-7. HMen-10, H -10¢),
ax Men ax Men ax Men ax
Men
2
-Bromo-2¢-(diphenylphosphanyl)-1,1¢-biphenyl (8):
3
3
0
6
.84 (d, J = 6.9 Hz, 3 H, HMen-9), 0.75–0.66 (dpq+dd, 7 H, J
=
PH
9
,8
9¢,8¢
According to the General Procedure on a 57 mmol scale relative to 7
3
4
.9 Hz, J7
= 6.5 Hz, H -6¢ , HMen-9¢, HMen-7¢), 0.41 (dpq, J
¢1¢ax
Men ax
with ClPPh . After chromatography (silica gel, 5 ´ 30 cm) a colour-
less, fluffy solid 8 (8.7 g, 20.8 mmol, 49%) was obtained; mp
l05–107°C; R (silica gel, PE/Et O 30:1) = 0.37.
3
3
2
2
=
3.6 Hz, J2
= J
– J
= 12.5 Hz, 1 H, H -2 ).
¢ax,3¢ax
2¢ax,1¢ax
2¢ax,2¢eq Men ax
13
1
C NMR (CDCl , 100 MHz): d = 139.3 and 139.1 (2 d, J = 9.8 Hz,
3
ƒ
2
2
2
C, C -1, C -1¢), 133.7 and 133.2 (2 d, J = 19.7 and 19.0 Hz, 4 C,
Ph
Ph
1
3
4
H NMR (CDCl , 500 MHz): d = 7.63 (dd, J = 7.8 Hz, J = 1.6
CPh-2, CPh-2¢, C -6, C -6¢), 128.5 and 128.3 (2 s, 2 C, C -4, C -4¢),
Ph Ph Ph Ph
3
3
3,4
3,5
3
3
4
Hz, 1 H, H-3), 7.42 (dpt, J
= 7.3 Hz J = 7.6 Hz, J
= 1.6
= 1.7
128.1 and 128.0 (2 d, J = 1.8 Hz, 4 C, C -3, C -3¢, CPh-5, CPh-5¢),
Ph Ph
1
5
¢,4¢
5¢,6¢
5¢,3¢
= 7.3 Hz, J
3
3
4
Hz, 1 H, H-5¢), 7.33 (dpt, J
= 6.6 Hz, J
78.5 (d, J = 20.3 Hz, 1 C, C -1 or C -1¢), 76.0 (d, J = 30.0 Hz, 1 C,
Fc Fc
1
4
¢,3¢
4¢,5¢
4¢,6¢
3
Hz, 1 H, H-4¢), 7.32–7.20 (m, 10 H, PPh ), 7.24 (dd, J
= 7.6 Hz,
C ), 75.8 (d, J = 6.4 Hz, 1 C, C -1¢ or C -1), 73.9 (d, J = 17.2 Hz,
Fc Fc Fc
2
6¢,5¢
4
4
4
3
3
J
= 1.7 Hz, 1 H, H-6¢), 7.16 (dpt, J = 7.8 Hz, J4,5 = 7.3 Hz,
1 C, C ), 73.1 (d, J = 12.3 Hz, 1 C, C ), 73.0 (t, J = 3.1 Hz, 1 C, C ),
6¢,4¢
4,3
Fc Fc Fc
3
3
J4,6 = 1.9 Hz, 1 H, H-4), 7.14 (ddd, J = 3.7 Hz, J
J3¢,5¢ = 1.6 Hz, 1 H, H-3¢), 7.12 (dpt, J = J = 7.3 Hz, J = 1.6
= 6.6 Hz,
72.6 (dd, J = 4.4 Hz, J = 1.8 Hz, 1 C, C ), 71.1 (d, J = 7.7 Hz, 1 C,
C ), 70.8 (d, J = 1.8 Hz, 1 C, C ), 70.3 (d, J = 2.1 Hz, 1 C, C ), 46.7
and 44.7 (2 d, J = 21.9 and 14.3 Hz, 2 C, CMen-4, CMen-4¢), 40.6 and
3
PH
3¢,4¢
Fc
3
3
4
5,4
5,6
5,3
Fc
Fc
Fc
3
4
3
Hz, 1 H, H-5), 6.96 (dd, J6 = 7.3 Hz. J = 1.9 Hz, 1 H, H-6).
1
,5
6,4
3
3
2
9.2 (2 d, J = 3.3 and 2.6 Hz, 2 C, CMen-2, C -2¢), 38.0 and 34.6 (2
Men
2
C NMR (CDCl , 125.8 MHz): d = 147.0 (d, J = 31.0 Hz, 1 C, C-
3
3
1
d, J = 15.6 and 23.9 Hz, 2 C, CMen-3, C -3¢), 35.1 and 35.0 (2 s, 2
l¢), 142,0 (d, J = 6.6 Hz, 1 C, C-1), 137.2 (d, J = 12.0 Hz, 1 C, C-
Men
1
C, CMen-6, C -6¢), 33.8 and 33.6 (2 s, 2 C, CMen-1, C -l¢), 27.9
2
1
1
¢), 136.8 and 136.9 (2 d, J = 12.3 and 11.8 Hz, 2 C, C-1² of PPh ),
Men
Men
2
4
2
and 27.6 (2 d, J = 3.0 and 2.4 Hz, 2 C, C -8, CMen-8¢), 25.7 (s, 1 C,
33.6 and 133.9 (2 d, J = 19.6 and 20.1 Hz, 4 C, C-2², C-6² of PPh ),
33.8 (d, J = 1.2 Hz, 1 C, C-3¢), 132.3 (s, 1 C, C-3), 131.8 (d, J = 3.5
Men
2
4
2
4
CMen-5), 25.6 (d, J = 2.5 Hz, 1 C, C -5¢), 22.8 and 22.7 (2 s, 2 C,
Men
3
CMen-7, CMen-7¢), 22.1 and 21.6 (2 s, 2 C, C -10, C -10¢), 16.0
Hz, 1 C. C-6), 129.9 (d, J = 5.4 Hz, 1 C, C-6¢), 129.0 (s, 1 C, C-4),
Men
Men
3
and 15.6 (2 s, 2 C, C -9, C -9¢).
1
2
1
28.6 and 128.7 (2 s, 2 C, C-4² of PPh ), 128.3 (2 d, J = 2.6 and
Men
Men
2
4
31
.8 Hz, 4 C, C-3², C-5² of PPh ), 128.3 (d, J = 2.8 Hz, 1 C, C-5¢),
28.1 (s, 1 C, C-4¢), 126.4 (s, 1 C, C-5), 124.0 (d. J = 1.9 Hz, 1 C. C-2).
P NMR (CDCl , 162 MHz): d = –16.3 (s, PPh ), –24.2 (s, PMen ).
3 2 2
2
4
IR (KBr): n= 3103, 3076 (ar. C-H); 2961, 2919, 2863 (al. C-H); 1456,
1439 (P-ar.); 1380; 1161; 1091; 1030; 825; 741; 695 cm .
31
–1
P NMR (CDCl , 162 MHz): d = –12.5 (s).
3
+
+
IR (KBr): n = 3054. 3005 (ar. C-H); 1584; 1562 (ar. C=C); 1478;
1
MS (EI, 70 eV): m/z (%) = 678.6 (54, M ), 539.5 (33, [M–Men] ),
493.6 (25, [M–PPh ] ), 401.3 (100, [M–2xMen] ), 216.0 (24,
[M–2xMen–PPh ] ).
–1
+
+
454, 1430 (P-ar.); 1088; 1026; 1002; 765; 745; 696 cm .
2
+
+
MS (EI, 70 eV): m/z (%) = 417.1/415.1 (l/1%, [M-H] ), 337.1 (100%,
2
+
+
+
[M-Br] ), 260.1 (5%, [M-Br-Ph] ), 182.9 (16%, [M-Br-2xPh] ).
[a] (c = 0.5, CH Cl ): –99 (589 nm), –94 (578 nm), –44 (546 nm).
l
2
2
C H BrP calcd
C
69.08
68.25
H
4.35
4.42
C H FeP calcd
C
74.33
74.32
74.24
H
8.32
8.63
8.24
24
18
30 46
2
(417.3)
found
(678.7)
found
found
(Method A)
(Method B)
(
(
–)-1-Dimenthylphosphanyl-1¢-(diphenylphosphanyl)ferrocene
2a):
(–)-1,1¢-Bis(dimenthylphosphanyl)ferrocene (2b):
MethodA: Via Nucleophilic P–C bond opening of(1,1’-Ferrocenedi-
yl)phenylphosphane 6 with PhLi:
To a cooled (–78°C) suspension of 1,1¢-dilithioferrocene–TMEDA
adduct37 (2.21 g, 7.04 mmol) in petroleum ether (bp 80–110°C,
To a solution of 20% PhLi in hexane/Et O (7:3) (1.5 mL, 3 mmol) in
100 mL) was added dropwise a solution of ClPMen (6.05 g, 17.5
2
2
Et O (5 mL) was added over 45 min at r.t. a solution of 6 (0.8 g,
2
mmol) in freshly distilled THF (20 mL) over1 h. The solution was al-
2
.7 mmol) in hexane (50 mL). After stirring for 1 h, the solvent was
lowed to warm up to r.t. and refluxed for 24 h. It was hydrolysed with
2
removed. The brown orange residue was dissolved in freshly distilled
degassed 1 M HCl (5 mL) and dried (Na SO ). The solvents were re-
4
THF (20 mL) and cooled to –50°C. A solution of ClPMen (1.18 g,
moved and the residue was dissolved in CH Cl (20 mL). Silica gel
2
2
2
3
.4 mmol) in THF (30 mL) was added over 45 min and the reaction
(10 g) was added and the CH Cl was evaporated. The coated silica
2 2
mixture was allowed to warm up. It was refluxed for an additional
hour and after cooling hydrolysed with degassed 1 M HCl (0.5 mL).
Silica gel (ca. 3 g) was added and the solvents were removed. The
coated silica gel was loaded onto the top ofa column (alumina, 3 ´ 15
gel was added onto the top of a column (alumina, 3 ´ 20 cm) and elu-
ted with PE ® PE/Et O (50:1) to give an orange brown solid of 2b
2
(3.5 g, 4.3 mmol, 62%), mp 190–l93°C (dec.).
1
H NMR (CDCl , 400 MHz): d = 4.32–4.31 (cm, 2 H, H , H ¢),
3
Fc
Fc
cm) and chromatographed with hexane ® hexane/Et O (40:1) to
4.26–4.25 (cm, 2 H, H , H ¢), 4.19–4.17 (cm, 2 H, H , H ¢),
Fc Fc Fc Fc
4 3 3
2
yield the product 2a (0.55 g, 0.8 mmol, 36%).
4.12–4.11 (cm, 2 H, H , H ¢), 2.86 (cm. J = 6.2 Hz, J = J
=
Fc
Fc
PH
8,10
8,9
4
3
3
6
.8 Hz, 2 H, H -8), 2.80 (cm, J = 6.9 Hz, J
= J = 6.8 Hz,
= 12.9 Hz, 2 H, HMen-2 ), 1.94 (pt,
Men
PH
8¢,10¢ 8¢,9¢
2
Method B: Via Halogen–Metal Exchange with 1-Bromo-1¢-(diphe-
nylphosphanyl)ferrocene (5a) and t-BuLi:
2 H, H -8¢), 2.13 (br d, J
Men
=
2eq,2ax eq
3
3
= 11.4 Hz, 3J
J3ax,4ax
J
= 2.4 Hz, 2 H, HMen-3ax),
3ax,2ax
3ax,2eq
eq
5
a (3.40 g, 7.57 mmol) was dissolved in freshly distilled Et O
1.81–l.78 (m, 4 H, HMen-6eq, HMen-5 ), 1.69–1.60 (m, 4 H, H -6¢ ,
2
Men eq
(
8
100 mL) and cooled to –78°C. 1.6 M t-BuLi in pentane (5 mL,
mmol) was added dropwise over 15 min and the reaction mixture
was stirred for 30 min at –70°C. Then a solution ofClPMen (2.74 g,
HMen-5¢ ), 1.46–l.35 (m, 6 H, H -l , H -3¢ , H -2¢ ),
eq Men ax Men ax Men eq
3 3 3 3
1.25–0.84 (m, J7 = 6.5 Hz, J = J
= J = 6.8 Hz, 38 H, H
-
,1
10,8
10¢,8¢
9,8
Men
1¢ , H -4¢ , H -2 , H -4 , H -6 , H -5 , H -5¢ ,
2
ax
Men ax
Men ax
Men ax
Men ax
Men ax
Men ax
3
7
.94 mmol) in freshly distilled THF (10 mL) was added and the coo-
H
-7, HMen-10, HMen-10¢, HMen-9), 0.73–0.68 (dpq+dd, J
= 6.9
Men
Hz, J7
= 3.3 Hz. J2
9¢,8¢
3
4
ling bath was removed. The mixture was refluxed for another hour
and hydrolysed with degassed sat. brine (1 mL). Then it was directly
evaporated onto silica gel (10 g). Chromatography (alumina, 2.5 ´ 20
cm) with PE yielded the orange-red solid 2a (2.45 g, 3.6 mmol, 48%)
which was recrystallised from hexane (10 mL); mp 14l–l42°C.
= 6.5 Hz, 14 H, H -6¢ , HMen-9¢, HMen-7¢), 0.51 (dpq, J
¢ax,3¢ax
¢,1¢ax
Men ax
PH
3
3
2
= J
= J
= 12.8 Hz, 2 H, HMen-2¢ax).
2¢ax,1¢ax
2¢ax,2¢eq
P NMR (CDCl , 162 MHz): d = –24.1 (s).
3
IR (KBr):3 = 3096 (ar. C-H); 2956, 2926, 2870, 2853 (al. C-H);
–1
2662; 1457 (P-ar.); 1379; 1369; 188; 155; 1032; 820 cm .

January 1998
SYNTHESIS
53
MS (FD, toluene): m/z = 803.3 M+.
[a] (c = 0.9, CH Cl ): –71 (589 nm), –66 (578 nm), –25 (546 nm).
l
2
2
[
a] (c = 1, CH Cl ): –147 (589 nm), –139 (578 nm), –78 (546 nm)
l 2 2
C H BrFeP calcd
C
62.84
62.56
H
8.32
8.14
30 46
C H FeP calcd
C
74.79
74.63
H
10.54
10.69
(573.4)
found
50
84
2
(803.0)
found
(–)-5-P-Menthyl-5H-dibenzophosphole (3c):
(
–)-Dimenthylphosphanylferrocene (2c):
A solution of 2.2¢-dibromo-1,1¢-biphenyl (7) (1.29 g, 4.13 mmol) in
Tributylstannylferrocene (10) (1.34 g, 2.8 mmol) was dissolved in Et O (15 mL) was cooled to 0°C and treated with 1.6 M BuLi in
2
4
9
freshly distilled THF (15 mL) and cooled to –78°C. Then 1.6 M BuLi hexane (5.5 mL, 8.8 mmol) to give 2,2¢-dilithio-1,1¢-biphenyl. The
in hexane (1.9 mL, 3.0 mmol) was slowly added over 10 min, and the black solution was stirred for 5 h at r.t. and cooled to –15 °C. When a
reaction mixture was stirred for 20 min. A precipitate of lithioferro- solution of ClPMen (3.39 g, 9.8 mmol) in THF (30 mL) was added,
2
cene appeared. A solution of ClPMen (1.08 g, 3.1 mmol) in THF the colour turned purple. After stirring for 15 h, it was hydrolysed
2
(
–
10 mL) was then added and the cooling bath was removed. At ca. with degassed 1 M HCl (1 mL). The mixture was directly evaporated
50°C the colour ofthe mixture turned brown. The solution was heat- onto silica gel (ca. 5 g, degassed before use) and the coated silica gel
ed under reflux for another hour. then cooled to r.t. and hydrolysed was loaded onto the top of a silica gel column (3 ´ 20 cm). The chro-
with degassed 1 M HCl (1 mL). This mixture was then directly evap- matography was performed with PE to yield the colourless solid 3c
orated onto silica gel (~ 5 g, degassed before use) and the coated silica (0.35 g, 1.1 mmol. 26%); mp 111–113°C; R (silica gel, PE) = 0.75.
ƒ
1
4
3
gel was loaded onto the top of an alumina column (3 ´ 20 cm). First
H NMR (CDCl , 400 MHz): d = 7.95–7.92 (m, J = 0.8 Hz, J =
7.4 Hz, 2 H. H-1, H-9), 7.66 (dddd, J = 7.4 Hz, J = 7.4 Hz, J
1.3 Hz, J = 0.8 Hz, 1 H, H-4), 7.61 (dddd, J = 7.4 Hz, J
3
PH
3
3
4
with PE traces of ferrocene were eluted, then with PE/Et O (20:1) the
2
PH
4,3
4,2
=
5
3
3
product 2c. The solvents were removed and the remaining oily resi-
due was recrystallised from a minimum of pentane (4 mL) to give red
coffinlike crystals (0.60 g, 1.2 mmol, 43%); mp 119.5–121°C.
=
7
4
,1
PH
6,7
4
5
3
.4 Hz, J6 = 1.3 Hz, J = 0.8 Hz, 1 H, H-6), 7.45 (ddd, J2,3 = 3J2,1
,8 6,9
4 3 3
=
7.4 Hz, J2 = 1.3 Hz, 1 H, H-2), 7.44 (ddd, J = J = 7.4 Hz,
,4 8,7 8,9
4 3 3
1
4
H NMR (CDCl , 400 MHz): d= 4.30–4.28 (cm, 1 H, H ), 4.28–4.26
J8,6 = 1.3 Hz, 1 H, H-8), 7.35 (dddd, J = 2.8 Hz, J = J = 7.4
3
Fc
PH
3,2
3,4
3
4
4
3
(
(
cm, 1 H, H ), 4.22–4.20 (cm, 1 H, H ), 4.17 (s, 5 H, Cp), 4.15–4.14 Hz, J = 1.1 Hz, 1 H, H-3), 7.33 (dddd, J = 2.8 Hz, J = J
=
=
Fc
Fc
3,1
PH
7,8
7,6
4
3
3
4
4
3
cm, 1 H, H ), 2.85 (cm, J = 6.8 Hz, J
= J = 6.9 Hz, 1 H, 7.4 Hz, J = 1.1 Hz, 1 H, H-7), 3.05 (dddd, J = 6.9 Hz, J
8,9
7,9 PH 8,4ax
3 3 2
Fc
PH
8,10
3
3
HMen-8), 2.76 (cm, J = 6.8 Hz, J
= J
= 6.9 Hz, 1 H, HMen- 2.9 Hz, J = 6.8 Hz, J
= 6.9 Hz, 1 H, H -8), 2.04 (dddd, J
8,10 Men PH
3
PH
8¢,10¢
8¢,9¢
8,9
2
3
3
3
8
¢), 2.15 (br d, J2
= 13.1 Hz, 1 H, HMen-2 ), 1.96 (pt, J
=
= 8.8 Hz, J
= J
= 11.7 Hz, J
= 3.2 Hz, 1 H, HMen-
3ax,2eq
3
eq,2ax
eq
3ax,4ax
3ax,2ax
3ax,2ax
3
3
3
J
= 11.3 Hz, J
= 2.5 Hz, 1 H, HMen-3 ), 1.81–1.78 (m, 2 3ax), 1.77 (cm, J5eq,5ax = 12.9 Hz, J
= 3.2 Hz, J
= 3.6 Hz,
3ax,2ax
3ax,2eq
ax
5eq,4ax
5eq,6ax
2
H, HMen-6 , H -5 ), 1.69–1.60 (m, 2 H, H -6¢ , H -5¢ ), 1 H. H -5 ), 1.60 (br d. J
= 12.9 Hz, 1 H. H -6 ), 1.47
eq
Men eq
Men eq
Men eq
Men eq
6eq,6ax
Men eq
3
3
3
3
1
.47–1.37 (m, 3 H, HMen-1 , H -3¢ , H -2 ), 1.27–1.10 (m, 4 H, (ddddd, J = 3.7 Hz, J
= 11.7 Hz, J
= 3.2 Hz, J
ax
Men ax
Men eq
PH
4ax,3ax
4ax,5eq
4ax,5ax
3
3
3
H
-1¢ , H -4¢ , H -2¢ , H -4 ), 1.10–0.88 (m. 15 H, J
=
= 12.0 Hz, J
= 2.9 Hz, 1 H, HMen-4), 1.17 - 1.01 (m, J = 6.8
= J = 6.9 Hz, H -6 , H -5 , H -5¢ , HMen-7, Hz, J = 6.9 Hz, 8 H, HMen-l, HMen-5 , HMen-9, HMen-10), 0.76
Men ax
Men ax
Men ax
Men ax
7,1
4ax,8
9,8
3
3
3
3
J10.8 – J
10¢.8¢
9,8
Men ax
Men ax
Men ax
1,8
ax
3
3
2
3
3
H
Men-10, HMen-10¢, HMen-9), 0.74–0.68 (dpq+dd, 7 H, J
= 6.9 Hz, (dddd. J = 2.3 Hz, J
= 13.3 Hz, J
= 2.3 Hz, J
=
9¢,8¢
PH
2eq,2ax
2eq,1ax
= 12.9 Hz, J
= 3.6 Hz, 1 H, H -6 ), 0.48 (d, J
2eq,3ax
= 11.8
3
4
2
3
J7¢,1¢ax 3= 6.5 Hz, H -6¢ , HMen-9¢, HMen-7¢), 0.51 (dpq,
J
=
3.2 Hz, 1 H, H -2 ), 0.66 (dpq, J
Hz, J
Men ax
PH
Men eq
6ax,6eq
6ax,1ax
3
2
’
3
3
3
.4 Hz, J2
= J
= J
= 13.0 Hz, 1 H, HMen-2 ax).
= 6.5 Hz, 3 H,
7,1ax
3
¢ax,3¢ax
2¢ax,1¢ax
2¢ax.2¢eq
6ax,5eq
Men ax
31
3
2
P NMR (CDCl , 162 MHz): d = –23.3 (s).
H
-7), 0.02 (dpq, J = 3.9 Hz, J
= 13.3 Hz, J
=
2ax,3ax
3
Men
PH
J2ax,1ax = 11.7 Hz, 1 H, Hmen-2ax).
13
2ax,2eq
3
IR (KBr): n = 3099 (ar. C-H); 2956, 2925, 2864 (al. C-H); 1458 (P-
–1
2
ar.); 1413; 1384; 1367; 1191; 1155; 1108; 817 cm .
C NMR (CDCl , 100 MHz): d = 144.5 and 144.3 (2 d, J = 1.9 and
2.5 Hz, 2 C, C-1a and C-9a), 142.3 and 140.6 (2 d, J = 5.0 and 9.7
3
+
1
MS (EI, 70 eV): m/z (%) = 494.4 (100, M ).
2
[
(
a] (c = 0.45, CH Cl ): –197 (589 nm), –184 (578 nm), –139 Hz, 2 C, C-4a and C-6a), 130.5 and 129.5 (2 d, J = 20.2 and 21.5 Hz,
l
2
2
546 nm).
2 C, C-4 and C-6), 127.9 and 127.8 (2 s, 2 C, C-2 and C-8), 127.0 and
3
1
26.6 (2 d, J = 7.2 and 7.0 Hz, 2 C, C-3 and C-7), 121.3 and 121.1 (2
s, 2 C, C-1 and C-7), 45.6 (d, J = 8.0 Hz, 1 C, C -4), 41.6 (d, J =
C H FeP calcd
C
72.87
72.95
H
9.58
9.63
3
0 47
2
1
(494.5)
found
Men
2
2
0.5 Hz, 1 C, C -3), 35.3 (d, J = 5.2 Hz, 1 C, C -2), 34.9 (s, 1 C,
Men Men
3 3
CMen-6), 33.5 (d, J = 2.3 Hz, 1 C, C -1), 28.9 (d, J = 19.7 Hz, 1 C,
Men
3
CMen-8), 25.7 (d, J = 8.0 Hz, 1 C, CMen-5), 22.1 (s, 1 C, CMen-7), 21.5
(
–)-1-Bromo-1¢-(dimenthylphosphanyl)ferrocene (2d):
(
s, 1 C, CMen-l0), 15.5 (s, 1 C, CMen-9).
According to the General Procedure on a 6.0 mmol scale of 1,1¢-di-
3
1P NMR (CDCl
bromoferrocene with chlorodimenthylphosphane. Chromatography
3
, 162 MHz): d = –7.5 (s).
(
alumina, 3 ´ 15 cm) with PE yielded a viscous red oil of 2d (2.3 g, IR (KBr): n = 3070 (ar. C-H); 2954, 2931, 2867 (al. C-H); 1938;
4
.0 mmol, 67%) which crystallised over several months.
1903; 1594 (ar. C=C); 1456, 1434 (P-ar.); 1366; 1184; 1124; 1082;
1
–1
H NMR (CDCl , 400 MHz): d = 4.39–4.37 (m, 2 H, H ), 4.35–4.34 1030; 999; 973; 934; 854; 803; 743; 721 cm .
3
Fc
+
+
(
m, 1 H, H ), 4.32 - 4.31 (m, 1 H, H ), 4.24–4.22 (m, 1 H, H ), MS (EI, 70 eV): m/z (%) = 322.2 (88, M ), 307.1 (4, [M–Me] ), 279.1
Fc
Fc
Fc
4
4
i
+
+
4
.12–4.10 (m, 3 H, H ), 2.88–2.74 (cm, J = 6.5 Hz, J = 7.0 Hz, (7. [M–Me– Pr] ), 183.9 (100, [M–Men] ).
Fc P, 8 P, 8 ¢
3 3 3
3
J8 = J = J
= J = 6.9 Hz, 2 H, HMen-8, HMen-8¢), 2.14 (br [a]
l
(c = 0.88, CH
Cl ): –121 (589 nm), –127, (578 nm), –146 (546
2 2
,10
8,9
8¢,10¢
8¢,9¢
2
3
3
d, J
1
= 13.1 Hz, 1 H, HMen-2 ), 2.02 (pt, J
= J
=
nm), –268 (436 nm), –492 (365 nm).
2
eq,2ax
eq
3ax,4ax
3ax,2ax
3
1.4 Hz, J3
ax,2eq ax
= 2.7 Hz, 1 H, HMen-3 ), 1.81–1.78 (m, 2 H, HMen-
C H P
(322.4)
calcd
found
C
81.95
80.74
H
8.44
8.16
2
2 27
6eq, HMen-5 ), 1.69–1.61 (m, 2 H, H -6¢ , H -5¢ ), 1.48–1.30 (m,
eq
Men eq Men eq
3
3
3
=
H, H -1 , H -3¢ , H -2 ), 1.27–0.83 (m, 19 H, J = J
Men ax Men ax Men eq 7,1 10,8
3 3
J10¢.8¢ = J = 6.8 Hz, H -1¢ , H -4¢ , H -2¢ , H
4 ,
9,8
Men ax
Men ax
Men ax
Men- ax
HMen-6 , H -5 . H -5¢ , H -7, HMen-10, HMen-10¢, HMen-9), Side-Product (–)-Tetramenthylbisphosphane:
ax
Men ax
Men ax
Men
3
3
0
.73–0.68 (dpq+dd, J9 = 6.9 Hz. J
Men-9¢, HMen-7¢), 0.49 (dpq, J = 3.2 Hz, J
= 6.5 Hz, 7 H, H -6¢ , When trying to prepare 1a via the Grignard route, a white undissolved
7¢,1¢ax Men ax
3 3
¢,8¢
4
H
= J =
2¢ax,1¢ax
residue remained between the aqueous and ethereal layer. This resi-
due was isolated, washed several times with Et O and dried in vacuo.
PH
2¢ax,3¢ax
2
J
= 12.5 Hz, 1 H, HMen-2¢ ).
2
2
¢ax,2¢eq
ax
31
Also in the synthesis of 1b, tetramenthylbisphosphane appeared as a
side-product, which could be isolated in ca. 5% yield. The off-white
residue is insoluble in Et O, slightly soluble in less polar solvents; mp
P NMR (CDCl , 162 MHz): d = –24.4 (s).
3
IR (CH Cl ): n = 3042 (ar. C-H); 2982, 2953, 2921 (al. C-H); 1500;
2
2
–
1
1
439 (P-ar.); 1417; 1260; 1149; 886; 720 cm .
2
+
< 240°C (dec.).
1
MS (EI, 70 eV): m/z (%) = 574.3/572.3 (26/28, M ), 494.4 (22,
+
+
[
[
[
M–Br] ), 436.2/434.2 (12/11, [M–Men] ), 372.3 (54,
H NMR (CDCl , 400 MHz): d = 2.92–2.90 (m, 2 H), 2.77–2.70 (m,
3
3
+
+
M+O-Br–Men] ), 356.2 (8, [M–Br–Men] ), 296.9/294.9 (79/85, 2 H), 2.36–2.27 (m, 4 H), 1.87–1.72 (m, 8 H), 1.53–0.76 (m, J =
+
+
3
3
M–2xMen] ), 216.9 (100, [M–Br–2xMen] ).
6.5 Hz, J = 6.9 Hz, 48 H), 0.71 – 0.68 (2 d, J = 6.8 Hz, 12 H).

5
4
Papers
SYNTHESIS
3
1
P NMR (CDCl , 162 MHz): d = –42.1 (s).
b) Strukul, G.; Bonivento, M.; Graziani, M.; Cernia, E.; Palladi-
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3
IR (KBr): n = 2952, 2925, 2866 (al. C-H); 1456 (P-al.); 1369; 1082;
9
MS (EI, 70 eV): m/z (%) = 618.6 (100, M ).
–1
96; 851 cm .
+
[
(
a] (c = 0.34, CHCl ): –375 (589 nm), –394 (578 nm), –456
(6) Hägele, G.; Kückelhaus, W.; Tossing, G.; Seega, J.; Harris,
R. K.; Creswell, C. J.; Jageland, P. T. J. Chem. Soc., Dalton
Trans. 1987, 795 (and refs. cited therein).
l
3
546 nm), –865 (436 nm).
C H P
0 76 2
calcd
found
C
77.62
76.92
H
12.38
11.89
4
(
7) a) Benn, R. Org. Magn. Res. 1983, 21, 60.
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(619.0)
Catalyses
42
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The hydrogenation of (Z)-a-acetamidocinnamic acid and ketopan-
43
tolactone, the hydrosilylation of acetophenone with diphenyl-
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a) de Vaumas, R.; Marinetti, A.; Ricard, L.; Mathey, F. J. Am.
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45
chloride with vinyl bromide were carried out as described in the lit-
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phosphane ligand (0.044 mmol) (or 0.088 mmol of a monophosphane
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1
2, 1207.
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3
stainless steel autoclave. After the atmosphere was replaced with hy-
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1
997, 529, 465.
(
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1
aliquot ofthe product to the isopropylcarbamate derivative in CH Cl .
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(
1
We thank the Bayerische Forschungsverbund Katalyse (FORKAT)
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