Influence of structural changes in ferrocene phosphane aminophosphane ligands on their catalytic activity

Article abstract of DOI:10.1016/j.jorganchem.2009.01.027

New phosphane aminophosphane ligands based on [3]ferrocenophane skeleton were synthesized using a direct double lithiation followed by phosphanylation. Influence of ligand structure on catalytic performance was evaluated by performing a series of Pd-catalyzed allylic substitution on different substrates. Enantioselectivities up to 55% ee were obtained with bridged ligand compared to 33% ee with analogous non-bridged BoPhoz ligand.

Full text of DOI:10.1016/j.jorganchem.2009.01.027

Journal of Organometallic Chemistry 694 (2009) 1898–1902
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Influence of structural changes in ferrocene phosphane aminophosphane
ligands on their catalytic activity
*
Radovan Šebesta , Andrea Škvorcová
Department of Organic Chemistry, Faculty of Natural Sciences, Comenius University, Mlynská dolina CH-2, SK-84215 Bratislava, Slovakia
a r t i c l e i n f o
a b s t r a c t
Article history:
New phosphane aminophosphane ligands based on [3]ferrocenophane skeleton were synthesized using a
direct double lithiation followed by phosphanylation. Influence of ligand structure on catalytic perfor-
mance was evaluated by performing a series of Pd-catalyzed allylic substitution on different substrates.
Enantioselectivities up to 55% ee were obtained with bridged ligand compared to 33% ee with analogous
non-bridged BoPhoz ligand.
Received 23 October 2008
Received in revised form 17 December 2008
Accepted 16 January 2009
Available online 22 January 2009
Ó 2009 Elsevier B.V. All rights reserved.
Keywords:
Ferrocene
ortho-Lithiation
Asymmetric catalysis
Allylic substitution
1. Introduction
allylic substitution, Rh-catalyzed hydrogenation and Cu-catalyzed
conjugate addition of Et2Zn [17,18] (see Fig. 1).
Transition metal complexes with chiral ferrocene ligands repre-
sent an important class of enantioselective catalysts [1]. Ferrocene
scaffold is, for its interesting stereochemical properties, an attrac-
tive and often used design motive. Numerous enantioselective
transformations are successfully catalyzed by chiral ferrocene
diphosphanes [2–4], amino phosphanes [5] as well as other types
of ligands [6–10].
We hypothesized that another way to improve ligand 1 and to
gain further information on effects of structural changes on cata-
lytic performance of ligands of this type could be preparation of
phosphano aminophophane 3. Such compounds would also be
bridged analogs to well-known BoPhoz ligands [19]. In this paper,
we present synthesis of this new type of ligands along with results
of comparative study of their catalytic performance.
Ferrocenes with carbon-bridged cyclopentadienyl rings, ferroc-
enophanes, are interesting subgroup of ferrocene derivatives [11].
Although many ferrocenophane derivatives are known, only com-
pounds having three and five carbon bridge were used as ligands
for asymmetric catalysis. Weissensteiner described several [3]fer-
rocenophane phosphane ligands which were applied in Pt-cata-
lyzed carbonylation [12], and Rh-catalyzed hydrogenations of
olefins [13]. In Pd-catalyzed allylic alkylation, diphosphane ligands
were active (up to 70% ee) but aminophosphane 1 produced race-
mic allylation product [14]. This observation stimulated us to pre-
pare modified [3]ferrocenophane aminophosphane ligand 2 with
increased chelate ring size due to inserted methylene group be-
tween phosphorus and cyclopentadienyl ring. Palladium com-
plexes with ligand 2 were useful catalysts for allylic substitution
(up to 86% ee) [15]. Erker prepared [3]ferrocenophane diphos-
phanes of different type which were efficient in Rh-catalyzed
hydrogenations [16]. We have also recently showed that [5] ferro-
cenophane phosphanes are interesting ligands for Pd-catalyzed
2. Results and discussion
The ligand synthesis starts from ketone 4. The stereogenic cen-
ter was introduced by reductive amination of oxo group using (S)-
phenylethylamine and NaBH4. The resulting diastereoisomeric
amines were separated by flash chromatography and (S,S)-diaste-
reoisomer was then reductively methylated using formaldehyde
and NaBH4 to form tertiary amine 5 [20]. To remove 2-phenylethyl
group, amine 5 was subjected to hydrogenolysis with Pd/C in for-
mic acid. This reaction produced N-methylated amine 6 in 80%
yield (Scheme 1).
At the beginning we planned to use dimethylamino derivative 1
for diastereoselective ortho-lithiation and subsequently transform
it to N-monomethyl compound for introduction of second phos-
phane group. However this approach failed, the desired nucleo-
philic substitution on
a-carbon to Cp-ring could not be
performed, presumably, because of large steric hindrance. There-
fore, we looked for alternatives.
Diastereoselective ortho-metallation, particularly lithiation, is
the main method for introduction of planar chirality in ferrocene
* Corresponding author. Tel.: +421 260296376; fax: +421 260296337.
E-mail address: sebesta@fns.uniba.sk (R. Šebesta).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.01.027

R. Šebesta, A. Škvorcová / Journal of Organometallic Chemistry 694 (2009) 1898–1902
1899
as acetal [28], sulfoxide [29] and oxazaphospholidine-oxide [30]
were also described as suitable directing groups. However, exam-
ples of proton containing groups as ortho-directing substituents
are scarce. Interestingly, lithiation of Boc-protected amine led to
introduction of lithium to unfunctionalized Cp-ring [31], Recently,
direct ortho-lithiation of free ferrocenyl alcohols was also de-
scribed [32]. We envisaged that it would be of high value if amine
6 could be directly and diastreoselectively lithiated with added
benefit of one-pot introduction of desired phosphane group also
on nitrogen upon reaction with appropriate electrophile. Treating
amine 6 with 2.5 equiv. of BuLi and subsequent reaction with chlo-
rodiphenylphosphane led indeed to formation of phosphane 3 in
60% yield after a rapid flash chromatography and crystallization.
Proton and phosphorus NMR spectra of the crude reaction mixture
revealed that d.r. is 99:1. Similarly, reaction with chloro-
dicyclohexylphosphane resulted in formation of phosphane 7 in
47% yield (Scheme 1). Noteworthy is also the fact that lithiation
of analogous non-bridged derivative led to a complicated mixture
of compounds.
We were not able to produce crystals suitable for X-ray analysis
from phosphanes 3 or 7. However, NOESY NMR experiments con-
firmed that a relative configuration of planar stereogenic unit is
Sp. Fig. 2 depicts major NOE interactions and NOESY spectrum of
phosphane 3. Configuration of chiral carbon was established previ-
ously [33].
As a benchmark C–C bond forming reaction we chose Pd-cata-
lyzed allylic alkylation. Symmetrical substrates, 1,3-diphenylp-
ropenyl acetate (8) and cyclohexenyl acetate (10) were reacted
with C-anion generated from dimethyl malonate under catalysis
of in situ formed Pd-complex of chiral ligands (Scheme 2). For com-
parison, reaction was performed also with BoPhoz ligand, which
was prepared according to known procedures [19]. We chose
(R,R)-configuration of BoPhoz ligand so that it matches relative
configuration of bridged derivatives 3 and 7.
PPh2
PPh2
NMe2
NMe2
Fe
Fe
Fe
2
Me
1
PPh2
Me
Ph2P
N
N
PPh2
Ph2P
Fe
BoPhoz
3
Fig. 1. Aminophosphane Ferrocene and Ferrocenophane ligands.
Ph
Ph
Me
Me
1.
N
O
H2N
Me
2. NaBH4
Fe
Fe
3. HCHO
NaBH4
5
(S,S)-
4
Pd/C
HCO2H
MeOH
Me
N
Me
H
N
PR2
1. BuLi, Et2O
0°C - r.t., 5h
R2P
Fe
Fe
Product of allylic substitution, diester 9, was obtained under
various conditions in good yields but with only mediocre enanti-
oselectivity. Influence of several parameters, including solvent,
temperature and base was investigated. Noteworthy is effect of
base and palladium source on enantioselectivity. The highest
enantioselectivity (55% ee) was obtained with ligand 3 using
Pd2dba3 as a source of palladium. Under same conditions, BoPhoz
ligand afforded product 9 with only 20% ee, but the reaction was
faster. Using [Pd(allyl)Cl]2 the difference in enantioselectivity is
smaller (40% and 33% ee, respectively). Cyclic derivative 10 seems
as a more difficult substrate for ligand 3, even though diester 11
2. ClPR2
6
(S)-
3
R=Ph, (Sp,S)- , 60%
R=Cy, (Sp,S)-7, 47%
Scheme 1.
derivatives [21,22]. Most often nitrogen containing substituents,
such as amines [23,24], oxazolines [25,26], imidazolines [27] were
used as ortho-directing groups. Several other functionalities such
Fig. 2. NOESY spectrum of ligand 3.

1900
R. Šebesta, A. Škvorcová / Journal of Organometallic Chemistry 694 (2009) 1898–1902
Table 2
MeO2C
Ph
CO2Me
Ph
OAc
Ph
Pd-catalyzed allylic substitution on unsymmetrical acetate 12.
Pd/L*
Subtrate
Ligand
[Pd]
Time (h)
Isolated yield (%)
ee (%)a
CH2(CO2Me)2
base, solvent
Ph
12
12
12
12
3
3
[Pd(allyl)Cl]2
26
26
26
26
54
66
69
71
6
0
1
0
8
9
Pd2dba3 ꢁ CHCl3
BoPhoz
BoPhoz
[Pd(allyl)Cl]2
Pd2dba3 ꢁ CHCl3
a
Determined by HPLC on Daicel Chiralpak AD-H column.
MeO2C
CO2Me
OAc
Pd/L*
and without any regioisomer in position 1. However, in all cases,
diester 13 was produced with very low enantioselectivity (6% ee)
or as a racemate (Table 2).
Data of catalytic experiments suggest that introduction of car-
bon bridge into BoPhoz ligand has a positive effect on ligand per-
formance in Pd-catalyzed allylic substitution.
CH2(CO2Me)2
base, solvent
10
11
Scheme 2.
3. Conclusions
Table 1
Pd-Catalyzed allylic alkylation of symmetrical substrates 8 and 10.
We developed efficient method for preparation of phosphane
aminophosphane ferrocenophane derivatives by one-pot double
lithiation of carbon and nitrogen followed by reaction with chloro-
phosphanes. We believe that this procedure could be useful for
preparation of new chiral ferrocene derivatives. Although ferroce-
nophane ligands are only moderately selective in Pd-catalyzed
allylic substitution of acyclic 1,3-diphenylpropenyl acetate (up to
55% ee), this enantioselectivity is higher than that of BoPhoz ligand
for this substrate (33% ee).
Substrate Ligand [Pd]
Base
Solvent Time Isolated ee
(h)
yield
(%)
(%)a
8
8
8
8
8
8
8
8
3
3
3
3
3
3c
3
3
[Pd(allyl)Cl]2
[Pd(allyl)Cl]2
[Pd(allyl)Cl]2
[Pd(allyl)Cl]2
[Pd(allyl)Cl]2
[Pd(allyl)Cl]2
BSA/
KOAc
BSA/
KOAc
BSA/
KOAc
Et2Zn
CH2Cl2
21
86
97
52
40
19
40
(S)
12
(S)
34
(S)
34
(S)
44
(S)b
35
(S)
55
(S)
30
(S)
0
10
(S)
33
(R)
20
(R)
4 (S)d
Toluene 24
THF
24
24
24
THF
BSA/
KOAc
BSA/
KOAc
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
4. Experimental
3.5 98
General: All reactions were carried out in inert atmosphere of N2
or Ar. The solvents were purified by standard methods. Reactions
with organometallic reagents were carried out using standard
Schlenk techniques. NMR spectra were recorded on Varian Mer-
cury plus instrument (300 MHz for 1H, 75 MHz for 13C and
121.5 MHz for 31P) and Varian Inova instrument (600 MHz for
1H). Chemical shifts (d) are given in ppm relative to tetramethylsil-
ane for 1H NMR, relative to residual solvent peak for 13C NMR and
relative to H3PO4 as external standard for 31P NMR. Specific optical
rotations were measured on Perkin–Elmer instrument and are gi-
ven in deg cmꢀ3 gꢀ1 dmꢀ1. Flash chromatography was performed
on Merck silica gel 60. Thin-layer chromatography was performed
on Merck TLC-plates silica gel 60, F-254. Enantiomeric excesses
were determined by HPLC on Chiralpak AD-H (Daicel Chemical
Industries) column using hexane/i-PrOH = 9:1 as a mobile phase
and detection with UV-detector at 254 nm. Mass spectra were re-
corded on Waters Premium QTOF instrument. Compound 5 have
been prepared according to literature procedure [20].
Pd2dba3 ꢁ CHCl3 BSA/
21
21
80
77
KOAc
Pd2dba3 ꢁ CHCl3 BSA/
LiOAc
8
8
3
7
Pd2dba3 ꢁ CHCl3 Cs2CO3
CH2Cl2
CH2Cl2
48
19
95
84
[Pd(allyl)Cl]2
BSA/
KOAc
BSA/
KOAc
8
BoPhoz [Pd(allyl)Cl]2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
3
5
4
1
96
81
70
80
8
BoPhoz Pd2dba3 ꢁ CHCl3 BSA/
KOAc
10
10
3
[Pd(allyl)Cl]2
BSA/
KOAc
BSA/
KOAc
BoPhoz [Pd(allyl)Cl]2
20
(R)d
a
Determined by HPLC on Daicel Chiralpak AD-H column.
Reaction performed at ꢀ25 °C.
b
c
5 mol% of ligand.
d
Determined by NMR using chiral shift reagent tris{3-(heptafluoropropylhydr-
oxymethylene)-d-camphorato}europium(III).
4.1. Preparation of (S)-1,10-(1-methylamino-propanediyl)ferrocene (6)
was obtained in reasonable yield (70%), enantioselectivity was only
small (4% ee). Interestingly, with BoPhoz ligand diester 11 was ob-
tained with 20% ee. Results of Pd-catalyzed allylic substitutions are
summarized in Table 1.
We were also interested whether unsymmetrical acetate 12
would undergo enantioselective allylic substitution (Scheme 3).
Both ligand 3 and BoPhoz afforded solely product 13 in good yields
Palladium on charcoal (10% Pd, 148 mg) was, under nitrogen
atmosphere, suspended in HCOOH/MeOH mixture (1:20, 9 mL)
and amine 5 (500 mg, 1.39 mmol) in HCOOH/MeOH mixture
(1:20, 16 mL) was added into this solution. The resulting mixture
was stirred at r.t. for 2 h. Then it was passed through Celite and sol-
vent was evaporated in vacuum. The crude product was purified by
flash chromatography (SiO2, hexane/EtOAc = 3:1) to give amine 7
(304 mg, 80%) as orange crystals. 1H NMR (300 MHz, CDCl3) d
1.41 (bs, 1H, NH), 1.90–2.02 (m, 1H, CH2), 2.10–2.17 (m, 2H,
CH2), 2.33–2.40 (m, 1H, CH), 2.38 (s, 3H, MeN), 3.03–3.07 (dd, 1H,
J = 7.2, 5.3 Hz, CHN), 3.96–3.98 (m, 1H, CHCp), 4.03–4.10 (m, 6H,
CHCp), 4.23–4.24 (m, 1H, CHCp).
MeO2C
CO2Me
Me
OAc
Me
Pd/L
CH2(CO2Me)2
BSA, KOAc
CH2Cl2
13
12
The NMR data were identical to literature values [34].
Scheme 3.

R. Šebesta, A. Škvorcová / Journal of Organometallic Chemistry 694 (2009) 1898–1902
1901
4.2. Preparation of (S,Sp)-1-diphenylphosphanyl-2,10-[N-diphenyl-
phosphino-1-metylaminopropanediyl]ferrocene (3)
28.2 (d, J(C-P) = 13.4 Hz, CH2), 28.8 (d, J(C-P) = 12.0 Hz, CH2), 29.4
(d, J(C-P) = 7.0 Hz, CH2), 30.0 (d, J(C-P) = 6.3 Hz, CH2), 30.20 (s,
2 ꢂ CH2), 30.23 (d, J(C-P) = 5.1 Hz, CH2), 30.4 (d, J(C-P) = 9.2 Hz,
CH2), 30.9 (d, J(C-P) = 9.0 Hz, CH2), 32.9 (d, J(C-P) = 16.7 Hz, CH2),
33.8 (d, J(C-P) = 21.9 Hz, CH2), 34.2 (bs, MeN), 36.10 (d,
J(C-P) = 17.1 Hz, CHcy), 38.7 (d, J(C-P) = 15.0 Hz, CHcy), 36.13 (dd,
J(C-P) = 16.2, 68.1 Hz, CHN), 39.1 (d, J(C-P) = 8.8 Hz, CH2), 39.2
(d, J(C-P) = 8.7 Hz, CH2), 67.5 (s, CHCp), 70.0 (s, CHCp), 71.0 (s, CHCp),
71.6 (d, J(C-P) = 2.2 Hz, CHCp), 71.8 (s, CHCp), 72.9 (d, J(C-P) = 3.8 Hz,
CHCp), 76.0 (d, J(C-P) = 4.8 Hz, CHCp), 78.5 (d, J(C-P) = 25 Hz, CqCp),
87.6 (dd, J(C-P) = 22.0, 3.3 Hz, CqCp), 89.5 (s, CqCp). 31P NMR
(121 MHz, CDCl3) d ꢀ13.6 (s), 80.4 (bs). ESI HRMS Calc. for
C38H60FeNP2 [M+H]+ 648.3519; found 648.4038.
Amine 6 (483 mg, 1.79 mmol) was dissolved in anhydrous Et2O
(5 mL). The solution was cooled in an ice bath and BuLi (1.6 M in
hexane, 0.8 mL, 1.28 mmol) was added. The resulting mixture
was stirred for 5 h and temperature was allowed to rise to r.t dur-
ing this time. Then the reaction mixture was cooled again in the ice
bath and ClPPh2 (0.25 mL, 1.39 mmol) was added. The mixture was
stirred overnight (0 °C – r.t.). Saturated NaHCO3 solution. (5 mL)
was added and phases were separated. Organic layer was washed
with water, dried (Na2SO4) and concentrated. Flash chromatogra-
phy (SiO2, hexane/EtOAc/Et3N = 66:33:1) followed by crystalliza-
tion from hot iPrOH afforded pure phosphane 3 (686 mg, 60%) as
a yellow solid. M.p. 62–65 °C. [
a]
D = ꢀ199.2 (c = 0.5, CH2Cl2). 1H
4.4. General procedure for allylic substitution of acetates 8, 10 and 12
NMR (300 MHz, CDCl3) d 2.03–2.11 (m, 1H, CH2), 2.15 (d, 3H,
J = 3.9 Hz, MeN), 2.67 (m, 2H, CH2), 3.37–3.50 (m, 1H, CH2), 3.40–
3.41(m, 1H, CHCp), 3.77(dt, 1H, J = 1.3, 2.3 Hz, CHCp), 3.81–3.93
(m, 2H, CHCp, CHN), 4.14 (td, 1H, J = 1.4, 2.5 Hz, CHCp), 4.24 (td,
1H, J = 1.4, 2.5 Hz, CHCp), 4.40–4.42 (m, 1H, CH Cp), 4.43–4.45 (m,
1H, CHCp), 7.06–7.36 (m, 18H, CHPh), 7.48–7.55 (m, 2H, CHPh). 1H
NMR (600 MHz, C6D6) d 1.82 (t, 1H, J = 13.3 Hz, CH2), 2.34 (d, 3H,
J(H-P) = 3.6 Hz, MeN), 2.51 (dt, 1H, J = 3.24, 14.4 Hz, CH2), 2.74–
2.78 (m, 1H, CH2), 3.48 (dd, 1H, J = 2.4, 3.6 Hz, CHCp), 3.54–3.62
(m, 1H, CH2), 3.65 (dt, 1H, J = 1.3, 2.4 Hz, CHCp), 3.89–3.92 (m,
3H, CHN, CHCp), 4.09 (dt, 1H, J = 0.6, 2.5 Hz, CHCp), 4.27 (td, 1H,
J = 1.6, 3.2 Hz, CHCp), 4.44 (m, 1H, CHCp), 6.94–7.00 (m, 3H, CHPh),
7.03–7.08 (m, 6H, CHPh), 7.08–7.14 (m, 3H, CHPh), 7.25–7.28 (m,
2H, CHPh), 7.34–7.36 (m, 2H,CHPh), 7.38–7.41 (m, 2H, CHPh),
7.56–7.59 (m, 2H, CHPh). 13C NMR (75 MHz, C6D6) d 21.2 (s, CH2),
34.9 (t, J(C-P) = 8.3 Hz, MeN), 40.4 (dd, J(C-P) = 12.0, 16.4 Hz, CH2),
67.7 (s, CHCp), 68.0 (d, J(C-P) = 33.6 Hz, CHN), 70.5 (s, CHCp), 71.1
(s, CHCp), 72.1 (s, 2xCHCp), 74.2 (d, J(C-P) = 16.5 Hz, CqCp,), 75.5
(d, J(C-P) = 4.6 Hz CHCp), 76.9 (d, J(C-P) = 5.4 Hz, CHCp), 89.2 (s,
CqCp), 89.4 (dd, J(C-P) = 22.7, 5.84 Hz, CqCp,), 127.9, 128.2, 128.5,
129.0 (s, 12 ꢂ CHPh, overlap with C6D6), 132.2 (d, J(C-P) = 19.2 Hz,
CHPh), 132.9 (d, J(C-P) = 17.8 Hz, CHPh), 133.2 (d, J(C-P) = 20.8 Hz,
CHPh), 135.9 (d, J(C-P) = 21.7 Hz, CHPh), 139.3 (d, J(C-P) = 9.4 Hz,
CHPh), 139.4 (d, J(C-P) = 4.9 Hz, CqPh), 139.6 (d, J(C-P) = 8.8 Hz,
CqPh), 141.7 (d, J(C-P) = 9.9 Hz, CqPh). 31P (121 MHz, CDCl3) d
ꢀ20.2 (d, J = 4.7 Hz), 60.7 (d, J = 4.7 Hz). ESI HRMS Calc. for
C38H35FeNP2Na [M+Na]+ 646.1461; found: 646.1407.
Ligand (0.02 mmol) and [Pd(allyl)Cl]2 or Pd2dba3.CHCl3
(0.01 mmol) were dissolved in CH2Cl2 (3 mL) and stirred for
20 min. This solution was added to
a solution of substrate
(1 mmol) in CH2Cl2 (2 mL). Then bis(trimethylsilyl)acetamide
(2 mmol), dimethylmalonate (2 mmol) and KOAc (0.05 mmol)
were added in this order. The resulting solution was stirred at r.t.
and monitored by TLC (SiO2, hexane/EtOAc 4:1). When all starting
material was consumed, saturated aq. NH4Cl solution (3 mL) and
tBuOMe were added and layers were separated. Organic layer
was washed with brine (10 mL), dried (Na2SO4) and concentrated.
Flash chromatography (SiO2, hexane/EtOAc = 9:1) of the crude
mixture afforded pure allylation product.
4.5. Dimethyl 2-(1,3-diphenylallyl)malonate (9) [35]
1H NMR (300 MHz, CDCl3) d 3.52 (s, 3H, OMe), 3.71 (s, 3H, OMe),
3.95 (d, J = 10.9 Hz, 1H, CH), 4.27 (dd, J = 10.9, 8.5 Hz, 1H, CH), 6.32
(dd, J = 15.7, 8.5 Hz, 1H, CH), 6.48 (d, J = 15.7 Hz, 1H, CH), 7.17–7.35
(m, 10H, Ph). HPLC (AD-H, hexane/i-PrOH 90:10, 0.75 mL/min,
254 nm) tR = 14.13 min (R), tR = 19.08 min (S), 55% ee [
(1.01, CHCl3).
a]
D = ꢀ3.9
4.6. Dimethyl 2-(cyclohex-2-enyl)malonate (11) [36]
1H NMR (300 MHz, CDCl3) d 1.31–1.43 (m, 1H, CH), 1.49–1.84
(m, 3H, CH2), 1.96–2.03 (m, 2H, CH2), 2.86–2.96 (m, 1H, CH2),
3.74 (s, 3H, OMe), 3.75 (s, 3H, OMe), 3.29 (d, J = 9.5 Hz, 1H, CH),
5.50–5.55 (m, 1H, CH), 5.75–5.81 (m, 1H, CH).
4.3. Preparation of (S,Sp)-1-dicyclohexylphosphanyl-2,10-[N-dicyclo-
hexylphosphino-1-metylaminopropanediyl]ferrocene (7)
Amine 6 (270 mg, 1.0 mmol) was dissolved in anhydrous Et2O
(3 mL). The solution was cooled in an ice bath and BuLi (1.6 M in
hexane, 0.8 mL, 1.28 mmol) was added. The resulting mixture
was stirred for 5 h and temperature was allowed to rise to r.t dur-
ing this time. Then the reaction mixture was cooled again in the ice
bath and ClPCy2 (0.62 mL, 2.7 mmol) was added. The mixture was
stirred overnight (0 °C – r.t.). Saturated NaHCO3 soln. (5 mL) was
added and phases were separated. Organic layer was washed with
H2O, dried (Na2SO4) and concentrated. Flash chromatography
(SiO2, hexane/EtOAc/Et3 N = 66:33:1) followed by crystallization
from hot EtOH afforded pure phosphane 7 (302 mg, 47%) as a yel-
4.7. Dimethyl 2-(4-phenylbut-3-en-2-yl)malonate (13) [35]
1H NMR (300 MHz, CDCl3) d 1.19 (d, 3H, J = 6.8 Hz, CH3),
3.08–3.19 (m, 1H, CH), 3.40 (d, J = 8.9 Hz, 1H, CH), 3.67 (s, 3H,
OMe), 3.75 (s, 3H, OMe), 6.12 (dd, J = 15.8, 8.5 Hz, 1H, CH), 6.46
(d, J = 15.8 Hz, 1H, CH), 7.18–7.35 (m, 5H, Ph). HPLC (OD-H, hex-
ane/i-PrOH 99:1, 0.5 mL/min, 254 nm) tR = 19.38 min, tR = 21.46
min.
low solid. M.p.: 150–152 °C. [
a
]
D = ꢀ72.2 (c = 0.5, CH2Cl2). 1H NMR
Acknowledgements
(300 MHz, C6D6) d 1.12–1.56 (m, 22H, Cy), 1.60–2.00 (m, 22H, Cy),
2.34–2.41 (m, 1H, CH2), 2.42–2.55 (m, 2H, CH2), 2.81(s, 3H, MeN),
3.20–3.35(m, 1H, CH2), 3.84 (m, 1H, CHCp), 3.95 (m, 2H, CHCp),
4.00– 4.09 (m, 2H, CHCp, CHN), 4.09–4.11 (m, 1H, CHCp), 4.20 (m,
1H, CHCp), 4.35 (m, 1H, CHCp). 13C NMR (75 MHz, C6D6) d 27.0 (d,
J(C-P) = 10.96 Hz, CH2), 27.1 (d, J(C-P) = 7.9 Hz, CH2), 27.5 (d, J(C-
P) = 2.36 Hz, CH2), 27.67(d, J(C-P) = 5.4 Hz, CH2), 27.71 (d, J(C-
P) = 17.7 Hz, CH2), 27.75(s, 2xCH2), 27.8 (d, J(C-P) = 7.8 Hz, CH2),
We thank Ministry of education of Slovak Republic, Grant No.
MVTS-COST/UK/07, Slovak grant agency VEGA, Grant No. VEGA
1/3569/06, and Comenius University, Grant No. UK/220/2008 for
financial support. We thank Dr. Branislav Horváth for performing
NOESY experiments, NMR measurements were provided by Slovak
State Programme Project No. 2003SP200280203. For performing
HRMS measurements, Dr. Jozef Marák is gratefully acknowledged.

1902
R. Šebesta, A. Škvorcová / Journal of Organometallic Chemistry 694 (2009) 1898–1902
[18] A. Almassy, K. Barta, G. Francio, R. Šebesta, W. Leitner, Š. Toma, Tetrahedron:
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