Enantioselective Catalysis, 101 [1] Synthesis and Coordination Properties of (3′S,4′S)-(+)-1,2-Bis(3′,4′-dimethoxyphospholano) benzene, a New Chiral Diphosphane

Article abstract of DOI:10.1515/znb-1996-0823

A new bisphospholane, BDPB, derived from 1,2-bisphosphanobenzene and tartaric acid as well as the complex [Rh(COD)(BDPB)]PF₆ were synthesized. The strong binding of BDPB to metals and the presence of four functional groups in the periphery of t

Full text of DOI:10.1515/znb-1996-0823

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a rhodium (I) com plex of this ligand. The related
com pound derived from 1,2-bisphosphanoethane
is already reported in the literature but a different
synthetic procedure was used for its preparation
[10], We carried out the synthesis of BD PB b e-
cause of the greater rigidity of the 1,2-phenylene
backbone as com pared to the ethano bridge.
Enantioselective Catalysis, 101 [1]
Synthesis and Coordination Properties
of (3'S,4'S)-(+)-l,2-Bis(3',4'-dim ethoxy-
phospholano)benzene,
Diphosphane
a
New Chiral
H enri B runner*, G em m a N et
Institut für Anorganische Chemie,
Results and Discussion
Universität Regensburg, D-93040 Regensburg.
Germany
The first attem pt to synthesize (3'S,4'S)-(+)-l,2-
bis(3',4'-dim ethoxyphospholano)benzene
Z. Naturforsch. 51b, 1210-1212 (1996);
received February 5. 1996
(B D PB ) was in analogy to the synthesis of D IO P
[11], H ow ever, the dilithium salt of 1,2-bisphos-
phanobenzene did not react with (2S,3S)-(+)-2,3-
dim ethoxytetram ethylen-l,4-bis-/?-toluenesulfona-
te in the desired m anner.
The new bisphospholane B D PB could be finally
obtained using the cyclic sulfate (5S,6S)-(+)-5,6-di-
m ethoxy-l,3,2-dioxathiepane-2,2-dioxide.
sulfates have been shown to be convenient rea-
gents for the synthesis of sim ilar phosphanes [9],
In contrast to the bistosylates, the second nucleo-
philic attack in cyclic sulfates is much slower than
the first one. This favors the desired intram olecu-
lar reaction with respect to an interm olecular a t-
tack leading to oligom erization.
The cyclic sulfate was obtained from the co rre-
sponding dialcohol according to the reactions in
the Schem e. It is a crystalline, rather unstable,
w hite com pound, turning red within several hours
on standing at room tem perature. Its MS spectrum
could not be obtained because of this therm al in-
stability.
Chiral Bisphosphanes. Expanded Phosphanes,
Rhodium Complexes, Cyclic Sulfates
A new bisphospholane, BDPB, derived from
1,2-bisphosphanobenzene and tartaric acid as well
as the complex [Rh(COD)(BDPB)]PF6 were syn-
thesized. The strong binding of BDPB to metals
and the presence of four functional groups in the
periphery of the molecule make this bisphospho-
lane a good starting point for new expanded bis-
phosphanes.
Cyclic
Introduction
C hiral chelating bisphosphanes with two aryl
groups on each phosphorus atom are excellent li-
gands for asym m etric catalysis [2, 3]. T hough the
chirality is usually located close to the phosphorus
atoms, the group of H ayashi achieved high optical
inductions in asym m etric allylations with phos-
phane ligands having the chiral groups at relatively
large distances from the phosphorus atom s [4, 5].
O ur group developed the concept of the expanded
phosphanes, ligands designed to induce long range
effects in enantioselective catalysis [6 - 8]. They
consist of two phosphorus atom s bridged by a rigid
backbone and surrounded by an assem bly of chiral
and nonchiral layers.
Starting from this cyclic sulfate, the desired bis-
phospholane could be obtained in a two step one
pot reaction (see Schem e). The nucleophilic attack
of the phosphide at the second a-carbon atom of
the sulfate takes several hours, a slower process
Phospholane derivatives of 1,2-bisphosphano-
benzene proved to be very good ligands for enanti-
oselective catalysis [9], O ur objective was to syn-
Q
p -
V^OH
a) SOCI2
thesize
a chiral bisphospholane ligand with the
b) Nal04, RuCI3x 3H20
possibility of future expansion. In the present
w ork, we report on the synthesis of a new bisphos-
pholane derived from 1,2-bisphosphanobenzene
and tartaric acid, (3'S ,4'S )-(+ )-l,2-bis(3',4'-di-
m ethoxyphospholano)benzene (B D PB ), as well as
a) 2 BuLi
b) 2 BuLi
h2p
Reprint requests to Prof. Dr. H. Brunner.
0932-0776/96/0800-1210 $06.00 © 1996 Verlag der Zeitschrift für Naturforschung. All rights reserved.
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than sim ilar reactions described in the literature
[9]. The new phosphane BD PB is a white, crystal-
line, strongly smelling, air sensitive com pound.
Since our aim was to design ligands for enan-
tioselective catalysis, and hydrogenation is the
m ost extensively studied reaction in this field,
28.3 g (132.5 m m ol) of N a I0 4 w ere added with
stirring. Two yellow layers form ed which gradually
becam e black. L ater,
a yellow precipitate ap-
peared and the solution becam e yellow again. A f-
ter stirring for 1 h, 400 ml of w ater and 200 ml of
ether w ere added. The two layers were separated
and the aqueous phase was extracted with 3 x 200
ml of ether. The com bined organic extracts were
w ashed with 2 x 100 ml of a saturated aqueous
solution of NaCl and dried over N a2S 0 4. TTie re -
sulting organic solution was filtered through silica
gel and reduced in volum e to 20 ml. Colorless nee-
dles form ed (11.6 g). A fter recrystallization from
ether, 10.0 g of the pure cyclic sulfate were ob-
tained (70.8% yield) which w ere stored below
0°C .
we
synthesized
the
rhodium
com plex
[R h(C O D )(B D P B )]P F 6. The cation was easily
form ed and isolated as its hexafluorophosphate
salt by reaction of an equim olar m ixture of
[R h(/*-C l)(C O D )]2 and A gPF6 with B D PB at
-7 8 °C. W hen the reaction was perform ed at
higher tem perature, m ixtures of com plexes w ere
obtained. A ttem pts to synthesize this com plex
using o th er starting m aterials and counterions al-
ways led to m ixtures containing the cation
[R h (C O D )(B D P B )]+ besides other com ponents.
Sim ilar problem s to obtain this type of com plex
w ere also encountered for other dialkylphos-
phanes derived from 1,2-bisphosphanobenzene
[8],
M elting point: 100-101 °C. [a]D2'’ = + 85.1° (c =
1.0, C H 2C12).
Elemental analysis for Cf,H,20 6S
Calcd
C 33.96 H 5J 0 % ,
Found C 33.98 H 5.79% .
'H N M R (250 M Hz, CDC13, ppm ): 4.59 (2H, d,
J = 13.0 Hz, C H 7); 4.38 (2H, dm, J = 13.0 Hz,
C H 2); 3.49 (2H, m, C H O M e); 3.47 (6 H, s, O M e).
13C{'H} N M R (63 M Hz, CDC13, ppm ): 77.1 (C H -
O M e); 66.8 (C H 2); 57.3 (O C H 3).
Experimental Section
All reactions and m anipulations were p er-
form ed under nitrogen by using standard Schlenk
techniques. Solvents were purified and dried by
standard procedures. 1,2-B isphosphanobenzene
[12],
(2S,3S)-(+)-2,3-dim ethoxy-1,4-butanediol
Synthesis o f (3'S,4'S)-(+)-1,2-bis(3',4'-dimethoxy-
phospholano)benzene (B D PB )
[13] and [R h(p-C l)(C O D )]2 [14] were prepared as
described in the literature.
13 ml (20.0 m m ol) of 1.6 N n-BuLi in hexane
was added dropw ise to a solution of 1.48 g (10.0
m m ol) of 1,2-bisphosphanobenzene in 100 ml of
THF. The pale yellow m ixture was stirred for 1 h
at 20 °C. A fter cooling to 0 °C, the cyclic sulfate
(4.24 g, 20.0 m m ol) was added and the colorless
suspension was stirred for 2 h. Then, 2.2 equiva-
lents of «-BuLi (14.3 ml) w ere added dropw ise at
0 °C, and the orange suspension was stirred over-
night. A fter 18 h, 60 ml of w ater was added to the
pale yellow suspension, and the T H F was evapo-
rated. The m ixture was extracted with 5 x 50 ml of
ether. The ether solution was dried over N a2S 0 4
and the solvent was evaporated. The product was
obtained as an oil which crystallized overnight.
Yield: 2.61 g (6 8% ). [a ]D25 = + 51.9° (c = 0.7,
C H 2C12). MS (EI, LR): m /z = 370.0 (M + ).
’H, 'H {31P], 13C['H} and 3IP{'H} NM R spectra
w ere recorded in deuterated chloroform on
a
B ruker A R X 400 or on a B ruker AC 250 instru-
m ent (21 HC) using TM S as internal standard ('H
and l3C) or H 3P 0 4 as external standard (3IP).
M ass spectra (E I, LR ) were obtained on a Finni-
gan M at 112 S spectrom eter. O ptical rotations
w ere m easured at 24 °C on a P erkin-E lm er 241
polarim eter.
Synthesis o f (5S,6S)-(+)-dimethoxy-1,3,2-dioxathie-
pane-2,2-dioxide
The preparation of the cyclic sulfate is based
upon the m ethod used by Burk et al. to prepare
sim ilar com pounds [9], The m ixture which resulted
by addition of 6.06 ml (9.90 g, 83.2 mmol) of thio-
nyl chloride to a solution of 10.0 g (66.6 m m ol) of
(2S,3S)-(+)-2,3-dim ethoxy-l,4-butanediol in 60 ml
of CC14 was stirred under reflux for 1.5 h. A fter
cooling, the solvent was evaporated to dryness in
a rotary evaporator. The cyclic sulfite, obtained as
a brow n oil, was dissolved in 60 ml of CC14, 60 ml
of C H 3CN and 90 ml of H 20 . A fter cooling to
0 °C, 100 m g (0.38 m m ol) of R uC l3-trihydrate and
Elemental analysis for C,^H^s0 4P->
Calcd
C 58.37 H 7 .6 2 % ,
Found C 58.88 H 7.88% .
31 P{1H} N M R (162 M Hz, CDC13, ppm ): -33.8
(s). 'H {31P} N M R (400 M Hz, CDC13, ppm ): 7.59
(2H, m. H arom); 7.29 (2H, m, H arom); 3.92 (2H, m,
C H O M e); 3.86 (2H , m, C H O M e); 3.35 (6H, s.
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O M e); 3.33 (6H, s, O M e); 2.43 (2H . dd. 7, = 14.5
Hz, J2 = 6.5 Hz. C H ,); 2.25 (2H . dd, 7, = 14.1 Hz,
7, = 5.3 Hz. C H ,); 2.06 (2H. dd. 7, = 14.1 Hz, J2 =
6.3 Hz, C H ,); 1.90 (2H, dd, 7, = 14.5 Hz. 7, = 5.2
Hz. C H ,). 13C{1H} N M R (100 M Hz, C D C l,. ppm )
[15]: 146.7 (m l, N = 5.8 Hz, C arom-P); 131.3 (m2,
N' = 5.6 Hz, C H arom); 129.4 (s, C H arom); 86.9 (C H -
O M e); 86.7 (C H -O M e); 57.4 (O M e); 57.3 ( O M e);
28.8 (m, C H 2).
allowed to warm to room tem perature. The deep
red solution was separated from the AgCl by
filtration and the filtrate was evaporated. C rystal-
lization of the residue from C H 2C12 / pentane gave
838 mg of the red product (78% yield).
Elemental analysis for C?6H4()F60 4P ^Rh
Calcd
C 42.99 H 5.55% ,
Found C 43.15 H 5.59%.
31P ('H )N M R (162 M Hz, CDC13, ppm ): 55.1 (d.
7 = 151.3 Hz); -143.7 (sept. 7 = 713.3 Hz).
Synthesis o f [R h(B D P B )(C O D )JP F 6
372.4 mg (1.48 m m ol) of A gPF6 was added
Acknowledgment
to
a
solution of 363.2 mg (0.74 m m ol) of
Support of this research by the Bayerische Forschungs-
verbund Katalyse (FORKAT) is gratefully acknowledged.
GN thanks the European Community for financial support
(HCM fellowship).
[R h(/i-C l)(C O D )]2 in 10 ml of THF. A solution of
545.6 mg (1.48 m m ol) of B D PB was added drop-
wise at -78 °C. A fter 1 h, the reaction m ixture was
[lljH .B . Kagan. T-P. Dang, J. Am. Chem. Soc. 94,
6429 (1972).
[12] E.P. Kyba, S-T. Liu, R.L. Harris. Organometallics 2,
1877 (1983).
[13] D. Seebach. H-O. Kalinowski, B. Bastani, G. Crass,
H. Daum, H. Dörr, N.P. DuPreez, V. Ehrig, W.
Langer, C. Nüssler, H.A. Oei. M. Schmidt, Helv.
Chim. Acta 60, 301 (1977).
[14] G. Giordano. R.H. Crabtree, Inorg. Synth. 19, 218
(1979).
[15] Second order AA'XX' spectrum, ml and m2 are
multiplets which appear as 1:1:1:1 (m l) and 1:2:1
(m2) signals as if they were first order dd oder t.
respectively. The signals were analysed according to
a) H.M. McConnel, A.D. McLean. C.A. Reilly; J.
Chem. Phys. 23, 1152 (1955) and b) R.J. Abraham,
H.J. Bernstein, Can. J. Chem. 39, 216 (1961). N is
7 pC + pc and N is p^- + ~Jp^-.
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selective Catalysis, Vol. I and II, VCH, Weinheim
(1993).
[3] I. Ojima, Catalytic Asymmetric Synthesis, VCH
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[4] T. Hayashi. K. Kanehira, H. Tsuchiya. M. Kumada.
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[5] T. Hayashi. A. Yamamoto, T. Hagihara, Y. Ito,
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[6] H. Brunner, J. Fürst, J. Ziegler. J. Organomet.
Chem. 454, 87 (1993).
[7] H. Brunner, J. Fürst, Tetrahedron 50, 4303 (1994).
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[9] M.J. Burk. J.E. Feaster, W.A. Nugent, R.L. Harlow.
J. Am. Chem. Soc. 115, 10125 (1993).
[10] H. Brunner. R. Sievi. J. Organomet. Chem. 328, 71
(1987).
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