Additional data on the synthesis and properties of chiral 1,2- bis(phosphetano)benzenes

Article abstract of DOI:10.1016/S0040-4020(99)00777-2

The synthesis of chiral, C₂-symmetric 1,2-bis(phosphetano)benzenes 2 has been extended to the benzyl-substituted derivative 2c (R=CH₂Ph). Stable ruthenium and palladium complexes containing ligands 2 have been isolated. X- Ray diffraction studies have been performed on the monoborane adduct of 2a (R=i-Pr) and on a palladium(II) complex of 2b (R=Me).

Full text of DOI:10.1016/S0040-4020(99)00777-2

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 95–100
Additional Data on the Synthesis and Properties of
Chiral 1,2-Bis(phosphetano)benzenes
a
a
b
Angela Marinetti,a, Sebastien Jus, Jean-Pierre Genet and Louis Ricard
*
´
ˆ
a
`
´
Laboratoire de Synthese Selective Organique et Produits Naturels, UMR CNRS 7573, E.N.S.C.P.-11, rue Pierre et Marie Curie,
75231 Paris Cedex 05, France
Laboratoire Heteroelements et Coordination, UMR CNRS 1499, Ecole Polytechnique, 91128 Palaiseau Cedex, France
b
´ ´
´
Received 2 March 1999; accepted 29 June 1999
Abstract—The synthesis of chiral, C2-symmetric 1,2-bis(phosphetano)benzenes 2 has been extended to the benzyl-substituted derivative 2c
(RˆCH2Ph). Stable ruthenium and palladium complexes containing ligands 2 have been isolated. X-Ray diffraction studies have been
performed on the monoborane adduct of 2a (Rˆi-Pr) and on a palladium(II) complex of 2b (RˆMe). ᭧ 1999 Elsevier Science Ltd. All rights
reserved.
Introduction
cyclohexyl groups are needed to attain high enantiomeric
excesses, while the methyl substituted derivative gives
moderate to low enantioselectivities. We can reasonably
assume that geometrical constraints related to the four-
membered ring are responsible for the observed trends.
Particularly, the small intracyclic bond angles of the phos-
phetane moiety should entail large exocyclic bond angles at
the phosphorus atom and at the a-carbons. This should
increase the distance between the C2-symmetry axis and
the R substituent in 2, with respect, for instance, to the
analogous phospholane-based DuPHOS ligands.1a An
X-ray diffraction study of the borane complex (S,S)-3a
(Rˆi-Pr) has been performed (ORTEP drawing is given in
Fig. 1. Selected bond angles and distances are reported in
Table 1).
Phosphorus heterocycles are increasingly and successfully
used as chiral building blocks for optically active ligands.1
In such a context the four-membered phosphetane ring has
recently been considered as a chiral synthon,2 which led to
the preparation of, amongst others, 1,2-bis(phosphetano)-
benzenes 2.3 Diphosphines 2 represent a new, easily acces-
sible class of chiral ligands. Their catalytic efficiency has
been demonstrated for the ruthenium-catalyzed hydro-
genation of functionalized carbonyls and studies on further
catalytic applications are in progress. Here we afford addi-
tional information on the synthesis, coordinating behavior,
and structural characterizations for these new diphosphines.
Indeed, the solid state structure shows a C5–P1–C2 angle of
108.0(1)Њ and a P1–C2–C18 angle of 119.3(2)Њ for the tri-
valent phosphetane moiety. Both angles are significantly
larger than the corresponding bond angles in the reported
(COD)Rh(MeDuPHOS)ϩPF6Ϫ complex,5 where they are of
102.5(4) [or 104.2(4)] and 115.3(6) [or 115.6(6)] degrees,
respectively. Thus, compared to the DuPHOS series, more
bulky substituents are required to similarly hinder the phos-
phorus environment in 2, or the metal environment in their
complexes, and consequently afford significant chiral
discrimination.
Results and Discussion
The bis-phosphetanes 2 have been prepared from 1,2-
bis(phosphino)benzene and cyclic sulfates of optically
pure 1,3-diols according to Eq. (1) (Scheme 1).3 Borane
complexation4 has been used to protect the phosphorus
atom toward oxidation in order to facilitate the purification
step.
So far compounds 2 have been prepared for Rˆmethyl,
ethyl, isopropyl and cyclohexyl. Catalytic tests on the
ruthenium-catalyzed hydrogenation offunctionalized ketones
showed that chiral induction increases significantly with
the steric hindrance of the R substituent. At least for the
reactions examined to date, very bulky isopropyl or
From the data in Table 1, the effect of borane complexation
on structural parameters can also be noticed: it appears that
BH3 complexation reduces bond distances and increases
bond angles at the phosphorus atom. This should result
from merely electronic effects; that is, an increased s-char-
acter for the P–C bonds in the borane complex with respect
to the trivalent phosphetane.
Keywords: chiral ligands; 1,2-bis(phosphetano)benzenes; hydrogenation.
* Corresponding author. Tel.: ϩ33-1-44-27-67-42; fax: ϩ33-1-44-07-10-
62; e-mail: marinet@ext.jussieu.fr
0040–4020/00/$ - see front matter ᭧ 1999 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(99)00777-2

96
A. Marinetti et al. / Tetrahedron 56 (2000) 95–100
Scheme 1.
Figure 1. Crystal structure of the 1,2-bis[(S,S)-2,4-diisopropylphosphetano]benzene borane complex 3a. The (S,S)-enantiomorph refined to lower R values,
which is consistent with the expected (S,S)-configuration of the phosphetane moiety.
The nature of the a-substituent being a crucial structural
feature of ligands 2, we briefly examined the availability
of other derivatives within the same series bearing new,
bulky R groups, that is Rˆt-Bu, CH2t-Bu and CH2Ph.
These syntheses require, firstly, preparation of the optically
pure 1,3-diols, of the corresponding cyclic sulfates, and then
reaction with 1,2-bis(phosphino)benzene. According to the
reported method,6,7 the required chiral diols should be avail-
able through ruthenium–Binap catalyzed hydrogenation of
the corresponding 1,3-diketones.
were obtained after crystallization of the crude hydroge-
nation mixtures. On the other hand, the 2,2,8,8-tetra-
methyl-4,6-nonanedione 4e could not be hydrogenated
with adequate selectivity by the ruthenium–Binap catalyst:
the anti diol was obtained in only moderate e.e. (about 70%)
as a mixture with the syn isomer (d.e. of about 50%). Thus,
diol 5e could not suitably be applied to the phosphetane
synthesis.
The cyclic sulfates 1c (RˆCH2Ph) and 1d (RˆCMe3) have
been prepared according to the Sharpless procedure9 (Eq.
(2)) (Scheme 2) and then reacted with the dilithium
1,2-bis(phosphino)benzene as shown in Eq. (1). The
cyclic sulfate 1d failed to react with the lithiated diphos-
phine under the usual reaction conditions, although
Catalytic hydrogenations of 1,5-diphenyl-2,4-pentanedione
4c8 and 2,2,6,6-tetramethylheptanedione 4d afforded the
expected anti diols in high diastereomeric and enantiomeric
excesses. The optically pure diols (S,S)-5c and (R,R)-5d
ϩ
Ϫ
˚
Table 1. Selected bond angles (degrees) and distances (A) for compound 3a. For comparison, the corresponding values for the (COD)Rh(MeDuPHOS) PF6
complex are given from Ref. 1a
Bond distances
Compound 3a
P1–C5
P11–C10
1.840(2)
1.817(2)
1.816(7)
P(1)–C(2)
P(11)–C(12)
1.863(3)
1.851(2)
1.843(8)
P(1)–C(4)
P(11)–C(14)
1.887(3)
1.849(3)
1.842(8)
DuPHOS–Rh
Bond angles
Compound 3a
C5–P1–C2
C10–P11–C12
108.0(1)
111.9(1)
104.2(4)
C5–P1–C4
C10–P11–C14
111.7(4)
116.9(1)
109.0(4)
C2–P1–C4
C12–P11–C14
76.9(1)
80.1(1)
94.4(4)
DuPHOS–Rh

A. Marinetti et al. / Tetrahedron 56 (2000) 95–100
97
Table 2. Ruthenium–2c catalyzed hydrogenations of b-ketoesters. For
comparison, results obtained with other phosphetanes 2 are reported (1%
catalyst, MeOH, 80 bars, 80ЊC, 20 h)
Substrate
Ligand (S,S)-2c
Ligand
e.e.% [conv.]
e.e.%
MeCOCH2CO2Me 85(S)
[conv.]
100
2a RˆiPr
2f RˆCy
2a RˆiPr
2a RˆiPr
86(R) 100
84(R) 100
86(S) 100
PhCOCH2CO2Et
86(R)
87(R)
100
50
iPrCOCH2CO2Et
90(S)
75
Scheme 2.
1-phenyl-2,4-bis(tert-butyl)phosphetane could be obtained
from 1d and dilithiophenylphosphine.10 The cyclic sulfate
1c afforded the expected 1,2-bis(phosphetano)benzene 2c
which was isolated as its monoborane complex 3c in
45% yield. The trivalent phosphetane 2c has been
removed from its borane adduct in quantitative yield by
phosphine–amine exchange with 1,4-diazabicyclo[2.2.2]-
octane, and fully characterized.
and 93.9(t) ppm). When isolated in the pure state, the
major compound does not afford an active catalyst, while
the crude mixture displays acceptable catalytic activity. A
similar behavior has been reported for the ruthenium–Binap
catalyst generated from (Binap)Ru(OCOMe)2 and two
equivalents of HCl.11
More detailed studies are required to establish the precise
nature of the catalytically active species, all the more
because the coordinating properties and behavior of phos-
phetanes 2 toward transition metals are totally unknown to
date. Thus, to get insight into this field, we started studies on
the synthesis and characterization of metal complexes of
phosphetanes 2 by using 2a (Rˆi-Pr) and 2b (RˆMe) as
model substrates. The first examples of ruthenium and palla-
dium complexes containing 2 are described hereafter.
Ruthenium complexes of the bis(phosphetano)benzenes
have been prepared by reacting 2a (Rˆi-Pr) or 2b
(RˆMe) with the (p-cymene)ruthenium dichloride dimer
in a dichloromethane–ethanol mixture12 (Eq. (3)) (Scheme
3). Complexation of 2 takes place in mild conditions.
Subsequent addition of AgBF4 and crystallization afforded
complexes 6a or 6b, respectively, in about 40% yield, as
orange-yellow, air stable solids. 31P-NMR spectra show the
AB patterns characteristic for the ruthenium–p-cymene–
diphosphine complexes: d 85.1 and 96.2 (AB, JP–Pˆ29.9
Hz) for 6a and d 101.8 and 115.2 (AB, JP–Pˆ29.9 Hz) for
6b. Other NMR and analytical data fully support the
proposed structures.
As a preliminary evaluation of the catalytic properties, the
new ligand has been tested as a chiral auxiliary in the
ruthenium catalyzed hydrogenations of b-ketoesters and
compared to the previously reported phosphetanes 2.
Results are given in Table 2. The catalyst amount and con-
ditions for these model reactions are nonoptimized. On the
whole, the catalytic activity as well as the enantioselectivity
levels obtained with 2c are comparable to those obtained
with the isopropyl- and cyclohexyl-substituted phosphe-
tanes 2a and 2f in analogous conditions.
For all the hydrogenation tests performed with ligands 2, the
ruthenium catalyst was prepared in situ from (COD)Ru(2-
methylallyl)2 and the chiral diphosphine by addition of two
equivalents of methanolic HBr. In such conditions
‘(diphosphine)RuBr2’ complexes are supposed to be formed
and act as catalyst precursors.7 When the reaction was
performed with ligand 2b (RˆMe), 31P-NMR analysis of
Palladium complexes of 2a and 2b have also been prepared
by ligand exchange reactions starting from (PhCN)2PdCl2
according to Eq. (4) (Scheme 4). The final products were
purified by crystallization and fully characterized.
the reaction mixture showed the presence of
a
Typical patterns are observed in the 13C-NMR spectra of 7,
due to the virtual coupling of the two phosphorus atoms (see
major compound (dˆ92 ppm) and small amounts of other
ruthenium complexes (dˆ129 ppm; 118.2 (t, Jˆ17.4 Hz)
Scheme 3.

98
A. Marinetti et al. / Tetrahedron 56 (2000) 95–100
for 31P) or on a Bruker 400 spectrometer at 400.13 MHz for
1H, 100.61 MHz for 13C and 161.97 MHz for 31P. Chromato-
graphic separations were performed on neutral alumina
columns.
Ruthenium catalyzed hydrogenations of the b-diketones
4c–e (Eq. (2))
Scheme 4.
Diketone 4c was prepared in 36% yield according to Ref. 8.
Diketone 4e was prepared in 66% yield by Claisen con-
densation of phenyl 3,3-dimethylbutyrate with methyl neo-
pentyl ketone in the presence of LDA and purified via the
copper chelate complex.13
The catalytic hydrogenation of 4c to 5c is given hereafter as
a representative example.
(R,R)-1,5-Diphenyl-2,4-pentanediol (5c). (R)-BINAP (32 mg,
0.05 mmol) and (COD)Ru(2-methylallyl)2 (12.7 mg, 0.04 mmol)
were placed in a 50 mL flask and 2 mL of anhydrous ace-
tone (distilled over K2CO3) were added. To the resulting
Figure 2. 13C-NMR spectrum of 7b: CDCl3, phosphetane ring signals.
suspension was added
a methanolic HBr solution
(0.52 mL, 0.17 M) and the reaction mixture was stirred at
room temperature for 30 min. The solvent was removed
under vacuum. Methanol (10 mL) and 1,5-diphenyl-2,4-
pentanedione (1.0 g, 4 mmol) were added to the reaction
vessel which was then placed in a 250 mL stainless steel
autoclave, under argon. The argon atmosphere was replaced
by hydrogen and the autoclave pressurized to an initial pres-
sure of 70 bars H2. The reaction was allowed to proceed at
50ЊC for 70 h. Complete conversion to the anti diol 5c
Fig. 2). The solid state structure of 7b has also been deter-
mined. The ORTEP drawing, selected bond angles and
distances are given in Fig. 3. Fig. 3 clearly shows the two
untouched phosphetane rings as well as chelation of the
bidentate ligand to palladium. Bond angles and distances
at the phosphorus atom in 7b are very similar to those
observed in the borane complexed moiety of 3a (see above).
Thus, the experiments of Eqs. (3) and (4) confirm that the
1,2-bis(phosphetano)benzenes 2 behave as chelating ligands
and, especially, that Ru(II) and Pd(II) derivatives do not
affect the four-membered phosphetane ring, as required
for catalytic reactions. Further studies on the coordination
chemistry and catalytic properties of ligands 2 are in
progress. Results will be reported later.
1
was confirmed by H NMR analysis: d (CDCl3) 1.73 (t,
3
3JH–Hˆ5.8 Hz, 2H, CH2), 2.79 (d, JH–Hˆ6.6 Hz, 4H,
CH2), 4.22 (m, 2H, CHOH), 7.2–7.3 (m, Ph) ppm. The
product was determined to be Ͼ95% enantiomerically
pure (1H NMR of the Mosher ester prepared from
(S)-MTPA-Cl in pyridine at 60 ЊC for 4 h. 1H NMR
3
of the (R,R)-5c-(R)-MPTA diester: d 1.76 (dd, JH–Hˆ7.4
2
and 5.4 Hz, 2H, CH2), 2.56 (dd, AB, JA–Bˆ13.7 Hz,
3
3JH–Hˆ7.5 Hz, 2H, CH2), 2.91 (dd, AB, JH–Hˆ5.9 Hz,
Experimental
CH2), 3.30 (6H, OMe), 5.24 (m, 2H, CH–O) ppm). The
crude reaction mixture was recrystallized from ether–
pentane to afford the enantiomerically pure diol 5c (1.0 g,
90% yield). The absolute configuration was assigned from
All reactions were carried out under argon in dry solvents.
NMR spectra were recorded on a Bruker AM 200 spectro-
1
meter (200.13 MHz for H, 50.32 MHz for 13C, 81.01 MHz
Figure 3. Solid state structure of (S,S)-7b. Selected bond distances: P(1)–C(4) 1.813(3), P(1)–C(1) 1.841(3), P(1)–C(3) 1.859(4), P(1)–Pd 2.2223(8), Pd–
Cl(2) 2.3707(8). Bond angles: C(4)–P(1)–C(1) 111.1(1), C(4)–P(1)–C(3) 116.1(2), P(1)–C(1)–C(13) 120.0(3), C(1)–P(1)–C(3) 79.5(2), P(1)–Pd–Cl(2)
90.88(3).

A. Marinetti et al. / Tetrahedron 56 (2000) 95–100
99
the optical rotation value, by comparison with literature
The reaction was allowed to proceed for about 30 min at
Ϫ78ЊC, then warmed up to r.t. and stirred for 2 h. Then,
0.3 mL of the BH3·SMe2 complex were added. After hydro-
lysis, the crude mixture was concentrated under vacuum.
Addition of a degassed hexane–ether 1:1 mixture led to a
gelatinous precipitate which was filtered under inert atmo-
sphere. The colorless solution was evaporated and the
residue chromatographed on alumina with a hexane–ether
gradient as eluent. The borane complex 3c was eluted with a
hexane–ether 90:10 mixture. The colorless solid (0.39 g,
45% yield) was recrystallized from ether–pentane. 31P
data14 ([a]Dˆϩ6 (cˆ1, CHCl3)).
(S,S)-2,2,6,6-Tetramethyl-3,5-heptanediol (5d). Hydro-
genation of 4d (5 g, 27 mmol) was performed with 0.25%
of the ruthenium–(R)-BINAP catalyst at 100 bars of hydro-
1
gen pressure, at 80ЊC for 6 days. H NMR (CDCl3) d 0.93
3
(18H, Me), 1.45 (dd, JH–Hˆ5.2 and 7.5 Hz, 2H, CH2), 3.54
(m, 2H, CHOH) ppm. [a]DˆϪ78 (cˆ1, MeOH).
2,2,8,8-Tetramethyl-4,6-nonanediol (5e). Hydrogenation
of 4e was performed on a 2 g scale with 0.5% of Ru–
BINAP catalyst at 50 bar. The reaction mixture was heated
at 50ЊC for 8 days. A 2:1 mixture of the anti and syn diols
was obtained. A small amount of the pure anti diol was
recovered from the crude product after crystallization
3
NMR (C6D6) d 10.0 (d, JP–Pˆ34.3 Hz), 50.8 (broad); 13C
NMR (C6D6) (100.6 MHz, selected data) d 29.4 (d,
1
2JC–Pˆ11.1 Hz, CH2), 31.8 (d, JC–Pˆ6.5 Hz, CH), 32.7
1
(CH2), 32.9 (d, JC–Pˆ4.9 Hz, CH), 36.2 (m, 2CH2), 36.5
(dd, JC–Pˆ40.4 and 8.7 Hz, CH), 38.1 (CH2), 38.5 (d,
1
2
1JC–Pˆ37.9 Hz, PCH), 41.2 (d, JC–Pˆ20.9 Hz, CH2) ppm.
from dichloromethane–ether. Anti-5e: H NMR (CDCl3)
2
3
0.97 (18H, Me), 1.34 (dd, AB, JH–Hˆ14.5 Hz, JH–Hˆ2.9
Mass spectrum (DCI/NH3) m/e 597 (Mϩ1, 38%), 583
(100%). [a]Dˆϩ302 (cˆ0.5, CH2Cl2). Anal. Calcd. for
C40H43BP2: C, 80.54; H, 7.26. Found, C, 78.49; H, 7.14.
3
Hz, 2H, CH2), 1.51 (dd, AB, JH–Hˆ8.1 Hz, 2H, CH2), 1.58
3
(dd, JH–Hˆ6.2 and 5.3 Hz, 2H, CH2), 2.18 (OH), 4.1 (m,
2H, CHOH) ppm.
1,2-bis[(S,S)-2,4-Dibenzylphosphetano]benzene (2c). The
phosphine–borane complex 3c (150 mg, 0.25 mmol) was
reacted with DABCO (30 mg, 0.27 mmol) in benzene
(3 mL) at 50ЊC for 2 h. The reaction mixture was directly
chromatographed under argon on a short alumina column
with hexane–ether 95:5 as eluent. The final product, 2c, was
obtained in quantitative yield as a colorless oil. 31P NMR
Preparation of the cyclic sulfates 1c,d
(R,R)-1,5-Diphenyl-2,4-pentanediol cyclic sulfate (1c). To
a solution of (R,R)-1,5-diphenyl-2,4-pentanediol (0.84 g,
3.3 mmol) in 6 mL CCl4 were added 0.26 mL (3.6 mmol)
of thionyl chloride. The resulting solution was heated at
reflux for 1 h. The solvent was removed on a rotary evapora-
tor and the residue was dissolved in a mixture of CCl4
(2 mL), MeCN (2 mL) and water (3 mL), and cooled to
0ЊC. RuCl3 (about 10 mg, 5×10Ϫ2 mmol) and NaIO4 (1.0 g,
4.9 mmol) were added. The mixture was allowed to warm up
to room temperature and stirred for about 1 h. Ether (30 mL)
was added, the organic phase was separated, washed with
water and dried over MgSO4. The ether solution was filtered
through a pad of silica gel. Evaporation of the solvent
afforded pure 1c which was recrystallized from a hexane–
1
(C6D6) d 11.7; H NMR (C6D6) d 2.0–2.15 (m, 6H), 2.7–
2.9 (m, 10H), 6.8–7.0 (m, Ph); 13C NMR (100.6 MHz,
selected data), (C6D6) d 29.1 (CH), 30.8 (CH2), 33.3 (t,
JC–Pˆ6.7 Hz, CH), 36.8 (CH2), 40.1 (t, JC–Pˆ9.2 Hz, CH2)
ppm.
Ruthenium–2c catalyzed hydrogenations of carbonyl
derivatives. The ruthenium catalyst was prepared as
in Ref.
7
from (COD)Ru(2-methylallyl)2 (3.2 mg,
1×10Ϫ2 mmol) and ligand 2c (7.0 mg, 1:2×10Ϫ2 mmol) in
acetone. After addition of 2.2 eq. of methanolic HBr and
stirring for 30 min, the solvent was evaporated under
vacuum. A solution of the appropriate substrate (1 mmol)
in 1 mL of degassed methanol (or ethanol) was added to the
catalyst. The glass vessel was placed under argon in a stain-
less steel autoclave which was then pressurized with H2 at
80 bars. The reaction was allowed to proceed at 80ЊC for
20 h. Conversion rates were determined by 1H NMR.
Enantiomeric excesses and absolute configurations of the
final alcohols were assigned by GC (Lipodex A column).
1
ether mixture (yield 0.88 g, 85%), colorless solid. H NMR
3
(CDCl3) d 2.04 (t, JH–Hˆ5.6 Hz, 2H, CH2), 3.06 (dd, AB,
3
2JABˆ14.0 Hz, JH–Hˆ7.6 Hz, 2H, CH2), 3.38 (dd, AB,
3JH–Hˆ6.7 Hz, CH2), 5.12 (m, CH–O), 7.15–7.36 (Ph); 13C
NMR (CDCl3) d 30.5 (CH2), 39.7 (CH2), 83.7 (CH–O),
127.3, 128.8, 129.2, 134.9 (Ph) ppm. [a]Dˆϩ33 (cˆ1,
CHCl3).
(S,S)-2,2,6,6-Tetramethyl-3,5-heptanediol cyclic sulfate
(1d). The same procedure as for 1c afforded 1d as a
1
colorless solid in 67% yield. H NMR (CDCl3) d 1.04 (s,
3
Synthesis of the ruthenium complexes 6. [(p-cymene)-
RuCl2]2 (65 mg, 0.11 mmol) was reacted with 2b
18H, Me), 2.02 (t, JH–Hˆ8.1 Hz, 2H, CH2), 4.33 (t,
3JH–Hˆ8.1 Hz, 2H, OCH) ppm. [a]Dˆϩ48 (cˆ1, CHCl3).
(0.24 mmol) in
a dichloromethane (0.5 mL)–ethanol
(1.5 mL) mixture. After 2 h at room temperature, the solvent
was removed under vacuum. The residue was taken up in
dichloromethane (1 mL) and AgBF4 (42 mg, 0.2 mmol) was
added. After a few minutes a pale yellow solid formed
which was separated from the reaction mixture. Recrystal-
lization from dichloromethane–ether afforded pure 6b in
43% yield. The same procedure was applied to the synthesis
of 6a.
1,2-bis[(S,S)-2,4-Dibenzylphosphetano]benzene borane
complex (3c). A solution of 1,2-bis(phosphino)benzene
(0.20 g, 1.4 mmol) in THF (10 mL) was cooled to Ϫ78ЊC
and n-BuLi (2.5 M solution in hexane, 1.2 mL, 2.2 eq.) was
added. After warming to room temperature, the resulting
orange-red solution of dilithium bis(phosphino)benzene
was then added to a solution of the cyclic sulfate 1c
(0.92 g, 2.9 mmol) in THF (150 mL) at Ϫ78ЊC. The reaction
mixture was allowed to warm to room temperature and
stirred for about 1 h. After cooling to Ϫ78ЊC, 2.2 eq. of
s-BuLi (1.3 M solution, 2.4 mL, 3.1 mmol) were added.
6a: Orange solid; 31P NMR (CD2Cl2) d 85.1 and 96.2 (AB,
1
JP–Pˆ29.9 Hz); H NMR (CD2Cl2) d (400.1 MHz, selected

100
A. Marinetti et al. / Tetrahedron 56 (2000) 95–100
3
3
data) d 0.04 (d, JH–Hˆ6.5 Hz, 3H, Me), 0.37 (d, JH–H
ˆ
Me), 19.9 (t, JC–Pˆ8.1 Hz, Me), 20.5 (Me), 22.3 (Me), 29.8
(4×CH), 34.2 (m, CH2), 45.9 (m, PCH), 51.0 (m, PCH),
132.3, 132.5, 132.6, 133.1, 141.2 (t, JC–Pˆ30.1 Hz, C) ppm.
3
6.5 Hz, 3H, Me), 0.53 (d, JH–Hˆ6.6 Hz, 3H, Me), 0.82 (d,
3JH–Hˆ6.4 Hz, 3H, Me), 0.92 (d, JH–Hˆ6.3 Hz, 3H, Me),
3
0.98 (d, 3JH–Hˆ6.3 Hz, 3H, Me), 1.09 (d, 3JH–Hˆ6.4 Hz, 3H,
3
3
1
Me), 1.15 (d, JH–Hˆ6.8 Hz, 3H, Me), 1.27 (d, JH–H
ˆ
7b: 31P NMR (CDCl3) d 100.1; H NMR (CDCl3) d 1.18
3
3
3
6.9 Hz, 3H, Me), 1.34 (d, JH–Hˆ7.0 Hz, 3H, Me), 2.07 (s,
(dd, JH–Pˆ19.0 Hz, JH–Hˆ7.7 Hz, 6H, Me), 1.70 (dd,
3
3
3
Me), 6.18 (d, JH–Hˆ6.3 Hz, 1H, CH),), 6.22 (d, JH–H
ˆ
3JH–Pˆ22.1 Hz, JH–Hˆ7.2 Hz, 6H, Me), 2.5–3.3 (m,
6.0 Hz, 1H, CH), 6.55 (CH), 6.65 (CH), 7.7 (m, 2H), 8.0–
6H), 4.1 (m, 2H), 7.8 (m, 2H), 8.1 (m, 2H); 13C
8.2 (m, 2H); 13C NMR (CD2Cl2; 100.6 MHz, selected data) d
NMR (CDCl3) d 15.6 (Me), 18.1 (Me), 33.6 (m,
1
1
46.4 (d, JC–Pˆ33.1 Hz, PCH), 49.3 (d, JC–Pˆ31.4 Hz,
PCH), 38.2 (m, PCH), 39.5 (m, CH2), 140.8 (t, JC–P
29.3 Hz, C) ppm. [a]Dˆϩ148 (cˆ0.3, CHCl3).
ˆ
1
1
PCH), 51.7 (d, JC–Pˆ30.4 Hz, PCH), 56.4 (d, JC–P
ˆ
2
37.5 Hz, PCH), 87.1 (d, JC–Pˆ9.1 Hz, CH-p-cymene), 87.5
(d, 2JC–Pˆ8.8 Hz, CH-p-cymene), 89.9 (CH-p-cymene), 95.7
(C-p-cymene), 98.2 (CH-p-cymene) ppm. Anal. Calcd. for
C34H54BClF4P2Ru: C, 54.59; H, 7.27. Found, C, 53.41; H,
7.13.
References
1. For selected references see: (a) Burk, M. J.; Gross, M. F.;
Harper, T. G. P.; Kalberg, C. S.; Lee, J. R.; Martinez, J. P. Pure
Appl. Chem. 1996, 68, 37 and references therein. (b) Jiang, Q.;
Jiang, Y.; Xiao, D.; Cao, P.; Xhang, X. Angew. Chem. 1998,
110, 1203. (c) Dierkes, P.; Ramdeehul, S.; Barloy, L.; De Cian,
A.; Fischer, J.; Kamer, P. C. J.; van Leeuwen, P. W. N.; Osborn,
J. A. Angew. Chem., Int. Ed. Engl. 1998, 37, 3116.
2. Marinetti, A.; Kruger, V.; Buzin, F.-X. Coord. Chem. Rev.
1998, 178–180, 755.
3. (a) Marinetti, A.; Kruger, V.; Buzin, F.-X. Tetrahedron Lett.
6b: Yellow solid; 31P NMR (CD2Cl2) d 101.8 and 115.2
1
(AB, JP–Pˆ29.9 Hz); H NMR (CD2Cl2, selected data) d
3
3
0.86 (dd, JH–Pˆ18.2 Hz, JH–Hˆ7.2 Hz, 3H, Me), 1.14
(3JH–Hˆ6.9 Hz, Me), 1.23 (3JH–Hˆ6.8 Hz, Me), 1.0–1.2
(m, Me), 1.5–1.7 (2 Me), 2.11 (s, Me), 6.18 (d,
3JH–Hˆ6.0 Hz, CH-p-cymene), 6.30 (d, JH–Hˆ6.5 Hz,
3
3
CH-p-cymene), 6.60 (d, JH–Hˆ6.2 Hz, CH-p-cymene),
3
6.70 (d, JH–Hˆ6.5 Hz, CH-p-cymene), 7.7 (m, 2H), 8.2
(m, 2H); 13C NMR (CD2Cl2; 100.6 MHz, selected data) d
ˆ
1997, 38, 2947. (b) Marinetti, A.; Genet, J.-P.; Jus, S.; Blanc, D.;
1
1
Ratovelomanana-Vidal, V. Chem. Eur. J. 1999, 5, 1160.
4. For a recent review on phosphine–borane complexes see: Ohff,
33.8 (d, JC–Pˆ40.8 Hz, PCH), 35.1 (d, JC–Pˆ33.7 Hz,
PCH), 39.1 (d, 1JC–Pˆ34.4 Hz, PCH), 39.4 (d,
2JC–Pˆ15.9 Hz, CH2), 39.6 (d, JC–Pˆ11.6 Hz, CH2), 41.6
2
¨
M.; Holz, J.; Quirmbach, M.; Borner, A. Synthesis 1998, 1391.
1
5. Burk, M. J.; Feaster, J. E.; Nugent, W. A.; Harlow, R. L. J. Am.
Chem. Soc. 1993, 115, 10125.
6. Noyori, R. Asymmetric Catalysis in Organic Synthesis; Wiley:
New York, 1994, pp 1–93 and references therein.
(d, JC–Pˆ39.7 Hz, PCH), 86.8, 90.4, 93.5, 97.6 (CH-p-
cymene), 139.1 (dd, JC–Pˆ37.2 and 27.2 Hz, PC), 140.1
(dd, JC–Pˆ33.3 and 26.7 Hz, PC) ppm. Anal. Calcd. for
C26H38BClF4P2Ru: C, 49.1; H, 6.02. Found, C, 48.82; H,
6.09.
ˆ
7. (a) Genet, J. P.; Pinel, C.; Ratovelomanana-Vidal, V.; Mallart,
S.; Pfister, X.; Bischoff, L.; Can˜o De Andrade, M. C.; Darses, S.;
Synthesis of the palladium complexes 7. A solution of the
bis(phosphetane) 2b (42 mg, 0.15 mmol) in dichloro-
methane (1 mL) was added to a CH2Cl2 solution of
(PhCN)2PdCl2 at room temperature. After a few minutes,
the solvent was removed under vacuum and the residue
recrystallized from CH2Cl2–ether. Crystals for X-ray
studies were grown from a CDCl3–ether mixture. Complex
7b was obtained as an almost colorless solid in 64% yield
(44 mg). The same procedure was applied to the synthesis of
complex 7a.
Galopin, C.; Laffitte, J. A. Tetrahedron: Asymmetry 1994, 5, 675.
ˆ
For recent reviews see: (b) Genet, J. P. In Advances in Asymmetric
Synthesis; Stephenson, G. R., Ed.; Chapman & Hall: London,
ˆ
1996; pp 60–92. (c) Ratovelomanana-Vidal, V.; Genet, J.-P.
J. Organomet. Chem. 1998, 567, 163.
8. Bryant, D. R.; Hauser, C. R. J. Org. Chem. 1962, 27, 694.
9. Gao, Y.; Sharpless, K. B. J. Am. Chem. Soc. 1988, 110, 7538.
10. Marinetti, A. et al., unpublished results.
11. Mashima, K.; Hino, T.; Takaya, H. J. Chem. Soc., Dalton
Trans. 1992, 2099.
12. Mashima, K.; Kusano, K.; Sato, N.; Matsumura, Y.; Nozaki,
K.; Kumobayashi, H.; Sayo, N.; Hori, Y.; Ishizaki, T.; Akutagawa,
S.; Takaya, H. J. Org. Chem. 1994, 59, 3064.
13. Nonhebel, D. C.; Smith, J. J. Chem. Soc. (C) 1967, 1919.
14. Rychnovsky, S. D.; Griesgraber, G.; Zeller, S.; Skalitzky, D. J.
J. Org. Chem. 1981, 56, 5161.
1
7a: Pale yellow solid; 31P NMR (CDCl3) d 92.5; H NMR
3
(CDCl3) d 0.40 (d, JH–Hˆ6.5 Hz, 6H, Me), 0.89 (d,
3
3JH–Hˆ5.9 Hz, 12H, Me), 0.92 (d, JH–Hˆ6.3 Hz, 6H,
Me), 1.92 (m, 2H), 2.5–3.1 (m, 8H), 3.7 (m, 2H), 7.8 (m,
2H), 8.1 (m, 2H); 13C NMR (CDCl3) d 19.7 (t, JC–Pˆ7.5 Hz,