A convenient method for the synthesis of protic 2-(tertiary phosphino)-1-amines and Their Cp*RuCl complexes

Article abstract of DOI:10.1021/om801042b

A variety of protic 2-(tertiary phosphino)-1-amines (R₂PCH ₂CHR'NHR", PNH) have been prepared from 2-oxazolidinones and secondary phosphines using a newly developed acid-promoted decarboxylatie C-P bond formation reaction. Treatment

Full text of DOI:10.1021/om801042b

390
Organometallics 2009, 28, 390–393
A Convenient Method for the Synthesis of Protic 2-(Tertiary
phosphino)-1-amines and Their Cp*RuCl Complexes
Masato Ito, Akihide Osaku, Chika Kobayashi, Akira Shiibashi, and Takao Ikariya*
Department of Applied Chemistry, Graduate School of Science and Engineering, Tokyo Institute of
Technology, 2-12-1-S1-39 O-okayama, Meguro-ku, Tokyo 152-8552, Japan
ReceiVed October 30, 2008
Scheme 1.
Cp*Ru(L-NH) Catalysts with Ru/NH
Summary: A Variety of protic 2-(tertiary phosphino)-1-amines
(R2PCH2CHR′NHR′′, P-NH) haVe been prepared from 2-ox-
azolidinones and secondary phosphines using a newly deVeloped
acid-promoted decarboxylatiVe C-P bond formation reaction.
Treatment of the resulting chiral P-NH compounds with
Cp*RuCl(isoprene) in CH2Cl2 smoothly furnished chiral
Cp*RuCl(P-NH) complexes with a typical three-legged piano-
stool structure, which proVe to be excellent catalyst precursors
for asymmetric reactions, including the isomerization of allylic
alcohols and hydrogenation of imides.
Bifunctionalities
Recently, optically active nitrogen-containing compounds
have been widely used as versatile ligands in transition-metal-
catalyzed asymmetric reactions.1 We have developed conceptu-
ally new molecular catalyst systems consisting of Cp*RuCl
complexes bearing chelating protic amine (L-NH) ligands and
successfully applied them to a variety of catalytic reactions. The
“Ru/NH bifunctionality”2,3 is a key structural feature of these
catalysts, which facilitates either abstraction or addition of
dihydrogen to enable a number of transformations (Scheme 1).
Scheme 2. Preparation of 2-(Diarylphosphino)-1-amines (2)
from 2-Oxazolidinones (1)
The coordinating elements (L) in the L-NH ligand play a
decisive role in controlling the catalytic performance by tuning
the electron density of the metal center in the molecule of a
catalyst.4 Thus, changing the group L from tertiary amine to
tertiary phosphine causes a significant broadening of applicable
substrates with a polarized C-O bond (polar functionalities)
in the hydrogenation.5 For example, the catalytic hydrogenation
of epoxides,5b imides,5c N-acylcarbamates, and N-acylsulfon-
* To whom correspondence should be addressed. E-mail: tikariya@
apc.titech.ac.jp.
amides5d are effectively promoted by Cp*Ru(P-NH) complexes
but not by Cp*Ru(N-NH), which serve as chemoselective
catalysts for the hydrogenation of ketones.5a The same change
in the structure of the catalyst also leads to considerable rate
enhancement in the reversible oxidation of primary and second-
ary alcohols.6a This extremely rapid hydrogen transfer between
alcohols and carbonyl compounds was successfully applied to
the isomerization of allylic alcohols6b and the selective lacton-
ization of 1,4-diols using acetone.6c These findings prompted
us to explore convenient methods for the chiral modification of
the essential P-NH framework in the ligand for developing
catalytic asymmetric processes.
(1) For example, see: (a) Noyori, R. Asymmetric Catalysis in Organic
Synthesis; Wiley: New York, 1994. (b) ComprehensiVe Asymmetric Catalysis
I-III; Jacobsen, E. N., Pfaltz, A., Yamamoto, H., Eds.: Springer: Berlin,
1999. (c) Catalytic Asymmetric Synthesis, 2nd ed.; Ojima, I., Ed.; Wiley-
VCH: New York, 2000. (d) Fache, F.; Schulz, E.; Tommasino, M. L.;
Lemaire, M. Chem. ReV. 2000, 100, 2159–2231.
(2) For reviews: (a) Noyori, R.; Hashiguchi, S. Acc. Chem. Res. 1997,
30, 97–102. (b) Noyori, R.; Ohkuma, T. Angew. Chem., Int. Ed. 2001, 40,
40–73. (c) Noyori, R.; Yamakawa, M.; Hashiguchi, S. J. Org. Chem. 2001,
66, 7931–7944. (d) Ikariya, T.; Murata, K.; Noyori, R. Org. Biomol. Chem.
2006, 4, 393–406. (e) Ikariya, T.; Blacker, A. J. Acc. Chem. Res. 2007, 40,
1300–1308.
(3) (a) Alonso, D. A.; Brandt, P.; Nordin, S. J. M.; Andersson, P. G.
J. Am. Chem. Soc. 1999, 121, 9580–9588. (b) Yamakawa, M.; Ito, H.;
Noyori, R. J. Am. Chem. Soc. 2000, 122, 1466–1478. (c) Petra, D. G.; Reek,
J. N. H.; Handgraaf, J.-W.; Meijer, E. J.; Dierkes, P.; Kamer, P. C. J.; Brusse,
J.; Shoemaker, H. E.; van Leeuwen, P. W. N. M. Chem. Eur. J. 2000, 6,
2818–2829. (d) Casey, C. P.; Johnson, J. B. J. Org. Chem. 2003, 68, 1998–
2001.
(4) Ito, M.; Ikariya, T. Chem. Commun. 2007, 5134–5142.
(5) (a) Ito, M.; Hirakawa, M.; Murata, K.; Ikariya, T. Organometallics
2001, 20, 379–381. (b) Ito, M.; Hirakawa, M.; Osaku, A.; Ikariya, T.
Organometallics 2003, 22, 4190–4192. (c) Ito, M.; Sakaguchi, A.; Koba-
yashi, C.; Ikariya, T. J. Am. Chem. Soc. 2007, 129, 290–291. (d) Ito, M.;
Koo, L.-W.; Himizu, A.; Kobayashi, C.; Sakaguchi, A.; Ikariya, T. Angew.
Chem., Int. Ed., in press.
Conventionally, the chiral P-NH compounds with a carbon-
centered chirality on the ethylene backbone have been prepared
by reactions of alkali-metal phosphides with partially N-
(6) (a) Ito, M.; Osaku, A.; Kitahara, S.; Hirakawa, M.; Ikariya, T.
Tetrahedron Lett. 2003, 44, 7521–7523. (b) Ito, M.; Kitahara, S.; Ikariya,
T. J. Am. Chem. Soc. 2005, 127, 6172–6173. (c) Ito, M.; Osaku, A.;
Shiibashi, A.; Ikariya, T. Org. Lett. 2007, 9, 1821–1824.
10.1021/om801042b CCC: $40.75
2009 American Chemical Society
Publication on Web 12/23/2008

Communications
Organometallics, Vol. 28, No. 2, 2009 391
Table 1. Reactions of 1a-m with Diarylphosphines in the Presence of TfOH
entry
1
R1
R2
HPAr2
2
yield, %
1
2
3
4
5
6
7
8
9
1a
1b
1c
1a
(S)-1e
(S)-1f
(S)-1g
(S)-1h
(S)-1i
(S)-1j
(S)-1j
(S)-1j
H
CH3
CH2C6H5
H
H
H
H
CH3
HP(C6H5)2
HP(C6H5)2
HP(C6H5)2
2a
2b
2c
2d
(S)-2e
(S)-2f
(S)-2g
(S)-2h
(S)-2i
(S)-2j
(S)-2n
(S)-2o
93
95
80
49
80
88
85
66
70
70
69
66
H
H
H
H
H
H
H
H
H
HP(2-CH3C6H4)2
HP(C6H5)2
CH(CH3)2
CH2CH(CH3)2
C(CH3)3
C6H5
CH2C6H5
CH2C6H5
CH2C6H5
HP(C6H5)2
HP(C6H5)2
HP(C6H5)2
HP(C6H5)2
10
11
12
HP(C6H5)2
HP(4-CH3C6H4)2
HP{3,5-(CH3)2C6H3}2
Scheme 3. Possible Reaction Pathway for the Formation of
2a
Scheme 4. Preparation of 2-(Dialkylphosphino)-1-amines
(2p,q) from 2-Oxazolidinone (1a)
Scheme 5. Preparation of Cp*RuCl(P-NH) Complexes
protected aminoalkyl halides or pseudohalides as a key step.7
However, these methods have certain limitations in synthetic
versatility and substrate scope.8 One notable side reaction is
intramolecular cyclization of partially N-protected aminoalkyl
halides induced by the deprotonation of untouched protons on
nitrogen with highly basic phosphides to form aziridine deriva-
tives.9 In order to preclude this side reaction, we have focused
our attention on the acid-promoted degradation of 2-oxazoli-
dinones (1),10,11 to develop an operationally simple and general
synthetic protocol providing a wide variety of chiral P-NH
compounds. Herein we describe the details of this novel
synthetic method as well as the complexation of the resulting
P-NH compounds with the Cp*RuCl fragment.
toluene for 24 h showed that 1.1 equiv of trifluoromethane-
sulfonic acid (TfOH) promotes the desired decarboxylative C-P
bond formation to give a TfOH salt of 2a, whereas trifluoroacetic
acid, montmorillonite K10, AlCl3, TiCl4, and BF3 · O(C2H5)2 are
not effective promoters under identical conditions. The salt-
free 2a was successfully isolated after treatment with aqueous
K2CO3 in 28% yield. After optimization of the reaction
conditions using TfOH, we found that 2a is obtainable in
reasonably high yield (93%) when the initial molar ratio of 1a,
HP(C6H5)2, and TfOH is set to 1:2:3. It should be noted that
the reduction of the amount of HP(C6H5)2 to 1 equiv markedly
decreased the product yield (60%). As shown in Scheme 2, the
optimized reaction conditions were applicable to the preparation
of a variety of P-NH compounds with a diarylphosphino group.
The reactions of N-substituted 2-oxazolidinones 1b,c with
HP(C6H5)2 proceeded equally well to furnish the secondary
amines 2b,c in high yields (Table 1, entries 2 and 3).
Furthermore, the reaction of 1a with HP(2-CH3C6H4)2 afforded
the corresponding 2d in moderate yield (entry 4).
The advantage of the present method was further demon-
strated by the preparation of chiral P-NH compounds. A wide
variety of chiral 2-oxazolidinones with a stereogenic carbon R
to the nitrogen ((S)-1e-m) afforded the chiral P-NH com-
pounds (S)-2e-m (entries 5-10), in good to excellent yields.12
Additionally, the reactions of (S)-1j with HP(4-CH3C6H4)2 and
HP{3,5-(CH3)2C6H3}2 furnished (S)-2n and (S)-2o in 69% and
66% yields, respectively (entries 11 and 12). Notably, no
measurable loss of optical purity in the products was observed
in this process, since (R)-2j prepared from (R)-1j showed the
specific rotation value of -66 that is opposite in sign to (S)-2j
with +67 (c ) 1.1, CHCl3) (see the Supporting Information).
The delicate balance of stoichiometry for the successful C-P
bond formation can be explained by the possible mechanism
outlined in Scheme 3. Thus, a 3-fold excess of TfOH is required
to fully protonate 1a to generate 1a · TfOH,13 since HP(C6H5)2
Our initial screening of acid promoters in the reaction of a
1:1 mixture of 2-oxazolidinone (1a) and HP(C6H5)2 in refluxing
(7) (a) Ogata, I.; Mizukami, F.; Ikeda, Y.; Tanaka, M. Jpn. Kokai Tokkyo
Koho 1976, 76, 43754; Chem. Abstr. 1976, 85, 124144z. (b) Kashiwabara,
K.; Kinoshita, I.; Ito, T.; Fujita, J. Bull. Chem. Soc. Jpn. 1981, 54, 725–
732. (c) Hiroi, K.; Abe, J. Chem. Pharm. Bull. 1991, 39, 616–621. (d)
Davies, I. W.; Gallagher, T.; Lamont, R. B.; Scopes, D. I. C. J. Chem.
Soc., Chem. Commun. 1992, 335–337. (e) Sakuraba, S.; Okada, T.;
Morimoto, T.; Achiwa, K. Chem. Pharm. Bull. 1995, 43, 927–934. (f) Kanai,
M.; Nakagawa, Y.; Tomioka, K. Tetrahedron 1999, 55, 3843–3854. (g)
Saitoh, A.; Uda, T.; Morimoto, T. Tetrahedron: Asymmetry 1999, 10, 4501–
4511. (h) Saitoh, A.; Achiwa, K.; Tanaka, K.; Morimoto, T. J. Org. Chem.
2000, 65, 4227–4240.
(8) (a) Christoffers, J. HelV. Chim. Acta 1998, 81, 845–852. (b)
Quirmbach, M.; Holz, J.; Tararov, V. I.; Bo¨rner, A. Tetrahedron 2000, 56,
775–780. (c) Anderson, J. C.; Cubbon, R. J.; Harling, J. D. Tetrahedron:
Asymmetry 2001, 12, 923–935.
(9) For the synthesis of related PN compounds using aziridines, see:
(a) Liu, S.-T.; Liu, C.-Y. J. Org. Chem. 1992, 57, 6079–6080. (b) Katagiri,
T.; Takahashi, M.; Fujiwara, Y.; Ihara, H.; Uneyama, K. J. Org. Chem.
1999, 64, 7323–7329. (c) Dahlensburg, L.; Go¨tz, R. J. Organomet. Chem.
2001, 619 (2), 88–98. (d) Caiazzo, A.; Dalili, S.; Yudin, A. K. Org. Lett.
2002, 4, 2597–2600. (e) Krauss, I. J.; Leighton, J. L. Org. Lett. 2003, 5,
3201–3203. (f) Kawamura, K.; Fukuzawa, H.; Hayashi, M. Org. Lett. 2008,
10, 3509–3512.
(10) (a) Jouitteau, C.; Le Perchec, P.; Forestie`re, A.; Sillion, B.
Tetrahedron Lett. 1980, 21, 1719–1722. (b) Poindexter, G. S.; Owens, D. A.;
Dolan, P. L.; Woo, E. J. Org. Chem. 1992, 57, 6257–6265.
(11) For the related base-promoted 2-aminoethylation of thiols, see: (a)
Ishibashi, H.; Uegaki, M.; Sakai, M. Synlett 1997, 915–916. (b) Ishibashi,
H.; Uegaki, M.; Sakai, M.; Takeda, Y. Tetrahedron 2001, 57, 2115–2120.

392 Organometallics, Vol. 28, No. 2, 2009
Communications
Figure 1. Molecular structures of 3e composed of SRu,SC (left) and RRu,SC (right) configurations. Hydrogens, except those on N, are omitted
for clarity.
Figure 2. Molecular structures of 3k composed of SRu,RN,SC (left) and RRu,SN,SC (right) configurations. Hydrogens, except those on N, are
omitted for clarity.
possibly serves as a competing proton acceptor. Also, a 2-fold
excess of HP(C6H5)2 is necessary to maintain a sufficient
concentration of the nonprotonated molecules, which undergo
nucleophilic attack at the 5-position of 1a · TfOH, thereby
allowing the subsequent release of CO2 to produce 2a · TfOH.
Unfortunately, the optimized stoichiometry was not effective
for the reaction of dialkylphosphines, possibly due to their
strongerBrønstedbasicitycomparedtothatofdiarylphosphines.14,15
Nevertheless, the similar C-P bond forming process between
1a and dialkylphosphines was realized when (CH3)3SiOTf was
used in place of TfOH. As shown in Scheme 4, the reaction of
a 1:1 mixture of 1a and HP(c-C6H11)2 or HP{C(CH3)3}2 in
refluxing toluene containing 2 equiv of (CH3)3SiOTf for 24-48
h furnished 2p,q in 23 and 13% yields, respectively. These
results indicate that the highly oxophilic nature of (CH3)3SiOTf
allows selective electrophilic activation of 1a in preference to
dialkylphosphines.
of 3e revealed that it exists in the solid state as two crystallo-
graphically independent molecules with different absolute
configurations17 of SRu,SC and RRu,SC, as shown in Figure 1.
However, the CD2Cl2 solution of complex 3b exhibited only a
single peak at 62.2 ppm and those of the complexes 3e-j also
showed a single peak around 55-60 ppm in the 31P{1H} NMR
at 30 °C. These results suggest that the stereogenic Ru center
in 3a-j might retain its configuration, at least in the solid state,
but epimerizes18 readily in solution to converge into the more
thermodynamically stable diastereomer.19,20
On the other hand, more confusing stereochemical behavior
was observed when the chiral nonracemic ligands (S)-2k,m with
a secondary amino group were used in the complexation. Since
3k with a pyrrolidine ring and 3m with a piperidine ring have
two stereogenic centers at both the Ru and N atoms in addition
to the configurationally fixed carbons, they can be a mixture of
four diastereomeric complexes. However, the 31P{1H} NMR
spectrum of 3k in CD2Cl2 showed only two signals at 59.6 and
61.8 ppm with an intensity of 1:1 that did not change in the
temperatures range from -90 to 30 °C. Also, an X-ray
diffraction study of the single crystal of 3k revealed that it is
composed of two crystallographically independent molecules
with absolute configurations of SRu,RN,SC and RRu,SN,SC, as
shown in Figure 2. Therefore, only two stereoisomers were
preferentially formed among four possible diastereomers in the
formation of 3k, possibly due to the configurational lability
either of the Ru or N atom, but the stereomutation between these
two complexes should require sufficiently high energy even in
solution to allow the observation of two independent signals in
the 31P{1H} spectra.
As we reported previously,5b a mononuclear Cp*RuCl(isoprene)
complex reacted smoothly with P-NH compounds (2) in
CH2Cl2, yielding the corresponding pseudotetrahedral Cp*RuCl-
(P-NH) (3) bearing a primary or secondary NH group (Scheme
5). In principle, the unsymmetrical structure of P-NH com-
pounds inevitably induces a new stereogenic center at the Ru
center upon complexation with a Cp*RuCl fragment.16 Since
complexes 3b,c with a secondary amine ligand have a stereo-
genic center at the N atoms and complexes 3e-j with a primary
amine ligand have a stereogenic center at the configurationally
fixed carbons, they could be a mixture of two diastereomeric
complexes, depending on the absolute configuration at the Ru
center. Indeed, an X-ray diffraction study of the single crystals

Communications
Organometallics, Vol. 28, No. 2, 2009 393
certo Catalysis”) and by the Asahi Glass Foundation (M.I.).
This work was partly supported by the 21 Century COE
Program. We are grateful to Prof. Takayuki Doi and the
personnel at the Tokyo Institute of Technology for the mass
spectrometric analysis.
Supporting Information Available: Text giving experimental
procedures and CIF files giving X-ray crystallographic data for
3e,k,m. This material is available free of charge via the Internet at
http://pubs.acs.org.
OM801042B
(15) A toluene-d8 solution of a 1:1 mixture of HP(C6H5)2 and TfOH
showed a very broad signal centered at-22 ppm in the 31P{1H} NMR
spectrum at 70 °C, while a similar experiment with HP(c-C6H11)2 showed
Figure 3. Molecular structure of 3m. Hydrogens, except those on
N, are omitted for clarity.
1
a quintet at-3.5 ppm with the coupling constant JPD ) 73 Hz. Since the
In contrast, the 31P{1H} NMR spectrum of 3m in CD2Cl2
showed only one signal at 55.0 ppm, and its solid-state structure
determined by X-ray diffraction revealed that it consists of only
one stereoisomer with SRu,RN,SC configuration (Figure 3).
These results led us to conclude that the stereogenic centers
at the nitrogen and carbon atoms alone do not inhibit the
epimerization at the Ru center in solution and hence the absolute
configuration in the solid state should be determined during the
course of crystallization by subtle intramolecular interactions,
although a synergistic combination of multiple stereogenic
elements occasionally retards the epimerization at the Ru center
in solution, as in the case of 3k. The configurational flexibility
of the Ru centers in the Cp*RuCl(P-NH) complexes may be
attributed to the ease of ionic dissociation of their Ru-Cl bonds,
which is in accord with the very long bond lengths (3e,
2.4918(8) Å; 3k, 2.470(2) and 2.489(2) Å; 3m, 2.4881(18) Å).
Also, it should be noted that the chiral complex 3k serves as
an excellent catalyst upon treatment with KO-t-Bu for asym-
metric reactions, including the isomerization of allylic alcohols6b
as well as hydrogenation of symmetrical glutarimides,5c despite
the fact that 3k is composed of a mixture of diastereomeric
molecules both in solution and in the solid state. Therefore, it
will be the subject for a further study to elucidate the
stereochemistry of catalytically active species16c,21 derived from
3k and other chiral complexes in these asymmetric catalytic
processes.22
formation of TfOD by rapid H-D scrambling between toluene-d8 and TfOH
likely precedes the salt formation, the former may indicate an equilibrium
between DP(C6H5)2 and [D2P(C6H5)2]OTf but the latter may suggest the
irreversible formation of [D2P(c-C6H11)2]OTf.
(16) (a) Brunner, H. Acc. Chem. Res. 1979, 12, 250–257. (b) Brunner,
H. AdV. Organomet. Chem. 1980, 18, 151–205. (c) Consiglio, G.; Morandini,
F. Chem. ReV. 1987, 87, 761–778. (d) Brunner, H. Angew. Chem., Int. Ed.
1999, 38, 1194–1208. (e) Ganter, C. Chem. Soc. ReV. 2003, 32, 130–138.
(17) (a) Sloan, T. E. Top. Stereochem. 1981, 12, 1–36. (b) Stanley, K.;
Baird, M. C. J. Am. Chem. Soc. 1975, 97, 6598–6599. (c) Cahn, R. S.;
Ingold, C.; Prelog, V. Angew. Chem., Int. Ed. Engl. 1966, 5, 385–415.
(18) (a) Consiglio, G.; Morandini, F.; Bangerter, F. Inorg. Chem. 1982,
21, 455–457. (b) Morandini, F.; Consiglio, G.; Straub, B.; Ciani, G.; Sironi,
A. J. Chem. Soc., Dalton Trans. 1983, 2293–2298. (c) Ganter, C.; Brassat,
L.; Glinsbo¨ckel, C.; Ganter, B. Organometallics 1997, 16, 2862–2867. (d)
Nishibayashi, Y.; Takei, I.; Hidai, M. Organometallics 1997, 16, 3091–
3093. (e) Koelle, U.; Rietmann, C.; Raabe, G. Organometallics 1997, 16,
3273–3281. (f) Brunner, H.; Neuhierl, T.; Nuber, B. J. Organomet. Chem.
1998, 563, 173–178. (g) van der Zeijden, A. A. H.; Jimenez, J.; Mattheis,
C.; Wagner, C.; Merzweiler, K. Eur. J. Inorg. Chem. 1999, 1919–1930.
(h) Slugovc, C.; Simanko, W.; Mereiter, K.; Schmid, R.; Kirchner, K.; Xiao,
L.; Weissensteiner, W. Organometallics 1999, 18, 3865–3872. (i) Trost,
B. M.; Vidal, B.; Thommen, M. Chem. Eur. J. 1999, 5, 1055–1069. (j)
Onitsuka, K.; Ajioka, Y.; Matsushima, Y.; Takahashi, S. Organometallics
2001, 20, 3274–3282. (k) Brunner, H.; Muschiol, M.; Tsuno, T.; Takahashi,
T.; Zabel, M. Organometallics 2008, 27, 3514–3525.
(19) (a) Cesarotti, E.; Chiesa, A.; Ciani, G. F.; Sironi, A.; Vefghi, R.;
White, C. J. Chem. Soc., Dalton Trans. 1984, 653–661. (b) Consiglio, G.;
Morandini, F. Inorg. Chim. Acta 1987, 127, 79–85. (c) Kataoka, Y.; Saito,
Y.; Nagata, K.; Kitamura, K.; Shibahara, A.; Tani, K. Chem. Lett. 1995,
833–834. (d) Koelle, U.; Bu¨cken, K.; Englert, U. Organometallics 1996,
15, 1376–1383. (e) Rasley, B. T.; Rapta, M.; Kulawiec, R. J. Organome-
tallics 1996, 15, 2852–2854.
(20) The 31P{1H} NMR measurements for 3e at lower temperature (-
90 °C) allowed the observation of a minor signal at higher field with respect
to the major signal with an intensity of 10%, which gradually diminished
to 0% as the temperature was raised to 30 °C. These results support the
notion that the two possible diastereomers are readily interconvertible and
the Ru-centered chirality of 3e in CD2Cl2 is very labile.
In summary, we have developed a convenient method for
the preparation of P-NH compounds starting from readily
available 2-oxazolidinones. These compounds readily afforded
the corresponding Cp*RuCl(P-NH) complexes, which consti-
tute a new family of chiral half-sandwich type Ru complexes
with a stereogenic Ru.16 Studies on the catalytic performance
of these new complexes in our recently developed asymmetric
reactions are underway and will be reported in due course.
(21) Consiglio, Morandini, and co-workers thoroughly investigated the
stereochemistry of some ligand substitution for a series of CpRu[(R)-
(C6H5)2PCH(CH3)CH2P(C6H5)2] complexes: (a) Consiglio, G.; Morandini,
F.; Ciani, G.; Sironi, A. Angew. Chem., Int. Ed. Engl. 1983, 22, 333–334.
(b) Consiglio, G.; Morandini, F.; Ciani, G.; Sironi, A.; Kretschmer, M. J. Am.
Chem. Soc. 1983, 105, 1391–1392. (c) Morandini, F.; Consiglio, G.;
Lucchini, V. Organometallics 1985, 4, 1202–1208. (d) Consiglio, G.;
Bangerter, F.; Morandini, F. J. Organomet. Chem. 1985, 293, C29–C32.
(e) Consiglio, G.; Morandini, F.; Sironi, A. J. Organomet. Chem. 1986,
306, C45–C48. (f) Consiglio, G.; Morandini, F. J. Organomet. Chem. 1986,
310, C66–C68. (g) Morandini, F.; Consiglio, G.; Sironi, A. Gazz. Chim.
Ital. 1987, 117, 61–63.
Acknowledgment. This research was supported by the
MEXT (Nos. 16750073 and 18065017 “Chemistry of Con-
(12) The substituents at the 5-position in 2-oxazolidinones seem to inhibit
the efficient C-P bond-forming process; 5-methyl-, 5-phenyl-, 5,5-
dimethyl-, and 5,5-diphenyl-2-oxazolidinones did not afford any product
under these conditions.
(13) (a) Olah, G. A.; Heiner, T.; Rasul, G.; Prakash, G. K. S. J. Org.
Chem. 1998, 63, 7993–7998. (b) Olah, G. A.; Calin, M. J. Am. Chem. Soc.
1968, 90, 401–404. (c) Armstrong, V. C.; Moodie, R. B. J. Chem. Soc. B
1968, 275–277. (d) Remko, M. Collect. Czech. Chem. Commun. 1988, 53,
1141–1148.
(22) By a similar method reported previously,5b the treatment of the
chloride complex 3e (103 mg, 0.20 mmol) with KOH (11.0 mg, 0.30 mmol)
in 2-propanol (5.0 mL) afforded a novel Cp*RuH complex bearing (S)-2e
(82.0 mg, 85% yield) as a diastereomeric mixture in an approximately 1:1
ratio, which was determined by their hydride signals at-10.6 ppm (d, 2JPH
) 40.3 Hz) and-9.9 ppm (d, 2JPH ) 37.5 Hz) in 1H NMR (THF-d8). This
result contrasts remarkably with the stereospecificity observed in the
conversion of CpRuCl[(R)-(C6H5)2PCH(CH3)CH2P(C6H5)2] to CpRuH[(R)-
(C6H5)2PCH(CH3)CH2P(C6H5)2] with methanolic CH3ONa.21c
(14) Henderson, W. A., Jr.; Streuli, C. A. J. Am. Chem. Soc. 1960, 82,
5791–5794.