Configurationally stable metal-centered chirality: Stereospecific and regioselective rhodaacylation of alkynes controlled by the third generation of the [Cp'-P]H ligand

Article abstract of DOI:10.1039/b001735n

The rhodium cationic complex [[η⁵:η¹-{3-(NIM)Ind-P}(n = 2)]Rh(CO)Me]BF₄ (1) reacts with 1-phenylpropyne regioselectively and stereospecifically to afford the alkenyl complex [[η⁵:η¹-{3-(NIM)Ind- P}(n

Full text of DOI:10.1039/b001735n

Configurationally stable metal-centered chirality: stereospecific and
regioselective rhodaacylation of alkynes controlled by the third generation of
the [CpA-P]H ligand
Yasutaka Kataoka,* Yoko Iwato, Atsushi Shibahara, Tsuneaki Yamagata and Kazuhide Tani*
Department of Chemistry, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531,
Japan. E-mail: tani@chem.es.osaka-u.ac.jp
Received (in Cambridge, UK) 3rd March 2000, Accepted 7th April 2000
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1
The rhodium cationic complex [[h +h -{3-(NIM)Ind-
P}n = 2]Rh(CO)Me]BF4 (1) reacts with 1-phenylpropyne
regioselectively and stereospecifically to afford the alkenyl
olefin, are possible, this transformation totally has the potential
for the formation of the eight isomers. The results, however,
indicated that only one isomer was produced from each
diastereomer of 1; the isomer ratio of 2 was the same as that of
the starting complex 1.† Thus, the metal-centered chirality did
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1
2
complex
[[h +h -{3-(NIM)Ind-P}n = 2]Rh{h -ONC(CH3)-
C(CH3)NCPh}]BF4 (2).
The design and synthesis of novel chiral transition-metal
complexes having a stereogenic metal center provide an elegant
and powerful method for stoichiometric or catalytic asymmetric
transformations.1–5 Nonetheless, chemistry using metal-cen-
tered chirality is much less developed than that using chiral
auxiliaries or ligands.6 In order to accomplish asymmetric
reactions using metal-centered chirality, easy and convenient
methods for the preparation of optically active complexes which
are configurationally stable at the metal center should be
supplied. Recently we have found that the third generation of
the [CpA-P]H ligand, [{3-(NIM)Ind-P}n = 2]H was effective for
controlling the central metal chirality in the oxidative addition
of alkyl halide to the Rh carbonyl complex, compared to the first
and the second generation of the [CpA-P]H ligand.7,8 Thus,
oxidative addition using metal complexes with the third
generation of the CpA-P ligand could become a new preparation
of an optically active complex having a metal-centered
chirality. In order to use the chiral complex as an asymmetric
catalyst, racemization or epimerization at the metal center must
be prevented. Herein we show that the metal-centered chirality
controlled by the {3-(NIM)Ind-P}n = 2 ligand9 is configuration-
ally stable, which causes the stereospecific and regioselective
addition of alkynes to its cationic Rh complex.
Scheme 1
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1
The cationic rhodium complex, [[h +h -{3-(NIM)Ind-
P}n = 2]Rh(CO)Me]BF4 (1), which was readily prepared from
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1
[h :h -{3-(NIM)Ind-P}n = 2]RhI(COMe) and AgBF4,8 is a
mixture of two diastereomers (major+minor = 96+4, 92% de).†
Reaction of complex 1 with 1-phenylpropyne in CH2Cl2 at
room temperature for 48 h afforded the alkenyl complex 2 in
79% isolated yield (Scheme 1).‡ From the 1H or 31P NMR of the
reaction mixture, 2 was found to contain only two isomers
(major+minor = 96+4). The structure of 2-major was confirmed
by the usual spectroscopic methods as well as X-ray crystallog-
raphy (Fig. 1).§ The stereochemistry around the Rh is S, and the
planar chirality is R. Complex 2 was produced through
migratory insertion of CO into the Rh–Me bond in 110 and the
subsequent rhodaacylation of the alkyne,11 followed by intra-
molecular coordination of the acyl oxygen to the Rh. Since four
isomers from each diastereomer of 1, based on the difference in
the metal-centered chirality and the regiochemistry of the
Fig. 1 ORTEP drawing of the X-ray crystal structure of the cationic part of
2-major. Selected bond lengths (Å) and angles (°): Rh–O 2.0719(15), Rh–P
2.2690(6), Rh–C(36) 2.023(2), C(36)–C(35) 1.362(3), C(34)–C(35)
1.428(4), O–C(34) 1,258(3); Rh–O–C(34) 114.79(17), Rh–C(36)–C(35)
115.13(19), Rh–P–C(11) 105.86(12), O–C(34)–C(35) 118.5(2), C(36)–Rh–
O 77.98(8), C(34)–C(35)–C(36) 113.5(2). The shortest interatomic distance
between the indenyl group and the phenyl ring is 3.278(4) Å.
DOI: 10.1039/b001735n
Chem. Commun., 2000, 841–842
This journal is © The Royal Society of Chemistry 2000
841

522. MS (FAB) m/z 727 (M+ 2 BF4, cationic part of 2). Anal. Found: C,
64.92; H, 6.10%. Calcd. for C44H49BF4OPRh: C, 64.88; H, 6.06%.
§ Crystal data for C44H49BF4OPRh 2-major: M = 814.52, triclinic, a =
10.0645(14), b = 10.9349(13), c = 9.9598(13) Å, a = 108.124(9), b =
106.426(10), g = 84.967(11)°, U = 999.2(2) Å3, T = 296 K, space group
P1 (No. 1), Z = 1, m(Mo-Ka) = 0.519 mm21, 18387 reflections measured,
17568 unique (Rint = 0.0099) which were used in all calculations. R1(all)
= 0.0416, R1(obsd) = 0.0316 ( > 2s(I)), wR2(all) = 0.0875, wR2(obsd) =
0.0826 ( > 2s(I)). CCDC 182/1600. See http://www.rsc.org/suppdata/cc/b0/
b001735n/ for crystallographic files in .cif format.
¶ Spectroscopic data for 4: mp 155–157 °C (dec.). dH (CDCl3, major) 0.29
(d, J = 0.8 Hz, 9 H), 0.49 (d, J = 6.3 Hz, 3 H), 0.89 (d, J = 6.9 Hz, 3 H),
1.02–1.21 (m, 1 H), 1.11 (d, J = 6.0 Hz, 3 H), 1.51–1.73 (m, 2 H), 1.64–1.89
(m, 3 H), 1.93–2.23 (m, 3 H), 2.28 (s, 3 H), 2.37–2.65 (m, 1 H), 2.98–3.28
(m, 2 H), 3.45–3.68 (m, 1 H), 3.86–4.06 (m, 1 H), 5.58 (s, 1 H), 7.01–7.15
(m, 3 H), 7.31–7.42 (m, 4 H), 7.48–7.65 (m, 4 H), 7.67–7.78 (m, 3 H) and
9.06 (dd, J = 11.8, 1.6 Hz, 1 H). 31P{1H} NMR (CDCl3) d 63.7 (d, JP–Rh
= 184 Hz, major) and 64.0 (d, JP–Rh = 179 Hz, minor). 13C{1H} NMR
(CDCl3): d 232.8 (dd, J = 28, 15 Hz, C(H)NCSi(CH3)3, major). IR (KBr,
Nujol, cm21) 3098, 3060, 1526, 1309, 1251, 1063, 845, 755, 709, 694 and
521. MS (FAB) m/z 709 (M+ 2 BF4, cationic part of 4). Anal. Found: C,
60.45; H, 6.54%. Calcd. for C40H51BF4OPRhSi: C, 60.31; H, 6.45%.
not racemize or epimerize throughout these transformations and
the regiochemistry of the olefinic part was completely con-
trolled.
The mixed ligand complex containing both an indenyl and a
tertiary phosphine ligand which are not connected by a spacer,
5
[Rh(h -C9H7)(PPh3)(CO)Me]BF4, did not react with 1-phenyl-
propyne at room temperature. Although the cationic complex
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1
having the second generation CpA-P ligand, [[h +h -(Ind-
P)n = 2]Rh(CO)Me]BF4, with 46% de (major+minor = 73+27)
also reacted with 1-phenylpropyne under the same conditions,
the corresponding alkenyl complexes comprised four diaster-
eomers (69+24+5+1).† The third generation of the [CpA-P]H
ligand was much more effective for controlling the ster-
eochemistry in this rhodaacylation.
Reaction of 1 (92% de) with phenyl acetylene in CH2Cl2 at
room temperature for 12 h gave the corresponding alkenyl
complex 3 with 92% de (Scheme 1).† The diastereomer excess
of 3 was also almost the same as that of 1. This reaction also
1
proceeded stereospecifically. H NMR of 3 showed a doublet
with a small coupling constant (J = 1.4 Hz) at d 6.21 for the
olefinic proton and the HMQC spectrum showed that the proton
was correlated to the b-olefinic carbon from Rh. Reaction of
complex 1 (92% de) with trimethylsilylacetylene under the
same conditions afforded the alkenyl complex 4 with 91% de
(Scheme 1).†¶ This reaction also proceeded stereospecifically,
but the opposite regioisomer to the product of the reaction with
phenylacetylene was obtained. The structure of 4-major was
confirmed by the usual spectroscopic methods as well as X-ray
1 For a review of optically active organometallic compounds having a
metal-centered chirality, see: H. Brunner, Angew. Chem., Int. Ed., 1999,
38, 1194.
2 For example from the Davies lab, see: S. G. Davies, Aldrichim. Acta,
1990, 23, 31 and references cited therein.
3 For example from the Faller lab, see: J. W. Faller, J. T. Nguyen and
M. R. Mazzieri, Appl. Organomet. Chem., 1995, 9, 291 and references
cited therein.
4 For an example from the Gladysz lab, see: J. A. Gladysz and B. J.
Boone, Angew. Chem., Int. Ed. Engl., 1997, 36, 550 and references cited
therein.
5 B. Therrien and T. R. Ward, Angew. Chem., Int. Ed., 1999, 38, 405; D.
Carmona, C. Vega, F. J. Lahoz, S. Elipe, L. A. Oro, M. P. Lamata, F.
Viguri, R. García-Correas, C. Cativiela and M. P. López-Ram de Víu,
Organometallics, 1999, 18, 3364 and references cited therein; C.
Slugovc, W. Simanko, K. Mereiter, R. Schmid and K. Kirchner,
Organometallics, 1999, 18, 3865.
6 Catalytic Asymmetric Synthesis, ed. I. Ojima, VCH, New York, 1993;
R. Noyori, Asymmetric Catalysis in Organic Synthesis, Wiley, New
York, 1994; S.-P. Jacqueline, Chiral Auxiliaries and Ligands in
Asymmetric Synthesis, Wiley, New York, 1995.
7 Y. Saito, T. Yamagata, Y. Kataoka and K. Tani, The 41st Symposium
on Organometallic Chemistry, Japan, 1994, abst. PA.109; Y. Kataoka,
Y. Saito, K. Nagata, K. Kitamura, A. Shibahara and K. Tani, Chem.
Lett., 1995, 833; Y. Kataoka, Y. Saito, A. Shibahara and K. Tani, Chem.
Lett., 1997, 621; Y. Kataoka, A. Shibahara, T. Yamagata and K. Tani,
Organometallics, 1998, 17, 4338.
1
crystallography. H NMR revealed a doublet of doublets at d
9.06 (J = 11.8 and 1.6 Hz) for the olefinic proton originating
from the terminal acetylenic hydrogen. When trimethylsilyl-
acetylene was used, the bulkier indenyl Rh moiety would attack
the less hindered acetylenic terminal carbon selectively in the
rhodaacylation process. In contrast, in the rhodaacylation of
1-phenylpropyne or phenylacetylene, the Rh–carbon bond was
formed at the more hindered site.12
We are currently investigating application of the reaction to
the stereoselective synthesis of general substituted olefins using
a catalytic amount of a rhodium complex containing the CpA-P
ligand. This work was supported by a Grant-in-Aid for
Scientific Research from the Ministry of Education, Science,
Sports, and Culture of Japan, and General Sekiyu Research &
Development Encouragement & Assistance Foundation.
Notes and references
† The isomer ratio was determined by 31P NMR of the crude product
obtained after removal of the solvents from the reaction mixture.
8 Y. Kataoka, Y. Iwato, T. Yamagata and K. Tani, Organometallics,
1999, 18, 5423.
‡ Preparation of 2: to a solution of 1 (20 mg, 0.028 mmol, 92% de) in
CH2Cl2 (5 mL) was added 1-phenylpropyne (4 mL, 0.032 mmol) at room
temperature. The reaction mixture was stirred for 48 h and then the solvent
was removed in vacuo to give orange powders, which contained a
diastereomeric mixture of 2. The ratio was determined by 31P NMR (major
: minor = 94+6, 92% de). After washing with Et2O (10 mL) and hexane (2
3 10 mL), recrystallization of the crude product from CH2Cl2 and Et2O
afforded 2 (18 mg, 0.022 mmol, 79%, major : minor = 94+6, 92% de) as
analytically pure orange powders, mp 118–122 °C (dec.). dH (CDCl3,
major) 0.37 (d, J = 6.3 Hz, 3 H), 0.86 (d, J = 6.6 Hz, 3 H), 1.15 (d, J = 6.0
Hz, 3 H), 1.42 (d, J = 1.6 Hz, 3 H), 1.48–1.89 (m, 6 H), 1.92–2.10 (m, 2 H),
2.38 (d, J = 2.2 Hz, 3 H), 2.30–2.53 (m, 2 H), 2.69–2.98 (m, 2 H), 3.82–3.99
(m, 1 H), 4.05–4.23 (m, 1 H), 5.39 (s, 1 H), 6.15 (dd, J = 8.2, 1.1 Hz, 2 H),
6.29–6.38 (m, 1 H), 6.40–6.48 (m, 1 H), 6.83–6.93 (m, 1 H), 6.99–7.09 (m,
1 H), 7.16–7.41 (m, 8 H), 7.46–7.61 (m, 3 H) and 7.87–7.99 (m, 2 H).
31P{1H} NMR (CDCl3) d 55.1 (d, JP–Rh = 179 Hz, major) and 62.0 (d, JP–Rh
= 181 Hz, minor). 13C{1H} NMR (CDCl3) d 232.2 (dd, J = 26, 12 Hz,
CNC(Ph), major). IR (KBr, Nujol, cm21) 1544, 1261, 1058, 727, 694 and
9 {3-(NIM)Ind-P}n = 2 is the anion of the [{3-(NIM)Ind-P}n = 2]H
ligand.
10 K. J. Carvell, Coord. Chem. Rev., 1996, 155, 209 and references cited
therein.
11 T. Mise, P. Hong and H. Yamazaki, Chem. Lett., 1982, 401; P. Hong, T.
Mise and H. Yamazaki, J. Organomet. Chem., 1987, 334, 129; I. Ojima,
J. Zhu, E. S. Vidal and D. F. Kass, J. Am. Chem. Soc., 1998, 120,
6690.
12 Although DeShong et al. reported that regiochemistry in the insertion of
an unsymmetrical alkyne into the Mn–carbon bond was controlled by
the electronic character of the substituents of the alkyne,13 we think that
one of the reasons for the regioselectivity in the reaction of
arylacetylenes could be the p–p stacking between the phenyl ring and
the indenyl benzene ring. The presence of the p–p stacking could be
also supported by the X-ray crystallographic analysis of 2-major (Fig.
1).
13 P. DeShong, D. R. Sidler, P. J. Rybczynski, G. A. Slough and A. L.
Rheingold, J. Am. Chem. Soc., 1988, 110, 2575.
842
Chem. Commun., 2000, 841–842