Application of chiral tetrahydropentalene ligands in rhodium-catalyzed 1,4-addition of (E)-2-phenylethenyl- and (Z)-propenylboronic acids to enones

Article abstract of DOI:10.1016/j.tetlet.2012.04.130

Chiral tetrahydropentalenes (3aR,6aR)-1 have been prepared and used as ligands in the Rh-catalyzed 1,4-addition of 1-alkenylboronic acids to cyclic enones 5. It has been discovered that the stereochemistry of the reaction was controlled by the steric properties of the aryl groups in 1 rather than their electronic nature. In the vinylation with (E)-2-phenylethenylboronic acid 5, ligands (3aR,6aR)-1 provided enantioselectivity up to 87% ee and gave high yields of ethenylketones 6 in the presence of 1 (6.6 mol %). The configuration of all ketone products obtained with (3aR,6aR)-1 is (S). Rh-catalyzed reaction of cyclopentenone 4a and (Z)-propenylboronic acid 7 in the presence of ligands (3aR,6aR)-1 yielded at 50 °C an inseparable mixture of (Z)- and (E)-ketones 8 with (Z)-8 as the major product and both in only moderate enantiomeric excess.

Full text of DOI:10.1016/j.tetlet.2012.04.130

Tetrahedron Letters 53 (2012) 3506–3509
Contents lists available at SciVerse ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Application of chiral tetrahydropentalene ligands in rhodium-catalyzed
1,4-addition of (E)-2-phenylethenyl- and (Z)-propenylboronic acids to enones
⇑
Sarah Helbig, Kirill V. Axenov, Stefan Tussetschläger, Wolfgang Frey, Sabine Laschat
Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Chiral tetrahydropentalenes (3aR,6aR)-1 have been prepared and used as ligands in the Rh-catalyzed 1,4-
addition of 1-alkenylboronic acids to cyclic enones 5. It has been discovered that the stereochemistry of
the reaction was controlled by the steric properties of the aryl groups in 1 rather than their electronic
nature. In the vinylation with (E)-2-phenylethenylboronic acid 5, ligands (3aR,6aR)-1 provided enantiose-
lectivity up to 87% ee and gave high yields of ethenylketones 6 in the presence of 1 (6.6 mol %). The con-
figuration of all ketone products obtained with (3aR,6aR)-1 is (S). Rh-catalyzed reaction of
cyclopentenone 4a and (Z)-propenylboronic acid 7 in the presence of ligands (3aR,6aR)-1 yielded at
50 °C an inseparable mixture of (Z)- and (E)-ketones 8 with (Z)-8 as the major product and both in only
moderate enantiomeric excess.
Received 23 March 2012
Revised 23 April 2012
Accepted 27 April 2012
Available online 2 May 2012
Keywords:
Asymmetric catalysis
Chirality
Diene ligands
Enones
Ó 2012 Elsevier Ltd. All rights reserved.
Vinylboronic acids
Since pioneering studies by Hayashi,1 Carreira,2 and Grützm-
acher,3 chiral diene steering ligands proved to be very useful in
Rh- and Ir-catalyzed reactions.4 A broad variety of bicyclic diene li-
gands have been prepared and were utilized in 1,4-additions of
aryl- and alkenylboronates to electron-poor alkenes,5 1,6-addi-
tions,6 1,2-additions to acylimines or hydrazones,7 [4+2] cycloaddi-
tions,8 aryl cross couplings,9 cyclizations of alkynals,10
cyclopropanations,11 hydrogenation of dehydroamino acids,12 and
polymerizations.13 Also some acyclic dienes were established as li-
gands in Rh-catalyzed asymmetric reactions.14
R1
1 R1
a Ph
H
H
Bn
b
c 4-F-C6H4
d 4-MeO-C6H4
R1
(3aR,6aR)-1
Scheme 1. Diene ligands 1a–d.
For our experiments, a series of substituted tetrahydropenta-
lenes 1 (Scheme 1) were synthesized. Ligands 1a (R1 = Ph) and 1b
(R1 = Bn) have been earlier reported for both configurations,
3aS,6a5p,16,17 and 3aR,6aR.16 In contrast, only 3aS,6aS-isomers for
structures 1c (R1 = p-F-C6H4) and 1d (R1 = p-MeO-C6H4) were de-
scribed in the literature.5n
We focused on the synthesis of the enantiomers (3aR,6aR)-1c
and (3aR,6aR)-1d. For this purpose we chose the well established
cross coupling of organometallic reagents with bis(triflate)
(3aR,6aR)-35p,16,17 (Scheme 2).5n,16 Two different catalysts, Fe(a-
cac)3 and Pd(PPh)3, were tested in order to suppress homo-cou-
pling of the Grignard reagent and to optimize the reaction
conditions. The best results were achieved using Pd(PPh)3
(1.5 mol %) (for experimental details and conditions see Supple-
mentary data).
Bicyclo[3.3.0]octa-2,5-diene steering ligands
1 (Scheme 1),
based on a tetrahydropentalene scaffold,15 have been applied in
asymmetric catalysis by our group16 and, independently, by Xu,
Lin, and co-workers5p,17 These tetrahydropentalene-based ligands
showed high stereoselectivity in Rh-catalyzed arylation of enon-
es,5n,5p,16,17 sulfonylimines,5p,7c,7h,17,18 nitroalkenes,5h as well as in
Pd-mediated aryl–aryl couplings.9
In order to expand the scope of olefinic steering ligands in
asymmetric catalysis, we were interested to study the catalytic
behavior of bicyclo[3.3.0]octa-2,5-diene derivatives 116 in Rh-cata-
lyzed conjugate addition of arylethenyl and alkylethenylboronic
acids to enone substrates. For this purpose, electronic and steric
properties of the substituents R1 (Scheme 1) were varied, and their
influence on stereoselectivity was investigated. The results are dis-
cussed below.
Cyclic b-alkenyl ketones are widely used as building blocks in
organic synthesis.19 In our experiments, the conjugate 1,4-addition
of (E)-2-phenylethenylboronic acid 5 to cyclic enones 4a–c was
investigated in the presence of tetrahydropentalene ligands
⇑
Corresponding author. Tel.: +49 711 685 64565; fax: +49 711 685 64285.
E-mail address: sabine.laschat@oc.uni-stuttgart.de (S. Laschat).
0040-4039/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2012.04.130

S. Helbig et al. / Tetrahedron Letters 53 (2012) 3506–3509
3507
O
R2-C6H4
R2-C6H4MgBr
TfO
H
H
H
H
1) KHMDS
2) 2-PyNTf2
THF
[cat]
THF
O
C6H4-R2
H
H
OTf
(3aR,6aR)-2
(3aR,6aR)-3, 75%
(3aR, 6aR)-1c, R2 = p-F, 72%
(3aR, 6aR)-1d, R2 = p-OMe, 71%
For experimental details see Supporting Information
Scheme 2. Synthesis of diene ligands 1c,d.
Table 2
O
Enantioselective Rh-catalyzed 1,4-addition of (1Z)-prop-1-enylboronic acid
7 to
(HO)2B
(5)
cyclopentenone 4a in the presence of diene ligands (3aR,6aR)-1a,b
Ph
Entry Ligandb Conversion (%)c Product Z:E
% ee (Z)d,e % ee (E)d
O
(see Table 1)
Ph
n
[cat], KOH
(S)-6a-c
1
2
3
4
1a
1b
1c
1d
85
87
83
81
8
8
8
8
77:23
75:25 (82)
69:31
69:31 (60)
—
44
50
34
42
dioxane-H2O
50°C, 2 h
O
O
—
n
(7)
(HO)2B
4a-c
+
a
Reaction conditions according to Scheme 3. For experimental details see Sup-
plementary data and Ref.16
Configuration of the ligands is (3aR,6aR).
Due to volatility of products 8, yields could not be determined.
Enantioselectivity was determined by capillary GC using a chiral stationary
phase.
No baseline separation of enantiomers by GC; therefore the ee-values were
estimated.
(see Table 2)
4,6
a b
c
(Z)-8
(E)-8
b
c
n
0 1 2
d
[cat] = [RhCl(C2H4)2]2 (3.0 mol %),
(3a ,6a )-1a-d (6.6 mol %)
R
R
e
Scheme 3. Rh-catalyzed 1,4-addition of boronic acids 5,7 to cyclic enones 4a–c.
Table 1
Whereas 1,4-arylation of enones received an increased atten-
Enantioselective Rh-catalyzed 1,4-addition of (E)-2-phenylethenylboronic acid 5 to
tion,4a–c,5j,5o,5r,14b,20 studies dedicated to the conjugate addition of
alkyl-5k,5o,20j,21 and arylethenylboronic acids5o,21,22 are scarce. In a
series of experiments, the 1,4-addition of (Z)-prop-1-enylboronic
acid 7 to cyclopentenone 4a was investigated. (Z)-prop-1-enylbo-
ronic acid 7 was reacted with substrate 4a in the presence of
[RhCl(C2H4)2]2 (3 mol %) and ligands (3aR,6aR)-1 (6.6 mol %), Ta-
ble 2. In all cases, an inseparable mixture of 3-[(1Z)-prop-1-
enyl]cyclopentanone (Z)-8 and its (1E)-isomer (E)-8 was obtained
(Scheme 3). In comparison with (E)-2-phenylethenylboronic acid
5, the boronic acid 7 was less reactive, and in the reaction with
cyclopentenone 4a complete conversion of the enone reagent
could not be achieved (Table 2). The Rh-catalyzed Z/E-isomeriza-
tion in 7 seems to occur faster than the addition of 7 to enone
4a,23 which leads to the appearance of the E-isomer (E)-8. Isomer-
ization of the propenyl group and the slow rate of the addition
reaction are possible reasons for low enantioselectivity of the pro-
cess, with enantiomeric excess recorded for (E)-8 between 34% ee
and 50% ee and estimated for (Z)-8 in a range of 60–82% ee.
In Rh-catalyzed addition reactions, mediated by a chiral olefinic
ligand, it is assumed that a chiral olefin-Rh complex is formed.24
These complexes possess molecular C2-symmetry, defined by the
ligand scaffold, which was illustrated by single crystal X-ray stud-
ies of isolated compounds.25 The enone substrate coordinates with
the Rh-center in a manner avoiding steric repulsion between the
carbonyl group of the substrate and bulky substituents of the ole-
finic ligand.5o,26 Intramolecular syn-addition of the aryl group to
the enone in the chiral intermediate complex selectively leads to
one enantiomer.1
enones 4 in the presence of diene ligands (3aR,6aR)-1a,b
Entry
Enone
n
Ligand
Productb
Yieldc (%)
ee (%)
1
2
3
4
5
6
7
8
4a
4a
4a
4a
4b
4b
4b
4b
4c
4c
4c
4c
0
0
0
0
1
1
1
1
2
2
2
2
1a
1b
1c
1d
1a
1b
1c
1d
1a
1b
1c
1d
6a
6a
6a
6a
6b
6b
6b
6b
6c
6c
6c
6c
74
51
72
66
80
63
70
65
86
71
80
76
70
32
67
76
76
48
76
77
87
58
86
85
9
10
11
12
a
b
c
Reaction conditions according to Scheme 3. For experimental details see Sup-
porting Information and Ref..16
Configuration of the ligands is (3aR,6aR). Configuration of ligands and products
was assigned by comparison of optical rotation with the literature data.14b,16,23
Yields refer to isolated yields.
(3aR,6aR)-1 (Scheme 3). Under reaction conditions typical for
arylation,16 for example 1.5 mol % of [RhCl(C2H4)2]2, 3.3 mol % of
ligand 1 and KOH as a base, the reaction of (E)-2-phenylethenylbo-
ronic acid 5 with enones 4a–c did not occur. Upon a two-fold
increase of the catalyst loading, b-alkenylketones 6a–c were
produced with yields up to 86% and enantioselectivities up to
87% ee (Table 1). As compared to the arylated analogues 1a,c,d
(entries 1, 3–5, 7–9, 11, 12), the ligand 1b bearing benzyl
groups was much less efficient, giving lower yields and only
moderate enantiomeric excess up to 58% ee (entries 2, 6, 10).
Concerning the catalytic activity of the ligands 1a–d with different
electronic properties, the following trend was observed
1a > 1c > 1d > 1b regardless of the ring size of enone 4. The struc-
tural influence of the enone substrate on the properties of the
catalyst in the vinylation reaction was significant. An increase in
the ring size of the cyclic enone substrate 4 led to an increase in
both productivity and selectivity of the Rh-catalysts, derived from
ligands 1a–d.
The structures of free Ph-substituted tetrahydropentalene 1a
(3aS,6aS)-isomer16 as well as (3aR,6aR)-isomer5n have been re-
ported in the literature. Upon coordination of (3aS,6aS)-1a with
the Rh-center, a C2-symmetrical structure is formed, with Ph
groups placed in opposite lateral sectors of the ligand core.5n By
an analogy with earlier made assumptions (see above), the inter-
mediate formation of corresponding chiral Rh complexes might
be suggested for tetrahydropentalene-derived ligands (3aR,6aR)-
1a–d. Subsequently, stereoselective coordination of an enone

3508
S. Helbig et al. / Tetrahedron Letters 53 (2012) 3506–3509
substrate on the si-site to the Rh-center should lead to enantiome-
rically pure ketone products (S)-6 (for a mechanistic proposal see
Supplementary data). Flat aryl substituents in (3aR,6aR)-1a,c,d
are presumably most suited to provide smooth coordination of
the enone to the Rh-center. In contrast, the nonplanar benzyl group
in ligand (3aR,6aR)-1b might shield the Rh-center from coordina-
tion with an enone substrate, which could be a reason for the
low catalytic activity and enantioselectivity of the ligand.
References and notes
1. Hayashi, T.; Ueyama, K.; Tokunaga, N.; Yoshida, K. J. Am. Chem. Soc. 2003, 125,
11508–11509.
2. Fischer, C.; Defieber, C.; Suzuki, T.; Carreira, E. M. J. Am. Chem. Soc. 2004, 126,
1628–1629.
3. Maire, P.; Deblon, S.; Breher, F.; Geier, J.; Böhler, C.; Rüegger, H.; Schönberg, H.;
Grützmacher, H. Chem. Eur. J. 2004, 10, 4198–4205.
4. Reviews: (a) Glorius, F. Angew. Chem. 2004, 116, 3444–3446; Angew. Chem. Int.
Ed. 2004, 43, 3364–3366; (b) Johnson, J. B.; Rovis, T. Angew. Chem. 2008, 120,
852–884. Angew. Chem. Int. Ed. 2008, 47, 840–871; (c) Defieber, C.;
Grützmacher, H.; Carreira, E. M. Angew. Chem. 2008, 120, 4558–4579; Angew.
Chem. Int. Ed. 2008, 47, 4482–4502; (d) Feng, C.-C.; Xu, M. H.; Lin, G.-Q. Synlett
2011, 1345–1356; (e) Shintani, R.; Hayashi, T. Aldrichimica Acta 2009, 42, 31–
38.
5. (a) Shao, C.; Yu, H.-J.; Wu, N.-Y.; Tian, P.; Wang, R.; Feng, C.-G.; Lin, G.-Q. Org.
Lett. 2011, 13, 788–791; (b) Nishimura, T.; Kasai, A.; Nagaosa, M.; Hayashi, T.
Chem. Commun. 2011, 10488–10490; (c) Wei, W. T.; Yeh, J.-Y.; Kuo, T.-S.; Wu,
H.-L. Chem. Eur. J. 2011, 17, 11405–11409; (d) Saxena, A.; Lam, H. W. Chem. Sci.
2011, 2, 2326–2331; (e) Li, Q.; Dong, Z.; Yu, Z.-X. Org. Lett. 2011, 13, 1122–
1125; (f) Shintani, R.; Hayashi, T. Org. Lett. 2011, 13, 350–352; (g) Pattison, G.;
Piraux, G.; Lam, H. W. J. Am. Chem. Soc. 2010, 132, 14373–14375; (h) Wang, Z.-
Q.; Feng, C.-G.; Zhang, S.-S.; Xu, M.-H.; Lin, G.-Q. Angew. Chem. 2010, 122, 5916–
5919; Angew. Chem. Int. Ed. 2010, 49, 5780-5783; (i) Luo, Y.; Carnell, A. J. Angew.
Chem. 2010, 122, 2810–2814; Angew. Chem. Int. Ed. 2010, 49, 2750-2754; (j)
Gendrineau, T.; Genet, J.-P.; Darses, S. Org. Lett. 2010, 12, 308–310; (k) Frost, C.
G.; Edwards, H. J.; Penrose, S. D.; Gleave, R. Synthesis 2010, 3243–3247; (l)
Shintani, R.; Tsutsumi, Y.; Nagaosa, M.; Nishimura, T.; Hayashi, T. J. Am. Chem.
Soc. 2009, 131, 13588–13589; (m) Gendrineau, T.; Chuzel, O.; Eijsberg, H.;
Genet, J.-P.; Darses, S. Angew. Chem. 2008, 120, 7783–7786; Angew. Chem. Int.
Ed. 2008, 47, 7669-7672; (n) Feng, C.-G.; Zhi-Qieu, T.; Tian, P.; Xu, M.-H.; Lin,
G.-Q. Chem. Asian J. 2008, 3, 1511–1516; (o) Okamoto, K.; Hayashi, T.; Rawal, V.
H. Org. Lett. 2008, 10, 4387–4389; (p) Feng, C.-G.; Wang, Z.-Q.; Shao, C.; Xu, M.-
H.; Liu, G.-Q. Org. Lett. 2008, 10, 4101–4104; (q) Sörgel, S.; Tokunaga, N.; Sasaki,
K.; Okamoto, K.; Hayashi, T. Org. Lett. 2008, 10, 589–592; (r) Berthon-Gelloz, G.;
Hayashi, T. J. Org. Chem. 2006, 71, 8957–8960.
Considering the size of the molecule and distribution of electron
density, (Z)-prop-1-enylboronic acid
7 differs markedly from
2-phenylvinyl analogue 5. The presence of the electron-donating
Me-substituent seems to slow down the rate of reaction between
boronic acid 7 and cyclopentenone 4a (see above). In the same
time, due to the small size of the propenyl moiety, the rate of
Z/E-isomerization in the (Z)-prop-1-enyl group coordinated to the
Rh-center is not affected by the bulky substituents of the chiral ole-
finic ligand. Consequently, appearance of the E-oriented ketone
products could be expected in this situation, with a Z/E ratio con-
trolled by the steric size of the boronic acid and almost indepen-
dent from the bulkiness of the olefinic ligand. This was observed
in our experiments. The reactions with rather bulky (E)-phen-
ylethenylboronic acid 5 showed no sign of E/Z-isomerization. In
the Rh-catalyzed addition of (Z)-propenylboronic acid 7 to cyclo-
pentenone 4a, mixtures of Z/E-products (Z)-8 and (E)-8 have been
obtained in the presence of ligands 1a–d (Table 2). The use of dif-
ferent substituted ligands 1a–1d, led to only a small change in the
content of E-isomer (between 23% and 31%).
In conclusion tetrahydropentalene-derived Rh catalysts showed
high catalytic activity and stereoselectivity for 1,4-conjugate
addition of (E)-2-phenylethenylboronic acid 5 to cyclic enone sub-
strates 4a–c. Several factors affect the selectivity and productivity
of the process. The electronic nature of aryl substituents in the li-
gand framework has only little influence on the stereocontrol of
the addition reaction. Conversely, steric factors have a considerable
effect on enantiomeric purity and yield of the reaction. The ligand
with nonplanar benzyl substituents was less efficient and selective
than tetrahydropentalenes bearing planar aryl groups. Enantiose-
lectivity and productivity of the Rh-catalyst are also dependent
on the ring size of the cyclic substrate. The enantioselectivity also
depends considerably on the nature of the used boronic acid. (E)-2-
phenylethenylboronic acid 5 gave substituted ketones with quite
high enantiomeric purity and yields. In contrast, the addition of
(Z)-prop-1-enyl boronic acid 7 occurred with reduced enantiose-
lectivity and was accompanied by Z/E-isomerization of the prop-
1-enyl group. Based on the obtained knowledge, directed synthesis
of b-substituted ketones could be performed with required selec-
tivity by gentle tuning in the structure of the ligand, substrate, or
used organoboronic acid. This should expand the applicability of
the Rh-catalyzed 1,4-conjugate addition to the synthesis of chiral
complex organic molecules.
6. (a) Nishimura, T.; Noishiki, A.; Hayashi, T. Chem. Commun. 2012, 973–975; b)
Nishimura, T.; Yasuhara, Y.; Sawano, T.; Hayashi, T. J. Am. Chem. Soc. 2010, 132,
7872–7873.
7. (a) Shintani, R.; Takeda, M.; Soh, Y.-T.; Ito, T.; Hayashi, T. Org. Lett. 2011, 13,
2977–2979; (b) Cui, Z.; Yu, H.-J.; Yang, R.-F.; Gao, W.-Y.; Feng, C.-G.; Lin, G.-Q. J.
Am. Chem. Soc. 2011, 133, 12394–12397; (c) Yang, H.-Y.; Xu, M.-H. Chem.
Commun. 2010, 46, 9223–9225; (d) Shintani, R.; Takeda, M.; Tsuji, T.; Hayashi,
T. J. Am. Chem. Soc. 2010, 132, 13168–13169; (e) Shintani, R.; Soh, Y.-T.;
Hayashi, T. Org. Lett. 2010, 12, 4106–4109; (f) Shao, C.; Yu, H.-J.; Wu, N.-Y.;
Feng, C.-G.; Lin, G.-Q. Org. Lett. 2010, 12, 3820–3823; (g) Okamoto, K.; Hayashi,
T.; Rawal, V. H. Chem. Commun. 2009, 4815–4817; (h) Wang, L.; Wang, Z.-Q.;
Xu, M.-H.; Lin, G.-Q. Synthesis 2010, 3263–3267.
8. Shintani, R.; Sannoha, Y.; Tsuji, T.; Hayashi, T. Angew. Chem. 2007, 119, 7415–
7418; Angew. Chem. Int. Ed. 2007, 46, 7277-7280.
9. Zhang, S.-S.; Wang, Z.-Q.; Xu, M.-H.; Lin, G.-Q. Org. Lett. 2010, 12, 5546–5549.
10. Shintani, R.; Okamoto, K.; Otomaru, Y.; Ueyama, K.; Hayashi, T. J. Am. Chem. Soc.
2005, 127, 54–55.
11. (a) Nishimura, T.; Maeda, Y.; Hayashi, T. Org. Lett. 2011, 13, 3674–3677; (b)
Nishimura, T.; Kawamoto, T.; Nagarosa, M.; Kumamoto, H.; Hayashi, T. Angew.
Chem. 2010, 122, 1682–1685; Angew. Chem. Int. Ed. 2010, 49, 1638-1641.
12. (a) Punniyamurthy, T.; Mayr, M.; Dorofeev, A. S.; Bataille, C. J. R.; Gosiewska, S.;
Nguyen, B.; Cowly, A. R.; Brown, J. M. Chem. Commun. 2008, 5092–5094; (b)
Aikawa, K.; Takahayashi, Y.; Kawauchi, S.; Mikami, K. Chem. Commun. 2008,
5095–5097.
13. (a) Ichikawa, Y.; Nishimura, T.; Hayashi, T. Organometallics 2011, 30, 2342–
2348; (b) Nishimura, T.; Ichikawa, Y.; Hayashi, T.; Onishi, N.; Shiotsuki, M.;
Masuda, T. Organometallics 2009, 28, 4890–4893.
14. (a) Trost, B. M.; Burns, A. C.; Tautz, T. Org. Lett. 2011, 13, 4566–4569; (b) Hu, X.;
Zhuang, M.; Cao, Z.; Du, H. Org. Lett. 2009, 11, 4744–4747.
15. (a) Wawzonek, S. J. Am. Chem. Soc. 1943, 65, 839–843; (b) Quast, H.; Carlsen, J.;
Herkert, T.; Janiak, R.; Röschert, H.; Peters, E.-M.; Peters, K.; von Schnering, H.
G. Liebigs Ann. Chem. 1992, 495–511.
Acknowledgments
16. Helbig, S.; Sauer, S.; Cramer, N.; Laschat, S.; Baro, A.; Frey, W. Adv. Synth. Catal.
2007, 349, 2331–2337.
17. Wang, Z.-Q.; Feng, C.-G.; Xu, M.-H.; Lin, G.-Q. J. Am. Chem. Soc. 2007, 129, 5336–
5337.
18. Trinkado, M.; Ellman, J. A. Angew. Chem. 2008, 120, 5705–5708; Angew. Chem.
Int. Ed. 2008, 47, 5623-5626.
19. The use of enantiomerically pure 3-(2-phenylvinyl)cyclohexanone in total
synthesis of phoslactomycin A, see König, C. M.; Gebhardt, B.; Schleth, C.;
Dauber, M.; Koert, U. Org. Lett. 2009, 11, 2728–2731.
Generous financial support by the Deutsche Forschungsgeme-
inschaft (DFG), the Fonds der Chemischen Industrie, the
Ministerium für Wissenschaft, Forschung und Kunst des Landes
Baden-Württem berg is gratefully acknowledged. We would like
to thank Umicore, Hanau for donation of Rh-precursors. We are
grateful to Inga Loke and Tanja Heidt for skillful technical assistance.
20. (a) Hafner, C.; Alexakis, A. Chem. Commun. 2010, 46, 7295–7306; (b) Shintani,
R.; Duan, W.-L.; Nagano, T.; Okada, A.; Hayashi, T. Angew. Chem. 2005, 117,
4687–4690; Angew. Chem. Int. Ed. 2005, 44, 4611-4614; (c) Kina, A.; Ueyama,
K.; Hayashi, T. Org. Lett. 2005, 7, 5889–5892; (d) Hahn, B. T.; Tewes, F.; Fröhlich,
R.; Glorius, F. Angew. Chem. 2010, 122, 1161–1164; Angew. Chem. Int. Ed. 2010,
49, 1143-1146; (e) Shintani, R.; Ueyama, K.; Yamada, I.; Hayashi, T. Org. Lett.
2004, 6, 3425–3427; (f) Defieber, C.; Paquin, J.-F.; Serna, S.; Carreira, E. M. Org.
Lett. 2004, 6, 3873–3876; (g) Chen, F.-X.; Kina, A.; Hayashi, T. Org. Lett. 2006, 8,
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.tetlet. 2012.04.
130.

S. Helbig et al. / Tetrahedron Letters 53 (2012) 3506–3509
3509
341–344; (h) Tokunaga, N.; Hayashi, T. Adv. Synth. Catal. 2007, 349, 513–516;
(i) Zoute, L.; Kociok-Köhn, G.; Frost, C. G. Org. Lett. 2009, 11, 2491–2494; (j)
Gendrineau, T.; Genet, J.-P.; Darses, S. Org. Lett. 2009, 11, 3486–3489.
21. Shintani, R.; Ichikawa, Y.; Takatsu, K.; Chen, F.-X.; Hayashi, T. J. Org. Chem. 2009,
74, 869–873.
22. (a) Chen, G.; Gui, J.; Li, L.; Liao, J. Angew. Chem. 2011, 123, 7823–7827; Angew.
Chem. Int. Ed. 2011, 50, 7681-7685; (b) Thaler, T.; Guo, L.-N.; Steib, A. K.;
Raducan, M.; Karaghiosoff, K.; Mayer, P.; Knochel, P. Org. Lett. 2011, 13, 3182–
3185; (c) Wang, Y.-Z.; Hu, X.-C.; Du, H.-F. Org. Lett. 2010, 12, 5482–5485; (d)
Konno, T.; Tanaka, T.; Miyabe, T.; Morigaki, A.; Ishihara, T. Tetrahedron Lett.
2008, 49, 2106–2110; (e) Zigterman, J. L.; Woo, J. C. S.; Walker, S. D.; Tedrow, J.
S.; Borths, C. J.; Bunel, E. E.; Faul, M. M. J. Org. Chem. 2007, 72, 8870–8876; (f)
Stemmler, R. T.; Bolm, C. J. Org. Chem. 2005, 70, 9925–9931.
23. Examples of Rh-catalyzed E/Z-isomerizations of substituted alkenes: (a)
Podlaha, J.; Prochazka, M. Collect. Czech. Chem. Commun. 1985, 50, 1274–
1282; (b) Mori, A.; Takahisa, E.; Nishihara, Y.; Hiyama, T. Can. J. Chem. 2001, 79,
1522–1524; (c) Musolino, M. G.; Apa, G.; Donato, A.; Pietropaolo, R. Catal.
Today 2005, 100, 467–471; (d) Martan, M.; Reichenbacher, P. H. Isomerization
of cis-anethole to trans-anethole, US 4038325 A, July 26, 1977.
24. Hayashi, T.; Takahashi, M.; Takaya, Y.; Ogasawara, M. J. Am. Chem. Soc. 2002,
124, 5052–5058.
25. Otomaru, Y.; Kina, A.; Shintani, R.; Hayashi, T. Tetrahedron: Asymmetry 2005,
16, 1673–1679. For crystal structures of isolated Rh-complexes also see Refs.
5r,20f
.
26. Otomaru, Y.; Okamoto, K.; Shintani, R.; Hayashi, T. J. Org. Chem. 2005, 70, 2503–
2508.