Ru-Catalyzed Chemo- and Enantioselective Hydrogenation of β-Diketones Assisted by the Neighboring Heteroatoms

Article abstract of DOI:10.1021/acs.orglett.9b01829

A highly chemo- and enantioselective hydrogenation of β-diketones was achieved by using [Ru(benzene)(S)-SunPhosCl]Cl for consistency in THF. The neighboring heteroatoms played important roles in guaranteeing the reactivity and controlling the chemoselectivity. These results suggested a potential approach for the clean and facile synthesis of functionalized chiral β-hydroxy ketones, which could otherwise be prepared through much less step-economic transformations.

Full text of DOI:10.1021/acs.orglett.9b01829

Letter
pubs.acs.org/OrgLett
Cite This: Org. Lett. XXXX, XXX, XXX−XXX
Ru-Catalyzed Chemo- and Enantioselective Hydrogenation of
β‑Diketones Assisted by the Neighboring Heteroatoms
Wanfang Li,†,‡ Bin Lu,‡ Xiaomin Xie,‡ and Zhaoguo Zhang*,‡,§
†College of Science, University of Shanghai for Science and Technology, Shanghai 200093, China
‡Shanghai Key Laboratory for Molecular Engineering of Chiral Drugs, School of Chemistry and Chemical Engineering, Shanghai
Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
§State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345
Lingling Road, Shanghai 200032, China
S
* Supporting Information
ABSTRACT: A highly chemo- and enantioselective hydrogenation of β-diketones was achieved by using [Ru(benzene)(S)-
SunPhosCl]Cl for consistency in THF. The neighboring heteroatoms played important roles in guaranteeing the reactivity and
controlling the chemoselectivity. These results suggested a potential approach for the clean and facile synthesis of functionalized
chiral β-hydroxy ketones, which could otherwise be prepared through much less step-economic transformations.
nantiopure β-hydroxy ketones represent a prevalent
(Scheme 1c) that used DNA-based catalysts or chiral copper
complexes, respectively.
E
structural motif for numerous natural products and
pharmaceutical agents.1 Therefore, the construction of these
chiral building blocks instigated the interest of many synthetic
chemists. Traditionally, asymmetric Mukaiyama-type aldol
reactions allow for a convenient preparation of chiral β-
hydroxy ketones (Scheme 1a).2 Alternatively, enantiopure β-
Notably, a selective monoreduction of β-diketones is an
appealing alternative to the aforementioned methods seeing
that β-diketone compounds are readily accessible.6 However,
few chemical reductions could discriminate between the two
extremely similar carbonyl groups thereof. Until now,
enzymatic reductions are still the mainstay in producing high
levels of chemo- and enantioselectivity in this regard (Scheme
1d).7 However, they are generally expensive and of low
volume−time output and poor substrate generality, which
made their applications in organic synthesis difficult.
Accordingly, there is a strong growing incentive to develop
some general chemical reductions of β-diketones to chiral β-
hydroxy ketones (Scheme 1e) in a selective manner. For
example, Yamada et al. designed a chiral cobalt complex to
catalyze the selective reduction of 2-substituted β-diketones
with NaBH4.8 For some cyclic β-diketones, Noyori’s transfer
hydrogenation catalyst was able to deliver good yields and
enantioselectivity by using HCOOH/NEt3 as the reductant.9
Undoubtedly, Noyori-type hydrogenation is the most clean
and efficient redution method for various mono- and
unfunctionalized ketones to enantiopure alcohols.10 The
simultaneous chemo- and enantioselective hydrogenation of
polycarbonyls, however, was usually frustrated by the multiple
coordinations between the manifold carbonyl groups and
Scheme 1. Known Routes of Access to Chiral β-Hydroxy
Ketones
hydroxy acid derivatives have been converted to β-hydroxy
ketones through nucleophilic substitutions (Scheme 1b).3 In
2017, Bru
̈
ckner and co-workers3b demonstrated this strategy
by the reaction of Grignard and organolithium reagents with
enantiopure β-hydroxy Weinreb amides. More recently, Zhou
and co-workers obtained a β-hydroxy ketone substructure from
chiral β-hydroxy acid in their formal synthesis of (−)-cyanolide
A.3c Other emerging methods employed the asymmetric
hydration4 or tandem β-borylation/oxidation5 of α,β-enones
Received: May 26, 2019
© XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.9b01829
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
ruthenium center.11 It is well-known that Noyori-type
hydrogenation of β-diketones invariably produces anti-1,3-
diols, whereas the intermediate β-hydroxy ketones can seldom
be isolated with meaningful yields (Scheme 2a).12 Herein, we
communicate our recent work on the chemo- and
enantioselective hydrogenation of various heteroatom-substi-
tuted β-diketones to β-hydroxy ketones (Scheme 2b).
a
Table 1. Optimization of the Reaction Conditions
e
b
c
entry L*
T (°C) H2 (bar) time (h) yield (%)
ee (%)
1
2
3
4
5
6
L1
50
50
70
90
70
70
10
20
20
20
20
20
20
20
15
8
15
15
89
91
99.4 (R)
99.6 (R)
99.3 (R)
99.8 (R)
91.6 (R)
93.7 (S)
L1
L1
L1
L2
L3
93
Scheme 2. Asymmetric Monohydrogenation of β-Diketones
to β-Hydroxy Ketones
d
42
91
92
a
Conditions: 1a (103 mg, 0.5 mmol), THF (2 mL), [Ru(benzene)-
b
c
(L*)Cl]Cl, S/C = 200. Isolated yields. ee’s were determined by
chiral HPLC. The absolute configuration was determined by
comparing the specific rotation with the reported value. The
byproduct was anti-1-(benzyloxy)pentane-2,4-diol. L1 = (S)-
d
e
SunPhos; L2 = (S)-SegPhos; L3 = (R)-BINAP.
EtOH, CH2Cl2, and acetone. Less than 5% conversion of 1a
was observed in MeCN and DMF. 1,4-Dioxane and ethyl
acetate allowed for the hydrogenation of 1a to 2a with 80%
and 19% conversion, respectively. The corresponding isolated
yields, 76% and 17%, respectively, implied a high level of
chemoselectivity. However, the enantioselectivity was de-
creased to 93−94%. We thus set the following optimized
conditions: 70 °C, 20 bar of H2, (S)-SunPhos as the ligand.
Having the optimized conditions in hand, we tried to
broaden the substrate scope to other alkoxyl-substituted β-
In our previous work on the asymmetric hydrogenation of
polyfunctionalized ketones,13 we discovered that hydrogena-
tion of β-hydroxy ketones, unlike the situation in conventional
alcoholic solvents, was extraordinarily sluggish in a coordina-
tive solvent like THF. Enlightened by this observation, we
inferred that selective monohydrogenation of β-diketones to β-
hydroxy ketones might be achieved in THF. To prove this, we
conducted the hydrogenation of symmetric β-diketones such
as 2,4-pentanedione and dibenzoylmethane with a nonchiral
catalyst in THF (Scheme 3a). Nevertheless, almost no
diketones. 1-(Methoxy)pentane-2,4-dione (1b, where R1
=
Me) was hydrogenated under the optimized conditions to give
2b in 83.7% ee (entry 1, Table 2), much lower than that of 2d
Scheme 3. Initial Experiments for the Hydrogenation of β-
Diketones in THF
Table 2. Asymmetric Hydrogenation of 1-Alkoxyl β-
Diketones
a
a
b
c
entry
1
R1
R2
yield (%)
ee (%)
1
2
3
4
5
6
7
8
9
1b
1c
1d
1e
1f
1g
1h
1i
Me
Ph
Bn
Bn
Bn
Bn
Bn
Bn
Bn
Bn
Ph
Me
Ph
4-MeOC6H4
4-CF3C6H4
2-ClC6H4
2-MeC6H4
1-naphthyl
2-naphthyl
2-furyl
95
92
94
91
90
83.7
98.6
99.9 (R)
98.7
97.4
−
95.4
97.8
98.5
95.7
a
Conditions: 20 bar of H2, 90 °C, 8 h.
d
conversion was detected in the presence of [Ru(benzene)-
(SunPhos)Cl]Cl under 20 bar of H2 at 90 °C for 8 h (Scheme
3a). However, 1-(benzyloxy)pentane-2,4-dione (1a), which
featured one adjacent benzyloxy group, was fully converted to
2a in 99.8% ee and 42% yield (Scheme 3b), together with anti-
1-(benzyloxy)pentane-2,4-diol (2aa) in 40% yield (Scheme
3b).
Reaction conditions were then scrutinized to maximize the
monohydrogenation of 1a to β-hydroxy ketone 2a. As shown
in Table 1, the temperature and hydrogen pressure had little
effect on the enantioselectivity. Lower temperatures led to
higher yields of 2a because overhydrogenation to 2aa was
alleviated (entries 1−3, Table 1). For comparison, the
analogous Ru-BINAP and Ru-SegPhos catalysts were prepared
in the same fashion and delivered somewhat lower
enantioselectivities (entries 5 and 6, respectively, Table 1),
which might be caused by the variations in the steric and
electronic properties of the ligands.14 Other solvents were also
examined (see Table S1). Only 1,3-diol (2aa) was obtained in
−
95
92
95
94
1j
1k
10
a
Conditions: 1 (1.0 mmol), THF (2.0 mL), [Ru(benzene)(L*)Cl]Cl,
b
c
S/C = 200, 70 °C, 20 bar of H2, 15 h. Isolated yield. ee’s were
determined by HPLC. The absolute configuration of 2d was
determined by comparing the specific rotation with the reported
d
value. A mixture was obtained even at 45 °C and 20 bar of H2 for 6
h.
where R1 = Bn (entry 3, Table 2). Phenyloxyl acetone 1c was
also hydrogenated well in 98.6% ee (entry 2, Table 2). Various
substituents on the phenyl rings (R2) were tolerated. Overall,
ortho substituents on R2 decreased the enantioselectivity to
various extents. However, the presence of an ortho chloro
substituent led to overhydrogenation of the 3,5-dicarbonyls
(2gg) under the standard conditions, which may be caused by
B
DOI: 10.1021/acs.orglett.9b01829
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
the competitive coordination of the chloro atom (entry 6,
Table 2).15 When R2 = 2-furyl, the corresponding hydro-
genation product 2k was also isolated in high yield and ee
(entry 10, Table 2). These hydrogenation products in Table 2
are useful chiral intermediates that could be prepared only by
some less straightforward methods.16
of 1-(2-chlorophenyl)-3-phenylpropane-1,3-dione (3g) could
be hydrogenated in high chemical yield and good enantiose-
lectivity, in which the chloro atom is crucial (entry 7 of Table 3
vs Scheme 3a). Such diaryl-β-hydroxy ketones were used in
prophylaxis or the treatment of photodermatoese.18 In
addition, 2,4-diketo acid derivatives (4h−j), which remained
elusive substrates as in the previous reports,19 could also be
selectively hydrogenated at the C2-carbonyls in moderate to
high yields and enantioselectivities (entries 8−10, Table 3).
For the 2,4-diketones mentioned above (1 and 3), it is
seemed as if one of the carbonyl groups was “activated” by the
adjacent heteroatoms, which imparted the high level of C2
versus C4 selectivity. To the best of our knowledge, such an
activation phenomenon has not been investigated or even
proposed in asymmetric hydrogenation reactions. Although
chloro and benzyloxy groups were reported to compete in the
coordination to the Ru center,12b,20 the hydrogenation of the
C2-carbonyl of 1a was directed by the C4-carbonyl inferred
from the absolute configuration of 2a (Scheme 4a; see the
Next, β-diketones with other heteroatoms were explored for
the chemo- and enantioselective hydrogenation (Table 3). For
Table 3. Asymmetric Hydrogenation of 1,3-Diketones with
a
Other Heteroatoms
Scheme 4. Determination of the Intrinsic Directing Group
by the Enantio-Induction Outcome
Supporting Information).10a Moreover, benzyloxyacetone
remained inactive under the same reaction conditions, which
also negated the direction by the benzyloxy group (Scheme
4b).
Considering the distinctive keto−enol equilibrium in β-
dicarbonylic systems,21 we proposed a tentative correlation
between the reactivity and the presence of the neighboring
heteroatoms (Scheme 5). For β-diketones without any
Scheme 5. Heteroatoms Affected the Hydrogen Bonding
Orientation
a
Conditions: 3 (1 mmol), THF (2 mL), 70 °C, 20 bar of H2, 15 h, S/
b
c
C = 200. Isolated yield. Determined by HPLC. The absolute
configuration of known compounds was determined by comparing the
d
chiral HPLC elution orders with literature results. With 0.05 mmol
e
of CaCO3 added. At 80 °C and 30 bar of H2.
example, 3a and 3b were hydrogenated to give 4a and 4b,
respectively, in high ee’s while the yields were moderate due to
the lability of dialkoxyl ketals. When 10 mol % CaCO3 was
added, the yield of 4a was improved to 89% while the
enantioselectivity dropped to 91.6%.17 Both γ-phthalimide
acetylacetone (3c) and γ-phenylsulfonyl β-diketones (3d and
3e) were also hydrogenated to C2-hydroxy products with high
chemo- and enantioselectivity (entries 3−5, respectively, Table
3). The substrate with multiple halides (3f) was selectively
hydrogenated at the C2-carbonyl to 4f with 59% ee (entry 6,
Table 3) promoted by the CF3 group. Similarly, the 2-carbonyl
neighboring heteroatoms (A), the cyclic intramolecular O−
H···O hydrogen bond (B and C)22 disfavored easy accessibility
for the catalyst to form valid coordination, so ethyl
acetoacetate and acetylacetone were almost inert toward
hydrogenation in THF or cyclohexane. When a catalytic
amount of H2SO4 or TsOH was added, the cyclic enols, B or
C, were interrupted to form A or their noncyclic enol forms,22b
which favored effective coordination with the ruthenium
center, and smooth hydrogenation was observed (Scheme 5a).
C
DOI: 10.1021/acs.orglett.9b01829
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Organic Letters
Letter
Org. Lett. 2013, 15, 2869−2871. (c) Mase, N.; Hayashi, Y.;
In the presence of neighboring heteroatom X, the
equilibrium may shift from D to E driven by the formation
of the intramolecular O−H···X hydrogen bond.23 For example,
3f was reported to exist mainly in enol form E due to the
strong intramolecular O−H···F hydrogen bonding.24 We
believe that the enol E exposes its electron pairs on the two
oxygens adequately toward the ruthenium catalyst to form
efficacious coordination (F and F′ in Scheme 5b) for the
selective hydrogentaion to take place. As evidence, ethyl 4-
chloroacetoacetate (X = Cl; R1 = OEt) can be hydrogenated in
cyclohexane or THF, while ethyl acetoacetate (X = H; R1 =
OEt) cannot.21b To obtain some structural information for the
enol forms that may contribute to the unprecedented
Heathcock, C.; Kobayashi, S.; Yamashita, Y.; Yoo, W.-J.;
́
Kitanosono, T.; Soule, J.-F.; Harada, T.; Abiko, A. In Comprehensive
Organic Synthesis, 2nd ed.; Knochel, P., Molander, G. A., Eds.;
Elsevier, 2014; Vol. 2, pp 273−511.
(2) (a) Wadamoto, M.; Ozasa, N.; Yanagisawa, A.; Yamamoto, H. J.
Org. Chem. 2003, 68, 5593−5601. (b) Lou, S.; Westbrook, J. A.;
Schaus, S. E. J. Am. Chem. Soc. 2004, 126, 11440−11441.
(c) Kobayashi, S.; Ogino, T.; Shimizu, H.; Ishikawa, S.; Hamada,
T.; Manabe, K. Org. Lett. 2005, 7, 4729−4731. (d) Paradowska, J.;
Pasternak, M.; Gut, B.; Gryzło, B.; Mlynarski, J. J. Org. Chem. 2012,
77, 173−187. (e) Shu, K.; Kodadek, T. ACS Comb. Sci. 2018, 20,
277−281.
̂
(3) (a) Labeeuw, O.; Bourg, J. B.; Phansavath, P.; Genet, J. P.
ckner, R. Eur. J. Org.
1
reactivity, we performed a H−13C HMBC experiment with
Arkivoc 2007, 2007, 94−106. (b) Diehl, J.; Bru
̈
Chem. 2017, 2017, 278−286. (c) Che, W.; Li, Y.-Z.; Liu, J.-C.; Zhu,
S.-F.; Xie, J.-H.; Zhou, Q.-L. Org. Lett. 2019, 21, 2369−2373.
(4) (a) Boersma, A. J.; Coquiere, D.; Geerdink, D.; Rosati, F.;
1a in d8-THF and the enol form on the heteroatom’s side (D
or E) was indeed the predominant form (see the Supporting
Information). However, the detailed hydrogenation mecha-
nism is still unclear.25
̀
Feringa, B. L.; Roelfes, G. Nat. Chem. 2010, 2, 991. (b) Yum, J. H.;
Park, S.; Hiraga, R.; Okamura, I.; Notsu, S.; Sugiyama, H. Org. Biomol.
Chem. 2019, 17, 2548−2553.
In summary, we have developed a practical and general
procedure for the chemo- and enantioselective hydrogenation
of various heteroatom-substituted β-diketones. Our method
enriches the toolbox for the synthesis of various valuable chial
β-hydroxy ketones, which have been prepared only via some
waste- and step-intensive transformations. The role of
activation of the heteroatoms was also proposed on the basis
of the analysis of the hydrogen bond orientation in the relevant
substrates. Further investigations of the assistance of the
heteroatoms and applications of this method in the synthesis of
more functionally versatile alcohols are underway in our group.
(5) (a) Kobayashi, S.; Xu, P.; Endo, T.; Ueno, M.; Kitanosono, T.
Angew. Chem., Int. Ed. 2012, 51, 12763−12766. (b) Thorpe, S. B.;
Calderone, J. A.; Santos, W. L. Org. Lett. 2012, 14, 1918−1921.
(c) Zhu, L.; Kitanosono, T.; Xu, P.; Kobayashi, S. Chem. Commun.
2015, 51, 11685−11688.
(6) (a) Kel’in, A. V. Curr. Org. Chem. 2003, 7, 1691−1711.
(b) Shokova, E. A.; Kim, J. K.; Kovalev, V. V. Russ. J. Org. Chem. 2015,
51, 755−830.
(7) (a) Kalaitzakis, D.; Rozzell, J. D.; Smonou, I.; Kambourakis, S.
Adv. Synth. Catal. 2006, 348, 1958−1969. (b) Ema, T.; Kadoya, T.;
Akihara, K.; Sakai, T. J. Mol. Catal. B: Enzym. 2010, 66, 198−202.
(c) Vitale, P.; Perna, F. M.; Agrimi, G.; Scilimati, A.; Salomone, A.;
Cardellicchio, C.; Capriati, V. Org. Biomol. Chem. 2016, 14, 11438−
11445. (d) Xu, F.; Xu, J.; Hu, Y.; Lin, X.; Wu, Q. RSC Adv. 2016, 6,
76829−76837. (e) Dall’Oglio, F.; Contente, M. L.; Conti, P.;
Molinari, F.; Monfredi, D.; Pinto, A.; Romano, D.; Ubiali, D.;
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.or-
glett.9b01829.
̇
Tamborini, L.; Serra, I. Catal. Commun. 2017, 93, 29−32. (f) Ządło-
Dobrowolska, A.; Schrittwieser, J. H.; Grischek, B.; Koszelewski, D.;
Kroutil, W.; Ostaszewski, R. Tetrahedron: Asymmetry 2017, 28, 797−
802.
Details of experimental procedures, characterization data
for 1−4, NMR spectra for compounds 1−4, and HPLC
charts for racemic and chiral compounds 2 and 4 (PDF)
(8) (a) Ohtsuka, Y.; Koyasu, K.; Ikeno, T.; Yamada, T. Org. Lett.
2001, 3, 2543−2546. (b) Yamada, T.; Nagata, T.; Sugi, K. D.; Yorozu,
K.; Ikeno, T.; Ohtsuka, Y.; Miyazaki, D.; Mukaiyama, T. Chem. - Eur.
J. 2003, 9, 4485−4509.
(9) (a) Wu, Y.; Geng, Z.; Bai, J.; Zhang, Y. Chin. J. Chem. 2011, 29,
1467−1472. (b) Cotman, A. E.; Cahard, D.; Mohar, B. Angew. Chem.,
Int. Ed. 2016, 55, 5294−5298.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: zhaoguo@sjtu.edu.cn.
ORCID
(10) (a) Noyori, R.; Ohkuma, T. Angew. Chem., Int. Ed. 2001, 40,
40−73. (b) Shang, G.; Li, W.; Zhang, X. In Catalytic Asymmetric
Synthesis, 3rd ed.; Ojima, I., Ed.; John Wiley & Sons, Inc.: Hoboken,
NJ, 2010. (c) Ager, D. J.; De Vries, A. H. M.; De Vries, J. G. Chem.
Soc. Rev. 2012, 41, 3340−3380. (d) Xie, J.; Zhou, Q. Huaxue Xuebao
2012, 70, 1427−1438. (e) Seo, C. S. G.; Morris, R. H. Organometallics
2019, 38, 47−65.
Wanfang Li: 0000-0002-2544-1756
Xiaomin Xie: 0000-0002-5798-291X
Zhaoguo Zhang: 0000-0003-3270-6617
Notes
The authors declare no competing financial interest.
(11) Xie, X.; Lu, B.; Li, W.; Zhang, Z. Coord. Chem. Rev. 2018, 355,
39−53.
ACKNOWLEDGMENTS
■
(12) (a) Kawano, H.; Ishii, Y.; Saburi, M.; Uchida, Y. J. Chem. Soc.,
Chem. Commun. 1988, 87−88. (b) Kitamura, M.; Ohkuma, T.; Inoue,
S.; Sayo, N.; Kumobayashi, H.; Akutagawa, S.; Ohta, T.; Takaya, H.;
Noyori, R. J. Am. Chem. Soc. 1988, 110, 629−631. (c) Shao, L.;
Kawano, H.; Saburi, M.; Uchida, Y. Tetrahedron 1993, 49, 1997−
The authors thank the National Natural Science Foundation of
China, the Science and Technology Commission of Shanghai
Municipality, and the Education Commission of Shanghai
Municipality for financial support. The authors are also very
grateful for Mr. Chengyang Li’s generous help in partial NMR
and HPLC experiments.
̂
2010. (d) Blanc, D.; Ratovelomanana-Vidal, V.; Marinetti, A.; Genet,
J. P. Synlett 1999, 1999, 480−482. (e) Blandin, V.; Carpentier, J.-F.;
Mortreux, A. Eur. J. Org. Chem. 1999, 1999, 3421−3427. (f) Blandin,
V.; Carpentier, J.-F.; Mortreux, A. New J. Chem. 2000, 24, 309−312.
(13) (a) Li, W.; Fan, W.; Ma, X.; Tao, X.; Li, X.; Xie, X.; Zhang, Z.
Chem. Commun. 2012, 48, 8976−8978. (b) Li, W.; Xie, X.; Tao, X.;
REFERENCES
■
(1) (a) Evans, D. A.; Hoveyda, A. H. J. Am. Chem. Soc. 1990, 112,
6447−6449. (b) Ueno, M.; Huang, Y.-Y.; Yamano, A.; Kobayashi, S.
D
DOI: 10.1021/acs.orglett.9b01829
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
Ma, X.; Fan, W.; Li, X.; Zhang, Z. RSC Adv. 2012, 2, 3214−3216.
(c) Li, W.; Lu, B.; Zhang, Z. Chem. Rec. 2016, 16, 2506−2520.
(14) (a) Zhang, Z.; Qian, H.; Longmire, J.; Zhang, X. J. Org. Chem.
2000, 65, 6223−6226. (b) Saito, T.; Yokozawa, T.; Ishizaki, T.;
Moroi, T.; Sayo, N.; Miura, T.; Kumobayashi, H. Adv. Synth. Catal.
2001, 343, 264−267.
(15) Kitamura, M.; Tokunaga, M.; Ohkuma, T.; Noyori, R.
Tetrahedron Lett. 1991, 32, 4163−4166.
(16) (a) Chenevert, R.; Thiboutot, S. Can. J. Chem. 1986, 64, 1599−
1601. (b) Evans, D. A.; Kozlowski, M. C.; Murry, J. A.; Burgey, C. S.;
Campos, K. R.; Connell, B. T.; Staples, R. J. J. Am. Chem. Soc. 1999,
121, 669−685. (c) Schetter, B.; Mahrwald, R. Angew. Chem., Int. Ed.
2006, 45, 7506−7525. (d) Li, D. R.; Murugan, A.; Falck, J. R. J. Am.
Chem. Soc. 2008, 130, 46−48.
(17) Fan, W.; Li, W.; Ma, X.; Tao, X.; Li, X.; Yao, Y.; Xie, X.; Zhang,
Z. Chem. Commun. 2012, 48, 4247−4249.
(18) Carola, C.; Heider, L.; Lefort, M.; Driller, H. WO 2017088950
A1, 2017. Chem. Abstract. 2017, 167, 48738.
(19) (a) Blandin, V.; Carpentier, J. F.; Mortreux, A. Tetrahedron:
Asymmetry 1998, 9, 2765−2768. (b) Blandin, V.; Carpentier, J.-F.;
Mortreux, A. Eur. J. Org. Chem. 1999, 1999, 1787−1793.
(20) Kitamura, M.; Ohkuma, T.; Takaya, H.; Noyori, R. Tetrahedron
Lett. 1988, 29, 1555−1556.
(21) (a) Emsley, J.; Freeman, N. J. J. Mol. Struct. 1987, 161, 193−
204. (b) Ferrari, E.; Saladini, M.; Pignedoli, F.; Spagnolo, F.; Benassi,
R. New J. Chem. 2011, 35, 2840−2847. (c) Smith, M. B. March’s
Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 7th
ed.; John Wiley & Sons, Inc.: Hoboken, NJ, 2013.
(22) (a) Mills, S. G.; Beak, P. J. J. Org. Chem. 1985, 50, 1216−1224.
(b) Reichardt, C. In Solvents and Solvent Effects in Organic Chemistry;
Wiley-VCH: Weinheim, Germany, 2003; Chapter 4, pp 106−114.
(23) Katsuyama, I.; Ogawa, S.; Yamaguchi, Y.; Funabiki, K.; Matsui,
M.; Muramatsu, H.; Shibata, K. Synthesis 1997, 1997, 1321−1324.
(24) (a) Park, J. D.; Brown, H. A.; Lacher, J. R. J. Am. Chem. Soc.
1953, 75, 4753−4756. (b) von Arx, M.; Mallat, T.; Baiker, A. Angew.
Chem., Int. Ed. 2001, 40, 2302−2305. (c) Hess, R.; Diezi, S.; Mallat,
T.; Baiker, A. Tetrahedron: Asymmetry 2004, 15, 251−257.
(25) Noyori, R.; Ikeda, T.; Ohkuma, T.; Widhalm, M.; Kitamura,
M.; Takaya, H.; Akutagawa, S.; Sayo, N.; Saito, T.; Taketomi, T.;
Kumobayashi, H. J. Am. Chem. Soc. 1989, 111, 9134−9135.
E
DOI: 10.1021/acs.orglett.9b01829
Org. Lett. XXXX, XXX, XXX−XXX