Asymmetric dearomatization of naphthols via a Rh-catalyzed C(sp2)-H functionalization/annulation reaction

Article abstract of DOI:10.1021/jacs.5b01707

A Rh-catalyzed enantioselective dearomatization of 1-aryl-2-naphthols with internal alkynes via C-H functionalization reaction was achieved. In the presence of a chiral Cp/Rh catalyst and combined oxidants of Cu(OAc)₂ and air (oxygen), various

Full text of DOI:10.1021/jacs.5b01707

Subscriber access provided by UNIV OF NEBRASKA - LINCOLN
Communication
Asymmetric Dearomatization of Naphthols via a Rh-
Catalyzed C(sp2)–H Functionalization/Annulation Reaction
Jun Zheng, Shao-Bo Wang, Chao Zheng, and Shu-Li You
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.5b01707 • Publication Date (Web): 08 Apr 2015
Downloaded from http://pubs.acs.org on April 9, 2015
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a free service to the research community to expedite the
dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts
appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been
fully peer reviewed, but should not be considered the official version of record. They are accessible to all
readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered
to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published
in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just
Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor
changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers
and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors
or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
Journal of the American Chemical Society is published by the American Chemical
Society. 1155 Sixteenth Street N.W., Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 5
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
Asymmetric Dearomatization of Naphthols via a Rh-Catalyzed
C(sp2)–H Functionalization/Annulation Reaction
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Jun Zheng, Shao-Bo Wang, Chao Zheng, and Shu-Li You*
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences,
345 Lingling Lu, Shanghai 200032, China
Supporting Information Placeholder
dearomatization reaction of β-naphthols with alkynes initiated
with C–H functionalization by chiral Rh catalyst (Figure1, eq.
4).10
ABSTRACT: A Rh-catalyzed enantioselective dearomatization
of 1-aryl-2-naphthols with internal alkynes via C–H functionaliza-
tion reaction was achieved. In the presence of a chiral Cp/Rh cata-
lyst and combined oxidants of Cu(OAc)2 and air (oxygen), vari-
ous highly enantioenriched spirocyclic enones bearing an all-
carbon quaternary stereogenic center could be synthesized in 33-
98% yields with up to 97:3 er.
Phenol and naphthol derivatives are among the most abundant
chemical feedstocks in industry and serve as versatile building
blocks for the synthesis of complex target molecules.1 In contrast
to the traditional transformations of phenols and naphthols based
on aromatic substitutions, which generally lead to planar aromatic
products, the catalytic asymmetric dearomatization reactions of
phenols and naphthols have attracted considerable attention and
emerged as novel enabling methods for rapid construction of
highly functionalized three dimensional structures, which signifi-
cantly increased the chemical diversity.2 Although great efforts
have been devoted to the development in this area, yet most
dearomatization reactions of phenols and naphthols still rely on
the transformation of certain functional groups which inevitably
require additional steps for pre-functionalization.3 To the best of
our knowledge, catalytic asymmetric dearomatization reaction
initiated with direct functionalization of inert C–H bonds has not
appeared.4
In 2013, Luan and coworkers5 reported the first Ru-catalyzed
C-H functionalization/vinylative dearomatization of naphthols for
the synthesis of various spirocyclic molecules in good yields and
excellent regioselectivity (Figure 1, eq. 1). and
Gulías,6a as well as Lam6b independently developed Rh-catalyzed
annulative dearomatization of ortho-vinyl phenols triggered by
terminal C–H functionalization of the alkenyl moiety (Figure 1,
eq. 2). More recently, the Luan group7 described a Pd-catalyzed [2
+ 2 + 1] spiroannulation reaction between β-naphthols and two
equivalents of alkynes (Figure 1, eq. 3). Despite these elegant
advances, the reports on transition-metal-catalyzed annulative
dearomatization of phenols and naphthols initiated with C–H
functionalization step are still limited within racemic reactions.
Figure 1. C–H bond functionalization/dearomatization reactions.
The study was launched by utilizing 3-bromo-1-
phenylnaphthalen-2-ol (1a) and prop-1-ynylbenzene (2a) as the
model substrates to optimize the reaction conditions (Table 1). In
the presence of 5 mol % of chiral Rh complex K1 and (BzO)2,
and
3 equivalents of Cu(OAc)2, the C–H functionaliza-
tion/annulation reaction could proceed to provide 3aa in 45%
NMR yield and 92:8 er (entry 1). Interestingly, similar results
were obtained when the reaction was conducted under air (entry
2). Lowering the reaction temperature to 85 °C led to an increase
of yield and enantioselectivity (entry 3), and 1 equivalent of
Cu(OAc)2 was found to be sufficient (entry 4). Varying the sol-
vents showed great influence on the reactivity of the reaction, but
less impact on the enantioselective control (entries 6-9). Toluene
was found to be optimal solvent affording 3aa in 93% yield, 95:5
er and 17:1 regioselectivity (entry 7). Further examination of dif-
ferent chiral Cp/Rh complexes and reaction temperature did not
provide better results (entries 10-13). The yield of the reaction
was decreased dramatically in the absence of Cu(OAc)2 (entry 14).
No reaction occurred without the addition of Rh catalyst. Finally,
the optimal reaction conditions were identified as the following: 5
mol % of K1, 5 mol % of (BzO)2, 1 equivalent of Cu(OAc)2 and 2
equivalents of K2CO3 at 85 °C in toluene under air (entry 7). The
absolute configuration of product 3aa was assigned as S by an X-
In 2014, we reported an asymmetric C–H functionaliza-
tion/dehydrogenative Heck coupling between biaryl compounds
and alkenes to synthesize axially chiral products.8 The chiral Rh
catalysts developed by the Cramer group were found capable of
inducing good enantioselective control under relatively harsh
conditions required for the C–H bond functionalization step.9
Herein, we wish to describe the first asymmetric annulative
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 2 of 5
ray crystallographic analysis (for details, see the Supporting In-
metrical alkynes bearing ethyl and cyclopropyl groups (2b and 2c)
1
2
3
4
5
6
7
8
formation).
both led to their corresponding dearomatized products in excellent
enantioselectivity (96:4-97:3 er), moderate to good yields (74-
88%) and good regioselectivity (7.1:1-14.5:1). Symmetrical al-
kynes bearing various aromatic groups in spite of electronic prop-
erty were tolerated well, and the corresponding spirocyclic prod-
ucts (3bd-3bi) were obtained in moderate to good yields (54-86%)
with excellent enantioselectivity (96:4-97:3 er). Satisfactorily, a
gram-scale reaction between 1b and 2d proceeded smoothly with-
out affecting the reaction outcome. Notably, dialkylacetylene (2j)
could undergo this transformation leading to 3bj in excellent yield
(98%) and good enantioselective control (92:8 er).
Table 1. Optimization of the reaction conditions.a
9
entry
1d
2e
3
4
5
x
3
3
3
1
0.5
1
1
1
1
solvent
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
DME
toluene
DCE
t-AmylOH
toluene
toluene
yield (%)b
45
49
74
80 (72)
70
29
93 (81)
19
21
47
31
88
80
19
erc
Cat.
K1
K1
K1
K1
K1
K1
K1
K1
K1
K2
K3
K4
K1
K1
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
92:8
92:8
95:5
95:5
94:6
92:8
95:5
92:8
87:13
88:12
88:12
69:31
95:5
89:11
Scheme 2. Substrate scope: alkynes.a
6
7f
8
9
10
11
12
13g
14
1
1
1
1
toluene
toluene
toluene
0
a
Reaction conditions: 1a (0.1 mmol), 2a (0.2 mmol), Cat. (5 mol %),
(BzO)2 (5 mol %), K2CO3 (2 equiv.) and Cu(OAc)2 in solvent at 85 °C for 36 h
under air (open flask), unless otherwise noted. b Determined by 1H NMR analy-
sis with CH2Br2 as an internal standard. Isolated yields are reported in paren-
theses. c Determined by HPLC analysis. d Reflux under Ar. e At 110 C. f Regi-
oselectivity was determined as 17:1. g At 70 C for 58 h.
With the optimized reaction conditions in hands, we next inves-
tigated the substrate scope of the reaction. The effects of various
substituents on the 3-position of naphthols were first evaluated
(Scheme 1). The reactions worked well with naphthols bearing Cl
and F atoms, affording 3ba (83% yield, >19:1 rr, 96:4 er) and 3ca
(72% yield, 10.3:1 rr, 86:14 er), respectively. However, when a
methyl group was introduced (1d) or simple naphthol (1e) was
used, the reactions proceeded in good regio- and enantioselectivi-
ty but moderate yields.
a
Reaction conditions: 1b (0.2 mmol), 2 (0.4 mmol), K1 (5 mol %), (BzO)2
(5 mol %), K2CO3 (2 equiv.) and Cu(OAc)2 (1 equiv.) in toluene at 85 °C under
air (open flask). Regioselectivity (rr) was determined by 1H NMR analysis of
the crude reaction mixture. Yields of isolated products are reported. Er was
determined by HPLC analysis. b 3.2 mmol 1b and 6.4 mmol 2d were used.
Scheme 3. Substrate scope: substituted β-naphthols.a
Scheme 1. Substrate scope: 3-substituted β-naphthols.a
a
Reaction conditions: 1 (0.2 mmol), 2a (0.4 mmol), K1 (5 mol %), (BzO)2
(5 mol %), K2CO3 (2 equiv.) and Cu(OAc)2 (1 equiv.) in toluene at 85 °C under
air (open flask). Regioselectivity (rr) was determined by 1H NMR analysis of
the crude reaction mixture. Yields of isolated products are reported. Er was
determined by HPLC analysis.
a
Reaction conditions: 1 (0.2 mmol), 2d (0.4 mmol), K1 (5 mol %), (BzO)2
Next, various alkynes (2b-2j) were examined in the reaction
with 3-chloro-1-phenylnaphthalen-2-ol (1b) (Scheme 2). Unsym-
(5 mol %), K2CO3 (2 equiv.) and Cu(OAc)2 (1 equiv.) in toluene at 85 °C under
air (open flask). Yields of isolated products are reported. Er was determined by
HPLC analysis.
ACS Paragon Plus Environment

Page 3 of 5
Journal of the American Chemical Society
In addition, various substituted 1-aryl-2-naphthol derivatives
1
2
3
4
5
6
7
8
(1f-1q) were examined with diphenylacetylene (2d) as the cou-
pling partner (Scheme 3). Either electron-donating or electron-
withdrawing group (Me, Ph, OMe, F and CO2Me) at the para-
position of phenyl ring (1f-1j) was well tolerated, and the desired
products were obtained in good yields (72-86%) and enantioselec-
tivity (90:10-94:6 er). While substrate 1k bearing 3-methyl phenyl
led to the desired product in 81% yield, substrate 1m bearing 2-
trifluoromethyl phenyl only gave 33% yield. In both cases, good
enantiomeric ratio was obtained (3kd, 3md, 93:7 er). To be noted,
because of the secondary directing effect of methoxyl group,9d
substrate 1l containing 3-methoxyl phenyl substituent gave 8:1
regioselectivity with excellent enantioselectivity (96:4 and 97:3 er)
for both regioisomers. To our delight, the introduction of varied
substituents (Ph, Me, CHO) on the 6-position of naphthalene ring
(1n, 1o, 1p) were tolerated well affording products in good yields
and excellent enantiomeric ratios. The compatibility of the formyl
group further enhanced potentials of the diverse transformation of
the product. The reaction involving heterocycle substrate contain-
ing a thienyl ring (1q) could also provide the expected product
(3qd) with excellent enantiomeric ratio (95:5 er), albeit in low
yield.
Scheme 5. Deuteration Experiments.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Scheme 6. Proposed mechanism.
To demonstrate the synthetic utility of the method, several
transformations of the 2-naphthalenone products were carried out
(Scheme 4). The ketone group in 3bd could be reduced with
LiAlH4 to afford allylic alcohol 5bd in excellent yield and dia-
stereoselectivity (eq. 5). The Suzuki–Miyaura coupling between
bromo-containing product 3aa and PhB(OH)2 gave 5aa in quanti-
tative yield (eq. 6).
Scheme 4. Transformations of the products.
In summary, we have achieved the first asymmetric C–H func-
tionalization/dearomatization reaction of -naphthol derivatives
by a chiral rhodium catalyst. The reaction allows the transfor-
mation of simple naphthol derivatives into chiral spirocyclic -
naphthalenones bearing an all-carbon quaternary stereogenic cen-
ter in good to excellent yields, regio- and enantioselectivity.
To shed light on the mechanism of the Rh-catalyzed asymmet-
ric annulative dearomatization reaction, deuterium-labeling exper-
iments were performed (Scheme 5). The intramolecular competi-
tive experiment of monodeuterated analogue 1b-d1 with prop-1-
ynylbenzene (2a) under standard conditions resulted in no H/D
scrambling in the recovered starting material, which suggested
that the C–H bond cleavage step is irreversible. A kinetic isotope
effect (kH/kD~3.8) was observed at different reaction stages (eq. 7).
In addition, the kinetic isotope effect (kH/kD~5.7) was also ob-
served in an intermolecular competitive experiment (eq. 8). These
observations indicate that C–H bond cleavage is most likely in-
volved in the rate-limiting step.
ASSOCIATED CONTENT
Supporting Information
Text, figures, and CIF files giving experimental procedures, com-
pound characterization data. This material is available free of
charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
E-mail: slyou@sioc.ac.cn.
Based on the above mechanistic information and previous re-
ports,5,6 a putative mechanism for the reaction is proposed
(Scheme 6). The catalytic cycle likely begins with the deprotona-
tion of the -naphthol substrates by the Rh catalyst. The obtained
intermediate I subsequently undergoes C–H bond activation, lead-
ing to the rhodacycle II. Alkyne coordination and migratory inser-
tion gives a rather strained eight-membered rhodacycle III which
might be in equilibrium with a six-membered isomer IV. Finally,
the dearomatized product is obtained after reductive elimination,
and the released Rh(I) species is concomitantly oxidized by
Cu(OAc)2 and oxygen to the activated Rh(III) catalyst, furnishing
the catalytic cycle.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
We thank the National Basic Research Program of China (973
Program 2015CB856600) and the National Natural Science Foun-
dation of China (21121062, and 21332009) for generous financial
support. We are also in greatly indebted to Prof. Tian-Sheng Mei
and Prof. Guosheng Liu for their helpful discussions. This paper
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 4 of 5
is dedicated to Prof. Xue-Long Hou on the occasion of his 60th
birthday.
masaki, M.; Shiro, M.; Fujioka, H.; Maruyama, A.; Kita, Y. J. Am.
Chem. Soc. 2013, 135, 4558. (n) Phipps, R. J.; Toste, F. D. J. Am.
Chem. Soc. 2013, 135, 1268. (o) Wang, S.-G.; Yin, Q.; Zhuo, C.-
X.; You, S.-L. Angew. Chem., Int. Ed. 2015, 54, 647. (p) Yang,
D.-X.; Wang, L.-Q; Han, F.-X.; Li, D.; Zhao, D.-P.; Wang, R.
Angew. Chem., Int. Ed. 2015, 54, 2185. (q) Nan, J.; Liu, J.; Zheng,
H.; Zuo, Z.; Hou, L.; Hu, H.; Wang, Y.; Luan, X. Angew. Chem.,
Int. Ed. 2015, 54, 2356. (r) Du, K.; Guo, P.; Chen, Y.; Cao, Z.;
Wang, Z.; Tang, W. Angew. Chem., Int. Ed. 2015, 54, 3033.
(4) For reviews on asymmetric C–H functionalization reactions, see:
(a) Giri, R.; Shi, B.-F.; Engle, K. M.; Maugel, N.; Yu, J.-Q. Chem.
Soc. Rev. 2009, 38, 3242. (b) Yang, L.; Huang, H. Catal. Sci.
Technol. 2012, 2, 1099. (c) Wencel-Delord, J.; Colobert, F.
Chem.-Eur. J. 2013, 19, 14010. (d) Zheng, C.; You, S.-L. RSC
Adv. 2014, 4, 6173.
(5) (a) Nan, J.; Zuo, Z.; Luo, L.; Bai, L.; Zheng, H.; Yuan, Y.; Liu, J.;
Luan, X.; Wang, Y. J. Am. Chem. Soc. 2013, 135, 17306. (b) For
a racemic synthesis of similar substrates, see: Zheng, H.; Bai, L.;
Liu, J.; Nan, J.; Zuo, Z.; Yang, L.; Wang, Y.; Luan, X. Chem.
Commun. 2015, 51, 3061.
(6) (a) Seoane, A.; Casanova, N.; Quiñones, N.; Mascareñas, J. L.;
Gulías, M. J. Am. Chem. Soc. 2014, 136, 7607. (b) Kujawa, S.;
Best, D.; Burns, D. J.; Lam, H. W. Chem.–Eur. J. 2014, 20, 8599.
(7) Gu, S.; Luo, L.; Liu, J.; Bai, L.; Zheng, H.; Wang, Y.; Luan, X.
Org. Lett. 2014, 16, 6132.
1
2
3
4
5
6
7
8
REFERENCES
(1) (a) Fiege, H.; Voges, H.-W.; Hamamoto, T.; Umemura, S.; Iwata,
T.; Miki, H.; Fujita, Y.; Buysch, H.-J.; Garbe, D.; Paulus, W.
“Phenol derivatives” in Ullmann's Encyclopedia of Industrial
Chemistry; Wiley-VCH; Weinheim, 2000. (b) Weber, M.; Weber,
M.; Kleine-Boym nn . “Phenol” in Ullmann’s Encyclopedia of
Industrial Chemistry; Wiley-VCH; Weinheim, 2004.
(2) For selected reviews on dearomatization reactions, see: (a) Pape,
A. R.; Kaliappan, K. P.; Kündig, E. P. Chem. Rev. 2000, 100,
2917. (b) Pelter, A.; Ward, R. S. Tetrahedron 2001, 57, 273. (c)
Kündig, E. P.; Pape, A. R. Top. Organomet. Chem. 2004, 7, 71.
(d) Harman, W. D. Top. Organomet. Chem. 2004, 7, 95. (e)
Quideau, S.; Pouységu, L.; Deffieux, D. Curr. Org. Chem. 2004,
8, 113. (f) López Ortiz, F.; Iglesias, M. J.; Fernández, I.; Andújar
Sánchez, C. M.; Gómez, G. R. Chem. Rev. 2007, 107, 1580. (g)
Quideau, S.; Pouységu, L.; Deffieux, D. Synlett 2008, 467. (h)
Pouységu, L.; Deffieux, D.; Quideau, S. Tetrahedron 2010, 66,
2235. (i) Roche, S. P.; Porco Jr., J. A. Angew. Chem., Int. Ed.
2011, 50, 4068. (j) Zhuo, C.-X.; Zhang, W.; You, S.-L. Angew.
Chem., Int. Ed. 2012, 51, 12662. (k) Zhuo, C.-X.; Zheng, C.; You,
S.-L. Acc. Chem. Res. 2014, 47, 2558.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(8) Zheng, J.; You, S.-L. Angew. Chem., Int. Ed. 2014, 53, 13244.
(9) For examples on Rh(III)-catalyzed asymmetric C–H functionali-
zation reactions, see: (a) Hyster, T. K.; Knörr, L.; Ward, T. R.;
Rovis, T. Science 2012, 338, 500. (b) Ye, B.; Cramer, N. Science
2012, 338, 504. (c) Ye, B.; Cramer, N. J. Am. Chem. Soc. 2013,
135, 636. (d) Ye, B.; Donets, P. A.; Cramer, N. Angew. Chem.,
Int. Ed. 2014, 53, 507. (e) Ye, B.; Cramer, N. Angew. Chem., Int.
Ed. 2014, 53, 7896. For a chiral Cp/Sc catalyzed asymmetric C–H
functionalization reaction, see: Song, G.; O, W. W. N.; Hou, Z. J.
Am. Chem. Soc. 2014, 136, 12209.
(10) For selected reviews on Rh(III)-catalyzed C–H functionalization
reaction, see: (a) Satoh, T.; Miura, M. Chem.-Eur. J. 2010, 16,
11212. (b) Wencel-Delord, J.; Dröge, T.; Liu, F.; Glorius, F.
Chem. Soc. Rev. 2011, 40, 4740. (c) Yeung, C. S.; Dong, V. M.
Chem. Rev. 2011, 111, 1215. (d) Colby, D. A.; Tsai, A. S.; Berg-
man, R. G.; Ellman, J. A. Acc. Chem. Res. 2012, 45, 814. (e)
Song, G.; Wang, F.; Li, X. Chem. Soc. Rev. 2012, 41, 3651. (f)
Kuhl, N.; Schröder, N.; Glorius, F. Adv. Synth. Catal. 2014, 356,
1443. (g) Zhang, X.-S.; Chen, K.; Shi, Z.-J. Chem. Sci. 2014, 5,
2146.
(3) For selected examples on asymmetric dearomatization reactions
of phenols and naphthols: (a) Dong, S.; Zhu, J.; Porco Jr., J. A. J.
Am. Chem. Soc. 2008, 130, 2738. (b) Dohi, T.; Maruyama, A.;
Takenaga, N.; Senami, K.; Minamitsuji, Y.; Fujioka, H.;
Caemmerer, S. B.; Kita, Y. Angew. Chem., Int. Ed. 2008, 47,
3787. (c) Boppisetti, J. K.; Birman, V. B. Org. Lett. 2009, 11,
1221. (d) Quideau, S.; Lyvinec, G.; Marguerit, M.; Bathany, K.;
Ozanne-Beaudenon, A.; Buffeteau, T.; Cavagnat, D.; Chénedé, A.
Angew. Chem., Int. Ed. 2009, 48, 4605. (e) Qi, J.; Beeler, A. B.;
Zhang, Q.; Porco Jr., J. A. J. Am. Chem. Soc. 2010, 132, 13642. (f)
Uyanik, M.; Yasui, T.; Ishihara, K. Angew. Chem., Int. Ed. 2010,
49, 2175. (g) Nemoto, T.; Ishige, Y.; Yoshida, M.; Kohno, Y.;
Kanematsu, M.; Hamada, Y. Org. Lett. 2010, 12, 5020. (h) Uyan-
ik, M.; Yasui, T.; Ishihara, K. Tetrahedron 2010, 66, 5841. (i) Wu,
Q.-F.; Liu, W.-B.; Zhuo, C.-X.; Rong, Z.-Q.; Ye, K.-Y.; You, S.-
L. Angew. Chem. Int. Ed. 2011, 50, 4455. (j) Rousseaux, S.; Gar-
cía-Fortanet, J.; Del Aguila Sanchez, M. A.; Buchwald, S. L. J.
Am. Chem. Soc. 2011, 133, 9282. (k) Oguma, T.; Katsuki, T. J.
Am. Chem. Soc. 2012, 134, 20017. (l) Yoshida, M.; Nemoto, T.;
Zhao, Z.; Ishige, Y.; Hamada, Y. Tetrahedron: Asymmetry 2012,
23, 859. (m) Dohi, T.; Takenaga, N.; Nakae, T.; Toyoda, Y.; Ya-
ACS Paragon Plus Environment

Page 5 of 5
Journal of the American Chemical Society
1
2
TOC Graphic
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
5
ACS Paragon Plus Environment