Asymmetric Synthesis of Triarylmethanes by Rhodium-Catalyzed Enantioselective Arylation of Diarylmethylamines with Arylboroxines

Article abstract of DOI:10.1021/jacs.5b03277

The reaction of racemic diarylmethylamines, (Ar¹Ar²CHNR₂), where Ar¹ is substituted with a 2-hydroxy group, with arylboroxines (Ar³BO)₃ in the presence of a chiral diene-rhodium catalyst gave high yields of chiral triarylmethanes (Ar¹Ar²CH?Ar³) with high enantioselectivity (up to 97% ee). The reaction is assumed to proceed through o-quinone methide intermediates which undergo Rh-catalyzed asymmetric 1,4-addition of the arylboron reagents.

Full text of DOI:10.1021/jacs.5b03277

Communication
pubs.acs.org/JACS
Asymmetric Synthesis of Triarylmethanes by Rhodium-Catalyzed
Enantioselective Arylation of Diarylmethylamines with Arylboroxines
Yinhua Huang† and Tamio Hayashi*,†,‡
†Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
‡Institute of Materials Research and Engineering, A*STAR, 3 Research Link, Singapore 117602, Singapore
S
* Supporting Information
Scheme 1. Synthesis of Enantiomerically Enriched
Triarylmethanes
ABSTRACT: The reaction of racemic diarylmethyl-
amines, (Ar1Ar2CHNR2), where Ar1 is substituted with a
2-hydroxy group, with arylboroxines (Ar3BO)3 in the
presence of a chiral diene-rhodium catalyst gave high yields
of chiral triarylmethanes (Ar1Ar2CH*Ar3) with high
enantioselectivity (up to 97% ee). The reaction is assumed
to proceed through o-quinone methide intermediates
which undergo Rh-catalyzed asymmetric 1,4-addition of
the arylboron reagents.
riarylmethanes (Ar1Ar2Ar3CH) are known to be an
T
important class of compounds because of their high utility
in medicinal chemistry and materials science as well as in organic
synthesis.1 The enantiomerically enriched triarylmethanes have
been synthesized by a few methods including asymmetric
catalysis, which are summarized in Scheme 1. They are: (a)
stereospecific Ni- or Pd-catalyzed cross-coupling of enantiomeri-
cally enriched diarylmethyl esters2,3 or boron reagents;4 (b)
enantioposition-selective oxidative cross-coupling of 2-
(diarylmethyl)pyridine catalyzed by a chiral Pd catalyst;5 and
(c) asymmetric Friedel−Crafts alkylation of electron-rich arenes
catalyzed by a chiral phosphoric acid.6 Here we report a new type
of asymmetric synthesis of triarylmethanes which is realized by
Rh-catalyzed enantioselective substitution of diarylmethylamines
with arylboron reagents (Scheme 1d).
On the other hand, it has been well recognized that the
rhodium-catalyzed asymmetric arylation of olefins with arylbor-
on reagents is one of the most convenient and reliable methods
of creating benzylic stereocenters with high enantioselectivity.7
The olefinic substrates successfully applied for the asymmetric
arylation are mainly electron-deficient olefins, typically those
activated by carbonyl groups such as α,β-unsaturated ketones.8
We envisioned that o-quinone methide,9 which is classified as an
α,β-unsaturated ketone, could be an appropriate substrate for the
catalytic asymmetric synthesis of chiral triarylmethanes.
same conditions gave a lower yield (61%) of triarylmethane 3aa
with 79% ee (entry 2). These results demonstrate that the
quinone methide can be an appropriate substrate for the
rhodium-catalyzed asymmetric arylation forming chiral triaryl-
methanes, but the low availability of isolable quinone methides is
a serious drawback in studying the present asymmetric reactions.
Based on the report by Schaus that the ethyl ether 5a is a good
precursor to generate quinone methide in situ for their
asymmetric addition of boronates catalyzed by a chiral
binaphthol,13,14 we examined 5a for the rhodium-catalyzed
asymmetric arylation. It turned out that the yield of triaryl-
methane is low under the basic conditions with both cod and
binap-rhodium catalysts, cyclic boronate 4a being the major
At initiating our studies, the reaction of isolated quinone
methide 1a, which is obtained according to a reported
procedure,10 was examined for its reactivity under some of the
standard conditions used for α,β-unsaturated ketones.7 Thus, 1a
was allowed to react with phenylboroxine (2a) in the presence of
[RhCl(cod)]2 (5 mol % of Rh) and KOH (40 mol %) in dioxane/
H2O (10/1) at 40 °C.11 All the quinone methide 1a was
consumed within 15 h to give 82% yield of triarylmethane 3aa
together with 18% of a cyclic phenylboronate 4a (entry 1 in
Received: March 30, 2015
12
Table 1). Use of [RhCl((R)-binap)]2 as a catalyst under the
© XXXX American Chemical Society
A
DOI: 10.1021/jacs.5b03277
J. Am. Chem. Soc. XXXX, XXX, XXX−XXX

Journal of the American Chemical Society
Communication
was subjected to the rhodium-catalyzed arylation. Although the
conversion of 6a is not high in the dioxane/H2O mixed solvent,
the triarylmethane 3aa was formed in 22% and 15% yields with
the Rh-cod and Rh-binap catalysts, respectively (entries 6 and 7).
Screening of the reaction solvents revealed that the reaction in
dioxane without H2O greatly improves the yield of triaryl-
methane. Thus, the yields of 3aa were increased to 81% and 55%
with the Rh-cod and Rh-binap catalysts, respectively (entries 8
and 9). Of the chiral diene ligands18 examined (entries 10−12),
Fc-tfb19 showed the highest performance in terms of both
catalytic activity and enantioselectivity to give 85% yield of
triarylmethane 3aa with 95% ee (entry 10).20 With segphos21 as a
chiral ligand, the enantioselectivity was higher (96% ee), but the
yield was lower (56%) (entry 13). Dioxane is a solvent of choice
for the present reaction, the yield of 3aa being lower in THF,
toluene, and dichloroethane (entries 14−16). The reaction of
morpholino-substituted diarylmethylamine 6a′ with the Rh/Fc-
tfb catalyst in dioxane gave 3aa with essentially the same
enantioselectivity (94% ee) as 6a, although the yield is slightly
lower (entry 17).
NMR experiments showed that the addition of morpholine to
6a in CDCl3 brings about a rapid equilibration (t1/2 < 1 h at 20
°C) with 6a′ and piperidine (see Supporting Information).
Although o-quinone methide 1a is not detected by NMR, it is
likely that the equilibration proceeds through elimination−
addition via the o-quinone methide intermediate, and the present
Rh-catalyzed substitution of diarylmethylamine with arylborox-
ine also proceeds through the addition of an arylrhodium
intermediate22 to the o-quinone methide.
Several diarylmethylamines 6, where one of the two aryl
groups is 2-hydroxy-4,5-methylenedioxyphenyl, were subjected
to the reaction with a variety of arylboroxines 2 under the
conditions optimized for the reaction of diarylmethylamine 6a
with phenylboroxine (2a) (entry 10 in Table 1). The results
summarized in Table 2 show that the enantioselectivity is
generally high for most of the aryl groups in both diarylmethyl-
amines 6 and arylboroxines 2 with some exceptions (entries 5, 6,
25, 26, and 27). One structural limitation of diarylmethylamine 6
is that the enantioselectivity is low with the ortho-substituted aryl
group (entry 25). The arylation of diarylmethylamine 6b with 4-
methoxy- (2e) and 4-methylphenylboroxine (2b) was found to
take place in the absence of rhodium catalyst to some extent,23
which is in good agreement with the lower % ee observed in the
asymmetric arylation with 2e and 2b (entries 5 and 6). The
enantioselectivity was modest for the addition of 3-thienyl- and
3-furylboronic acids (entries 26 and 27).
Table 1. Rhodium-Catalyzed Asymmetric Arylation of
Quinone Methide 1a and Its Precursors 5a and 6a with
Phenylboroxine (2a)
d
ligand on
Rh
yield
yield
% ee
b
c
c
entry subst
solvent
(%) 3aa (%) 4a
3aa
e
1
2
1a
1a
5a
5a
4a
6a
6a
6a
6a
6a
cod
dioxane/H2O
dioxane/H2O
dioxane/H2O
dioxane/H2O
dioxane/H2O
dioxane/H2O
dioxane/H2O
dioxane
82
61
18
16
0
18
39
82
84
100
18

79

51


76

72
95
f
(S)-binap
e
3
cod
f
4
(S)-binap
e
5
cod
e
g
g
g
6
cod
22
15
81
f
f
7
(S)-binap
12
e
8
cod
12
g
9
(S)-binap
dioxane
55 (55)
87 (85)
26
10
(R,R)-Fc-
tfb
dioxane
13
h
11
12
13
14
15
16
17
6a
6a
6a
6a
6a
6a
(S,S)-Ph-
dioxane
dioxane
dioxane
THF
78 (72)
78 (76)
59 (56)
70 (66)
64 (62)
59 (57)
79 (78)
16
17
23
13
22
15
21
81
64
96
94
92
92
94
i
bod
(S,S)-Ph-
i
tfb
(S)-
segphos
j
(R,R)-Fc-
h
tfb
(R,R)-Fc-
toluene
h
tfb
(R,R)-Fc-
dichloroethane
dioxane
h
tfb
6a′ (R,R)-Fc-
h
tfb
a
Reaction conditions: 1a, 5a, or 6a (0.12 mmol), (PhBO)3 (2a) (0.12
mmol (0.36 mmol of B)), Rh catalyst (5 mol % of Rh), and KOH
b
The absolute configuration of the product 3bh (Ar1 = Ph, Ar2
= 4-BrC6H4) was determined to be (S) by its X-ray crystallo-
graphic analysis.24 The S configuration obtained with (R,R)-Fc-
tfb is rationalized by the addition of aryl−rhodium intermediate
to the quinone methide from its si face. The coordination with
the other face is less favorable due to the steric repulsions
between the carbonyl of quinone methide and one of the
ferrocenyl groups on the diene ligand25 (Scheme 2). All the
products under the present conditions with (R,R)-Fc-tfb ligand
are assumed to have the same configuration.
To generate the o-quinone methide intermediate efficiently
under the present conditions, an electron-donating substituent
on the 2-hydroxyphenyl group is necessary. Replacement of 4,5-
methylenedioxy in 6a by methyl made the diarylmethylamine 7a
much less reactive, and the yield of the triarylmethane product
8ai is low even at higher temperature (70 °C) for a longer
reaction time (Scheme 3). With MeO substitution, 7b is more
(0.048 mmol). Solvent: dioxane/H2O (1.0/0.1 mL), dioxane, THF,
c
1
toluene, dichloroethane (1.0 mL). The yields are obtained by H
NMR analysis of the crude reaction mixture. Isolated yields in
d
parentheses. The % ee was determined by HPLC on a chiral
e
f
g
stationary phase column. [RhCl(cod)]2. [RhCl((R)-binap)]2. 6a
was recovered in 60%, 73%, 7%, and 19% in entries 6, 7, 8, and 9,
h
i
respectively. [RhCl((R,R)-Fc-tfb)]2. [RhCl(coe)2]2/(S,S)-Ph-bod.
j
[RhCl(coe)2]2/(S)-segphos.
product (entries 3−4). It is noted that cyclic boronate 4a is too
stable to generate the quinone methide under the reaction
conditions15 (entry 5).
Our attention was turned to diarylmethylamines as precursors
of quinone methide,9 which are readily prepared from phenol
derivatives, aromatic aldehydes, and secondary amines,16 and are
isolated pure without difficulty due to their high stability
compared with the diarylmethyl ether analogs such as 5a. The
diarylmethylamine 6a,17 where the amino group is piperidino,
B
DOI: 10.1021/jacs.5b03277
J. Am. Chem. Soc. XXXX, XXX, XXX−XXX

Journal of the American Chemical Society
Communication
Table 2. Rhodium-Catalyzed Asymmetric Arylation of
Diarylmethylamines 6 with Arylboroxines 2
Scheme 3. Rhodium-Catalyzed Asymmetric Arylation of
Diarylmethylamines 7 with Arylboroxines 2
a
b
c
entry
4: Ar1
2: Ar2
3: yield (%) ee (%)
1
2
3
4
5
6
6a: 4-MeOC6H4
6a: 4-MeOC6H4
6a: 4-MeOC6H4
6a: 4-MeOC6H4
6b: Ph
2a: Ph
3aa: 85
3ab: 91
3ac: 80
3ad: 82
3be: 94
3bb: 85
3bc: 99
3bf: 84
3bg: 82
3bd: 83
3bh: 71
3bi: 82
3bj: 65
3bk: 53
3ca: 85
3da: 85
3ea: 87
3fa: 86
3ga: 82
3ha: 81
3ia: 78
3ja: 90
3ja: 88
3ka: 59
3la: 74
3al: 77
3am: 35
95
90
96
95
59
84
95
90
90
95
95
97
95
96
90
96
93
94
91
94
91
94
94
90
62
50
67
2b: 4-MeC6H4
2c: 3-MeOC6H4
2d: 4-ClC6H4
2e: 4-MeOC6H4
2b: 4-MeC6H4
2c: 3-MeOC6H4
2f: 3-MeC6H4
2g: 4-FC6H4
2d: 4-ClC6H4
2h: 4-BrC6H4
2i: 4-CF3C6H4
2j: 4-MeOCOC6H4
2k: 4-NO2C6H4
2a: Ph
6b: Ph
d
7
6b: Ph
8
6b: Ph
9
6b: Ph
10
11
12
13
14
15
16
17
18
19
20
21
22
6b: Ph
6b: Ph
6b: Ph
6b: Ph
6b: Ph
6c: 4-MeC6H4
6d: 4-Me2NC6H4
6e: 4-FC6H4
6f: 4-ClC6H4
6g: 4-BrC6H4
6h: 4-CF3C6H4
6i: 4-NO2C6H4
6j: 2-naphthyl
6j: 2-naphthyl
6k: 2-thienyl
6l: 2-MeC6H4
6a: 4-MeOC6H4
6a: 4-MeOC6H4
The hydroxyl group in the triarylmethane products can be
readily removed by palladium-catalyzed reduction of triflate26,27
in a high yield. One example is shown in eq 1, where 3bc was
2a: Ph
2a: Ph
2a: Ph
2a: Ph
2a: Ph
2a: Ph
2a: Ph
e
,f
23
24
25
26
27
2a: Ph
2a: Ph
2a: Ph
f
f
g
2l: 3-thienyl
g
2m: 3-furyl
a
Reaction conditions: diarylmethylamine 6 (0.12 mmol), arylboroxine
2 (0.36 mmol of B), [RhCl((R,R)-Fc-tfb)]2 (5 mol % of Rh), KOH
b
(0.048 mmol), dioxane (1.0 mL) at 40 °C for 15 h. Isolated yield.
c
The % ee was determined by HPLC on a chiral stationary phase
d
e
column. Boroxine 2c (0.72 mmol of B). Reaction of 6j (2.0 mmol)
f
with 3 mol % of the catalyst for 40 h. With [RhCl((S,S)-Fc-tfb)]2.
g
The boronic acid (0.72 mmol) was used.
Scheme 2. Proposed Stereochemical Pathway for the
Asymmetric Arylation of a Quinone Methide Generated from
6 with 2 Catalyzed by Rh/(R,R)-Fc-tfb
reduced into 9 without serious loss of enantiomeric purity.
Conversion of dimethylamino group in 8c was also successful via
trimethylammonium generated by treatment with MeOTf (eq
2). Methylation of the amino group and phenol oxygen in 8cc
followed by reductive removal of the ammonium28 gave chiral
trianisylmethane 10a, where the three methoxy groups are
located at ortho, meta, and para positions, respectively. The
amino group was replaced by an alkenyl group by the palladium-
catalyzed Grignard cross-coupling reaction29 giving 11. During
these transformations, no racemization was observed.
In summary, we have developed a new type of catalytic
asymmetric synthesis of chiral triarylmethanes, which is realized
by a rhodium-catalyzed asymmetric substitution of diarylmethyl-
amines with arylboron reagents. The reaction is assumed to
proceed through o-quinone methide intermediates generated
from diarylmethylamines. The enantioselectivity is generally high
(≥90% ee) with the rhodium catalyst coordinated with a chiral
diene ligand (Fc-tfb).
reactive than 7a, but it is still necessary to heat the reaction.
Under optimized conditions (at 60 °C for 24 h) 7b gave a high
yield of the triarylmethanes 8ba and 8bi albeit with lower
enantioselectivity. Dimethylamino group can activate the
diarylmethylamines 7c,e,f,g,h to make their reactivity compara-
ble with the methylenedioxy group. The reaction with boroxines
2 gave the corresponding triarylmethanes 8 with the
enantioselectivity as high as for methylenedioxy substrates 6.
C
DOI: 10.1021/jacs.5b03277
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Journal of the American Chemical Society
Communication
(14) Recent examples of the use of o-quinone methides for asymmetric
catalysis (a) Selenski, C.; Pettus, T. R. R. J. Org. Chem. 2004, 69, 9196.
(b) Zhang, Y.; Sigman, M. S. J. Am. Chem. Soc. 2007, 129, 3076.
(c) Alden-Danforth, E.; Scerba, M. T.; Lectka, T. Org. Lett. 2008, 10,
4951. (d) Lv, H.; You, L.; Ye, S. Adv. Synth. Catal. 2009, 351, 2822.
(e) Lv, H.; Jia, W.-Q.; Sun, L.-H.; Ye, S. Angew. Chem., Int. Ed. 2013, 52,
8607. (f) El-Sepelgy, O.; Haseloff, S.; Alamsetti, S. K.; Schneider, C.
Angew. Chem., Int. Ed. 2014, 53, 7923. (g) Saha, S.; Schneider, C.
Chem.Eur. J. 2015, 21, 2348. (h) Hsiao, C.-C.; Raja, S.; Liao, H.-H.;
Atodiresei, I.; Rueping, M. Angew. Chem., Int. Ed. 2015, 54, 5762.
(i) Zhao, J.-J.; Sun, S.-B.; He, S.-H.; Wu, Q.; Shi, F. Angew. Chem., Int. Ed.
2015, 54, 5460.
(15) Cyclic boronates as precursors of o-quinone methides, see
(a) Chambers, J. D.; Crawford, J.; Williams, H. W. R.; Dufresne, C.;
Scheigetz, J.; Bernstein, M. A.; Lau, C. K. Can. J. Chem. 1992, 70, 1717.
(b) Lau, C. K.; Mintz, M.; Bernstein, M. A.; Dufresne, C. Tetrahedron
Lett. 1993, 34, 5527. (c) Bissada, S.; Lau, C. K.; Bernstein, M. A.;
Dufresne, C. Tetrahedron Lett. 1994, 35, 3691.
ASSOCIATED CONTENT
■
S
* Supporting Information
Experimental procedures, compound characterization data, and
crystallographic data (CIF). The Supporting Information is
available free of charge on the ACS Publications website at DOI:
10.1021/jacs.5b03277.
AUTHOR INFORMATION
■
Corresponding Author
*tamioh@imre.a-star.edu.sg, chmtamh@nus.edu.sg
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank Institute of Materials Research and Engineering
(IMRE) and National University of Singapore for supporting this
research.
(16) For a review, see Cardellicchio, C.; Capozzi, M. A. M.; Naso, F.
Tetrahedron: Asymmetry 2010, 21, 507.
(17) (a) Jurd, L. J. Heterocyclic Chem. 1985, 22, 993. (b) Lavecchia, A.;
Giovanni, C. D.; Cerchia, C.; Russo, A.; Russo, G.; Novellino, E. J. Med.
Chem. 2013, 56, 2861. (c) von Strandtmann, M.; Cohen, M. P.; Shavel,
J., Jr. Tetrahedron Lett. 1965, 6, 3103.
REFERENCES
■
(1) For pertinent reviews, see (a) Mondal, S.; Panda, G. RSC Adv.
2014, 4, 28317. (b) Nair, V.; Thomas, S.; Mathew, S. C.; Abhilash, K. G.
Tetrahedron 2006, 62, 6731. For selected papers, see (c) Parai, M. K.;
Panda, G.; Chaturvedi, V.; Manju, Y. K.; Sinha, S. Bioorg. Med. Chem.
Lett. 2008, 18, 289. (d) Gibson, H. W.; Lee, S.-H.; Engen, P. T.;
Lecavalier, P.; Sze, J.; Shen, Y. X.; Bheda, M. J. Org. Chem. 1993, 58,
3748. (e) Finocchiaro, P.; Gust, D.; Mislow, K. J. Am. Chem. Soc. 1974,
96, 3198.
(2) (a) Taylor, B. L. H.; Harris, M. R.; Jarvo, E. R. Angew. Chem., Int. Ed.
2012, 51, 7790. (b) Harris, M. R.; Hanna, L. E.; Greene, M. A.; Moore,
C. E.; Jarvo, E. R. J. Am. Chem. Soc. 2013, 135, 3303.
(3) Zhou, Q.; Srinivas, H. D.; Dasgupta, S.; Watson, M. P. J. Am. Chem.
Soc. 2013, 135, 3307.
(4) Matthew, S. C.; Glasspoole, B. W.; Eisenberger, P.; Crudden, C. M.
J. Am. Chem. Soc. 2014, 136, 5828.
(5) Shi, B.-F.; Maugel, N.; Zhang, Y.-H.; Yu, J.-Q. Angew. Chem., Int. Ed.
2008, 47, 4882.
(6) (a) Sun, F.-L.; Zheng, X.-J.; Gu, Q.; He, Q.-L.; You, S.-L. Eur. J. Org.
Chem. 2010, 47. See also (b) Zhuo, M.-H.; Jiang, Y.-J.; Fan, Y.-S.; Gao,
Y.; Liu, S.; Zhang, S. Org. Lett. 2014, 16, 1096.
(7) For pertinent reviews, see (a) Tian, P.; Dong, H.-Q.; Lin, G.-Q.
ACS Catal. 2012, 2, 95. (b) Partyka, D. V. Chem. Rev. 2011, 111, 1529.
(c) Berthon, G.; Hayashi, T. In Catalytic Asymmetric Conjugate Reactions;
(18) For reviews on chiral diene ligands, see (a) Defieber, C.;
Grutzmacher, H.; Carreira, E. M. Angew. Chem., Int. Ed. 2008, 47, 4482.
̈
(b) Shintani, R.; Hayashi, T. Aldrichimica Acta 2009, 42, 31. (c) Feng,
C.-G.; Xu, M.-H.; Lin, G.-Q. Synlett 2011, 1345. (d) Feng, X.; Du, H.
Asian J. Org. Chem. 2012, 1, 204.
(19) (a) Nishimura, T.; Kumamoto, H.; Nagaosa, M.; Hayashi, T.
Chem. Commun. 2009, 5713. (b) Nishimura, T.; Noishiki, A.; Ebe, Y.;
Hayashi, T. Angew. Chem., Int. Ed. 2013, 52, 1777. (c) Nishimura, T.;
Ashouri, A.; Ebe, Y.; Maeda, Y.; Hayashi, T. Tetrahedron: Asymmetry
2012, 23, 655. (d) Sasaki, K.; Hayashi, T. Tetrahedron Asymmetry 2012,
23, 373. (e) Lim, K. M.-H.; Hayashi, T. J. Am. Chem. Soc. 2015, 137,
3201 and references cited.
(20) The yield of the phenylation product 3aa was lower (47%) with a
smaller amount (0.06 mmol (0.18 mmol of B)) of (PhBO)3. The
reaction of 6a with PhB(OH)2 and PhBF3K in place of (PhBO)3 under
the same conditions for entry 10 in Table 1 gave 3aa, in 78% yield (95%
ee) and in <3% yield, respectively.
(21) Saito, T.; Yokozawa, T.; Ishizaki, T.; Moroi, T.; Sayo, N.; Miura,
T.; Kumobayashi, H. Adv. Synth. Catal. 2001, 343, 264.
(22) For the catalytic cycle of Rh-catalyzed 1,4-addition of organo-
boronic acids, see ref 12.
(23) In the absence of rhodium catalyst, the reactions in entries 5 and 6
under otherwise same conditions gave the arylation products in 58%
(3be) and 5% (3bb) yields, respectively. The rhodium-catalyzed
reaction at 23 °C gave 3be with 72% ee albeit in a low yield (40%).
(24) The details are described in Supporting Information.
(25) The rationalization of stereochemical pathway using this type of
model has been always successful (ref 18b). See also Hayashi, T.;
Ueyama, K.; Tokunaga, N.; Yoshida, K. J. Am. Chem. Soc. 2003, 125,
11508.
́
Cordova, A., Ed.; Wiley-VCH: Weinheim, Germany, 2010; Chapter 1, p
1. (d) Edwards, H. J.; Hargrave, J. D.; Penrose, S. D.; Frost, C. G. Chem.
Soc. Rev. 2010, 39, 2093. (e) Johnson, J. B.; Rovis, T. Angew. Chem., Int.
Ed. 2008, 47, 840. (f) Darses, S.; Genet, J.-P. Eur. J. Org. Chem. 2003,
4313. (g) Hayashi, T.; Yamasaki, K. Chem. Rev. 2003, 103, 2829.
(h) Fagnou, K.; Lautens, M. Chem. Rev. 2003, 103, 169. (i) Bolm, C.;
Hildebrand, J. P.; Muniz, K.; Hermanns, N. Angew. Chem., Int. Ed. 2001,
̃
40, 3284.
(26) Wang, Z.; Ai, F.; Wang, Z.; Zhao, W.; Zhu, G.; Lin, Z.; Sun, J. J.
Am. Chem. Soc. 2015, 137, 383.
(8) Early examples of addition to α,β-unsaturated ketones (a) Sakai,
M.; Hayashi, H.; Miyaura, N. Organometallics 1997, 16, 4229.
(b) Takaya, Y.; Ogasawara, M.; Hayashi, T.; Sakai, M.; Miyaura, N. J.
Am. Chem. Soc. 1998, 120, 5579.
(9) Reviews on o-quinone methides (a) Van De Water, R. W.; Pettus,
T. R. R. Tetrahedron 2002, 58, 5367. (b) Amouri, H.; Bras, J. L. Acc.
Chem. Res. 2002, 35, 501. (c) Pathak, T. P.; Sigman, M. S. J. Org. Chem.
2011, 76, 9210. (d) Willis, N. J.; Bray, C. D. Chem.Eur. J. 2012, 18,
9160. (e) Bai, W.-J.; David, J. G.; Feng, Z.-G.; Weaver, M. G.; Wu, K.-L.;
Pettus, T. R. R. Acc. Chem. Res. 2014, 47, 3655.
(27) For reviews on the conversion of aryl triflates, see (a) Ritter, K.
Synthesis 1993, 735. (b) Doucet, H. Eur. J. Org. Chem. 2008, 2013.
(c) Corbet, J.-P.; Mignani, G. Chem. Rev. 2006, 106, 2651.
(28) For Pd-catalyzed reduction of aryl halides, see (a) Rajagopal, S.;
Spatola, A. F. J. Org. Chem. 1995, 60, 1347. (b) Cellier, P. P.; Spindler, J.-
F.; Taillefer, M.; Cristau, H.-J. Tetrahedron Lett. 2003, 44, 7191.
(c) Arcadi, A.; Cerichelli, G.; Chiarini, M.; Vico, R.; Zorzan, D. Eur. J.
Org. Chem. 2004, 3404.
(29) For cross-coupling of ArNMe3OTf, see (a) Reeves, J. T.;
Fandrick, D. R.; Tan, Z.; Song, J. J.; Lee, H.; Yee, N. K.; Senanayake, C.
H. Org. Lett. 2010, 12, 4388. (b) Guo, W.-J.; Wang, Z.-X. Tetrahedron
2013, 69, 9580.
(10) Jurd, L. Tetrahedron 1977, 33, 163.
(11) Itooka, R.; Iguchi, Y.; Miyaura, N. J. Org. Chem. 2003, 68, 6000.
(12) Hayashi, T.; Takahashi, M.; Takaya, Y.; Ogasawara, M. J. Am.
Chem. Soc. 2002, 124, 5052.
(13) Luan, Y.; Schaus, S. E. J. Am. Chem. Soc. 2012, 134, 19965.
D
DOI: 10.1021/jacs.5b03277
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