Palladium-Catalyzed Amination of Aryl Sulfides and Sulfoxides with Azaarylamines of Poor Nucleophilicity

Article abstract of DOI:10.1055/s-0037-1611732

The amination of aryl sulfides and sulfoxides with azaarylamines is investigated using a palladium-N-heterocyclic carbene (NHC) complex. Because azaarylamines are less nucleophilic than anilines, more reactive diaryl sulfides and sulfoxides are found to be suitable coupling partners that liberate better leaving arenethiolate or arenesulfenate anions, instead of aryl methyl sulfides as reported previously.

Full text of DOI:10.1055/s-0037-1611732

SYNTHESIS
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© Georg Thieme Verlag Stuttgart · New York
2019, 51, A–H
special topic
A
en
R. Pratap, H. Yorimitsu
Special Topic
Synthesis
Palladium-Catalyzed Amination of Aryl Sulfides and Sulfoxides
with Azaarylamines of Poor Nucleophilicity
Ramendra Pratapa,b
Hideki Yorimitsu*a
S
H
0
0
0
0-0
0
0
2-0
1
5
3-
1
8
8
8
N
Pd-NHC cat.
KHMDS
Ar
H2N
aza
Ar
a Department of Chemistry, Graduate School of Science, Kyoto University,
Sakyo-ku, Kyoto 606-8502, Japan
yori@kuchem.kyoto-u.ac.jp
b Department of Chemistry, University of Delhi, North Campus, Delhi, 110007,
India
aza
43 examples
36–98% yield
poor nucleophilicity
Published as part of the Special Topic Amination Reactions in Organic Synthesis
Received: 22.12.2018
Accepted after revision: 18.01.2019
Published online: 26.02.2019
2-aminopyridine, 2-aminopyrimidine and adenine have
not been well investigated as substrates. Herein, we report
several sets of conditions that realize the amination of aryl
sulfides and sulfoxides with azaarylamines of poor nucleo-
philicity (Figure 1).
DOI: 10.1055/s-0037-1611732; Art ID: ss-2018-z0862-st
Abstract The amination of aryl sulfides and sulfoxides with azaaryl-
amines is investigated using a palladium-N-heterocyclic carbene (NHC)
complex. Because azaarylamines are less nucleophilic than anilines,
more reactive diaryl sulfides and sulfoxides are found to be suitable
coupling partners that liberate better leaving arenethiolate or arene-
sulfenate anions, instead of aryl methyl sulfides as reported previously.
H2N
OMe H2N
N
OMe
H2N
H2N
N
N
N
N
N
N
OMe
OMe
2a
2b
2c
2d
Key words amination, palladium, cross-coupling, organosulfur com-
pounds
H2N
N
H2N
H2N
H2N
N
N
N
N
N
N
NR
Palladium-catalyzed amination of aryl halides rep-
resents a powerful tool to provide a variety of aniline deriv-
atives that are useful as biologically active agents or that are
photophysically or electrochemically intriguing materials.1
Usually, reactive aryl halides and pseudohalides are used as
the substrates. Over the last decade, significant efforts have
been made to achieve amination of rather inert C–O bonds
with nickel catalysts in order to widen the scope of catalytic
amination.2–7
2e
2f
2g
2h R = CH2Ph
2i R = iPr
iPr
iPr
iPr
iPr
N
N
N
N
iPr
iPr
O
iPr
iPr
Pd
Cl
Pd
N
Cl
NH
SingaCycle-A1
SingaCycle-A3
Along this line, aryl sulfides and their derivatives are ex-
pected to be alternative aryl electrophiles in transition-
metal-catalyzed coupling reactions.8,9 While C–S bonds
show intriguing and exquisite reactivity compared with C–X
and C–O bonds, the catalyst-poisoning nature of organosul-
fur species makes it difficult to achieve catalytic transfor-
mations of C–S bonds, especially in their transmetalation
steps where sulfur anions depart from the metal centers.
We have been developing catalytic transformations of C–S
bonds of aryl sulfide derivatives by overcoming the cata-
lyst-poisoning nature.8e,g,9 Indeed, we have achieved palla-
dium-catalyzed aminations of aryl sulfides and sulfox-
ides.9e,h,10 While anilines and alkylamines have been avail-
able for amination, less nucleophilic azaarylamines such as
Figure 1 Structures of the azaarylamines and precatalysts employed in
this work
Previously, we reported one example of the amination
of thioanisole (1a) with 2-aminopyridine (2a), which af-
forded 3aa in 75% yield in the presence of KHMDS (2.5
equiv) and SingaCycle-A311 (5 mol%) (see Figure 1) in diox-
ane/toluene at 100 °C.10a After further screening of the reac-
tion conditions, we found that the use of a larger amount of
KHMDS (3.0 equiv) and a different precatalyst, SingaCycle-
A111 (7.5 mol%) (see Figure 1), improved the yield of 3aa up
to 95% (Table 1). Other aryl sulfides 1b–f participated in the
amination to furnish products 3ba–fa in good yields.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2019, 51, A–H

B
R. Pratap, H. Yorimitsu
Special Topic
Synthesis
Table 1 Reactions of Aryl Methyl Sulfides with 2-Aminopyridine (2a)
Table 2 Reactions of Diaryl Sulfides and Diaryl Sulfoxides with Azaaryl-
amines of Low Nucleophilicity
7.5 mol% SingaCycle-A1
H
3 equiv KHMDS
SMe
N
5 mol% SingaCycle-A1
3 equiv KHMDS
1.3 equiv 2-aminopyridine (2a)
Ar
Ar
H
N
Ar2S (4)
or
Ar2SO (5)
toluene, 100 °C, 18–24 h
1.2 equiv aza-Ar-NH2
2
N
1
3aa–fa
Ar
aza-Ar
toluene, 100 °C, 24 h
3
Entry
Ar
Ph
1
3
Yield (%)
Entry
Substrate 4 or 5
2
3
Yield (%)
1
2
3
4
5
6
1a
3aa
3ba
3ca
3da
3ea
3fa
95
88
72
63
92
94
1
2
Ph2S (4a)
2b
2b
2b
2b
2b
2b
2b
2b
2c
2c
2d
2d
2d
2e
2e
2e
2e
2a
2a
2a
2a
2f
3ab
3ab
3bb
3db
3eb
3gb
3gb
3hb
3ac
3ac
3ad
3ad
3gd
3ae
3ae
3ge
3he
3aa
3aa
3ba
3ea
3af
89
98
36
69
64
78
85
76
75
88
76
82
67
96
91
70
90
95
96
47
70
73
65
92
93
4-F-C6H4
1b
1c
1d
1e
1f
Ph2SO (5a)
a
4-Acet-C6H4
3-Me-C6H4
2-naphthyl
2-pyridyl
3
(4-F-C6H4)2SO (5b)
4
(3-Me-C6H4)2SO (5d)
5
(2-naphthyl)2SO (5e)
6a
(4-MeO-C6H4)2S (4g)
a Acet = MeC(OCH2CMe2CH2O).
7a
(4-MeO-C6H4)2SO (5g)
8
(4-Ph-C6H4)2SO (5h)
We then tried to employ 2-aminopyrimidine (2b) as a
less nucleophilic amine. The reaction of 1a with 2b under
the reaction conditions shown in Table 1 resulted in only a
26% conversion of 1a. After extensive rescreening of the re-
action conditions, we gave up using 1a for the reaction with
2b. We speculate that the methylthiolate anion is a poor
leaving group which hampered the substitution reaction of
the oxidative adduct, Pd(IPr)Ph(SMe), with 2b. With this
hypothesis in mind, diphenyl sulfide (4a) and diphenyl
sulfoxide (5a) were utilized instead of 1a because PhS– and
PhSO– are better leaving groups than MeS–.
9
4a
5a
4a
5a
5g
4a
5a
5g
5h
4a
5a
5b
5e
4a
5a
4a
5a
10
11
12
13a
14
15
16a
17
18b
19b
20b
21b
22c
23c
24
25
This was indeed successful, and the amination proceed-
ed in excellent yields under similar conditions (Table 2, en-
tries 1 and 2). Electron-rich di-4-anisyl sulfide (4g) and
sulfoxide (5g) were aminated, albeit with a higher catalyst
loading under harsher conditions (entries 6 and 7). The re-
action of di-4-fluorophenyl sulfoxide (5b) afforded a mod-
erate yield of product 3bb along with unidentified byprod-
ucts (entry 3). Because of the highly basic reaction condi-
tions, the functional group compatibility of this amination
proved to be moderate. Aminopyrimidines 2c and 2d, pos-
sessing methoxy groups, and 2-aminopyrazine (2e) reacted
smoothly (entries 9–17). 2-Aminopyridine (2a) reacted
more efficiently than 2-aminopyrimidines, requiring only
2.5 mol% of the catalyst (entries 18–21). However, 4-amino-
pyridine (2f) was slightly less reactive than 2a (entries 22
and 23). Under similar conditions, 2-amino-4-trifluoro-
methylpyrimidine and 2-aminothiazole did not participate
in the amination (not shown). Generally, sulfoxides 5 were
more reactive than sulfides 4, probably due to smoother ox-
idative addition and substitution.9d,f,h With these results,
the reactivity of aromatic sulfur compounds was confirmed
to increase in the following order: aryl methyl sulfide < di-
aryl sulfide < diaryl sulfoxide.
2f
3af
2g
2g
3ag
3ag
a 10 mol% SingaCycle-A1, 120 °C, 48 h.
b 2.5 mol% SingaCycle-A1.
c 1.4 equiv 2f.
tion of 2h was found to require diaryl sulfoxides as aryl
electrophiles, a higher temperature of 120 °C, and longer
reaction times of 36–42 hours (Table 3). Notably, direct C–H
arylation at the 8 position was observed in most cases as a
side reaction, affording 6ah and 6hh as byproducts.13 The
reactions of 9-isopropyladenine (2i) resulted in cleaner
crude reaction mixtures and easier chromatographic purifi-
cations, although deprotection was not easy (entries 4–7).
Some chemoselective reactions are worth noting: (1)
Di-4-methylsulfanylphenyl sulfoxide (5i) participated in se-
lective amination at the sulfoxide unit leaving the sulfanyl
group untouched (Scheme 1). (2) Bromothioanisoles under-
went bromo-selective Suzuki–Miyaura coupling or amina-
We then became interested in the amination with 9-
benzyladenine (2h) as adenine is a biologically important
nucleus.12 Because of its poor nucleophilicity, the amina-
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2019, 51, A–H

C
R. Pratap, H. Yorimitsu
Special Topic
Synthesis
Table 3 Reactions with Adenines
the following order: adenines < aminopyrimidines/amino-
pyrazines < 3-aminoquinoline, 4-aminopyridine < 2-amino-
pyridine. To further establish sulfur-based organic synthe-
sis, continued investigations on catalytic transformations of
C–S bonds are ongoing in our laboratory.
H
10 mol% SingaCycle-A1
2.5 equiv KHMDS
N
N
Ar
1.2 equiv 2h or 2i
Ar2SO
N
dioxane, 120 °C, 36–42 h
N
5
NR
3 R’ = H
6 R’ = Ar
R’
Anhydrous toluene and dioxane were purchased from Wako Pure
Chemical Industries, Ltd. and were used directly for reactions. Singa-
Cycle-A1, SingaCycle-A3 and KHMDS (0.5 M solution in toluene) were
purchased from TCI Co. Ltd. Solid KHMDS was purchased from Sigma-
Aldrich. Azaarylamines 2a–g are commercially available. Benzyl- and
isopropyladenine (2h and 2i)14 and diaryl sulfoxides 5b–g15 were pre-
pared according to literature procedures. TLC analyses were per-
formed on commercial glass plates bearing a layer (0.25 mm) of
Merck Silica gel 60F254. Purification was performed by column chro-
matography using silica gel (Wakosil® C-300). Melting points were
measured with a Stanford Research System MPA100 instrument. 1H
NMR (600 MHz) and 13C NMR (151 MHz) spectra were recorded on a
JEOL ECA-600 spectrometer as solutions in CDCl3 (for 1H, δ = 7.26; for
13C, δ = 77.0). Spectroscopic grade solvents were used for all spectro-
scopic studies without further purification. Mass spectra were ob-
tained using a Bruker microTOF II spectrometer.
Entry
5
2
3
Yield (%)
6
Yield (%)
1
2
3
4
5
6
7
5a
5e
5h
5a
5e
5g
5h
2h
2h
2h
2i
3ah
3eh
3hh
3ai
71
71
72
66
72
71
65
6ah
5
0
4
6
2
6
6
6eh
6hh
6ai
2i
3ei
6ei
6gi
6hi
2i
3gi
3hi
2i
tion followed by the C–S-bond-cleaving amination with
2-aminopyridine (Scheme 2).
O
S
5 mol% SingaCycle-A1
3 equiv KHMDS
1.2 equiv 2a or 2b
Amination with 2-Aminopyridine (Table 1); General Procedure 1
To a Schlenk tube were added 2-aminopyridine (2a) (30.8 mg, 0.325
mmol), aryl methyl sulfide 1 (0.25 mmol) and SingaCycle-A1 (12.5
mg, 0.019 mmol, 7.5 mol%) under a nitrogen atmosphere. KHMDS
(1.5 mL, 0.50 M in toluene, 0.75 mmol) was added slowly with stir-
ring. The resulting mixture was stirred at 100 °C for 18–24 h until
completion of the reaction. After completion, the reaction mixture
was poured into water and extracted with ethyl acetate (3 × 20 mL).
The combined organic layer was dried over sodium sulfate and the
solvent was removed under reduced pressure. The obtained crude
product was purified by column chromatography using 25% ethyl ace-
tate in hexane as the eluent.
toluene, 100 °C, 24 h
MeS
SMe
5i
H
N
Y
N
MeS
3ia 74% (Y = CH)
3ib 68% (Y = N)
Scheme 1 Sulfoxide-selective reactions
1) cat. Pd(OAc)2/Sphos
PhB(OH)2, K3PO4
toluene, then isolation
H
N
Amination with Azaarylamines and Diaryl Sulfides/Sulfoxides
(Table 2); General Procedure 2
N
2) Standard conditions
in Table 1
in a different flask
Ph
KHMDS (90 mg, 0.45 mmol), azaarylamine (0.18 mmol), diaryl sul-
fide/sulfoxide (0.15 mmol), and SingaCycle-A1 (5.0 mg, 0.0075 mmol,
5 mol%) were sequentially added to a Schlenk tube under a nitrogen
atmosphere. Toluene (1.0 mL) was added and the resulting mixture
was heated at 100 °C for 24 h. The reaction mixture was poured into
H2O and extracted with ethyl acetate (3 × 20 mL). The combined or-
ganic layer was dried over sodium sulfate and the solvent was re-
moved under reduced pressure. Chromatographic purification of the
crude oil using 25% ethyl acetate in hexane as the eluent provided the
corresponding product 3.
3ha 51%
Br
SMe
7a (4-Br)
7b (3-Br)
H
N
1) cat. SingaCycle-A1
HNR2, KHMDS
toluene (ref 10a)
R2N
N
2) Standard conditions
in Table 1
in the same flask
8a 50% (NR2 = pyrrolidinyl)
8b 50% (NR2 = morpholinyl)
Scheme 2 Iterative cross-couplings of bromothioanisoles
Amination with 9-Benzyl/Isopropyladenine and Diaryl Sulfoxides
(Table 3); General Procedure 3
KHMDS (75 mg, 0.375 mmol), 9-benzyl/isopropyladenine (0.15
mmol), diaryl sulfoxide (0.18 mmol) and SingaCycle-A1 (10 mg, 0.015
mmol, 10 mol%) were added to a Schlenk tube under a nitrogen atmo-
sphere. 1,4-Dioxane (1.0 mL) was then added to the reaction mixture.
After the mixture had been heated at 120 °C for 36–42 h, it was
poured into water and extracted with ethyl acetate (3 × 20 mL). The
combined organic layer was dried over sodium sulfate and the solvent
was removed under reduced pressure. The obtained crude oil was
In summary, we have examined the palladium-cata-
lyzed amination of aryl methyl sulfides, diaryl sulfides and
diaryl sulfoxides with azaarylamines of poor nucleophilici-
ty including adenines. The reactivity of aromatic sulfur
compounds was confirmed to increase in the following or-
der: aryl methyl sulfide < diaryl sulfide < diaryl sulfoxide.
Similarly the reactivity of amines was found to increase in
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2019, 51, A–H

D
R. Pratap, H. Yorimitsu
Special Topic
Synthesis
chromatographed on silica gel using 25% ethyl acetate in hexane as
the eluent to afford diarylated adenines 6, followed by 50% ethyl ace-
tate in hexane to give monoarylated adenines 3.
N-(2-Naphthyl)pyrimidin-2-ylamine (3eb)
Synthesized by general procedure 2.
Yield: 21.2 mg (64%); off-white solid; mp 136–138 °C.
1H NMR (600 MHz, CDCl3): δ = 8.48 (d, J = 4.8 Hz, 2 H), 8.29 (d, J = 2.4
Hz, 1 H), 7.85–7.75 (m, 3 H), 7.57 (dd, J = 5.4, 2.4 Hz, 1 H), 7.53 (br s, 1
H), 7.46–7.43 (m, 1 H), 7.38–7.33 (m, 1 H), 6.76 (t, J = 4.8 Hz, 1 H).
13C NMR (151 MHz, CDCl3): δ = 160.3, 158.1, 136.9, 134.3, 130.0,
128.7, 127.6, 127.4, 126.4, 124.3, 120.5, 115.2, 112.8.
N-Phenylpyridin-2-ylamine (3aa)
Synthesized by general procedure 1. The spectroscopic data are iden-
tical to those reported in the literature.16,17
Yield: 40.4 mg (95%), white solid.
HRMS (ESI): m/z [M + H]+ calcd for C14H12N3: 222.1026; found:
222.1030.
N-(4-Fluorophenyl)pyridin-2-ylamine (3ba)
Synthesized by general procedure 1. The spectroscopic data are iden-
tical to those reported in the literature.16
N-(4-Methoxyphenyl)pyrimidin-2-ylamine (3gb)
Yield: 41.3 mg (88%), off-white solid.
Synthesized by general procedure 2. The spectroscopic data are iden-
tical to those reported in the literature.18,19
N-[4-(2,5,5-Trimethyl-1,3-dioxan-2-yl)phenyl]pyridin-2-ylamine
(3ca)
Yield: 25.6 mg (85%), white solid.
Synthesized by general procedure 1.
N-(Biphenyl-4-yl)pyrimidin-2-ylamine (3hb)
Yield: 53.6 mg (72%), white solid; mp 155–157 °C.
Synthesized by general procedure 2. The spectroscopic data are iden-
tical to those reported in the literature.18
1H NMR (600 MHz, CDCl3): δ = 8.23 (dd, J = 4.8, 1.8 Hz, 1 H), 7.50 (dt,
J = 8.4, 1.8 Hz, 1 H), 7.37 (s, 4 H), 6.89 (d, J = 8.4 Hz, 1 H), 6.76 (br s, 1
H), 6.74 (dd, J = 8.4, 4.8 Hz, 1 H), 3.47 (d, J = 10.9 Hz, 2 H), 3.37 (d, J =
10.9 Hz, 2 H), 1.54 (s, 3 H), 1.33 (s, 3 H), 0.59 (s, 3 H).
13C NMR (151 MHz, CDCl3): δ = 155.7, 148.3, 139.9, 137.6, 134.8,
127.7, 119.8, 115.1, 108.6, 100.1, 71.6, 32.0, 29.9, 22.8, 21.8.
Yield: 28.2 mg (76%), white solid.
2,6-Dimethoxy-N-phenylpyrimidin-4-ylamine (3ac)
Synthesized by general procedure 2. The spectroscopic data are iden-
tical to those reported in the literature.18
HRMS (ESI): m/z [M + H]+ calcd for C18H23N2O2: 299.1754; found:
299.1759.
Yield: 26 mg (75%), white solid.
N-(3-Tolyl)pyridin-2-ylamine (3da)
4,6-Dimethoxy-N-phenylpyrimidin-2-ylamine (3ad)
Synthesized by general procedure 1. The spectroscopic data are iden-
tical to those reported in the literature.16
Synthesized by general procedure 2. The spectroscopic data are iden-
tical to those reported in the literature.20
Yield: 29 mg (63%), white solid.
Yield: 34.5 mg (82%), off-white solid.
N-(Naphthalen-2-yl)pyridin-2-ylamine (3ea)
4,6-Dimethoxy-N-(4-methoxyphenyl)pyrimidin-2-ylamine (3gd)
Synthesized by general procedure 1. The spectroscopic data are iden-
tical to those reported in the literature.16
Synthesized by general procedure 2. The spectroscopic data are iden-
tical to those reported in the literature.20
Yield: 50.6 mg (92%), white solid.
Yield: 26.8 mg (67%), off-white solid.
Di(pyridin-2-yl)amine (3fa)
N-Phenylpyrazin-2-ylamine (3ae)
Synthesized by general procedure 1. The spectroscopic data are iden-
tical to those reported in the literature.17
Synthesized by general procedure 2. The spectroscopic data are iden-
tical to those reported in the literature.17
Yield: 40.2 mg (94%), white solid.
Yield: 24.6 mg (96%), white solid.
N-Phenylpyrimidin-2-ylamine (3ab)
N-(4-Methoxyphenyl)pyrazin-2-ylamine (3ge)
Synthesized by general procedure 2. The spectroscopic data are iden-
tical to those reported in the literature.18,19
Synthesized by general procedure 2. The spectroscopic data are iden-
tical to those reported in the literature.17
Yield: 25.1 mg, white solid (98%).
Yield: 21.1 mg (70%), white solid.
N-(4-Fluorophenyl)pyrimidin-2-ylamine (3bb)
N-(Biphenyl-4-yl)pyrazin-2-ylamine (3he)
Synthesized by general procedure 2.
Synthesized by general procedure 2. The spectroscopic data are iden-
tical to those reported in the literature.19
Yield: 33.3 mg (90%); white solid; mp 186–188 °C.
Yield: 10.2 mg (36%), white solid.
1H NMR (600 MHz, CDCl3): δ = 8.28 (s, 1 H), 8.14 (s, 1 H), 8.00 (d, J =
3.0 Hz, 1 H), 7.59 (t, J = 8.4 Hz, 4 H), 7.52 (d, J = 8.4 Hz, 2 H), 7.44 (t, J =
8.4 Hz, 2 H), 7.33 (t, J = 8.4 Hz, 1 H), 6.61 (br s, 1 H).
13C NMR (151 MHz, CDCl3): δ = 152.0, 141.9, 140.5, 138.4, 136.4,
135.1, 133.2, 128.8, 128.0, 127.0, 126.7, 120.3.
N-(3-Tolyl)pyrimidin-2-ylamine (3db)
Synthesized by general procedure 2. The spectroscopic data are iden-
tical to those reported in the literature.18
Yield: 19.2 mg (69%), white solid.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2019, 51, A–H

E
R. Pratap, H. Yorimitsu
Special Topic
Synthesis
HRMS (ESI): m/z [M + H]+ calcd for C16H14N3: 248.1182; found:
Yield: 32.7 mg (72%); white solid; mp 94–96 °C.
248.1195.
1H NMR (600 MHz, CDCl3): δ = 8.60 (s, 1 H), 8.47 (d, J = 1.4 Hz, 1 H),
8.24 (br s, 1 H), 7.90 (s, 1 H), 7.83–7.81 (m, 2 H), 7.79–7.76 (m, 2 H),
7.47–7.44 (m, 1 H), 7.39–7.36 (m, 1 H), 4.88 (sept, J = 6.8 Hz, 1 H), 1.62
(d, J = 6.8 Hz, 6 H).
13C NMR (151 MHz, CDCl3): δ = 152.6, 152.4, 149.4, 138.3, 136.4,
134.1, 130.3, 128.8, 127.7, 127.6, 126.4, 124.7, 120.9, 120.8, 116.6,
47.3, 22.8.
N-Phenylpyridin-4-ylamine (3af)
Synthesized by general procedure 2. The spectroscopic data are iden-
tical to those reported in the literature.21
Yield: 18.6 mg (73%), white solid.
N-Phenylquinolin-3-ylamine (3ag)
HRMS (ESI): m/z [M + H]+ calcd for C18H18N5: 304.1557; found:
304.1552.
Synthesized by general procedure 2. The spectroscopic data are iden-
tical to those reported in the literature.22
9-Isopropyl-N-(4-methoxyphenyl)-9H-purin-6-ylamine (3gi)
Synthesized by general procedure 3.
Yield: 30.7 mg (93%), white solid.
9-Benzyl-N-phenyl-9H-purin-6-ylamine (3ah)
Yield: 30.1 mg (71%); white solid; mp 170–172 °C.
1H NMR (600 MHz, CDCl3): δ = 8.48 (s, 1 H), 7.86 (s, 1 H), 7.69 (br s, 1
H), 7.63 (d, J = 8.8 Hz, 2 H), 6.93 (d, J = 8.8 Hz, 2 H), 4.86 (sept, J = 6.8
Hz, 1 H), 3.81 (s, 3 H), 1.62 (d, J = 6.8 Hz, 6 H).
Synthesized by general procedure 3. The spectroscopic data are iden-
tical to those reported in the literature.23
Yield: 32.0 mg (71%), white solid.
13C NMR (151 MHz, CDCl3): δ = 156.3, 152.8, 152.7, 149.2, 138.0,
131.6, 122.8, 120.5, 144.4, 55.6, 47.2, 22.8.
HRMS (ESI): m/z [M + H]+ calcd for C15H18N5O: 284.1506; found:
9-Benzyl-N-(2-naphthyl)-9H-purin-6-ylamine (3eh)
Synthesized by general procedure 3.
284.1516.
Yield: 37.4 mg (71%); white solid; mp 167–169 °C.
1H NMR (600 MHz, CDCl3): δ = 8.64 (s, 1 H), 8.46 (d, J = 1.4 Hz, 1 H),
8.04 (br s, 1 H), 7.90–7.71 (m, 5 H), 7.46 (t, J = 7.1 Hz, 1 H), 7.43–7.27
(m, 6 H), 5.39 (s, 2 H).
N-(Biphenyl-4-yl)-9-isopropyl-9H-purin-6-ylamine (3hi)
Synthesized by general procedure 3.
13C NMR (151 MHz, CDCl3): δ = 153.2, 152.4, 149.9, 140.6, 136.3,
135.5, 134.1, 130.4, 129.2, 128.8, 128.6, 127.9, 127.7, 127.6, 126.5,
124.7, 120.8, 120.5, 116.7, 47.4.
HRMS (ESI): m/z [M + H]+ calcd for C22H18N5: 352.1557; found:
352.1554.
Yield: 32.1 mg (65%); white solid; mp 109–111 °C.
1H NMR (600 MHz, CDCl3): δ = 8.57 (s, 1 H), 7.94 (br s, 1 H), 7.90 (s, 1
H), 7.88–7.87 (m, 2 H), 7.63–7.59 (m, 4 H), 7.43 (t, J = 7.8 Hz, 2 H), 7.32
(t, J = 7.8 Hz, 1 H), 4.88 (sept, J = 6.6 Hz, 1 H), 1.64 (d, J = 6.6 Hz, 6 H).
13C NMR (151 MHz, CDCl3): δ = 152.4, 152.1, 149.3, 140.7, 138.2,
138.0, 136.3, 128.7, 127.6, 126.9, 126.8, 120.8, 120.6, 47.2, 22.7.
HRMS (ESI): m/z [M + H]+ calcd for C20H20N5: 330.1713; found:
330.1723.
9-Benzyl-N-(biphenyl-4-yl)-9H-purin-6-ylamine (3hh)
Synthesized by general procedure 3.
Yield: 40.7 mg (72%); white solid; mp 197–199 °C.
9-Benzyl-N,8-diphenyl-9H-purin-6-ylamine (6ah)
Synthesized by general procedure 3.
1H NMR (600 MHz, CDCl3): δ = 8.61 (s, 1 H), 7.98–7.85 (m, 3 H), 7.82
(s, 1 H), 7.69–7.56 (m, 4 H), 7.51–7.41 (m, 2 H), 7.41–7.28 (m, 6 H),
5.41 (s, 2 H).
Yield: 2.9 mg (5%); white solid; mp 156–158 °C.
13C NMR (151 MHz, CDCl3): δ = 153.2, 152.3, 149.9, 140.8, 140.6,
138.1, 136.5, 135.5, 129.2, 128.8, 128.6, 127.9, 127.8, 127.1, 126.9,
120.7, 120.4, 47.4.
1H NMR (600 MHz, CDCl3): δ = 8.58 (s, 1 H), 8.14 (br s, 1 H), 7.83 (d, J =
7.8 Hz, 1 H), 7.81 (br s, 1 H), 7.60 (d, J = 6.6 Hz, 2 H), 7.50–7.45 (m, 3
H), 7.38 (t, J = 8.1 Hz, 2 H), 7.29–7.24 (m, 3 H), 7.11–7.07 (m, 3 H), 5.50
(s, 2 H).
HRMS (ESI): m/z [M + H]+ calcd for C24H20N5: 378.1713; found:
13C NMR (151 MHz, CDCl3): δ = 152.9, 152.0, 151.9, 151.5, 138.9,
136.4, 130.4, 129.6, 129.2, 129.1, 129.0, 128.9, 127.9, 126.7, 123.5,
120.2, 47.1.
378.1706.
9-Isopropyl-N-phenyl-9H-purin-6-ylamine (3ai)
Synthesized by general procedure 3.
HRMS (ESI): m/z [M + H]+ calcd for C24H20N5: 378.1713; found:
378.1717.
Yield: 25 mg (66%); white solid; mp 104–106 °C.
1H NMR (600 MHz, CDCl3): δ = 8.54 (s, 1 H), 7.89 (s, 1 H), 7.84 (br s, 1
H), 7.79 (d, J = 7.8 Hz, 2 H), 7.38 (t, J = 7.8 Hz, 2 H), 7.10 (t, J = 7.5 Hz, 1
H), 4.87 (sept, J = 7.2 Hz, 1 H), 1.63 (d, J = 7.2 Hz, 6 H).
9-Benzyl-N,8-bis(biphenyl-4-yl)-9H-purin-6-ylamine (6hh)
Synthesized by general procedure 3.
13C NMR (151 MHz, CDCl3): δ = 152.5, 152.3, 149.3, 138.8, 138.2,
Yield: 3.2 mg (4%); white solid; mp 218–220 °C.
1H NMR (600 MHz, CDCl3): δ = 8.62 (s, 1 H), 7.93 (d, J = 8.2 Hz, 2 H),
7.85 (br s, 1 H), 7.74–7.70 (m, 4 H), 7.65–7.63 (m, 6 H), 7.49–7.39 (m,
5 H), 7.35–7.28 (m, 4 H), 7.15 (d, J = 7.5 Hz, 2 H), 5.47 (s, 2 H).
129.1, 123.5, 120.8, 120.4, 47.2, 22.8.
HRMS (ESI): m/z [M + H]+ calcd for C14H16N5: 254.1400; found:
254.1394.
13C NMR (151 MHz, CDCl3): δ = 152.9, 151.8, 151.7, 151.6, 143.1,
140.7, 139.9, 138.1, 136.4, 136.3, 129.5, 129.0, 128.8, 128.3, 128.1,
128.0, 127.9, 127.7, 127.6, 127.2, 127.1, 126.9, 126.8, 120.4, 120.3,
47.1.
9-Isopropyl-N-(2-naphthyl)-9H-purin-6-ylamine (3ei)
Synthesized by general procedure 3.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2019, 51, A–H

F
R. Pratap, H. Yorimitsu
Special Topic
Synthesis
HRMS (ESI): m/z [M + H]+ calcd for C36H28N5: 530.2339; found:
HRMS (ESI): m/z [M + H]+ calcd for C32H28N5: 482.2339; found:
530.2329.
482.2335.
9-Isopropyl-N,8-diphenyl-9H-purin-6-ylamine (6ai)
Synthesized by general procedure 3.
N-(4-Methylsulfanylphenyl)pyridin/pyrimidin-2-ylamines 3ia and
3ib
KHMDS (90 mg, 0.45 mmol), azaarylamine (0.18 mmol), bis(4-meth-
ylsulfanylphenyl) sulfoxide (5i) (44 mg, 0.15 mmol), and SingaCycle-
A1 (5.0 mg, 0.0075 mmol, 5 mol%) were sequentially added to a
Schlenk tube under a nitrogen atmosphere. Toluene (1.0 mL) was add-
ed and the resulting mixture was heated at 100 °C for 24 h. The reac-
tion mixture was poured into water and extracted with ethyl acetate
(3 × 20 mL). The combined organic layer was dried over sodium sul-
fate and the solvent was removed under reduced pressure. Chromato-
graphic purification of the crude oil using 25% ethyl acetate in hexane
as the eluent provided the corresponding product.
Yield: 3.0 mg (6%); white solid; mp 156–158 °C.
1H NMR (600 MHz, CDCl3): δ = 8.55 (s, 1 H), 7.82 (d, J = 8.8 Hz, 2 H),
7.70 (br s, 1 H), 7.66–7.62 (m, 2 H), 7.57–7.56 (m, 3 H), 7.42–7.36 (m,
2 H), 7.10 (t, J = 7.5 Hz, 1 H), 4.74 (sept, J = 6.8 Hz, 1 H), 1.57 (d, J = 6.8
Hz, 6 H).
13C NMR (151 MHz, CDCl3): δ = 152.0, 151.7, 151.4, 150.8, 138.9,
130.3, 130.2, 129.3, 129.1, 129.0, 123.2, 120.8, 120.1, 49.7, 21.4.
HRMS (ESI): m/z [M + H]+ calcd for C20H20N5: 330.1713; found:
330.1710.
N-(4-Methylsulfanylphenyl)pyridin-2-ylamine (3ia)
9-Isopropyl-N,8-di(2-naphthyl)-9H-purin-6-ylamine (6ei)
Synthesized by general procedure 3.
Yield: 24.0 mg (74%); white solid; mp 118–120 °C.
1H NMR (600 MHz, CDCl3): δ = 8.19 (d, J = 4.8 Hz, 1 H), 7.48 (dt, J = 8.4,
1.8 Hz, 1 H), 7.29–7.27 (m, 4 H), 6.81 (d, J = 8.4 Hz, 1 H), 6.79 (br s, 1
H), 6.72 (t, J = 6.6 Hz, 1 H), 2.47 (s, 3 H).
13C NMR (151 MHz, CDCl3): δ = 155.9, 148.3, 138.3, 137.7, 131.4,
128.9, 121.0, 115.0, 108.3, 17.2.
Yield: 1.3 mg (2%); white solid; mp 90–92 °C.
1H NMR (600 MHz, CDCl3): δ = 8.64 (s, 1 H), 8.52 (s, 1 H), 8.18 (s, 1 H),
8.04 (d, J = 8.8 Hz, 1 H), 7.98–7.95 (m, 2 H), 7.91 (br s, 1 H), 7.86 (t, J =
8.8 Hz, 2 H), 7.80–7.77 (m, 2 H), 7.73–7.72 (m, 1 H), 7.63–7.60 (m, 2
H), 7.47 (t, J = 7.2 Hz, 1 H), 7.39 (t, J = 7.2 Hz, 1 H), 4.84 (sept, J = 6.6
Hz, 1 H), 1.79 (d, J = 6.6 Hz, 6 H).
HRMS (ESI): m/z [M + H]+ calcd for C11H13N2S: 217.0794; found:
13C NMR (151 MHz, CDCl3): δ = 152.1, 151.9, 151.6, 151.0, 146.9,
137.1, 136.6, 134.8, 134.2, 133.8, 133.0, 131.6, 130.2, 129.6, 128.9,
128.8, 128.6, 128.0, 127.6, 127.2, 126.5, 125.9, 124.6, 120.6, 116.2,
49.9, 21.5.
HRMS (ESI): m/z [M + H]+ calcd for C28H24N5: 430.2026; found:
430.2013.
217.0799.
N-(4-Methylsulfanylphenyl)pyrimidin-2-ylamine (3ib)
Yield: 22.0 mg (68%); white solid; mp 133–135 °C.
1H NMR (600 MHz, CDCl3): δ = 8.41 (d, J = 4.8 Hz, 2 H), 7.56–7.55 (m, 3
H), 7.29 (d, J = 9.0 Hz, 2 H), 6.71 (t, J = 4.8 Hz, 1 H), 2.47 (s, 3 H).
13C NMR (151 MHz, CDCl3): δ = 160.1, 157.9, 137.3, 131.4, 128.7,
120.3, 112.5, 17.2.
HRMS (ESI): m/z [M + H]+ calcd for C11H12N3S: 218.0746; found:
9-Isopropyl-N,8-bis(4-methoxyphenyl)-9H-purin-6-ylamine (6gi)
Synthesized by general procedure 3.
Yield: 3.5 mg (6%); white solid; mp 70–72 °C.
218.0755.
1H NMR (600 MHz, CDCl3): δ = 8.48 (s, 1 H), 7.65 (d, J = 8.4 Hz, 2 H),
7.57 (d, J = 8.4 Hz, 3 H), 7.07 (d, J = 8.4 Hz, 2 H), 6.93 (d, J = 8.4 Hz, 2 H),
4.72 (sept, J = 6.8 Hz, 1 H), 3.89 (s, 3 H), 3.81 (s, 3 H), 1.73 (d, J = 6.8 Hz,
6 H).
13C NMR (151 MHz, CDCl3): δ = 161.1, 156.1, 152.2, 151.7, 151.2,
150.8, 131.9, 130.8, 122.6, 122.4, 120.5, 114.5, 114.4, 55.6, 55.5, 46.6,
21.4.
N-(Biphenyl-4-yl)pyridin-2-ylamine (3ha)
To a Schlenk tube were added 4-bromothioanisole (7a) (304 mg, 1.63
mmol), phenylboronic acid (270 mg, 2.21 mmol), Pd(OAc)2 (11 mg,
0.049 mmol), SPhos (19 mg, 0.046 mmol), and K3PO4 (424 mg, 3.12
mmol) under an argon atmosphere. Toluene (4.5 mL) was then added
and the mixture heated at 110 °C for 24 h. After complete conversion,
the reaction mixture was cooled to room temperature. Chromato-
graphic purification afforded 4-methylsulfanylbiphenyl (260 mg, 1.30
mmol, 80% yield).
HRMS (ESI): m/z [M + H]+ calcd for C22H24N5O2: 390.1925; found:
390.1940.
2-Aminopyridine (2a) (28.2 mg, 0.30 mmol), 4-methylsulfanylbiphe-
nyl (50 mg, 0.25 mmol), SingaCycle-A1 (12.5 mg, 0.019 mmol), and
KHMDS (150 mg, 0.75 mmol) were placed in a Schlenk tube under a
nitrogen atmosphere and the resulting mixture was stirred at 100 °C
for 24 h. The reaction mixture was poured into water and extracted
with ethyl acetate (3 × 30 mL). The combined organic layer was dried
over sodium sulfate and the solvent was removed under reduced
pressure. The obtained crude product was purified by column chro-
matography using 25% ethyl acetate in hexane as the eluent to yield
3ha.
N,8-Bis(biphenyl-4-yl)-9-isopropyl-9H-purin-6-ylamine (6hi)
Synthesized by general procedure 3.
Yield: 4.3 mg (6%); white solid; mp 76–78 °C.
1H NMR (600 MHz, CDCl3): δ = 8.59 (s, 1 H), 7.92–7.90 (m, 2 H), 7.80
(d, J = 8.5 Hz, 2 H), 7.80 (br s, 1 H), 7.74 (d, J = 7.8 Hz, 2 H), 7.69 (d, J =
6.8 Hz, 2 H), 7.64–7.60 (m, 4 H), 7.51 (t, J = 7.2 Hz, 2 H), 7.45–7.41 (m,
3 H), 7.34–7.32 (m, 1 H), 4.83 (sept, J = 6.8 Hz, 1 H), 1.80 (d, J = 6.8 Hz,
6 H).
13C NMR (151 MHz, CDCl3): δ = 151.8, 151.7, 151.2, 150.9, 143.1,
140.7, 140.0, 138.2, 136.1, 129.7, 129.0, 128.7, 128.0, 127.7, 127.6,
127.2, 126.9, 126.8, 120.9, 120.3, 49.8, 21.4.
The spectroscopic data are identical to those reported in the litera-
ture.16
Yield: 31.4 mg (51%); white solid.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2019, 51, A–H

G
R. Pratap, H. Yorimitsu
Special Topic
Synthesis
Diamines 8a and 8b
Chem. Res. 2008, 41, 1534. (e) Torborg, C.; Beller, M. Adv. Synth.
Catal. 2009, 351, 3027. (f) Surry, D. S.; Buchwald, S. L. Chem. Sci.
2011, 2, 27. (g) Ruiz-Castillo, P.; Buchwald, S. L. Chem. Rev. 2016,
116, 12564. (h) Martín, M.; Rama, R. J.; Nicasio, M. C. Chem. Rec.
2016, 16, 1819. (i) Schranck, J.; Tlili, A. ACS Catal. 2018, 8, 405.
(2) For pioneering work on the amination of aryl mesylates, see:
(a) So, C. M.; Zhou, Z.; Lau, C.; Kwong, F. Y. Angew. Chem. Int. Ed.
2008, 47, 6402. (b) Fors, B. P.; Watson, D. A.; Biscoe, M. R.;
Buchwald, S. L. J Am. Chem. Soc. 2008, 130, 13552.
In a Schlenk tube were placed SingaCycle-A1 (8.3 mg, 0.0125 mmol),
3-bromothioanisole (7b) (101 mg, 0.50 mmol), and pyrrolidine/mor-
pholine (0.55 mmol). KHMDS (1.5 mL, 0.5 M in toluene, 0.75 mmol)
was then added and the reaction mixture was heated at 80 °C for 14 h.
After completion of the reaction as confirmed by TLC, the mixture
was cooled to room temperature. 2-Aminopyridine (2a) (56.4 mg,
0.60 mmol), SingaCycle-A1 (24.9 mg, 0.0375 mmol), and KHMDS (300
mg, 1.50 mmol) were sequentially added to the mixture under a ni-
trogen atmosphere and the resulting mixture was stirred at 100 °C for
30 h. The reaction mixture was poured into water and extracted with
ethyl acetate (3 × 30 mL). The combined organic layer was dried over
sodium sulfate and the solvent was removed under reduced pressure.
Chromatographic purification of the crude oil using 25% ethyl acetate
in hexane as the eluent provided the corresponding products 8a and
8b.
(3) Of aryl phosphates, see: Huang, J.-H.; Yang, L.-M. Org. Lett. 2011,
13, 3750.
(4) Of aryl sulfamates, see: (a) Ramgren, S. D.; Silberstein, A. L.;
Yang, Y.; Garg, N. K. Angew. Chem. Int. Ed. 2011, 50, 2171.
(b) Ackermann, L.; Sandmann, R.; Song, W. Org. Lett. 2011, 13,
1784. (c) Hie, L.; Ramgren, S. D.; Mesganaw, T.; Garg, N. K. Org.
Lett. 2012, 14, 4182. (d) Park, N. H.; Teverovskiy, G.; Buchwald, S.
L. Org. Lett. 2014, 16, 220. (e) Nathel, N. F. F.; Kim, J.; Hie, L.;
Jiang, X.; Garg, N. K. ACS Catal. 2014, 4, 3289. (f) Lavoie, C. M.;
MacQueen, P. M.; Stradiotto, M. Chem. Eur. J. 2016, 22, 18752.
(g) MacQueen, P. M.; Stradiotto, M. Synlett 2017, 28, 1652.
(5) Of aryl carbamates, see: (a) Mesganaw, T.; Silberstein, A. L.;
Ramgren, S. D.; Nathel, N. F. F.; Hong, X.; Liu, P.; Garg, N. K.
Chem. Sci. 2011, 2, 1766. (b) Schranck, J.; Furer, P.; Hartmann,
V.; Tlili, A. Eur. J. Org. Chem. 2017, 3496; see also references 4c
and 4g.
N-[3-(Pyrrolidin-1-yl)phenyl]pyridin-2-ylamine (8a)
Yield: 59.8 mg (50%); white solid; mp 85–87 °C.
1H NMR (600 MHz, CDCl3): δ = 8.20 (dd, J = 4.8, 1.8 Hz, 1 H), 7.46 (dt,
J = 8.4, 1.8 Hz, 1 H), 7.18 (t, J = 8.4 Hz, 1 H), 7.03 (br s, 1 H), 6.98 (d, J =
8.4 Hz, 1 H), 6.67 (dd, J = 7.2, 4.8 Hz, 1 H), 6.61 (dd, J = 7.2, 2.4 Hz, 1 H),
6.49 (t, J = 2.4 Hz, 1 H), 6.31 (dd, J = 7.2, 2.4 Hz, 1 H), 3.28 (t, J = 6.6 Hz,
4 H), 2.00 (quin, J = 3.6 Hz, 4 H).
13C NMR (151 MHz, CDCl3): δ = 156.6, 148.9, 148.4, 141.3, 137.5,
129.7, 114.4, 108.1, 107.9, 106.9, 104.1, 47.5, 25.4.
HRMS (ESI): m/z [M + H]+ calcd for C15H18N3: 240.1495; found:
240.1491.
(6) Of aryl esters, see: (a) Shimasaki, T.; Tobisu, M.; Chatani, N.
Angew. Chem. Int. Ed. 2010, 49, 2929. (b) Yue, H.; Guo, L.; Liu, X.;
Rueping, M. Org. Lett. 2017, 19, 1788.
(7) Of aryl ethers, see: (a) Tobisu, M.; Shimasaki, T.; Chatani, N.
Chem. Lett. 2009, 38, 710. (b) Tobisu, M.; Yasutome, A.;
Yamakawa, K.; Shimasaki, T.; Chatani, N. Tetrahedron 2012, 68,
5157. (c) Li, J.; Wang, Z.-X. Org. Lett. 2017, 19, 3723.
N-[3-(Morpholin-4-yl)phenyl]pyridin-2-ylamine (8b)
Yield: 63.8 mg (50%); white solid; mp 118–120 °C.
(8) For reviews, see: (a) Dubbaka, S. R.; Vogel, P. Angew. Chem. Int.
Ed. 2005, 44, 7674. (b) Wang, L.; He, W.; Yu, Z. Chem. Soc. Rev.
2013, 42, 599. (c) Modha, S. G.; Mehta, V. P.; Van der Eycken, E.
V. Chem. Soc. Rev. 2013, 42, 5042. (d) Pan, F.; Shi, Z.-J. ACS Catal.
2014, 4, 280. (e) Gao, K.; Otsuka, S.; Baralle, A.; Nogi, K.;
Yorimitsu, H.; Osuka, A. J. Synth. Org. Chem. Jpn. 2016, 74, 1119.
(f) Ortgies, D. H.; Hassanpour, A.; Chen, F.; Woo, S.; Forgione, P.
Eur. J. Org. Chem. 2016, 408. (g) Otsuka, S.; Nogi, K.; Yorimitsu,
H. Top. Curr. Chem. 2018, 376, 13. (h) Liu, H.; Jiang, X. Chem.
Asian J. 2013, 8, 2546. (i) Li, Y.; Pu, J.; Jiang, X. Org. Lett. 2014, 16,
2692; and references cited therein.
1H NMR (600 MHz, CDCl3): δ = 8.20 (dd, J = 6.0, 1.2 Hz, 1 H), 7.22 (t, J =
8.4 Hz, 1 H), 6.91–6.88 (m, 3 H), 6.82 (dd, J = 8.4, 1.2 Hz, 1 H), 6.71 (dd,
J = 6.6, 1.8 Hz, 1 H), 6.62 (dd, J = 8.4, 1.8 Hz, 1 H), 3.85 (t, J = 4.8 Hz, 4
H), 3.16 (t, J = 4.8 Hz, 4 H).
13C NMR (151 MHz, CDCl3): δ = 156.2, 152.3, 148.4, 141.4, 137.6,
129.8, 114.8, 112.1, 110.3, 108.3, 107.8, 66.8, 49.2.
HRMS (ESI): m/z [M + H]+ calcd for C15H18N3O: 256.1444; found:
256.1443.
(9) For very recent examples from our group, see: (a) Saito, H.;
Nogi, K.; Yorimitsu, H. Chem. Lett. 2017, 46, 1122. (b) Vasu, D.;
Hausmann, J. N.; Saito, H.; Yanagi, T.; Yorimitsu, H.; Osuka, A.
Asian J. Org. Chem. 2017, 6, 1390. (c) Saito, H.; Nogi, K.;
Yorimitsu, H. Synthesis 2017, 49, 4769. (d) Yamamoto, K.; Nogi,
K.; Yorimitsu, H. ACS Catal. 2017, 7, 7623. (e) Gao, K.;
Yamamoto, K.; Nogi, K.; Yorimitsu, H. Synlett 2017, 28, 2956.
(f) Yoshida, Y.; Nogi, K.; Yorimitsu, H. Synlett 2017, 28, 2561.
(g) Minami, H.; Otsuka, S.; Nogi, K.; Yorimitsu, H. ACS Catal.
2018, 8, 579. (h) Yoshida, Y.; Nogi, K.; Yorimitsu, H. Org. Lett.
2018, 20, 1134. (i) Otsuka, S.; Nogi, K.; Yorimitsu, H. Angew.
Chem. Int. Ed. 2018, 57, 6653. (j) Uno, D.; Minami, H.; Otsuka, S.;
Nogi, K.; Yorimitsu, H. Chem. Asian J. 2018, 13, 2397. (k) Minami,
H.; Nogi, K.; Yorimitsu, H. Heterocycles 2018, 97, 998.
(10) (a) Sugahara, T.; Murakami, K.; Yorimitsu, H.; Osuka, A. Angew.
Chem. Int. Ed. 2014, 53, 9329. (b) Gao, K.; Yorimitsu, H.; Osuka,
A. Eur. J. Org. Chem. 2015, 2678.
(11) (a) Kantchev, E. A. B.; Ying, J. Y. Organometallics 2009, 28, 289.
(b) Peh, G.-R.; Kantchev, E. A. B.; Er, J.-C.; Ying, J. Y. Chem. Eur. J.
2010, 16, 4010.
Funding Information
This work was supported by JSPS KAKENHI Grant Numbers
JP16H04109, JP18H04252, and JP18H04409. R.P. acknowledges the
award of a JSPS Invitational Fellowship.
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Supporting Information
Supporting information for this article is available online at
https://doi.org/10.1055/s-0037-1611732.
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References
(1) Selected reviews: (a) Wolfe, J. P.; Wagaw, S.; Marcoux, J.-F.;
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Special Topic
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© Georg Thieme Verlag Stuttgart · New York — Synthesis 2019, 51, A–H