General rhodium-catalyzed oxidative cross-coupling reactions between anilines: Synthesis of unsymmetrical 2,2′-diaminobiaryls

Article abstract of DOI:10.1039/c9cc01733j

Described herein is a dual chelation-assisted RhCl₃-catalyzed oxidative C-H/C-H cross-coupling reaction of aniline derivatives. The highlight of this methodology is the chemo- and regioselective cross-coupling between electronically similar substrates, which represents a highly challenging task in oxidative Ar-H/Ar-H cross-coupling reactions. Furthermore, this Cp?-free catalytic reaction tolerates a range of functional groups and requires only a low molar ratio of coupling partners. These features expedite the synthesis of unsymmetrical 2,2′-diaminobiaryls.

Full text of DOI:10.1039/c9cc01733j

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DOI: 10.1039/C9CC01733J
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General rhodium-catalyzed oxidative cross-coupling reactions
between anilines: synthesis of unsymmetrical 2,2’-diaminobiaryls
Received 00th January 20xx,
Accepted 00th January 20xx
Yang Shi, Jiahui Liu, Yudong Yang* and Jingsong You*
DOI: 10.1039/x0xx00000x
www.rsc.org/
Described herein is a dual chelation-assisted RhCl
3
-catalyzed distinct anilides were used as the coupling partners, which reduces
8
oxidative C–H/C–H cross-coupling reaction of aniline derivatives. the practicability of this methodology. Thus, the development of a
The highlight of this methodology is the chemo- and regioselective more general oxidative C–H/C–H cross-coupling reaction of anilines
cross-coupling between electronically similar substrates, which that could discriminate the subtle differences of electronic natures
represents a highly challenging task in oxidative Ar–H/Ar–H cross- on substrates is demanded.
*
coupling reactions. Furthermore, this Cp -Free catalytic reaction
Previous work: requiring electronically (de)activating groups
tolerates a range of functional groups and requires only a low
molar ratio of coupling partners. These features expedite the
synthesis of unsymmetrical 2,2’-diaminobiaryls.
2
017, Waldvogel
NHPG1
NHPG1
NHPG2
H
anode
HFIP/MeOH
R1
R1
R2
+
Bu3NMeO3SOMe, 50 °C
undivided cell
R2
H
2
PG HN
2
,2’-Diaminobiaryls are often found in many functional molecules
1
2
3
• Only electron-donating groups
2018, Lu
• Blocking groups at para position
• Medium yields
such as ligands, organocatalysts, and synthetic intermediates.
O
N
R1
H
Traditional methods to access the symmetric 2,2’-diaminobiaryls
4
Pd(OAc)2
K2S2O8
N
O
mainly depend on Ullmann reaction. The preparation of
H
N
H
N
R1
R3
R2
R2
+
R4
unsymmetrical 2,2’-diaminobiaryls typically involves Suzuki-Miyaura
R4
O
O
MsOH/CF COOH
3
H
H
H
cross-coupling reactions of ortho-halogenated and borylated
25 °C
5
R2
anilines. Despite reliable approaches, these methods suffer from
(1 equiv)
(up to 30 equiv)
• Large substrate ratio
• R2 = EDG, R4 = EWG
tedious synthetic routes, limited substrate scope and large amount
of toxic halide wastes. From the viewpoint of step economy and
substrate availability, direct oxidative Ar–H/Ar–H cross-coupling
reaction is considered as one of the most concise and efficient
This work: enabling discrimination of electronically similar substrates
NHAc
RhCl3•3H2O
AgOTFA
NHAc
H
NHPiv
H
R1
R1
R2
+
Cu(OTFA)2•xH2O
mesitylene
R2
6
strategies for the construction of 2,2’-difunctional biaryls. However,
PivHN
(
1 equiv)
Broad substrate scope
Compatibility of electronically similar substrates
(1.2 equiv)
controlling the chemo- and regioselectivity of each coupling
partners in this strategy to access unsymmetrical 2,2’-difunctional
biaryls is still a highly challenging task, which mainly relies on steric
and electronic effects.
•
•
• Good functional group tolerance
• Low molar ratio of substrates
• Complete regiocontrol
• Cp* ligand free
Scheme 1. Oxidative cross-coupling reactions between anilines.
In 2017, Waldvogel and co-workers reported an electrochemical
C–C cross-coupling reaction of highly electron-rich anilines with a
7
blocking group at the para-position. Later, Lu described a
The dual chelation-assisted strategy is considered as an ideal
palladium-catalyzed cross-coupling of anilides by employing a approach to control the regioselectivity for both coupling partners
9
significant excess amount of substrate (up to 30 equivalents) to in oxidative Ar–H/Ar–H cross-coupling reaction. Based on this
assure the output of the cross-coupled biaryl. Moreover, to ensure strategy, we recently described a unique RhCl
3
/TFA (TFA =
a
high cross-coupling/homo-coupling selectivity, electronically trifluoroacetic acid) catalytic system to promote the oxidative cross-
coupling reactions between benzamides and anilines, in which the
coupling partners possess distinctly different electronical natures,
1
0
by selection of a matched directing group pair. In response to the
challenge mentioned above, herein, we wish to disclose a dual
chelation-assisted oxidative C–H/C–H cross-coupling reaction of
anilines for synthesis of unsymmetrical 2,2’-diaminobiaryls by
making use of a modified rhodium catalytic system. Notably, no
Key Laboratory of Green Chemistry and Technology of Ministry of Education,
College of Chemistry, Sichuan University, 29 Wangjiang Road, Chengdu 610064,
P. R. China. E-mail: jsyou@scu.edu.cn; yangyudong@scu.edu.cn
Electronic Supplementary Information (ESI) available: Experimental procedures,
characterization data and copies of NMR spectra, see DOI: 10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
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electronically activating/deactivating functional groups and blocking directing group pair for this reaction. The reaVicetwioAnrtsicle uOsnilninge
groups on the aryl ring are necessary, and only a low molar ratio of toluenesulfonamido as the directing group gDaOveI: 1n0o.1d0e39si/rCe9dCpCr0o1d73u3cJt
coupling partners is required in this reaction.
(SI, Table S2).
Table 1. Optimization of the reaction conditionsa
Table 2. Scope of N-phenylpivalamidesa,b
NHPiv
NHPiv
RhCl3•3H2O (5.0 mol%)
AgOTFA (3.0 equiv)
NHPiv
H
NHAc
H
R1
NHPiv
H
NHAc
H
[
Rh]/AgOTFA (3.0 equiv)
additive (20 mol%)
+
R1
+
Cu(OTFA)2•xH2O (20 mol%)
mesitylene, 140 °C, 24 h
solvent (0.5 mL), 140 °C, 24 h
AcHN
AcHN
3a
1
a
2a
1
2a
3
b
NHPiv
NHPiv
NHPiv
NHPiv
Entry
[Rh]
Additive
Solvent
Yield (%)
*
1
2
3
4
5
6
7
8
9
[Cp RhCl
2
2
2
2
2
2
2
2
2
2
2
2
]
]
]
]
]
]
2
2
2
2
2
2
Cu(OAc)
2
2
2
2
2
2
2
·H
·H
·H
·H
·H
·H
·H
2
2
2
2
2
2
2
O
O
O
O
O
O
O
mesitylene
1,4-dioxane
DCE
53
nd
*
AcHN
a, 78%
AcHN
3b, 45%
AcHN
AcHN
[Cp RhCl
Cu(OAc)
Cu(OAc)
Cu(OAc)
Cu(OAc)
Cu(OAc)
Cu(OAc)
3
3c, 83%
3d, 80%
*
[Cp RhCl
nd
NHPiv
*
MeO
MeO
NHPiv
O
O
NHPiv Ph
NHPiv
[Cp RhCl
THF
nd
*
[Cp RhCl
DMF
trace
45
R
*
AcHN
e, R = OMe, 64%
3f, R = OPiv, 67%
[Cp RhCl
HFIP
AcHN
h, 72%
AcHN
3i, 86%
AcHN
3
3
3j, 71%
RhCl
RhCl
RhCl
RhCl
RhCl
RhCl
3
·3H
3
·3H
3
·3H
3
·3H
3
·3H
3
·3H
O
O
O
O
O
O
mesitylene
mesitylene
mesitylene
mesitylene
mesitylene
mesitylene
60
3g, R = tBu, 85%
CuI
Cu(acac)
58
NHPiv
Br
NHPiv
NHPiv
2
trace
70
3
k, R = CO Et, 64%
2
1
0
Cu(OTFA)
Cu(OTFA)
Cu(OTFA)
2
·xH
2
·xH
2
·xH
2
O
2
O
2
O
R
3l, R = Cl, 60%
1c
2c,d
78
3m, R = CF3, 50%
n, R = I, 42%
AcHN
1
AcHN
o, 58%
AcHN
3
3
3p, 65%
1
67
NHPiv
NHPiv
NHPiv
a
Reaction conditions: 1a (0.2 mmol, 1.0 equiv), 2a (0.2 mmol, 1.0
equiv), [Cp*RhCl
2
]
2
(2.5 mol %) or RhCl
3
·3H
2
O (5.0 mol %), AgOTFA
MeO2C
(
2
3.0 equiv), and additive (20 mol %) in solvent (0.5 mL) at 140 °C for
AcHN
3s, 69%
AcHN
3q, 70%
AcHN
b
c
4 h under N
2
atmosphere. Isolated yield. 1.2 equiv of 1a was
3r, 70%
d
used.
The reaction was carried out for 12 h. HFIP =
unreactive substrates:
NHPiv
hexafluoroisopropanol.
S
NHPiv
S
NHPiv
O
NHPiv
OHC
Ac
1t
1u
1v
1w
Initially, an equimolar amount of N-phenylpivalamide (1a) and N-
phenylacetamide (2a), which could be readily prepared by acylation
a
Reaction was performed with 1 (0.24 mmol, 1.2 equiv), and 2a (0.2
reaction, was used as the model substrate (Table 1). In the presence mmol, 1.0 equiv) in mesitylene (0.5 mL) at 140 °C for 24 h under N
2
*
b
of [Cp RhCl
2
]
2
(2.5 mol%), AgOTFA (3.0 equiv), and Cu(OAc)
2
·H
2
O
atmosphere.
Isolated
yield.
(20 mol%) as an additive in mesitylene at 140 °C, to our delight, the
cross-coupled product 3a could be obtained in 53% yield with only
trace amounts of homo-coupled products (Table 1, entry 1). Next,
With the optimal reaction conditions in hand, we then
common solvents such as 1,4-dioxane, DCE, THF and DMF were explored the substrate scope of N-phenylpivalamides. As shown
tested and proved to be ineffective for this transformation. HFIP in Table 2, a variety of N-phenylpivalamides with substituents on
gave a slightly inferior result, affording the desired product in 45% ortho-, meta- and para-positions could work smoothly under
yield (Table 1, entries 2-6). The attempt with RhCl
3
·3H
2
O instead of the standard conditions to give the desired 2,2’-diaminobiaryl
*
*
[
Cp RhCl
2
]
2
led to a higher yield, illustrating that Cp might not be derivatives in moderate to high yields (Table 2, 3b-3d). However,
1
1
crucial in this reaction (Table 1, entry 7). Further screening of the presence of a substituent at the ortho-position on the phenyl
additives demonstrated that Cu(OTFA) ·xH was the most ring decreased the reaction efficiency, probably owing to the
2
2
O
effective (Table 1, entries 8-10). However, no reaction was detected enhanced steric hindrance (Table 2, 3b). Both electron-donating
using stoichiometric amounts of copper salts instead of AgOTFA as groups such as alkoxy, pivaloyl, alkyl, and phenyl and electron-
the oxidant, excluding the possibility of Cu(OTFA) •xH O as an withdrawing groups such as ester, bromo, chloro, iodo and
2 2
oxidant in this reaction (SI, Table S1, entries 14 and 15). Increasing trifluoromethyl were accommodated perfectly (Table 2, 3e-3o).
the amount of phenylpivalamide 1a to 1.2 equiv could further In addition, α- and β-naphthylamines could also react with 2a
improve reaction efficiency, leading to a 78% isolated yield (Table 1, to deliver the biaryl products with high chemo- and
entry 11; for more details for the condition optimization, see SI). In regioselectivity (Table 2, 3p and 3q). It is worthy of note that
addition, extensive exploitation of the directing groups indicated the potentially reactive methylene and alkenyl moieties
that only the pivalamido and acetamido groups are a suitable
2
| J. Name., 2012, 00, 1-3
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toward oxidative conditions remained intact in this protocol in the presence of KOH and HCl, respectively, whicVhiewprAortvicidleeOsnlainne
Table 2, 3r and 3s). However, N-(4-acetylphenyl)pivalamide opportunity for further selective transformDaOtiIo:n10s.1(0S3c9h/eCm9CeC20,17e3q3nJ
(
and pivalamides contained heteroaryls such as thiophene and (3)).
furan failed to undergo the desired reaction (Table 2, 1t-1w).
Finally, a series of control experiments were conducted to probe
Next, the scope of N-phenylacetamides was evaluated as the reaction mechanism. Under the standard condition, treatment
depicted in Table 3. N-Phenylacetamides bearing various of either N-phenylpivalamide 1a or N-phenylacetamide 2a with D
2
O
substituents at different positions reacted smoothly with N- (20.0 equiv) led to a significant H/D exchange (25% D for 1a, and 59%
phenylpivalamides to provide the cross-coupled products in D for 2a; Scheme 3, eqn (4) and (5)). An obvious H/D scrambling for
moderate to high yields. The functional group compatibility was both coupling partners was observed when a mixture of 1a and 2a
testified by the tolerance to fluoro, bromo, chloro, ester, alkoxy, was subjected in the presence of D
methyl and phenyl group (Table 3, 4a-4i). However, N-(3- 2a; Scheme 3, eqn (6)). These results indicated that the C−H
phenylethynyl)phenyl)acetamide (2m) proved to be an ineffective activation processes of both 1a and 2a are reversible. Subsequently,
substrate to react with 1a. N-(Naphthalen-2-yl)acetamide kinetic isotope effect (KIE) experiments were conducted. A KIE value
regioselectively gave a C3-arylated product (Table 3, 4j). Finally, a of 1.25 was observed for the parallel reactions between 1a or [D ]-
2
O (52% D for 1a, and 48% D for
(
5
set of substrates bearing substituents with similar or different 1a with 2a (Scheme 3, eqn (7)), suggesting that the ortho C−H bond
electronic properties were successfully attempted (Table 3, 4k-4o), cleavage of 1a might not be involved in the rate-determining step.
further demonstrating the high efficiency of this unique rhodium In contrast, a KIE value of 2.22 was determined when 1a was
5
catalytic system in the oxidative cross-coupling of electronically reacted with 2a or [D ]-2a (Scheme 3, eqn (8)). This result implied
similar substrates and highlighting the generality of this the C−H activation of 2a might be involved in the rate-determining
methodology in preparing unsymmetric 2,2’-diaminobiaryls.
step.
Table 3. Scope of N-phenylacetamidea,b
NHPiv
RhCl3•3H2O (5 mol%)
AgOTFA (2.5 equiv)
NHPiv
NHAc
NHPiv
RhCl3•3H2O (5.0 mol%)
AgOTFA (3.0 equiv)
+
(1)
NHPiv
H
NHAc
H
R1
Cu(OTFA)2•xH2O (20 mol%)
mesitylene, 140 °C, 24 h
R1
+ R2
AcHN
3a, 69% (1.28 g)
Cu(OTFA)2•xH2O (20 mol%)
mesitylene, 140 °C, 24 h
R2
1
a (7.2 mmol)
2a (6.0 mmol)
AcHN
1
2
4
NHPiv
NH2
1) conc. HCl
NHPiv
NHPiv
NHPiv
NHPiv
MeOH, 70 °C, 20 h
(2)
F
CO2Et
Br
OMe
Cl
2) work-up, K CO
2
3
AcHN
3a
H2N
AcHN
AcHN
AcHN
4c, 66%
AcHN
6a, 88%
4a, 62%
4b, 70%
4d, 64%
NHPiv
NHPiv
NHPiv
NHPiv
NH2
NHPiv
KOH (10 equiv)
1
) conc. HCl, 70 °C, 12 h
O
O
(3)
R
4f, R = OMe, 74%
4g, R = Me, 78%
MeOH
120 °C, 12 h
2) work-up, K2CO3
AcHN
3a
H2N
2
H N
AcHN
OMe
AcHN
4h, R = Ph, 73%
5a, 87%
6a
, 93%
4e, 83%
AcHN
4i, 65%
NHPiv
NHPiv
NHPiv
Scheme 2. Gram-scale reaction and removal of the directing groups.
OMe
OMe
CO2Et
tBu
Cl
H
RhCl3•3H2O (5.0 mol%)
AgOTFA (3.0 equiv)
H/D
H
H
N
N
AcHN
AcHN
4k, 82%
AcHN
2
D O
+
Cu(OTFA)2•xH2O (20 mol%)
mesitylene, 140 °C, 2 h
(4)
O
O
4
j, 82%
4l, 65%
H
(20 equiv)
H/D
1a
[Dn]-1a, 25% D
Ph
H
RhCl3•3H2O (5.0 mol%)
AgOTFA (3.0 equiv)
H/D
H
NHPiv
NHPiv
H
N
NHPiv
N
+
D2O
CO2Et
Cu(OTFA) •xH O (20 mol%)
(5)
O
2
2
O
tBu
(20 equiv)
H
mesitylene, 140 °C, 2 h
H/D
2
a
[Dn]-2a, 59% D
AcHN
AcHN
4n, 72%
AcHN
NHAc
2m, no reaction
4m, 80%
4o, 58%
H
H
H
RhCl3•3H2O (5.0 mol%)
AgOTFA (3.0 equiv)
D2O (20 equiv)
H/D
H
H/D
H
H
N
N
N
N
+
+
(6)
(7)
O
O
O
O
a
H
H
Cu(OTFA)2•xH2O (20 mol%)
mesitylene, 140 °C, 2 h
Reaction was performed with 1 (0.24 mmol, 1.2 equiv), and 2 (0.2
mmol, 1.0 equiv) in mesitylene (0.5 mL) at 140 °C for 24 h under N
atmosphere.
H/D
H/D
[Dn]-2a, 48% D
1
a
2a
n
[D ]-1a, 52% D
2
(1.2 equiv)
b
NHPiv
Isolated
yield.
RhCl3•3H2O (5.0 mol%)
AgOTFA (3.0 equiv)
NHPiv
NHAc
4 4
H /D
H5/D5
+
Cu(OTFA)2•xH2O (20 mol%)
mesitylene, 140 °C
To further illustrate the synthetic utility of this methodology, a
gram-scale trial was performed, affording the target product in 69%
yield (Scheme 2, eqn (1)). Moreover, the directing groups on the
substrates could be simultaneously removed in the presence of HCl
+
AcHN
1
a or [D5]-1a
2a
kH/kD = 1.25
3a or [D4]-3a
NHPiv
RhCl3•3H2O (5.0 mol%)
AgOTFA (3.0 equiv)
NHPiv
NHAc
+
H5/D5
(8)
D4/H4
Cu(OTFA)2•xH2O (20 mol%)
mesitylene, 140 °C
AcHN
(Scheme 2, eqn (2)). As an alternative, the 2,2’-diaminobiphenyl
1
a
2a or [D5]-2a
kH/kD = 2.22
3a or [D4]-3a
could be obtained by a sequential removal of the directing groups
This journal is © The Royal Society of Chemistry 20xx
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Journal Name
Taguchi, A. Inaba, Y. Goto, A. Kikuchi, K. ItohVaienwdArYtic.leTOondlinae,
Scheme 3. Mechanistic study.
Chem. Commun., 2019, 55, 1552.
DOI: 10.1039/C9CC01733J
2
3
4
5
6
(a) S. Guizzetti, M. Benaglia, L. Raimondi and G. Celentano,
Org. Lett., 2007, 9, 1247; (b) H.-W. Zhao, Y.-Y. Yue, H.-L. Li,
X.-Q. Song, Z.-H. Sheng, Z. Yang, W. Meng, Z. Yang, Synlett
2013, 24, 2160; (c) M. Lee, J. R. Lamb, M. J. Sanford, A. M.
LaPointe and G. W. Coates, Chem. Commun., 2018, 54,
Based on the above mechanistic study and previous reports,10
plausible pathway is proposed. Initially, a cationic Rh species is
a
III
3
formed by chloride abstraction of RhCl with AgOTFA in the
1
2998.
presence of Cu(OTFA) ·xH O. Then a reversible directed C–H
2
2
(a) P. Data, P. Pander, M. Okazaki, Y. Takeda, S. Minakata
and A. P. Monkman, Angew. Chem. Int. Ed., 2016, 55, 5739;
activation of N-phenylpivalamide 1a might take place to give a
cyclorhodium intermediate IM1, followed by a second directed
ortho-C−H bond activation of N-phenylacetamide 2a. The resulting
bis-cyclometalted rhodium species IM2 was confirmed by ESI-HRMS
analysis (SI, Section VIII). Subsequently, IM2 undergoes a reductive
elimination to furnish the unsymmetrical 2,2’-diaminobiaryl product
a and release a Rh(I) species. Finally, the Rh(I) species is reoxidized
to a Rh(III) species by Ag(I) to complete the catalytic cycle. At this
stage, the possibility of a catalytic cycle involving C–H metalation of
(
b) D. S. Lee, T. Chatterjee, J. Ban, H. Rhee and E. J. Cho,
ChemistrySelect 2018, 3, 2092; (c) Z.-B. Sun, J.-K. Liu, D.-F
Yuan, Z.-H. Zhao, X.-Z. Zhu, D.-H. Liu, Q. Peng and C.-H. Zhao,
Angew. Chem. Int. Ed., 2019, 58, 4840.
For selected examples, see: (a) C.-L. Li, S.-J. Shieh, S.-C. Lin
and R.-S. Liu, Org. Lett., 2003, 5, 1131; (b) K. L. Chan, M. J.
McKiernan, C. R. Towns and A. B. Holmes, J. Am. Chem. Soc.,
2005, 127, 7662; (c) J. Yang, N. Sun, J. Huang, Q. Li, Q. Peng,
X. Tang, Y. Dong, D. Ma and Z. Li, J. Mater. Chem. C., 2015, 3,
3
2
624.
2
a as the first C–H activation step cannot be ruled out.
(a) T. Chatterjee, G.-b. Roh, M. A. Shoaib, C.-H. Suhl, J. S. Kim,
C.-G. Cho and E. J. Cho, Org. Lett., 2017, 19, 1906; (b) M.
Moustakim, K. Riedel, M. Schuller, A. P. Gehring, O. P.
Monteiro, S. P. Martin, O. Fedorov, J. Heer, D. J. Dixon, J. M.
Elkins, S. Knapp, F. Bracher, P. E. Brennan, Bioorg. Med.
Chem., 2018, 26, 2965;
RhCl3•3H2O
O
AgOTFA, Cu(OTFA)2•xH2O
NH
AgCl
H
N
Ag(I)
RhX3
-
-
X = OTFA, Cl
O
Rh(I)
H
1a
HN
For selected reviews and examples for C−H/C−H cross-
couplings of two (hetero)arenes, see: (a) X. Chen, K. M. Engle,
D.-H. Wang and J.-Q. Yu, Angew. Chem. Int. Ed., 2009, 48,
O
HX
3a
5
094; (b) J. A. Ashenhurst, Chem. Soc. Rev., 2010, 39, 540; (c)
H
N
H
N
C. S. Yeung and V. M. Dong, Chem. Rev., 2011, 111, 1215; (d)
S. H. Cho, J. Y. Kim, J. Kwak and S. Chang, Chem. Soc. Rev.,
2011, 40, 5068; (e) C. Liu, J. Yuan, M. Gao, S. Tang, W. Li, R.
Shi and A. Lei, Chem. Rev., 2015, 115, 12138; (f) H. Deng, H.
Li and L. Wang, Org. Lett., 2016, 18, 3110; (g) Y. Yang, J. Lan
and J. You, Chem. Rev., 2017, 117, 8787.
O
RhIII
III O
Rh
X
IM1
IM2
O
X
X
N
H
H
N
Detected by ESI-HRMS
M-X]+ calcd: 413.0736
[
O
7
L. Schulz, M. Enders, B. Elsler, D. Schollmeyer, K. M. Dyballa,
R. Franke and S. R. Waldvogel, Angew. Chem. Int. Ed., 2017,
HX
found: 413.0730
2a
5
6, 4877.
Scheme 4. Plausible mechanistic pathway.
In summary, we have developed a dual chelation-assisted RhCl
8
9
C. Mei and W. Lu, J. Org. Chem., 2018, 83, 4812.
(a) X.-S. Zhang, Y.-F. Zhang, Z.-W. Li, F.-X. Luo and Z.-J. Shi,
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Suo, J.-L. Niu and M.-P. Song, Angew. Chem. Int. Ed., 2016,
3
-
catalyzed oxidative C–H/C–H cross-coupling reaction between N-
phenylpivalamide and N-phenylacetamide, which provides a facile
and general route to various unsymmetrical 2,2’-diaminobiaryls.
This reaction features broad substrate scope, good functional group
tolerance, low molar ratio of substrates and excellent compatibility
of electronically similar coupling partners. The directing groups of
the resulting 2,2’-diaminobiaryl products could be removed
selectively or simultaneously. These features make this method
highly applicable.
5
5, 13571; (d) C. Zhang, T. Li, L. Wang and Y. Rao, Org. Chem.
Front., 2017, 4, 386; (e) S. Dana, D. Chowdhury, A. Mandal, F.
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2
018, 83, 2582; (g) N. Lv, Z. Chen, Y. Liu, Z. Liu and Y. Zhang,
Org. Lett., 2018, 20, 5845; (h) L. Zhang, L. Zhu, Y. Zhang, Y.
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8
324.
10 Y. Shi, L. Zhang, J. Lan, M. Zhang, F. Zhou, W. Wei and J. You,
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1
1 (a) G. S and X. Li, Acc. Chem. Res., 2015, 48, 1007; (b) J.
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We thank the financial support from the National NSF of China
No 21432005).
(
Conflicts of interest
There are no conflicts to declare.
Notes and references
1
(a) H. Nakatsuka, T. Yamamura, Y. Shuto, S. Tanaka, M.
Yoshimura and M. Kitamura, J. Am. Chem. Soc., 2015, 137,
8
138; (b) H. Suga, M. Yoshiwara, T. Yamaguchi, T. Bando, M.
4
| J. Name., 2012, 00, 1-3
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DOI: 10.1039/C9CC01733J
Table of Contents
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General rhodium-catalyzed oxidative cross-coupling reactions between anilines:
synthesis of unsymmetrical 2,2’-diaminobiaryls
Yang Shi, Jiahui Liu, Yudong Yang* and Jingsong You*
NHAc
RhCl •3H O
AgOTFA
R1
Ar1
3
2
NHAc
H
NHPiv
H
R1 Ar1
+
R2 Ar2
Ar2 R2
Cu(OTFA) •xH O
2
2
PivHN
mesitylene
(1.2 equiv)
•
•
•
Broad substrate scope
Compatibility of electronically similar substrates • Low molar ratio of substrates
Complete regiocontrol
• Cp* ligand free
• Good functional group tolerance
Described herein is a dual chelation-assisted RhCl -catalyzed oxidative C–H/C–H cross-coupling
3
reaction of aniline derivatives, in which the chemo- and regioselective cross-coupling between
electronically similar substrates is achieved.