Nickel-catalyzed cross-coupling of arene-or heteroarenecarbonitriles with aryl-or heteroarylmanganese reagents through C-CN bond activation

Article abstract of DOI:10.1002/adsc.201200369

The nickel-catalyzed cross-coupling reaction of arene- or heteroarenecarbonitriles with aryl- or heteroarylmanganese reagents via C-CN bond activation has been developed. Both electron-rich and electron-deficient nitriles can be employed as the electrophilic substrates. The reaction tolerates a range of functional groups and aromatic heterocycles. Copyright

Full text of DOI:10.1002/adsc.201200369

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DOI: 10.1002/adsc.201200369
Nickel-Catalyzed Cross-Coupling of Arene- or
Heteroarenecarbonitriles with Aryl- or Heteroarylmanganese
À
Reagents through C CN Bond Activation
Ning Liua and Zhong-Xia Wanga,*
a
CAS Key Laboratory of Soft Matter Chemistry and Department of Chemistry, University of Science and Technology of
China, Hefei, Anhui 230026, Peopleꢀs Republic of China
Fax : (+86)-551-360-1592; e-mail: zxwang@ustc.edu.cn
Received: April 27, 2012; Published online: June 5, 2012
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201200369.
À
Abstract: The nickel-catalyzed cross-coupling reac-
of arenecarbonitriles via silicon-assisted C CN bond
cleavage.[10] Knochel et al. found an efficient iron-cat-
alyzed reaction of aroyl cyanides with aryl-Grignard
reagents, forming diaryl ketones in good to excellent
tion of arene- or heteroarenecarbonitriles with aryl-
À
or heteroarylmanganese reagents via C CN bond
activation has been developed. Both electron-rich
and electron-deficient nitriles can be employed as
the electrophilic substrates. The reaction tolerates
a range of functional groups and aromatic heterocy-
cles.
yields.[11] In addition to carbon-carbon bond forming
reactions, aryl cyanides can be converted into C N,
bonds through catalytic
activation of the C CN bonds. We became interested
[8c]
À
[12]
[13]
[14]
À
À
À
C Si, C B and C H
À
À
in the C CN bond activation and transformation of
À
Keywords: catalysis; C CN bond activation; cross-
arenecarbonitriles because (i) functional group trans-
formation is a central issue in organic synthesis. Re-
moval or transformation of the cyano group in an aryl
nitrile is of significance from this viewpoint; (ii) the
coupling; nickel; nitriles; organomanganese re-
agents
À
activation of C CN bonds is challenging due to their
À
low reactivity (BDE of Ph CN is ca. 133 kcal
molÀ1);[15] (iii) the nucleophiles used in the C C cou-
À
Transition metal-catalyzed cross-coupling reactions pling reactions of arenecarbonitriles are still limited.
are powerful tools used to construct new carbon- Herein we report an efficient cross-coupling reaction
carbon bonds in modern organic synthesis.[1] The nu- of arene- or heteroarenecarbonitriles with aryl- or
cleophiles for the cross-couplings are normally heteroarylmanganese reagents.
Grignard reagents, organozinc reagents, organotin re-
The catalysts and solvents were first screened using
agents, organoboron reagents and organosilicon re- the reaction of 3-methoxybenzonitrile with p-
agents. Relatively recently, organomanganese re- MeC6H4MnCl (Table 1). A series of nickel, palladium
agents were used as a nucleophilic partner in some and cobalt complexes bearing phosphine ligands such
cross-coupling reactions.[2] Electrophiles used in the as PCy3, PEt3, PMe3 and Ph2POH was used as the cat-
reactions include organic halides,[3] aryl-oxygen deriv- alyst precursor. It was found Ni
ACHTUNGTRENNUNG
atives (triflates, mesylates, tosylates[4] and carboxy- to Ni
ACTHNGUTREN(NUNG PCy3)2Cl2 and NiACTHUNGTRENNUNG
lates[5]) and aryl-nitrogen derivatives (diazonium 3). 10 mol% of the former could lead to a 98% prod-
salts[6] and aryltrimethylammonium salts[7]). In 2001 uct yield in THF at room temperature. Further ex-
Miller et al. disclosed several nickel-catalyzed cross- periments proved that 5 mol% of NiACHTNUGTRNEG(UN PMe3)2Cl2 af-
coupling reactions of arenecarbonitriles with aryl-, al- forded a very similar product yield (Table 1, entry 4).
kenyl- and alkyl-Grignard reagents or alkynylzinc re- In these reactions, p-MeC6H4MnCl was prepared
[8]
À
agents through C CN bond cleavage. In the former from p-MeC6H4Li and Li2MnCl4. If p-MeC6H4MnCl
case the addition of t-BuOLi or PhSLi was required was prepared from p-MeC6H4MgBr, a lower cross-
to suppress the nucleophilic addition of the organo- coupling yield was observed (Table 1, entry 5). It
magnesium reagent to the nitrile group. Shi et al. re- seems that Mg2+ has a negative effect in this reaction.
ported the cross-coupling of arenecarbonitriles and ar- 2.5 equivalents of p-MeC6H4MnCl are necessary for
ylboronic esters catalyzed by Ni
et al. carried out the rhodium-catalyzed alkenylation ylmanganese reagent resulting in lower product yields
(PCy3)2Cl2.[9] Chatani the reaction to go to completion, lower amounts of ar-
ACHTUNGTRENNUNG
Adv. Synth. Catal. 2012, 354, 1641 – 1645
ꢁ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1641

Ning Liu and Zhong-Xia Wang
COMMUNICATIONS
Table 1. Screening of catalysts and solvents.[a]
conditions as those of entry 4 in Table 1 (Table 1,
entry 16).
We next examined the scope of arene- and hetero-
arenecarbonitriles in THF using p-MeC6H4MnCl as
a
nucleophile and Ni
(PMe3)2Cl2 as
a
catalyst
(Table 2). Both benzonitrile and 2-naphalenecarboni-
trile exhibited good reactivity and their reactions gave
excellent product yields at 258C with a 5 mol% of cat-
alyst loading (Table 2, entries 1 and 2). 4-Methoxy-
benzonitrile showed a lower reactivity than 3-meth-
Entry Catalyst
Solvent
Yield[f]
[%]
1
2
3
Ni
Ni
Ni
Ni
Ni
Ni
Ni
Ni
Ni
N
THF
THF
THF
THF
THF
THF
THF
19
40
98
96
88
92
91
47
AHCTUNGTRENNUNG
4[b]
5[c]
6[d]
7
AHCTUNGTRENNUNG
ed reaction temperatures or prolonged reaction times
(Table 2, entries 3 and 4). It was also noted that at
708C the reaction of 4-methoxybenzonitrile afforded
the homocoupling product of 4-methoxybenzonitrile,
4,4’-dimethoxybiphenyl, in 12% yield besides the
cross-coupling product. The reaction of 3,4-dimeth-
8
9
THF
76
10
11
12
13
Pd
Pd
Co
G
THF
THF
THF
THF-MTBE
(1:1)
THF-NMP (1:1) 24
toluene
THF
trace
trace
22
E
AHCTUNGTREGoNNUN xybenzonitrile gave a slightly higher yield than that
R
of 4-methoxybenzonitrile, whereas the reaction 4-(di-
methylamino)benzonitrile afforded an excellent result
at 708C (Table 2, entries 5 and 6). Electron-deficient
arenecarbonitriles, including ethyl 4-cyanobenzoate,
4-cyano-N,N-dimethylbenzamide, 4-fluorobenzonitrile
and 4-(trifluoromethyl)benzonitrile, displayed higher
reactivity than electron-rich ones.
Their reactions with p-MeC6H4MnCl could proceed
at room temperature with a 5 mol% catalyst loading,
giving 86–96% product yields (Table 2, entries 7–10).
In these reactions, functional groups such as F, CF3,
COOEt and C(O)NEt2 can be tolerated. Attempts to
Ni
A
94
14
15
Ni
Ni
U
45
96
16[b,e] Ni
R
[a]
Unless otherwise specified, the reactions were carried
out on a 0.5 mmol scale according to the conditions indi-
cated by the above equation and p-MeC6H4MnCl was
prepared from p-MeC6H4Li and Li2MnCl4; 2.5 equiv. of
p-MeC6H4MnCl were employed.
5 mol% catalyst was employed.
p-MeC6H4MnCl was prepared from p-MeC6H4MgBr and
Li2MnCl4.
[b]
[c]
perform
the
catalytic
reactions
using
p-
[d]
[e]
[f]
2 equiv. of p-MeC6H4MnCl were employed.
5 mmol m-MeOC6H4CN were employed.
Yields of isolated products.
RC(O)C6H4CN (R=H, Me, Ph) and p-O2NC6H4CN
as the electrophiles were unsuccessful. Reaction of p-
CHOC6H4CN with p-MeC6H4MnCl generated an ad-
ditional product of the formyl group; whereas
(Table 1, entry 6). Ni
lower yield than Ni(PMe3)2Cl2 under the same condi- not react with an arylmanganese reagent under the
tions, whereas Ni(acac)2/2Ph2POH led to a much standard catalytic conditions. Heteroarenecarboni-
lower yield (Table 1, entries 7 and 8). Somewhat sur- triles reacted smoothly with p-MeC6H4MnCl under
prisingly, Ni(COD)2/2PMe3 was not as effective as Ni- appropriate conditions. Reaction of both 3- and 4-cya-
(PMe3)2Cl2 for this transformation (Table 1, entry 9). nopyridines with p-MeC6H4MnCl in THF at room
ACTHGNUERTN(NGNU acac)2/2PMe3 afforded a slightly RC(O)C6H4CN (R=Me, Ph) and p-O2NC6H4CN did
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
Palladium and cobalt complexes showed less activity temperature gave excellent product yields with
than the nickel complexes tested. A combination of a 10 mol% catalyst loading (Table 2, entries 11 and
either Pd
only a trace amount of product (Table 1, entries 10 as electrophilic partner led to relatively low yield.
and 11). Co(acac)3/2PMe3 is not an effective catalyst Further studies showed that at 708C and in a mixed
ACHTUNGTRENNUNG(OAc)2 or Pd2ACHTUNTGRNEN(UGN dba)3 and PMe3 resulted in 12). However, similar reaction using 2-cyanopyridine
ACHTUNGTRENNUNG
for this reaction. It led to only 22% product yield solvent of THF and NMP (1:1) the reaction afforded
under the standard conditions (Table 1, entry 12). Sol- an almost quantitative yield (Table 2, entries 13 and
vent effects were also tested. The reaction in a 1:1 14). The improved reaction conditions are also appli-
mixture of THF and methyl tert-butyl ether (MTBE) cable to the reaction of 2-cyanoquinoline and pyrimi-
gave a yield close to that in THF, whereas use of tolu- dine-2-carbonitrile, which gave 99% and 92% yields,
ene or a mixed solvent of THF and NMP (1:1) result- respectively (Table 2, entries 15 and 16).
ed in much poorer results (Table 1, entries 13–15). In
The scope of the manganese reagents was also
addition, the reaction using a 5-mmol scale of 3-me- tested, including electron-rich and electron-deficient
thoxybenzonitrile gave a similar yield under the same arylmanganese chlorides as well as heteroarylmanga-
1642
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ꢁ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2012, 354, 1641 – 1645

Nickel-Catalyzed Cross-Coupling of Arene- or Heteroarenecarbonitriles
Table 2. Nickel-catalyzed coupling of arene- or heteroarene-
carbonitriles with p-MeC6H4MnCl.[a]
all other aryl- and heteroarylmanganese reagents
were prepared from the corresponding organolithium
reagents and Li2MnCl4. Reaction of p-MeOC6H4MnCl
or p-Me2NC6H4MnCl with PhCN in THF at 708C
using 10 mol% NiACTHNUTRGNEUNG(PMe3)2Cl2 as a catalyst afforded
the corresponding cross-coupling products in 67%
and 82% yields, respectively. Reaction of p-
Me2NC6H4MnCl with m-MeOC6H4CN under the
same conditions gave the desired product in 72%
yield (Table 3, entries 1–3). Usually an electron-rich
nucleophilic reagent should behave with stronger nu-
cleophilicity. However, the above results showed that
the reactivity of p-MeOC6H4MnCl and p-
Me2NC6H4MnCl was lower than that of p-
MeC6H4MnCl. A supposed reason is the coordination
of the oxygen atom of p-MeOC6H4MnCl or the nitro-
gen atom of p-Me2NC6H4MnCl to a metal center
(e.g., magnesium, lithium or manganese ion), which
decreases the nucleophilicity of the aryl anions. The
electron-deficient p-CF3C6H4MnCl is less reactive
than p-MeC6H4MnCl as expected. Reaction of p-
Entry ArCN
Catalyst loading Yield[e] [%]
1
2
5 mol%
5 mol%
90
93
3[b]
4[c]
10 mol%
10 mol%
77
75
5[b]
10 mol%
80
6[c]
7
10 mol%
5 mol%
89
96
CF3C6H4MnCl
with
p-EtO2CC6H4CN
or m-
MeOC6H4CN resulted in 63% and 76% yields, respec-
tively (Table 3, entries 4 and 5). The catalytic reaction
is sensitive to steric hindrance of the arylmanganese
reagents. Reaction of o-MeC6H4MnCl with p-(t-
BuO2C)C6H4CN afforded only 51% yield of cross-
coupling product. Heteroarylmanganese reagents are
applicable to the cross-coupling. Reaction of 2-furyl-
manganese chloride with 2-naphthalenecarbonitrile,
p-EtO2CC6H4CN or m-MeOC6H4CN gave the corre-
sponding products in 77–92% yields (Table 3, en-
tries 7–9). In the reactions, 2-naphthalenecarbonitrile
exhibited the highest reactivity; whereas the reaction
of p-EtO2CC6H4CN led to the lowest yield for as yet
unclear reasons. These results also showed that elec-
tron-rich 2-furylmanganese chloride is less reactive
than p-MeC6H4MnCl. This may be due to the same
8
5 mol%
87
9
5 mol%
5 mol%
86
92
10
11
12
13
10 mol%
10 mol%
10 mol%
89
86
53
14[c,d]
15[c,d]
10 mol%
10 mol%
10 mol%
99
99
92
reason
as
for
p-MeOC6H4MnCl
and
p-
Me2NC6H4MnCl. Thus, the coordination of the
oxygen atom of the furyl group to a metal ion like Li+
and Mn2+ decreases the nucleophilicity of the 2-furyl
anion. 2-Thienylmanganese chloride showed higher
reactivity than 2-furylmanganese chloride. Its reaction
with both activated and deactivated arenecarboni-
triles gave excellent results (Table 3, entries 10–13). It
was also proven through reaction of 2-naphthalene-
carbonitrile and 2-thienylmanganese chloride that the
reaction can tolerate larger amounts of substrates
without a reduction of yield (Table 3, entry 14). Ben-
zothien-2-ylmanganese chloride can also be used as
a nucleophile in the transformation. Its reaction with
PhCN or 3,4-(MeO)2C6H3CN gave the corresponding
16[c,d]
[a]
The reactions were carried out on a 0.5-mmol scale ac-
cording to the conditions indicated by the above equa-
tion unless otherwise specified; 2.5 equiv. of p-
MeC6H4MnCl were employed; p-MeC6H4MnCl was pre-
pared from p-MeC6H4Li and Li2MnCl4.
Reaction was run for 24 h.
Reaction was carried out at 708C.
Reaction was run in a mixed solvent of THF and NMP
(1:1).
[b]
[c]
[d]
[e]
Yields of isolated products.
nese chlorides. The electron-rich manganese reagents, cross-coupling products in 91% and 84% yields, re-
p-MeOC6H4MnCl and p-Me2NC6H4MnCl, were pre- spectively (Table 3, entries 15 and 16). The reaction
pared from the corresponding Grignard reagents and activity is approximately comparable to that of p-
Li2MnCl4, which gave better coupling results; whereas MeC6H4MnCl.
Adv. Synth. Catal. 2012, 354, 1641 – 1645
ꢁ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
1643

Ning Liu and Zhong-Xia Wang
COMMUNICATIONS
Table 3. Nickel-catalyzed coupling of arenecarbonitriles with
coupling of arene- or heteroarenecarbonitriles and
aryl- or heteroarylmanganese reagents. The cross-cou-
pling can be carried out under mild conditions, does
not require any additives, displays a broad substrate
scope and tolerates functional groups such as ester,
amide, trifluoromethyl, fluoride, methyloxy, and dime-
thylamino groups and aromatic heterocycles.
aryl- or heteroarylmanganese reagents.[a]
Entry ArMnCl
Arenecarbonitrile
Yield[d] [%]
1[b]
2[b]
67
82
Experimental Section
Typical Procedure (Table 1, entry 4)
3[b]
4
72
63
76
A Schlenk tube was charged with NiACTHUNRGTNEG(UN PMe3)2Cl2 (7.0 mg,
0.025 mmol), 3-methoxybenzonitrile (0.0675 g, 0.5 mmol)
and THF (0.5 mL). To the solution was added dropwise a so-
lution of p-MeC6H4MnCl (2.5 mL, 0.5M in THF, 1.25 mmol)
at 258C with stirring. After stirring at this temperature for
12 h, water (10 mL) and several drops of acetic acid were
successively added. The resulting mixture was extracted
with Et2O (3ꢂ10 mL). The extract was dried over Na2SO4,
filtered and concentrated by rotary evaporation. The residue
was purified by column chromatography (silica gel, eluted
using petroleum ether) to afford 3-methoxy-4’-methylbi-
phenyl; yield: 0.095 g (96%).
5
6
51
7
8
92
77
9
80
95
94
Acknowledgements
We gratefully acknowledge financial support by the National
Natural Science Foundation of China (grant no. 21172208)
and National Basic Research Program of China (grant no.
2009CB825300).
10
11
12
87
95
98
91
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