CuI-Catalyzed intramolecular aminocyanation of terminal alkynes in N-(2-ethynylphenyl)-N-sulfonylcyanamides via Cu-vinylidene intermediates

Article abstract of DOI:10.1039/c6cc08601b

CuI-Catalyzed intramolecular aminocyanation of terminal alkynes in N-(2-ethynylphenyl)-N-sulfonylcyanamides was initiated by the formation of Cu-acetylide to trigger N-CN bond cleavage of the N-sulfonylcyanamide moiety followed by CN migration to form a β-cyano Cu-vinylidene intermediate. Subsequently, the indole ring closure furnished the corresponding 1-sulfonyl-3-cyanoindoles.

Full text of DOI:10.1039/c6cc08601b

View Article Online
View Journal
ChemComm
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: Z. Liao, P. Liao
and T. Chien, Chem. Commun., 2016, DOI: 10.1039/C6CC08601B.
This is an Accepted Manuscript, which has been through the
Volume 52 Number
1 4 January 2016 Pages 1–216
Royal Society of Chemistry peer review process and has been
accepted for publication.
ChemComm
Accepted Manuscripts are published online shortly after
Chemical Communications
www.rsc.org/chemcomm
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1359-7345
COMMUNICATION
Marilyn M. Olmstead, Alan L. Balch, Josep M. Poblet, Luis Echegoyenet al.
Reactivity differences of Sc3N@C2n (2n 68 and 80). Synthesis of the
first methanofullerene derivatives of Sc N@D5h-C80
=
3
rsc.li/chemcomm

Please do not adjust margins
ChemComm
Page 1 of 4
View Article Online
DOI: 10.1039/C6CC08601B
Journal Name
COMMUNICATION
CuI-catalyzed Intramolecular Aminocyanation of Terminal Alkynes
in N-(2-Ethynylphenyl)-N-sulfonylcyanamides via Cu-vinylidene
Intermediates
Received 00th January 20xx,
Accepted 00th January 20xx
Zhen-Yuan Liao, Pen-Yuan Liao and Tun-Cheng Chien*
DOI: 10.1039/x0xx00000x
www.rsc.org/
CuI-catalyzed Intramolecular aminocyanation of terminal alkynes achieved by the reaction with NCTS (1) and (Bpin)2 under Cu(I)
in N-(2-ethynylphenyl)-N-sulfonylcyanamides was initiated by the catalysis. The vinyl group played the role of a directing group
formation of Cu-acetylide to trigger N-CN bond cleavage of the N- for the ortho-C(sp2)-H cyanation and itself was simultaneously
sulfonylcyanamide moiety followed by CN migration to form β- hydroborated.13,14 Montgomery further adopted a similar
cyano Cu-vinylidene intermediate. Subsequently, the indole ring reaction protocol for a cascade C(sp2)-cyanation/diborylation
closure furnished the corresponding 1-sulfonyl-3-cyanoindoles.
of terminal allenes (Scheme 1 (A)).15
(A) Buchwald (2014), Yang (2014 & 2016), Montgomery (2015, 2016):
Cyanamide derivatives have been extensively used as
reactive N-C-N building blocks in organic synthesis,1 and as
ambidentate ligands in coordination chemistry.2 Recently, the
B(Pin)
R1
R1
Cu(I) catalyst
CN
B2Pin2
Ts
N
1
H
CN
+
use of N-cyano-N-phenyl-p-toluenesulfonamide (NCTS, 1) and
B(pin)
Ph
R1
B(Pin)
its derivatives as organic cyanating reagents has received
considerable attention, of which the N-CN bond cleavage
provided reactive CN species for expeditious synthesis of a
variety of cyano-containing organic molecules.3
R1
.
CN
(B) Wang (2013):
R2
R2
H
Rh(I) catalyst
R1
CN
N
R1
NCTS
(1) can react with various nucleophiles or
CN
organometallic reagents to form the corresponding X-CN
bonds (X = C, N or O), including: (1) organozinc reagents,4 aryl
halides5 or aryl/vinyl boronic acids6 under transition-metal
NH
Ts
Ts
(C) Douglas (2014), Nakao (2014), Shi (2016):
R2
.
catalysis; (2) π-electron rich (hetero)arenes with BF3 OEt2;7 and
R = Ac:
CN
R2
Pd catalyst
with BR3
(3) Grignard reagents,8 boron enolates,9 or deprotonated X-H
n
R4
n
R2
O
R1
R1
R1
nucleophiles (X = N or O).10 NCTS (
1) was also used as the CN
R3
CN
or
N
R
N
Me
N
R
R = Ts:
CN
source for direct cyanation of (hetero)arenes or alkenes via
the transition-metal catalyzed C(sp2)-H bond activation in the
presence of miscellaneous neighboring directing groups.11
Zeng reported that ortho-aminobenzonitriles were obtained by
aminocyanation of arynes through the direct addition of N-
arylcyanamides, which is an exception for the N-CN bond
dissociation of cyanamides that did not possess electron-
withdrawing substituents.12
R = Ac, R2 = aryl
R3,R4 = cyclopropyl
n = 0
B(C6F5)3
R = Ac or Ts
R3 = R4 = H, n = 1~2
(D) This work:
H
CN
cat. CuI
C
C
Na2CO3
R1
R1
H
CN
1,4-dioxane
80 oC, 3 h, Ar
N
N
SO2R2
SO2R2
Scheme 1. Reactions of unsaturated C-C bonds with NCTS (1) or its derivatives
The intermolecular reactions of NCTS (1) with unsaturated
C-C bonds have also been studied. Buchwald and Yang
demonstrated that bis-functionalization of vinylarenes was
Our attention was attracted by the intramolecular CN
migration reaction of ortho-alkenyl substituted NCTS
derivatives, wherein the NCTS portion served as an internal
cyano donor for intramolecular cyanation of alkenes. Wang
found that the Rh(I)-catalyzed reactions of ortho-vinyl
substituted NCTS derivatives resulted in the intramolecular
alkene-cyanation (Scheme 1 (B)).16 Douglas,17 Nakao18 and
Shi,19 independently reported that ortho-allyl or homoallyl
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 2 of 4
View Article Online
DOI: 10.1039/C6CC08601B
COMMUNICATION
substituted NCTS derivatives or the N-acyl-N-phenylcyanamide cyanoindole24
Journal Name
(
10a) as the product, contrast to the 1-cyano-2-
congeners underwent intramolecular aminocyanation in the phenylindole25
(9) obtained from the phenylethynyl derivative
presence of boranes as activators, in which the N-CN bond 6a
dissociation took place accompanied by the simultaneous
addition of the N-CN bond to alkenes (Scheme 1 (C)).
.
R
N
H
CN
H
C
C
C
CuI (10 mol%)
The above mentioned works indicated that Lewis acid or
transition metal promoted N-CN bond cleavage of NCTS
derivatives is an effective approach to provide reactive CN
species for versatile cyanation applications. Nevertheless, the
present C-CN bond formation with NCTS derivatives was
limited only to sp2-hybridized carbon centers.3 The inter- and
R
R
CN
Et3N / DMF
(1 : 1, 0.2 M)
80oC, 3 h
N
N
N
N
CN
Ts
Ts
Ts
9
10
11
6a
7a
8a
R = Ph
TMS
reactant
6a R = Ph
product(s) obtained from the reaction
48% (9) not observed -----
7a R = TMS not observed 53% (10a, R = H) not observed
8a R = H not observed 52% (10a) not observed
H
intramolecular reactions of NCTS-derived cyanating reagents Scheme 3. Reactions of N-(2-alkynylphenyl)-N-tosylcyanamides (6a-8a) under literature
condition
with sp-hybridized carbon centers still remain unexploited.
The formation of 10a has particularly attracted our
attention, in which the formal cleavage of the N-CN bond took
place accompanied with intramolecular aminocyanation of the
alkyne to furnish the 3-cyanoindole skeleton. It is noteworthy
that the regiochemistry of our intramolecular aminocyanation
of the alkyne is contrary to the intramolecular aminocyanation
or cyanation of alkenes16-19
further examine the reaction details.
Various conditions for the reaction of 8a
(Scheme 1) and prompted us to
,
including
Scheme 2. Literature-reported reactions
different bases, metal salts, ligands/additives, solvents, and
temperature, were screened in order to optimize the
formation of 10a. The maximal yield was obtained when the
reaction was carried out in 1,4-dioxane with CuI as the
catalyst, and Na2CO3 as the base under argon at 80 oC, and the
reaction could be completed within 3 hours. The CuI-catalyzed
aminocyanation ring closure of 8a afforded exclusively 1-tosyl-
3-cyanoindole (10a) in an excellent yield. The survey of the
conditions also concluded that both Cu catalyst and base are
required, and reaction yields were presumably the same in
open air and under an argon atmosphere.
Literature survey revealed that the reactions of N-(2-
alkynylphenyl)cyanamide derivatives have rarely been studied.
Yamamoto reported that CuI-catalyzed reaction of N-(2-(2-
(trimethylsilyl)ethynyl)phenyl)cyanamide
(
2
)
gave
2-
trimethylsilyl-1-cyanoindole (
reaction of
(trimethylsilyl)ethynyl)phenyl)cyanamide (
catalysis afforded 3-allyl-2-trimethylsilyl-1-cyanoindole (
52% yield (Scheme 2).21 Both reactions resulted in the N-
cyanoindole derivatives, which showed that the N-CN bond
without an electron-withdrawing group is substantially stable
under catalytic conditions. Even in the presence of an electron-
withdrawing group, Saá demonstrated that N-(2-
3
) in 76% yield.20 In addition, the
N-allyl-N-(2-(2-
4
) under Pd(PPh3)4
5
) in
(phenylethynyl)phenyl)-N-tosylcyanamide
(6a) is thermally
stable at 150 oC and distinctive from the corresponding
ynamide analogs that can undergo thermal cyclization to form
benzo[b]carbazole.22 Therefore, we were prompted to
investigate the unexploited reactivity whether the N-CN bond
cleavage followed by intramolecular electrophilic cyanation of
N-(2-ethynylphenyl)-N-sulfonylcyanamides could be achieved
under catalytic condition.
Scheme 4. Reaction of N-substituted N-(2-ethynylphenyl)cyanamides (12a-j)
Subsequently, a series of N-(2-ethynylphenyl)cyanamides
The N-phenylcyanamide derivatives used in our study were
prepared by three different approaches, including dehydration
of N-phenylureas by sulfonyl chlorides,8 direct cyanation of N-
sulfonylanilines with BrCN,17,22 and Tiemann rearrangement of
benzamidoximes.23 In our initial trials, N-(2-alkynylphenyl)-N-
(
12a-j) with different substituents at cyanamide were
subjected to the optimized condition to screen for suitable N-
substituents which could promote the N-CN bond cleavage
and CN migration. 1-Cyanoindole25
(
14) was the only product
isolated from the reaction of N-(2-ethynylphenyl)cyanamide
12a), which confirmed that cleavage of the unsubstituted N-
tosylcyanamides (6a, 7a and 8a) were first subjected to
(
Yamamoto’s CuI and Pd(PPh3)4 conditions to explore the
reaction outcomes. While the reactions of 6a-8a did not
proceed with Pd(PPh3)4, the reactions with CuI gave two
different results, as shown in Scheme 3. Both the terminal and
CN bond cannot be achieved under CuI catalysis. The survey of
the substituent effects showed that only the sulfonyl groups
can proceed to the intramolecular aminocyanation to afford 1-
sulfonyl-3-cyanoindole derivatives (13f-j) in good yields, while
TMS-ethynyl derivatives
(8a and 7a) afforded 1-tosyl-3-
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 3 of 4
View Article Online
DOI: 10.1039/C6CC08601B
Journal Name
COMMUNICATION
N-methyl-
and
N-acyl-substituted
N-(2- trans-aminometalation across the alkyne followed by
via the
intermediacy of 1-tosylindol-3-yl cyano-copper complex (A-III
ethynylphenyl)cyanamides (12b-e) gave no desired products cyanation to give 1-tosyl-3-cyanoindoles
(P)
but complicated results (Scheme 4).
)
(
mechanism A in Scheme 6).
(A)
standard
condition
R
no reaction
recovered:
CN
N
Ts
6a
6b
7a
16
C
C
C
C
C
C
Ph
(CH2)5CH3
TMS
6a
6b
7a
16
R =
(94%)
(89%)
(93%)
(85%)
HC CH2
(B)
H
C
standard
condition
C
Ts
N
C
C C C
+
Ph
CN
Scheme 5. Reaction of N-(2-ethynylphenyl)-N-tosylcyanamides 8a-p
17
1
(4 equiv)
18
1
(82%), recovered: (95%)
(C)
R
C
standard
condition
Meanwhile,
a
variety
8a-p
of
N-tosyl-N-(2-
C
Ts
N
R
N
ethynylphenyl)cyanamides
(
)
were subjected to the
+
Ph
CN
NH
Ts
R = H
optimized condition to explore the scope and generality of the
intramolecular aminocyanation reaction. Our investigation
1
(4 equiv)
Ts
19
21
22
1
1
R = H 77%, recovered: (92%)
R = Ph 72%, recovered: (95%)
20
Ph
showed that the reactions of all the substrates
(8a-p)
(D)
proceeded flawlessly under the optimized condition to form
the corresponding 1-tosyl-3-cyanoindole derivatives (10a-p) in
good yields (Scheme 5).
H
CN
CN
C
standard
condition
C
H
+
CN
Br
N
N
N
(2 equiv)
Ts
(28%)
Ts
8a Ts
23
10a
(39%)
standard condition
Br
(2 equiv)
Scheme 7. Control experiments
A series of control experiments were conducted in order to
gain insight into the mechanistic details. ortho-Vinyl- and
internal alkynyl-tethered NCTS derivatives (16, 6a-b and 7a)
were first subjected to the standard condition to explore the
limitation of the unsaturated C-C components. The results
indicated that the intramolecular aminocyanation of alkenes
or internal alkynes did not take place under CuI catalysis
(
Scheme 7 (A)).
In an effort to investigate whether the intermolecular
aminocyanation or cyanation of phenylacetylenes could occur,
an excess amount of NCTS ( ) was used as an external CN
source to react with phenylacetylene 17) or N-tosyl-2-
1
(
alkynylanilines (19 and 20) under the standard condition. The
reaction of phenylacetylene gave only the homocoupling
adduct 18 and intact NCTS (
reactions of N-tosyl-2-ethynylanilines (19 and 20) afforded
exclusively the corresponding 1-tosylindoles 21 and 22
respectively) and the recovered NCTS ( ) (Scheme 7 (B)(C)).
The results revealed that NCTS ( ) is stable under the standard
condition and the subsequent electrophilic addition of cyano
group to phenylacetylenes was infeasible. As result,
mechanism A Scheme 6) was negligible since it failed to
1) was recovered, while the
Scheme 6. Proposed mechanism
(
,
A tentative mechanism was first sketched in accordance to
the conventional 3-substituted indole formation from 2-
alkynylaniline derivatives via indol-3-yl metal intermediates
1
1
(
mechanism A in Scheme 6).26 The reaction was proposed to
a
start with the formation of substrate-copper complex (A-I) by
π-coordination of alkyne and nitrile moieties to the copper
center. Subsequently, the heterolytic cleavage of N-CN bond
accompanied by migration of the electrophilic cyano group to
the copper center resulted in the N-tosyl-2-alkynylanilide
cyano-copper complex A-II. Intermediate A-II then underwent
(
account for the fact that the intramolecular aminocyanation
reaction is only applicable to terminal alkynes and the
heterolytic cleavage of N-CN bond of NCTS derivatives cannot
be triggered under copper catalysis.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 4 of 4
View Article Online
DOI: 10.1039/C6CC08601B
COMMUNICATION
Journal Name
10 V. Narayana Murthy, S. P. Nikumbh, S. Praveen Kumar, L.
,
Notably, only terminal alkynes underwent the
intramolecular aminocyanation reaction, which led to the
assumption that the formation of Cu-acetylide complex plays a
key role in the reaction. In an attempt to trap the transient
indolyl-Cu complex, the addition of allyl bromide to the
reaction of 8a under the standard condition was carried out.
The reaction afforded the aminocyanation adduct 10a
accompanied with 1-tosyl-2-allyl-3-cyanoindole (23). Since 23
cannot be obtained from the reaction of 10a under the same
condition, the result suggested that 1-tosylindol-2-yl-Cu
complex (B-III) was formed in the reaction (Scheme 7 (D)).
On the basis of the control experiments, the plausible
mechanism was proposed to start with the formation of Cu-
acetylide B-I with the increase of π-electron density at the β-
carbon. Intramolecular nucleophilic attack of the β-carbon to
the electrophilic cyanamide carbon accompanied with the N-
CN bond cleavage resulted in the β-cyano Cu-vinylidene
Vaikunta Rao and A. Raghunadh, Tetrahedron Lett., 2015, 56
5767-5770.
11 (a) A. Mishra, T. K. Vats and I. Deb, J. Org. Chem., 2016, 81
,
6525-6534; (b) J. Li and L. Ackermann, Angew. Chem. Int. Ed.,
2015, 54, 3635-3638; (c) J. Dong, Z. Wu, Z. Liu, P. Liu and P.
Sun, J. Org. Chem., 2015, 80, 12588-12593; (d) J. Jia, X. Liu, J.
Shi, H. E. Xu and W. Yi, Asian J. Org. Chem., 2015, 4, 1250-
1253; (e) M. Chaitanya and P. Anbarasan, Org. Lett., 2015,
17, 3766-3769; (f) W. Su, T.-J. Gong, B. Xiao and Y. Fu, Chem.
Commun., 2015, 51, 11848-11851; (g) N. K. Mishra, T. Jeong,
S. Sharma, Y. Shin, S. Han, J. Park, J. S. Oh, J. H. Kwak, Y. H.
Jung and I. S. Kim, Adv. Synth. Catal., 2015, 357, 1293-1298;
(h) M. Chaitanya and P. Anbarasan, J. Org. Chem., 2015, 80
,
3695-3700; (i) D.-G. Yu, T. Gensch, F. de Azambuja, S.
Vasquez-Cespedes and F. Glorius, J. Am. Chem. Soc., 2014,
136, 17722-17725; (j) J. Han, C. Pan, X. Jia and C. Zhu, Org.
Biomol. Chem., 2014, 12, 8603-8606; (k) L.-J. Gu, C. Jin, R.
Wang and H.-Y. Ding, ChemCatChem, 2014, 6, 1225-1228; (l)
W. Liu and L. Ackermann, Chem. Commun., 2014, 50, 1878-
1881; (m) M. Chaitanya, D. Yadagiri and P. Anbarasan, Org.
Lett., 2013, 15, 4960-4963; (n) T.-J. Gong, B. Xiao, W.-M.
Cheng, W. Su, J. Xu, Z.-J. Liu, L. Liu and Y. Fu, J. Am. Chem.
Soc., 2013, 135, 10630-10633.
complex B-II 27
Subsequent intramolecular nucleophilic attack
.
of the remaining tosylamide at the α-carbon of the Cu-
vinylidene complex (B-II) afforded 1-tosylindol-2-yl-Cu complex
B-III. Protonation of B-III furnished the product 10a and
regained the Cu(I) catalyst to continue the catalytic cycle
12 B. Rao and X. Zeng, Org. Lett., 2014, 16, 314-317.
13 (a) Y. Yang, Angew. Chem. Int. Ed., 2016, 55, 345-349; (b) Y.
Yang and S. L. Buchwald, Angew. Chem. Int. Ed., 2014, 53
8677-8681.
,
(mechanism B in Scheme 6).
In summary, we disclosed the CuI-catalyzed intramolecular
14 W. Zhao and J. Montgomery, Angew. Chem. Int. Ed., 2015,
54, 12683-12686.
aminocyanation of ortho-(N-tosyl-N-cyanoamino)-substituted
phenylacetylene derivatives. The mechanistic investigation
suggested that the transformation proceeded through a
cyanation-amination sequence involving both Cu-acetylide and
Cu-vinylidene intermediates to account for the regiochemical
course. The N-CN bond cleavage was triggered solely by the
neighboring Cu-acetylide, which enlightens that the
intramolecular β-electrophilic addition of Cu-acetylide complex
would be feasible for further synthetic applications.
15 W. Zhao and J. Montgomery, J. Am. Chem. Soc., 2016, 138
9763-9766.
,
16 R. Wang and J. R. Falck, Chem. Commun., 2013, 49, 6516-
6518.
17 Z. Pan, S. M. Pound, N. R. Rondla and C. J. Douglas, Angew.
Chem. Int. Ed., 2014, 53, 5170-5174.
18 Y. Miyazaki, N. Ohta, K. Semba and Y. Nakao, J. Am. Chem.
Soc., 2014, 136, 3732-3735.
19 Y.-C. Yuan, H.-B. Yang, X.-Y. Tang, Y. Wei and M. Shi, Chem.
Eur. J., 2016, 22, 5146-5150.
This work was supported by Research Grants 104-2113-M-
003-001- and 105-2113-M-003-003- from Ministry of Science
and Technology, Taiwan. We also thank Professor Ming-Chang
P. Yeh (National Taiwan Normal University, NTNU) for his
helpful discussion and Mr. Ting-Shen Kuo (NTNU) for his
assistance with X-ray crystallographic analysis.
20 S. Kamijo, T. Jin and Y. Yamamoto, Angew. Chem. Int. Ed.,
2002, 41, 1780-1782.
21 S. Kamijo and Y. Yamamoto, J. Am. Chem. Soc., 2002, 124
11940-11945.
,
22 (a) M. F. Martinez-Esperon, D. Rodriguez, L. Castedo and C.
Saá, Tetrahedron, 2006, 62, 3843-3855; (b) M. F. Martinez-
Esperon, D. Rodriguez, L. Castedo and C. Saá, Org. Lett.,
2005, 7, 2213-2216.
23 C.-C. Lin, T.-H. Hsieh, P.-Y. Liao, Z.-Y. Liao, C.-W. Chang, Y.-C.
Shih, W.-H. Yeh and T.-C. Chien, Org. Lett., 2014, 16, 892-895.
24 (a) K. Okamoto, M. Watanabe, M. Murai, R. Hatano and K.
Ohe, Chem. Commun., 2012, 48, 3127-3129; (b) H. Shimojo,
K. Moriyama and H. Togo, Synthesis, 2013, 45, 2155-2164; (c)
S. Iida and H. Togo, Tetrahedron, 2007, 63, 8274-8281.
Notes and references
1
(a) M. H. Larraufie, G. Maestri, M. Malacria, C. Ollivier, L.
Fensterbank and E. Lacote, Synthesis, 2012, 44, 1279-1292;
(b) D. D. Nekrasov, Russ. J. Org. Chem., 2004, 40, 1387-1402.
R. J. Crutchley, Coord. Chem. Rev., 2001, 219, 125-155.
2
3
4
25 S. Kamijo, T. Jin and Y. Yamamoto, J. Org. Chem., 2002, 67
7413-7417.
,
Y. Ping, Q. Ding and Y. Peng, ACS Catal., 2016, 6, 5989-6005.
Y. Cai, X. Qian, A. Rerat, A. Auffrant and C. Gosmini, Adv.
Synth. Catal., 2015, 357, 3419-3423.
J. Li, W. Xu, J. Ding and K.-H. Lee, Tetrahedron Lett., 2016, 57,
26 (a) M. Inman and C. J. Moody, Chem. Sci., 2013,
R. Vicente, Org. Biomol. Chem., 2011, , 6469-6480; (c) G. R.
Humphrey and J. T. Kuethe, Chem. Rev., 2006, 106, 2875-
2911; (d) S. Cacchi and G. Fabrizi, Chem. Rev., 2005, 105
4, 29-41; (b)
9
5
6
7
8
9
1205-1209.
P. Anbarasan, H. Neumann and M. Beller, Angew. Chem. Int.
Ed., 2011, 50, 519-522.
,
2873-2920; (e) G. W. Gribble, J. Chem. Soc., Perkin Trans. 1,
2000, 1045-1075.
Y. Yang, Y. Zhang and J.-B. Wang, Org. Lett., 2011, 13, 5608-
5611.
27 (a) D. K. Tiwari, J. Pogula, B. Sridhar, D. K. Tiwari and P. R.
Likhar, Chem. Commun., 2015, 51, 13646-13649; (b) D.-Y.
Zhang and X.-P. Hu, Tetrahedron Lett., 2015, 56, 283-295; (c)
C. Zhang, X.-H. Hu, Y.-H. Wang, Z. Zheng, J. Xu and X.-P. Hu, J.
Am. Chem. Soc., 2012, 134, 9585-9588.
P. Anbarasan, H. Neumann and M. Beller, Chem. Eur. J.,
2011, 17, 4217-4222.
K. Kiyokawa, T. Nagata and S. Minakata, Angew. Chem. Int.
Ed., 2016, 55, 10458-10462.
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins