Aryl radical-induced desulfonylative: Ipso -substitution of diaryliodonium salts: An efficient route to sterically hindered biarylamines

Article abstract of DOI:10.1039/d0cc01766c

By using vicinal aryl sulfonamide substituted diaryliodonium salts, a cascade of desulfonylation/aryl migration was promoted by triethylamine in the synthesis of sterically hindered biarylamines, which operated via a radical-induced reaction pathway. The products were readily converted into a variety of important synthons. Furthermore, coupling reactions of N-methyl biarylamine and 1,6-dibromopyrene provided a potentially attractive molecule in OLEDs.

Full text of DOI:10.1039/d0cc01766c

View Article Online
View Journal
ChemComm
Chemical Communications
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: J. Han, L. Wang
and H. Chen, Chem. Commun., 2020, DOI: 10.1039/D0CC01766C.
Volume 54
This is an Accepted Manuscript, which has been through the
Number
January 2018
Pages 1-112
1
4
Royal Society of Chemistry peer review process and has been
accepted for publication.
ChemComm
Chemical Communications
rsc.li/chemcomm
Accepted Manuscripts are published online shortly after 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
Information for Authors.
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 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
S. J. Connon, M. O. Senge et al.
Conformational control of nonplanar free base porphyrins:
towards bifunctional catalysts of tunable basicity
rsc.li/chemcomm

Please do not adjust margins
Page 1 of 4
ChemComm
View Article Online
DOI: 10.1039/D0CC01766C
COMMUNICATION
Aryl Radicals Induced Desulfonylative ipso-Substitution of
Diaryliodonium Salts: An Efficient Route to Steric Hindered
Biarylamines
Received 00th January 20xx,
Accepted 00th January 20xx
Huangguan Chen,a Limin Wang a and Jianwei Han *a
DOI: 10.1039/x0xx00000x
By using vicinal arylsulfonamide substituted diaryliodonium salts, a described diaryliodonium salts as aryl radical sources in
cascade of desulfonylation/aryl migration was promoted by arylations of arenes, heteroarenes and quinones under basic
triethylamine in synthesis of steric hindered biarylamines, which conditions or visible light-mediated photoredox catalysis.8 Very
operated in a radical induced reaction pathway. The products were recently, Lakhdar and Gillaizeau recognized the generation of
readily converted into
a
variety of important synthons. phosphinoyl
radicals
from
the
combination
of
Furthermore, double coupling reactions in one pot with the product diphenyliodonium salts with triethylamine (Et3N) in
of N-methyl biarylamine provided a potentially attractive molecule phosphorylations.9 Despite these elegant advances, the utility
in OLEDs.
of diaryliodonium salts in radical processes still remains largely
unexplored.
a. Arylations involved diaryliodonium salts
The chemistry of diaryliodonium salts has been a topical subject
of growing research interest.1 Their unique reactivity as highly
electrophilic precursors caused by the hyper nucleofuge of the
aryliodo moiety, enables to operate a variety of aromatic
transfer reactions.2 For the mechanistic discussion of iodonium
salts involved tranformations, the conclusive insight on reactive
intermediates generally included aryl cation, aryl cation radical,
iodonium ylide, zwitterionic iodonium or benzyne (Scheme 1,
a).3 The mechanism proposals were explained by the employed
substrates and reaction conditions, which were often closely
balanced and in competition with each other by collection of
the products.4 Gaunt and coworkers have proposed aryl cation
species in the copper catalyzed arylations of arenes, alkenes
and enamines.5 In particular, the use of diaryliodonium salts
provides an access to aryl radicals. Formally, previous studies on
cationic polymerization have revealed free iodoarene radicals
as the key photoinitiator under photolysis.6 Related to synthetic
methodology, Kita and coworkers pioneered the oxidative
coupling reactions by a single-electron-transfer process, in
which the charge-transfer complex of hypervalent iodine atom
and aromatics generated cation radicals with the aid of TMSOTf
in hexafluoroisopropanol.7 Three reports from the research
groups of Zhang and Yu, Tobisu and Chatani, Wang and Ding,
O
Ar
/
Ar
Aux
Nu
Ar
I
Nu
Ar
R
Aryl cation, radical
Zwitterionic iodonium
I
or
or E
X
EWG
Ar
R
E
Ar
EWG
I
Benzyne
Iodonium ylide
b. Synthesis of arylamines
LG
Ar
R1
R1
R1
Metal
Conditions
Aux
+
NH
R2
NH
R2
+
N
Ar
Ar
I
R2
X
Conditions A (by Stuart): KF, H2O, DCE
Conditions B (by Olofsson): Na2CO3, toluene
Traditional coupling reactions
c. Aryl migration of ortho-functionalized diaryliodonium salts ( Our previous work)
CF3
O
S
O
S
O
I
CF3
O
O
O
O
Base
-
δ
I
δ
I
+
X
d. Aryl radical induced intramolecular desulfonylative ipso-substitution (This work)
R
O
S
O
O
N
O
S
Base
SET
- SO2
N
R
N
HR
Aux
I
X
Scheme 1. Arylations and novel reactivity pattern of ortho-
functionalized diaryliodonium salts.
On the other hand, biarylamines occupy a vital position in fine
chemicals.10 Transition-metal catalyzed traditional coupling
reactions (e.g. Suzuki, Kumada, Negeshi, Stille, Ullman reaction,
Buchwald-Hartwig) or dehydrogenative couplings in synthesis
of steric hindered biaryls always meet difficulties due to both
a. Key Laboratory for Advanced Materials and Feringa Nobel Prize Scientist Joint
Research Center, Institute of Fine Chemicals, School of Chemistry & Molecular
Engineering, East China University of Science and Technology, 130 Meilong Road,
Shanghai 200237, China. E-mail: jianweihan@ecust.edu.cn
Electronic Supplementary Information (ESI) available: [details of any supplementary
information available should be included here]. See DOI: 10.1039/x0xx00000x
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 2 of 4
COMMUNICATION
Journal Name
electronic and steric factors (Scheme 1, b).11 Of note, the trapping product 3 in the reaction of 1a with VTieEwMArtPicOle Ownlianes
intermolecular arylation of aliphatic amines using detected by ESI-MS spectra.14 To show the effect of reactivity
DOI: 10.1039/D0CC01766C
diaryliodonium salts were reported by Stuart and Olofsson in caused by the auxiliary group, EPR spin-trapping experiments
synthesis of a wide range of arylated amines (Scheme 1, b). were conducted for the reaction of iodonium salts 1a-1e with
However, biarylamines were not described in their reports.12 In Et3N in the presence of α-phenyl-N-tert-butylnitrone (PBN) at
view of the biarylamine synthesis via Ar-Ar bond-forming room temperature.14 The EPR spectra revealed the formation of
strategies, the benefit of radical process was generally aryl-PBN radical adducts which were characterized by hyperfine
considered since that steric factors did not affect the reactivity. coupling constants (aN = 14.7 G and aH = 2.6 G).15 Interestingly,
However, the selectivity was a crucial issue in comparsion with the intensity of 1a is much larger than the others, which was
metal-catalyzed coupling reactions.13 In this regard, consistant with the best yield of 2aa.
diaryliodonium salts allow excellent regioselectivity by
We subsequently examined the structural diversity of various
adjusting the auxiliary group when aryl radical as a highly N-containing iodonium salts by assessing the substitution
reactive intermediate participates in the reactions.7,12 Recently, effects on the aryl motif and N-substituents. Firstly, substrates
our laboratory have uncovered an intramolecular aryl migration 1 with a broad range of substituents on the benzene ring (Ar1)
of
vicinal
trifluoromethanesulfonate
substituted were first investigated. As shown in Table 2, electron-neutral, -
diaryliodonium salts for the synthesis of steric hindered ortho- donating or -withdrawing substituents were generally well-
iodo diaryl ethers (Scheme 1, c).2d The novel reactivity pattern tolerated, affording the desired products 2aa-2an bearing
of ortho-functionalized diaryliodonium salts inspires us to hydrogen (2aa), methyl (2ab and 2ac), methoxy (2ad), phenyl
explore the further C-N bond formations. Herein, we present (2ae), halogen (2af-j), nitro (2ak), trifluoromethyl (2al), cyano
the base-promoted desulfonylation/aryl migration of vicinal (2am) and ester (2an) functionalities in good to excellent yields
aryl sulfonamide substituted diaryliodonium salts via aryl of 41-99%. We next turned our attention to the substituents on
radical induced process (Scheme 1, d). It was worth to mention the nitrogen of diaryliodonium salts. It was pleased to find that
that biarylamines with steric hindrance are favored by this substrates with various R groups also gave the desired
method.
biarylamines 2ba-2ka in good yields of 40-75%. Specifically, the
reactions went smoothly to afford amines 2ba and 2ca bearing
alkyl groups in 68% and 75% yields, respectively. Products 2da-
2ga with N-substituents of aromatic rings were also obtained in
56-74% yields. Moreover, substrates with benzyl or substituted
benzyl groups were compatible in this reaction, the amines 2ha-
2ka were furnished in 40-66% yields. Then, we sought to
examine the scope of diverse aryl sulfonyl groups (Ar2), the
generality of the protocol was also presented in Table 2.
Substrates 1 bearing ortho-substituted aryls of Ar2 with steric
hindrance were well-tolerated in the reaction and afforded the
desired products 2f-2k in the form of single product with yields
of 56-70%. Notably, steric demanding iodonium salts facilitate
the outcome of the reaction. The case of 2l bearing 2,4,6-
triisopropylphenyl was accomplished in an excellent yield of
94% under the standard conditions. Moreover, iodonium salts
1 with less hindered Ar2 were also successfully employed in this
context. While the sole product of 2m with electron-donating
methoxy group in the para-position of Ar2 was isolated in 69%
yield, several pair of products were observed in formation of
biarylamines (2n-2s) along with the cyclic amides (2n’-2s’),
which is consistent with radical chemistry.16 2n-2s were isolated
in 44-66% yields by ipso-substitution together with 2n’-2s’ as
minor products in 9-31% yields, which can be rationalized in
both pathways of ipso-substitution and direct radical addition.
To gain more insights into the plausible radical mechanism,
deuteration experiments were carried out in order to
determine the source of hydrogen. When the deuterated
solvent of MeCN-d3 was empolyed in the reaction, the signal of
N-H disappeared as shown in 1H-NMR spectra.14 It implied that
the solvent of MeCN served as the hydrogen source. Therefore,
a rational reaction pathway is proposed (Scheme 2). Firstly, the
association of Et3N with iodonium salts 1 forms an electron-
donor-acceptor (EDA) complex 4, which was thermally activated
Table 1. Desulfonylative aryl migration reaction.[a]
O
O
O
N
O
Mes
S
S
Et3N (2 equiv)
N
H
O
N
MeCN, 80 oC, 12 h
N
I
Aux
3
OTf
2aa
1a
e
-
Entry
1
2
3
4
Auxiliary
Phenyl (1a)
Scavenger Yield [%][b]
/
86
64
53
65
20
37
Trace
Trace
4-Methoxyphenyl (1b)
/
2,4,6-Trimethoxylphenyl (1c)
2,4,6-Trimethylphenyl (1d)
4-Nitrophenyl (1e)
Phenyl (1a)
/
/
/
5
6[c]
7[d]
8[e]
TEMPO
TEMPO
BHT
Phenyl (1a)
Phenyl (1a)
[a] Standard conditions: 1 (0.3 mmol), Et3N (2 equiv.) in 5 mL MeCN, 80
oC, 12 hours. [b] Isolated yield. [c] TEMPO
=
2,2,6,6-
tetramethylpiperidine-1-oxyl (2 equiv.). [d] TEMPO (10 equiv.). [e] BHT=
Butylated hydroxytoluene (10 equiv.).
To begin our studies, iodonium triflate (1a) was chosen as the
model substrate and the desired product 2aa was isolated in
86% yield when the reaction was performed in the presence of
2.0 equivalent of Et3N in acetonitrile at 80 oC (Table 1, entry 1).14
Then several substrates 1b-1e bearing various auxiliary groups
were prepared and employed in the reaction. As a result,
electron-donating 4-methoxyphenyl and bukyl 2,4,6-
trimethylphenyl as auxiliary group gave 2aa in comparable
yields of 64% and 65%, respectively. While 4-nitrophenyl 1e
resulted in a poor yield of 20% (Table 1, entry 5). Specifically, 1c
bearing 2,4,6-trimethoxylphenyl only gave 53% yield of 2aa
(Table 1, entry 3). When the radical scavenger of TEMPO
(2,2,6,6-tetramethylpiperidine-1-oxyl) or BHT (butylated
hydroxytoluene) was introduced to the reaction, it was found
that the reaction was inhibited by decreasing the yield of 2aa
significantly (Table 1, entries 6-8). Moreover, the radical
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 4
ChemComm
Please do not adjust margins
Journal Name
COMMUNICATION
to generate the aryl radical 5 with excellent regioselectivity. EPR cyclic amides, the radical 5 goes [1,6]-addition. The cyclic amide
View Article Online
DOI: 10.1039/D0CC01766C
spectra confirmed stable radical of 7 which was formed by 2n' was obtained by aromatization from intermediate 8.
radical trapping experiment with PBN (6). The radical 5 can go Otherwise, a spirocyclic intermediate 9 was generated by [1,5]-
through two alternative reaction pathways depending on the substitution, and the desired biarylamine 2n was formed
substituents of the aryl sulfonyl group.16 In the formation of through desulfonylation and hydrogen abstraction.
Table 2. Scope of diverse N-containing diaryliodonium salts.[a]
O
O
Ar2
O
O
Ar2
S
R
S
N
N
Et3N (2 equiv)
Ar2
R
H
Ar1
N
MeCN, 80 oC, 12 h
R
Ar1
Ar1
I
Ph
OTf
2aa ka & 2f
s
-
2n' - s'
-
1
Ar1
H
N
H
H
N
H
N
H
N
H
N
H
N
N
2af
2ag
2ah
, X = F, 41%
, X = Cl, 99%
, X = Br, 88%
H3CO
Ph
X
2ai
2aj
, X = Cl, 78%
, X = Br, 77%
X
2aa
, 86%
2ab
2ad
, 83%
, 72%
2ac
, 89%
2ae
, 74%
R
N-
X
H
N
H
N
H
H
N
H
N
H
H
N
N
N
n
O
O2N
F3C
X
NC
2ha
, X = H, 66%
2ba
2ca
2da
2ea
, n = 0, 68%
, n = 3, 75%
, X = H, 56%
O
2an
, 70%
O
2am
, 80%
2al
2ak
, 74%
, 53%
2ia
2ja
, X = CH3, 64%
, X = OCH3, 40%
, X = CH3, 61%
2fa
, X = tBu, 65%
Ar2
iPr
2ka
, X = NO2, 46%
2ga
, X = Br, 74%
O
O
X
H
N
O
O
S
iPr
iPr
H
N
N
S
H
N
H
H
N
H
N
N
N
H
N
2f
, X = CH3, 68%
2g
, X = F, 70%
, X = Cl, 66%
, X = Br, 63%
2h
2i
2k
2j
, 56%
, 65%
2l
, 94%
O
2m
, 69%
2n
2n'
, 31%
, 44%
2o'
2o
, 26%
, 66%
NO2
CF3
Ph
O
O
S
O
O
O
O
S
O
S
S
N
N
N
N
H
N
H
H
H
N
N
NO2
CF3
N
Ph
2p
2p'
, 22%
, 56%
2q
2q'
2s'
, 9%
, 52%
, 19%
2r
2r'
2s
, 45%
, 21%
, 64%
[a] Reaction conditions: diaryliodonium salts 1 (0.3 mmol), Et3N (0.6 mmol) in 5 mL MeCN, 80 oC, 12 hours; Isolated yield after column
chromatography.
O
S
As shown in Scheme 3, the N-H group of 2 was easily substituted
by phenyl (10), acetyl (11), and methyl (14) groups in excellent
yields of 70-99%, in which methyl-substituted biarylamine 14
was further transformed to 15 with aniline in an excellent yield
of 90%. Moreover, in the presence of palladium catalysts, the
intramolecular coupling reaction furnished 12 in 71% yield. The
iodination product 13 was afforded in 65% yield, which could be
used as an coupling synthon in further transoformations. To
further demonstrate the potential utility of the novel
desulfonylation/aryl migration reaction, an attractive molecule
16 was synthesized in 80% yield by double Buchwald-Hartwig
coupling reactions with 1,6-dibromopyrene in one pot, which is
a potentially useful compound in the field of organic light
emitting diodes (OLEDs).17
Ph
O
N
t-Bu
O
O
S
O
Ph
N
- PhI + Et3N
heat
6
Ph
Ar
O
N
t-Bu
N
1 + Et3N
I
7
5
Et3N
EDA complex 4
1,6-addition
1,5-substitution
O
O
O
O
S
O
O
S
H3C
H3C
S
H3C
N
N
N
- SO2
CN
H
N
H
2n'
8
9
2n
Scheme 2. The proposed mechanism.
Next, biarylamines as a family of synthetically versatile
synthons were converted into useful aromatic building blocks.
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
COMMUNICATION
Journal Name
I
2011, 353, 3063; (h) L. F. Silva, Jr. and B. Olofsson, Nat. Prod.
View Article Online
Rep., 2011, 28, 1722; (i) E. A. Merritt aDnOdI:B1.0O.1l0o3f9s/sDo0nC,CA0n1g76e6wC.
Chem. Int. Ed., 2009, 48, 9052; (j) V. V. Zhdankin and P. J.
Stang, Chem. Rev., 2008, 108, 5299.
Br
N
Me
HN
N
2
For selected recent examples, see: (a) M. K. Ghosh, J.
Rzymkowski and M. Kalek, Chem. Eur. J., 2019, 25, 9619; (b) C.
Xue, J. Han, M. Zhao and L. Wang, Org. Lett., 2019, 21, 4402;
(c) J. Sheng, R. He, J. Xue, C. Wu, J. Qiao and C. Chen, Org. Lett.,
2018, 20, 4458; (d) H. Chen, J. Han and L. Wang, Angew. Chem.
Int. Ed., 2018, 57, 12313; (e) J. Rae, J. Frey, S. Jerhaoui, S.
Choppin, J. Wencel-Delord and F. Colobert, ACS Catal., 2018,
8, 2805; (f) T. Kitamura, K. Gondo and J. Oyamada, J. Am.
Chem. Soc., 2017, 139, 8416; (g) R. Robidas, V. Guérin, L.
Provençal, M. Echeverria and C. Y. Legault, Org. Lett., 2017,
19, 6420.
For reviews of special topics in diaryliodonium salts: (a) Y. Kita
and T. Dohi, Chem. Rec., 2015, 15, 886; (b) M. S. Yusubov, A.
Yoshimura and V. V. Zhdankin, ARKIVOC, 2016, 342; (c) K.
Morimoto, T. Dohi and Y. Kita, Synlett, 2017, 28, 1680; (d) A.
Yoshimura, A. Saito and V. V. Zhdankin, Chem. Eur. J., 2018,
24, 15156; (e) X. Wang and A. Studer, Acc. Chem. Res., 2017,
50, 1712; (f) E. Malamidou-Xenikaki and S. Spyroudis, Synlett,
2008, 2725.
13
2n
, from , 65%
14
2i
, from , 91%
10
2aa
, from
, 70%
e
d
a
f
Ar2
b
H
N
R
N
H
N
Ar1
N
O
c
11
2aa
, 99%
, from
g
N
3
N
N
12
2n
, from , 71%
16
2aa
, 80%
, from
Scheme 3. Derivatization of biarylamines. Reagents and
conditions: (a) PhI, Pd(OAc)2/(t-Bu)3P, NaOtBu, toluene, 100 oC; (b) Ac2O,
Et3N, DMAP, DCM, 25 oC; (c) Pd(OAc)2, PhI(OAc)2, toluene, 25 oC; (d)
Pd(OAc)2, PhI(OAc)2, I2, DCM, 25 oC; (e) HCHO, HCO2H, 100 oC; (f) PhNH2,
Pd(OAc)2/(t-Bu)3P, NaOtBu, toluene, 100 oC; (g) 1,6-dibromopyrene,
Pd(OAc)2/(t-Bu)3P, NaOtBu, toluene, 100 oC.
4
5
E. Stridfeldt, E. Lindstedt, M. Reitti, J. Blid, P.-O. Norrby and B.
Olofsson, Chem. Eur. J., 2017, 23, 13249.
(a) R. J. Phipps, L. McMurray, S. Ritter, H. A. Duong and M. J.
Gaunt, J. Am. Chem. Soc., 2012, 134, 10773; (b) R. J. Phipps
and M. J. Gaunt, Science, 2009, 323, 1593; (c) F. Zhang, S. Das,
A. J. Walkinshaw, A. Casitas, M. Taylor, M. G. Suero and M. J.
Gaunt, J. Am. Chem. Soc., 2014, 136, 8851; (d) E. Cahard, H. P.
J. Male, M. Tissot and M. J. Gaunt, J. Am. Chem. Soc., 2015,
137, 7986.
(a) J. V. Crivello and J. H. W. Lam, Macromolecules, 1977, 10,
1307; (b) T. Nishikawa, A. Kanazawa and S. Aoshima, Polym.
Chem., 2019, 10, 1056.
In summary, we have developed
a base-promoted
desulfonylation/aryl migration cascade of diaryliodonium salts,
which provides an efficient route to get access to steric
hindered biarylamines. The reaction features wide substrate
scope and good functional group tolerance. Further
investigation of the detailed reaction mechanism and the
application of this transformation are ongoing in our laboratory.
6
7
8
T. Dohi, M. Ito, N. Yamaoka, K. Morimoto, H. Fujioka and Y.
Kita, Angew. Chem. Int. Ed., 2010, 49, 3334.
(a) J. Wen, R.-Y. Zhang, S.-Y. Chen, J. Zhang and X.-Q. Yu, J.
Org. Chem., 2012, 77, 766; (b) M. Tobisu, T. Furukawa and N.
Chatani, Chem. Lett., 2013, 42, 1203; (c) D. Wang, B. Ge, L. Li,
J. Shan and Y. Ding, J. Org. Chem., 2014, 79, 8607.
(a) S. Pal, A.-C. Gaumont, S. Lakhdar and I. Gillaizeau, Org.
Lett., 2019, 21, 5621; (b) W. Lecroq, P. Bazille, F. Morlet-
Savary, M. Breugst, J. Lalevée, A.-C. Gaumont and S. Lakhdar,
Org. Lett., 2018, 20, 4164.
Conflicts of interest
There are no conflicts to declare.
9
Acknowledgments
The work was supported by National Key Research and
Development Program (2016YFA0200302), Shanghai Municipal
Science and Technology Major Project (grant no.
2018SHZDZX03), the National Nature Science Foundation of
China (NSFC 21772039, 21472213) as well as by Croucher
Foundation (Hong Kong) in the form of a CAS-Croucher
Foundation Joint Laboratory Grant, the Fundamental Research
Funds for the Central Universities and Key Laboratory of
Organofluorine Chemistry, Shanghai Institute of Organic
Chemistry, Chinese Academy of Sciences.
10 (a) M. Liang and J. Chen, Chem. Soc. Rev., 2013, 42, 3453; (b)
K. Okano, H. Tokuyama and T. Fukuyama, Chem. Commun.,
2014, 50, 13650.
11 For a review, see: S. P. Stanforth, Tetrahedron, 1998, 54, 263.
12 (a) A. H. Sandtorv and D. R. Stuart, Angew. Chem. Int. Ed.,
2016, 55, 15812; (b) N. Purkait, G. Kervefors, E. Linde and B.
Olofsson, Angew. Chem. Int. Ed., 2018, 57, 11427.
13 (a) J. Malmgren, S. Santoro, N. Jalalian, F. Himo and B.
Olofsson, Chem. Eur. J., 2013, 19, 10334; (b) D. R. Stuart,
Chem. Eur. J., 2017, 23, 15852.
14 For detailed reaction condition optimization, ESI-MS and EPR
spectra of radical trapping experiments, and deuterium
experiment spectra, see the Supporting Information.
15 K. Pan, C.-R. Lin and T.-I. Ho, Magn Reson Chem., 1993, 31,
632.
16 (a) M. L. E.N. da Mata, W. B. Motherwell and F. Ujjainwalla,
Tetrahedron Lett., 1997, 38, 137; (b) F. Ujjainwalla, M. L. E.N.
da Mata, A. M.K. Pennell, C. Escolano, W. B. Motherwell and
S. Vázquez, Tetrahedron, 2015, 71, 6701.
Notes and references
1
For recent reviews, see: (a) A. Boelke, P. Finkbeiner and B. J.
Nachtsheim, Beilstein J. Org. Chem., 2018, 14, 1263; (b) C. K.
Cao, J. Sheng and C. Chen, Synthesis, 2017, 49, 5081; (c) N.
Chatterjee and A. Goswami, Eur. J. Org. Chem., 2017, 3023; (d)
M. Fañanás-Mastral, Synthesis, 2017, 49, 1905; (e) K. Aradi, B.
L. Tóth, G. L. Tolnai and Z. Novák, Synlett, 2016, 27, 1456; (f)
A. Yoshimura and V. V. Zhdankin, Chem. Rev., 2016, 116, 3328;
(g) H. Bonin, E. Fouquet and F.-X. Felpin, Adv. Synth. Catal.,
17 (a) K.-R. Wee, H.-C. Ahn, H.-J. Son, W.-S. Han, J.-E. Kim, D. W.
Cho and S. O. Kang, J. Org. Chem., 2009, 74, 8472; (b) H. Jung,
S. Kang, H. Lee, Y.-J. Yu, J. H. Jeong, J. Song, Y. Jeon and J. Park,
ACS Appl. Mater. Interfaces, 2018, 10, 30022.
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins