Photoinduced Cross-Coupling of Aryl Iodides with Alkenes

Article abstract of DOI:10.1021/acs.orglett.0c03935

A protocol for photoinduced cross-coupling of aryl iodides having polar π-functional groups or elongated π-conjugation with alkenes has been developed. The radical cascade mechanism involving generation of aryl radicals via C-I bond homolysis of photoexcited aryl iodides and their subsequent addition to alkenes is proposed. The method enables iodide-selective cross-coupling over other halogen leaving groups with functional group compatibility on both arene and alkene motifs.

Full text of DOI:10.1021/acs.orglett.0c03935

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Letter
Photoinduced Cross-Coupling of Aryl Iodides with Alkenes
Yuliang Liu, Haoyu Li, and Shunsuke Chiba*
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ABSTRACT: A protocol for photoinduced cross-coupling of aryl iodides having
polar π-functional groups or elongated π-conjugation with alkenes has been
developed. The radical cascade mechanism involving generation of aryl radicals via
C−I bond homolysis of photoexcited aryl iodides and their subsequent addition to
alkenes is proposed. The method enables iodide-selective cross-coupling over other
halogen leaving groups with functional group compatibility on both arene and
alkene motifs.
and electron-rich (hetero)arenes under irradiation with violet
light, in which aryl halides serve as a photoexcited oxidant to
induce SET to oxidize electron-rich (hetero)arenes in the
ground state. (Scheme 1B-ii).8 Herein we report radical
cascade cross-coupling of aryl iodides having polar π-functional
groups or elongated π-conjugation with various sets of alkenes
under irradiation with violet light (390 nm) (Scheme 1C). The
present processes are mediated via generation of aryl radicals
via C−I bond homolysis of photoexcited aryl iodides and their
subsequent addition to alkenes. The resulting transient
secondary or tertiary alkyl radical intermediates could be
oxidatively functionalized by the action of molecular iodine
(I2) or diiodide (I2•−), which are concomitantly formed in the
C−I bond homolysis, to liberate the final products.
In seeking other coupling partners in photoinduced aryl-
cross coupling reactions, we wondered if electron-rich ate
complexes such as silicates could function as alternative
electron donors to induce single-electron reduction of
photoexited aryl halides.9 We thus embarked on our
investigation on the reactions of 4′-haloacetophenones with
methallyltrimethylsilane (2a) (Scheme 2A). The optimization
of the reaction conditions (see the Supporting Information
(SI)) revealed that irradiation with violet light (λmax = 390 nm)
to a solution of 4′-iodoacetophenone (1a) and 2a (5 equiv) in
CH3CN in the presence of CsF (1 equiv) delivers
methallylated arene 3aa in 64% yield. On the other hand,
the reactivity of 4′-bromoacetophenone (1a-Br) was found to
be poorer (22% yield of 3aa with 56% conversion of 1a-Br; see
the SI). We also observed that the photoinduced methallyla-
tion of 1a with pinacol methallylboronate (4a) is promoted in
he cross-coupling of aryl halides with carbon-based
Tnucleophiles allows for facile construction of function-
alized aromatic motifs of various interests. Therefore, a series
of methods for the aryl cross-coupling have been developed.
The nucleophilic aromatic substitution reaction (SNAr) is a
classical yet powerful method of choice, while special substrate
settings and harsh (strongly basic) reaction conditions are
commonly required.1 Nonetheless, aryl cross-coupling with
transition-metal catalysis has advanced the current state-of-the-
art, allowing for employment of various substrate combinations
of aryl halides and nucleophiles with wider substituent
compatibility under milder reaction conditions.2 On the
other hand, leveraging of photoexcited aryl (pseudo)halides
for the aryl-cross coupling has been identified as an alternative
promising method, that circumvents use of precious transition
metal catalysts (Scheme 1).3 In this context, Albini and
Fagnoni have studied generation of triplet aryl cations through
photoexcitation of relatively electron-rich aryl (pseudo)halides
(Ar−X) and ensuing heterolytic dissociation of (pseudo)halide
ions (Scheme 1A). Subsequent capture of the resulting triplet
aryl cations with carbon-based nucleophiles such as alkenes
enables downstream aryl cross-coupling.4 Photoexcited aryl
halides can also function as a single-electron oxidant, accepting
an electron from various electron donors to promote C−X
bond mesolysis to provide aryl radicals either under a stepwise
fashion via the corresponding anion radicals (X = Cl or Br) or
under a concerted manner (X = I).5 The resulting aryl radicals
readily undergo ensuing cross-coupling with radical acceptors
(Scheme 1B). In this context, Li has recently developed a
protocol for single-electron-reduction of photoexcited aryl
(pseudo)halides by an iodide ion for generation of aryl
radicals, which could subsequently be functionalized with
molecular iodine (I2) or bis(pinacolato)diborane (B2pin2)
(Scheme 1B-i).6 The same group also reported photoinduced
electron transfer to aryl halides from sodium phosphite/
phosphinite, allowing for construction of aryl phosphonates.7
Our group has recently developed a protocol for (hetero)-
biaryl-cross coupling between electron-deficient aryl halides
Received: November 28, 2020
Published: January 6, 2021
https://dx.doi.org/10.1021/acs.orglett.0c03935
© 2021 American Chemical Society
Org. Lett. 2021, 23, 427−432
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Scheme 1. Photoinduced Aryl Cross-Coupling
Scheme 2. Scope on Methallylation with Respect to Aryl
Iodides
the presence of Na2CO3, despite moderate process efficiency
(50% yield of 3aa) (see the SI for details).
Differently from photoinduced allylation via triplet aryl
cations that necessitates use of electron-rich aryl halides and
irradiation with energy intensive UV light (Scheme 1A),4 the
present allylation protocol employing aryl iodides having polar
π-electron-withdrawing group(s) under irradiation with violet
light could potentially exhibit wider functional group
compatibility. Therefore, we next turned our attention to
investigate the substrate scope with respect to the aryl iodides
(Scheme 2A).10 As expected, the method allows for installation
of various polar π-electron-withdrawing groups such as an
ethoxycarbonyl group (for ester 3ba), an aminocarbonyl group
(for amide 3ca), and a cyano group (for nitrile 3da). The
position of the electron-withdrawing groups could be not only
at the para-position but also at the meta-position (for 3ea and
3fa), which argues against the possibility of the SNAr
mechanism. The method is also compatible with methallyla-
tion of thiophene (for 3ga) as well as multisubstituted
aromatics (for 3ha−3ka). We found that nonactivated aryl
iodides based on biphenyl (for 3la) and naphthalene (for 3ma)
are compatible for methallylation, while iodobenzene (1n)
could not be engaged. The reactivity difference between aryl
iodide and bromide stimulated us to explore chemoselective
functionalization of polyhalogenated aryl substrates. We were
pleased to observe chemoselective methallylation on a C−I
bond over C−F, C−Cl, and C−Br bonds (Scheme 2B).
a
Reaction conditions: 1 (0.5 mmol), 2a (5 equiv), CsF (1 equiv),
CH3CN (5 mL, 0.1 M), 390 nm light (Kessil lamp), 25 °C (water
bath). Isolated yields of 3 were recorded. 3 were isolated with
contamination of the corresponding styrene via alkene isomerization
b
(0−7% on the basis of 1H NMR analysis). The isolated yield of 3aa
c
from the reaction in 1 mmol scale. Use of pinacol methallylboronate
d
(4a) (5 equiv) in the presence of Na2CO3 (1 equiv). Bulb-to-bulb
distillation was performed for purification. Gel permeation
chromatography (GPC) was performed for purification.
e
We next investigated the scope of allylsilanes 2 (Scheme
3A). The method could engage not only simple allylsilane 2b
but also those having acetoxymethyl and aryl groups (for 2c
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alkyl radical intermediates is indispensable to facilitate the
cross-coupling (see the SI for details). Therefore, the following
radical cascade process is proposed as a mechanistic possibility
for the photoinduced allylation (Scheme 3C). Namely,
irradiation of aryl iodides 1 with violet light populates their
photoexcited states A (most likely in the triplet state), which
slowly undergo C−I bond homolysis to form aryl radicals B
and atomic iodine (I•).15 Although the recombination of aryl
radicals B with I• could regenerate 1, in the presence of
allylsilanes 2, aryl radicals B undergo irreversible addition to 2
to form β-silyl radicals C, and atomic iodine (I•) dimerizes to
molecular iodine (I2) or couples with iodide (I−) to diiodide
Scheme 3. Scope of Allylating Reagents and Proposed
Mechanism
16
(I2•−). Single-electron oxidation of C by I2 or I2 forms β-
silyl carbocations D,17 and subsequent elimination of silyl
fluoride liberates allylated products 3. Alternatively, radical
iodination of C18 followed by ionic desilylative elimination of
the resulting alkyl iodides E might occur.19 The experimental
observations on the regioselective arylation of allylsilanes 2e
(Scheme 3A) and 2f (Scheme 3B) well corroborate the
proposed process involving the Markovnikov addition of aryl
radicals B onto allylsilanes 2.
•−
The proposed radical cascade mechanism stimulated us to
explore other types of alkenes as the coupling partners. We
found that electron-rich enol ethers are compatible (Scheme
4).20 For example, treatment of aryl iodides 1 with 2-
Scheme 4. Aryl Cross-Coupling with Enol Ethers
a
Reaction conditions: 1d (0.5 mmol), 2 (5 equiv), CsF (1 equiv),
CH3CN (5 mL, 0.1 M), 390 nm light (Kessil lamp), 25 °C (water
b
bath). Isolated yields of 3 were recorded. 3dc was isolated with
contamination of the corresponding styrene 3dc′ in 8% yield (on the
c
1
basis of H NMR analysis) via olefin isomerization. 3df was isolated
with contamination of the corresponding styrene 3df′ in 2% yield (on
d
1
the basis of H NMR analysis) via olefin isomerization. Reaction
conditions: 1d (0.5 mmol) 4f (5 equiv), Na2CO3 (1 equiv), CH3CN
(5 mL, 0.1 M), 390 nm light (Kessil lamp), 25 °C (water bath).
and 2d). The reaction of allylsilane 2e based on a
dihydronaphthalene core resulted in regioselective arylation
with formation of an exo-methylene moiety. We also explored
prenylation using 1,1-dimethylallyltrimethylsilane (2f)11
(Scheme 3B). As expected, photoinduced prenylation of 1d
proceeded to give 3df, while the yield was moderate (44%). In
this case, we found use of readily available pinacol 1,1-
dimethylallylboronate (4f)12 to be optimal, affording 3df in
56% yield. We anticipate that this photoinduced prenylation
with 4f offers an alternative route to the prenylated arenes,
which are often found in molecules of biological and
pharmaceutical interest.13
a
Reaction conditions: 1 (0.5 mmol), 5 (3 equiv), K2CO3 (1 equiv),
CH3CN (5 mL, 0.1 M), 390 nm light (Kessil lamp), 25 °C (water
bath). Isolated yields of 6 were recorded. The isolated yield of 6d
from the reaction in 1 mmol scale. 5 equiv of 5 were used. Reaction
conditions: 1d (0.5 mmol), 7 or 8 (5 equiv), K2CO3 (1 equiv),
CH3CN (5 mL, 0.1 M), 390 nm light (Kessil lamp), 25 °C (water
bath).
b
c
d
methoxypropene (5) (3 equiv) in the presence of K2CO3
under irradiation with violet light followed by workup with
aqueous acid afforded acetomethylated arenes 6 in good yields
(Scheme 4A). The reactions with α-methoxystyrene (7) and
1,1-diethoxyethene (8) allowed for installation of the phenyl
Several control experiments including the reactions using
tetramethylsilane instead of allylsilanes and the radical clock
studies14 revealed that silicates do not function as the electron
donor but the presence of alkenes that can form oxidizable
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ketone motif (for 9) and ethyl ester moiety (for 10) (Scheme
4B).
We also observed that nonactivated alkenes could be
engaged in the photoinduced aryl cross-coupling. For example,
α-methylstyrene (11) was found to be compatible, providing a
mixture of terminal and internal alkenes 12 in good combined
yield (Scheme 5A). Similarly, the reaction with methylene-
conditions is commonly associated with semipinacol rearrange-
ment of the transient carbocation intermediates, providing
ring-expanded ketones as the major products.23 On the
contrary, the present protocol afforded spirocyclic epoxides
20b and 20c as the sole product.
Finally, by taking advantage of the chemoselective coupling
on the aryl−I bond over the aryl−Br bond for functionalization
of polyhalogenated arenes 1q and 1s, we demonstrated their
difunctionalization via consecutive photoinduced cross-cou-
pling reactions. For example, photoinduced iodide-selective
prenylation of 1q with pinacol 1,1-dimethylallylboronate (4f)
provided 21 in 64% yield, which was followed by photo-
induced heterobiaryl coupling with N-methylpyrrole to form
difunctionalized arene 22 (Scheme 6A). Similarly, consecutive
photoinduced cross-coupling of 1s with 4-pentenoic acid (15)
and N-methylpyrrole delivered multifunctionalized arene 24
(Scheme 6B).
a
Scheme 5. Aryl Cross-Coupling with Unactivated Alkenes
Scheme 6. Consecutive Aryl Cross-Couplings on
Polyharogenated Arenes
a
Reaction conditions: 1d (0.5 mmol), alkenes (5 equiv), K2CO3 (1
equiv), CH3CN (5 mL, 0.1 M), 390 nm light (Kessil lamp), 25 °C
(water bath). Isolated yields of the products were recorded.
In conclusion, we have developed a concise protocol for
cross-coupling reactions of aryl iodides with alkenes, which is
driven solely by irradiation with violet light (390 nm). The key
enabling the advance in this protocol is use of photoexcited
aryl iodides as a source of aryl radicals that undergo irreversible
addition to the alkene coupling partners. As the resulting
cyclohexane (13) proceeded smoothly to afford 14 in an exo-
selective fashion (Scheme 5B). Use of 4-pentenoic acid (15)
and 5-hexenoic acid (16) enabled facile construction of
lactones 17 and 18, respectively, via intramolecular capture of
the resulting secondary alkyl radical intermediates oxidatively
with the carboxylic acid moiety (Scheme 5C).21 Interestingly,
we observed that arylative epoxidation proceeded when 1,1-
dimethylallyl alcohol (19a) was used as a coupling partner with
1d, affording epoxide 20a in 66% yield (Scheme 5D). This
radical cascade process circumvents use of transition-metal
catalysts,22 showcasing the potential utility of this protocol .
Another unique feature found from this study was the ability of
the present method in the construction of spirocyclic epoxides
20b and 20c. Radical-mediated carbo-functionalization of vinyl
cycloalkanols such as 19b and 19c under redox reaction
oxidizable alkyl radicals could be oxidatively functionalized by
•−
concomitantly formed molecular iodine (I2) or diiodide (I2
)
to complete the process, the overall process is rendered redox
neutral. While the presence of polar π-electron-withdrawing
groups on aryl iodides is a typical prerequisite to make use of
violet light for their excitation, it could be considered as a
synthetic advantage, as such functional groups could be
appreciated for further manipulation of the resulting scaffolds.
Therefore, we anticipate that this transition-metal-free protocol
for aryl cross-coupling could be useful in various synthetic
endeavors.
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(3) (a) Liu, W.; Li, J.; Huang, C.-Y.; Li, C.-J. Angew. Chem., Int. Ed.
2020, 59, 1786−1796. (b) Liu, W.; Li, C.-J. Synlett 2017, 28, 2714−
2754. (c) Dichiarante, V.; Protti, S.; Fagnoni, M. J. Photochem.
Photobiol., A 2017, 339, 103−113. (d) Ravelli, D.; Protti, S.; Fagnoni,
M. Chem. Rev. 2016, 116, 9850−9913. (e) Dichiarante, V.; Fagnoni,
M. Synlett 2008, 2008, 787−800. (f) Fagnoni, M.; Albini, A. Acc.
Chem. Res. 2005, 38, 713−721.
(4) (a) Bergami, M.; Protti, S.; Ravelli, D.; Fagnoni, M. Adv. Synth.
Catal. 2016, 358, 1164−1172. (b) Raviola, C.; Chiesa, F.; Protti, S.;
Albini, A.; Fagnoni, M. J. Org. Chem. 2016, 81, 6336−6342.
(c) Qrareya, H.; Raviola, C.; Protti, S.; Fagnoni, M.; Albini, A. J.
Org. Chem. 2013, 78, 6016−6024. (d) Manet, I.; Monti, S.; Grabner,
G.; Protti, S.; Dondi, D.; Dichiarante, V.; Fagnoni, M.; Albini, A.
Chem. - Eur. J. 2008, 14, 1029−1039. (e) Protti, S.; Dondi, D.;
Fagnoni, M.; Albini, A. Eur. J. Org. Chem. 2008, 2008, 2240−2247.
(f) Protti, S.; Fagnoni, M.; Albini, A. J. Am. Chem. Soc. 2006, 128,
10670−10671. (g) Dichiarante, V.; Fagnoni, M.; Albini, A. Chem.
Commun. 2006, 3001−3003. (h) Dichiarante, V.; Fagnoni, M.; Mella,
M.; Albini, A. Chem. - Eur. J. 2006, 12, 3905−3915. (i) Protti, S.;
Fagnoni, M.; Albini, A. Angew. Chem., Int. Ed. 2005, 44, 5675−5678.
(j) Protti, S.; Fagnoni, M.; Mella, M.; Albini, A. J. Org. Chem. 2004,
69, 3465−3473. (k) Mella, M.; Coppo, P.; Guizzardi, B.; Fagnoni, M.;
Freccero, M.; Albini, A. J. Org. Chem. 2001, 66, 6344−6352.
(5) (a) Takeda, N.; Poliakov, P. V.; Cook, A. R.; Miller, J. R. J. Am.
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.orglett.0c03935.
■
sı
Experimental procedures, spectral data (PDF)
FAIR data, including the primary NMR FID files, for
compounds 1c, 1p, 2d−f, 3aa−3sa, 4a, 4f, 6b, 6d, 6f, 6g,
6j, 6l, 7−10, 12, 14, 17, 18, 19b, 19c, 20a−c, and 21−
28 (ZIP)
Accession Codes
CCDC 2044125 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/data_request/cif, or by emailing
data_request@ccdc.cam.ac.uk, or by contacting The Cam-
bridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Author
■
Shunsuke Chiba − Division of Chemistry and Biological
Chemistry, School of Physical and Mathematical Sciences,
Nanyang Technological University, Singapore 637371,
Singapore; orcid.org/0000-0003-2039-023X;
Email: shunsuke@ntu.edu.sg
́
Chem. Soc. 2004, 126, 4301−4309. (b) Pause, L.; Robert, M.; Saveant,
J.-M. J. Am. Chem. Soc. 1999, 121, 7158−7159.
(6) (a) Li, L.; Liu, W.; Zeng, H.; Mu, X.; Cosa, G.; Mi, Z.; Li, C.-J. J.
Am. Chem. Soc. 2015, 137, 8328−8331. (b) Yang, X.; Liu, W.; Li, L.;
Wei, W.; Li, C.-J. Chem. - Eur. J. 2016, 22, 15252−15256. (c) Li, L.;
Liu, W.; Mu, X.; Mi, Z.; Li, C.-J. Nat. Protoc. 2016, 11, 1948−1954.
(d) Liu, W.; Yang, X.; Gao, Y.; Li, C.-J. J. Am. Chem. Soc. 2017, 139,
8621−8627.
Authors
Yuliang Liu − Division of Chemistry and Biological Chemistry,
School of Physical and Mathematical Sciences, Nanyang
Technological University, Singapore 637371, Singapore
Haoyu Li − Division of Chemistry and Biological Chemistry,
School of Physical and Mathematical Sciences, Nanyang
Technological University, Singapore 637371, Singapore
(7) Zeng, H.; Dou, Q.; Li, C.-J. Org. Lett. 2019, 21, 1301−1305.
(8) Hayashi, H.; Wang, B.; Wu, X.; Teo, S. J.; Kaga, A.; Watanabe,
K.; Takita, R.; Yeow, E. K. L.; Chiba, S. Adv. Synth. Catal. 2020, 362,
2223−2231.
(9) For photoinduced decyanative allylation of dicyanobenzenes
based on single-electron transfer from allylsilanes and their silicates.
(a) Matsuoka, D.; Nishigaichi, Y. Chem. Lett. 2015, 44, 163−165.
(b) Matsuoka, D.; Nishigaichi, Y. Chem. Lett. 2014, 43, 559−561.
(c) Mizuno, K.; Nakanishi, K.; Otsuji, Y. Chem. Lett. 1988, 17, 1833−
1836.
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.orglett.0c03935
Notes
(10) Steady state UV−vis spectra revealed that all the aryl iodides
except for iodobenzene (1n) could be excited under irradiation with
violet light. The charge transfer band derived from electron donor−
acceptor (EDA) interaction was not observed in steady state UV−vis
spectra of the mixtures of aryl iodides and alkenes. See the SI for
details.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by funding from Nanyang
Technological University (NTU) and the Singapore Ministry
of Education (Academic Research Fund Tier 2: MOE2017-T2-
1-064) (for S.C.).
(11) Bennetau, B.; Pillot, J.-P.; Dunogues, J.; Calas, R. J. Chem. Soc.,
Chem. Commun. 1981, 1094−1095.
(12) Clary, J. W.; Rettenmaier, T. J.; Snelling, R.; Bryks, W.; Banwell,
J.; Wipke, W. T.; Singaram, B. J. Org. Chem. 2011, 76, 9602−9610.
(13) (a) Yazaki, K.; Sasaki, K.; Tsurumaru, Y. Phytochemistry 2009,
70, 1739−1745. (b) Hoarau, C.; Pettus, T. R. R. Synlett 2003, 127−
137.
DEDICATION
■
Dedicated to Professor Ilhyong Ryu on the occasion of his
70th birthday.
(14) Johnston, L. J.; Lusztyk, J.; Wayner, D. D. M.; Abeywickreyma,
A. N.; Beckwith, A. L. J.; Scaiano, J. C.; Ingold, K. U. J. Am. Chem. Soc.
1985, 107, 4594−4596.
REFERENCES
■
(1) For recent reviews, see: (a) Rohrbach, S.; Smith, A. J.; Pang, J.
H.; Poole, D. L.; Tuttle, T.; Chiba, S.; Murphy, J. A. Angew. Chem.,
Int. Ed. 2019, 58, 16368−16388. (b) Kwan, E. E.; Zeng, Y.; Besser, H.
A.; Jacobsen, E. N. Nat. Chem. 2018, 10, 917−923.
(15) (a) Wagner, P. J.; Sedon, J. H.; Gudmundsdottir, A. J. Am.
Chem. Soc. 1996, 118, 746−754. (b) Wagner, P. J.; Waite, C. I. J. Phys.
Chem. 1995, 99, 7388−7394. (c) Wagner, P. J.; Sedon, J.; Waite, C.;
Gudmundsdottir, A. J. Am. Chem. Soc. 1994, 116, 10284−10285.
(16) Reduction potential of molecular iodine (I2) is 0.24 V vs SCE,
while that of diiodide (I2•−) is 0.78 V vs SCE; see: (a) Boschloo, G.;
Hagfeldt, A. Acc. Chem. Res. 2009, 42, 1819−1826. (b) Aranzaes, J. R.;
Daniel, M.-C.; Astruc, D. Can. J. Chem. 2006, 84, 288−299.
(17) For oxidation potentials of alkyl radicals, see: (a) Fu, Y.; Liu, L.;
Yu, H.-Z.; Wang, Y.-M.; Guo, Q.-X. J. Am. Chem. Soc. 2005, 127,
7227−7234. (b) Wayner, D. D. M.; McPhee, D. J.; Griller, D. J. Am.
̈
(2) For selected reviews, see: (a) de Meijere, A.; Brase, S.; Oetreich,
M. Metal-Catalyzed Cross-Coupling Reactions and More; Wiley: 2014.
(b) Hazari, N.; Melvin, P. R.; Beromi, M. M. Nature Reviews Chemistry
2017, 1, 0025. (c) Ruiz-Castillo, P.; Buchwald, S. L. Chem. Rev. 2016,
116, 12564−12649. (d) Magano, J.; Dunetz, J. R. Chem. Rev. 2011,
111, 2177−2250. (e) Alberico, D.; Scott, M. E.; Lautens, M. Chem.
Rev. 2007, 107, 174−238. (f) Corbet, J.-P.; Mignani, G. Chem. Rev.
2006, 106, 2651−2710.
431
https://dx.doi.org/10.1021/acs.orglett.0c03935
Org. Lett. 2021, 23, 427−432

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pubs.acs.org/OrgLett
Letter
Chem. Soc. 1988, 110, 132−137. (c) Wayner, D. D. M.; Houmam, A.
Acta Chem. Scand. 1998, 52, 377−384. (d) Wayner, D. D. M.; Griller,
D. J. Am. Chem. Soc. 1985, 107, 7764−7765.
(18) For selected reports on radical iodination, see: (a) Yang, X.;
Liu, W.; Li, L.; Wei, W.; Li, C.-J. Chem. - Eur. J. 2016, 22, 15252−
15256. (b) Hang, Z.; Li, Z.; Liu, Z.-Q. Org. Lett. 2014, 16, 3648−
3651. (c) Tang, S.; Wu, Y.; Liao, W.; Bai, R.; Liu, C.; Lei, A. Chem.
Commun. 2014, 50, 4496−4499.
(19) As another minor mechanistic possibility, the process mediated
by single-electron reduction of photoexcited aryl iodides by the
oxidizable alkyl radical intermediates might be possible. This enables
the process under electron catalysis. For selected reviews on electron
catalysis, see: (a) Nocera, G.; Murphy, J. A. Synthesis 2020, 52, 327−
336. (b) Smith, A. J.; Poole, D. L.; Murphy, J. A. Sci. China: Chem.
2019, 62, 1425−1438. (c) Studer, A.; Curran, D. P. Angew. Chem., Int.
Ed. 2016, 55, 58−102. (d) Studer, A.; Curran, D. P. Nat. Chem. 2014,
6, 765−773. (e) Shirakawa, E.; Hayashi, T. Chem. Lett. 2012, 41,
130−134.
(20) (a) Felipe-Blanco, D.; Gonzalez-Gomez, J. C. Adv. Synth. Catal.
2018, 360, 2773−2778. (b) Wang, L.; Shen, J.; Yang, S.; Liu, W.;
Chen, Q.; He, M. Green Chem. 2018, 20, 1290−1296. (c) de Souza,
A. A. N.; Silva, N. S.; Muller, A. V.; Polo, A. S.; Brocksom, T. J.; de
̈
Oliveira, K. T. J. Org. Chem. 2018, 83, 15077−15086. (d) Shaaban, S.;
Jolit, A.; Petkova, D.; Maulide, N. Chem. Commun. 2015, 51, 13902−
̈
13905. (e) Hering, T.; Hari, D. P.; Konig, B. J. Org. Chem. 2012, 77,
10347−10352.
(21) (a) Felipe-Blanco, D.; Gonzalez-Gomez, J. C. Eur. J. Org. Chem.
2019, 2019, 7735−7744. (b) Guo, W.; Cheng, H.-G.; Chen, L.-Y.;
Xuan, J.; Feng, Z.-J.; Chen, J.-R.; Lu, L.-Q.; Xiao, W.-J. Adv. Synth.
Catal. 2014, 356, 2787−2793. (c) Gao, Y.; Xu, J.; Zhang, P.; Fang, H.;
Tang, G.; Zhao, Y. RSC Adv. 2015, 5, 36167−36170.
(22) (a) Bunescu, A.; Wang, Q.; Zhu, J. Org. Lett. 2015, 17, 1890−
1893. (b) Hayashi, S.; Yorimitsu, H.; Oshima, K. J. Am. Chem. Soc.
2009, 131, 2052−2053.
(23) (a) Alazet, S.; Preindl, J.; Simonet-Davin, R.; Nicolai, S.;
Nanchen, A.; Meyer, T.; Waser, J. J. Org. Chem. 2018, 83, 12334−
̈
12356. (b) Bergonzini, G.; Cassani, C.; Lorimer-Olsson, H.; Horberg,
J.; Wallentin, C.-J. Chem. - Eur. J. 2016, 22, 3292−3295. (c) Sahoo,
B.; Li, J.-L.; Glorius, F. Angew. Chem., Int. Ed. 2015, 54, 11577−
11580.
432
https://dx.doi.org/10.1021/acs.orglett.0c03935
Org. Lett. 2021, 23, 427−432