Ru-catalyzed (E)-specific ortho-C-H alkenylation of arenecarboxylic acids by coupling with alkenyl bromides

Article abstract of DOI:10.1021/acs.orglett.1c00956

In the presence of [p-cymene)RuCl2]2, (E)-configured alkenyl bromides couple with aromatic carboxylates to form ortho-vinylbenzoic acids. This C-H vinylation proceeds in high yields without any activating phosphine ligands and has an excellent functional group tolerance. Starting from commonly available (E/Z)-mixtures of alkenyl bromides, (E)-configured vinyl arenes or dienes are formed exclusively. Mechanistic studies show that this selectivity is achieved because the (E)-configured alkenyl bromides undergo a smooth coupling, whereas the (Z)-isomers are rapidly eliminated with the formation of alkynes.

Full text of DOI:10.1021/acs.orglett.1c00956

pubs.acs.org/OrgLett
Letter
Ru-Catalyzed (E)‑Specific ortho-C−H Alkenylation of Arenecarboxylic
Acids by Coupling with Alkenyl Bromides
Zhiyong Hu, Florian Belitz, Guodong Zhang, Florian Papp, and Lukas J. Gooßen*
Cite This: Org. Lett. 2021, 23, 3541−3545
Read Online
sı
*
Metrics & More
Article Recommendations
Supporting Information
ACCESS
ABSTRACT: In the presence of [p-cymene)RuCl2]2, (E)-configured
alkenyl bromides couple with aromatic carboxylates to form ortho-
vinylbenzoic acids. This C−H vinylation proceeds in high yields without
any activating phosphine ligands and has an excellent functional group
tolerance. Starting from commonly available (E/Z )-mixtures of alkenyl
bromides, (E)-configured vinyl arenes or dienes are formed exclusively.
Mechanistic studies show that this selectivity is achieved because the (E)-
configured alkenyl bromides undergo a smooth coupling, whereas the (Z)-isomers are rapidly eliminated with the formation of
alkynes.
Scheme 1. Established Syntheses of 2-Alkenylbenzoic Acids
ortho-Alkenylbenzoic acid moieties are abundant in natural
products, agrochemicals, pharmaceuticals, and functional
materials (Figure 1).1 They are also important synthetic
hubs en route to isocoumarins, dihydroisocoumarin, and
phthalide derivatives.2
Figure 1. 2-Alkenylbenzoic acid moieties in natural products.
Traditional synthetic entries to this substrate class, such as
Wittig olefinations,3 Mizoroki−Heck reactions,4 cross-cou-
plings,5 and Sonogashira/hydrogenation sequences, are based
on ortho-prefunctionalized benzoates (Scheme 1).6 In contrast,
ortho-C−H alkenylation strategies draw on non-prefunctional-
ized benzoic acids, which are widely available in great
structural diversities. The use of simple carboxylates as
directing groups is highly desirable, since they can be easily
removed afterward by decarboxylation or utilized as anchor
point for follow-up decarboxylative couplings.7 ortho-C−H
alkenylations of benzoates have been achieved via Fujiwara-
type oxidative couplings of benzoic acids with alkenes using Rh
or Ru catalysts in the presence of stoichiometric amounts of
copper or silver salts.8 Hydroarylations of alkynes with benzoic
acids are particularly atom-economic synthetic entries to such
structures.9 However, only a few efficient protocols exist that
proceed with high regioselectivities and reliably stop at the
stage of the alkenyl arene without concomitant lactoniza-
tion.9b−e
As a potential alternative, stereospecific C−H alkenylations
based on abundant alkenyl bromides are of considerable
interest.10 There are efficient protocols for carboxylate-directed
C−H arylations of benzoic acids based on aryl (pseudo)halide
electrophiles,11 but only two examples of alkenyl halide
coupling products can be found in the extensive scope
tables.11e,h This illustrates that the reactivity of this substrate
class has not yet been evaluated systematically, and no
generally applicable protocol has been established.
Received: March 19, 2021
Published: April 22, 2021
https://doi.org/10.1021/acs.orglett.1c00956
© 2021 American Chemical Society
Org. Lett. 2021, 23, 3541−3545
3541

Organic Letters
pubs.acs.org/OrgLett
Letter
Efficient C−H alkenylation protocols have only been
developed for arenes bearing strong directing groups, such as
pyridines, picolinamide, and other amides (Scheme 2a).12 For
insertion into the double bond despite the tendency of the
latter to undergo oxidative additions.14e,f If the alkenyl halides
were incorporated along this pathway, concomitant β-bromide
elimination through the dissociation of the O−Ru bond, the
rotation of the C−Ru bond, and the coordination of the O−Ru
bond would lead to the same alkenylated products but with the
opposite stereochemistry at the alkene (Scheme 2, path b).
Thus, (Z)-products should result from (E)-alkenyl bromide
starting materials.
Scheme 2. C−H Functionalizations Using Alkenyl Halides
To explore the reactivities of benzoic acids toward alkenyl
bromides, we used 2-methylbenzoic acid (1a) and commer-
cially available β-bromostyrene (2a, E/Z = 6.7:1) as a model
system. We investigated various Ru-based catalyst systems and
found that the desired olefination product 3aa was formed
most efficiently in the presence of [Ru(p-cymene)Cl2]2
without activating phosphines (Tables 1 and S1, entry 1).
a
Table 1. Optimization of the Alkenylation Reaction
b
yield (%)
entry
base
solvent
conversion of 1a (%)
3aa
4
1
2
3
4
5
6
7
8
K2CO3
Na2CO3
K3PO4
NMP
NMP
NMP
NMP
90
88
90
72
92
56
84
83
52
>95
79
30
72
69
72
50
74
50
63
60
41
87
66
16
n.d.
1
n.d.
n.d.
n.d.
1
NaHCO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
NMP
toluene
dioxane
tAmOH
DMF
DMAc
diglyme
H2O
example, Daugulis reported the Pd-catalyzed regioselective
alkenylations of anilides with haloacrylate esters,12a Inoue
published several examples of Ru-catalyzed alkenylations that
use N-containing directing groups,12b−d and Punji et al.
disclosed a Ni-catalyzed C−H alkenylation of indoles based on
pyridine directing groups.12f
1
1
9
1
1
1
n.d.
10
11
12
Compared to these nitrogen-based directing groups,
carboxylates are more weakly coordinating,13 and it is
challenging to develop analogous carboxylate-directed C−H
alkenylations. We considered ruthenium to be particularly
attractive as a catalyst metal for the envisioned process due to
its low price and ease of handling. Its activity in carboxylate-
directed hydroarylations9,14 and cross-couplings15 is well
documented, and plausible catalytic cycles can be drafted
based on known elemental steps (Scheme 2b). This is why we
focused on inexpensive ruthenium complexes in our search for
an effective catalyst.
deviations from optimal conditions in entry 10
13
14
15
16
17
110 °C
0.8 eq. base
80
78
73
50
n.d.
88
9
n.d.
n.d.
73
n.d.
n.d.
pure (Z)-isomer
pure (E)-isomer
under air
<5
>95
38
a
Conditions are as follows: 0.25 mmol 1a, 0.5 mmol 2a, 2.5 mol %
[Ru(p-cymene)Cl2]2, 1.5 mL of solvent, 120 °C, 18 h, Ar. Yields
were determined after esterification with iodomethane by GC analysis
b
using tetradecane as an internal standard; n.d. stands for not detected
Notably, there are two orthogonal pathways along which
alkenyl bromides might react with benzoic acids in the
presence of ruthenium catalysts. It is well-established that the
reaction of benzoic acids with ruthenium complexes leads to
the formation of ruthenacycles. In the presence of phosphines,
such complexes were found to react with aryl bromides via
oxidative addition and concurrent reductive C−C bond
formation.11b,e,12b−d The stereochemistry should be preserved
for alkenyl bromide substrates in this oxidative addition
pathway (Scheme 2, path a) such that (E)-configured
substrates would lead to (E)-configured products and vice
versa. However, in the absence of activating phosphines
ruthenacycles are known to react with allyl electrophiles via
The reaction is facilitated by mild bases, particularly Cs2CO3,
and works best in polar amide solvents; the best results were
obtained for DMAc (Table 1, entries 1−12). Other bases were
found to be less effective (see Table S1). Control experiments
confirmed that the optimal reaction temperature is 120 °C and
a slight excess of base is beneficial (Table 1, entries 13 and 14,
respectively).
The stereochemical outcome of the reaction was remarkable.
The (E)-product was formed exclusively not only when
starting from pure (E)-β-bromostyrene (2a) but also when an
excess of 2a was administered as an isomeric mixture (Table 1,
entries 10 and 16). This is very advantageous from a synthetic
3542
https://doi.org/10.1021/acs.orglett.1c00956
Org. Lett. 2021, 23, 3541−3545

Organic Letters
pubs.acs.org/OrgLett
Letter
standpoint, since alkenyl bromides are often obtained as (E/
Z)-mixtures. The retention of the stereochemistry suggests that
the coupling of (E)-2a proceeds via a stereospecific oxidative
addition mechanism (Scheme 2, path a). However, pure (Z)-β-
bromostyrene ((Z)-2a) did not give any product, which
indicates that the (Z)-β-bromostyrene was not converted into
(E)-β-bromostyrene and thus the (E)-product originated only
from the (E)-β-bromostyrene content of the starting materi-
al.16 Instead, phenylacetylene and its follow-up products were
obtained (Table 1, entry 15). The reaction gave only
unsatisfactory yields under air, so strictly anaerobic conditions
are recommended (Table 1, entry 17).
kH/kD = 2.6 indicates that the C−H activation is rate-
determining (Scheme 3d). This reactivity is only observed for
benzoic acids, as esters do not undergo C−H vinylation (see
the Supporting Information). All these findings are in good
agreement with the oxidative addition pathway (Scheme 2,
path a).
We went on to investigate the scope of the C−H
alkenylation with regard to the alkenyl bromides (Scheme
4). Various (E)-configured 2-(hetero)arylalkenyl bromides
a
Scheme 4. Scope in Regard to the Alkenyl Bromides
We investigated this unexpected outcome by separately
treating (E)- and (Z)-bromostyrene with Cs2CO3 in the
absence of the catalyst. The (Z)-derivative was swiftly
eliminated to give the phenylacetylene, whereas the (E)-
derivative remained unchanged (more detail in the Supporting
Information). This is in line with a base-assisted anti-
elimination of HBr, which proceeds swiftly only if an
antiperiplanar arrangement of the substrate is possible.17 It is
not feasible for (E)-configured alkenyl bromides under such
mild conditions.18 The competing elimination process results
in an amplification of the (E/Z)-ratio.
The mechanism of the alkenylation reaction was further
investigated by deuterium labeling experiments. Upon stirring
o-toluic acid 1a in D2O under the reaction conditions, rapid
ortho-deuteration was observed, confirming that the C−H
activation step is reversible (Scheme 3a). When the coupling of
Scheme 3. Mechanistic Investigations
a
Conditions are as follows: 0.5 mmol 1a, 1 mmol 2, 2.5 mol % [Ru(p-
cymene)Cl2]2, 0.75 mmol Cs2CO3, 3 mL of DMAc, 120 °C, 18 h;
b
yields shown are the isolated yields of the esters. Isolated yields of
c
d
the benzoic acid. Alkenyl chloride was used as the substrate. Used
e
f
1.5 mmol 2j. Contains a double-bond isomerization product. Used 5
mol % [Ru(p-cymene)Cl2]2, 10 mol % HBF4PEt3, 0.55 mmol K2CO3,
3 mL of NMP, 120 °C, 18 h. GC yields of the corresponding
g
product.
(2a−2i) and dienyl bromide (2j) were smoothly converted,
giving the (E)-product exclusively. Compound 3aa was also
generated from cinnamyl chloride, albeit in a somewhat lower
yield. The exocyclic alkene 2m gave a very low yield under the
standard conditions, but the yield could be improved to 64%
(3am) by adding a phosphine ligand that has also been used in
related Ru-catalyzed C−H arylations.11b As expected, sub-
strates with antiperiplanar hydrogen atoms, such as 2p, gave
1a and 2a was performed in the presence of D2O, no
incorporation of deuterium into 3aa was observed (Scheme
3b). In the coupling of deuterated benzoic acid [D]5-1s with
2a, no incorporation of deuterium at the alkenyl group took
place, which would have been indicative of a hydroarylation
pathway; only the expected D/H scrambling at the ortho C−H
position was observed (Scheme 3c). A kinetic isotope effect of
3543
https://doi.org/10.1021/acs.orglett.1c00956
Org. Lett. 2021, 23, 3541−3545

Organic Letters
pubs.acs.org/OrgLett
Letter
low yields due to the predominating elimination reaction. As in
related couplings, hindered substrates such as 2o gave only
unsatisfactory yields. Notably, this protocol is not suitable for
aryl halides, which is in line with previous findings that such
substrates require activating ligands at the ruthenium.11b
As can be seen from the examples in Scheme 5, the reaction
is broadly applicable in regard to the carboxylate. Benzoic acids
obtained (see the Supporting Information), confirming that
difunctionalization cannot be avoided with the current
protocol. Notably, even some acrylic acids were converted to
the corresponding dienes (3ta−3xa), demonstrating that the
reaction concept is not limited to benzoic acids alone.
In conclusion, we have demonstrated that a phosphine-free
Ru-catalyst enables the specific C−H alkenylation of benzoic
acids with (E)-alkenyl bromides, while the (Z)-isomers
eliminate under the reaction conditions. This allows the
regioselective synthesis of various (E)-2-alkenylbenzoic acids
even when starting from isomeric mixtures of alkenyl halides.
a
Scheme 5. Scope in Regard to Carboxylic Acids
ASSOCIATED CONTENT
* Supporting Information
■
sı
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.orglett.1c00956.
Experimental procedures, full analysis data for new
compounds, and copies of the NMR spectra (PDF)
AUTHOR INFORMATION
Corresponding Author
■
Lukas J. Gooßen − Evonik Chair of Organic Chemistry, Ruhr-
Universität Bochum, 44801 Bochum, Germany;
orcid.org/0000-0002-2547-3037;
Email: lukas.goossen@rub.de
Authors
Zhiyong Hu − Evonik Chair of Organic Chemistry, Ruhr-
Universität Bochum, 44801 Bochum, Germany
Florian Belitz − Evonik Chair of Organic Chemistry, Ruhr-
Universität Bochum, 44801 Bochum, Germany
Guodong Zhang − Evonik Chair of Organic Chemistry, Ruhr-
Universität Bochum, 44801 Bochum, Germany
Florian Papp − Evonik Chair of Organic Chemistry, Ruhr-
Universität Bochum, 44801 Bochum, Germany
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.orglett.1c00956
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
a
Funded by the Deutsche Forschungsgemeinschaft (DFG,
German Research Foundation) under Germany’s Excellence
Strategy (EXC-2033-390677874), RESOLV, SFB-TRR88
“3MET”, GO 853/12-1, BMBF, and the state of NRW
(Center of Solvation Science “ZEMOS”). We thank
UMICORE AG for donating chemicals and the CSC for a
fellowship to Z.H.
Conditions are as follows: 0.5 mmol 1, 1 mmol 2a, 2.5 mol % [Ru(p-
cymene)Cl2]2, 0.75 mmol Cs2CO3, 3 mL of DMAc, 120 °C, 18 h;
yields shown are isolated yields. Isolated yields of the corresponding
benzoic acid. Isolated yield of the monoarylation product. Used 5
mol % [Ru].
b
c
d
bearing various electron-donating and electron-withdrawing
substituents in ortho- or meta-positions were coupled with
cinnamyl bromide in high yields (3aa−3ia). Common
functional groups, such as halogens (F, Cl), trifluoromethyl,
ester, methoxy, and keto groups, were tolerated. Polysub-
stituted benzoic acids and naphthylcarboxylic acid also gave
good yields (3ja−3oa). Heterocyclic carboxylates such as 2-
thiophenecarboxylic acid, benzo[b]furan-2-carboxylic acid, and
1-methylindole-2-carboxylic acid were also smoothly converted
(3pa−3ra, respectively). Unsubstituted benzoic acid yielded
the mono- and dialkenylated product in a ratio of 1:1.5 (3sa).
For the para-substituted benzoic acids, 1:2 mixtures were
REFERENCES
■
(1) (a) Baird, L. J.; Timmer, M. S. M.; Teesdale-Spittle, P. H.;
Harvey, J. E. J. Org. Chem. 2009, 74, 2271−2277. (b) Grandhi, G. S.;
Selvakumar, J.; Dana, S.; Baidya, M. J. Org. Chem. 2018, 83, 12327−
12333. (c) Hua, X.; Fu, Y.-J.; Zu, Y.-G.; Wu, N.; Kong, Y.; Li, J.; Peng,
X.; Efferth, T. J. Pharm. Biomed. Anal. 2010, 52, 273−279.
(2) (a) Chen, T.; Yeung, Y.-Y. Org. Biomol. Chem. 2016, 14, 4571−
4575. (b) Martz, K. E.; Dorn, A.; Baur, B.; Schattel, V.; Goettert, M.
I.; Mayer-Wrangowski, S. C.; Rauh, D.; Laufer, S. A. J. Med. Chem.
2012, 55, 7862−7874. (c) Yang, X.; Jin, X.; Wang, C. Adv. Synth.
Catal. 2016, 358, 2436−2442.
3544
https://doi.org/10.1021/acs.orglett.1c00956
Org. Lett. 2021, 23, 3541−3545

Organic Letters
pubs.acs.org/OrgLett
Letter
(3) (a) Maryanoff, B. E.; Reitz, A. B. Chem. Rev. 1989, 89, 863−927.
(b) Blakemore, P. R. Olefination of Carbonyl Compounds by Main-
Group Element Mediators. In Comprehensive Organic Synthesis II, Vol.
1; Knochel, P., Molander, G. A., Eds.; Elsevier, 2014; pp 516−608.
(4) (a) Triandafillidi, I.; Raftopoulou, M.; Savvidou, A.; Kokotos, C.
G. ChemCatChem 2017, 9, 4120−4124. (b) da Penha, E. T.; Forni, J.
A.; Biajoli, A. F. P.; Correia, C. R. D. Tetrahedron Lett. 2011, 52,
6342−6345.
2948−2951. (f) Jagtap, R. A.; Vinod, C. P.; Punji, B. ACS Catal. 2019,
9, 431−441.
(13) Pichette Drapeau, M.; Gooßen, L. J. Chem. - Eur. J. 2016, 22,
18654−18677.
(14) For examples of Ru-catalyzed C−H hydroarylation, see:
(a) Mandal, A.; Sahoo, H.; Dana, S.; Baidya, M. Org. Lett. 2017,
19, 4138−4141. (b) Kumar, N. Y. P.; Rogge, T.; Yetra, S. R.;
Bechtoldt, A.; Clot, E.; Ackermann, L. Chem. - Eur. J. 2017, 23,
17449−17453. (c) Kumar, G. S.; Chand, T.; Singh, D.; Kapur, M.
Org. Lett. 2018, 20, 4934−4937. (d) Zhang, G.; Jia, F.; Gooßen, L. J.
Chem. - Eur. J. 2018, 24, 4537−4541. (e) Trita, A. S.; Biafora, A.;
Pichette Drapeau, M.; Weber, P.; Gooßen, L. J. Angew. Chem., Int. Ed.
2018, 57, 14580−14584. (f) Hu, Z.; Hu, X.-Q.; Zhang, G.; Gooßen,
L. J. Org. Lett. 2019, 21, 6770−6773. (g) Wu, X.; Fan, J.; Fu, C.; Ma,
S. A. Chem. Sci. 2019, 10, 6316−6321.
̂
(5) Cherry, K.; Duchene, A.; Thibonnet, J.; Parrain, J.-L.; Anselmi,
E.; Abarbri, M. Synthesis 2009, 2009, 257−270.
(6) (a) Kluwer, A. M.; Elsevier, C. J. Homogeneous Hydrogenation
of Alkynes and Dienes. In The Handbook of Homogeneous Hydro-
genation; de Vries, J. G., Elsevier, C. J., Eds.; Wiley-VCH Verlag
GmbH: Weinheim, Germany, 2006; pp 374−411. (b) Castro, C. E.;
Stephens, R. D. J. Am. Chem. Soc. 1964, 86, 4358−4363.
(15) (a) Dana, S.; Chowdhury, D.; Mandal, A.; Chipem, F. A. S.;
Baidya, M. ACS Catal. 2018, 8, 10173−10179. (b) Shi, X.-Y.; Dong,
X.-F.; Fan, J.; Liu, K.-Y.; Wei, J.-F.; Li, C.-J. Sci. China: Chem. 2015,
58, 1286−1291. (c) Miura, H.; Terajima, S.; Shishido, T. ACS Catal.
2018, 8, 6246−6254. (d) Mandal, A.; Dana, S.; Sahoo, H.; Grandhi,
G. S.; Baidya, M. Org. Lett. 2017, 19, 2430−2433.
(7) (a) Gooßen, L. J.; Deng, G.; Levy, L. M. Science 2006, 313, 662−
664. (b) Rodríguez, N.; Gooßen, L. J. Chem. Soc. Rev. 2011, 40,
5030−5048. (c) Wei, Y.; Hu, P.; Zhang, M.; Su, W. Chem. Rev. 2017,
117, 8864−8907. (d) Perry, G. J. P.; Quibell, J. M.; Panigrahi, A.;
Larrosa, I. J. Am. Chem. Soc. 2017, 139, 11527−11536.
(8) For selected reviews, see: (a) Arockiam, P. B.; Bruneau, C.;
Dixneuf, P. H. Chem. Rev. 2012, 112, 5879−5918. (b) Song, G.;
Wang, F.; Li, X. Chem. Soc. Rev. 2012, 41, 3651−3678.
(c) Kozhushkov, S. I.; Ackermann, L. Chem. Sci. 2013, 4, 886−896.
(d) Manikandan, R.; Jeganmohan, M. Chem. Commun. 2017, 53,
8931−8947. For recent articles, see: (e) Mochida, S.; Hirano, K.;
Satoh, T.; Miura, M. Org. Lett. 2010, 12, 5776−5779. (f) Mochida, S.;
Hirano, K.; Satoh, T.; Miura, M. J. J. Org. Chem. 2011, 76, 3024−
3033. (g) Ueyama, T.; Mochida, S.; Fukutani, T.; Hirano, K.; Satoh,
T.; Miura, M. Org. Lett. 2011, 13, 706−708. (h) Dana, S.; Mandal, A.;
Sahoo, H.; Mallik, S.; Grandhi, G. S.; Baidya, M. Org. Lett. 2018, 20,
716−719. (i) Mandal, A.; Mehta, G.; Dana, S.; Baidya, M. Org. Lett.
2019, 21, 5879−5883.
(16) Dolby, L. J.; Wilkins, D. C.; Frey, T. G. J. Org. Chem. 1966, 31,
1110−1116.
(17) (a) Organic Chemistry; Clayden, J., Greeves, N., Warren, S.,
Wothers, P. D., Eds.; Oxford University Press: New York, NY, 2001.
(b) Taillefer, M.; Ouali, A.; Renard, B.; Spindler, J.-F. Chem. - Eur. J.
2006, 12, 5301−5313.
(18) Hessler, J. C. Phenylacetylene. Org. Synth. 1922, 2, 67−69.
(9) (a) Ueura, K.; Satoh, T.; Miura, M. Org. Lett. 2007, 9, 1407−
1409. (b) Kumar, N. Y. P.; Bechtoldt, A.; Raghuvanshi, K.;
Ackermann, L. Angew. Chem., Int. Ed. 2016, 55, 6929−6932.
(c) Huang, L.; Biafora, A.; Zhang, G.; Bragoni, V.; Gooßen, L. J.
Angew. Chem., Int. Ed. 2016, 55, 6933−6937. (d) Biafora, A.; Khan, B.
A.; Bahri, J.; Hewer, J. M.; Gooßen, L. J. Org. Lett. 2017, 19, 1232−
1235. (e) Zhang, J.; Shrestha, R.; Hartwig, J. F.; Zhao, P. A. Nat.
Chem. 2016, 8, 1144−1151.
(10) For selected reviews, see: (a) Denmark, S. E.; Butler, C. R.
Chem. Commun. 2009, 20−33. (b) Ankner, T.; Cosner, C. C.;
Helquist, P. Chem. - Eur. J. 2013, 19, 1858−1871. For selected
articles, see (c) Cherney, A. H.; Reisman, S. E. J. Am. Chem. Soc. 2014,
136, 14365−14368. (d) Li, H.; Zhang, Z.; Shangguan, X.; Huang, S.;
Chen, J.; Zhang, Y.; Wang, J. Angew. Chem., Int. Ed. 2014, 53, 11921−
11925. (e) Olivares, A. M.; Weix, D. J. J. Am. Chem. Soc. 2018, 140,
2446−2449. (f) Swyka, R. A.; Shuler, W. G.; Spinello, B. J.; Zhang,
W.; Lan, C.; Krische, M. J. J. Am. Chem. Soc. 2019, 141, 6864−6868.
(g) Wang, C.; Rago, A. J.; Dong, G. Org. Lett. 2019, 21, 3377−3381.
(11) For selected reviews, see: (a) Shi, G.; Zhang, Y. Adv. Synth.
Catal. 2014, 356, 1419−1442. For recent articles, see: (b) Biafora, A.;
Krause, T.; Hackenberger, D.; Belitz, F.; Gooßen, L. J. Angew. Chem.,
Int. Ed. 2016, 55, 14752−14755. (c) Huang, L.; Hackenberger, D.;
Gooßen, L. J. Angew. Chem., Int. Ed. 2015, 54, 12607−12611.
(d) Huang, L.; Weix, D. J. Org. Lett. 2016, 18, 5432−5435. (e) Mei,
R.; Zhu, C.; Ackermann, L. Chem. Commun. 2016, 52, 13171−13174.
(f) Zhu, C.; Zhang, Y.; Kan, J.; Zhao, H.; Su, W. Org. Lett. 2015, 17,
3418−3421. (g) Just-Baringo, X.; Shin, Y.; Panigrahi, A.; Zarattini,
M.; Nagyte, V.; Zhao, L.; Kostarelos, K.; Casiraghi, C.; Larrosa, I.
Chem. Sci. 2020, 11, 2472−2478. (h) Takeda, D.; Yamashita, M.;
Hirano, K.; Satoh, T.; Miura, M. Chem. Lett. 2011, 40, 1015−1017.
(12) (a) Zaitsev, V. G.; Daugulis, O. J. Am. Chem. Soc. 2005, 127,
4156−4157. (b) Oi, S.; Aizawa, E.; Ogino, Y.; Inoue, Y. J. Org. Chem.
2005, 70, 3113−3119. (c) Oi, S.; Fukita, S.; Hirata, N.; Watanuki, N.;
Miyano, S.; Inoue, Y. Org. Lett. 2001, 3, 2579−2581. (d) Oi, S.;
Ogino, Y.; Fukita, S.; Inoue, Y. Org. Lett. 2002, 4, 1783−1785.
(e) Zhao, Y.; He, G.; Nack, W. A.; Chen, G. Org. Lett. 2012, 14,
3545
https://doi.org/10.1021/acs.orglett.1c00956
Org. Lett. 2021, 23, 3541−3545