Dual Cobalt and Photoredox Catalysis Enabled Redox-Neutral Annulation of 2-Propynolphenols

Article abstract of DOI:10.1002/adsc.202100221

A hydroxyl-assisted, organophotoredox/cobalt dual catalyzed annulation of 2-propynolphenols to form 2-hydroxymethyl-benzo[b]furans was developed by employing 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) as photosensitizer and CoCl₂

Full text of DOI:10.1002/adsc.202100221

UPDATES
DOI: 10.1002/adsc.202100221
Dual Cobalt and Photoredox Catalysis Enabled Redox-Neutral
Annulation of 2-Propynolphenols
+
a
+b
a,
a
c
Yao Zhu, Yong-Qin He, Wan-Fa Tian, * Mei Wang, Zhao-Zhao Zhou,
a
a
a,
Xian-Rong Song, Hai-Xin Ding, and Qiang Xiao *
a
Institute of Organic Chemistry, Jiangxi Science & Technology Normal University, Key Laboratory of Organic Chemistry,
Jiangxi Province, Nanchang, 330013, People’s Republic of China
E-mail: tianwf12@lzu.edu.cn; xiaoqiang@tsinghua.org.cn
School of Pharmaceutical Science, Nanchang University, Nanchang, 330006, People’s Republic of China
Department of Chemistry, Nanchang Normal University, Nanchang, People’s Republic of China
b
c
+
These authors contributed equally.
Manuscript received: February 18, 2021; Revised manuscript received: May 20, 2021;
Version of record online: ■■■, ■■■■
Supporting information for this article is available on the WWW under https://doi.org/10.1002/adsc.202100221
[4]
[5]
[6]
Shigehisa, Pronin, and Zhu suggested that the
radical or collapsed alkylcobalt(III) intermediate could
be further transformed into a carbocation or alkylco-
balt(IV) species via single electron oxidation process
in the presence of N-fluorocollidinium salt or excited
photocatalyst, and which can be captured by nucleo-
philes (Scheme 1a, III). By applying these strategies, a
variety of carbon-carbon or carbon-heteroatom bonds
Abstract: A hydroxyl-assisted, organophotoredox/
cobalt dual catalyzed annulation of 2-propynolphe-
nols to form 2-hydroxymethyl-benzo[b]furans was
developed by employing 1,2,3,5-tetrakis(carbazol-9-
yl)-4,6-dicyanobenzene (4CzIPN) as photosensitizer
and CoCl (PPh ) /5,5’-dimethyl-2,2’-bipyridine as
cobalt catalytic precursor. Various substrates and
functional groups were tolerated. The practical
applications of this reaction were further demon-
strated by enlarged gram-scale and various deriva-
tions for complex heterocycles. Primary mechanistic
studies suggested the involvement of cobalt-hydride
mediated hydrogen atom transfer (HAT) process.
2
3 2
[1]
have been constructed. Despite these great advances,
the current HAT catalysis limits their substrates on
alkenes. Alkynes, however, are rarely reported to
[7]
achieve hydrofunctionalization via HAT strategies.
Catalytic cyclization of o-alkynylphenol is the most
straightforward and atom-economic method to con-
[8]
struct benzo[b]furan, which is widely existed in
[9]
biologically active molecules. The traditional syn-
thetic strategy is electrophilic activation of carbon-
carbon triple bonds by Lewis acidic metals (e.g. Ir, Rh,
Pd, Au, Ag, Cu, Zn, In and others), followed by a
nucleophilic attack on alkyne to realize the cyclization.
It is of note that cobalt-based catalyst is rarely used to
Keywords: Photoredox catalysis; cobalt; hydrogen
atom transfer (HAT); redox-neutral; 2-propynolphe-
nols
The first-row transition-metal hydrides (L MÀ H) medi- achieve such annulation.
n
ated hydrogen atom transfer (HAT) reaction has
Merging photoredox catalysis with transition-metal
recently attracted significant attentions in organic catalysis has been identified as vital ways to achieve
[1]
synthesis. A key step in these reactions is chemo- novel and unique transformations under mild
[10]
selective generation of a radical/metal cage. The conditions. Recently, we developed an visible-light-
radical could either escape from the cage and thus be promoted iridium/cobalt dual catalytic system for
[2]
captured by radicalophiles or recombine with metal efficient construction 2,3-dihydrobenzofurans from 2-
to form the cage-collapsed organometallics complex propynolphenols via tandem semi-hydrogenation and
[
11]
which would undergo transmetalation with other intramolecular cyclization processes (Scheme 1b).
metals and thus introducing new functionalities.
A
[3]
low-valent cobalt catalyzed phenolic OÀ H activation
Catalysts based on cobalt are among the most studied or a further hydrogenation of (Z)-alkene followed by
systems for these types of transformations and proved phenolic oxygen substitution on cobalt center is
[2a–l]
extremely versatile (Scheme 1a, I and II).
Recently, supposed to contribute to the cyclization. Based on this
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Table 1. Reaction optimization.
Scheme 1. Cobalt-hydride mediated HAT catalysis and photo-
redox/cobalt catalyzed cyclization of 2-propynolphenols.
work, we wondered if benzo[b]furan could be directly
formed from o-alkynylphenol via photoredox/cobalt
dual catalysis with an avoided semi-hydrogenation
process. As an update of our previous work, we herein
would like to report the successful realization of this
goal by employing an organophotoredox/cobalt dual
catalytic system with 1,2,3,5-tetrakis(carbazol-9-yl)-
4
,6-dicyanobenzene (4CzIPN) as photosensitizer
(Scheme 1c). More importantly, primary mechanism
studies suggest the reaction involves a novel cobalt-
hydride mediated HAT pathway, which is highly
different from our previous work. It is worth noting
that this photoredox/Co dual catalytic system obviates
the using of stoichiometric strong oxidants such as N-
fluorocollidinium salt and high reducing silane reagent,
which are generally indispensable for most metal-
hydride mediated HAT system.
[
a]
1
a (0.1 mmol), PS (1 mol%), [Co] (10 mol%), Ligand
(15 mol%), i-Pr NEt (3.0 equiv.), additive (20 mol%), solvent
2
(2.0 mL), irradiation with blue LEDs for 6 h, the reaction
mixture was filtered by a small pad of silica gel after
irradiation and H NMR yield was reported using
Cl CHCHCl as an internal standard.
DBU=1.2 equiv.
EtOH=4.0 mL.
DBU=2.0 equiv.
4CzIPN=2 mol%.
isolate yield.
no i-Pr NEt.
i-Pr NEt=5.0 equiv.
DBU=5.0 equiv.
in dark. PS=photosensitizer.
1
We started to verify our hypothesis by using similar
2
2
[11]
[
[
[
[
[
[
[
[
b]
c]
d]
e]
f]
conditions in our previous work, that is, selecting 1a
as the model substrate, Ir[dF(CF )ppy] (dtbbpy)PF as
3
2
6
photocatalyst, 4,4’-di-tert-butyl-2,2’-bipyridine (L1) as
ligand, and i-Pr NEt as radical sacrificial in n-propyl
2
alcohol at room temperature (table 1, entry 1). Unfortu-
nately, none of corresponding benzo[b]furan 2a was
detected. Other cobalt catalysts were then explored
g]
h]
i]
2
2
(
entries 2–3). To our great surprise, CoCl (PPh3)2
2
[j]
displayed reactivity on catalyzing the cyclization to
afford 2a in 34% yield. The effects of bases were
subsequently investigated (entries 4–6). Among them,
DBU displayed a higher yield up to 44%. Solvent to organic dye, 4CzIPN (E
investigation revealed that EtOH is the best choice, SCE), and increasing the amount of photosensitizer
PC*/PCÀ
= +1.43 V vs
[12]
delivering 2a in 56% yield (entries 7–9). Increasing to 2 mol% (entry 16). In absence of i-Pr NEt (E = +
2
ox
the amount of base and solvent further elevated the 0.75 V vs SCE, see SI) or DBU (E = +1.28 V vs
ox
[13]
yield up to 74% (entries 10, 11). The ligand screening SCE)
decreased the yield to 36% and 60%
showed that 5,5’-dimethyl-2,2’-bipyridine (L3) is the respectively (entries 17–18). From redox-potential
best choice (entries 12–15). Finally, 89% isolated yield analysis, DBU is capable of transferring electron to
was obtained by changing the iridium photosensitizer excited photosensitizer (4CzIPN*), so it may not only
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play the role of base but also partially serve as an decreased yield of 55%. Other unsymmertric diphenyl-
electron donor reagent. Adding 5 equivalents of i- methanols with electron-deficient groups on para-
Pr NEt or DBU to the system decreased the yield to position of phenyls generated the products in good
2
2
2% and 12%, respectively (entries 19–20). The yields (2p–2q, 75–78%). Ortho-fluoronated substrate
control experiments revealed that visible-light, photo- 1r delivered the corresponding product 2r in 67%
sensitizer, cobalt complexes were all essential for the yield. In addition, the phenylnaphthalenyl methanol
successful transformation (entries 21–23).
resulted in good reaction efficiency (2s, 89%). It’s
With the optimized conditions in hand, the substrate obvious that the heterocycle of thienyl was also
scope of this transformation was then investigated compatible under the conditions to provide the corre-
(Table 2). First, the propargylic alcohols bearing sponding product 2t in 78% yield. Tertiary propargylic
various substituents on the phenolic ring were studied. alcohols with arylalkyl methanol or dialkyl methanols
Notably, both electron-deficient groups, such as fluo- also reacted well under the standard conditions to give
rine, chlorine, bromine and ester, and electron-donating the corresponding products in excellent yields (2u–
group, such as methyl were compatible to afford the 2w, 80–94%).
products in excellent yields (2b–2g, 78–88%). The
To further disclose the potential synthetic applica-
substrate bearing two fluorine atoms on the C4 and C5 tions of the reaction, a series of derivatizations were
positions of phenolic ring gave the product 2h in 73% conducted (Scheme 2). A gram-scale reaction of 1a
yield.
was firstly performed under standard conditions,
Next, the influence of the substituents on the affording the product 2a (1.20 g) in 80% yield.
diphenylmethanol was investigated. Obviously, prop- Furthermore, 2-benzofuranmethanol has been identi-
argylic alcohols with electron-donating group on the fied as a versatile platform for further transformations.
para-position of phenyls (2l, 92%) delivered higher For example, the nucleophiles, such as diphenylphos-
yield than electron-withdrawing groups (2i–2k, 72– phine oxide and indole, could be feasible installed at
8
5%), illustrating that the electronic effect on the yield. C3 position of the 2a to afford the products 4 and 6
Strong electron-withdrawing groups, such as fluorine under the catalysis of TfOH and TsOH·H O, respec-
2
and trifluoromethyl, on meta-position of the phenyls tively. In addition, a regioselective benzylic phosphi-
afforded the products 2m in 86% yield and 2n in 83% nated product of 7 was obtained under the catalysis of
yield, respectively. Interestingly, replacement of one TsOH·H O at a lower temperature of 15°C. Consider-
2
fluorine atom by methoxyl group afforded 2o in a ing the great importance of benzo[b]furan, indole, and
phosphorous on pharmaceuticals’ activity, these prod-
ucts provide foundation for further bioactive mole-
cules’ investigation.
[a]
[14]
Table 2. Substrate scope.
To verify the role of alcoholic hydroxyl group in
the substrate, several control experiments were con-
ducted (Scheme 3a). Protecting the alcoholic hydroxyl
group with methyl (1x) could not afford any desired
product, but, interestingly, the demethoxyl product 2x’
[a]
Reaction condition: 1 (0.1 mmol), 4CzIPN (2 mol%), CoCl2
Ph P)2 (10 mol%), L3 (15 mol%), i-Pr NEt (3.0 equiv.),
(
3
2
DBU (2.0 equiv.), EtOH (4.0 mL), irradiation with blue
LEDs for 6 h, isolated yield was reported.
Scheme 2. Gram-scale reaction and further transformations.
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Meanwhile, we also conducted the experiments that
using prepared (Z)-8 and (E)-8 as substrates under
standard conditions, but none of reactions were
occurred (Scheme S6). Since (Z)-8 was proved to be
an intermediate in our previous work (Scheme 1b), we
thus deduced that this work should proceed via a
[11]
highly different mechanism from our previous work.
Third, the light on/off experiment was conducted
Figure 1b). The results revealed that the reaction
(
efficiently took place under visible-light irradiation
and was suppressed under dark, suggesting the inter-
secting of photoredox catalysis with cobalt catalysis.
Next, the luminescent quenching experiments were
conducted (Figure S7). 1a, CoCl (PPh ) , and DBU,
2
3 2
showed only slight quenching phenomena, but i-
Pr NEt displayed an obvious quenching phenomenon.
2
Scheme 3. Control experiments.
Meanwhile, cobalt complex CoCl (L3) , which formed
2
2
in a 1:2 mixture of CoCl (PPh ) with L3 in EtOH and
2
3 2
was obtained in 29% yield with 58% of 1x recovery determined via HRMS (see Figure S1), showed a
eq. 1). Next, 2x was synthesized and tested under similar quenching rate with i-Pr NEt. These experi-
(
2
standard conditions to verify whether the demeth- ments suggest that single electron transfer (SET) of the
oxylation occurred after ring closure (eq. 2). However, exited photocatalyst 4CzIPN* dominantly occurs with
no demethoxylation was observed under the condi- i-Pr NEt or the cobalt complex. The thermodynamic
2
tions, expelling the above-mentioned possibility. Un- feasibility of the photoinduced SET was analyzed by
fortunately, the pathway of the demethoxylation the oxidation-reduction potentials. The oxidation po-
remains obscure at this stage. Moreover, replacing the tential and reduction potential of 4CzIPN* were
alcoholic hydroxyl group by methyl (1y) afforded the reported to be À 1.18 V vs SCE and +1.43 V vs SCE,
[12]
corresponding products only in trace amount (<5% respectively. Obviously, the 4CzIPN* is capable of
yield, eq. 3). Since the reaction efficiency were greatly abstracting
electrons
from
i-Pr NEt
2
iÀ Pr2NEt/iÀ Pr2Net
*
+
retarded when the alcoholic hydroxyl is protected or (E
absent, we therefore deduced that the alcoholic or transferring electron to the cobalt complex (E
= +0.75 V vs SCE, see Figure S8)
Co(II)/
Co(I)
hydroxyl group should play a significant role of
chelation.
=À 1.05 V vs SCE, see Figure S9).
[10d]
Based on the above results and literature reports,
Mechanistic studies were conducted to gain more a plausible reaction mechanism is proposed in
insights on the reaction. First, adding 2 equiv. of Scheme 4. The photosensitizer 4CzIPN is initially
2
,2,6,6-tetramethyl-1-piperidineoxyl (TEMPO) to the irradiated by blue LEDs to its excited state 4CzIPN*.
standard reaction completely suppressed the trans- Then, two pathways might be involved in reduction of
formation, suggesting that free radical might involve in Co(II) to Co(I). In path a, 4CzlPN* is reductively
the catalytic cycle. (Scheme 3b). Second, monitoring quenched by i-Pr NEt to afford reductive photosensi-
2
of the synthesis of 2a showed no apparent stable
intermediates, but a byproduct of semi-hydrogenation
of 1a to alkene (Z)-8 was detected, suggesting that an
active CoÀ H species, as well as a key alkenylcobalt
intermediate should involve in the reaction (Figure 1a).
Figure 1. a) Yield/time diagram for preparation of 2a (left) and
b) light on/off experiments (right).
Scheme 4. Plausible reaction mechanism.
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*
À
PC/PC
*
À
[12]
tizer [4CzIPN] (E
radical cation of i-Pr NEt, and the former transfers one
=À 1.24 V vs SCE) and ethanol were added to the reaction tube via syringe under Ar
atmosphere. The reaction mixture was stirred for 6 h at Wattcas
2
Parallel Light Reactor System (Blue LED Light source, 10 W
every position) at ambient temperature (the temperature range
from 28°C to 32°C). Finally, the solvent was removed in
electron to Co(II) complex to produce the Co(I) species
and regenerate 4CzIPN. Alternatively (path b),
4
CzIPN* is oxidative quenched by Co(II) to afford
*
+
vacuum and the residue was purified by column chromatog-
raphy on silica gel to afford the compound 2.
Co(I) and the oxidative photosensitizer [4CzIPN] .
*
+
PC
*
+/PC
[12]
[4CzlPN]
(E
= +1.49 V vs SCE)
would
subsequently abstract an electron from i-Pr NEt to
2
regenerate 4CzIPN (path b). The generated Co(I) is
+
[15] Acknowledgements
quickly trapped by H to give Co(III)-H species.
Subsequently, a Co(III)-H mediated HAT reaction
We acknowledge the National Natural Science Foundation of
might occur to form a radical cage consisting of radical China (No. 21676131, No. 21462019, and No. 22001101), the
species 9 and an Co(II) catalyst. Reacting with Co(III)- Science Foundation of Jiangxi Province (No. 20143ACB20012,
À
+
H or accepting an electron (e ) and a proton (H ) by 9 20202BAB213003), Education Department of Jiangxi Province
(No. GJJ190616), and Jiangxi Science & Technology Normal
would afford the byproduct (Z)-8 and release a Co(II)
species. Next, substitution between phenolic
University (No. 2018BSQD024, Doctor Startup Fund) for
financial support.
a
hydroxyl group and cobalt center under basic condition
might occur to form the intermediate 10, followed by a
radical capture to afford Co(III) species 11. Consider-
ing the intersecting of photocatalysis with cobalt
catalysis from light on/off experiments, as well as
References
[
1] a) S. W. Crossley, C. Obradors, R. M. Martinez, R. A.
Shenvi, Chem. Rev. 2016, 116, 8912–9000; b) S. A.
Green, S. W. M. Crossley, J. L. M. Matos, S. Vásquez-
Céspedes, S. L. Shevick, R. A. Shenvi, Acc. Chem. Res.
2018, 51, 2628–2640; c) S. H. Kyne, G. Lefèvre, C.
Ollivier, M. Petit, V.-A. Ramis Cladera, L. Fensterbank,
Chem. Soc. Rev. 2020, 49, 8501–8542; d) S. L. Shevick,
C. V. Wilson, S. Kotesova, D. Kim, P. L. Holland, R. A.
Shenvi, Chem. Sci. 2020, 11, 12401–12422.
[10g]
literature reports,
by 4CzIPN* might occure to give Co(IV) intermediate
2, which would undergo a reductive ellimination
a single electron oxidation of 11
1
process to furnish 2a and Co(II). Finally, to close both
catalytic cycles, reduction of Co(II) by reductive
*
À
photosensitizer [4CzIPN] would regenerate the Co(I)
catalyst and 4CzIPN. We reasoned that the alcoholic
hydroxyl group should play a vital role of chelation to
stabilize the intermediate or direct the selective
addition of Co(III)-H to alkynes.
In conclusion, a catalytic system in combination of
cobalt catalysis and an organic dye, 4CzIPN, promote
a novel photochemical intramolecular cyclization proc-
ess. Using the Co/4CzIPN catalytic system, 2-meth-
anolbenzofurans are prepared in good to excellent
yields from tertiary alkynlalcohols. The inevitable role
of alcoholic hydroxyl group and its diverse functions
for highly selective phosphorylation and indolation of
[2] For selected examples on cobalt: a) J. Waser, B. Gaspar,
H. Nambu, E. M. Carreira, J. Am. Chem. Soc. 2006, 128,
1
1693–11712; b) B. Gaspar, E. M. Carreira, Angew.
Chem. 2008, 120, 5842–5844; Angew. Chem. Int. Ed.
008, 47, 5758–5760; c) S. W. Crossley, F. Barabe, R. A.
2
Shenvi, J. Am. Chem. Soc. 2014, 136, 16788–16791;
d) S. M. King, X. Ma, S. B. Herzon, J. Am. Chem. Soc.
2
014, 136, 6884–6887; e) X. Ma, S. B. Herzon, Chem.
Sci. 2015, 6, 6250–6255; f) S. A. Green, J. L. Matos, A.
Yagi, R. A. Shenvi, J. Am. Chem. Soc. 2016, 138,
1
2779–12782; g) X. Ma, S. B. Herzon, J. Am. Chem.
2
-benzofuranylmethanols at benzylic or C3 position
Soc. 2016, 138, 8718–8721; h) X. Ma, H. Dang, J. A.
Rose, P. Rablen, S. B. Herzon, J. Am. Chem. Soc. 2017,
were demonstrated. Furthermore, the proposed hydro-
gen atom transfer mechanisms are supported by the
detecting of semi-hydrogenated product (Z)-8, radical
capture experiment and light on/off experiment. Fur-
ther mechanism studies with synthetic exploration of
this catalytic system are underway in our laboratory.
1
39, 5998–6007; i) X. Shen, X. Chen, J. Chen, Y. Sun,
Z. Cheng, Z. Lu, Nat. Commun. 2020, 11, 783; j) S. Shi,
J. L. Kuo, T. Chen, J. R. Norton, Org. Lett. 2020, 22,
6
171–6176; k) L. Song, N. Fu, B. G. Ernst, W. H. Lee,
M. O. Frederick, R. A. DiStasio, S. Lin, Nat. Chem.
020, 12, 747–754; l) Y. Kamei, Y. Seino, Y. Yamaguchi,
2
Experimental Section
T. Yoshino, S. Maeda, M. Kojima, S. Matsunaga, Nat.
Commun. 2021, 12, 966; for selected examples on iron:
m) T. J. Barker, D. L. Boger, J. Am. Chem. Soc. 2012,
General Procedure for the Synthesis of
2
-hydroxymethylbenzo[b]furans 2
1
34, 13588–13591; n) J. C. Lo, J. Gui, Y. Yabe, C.-M.
Pan, P. S. Baran, Nature 2014, 516, 343; o) J. H. Gui,
C. M. Pan, Y. Jin, T. Qin, J. C. Lo, B. J. Lee, S. H.
Spergel, M. E. Mertzman, W. J. Pitts, T. E. La Cruz,
M. A. Schmidt, N. Darvatkar, S. R. Natarajan, P. S.
Baran, Science 2015, 348, 886–891; p) J. Zheng, D.
To a Schlenk tube containing a stirring bar was added 4CzIPN
(
0.002 mmol, 2 mol%), Co(PPh ) Cl (0.01 mmol, 10 mol%),
3 2 2
5
2
,5’-dimethyl-2,2’-bipyridine (L3, 0.015 mmol, 15 mol%), and
-propynolphenol 1 (0.10 mmol, 1.0 equiv.). Then, i-Pr EtN
2
(0.3 mmol, 3.0 equiv.), DBU (0.2 mmol, 2.0 equiv.), and 4.0 mL
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Wang, S. Cui, Org. Lett. 2015, 17, 4572–4575; q) Y.
Shen, J. Qi, Z. Mao, S. Cui, Org. Lett. 2016, 18, 2722–
725; r) S. A. Green, S. Vasquez-Cespedes, R. A. Shen-
vi, J. Am. Chem. Soc. 2018, 140, 11317–11324; s) J. Qi,
J. Zheng, S. Cui, Org. Lett. 2018, 20, 1355–1358; t) M.
Saladrigas, C. Bosch, G. V. Saborit, J. Bonjoch, B.
Bradshaw, Angew. Chem. 2018, 130, 188–192; Angew.
Chem. Int. Ed. 2018, 57, 182–186; u) L. Yang, W. W. Ji,
E. Lin, J. L. Li, W. X. Fan, Q. Li, H. Wang, Org. Lett.
R. H. Crabtree, Org. Lett. 2005, 7, 5437–5440; c) Y.
Liang, S. Tang, X.-D. Zhang, L.-Q. Mao, Y.-X. Xie, J.-H.
Li, Org. Lett. 2006, 8, 3017–3020; d) M. Nakamura, L.
Ilies, S. Otsubo, E. Nakamura, Angew. Chem. 2006, 118,
958–961; Angew. Chem. Int. Ed. 2006, 45, 944–947;
e) N. Isono, M. Lautens, Org. Lett. 2009, 11, 1329–1331;
f) O. S. Morozov, A. V. Lunchev, A. A. Bush, A. A.
Tukov, A. F. Asachenko, V. N. Khrustalev, S. S. Zales-
skiy, V. P. Ananikov, M. S. Nechaev, Chem. Eur. J. 2014,
20, 6162–6170; g) Z. Xia, O. Khaled, V. Mouriès-
Mansuy, C. Ollivier, L. Fensterbank, J. Org. Chem. 2016,
81, 7182–7190; h) L. Alonso-Marañón, M. M. Martínez,
L. A. Sarandeses, E. Gómez-Bengoa, J. Pérez Sestelo, J.
Org. Chem. 2018, 83, 7970–7980; i) Z. Rong, K. Gao, L.
Zhou, J. Lin, G. Qian, RSC Adv. 2019, 9, 17975–17978.
[9] a) R. Naik, D. S. Harmalkar, X. Xu, K. Jang, K. Lee,
Eur. J. Med. Chem. 2015, 90, 379–393; b) A. Radadiya,
A. Shah, Eur. J. Med. Chem. 2015, 97, 356–376.
2
2
018, 20, 1924–1927; v) Y. Zhang, C. Huang, X. Lin, Q.
Hu, B. Hu, Y. Zhou, G. Zhu, Org. Lett. 2019, 21, 2261–
264; w) M. Saladrigas, J. Puig, J. Bonjoch, B.
2
Bradshaw, Org. Lett. 2020, 22, 8111–8115; x) B. Wu, R.
Zhu, ACS Catal. 2020, 10, 510–515; for selected
examples on manganese: y) K. Iwasaki, K. K. Wan, A.
Oppedisano, S. W. Crossley, R. A. Shenvi, J. Am. Chem.
Soc. 2014, 136, 1300–1303; z) S. A. Green, T. R. Huff-
man, R. O. McCourt, V. van der Puyl, R. A. Shenvi, J.
Am. Chem. Soc. 2019, 141, 7709–7714; aa) Y.-Y. Wang, [10] for selected reviews, see: a) D. C. Fabry, M. Rueping,
J. W. Bode, J. Am. Chem. Soc. 2019, 141, 9739–9745;
for selected example on nickel: ab) P. Song, S. Zhu,
ACS Catal. 2020, 10, 13165–13170.
Acc. Chem. Res. 2016, 49, 1969–1979; b) W.-J. Zhou,
Y.-H. Zhang, Y.-Y. Gui, L. Sun, D.-G. Yu, Synthesis
2018, 50, 3359–3378; c) A. Gualandi, M. Anselmi, F.
Calogero, S. Potenti, E. Bassan, P. Ceroni, P. G. Cozzi,
Org. Biomol. Chem. 2021, 19, 3527–3550; for selected
examples on photoredox/cobalt dual catalysis, see:
d) S. M. Thullen, T. Rovis, J. Am. Chem. Soc. 2017, 139,
15504–15508; e) D. Kalsi, S. Dutta, N. Barsu, M.
Rueping, B. Sundararaju, ACS Catal. 2018, 8, 8115–
8120; f) M. J. González, B. Breit, Chem. Eur. J. 2019,
25, 15746–15750; g) J.-C. Grenier-Petel, S. K. Collins,
ACS Catal. 2019, 9, 3213–3218; h) D. Kalsi, N. Barsu,
S. Chakrabarti, P. Dahiya, M. Rueping, B. Sundararaju,
Chem. Commun. 2019, 55, 11626–11629; i) Q.-Y. Meng,
T. E. Schirmer, K. Katou, B. König, Angew. Chem. 2019,
131, 5779–5784; Angew. Chem. Int. Ed. 2019, 58, 5723–
5728; j) P. Rai, K. Maji, B. Maji, Org. Lett. 2019, 21,
3755–3759; k) W. F. Tian, Y. Q. He, X. R. Song, H. X.
Ding, J. Ye, W. J. Guo, Q. Xiao, Adv. Synth. Catal. 2020,
362, 1032–1038.
[
3] a) J. L. M. Matos, S. Vásquez-Céspedes, J. Gu, T.
Oguma, R. A. Shenvi, J. Am. Chem. Soc. 2018, 140,
1
6976–16981; b) S. L. Shevick, C. Obradors, R. A.
Shenvi, J. Am. Chem. Soc. 2018, 140, 12056–12068.
4] a) H. Shigehisa, T. Aoki, S. Yamaguchi, N. Shimizu, K.
Hiroya, J. Am. Chem. Soc. 2013, 135, 10306–10309;
b) H. Shigehisa, N. Koseki, N. Shimizu, M. Fujisawa, M.
Niitsu, K. Hiroya, J. Am. Chem. Soc. 2014, 136, 13534–
[
1
3537; c) H. Shigehisa, T. Ano, H. Honma, K. Ebisawa,
K. Hiroya, Org. Lett. 2016, 18, 3622–3625; d) H.
Shigehisa, M. Hayashi, H. Ohkawa, T. Suzuki, H.
Okayasu, M. Mukai, A. Yamazaki, R. Kawai, H.
Kikuchi, Y. Satoh, A. Fukuyama, K. Hiroya, J. Am.
Chem. Soc. 2016, 138, 10597–10604; e) S. Date, K.
Hamasaki, K. Sunagawa, H. Koyama, C. Sebe, K.
Hiroya, H. Shigehisa, ACS Catal. 2020, 10, 2039–2045;
f) K. Ebisawa, K. Izumi, Y. Ooka, H. Kato, S. Kanazawa,
S. Komatsu, E. Nishi, H. Shigehisa, J. Am. Chem. Soc. [11] W.-F. Tian, Y. Zhu, Y.-Q. He, M. Wang, X.-R. Song, J.
020, 142, 13481–13490; g) T. Nagai, N. Mimata, Y. Bai, Q. Xiao, Adv. Synth. Catal. 2021, 363, 730–736.
Terada, C. Sebe, H. Shigehisa, Org. Lett. 2020, 22, [12] E. Speckmeier, T. G. Fischer, K. Zeitler, J. Am. Chem.
522–5527. Soc. 2018, 140, 15353–15365.
5] E. E. Touney, N. J. Foy, S. V. Pronin, J. Am. Chem. Soc. [13] D. Nicewicz, H. Roth, N. Romero, Synlett 2015, 27,
018, 140, 16982–16987. 714–723.
6] a) X. L. Zhou, F. Yang, H. L. Sun, Y. N. Yin, W. T. Ye, [14] a) B. R. Smith, C. M. Eastman, J. T. Njardarson, J. Med.
2
5
[
[
2
R. Zhu, J. Am. Chem. Soc. 2019, 141, 7250–7255; b) R.
Zhu, Synlett 2019, 30, 2015–2021; c) H.-L. Sun, F. Yang,
W.-T. Ye, J.-J. Wang, R. Zhu, ACS Catal. 2020, 10,
Chem. 2014, 57, 9764–9773; b) E. Vitaku, D. T. Smith,
J. T. Njardarson, J. Med. Chem. 2014, 57, 10257–10274;
c) M. D. Delost, D. T. Smith, B. J. Anderson, J. T.
Njardarson, J. Med. Chem. 2018, 61, 10996–11020.
4
983–4989.
[7] D. P. Estes, J. R. Norton, S. Jockusch, W. Sattler, J. Am. [15] a) B. Chen, L. Z. Wu, C. H. Tung, Acc. Chem. Res. 2018,
Chem. Soc. 2012, 134, 15512–15518.
8] a) A. Fürstner, P. W. Davies, J. Am. Chem. Soc. 2005,
51, 2512–2523; b) H. Wang, X. Gao, Z. Lv, T. Abdelilah,
A. Lei, Chem. Rev. 2019, 119, 6769–6787; c) M. Kojima,
S. Matsunaga, Trends Chem. 2020, 2, 410–426.
[
1
27, 15024–15025; b) X. Li, A. R. Chianese, T. Vogel,
Adv. Synth. Catal. 2021, 363, 1–7
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UPDATES
Dual Cobalt and Photoredox Catalysis Enabled Redox-
Neutral Annulation of 2-Propynolphenols
Adv. Synth. Catal. 2021, 363, 1–7
Y. Zhu, Y.-Q. He, W.-F. Tian*, M. Wang, Z.-Z. Zhou, X.-R.
Song, H.-X. Ding, Q. Xiao*