Synthesis of Functionalized Indole-1-oxide Derivatives via Cascade Reactions of Allenynes and tBuONO

Article abstract of DOI:10.1021/acs.orglett.9b00968

This paper presents a novel access to 5-oxo-2H-benzo[g]indole-1-oxides/functionalized naphthalene-1,2-diones via the cascade reaction of allenynes with alcohols/amines and ^tBuONO without using any catalyst. Mechanistically, the formation of 5-oxo-2H-benzo[g]indole-1-oxides involves a cascade process combining [2 + 2] cycloaddition, 1,6-addition, and ring expansion of the in situ formed cyclobutene intermediate. The construction of naphthalene-1,2-diones should undergo a ring-opening pathway. Moreover, the utility of benzoindole-1-oxides was demonstrated by their easy conversion into pharmaceutically significant 1H-benzo[g]indol-5-ol derivatives.

Full text of DOI:10.1021/acs.orglett.9b00968

Letter
pubs.acs.org/OrgLett
Cite This: Org. Lett. XXXX, XXX, XXX−XXX
Synthesis of Functionalized Indole-1-oxide Derivatives via Cascade
t
Reactions of Allenynes and BuONO
Yan He,* Tian Feng, and Xuesen Fan*
Henan Key Laboratory of Organic Functional Molecules and Drug Innovation, Key Laboratory for Yellow River and Huai River
Water Environmental Pollution Control, Ministry of Education, Collaborative Innovation Center of Henan Province for Green
Manufacturing of Fine Chemicals, School of Environment, School of Chemistry and Chemical Engineering, Henan Normal
University, Xinxiang, Henan 453007, China
S
* Supporting Information
ABSTRACT: This paper presents a novel access to 5-oxo-
2H-benzo[g]indole-1-oxides/functionalized naphthalene-1,2-
diones via the cascade reaction of allenynes with alcohols/
t
amines and BuONO without using any catalyst. Mechanis-
tically, the formation of 5-oxo-2H-benzo[g]indole-1-oxides
involves a cascade process combining [2 + 2] cycloaddition,
1,6-addition, and ring expansion of the in situ formed
cyclobutene intermediate. The construction of naphthalene-1,2-diones should undergo a ring-opening pathway. Moreover,
the utility of benzoindole-1-oxides was demonstrated by their easy conversion into pharmaceutically significant 1H-
benzo[g]indol-5-ol derivatives.
he indole unit is a key block of various natural products,
preparation of various kinds of organic compounds.5,6 From this
1
Telectronic materials, and pharmaceuticals. Among various aspect, a novel method for the synthesis of cyclobutanol-fused 2-
nitronaphthalen-1-ols (I, Scheme 1, (1)) through tandem
indole derivatives, indole-1-oxide is present widely in alkaloids
possessing powerful biological activities. For example, avrain-
villamide and stephacidin B possess a strong inhibitory effect on
the growth of testosterone-dependent prostate and breast cancer
cell lines.2 As another example, waikialoid A showed potent
inhibition to biofilm formation, thus providing a novel and
effective approach to combating refractory infections (Figure
1).3
Scheme 1. Varied Reactions of Benzene-Linked Allene-Yne
with TBN in Different Solvents
reactions of benzene-linked allene-ynes, prepared in three
routine steps from commercial 2-bromobenzaldehydes,5h,6b,7
t
with BuONO (tert-butyl nitrite, TBN) using DCE as the
Figure 1. Alkaloids containing the indole-1-oxide moiety.
reaction medium, has been disclosed by our group.8 During that
study, we serendipitously found that when the above-mentioned
reaction was carried out in ethanol instead of DCE, an
unexpected cascade reaction occurred to construct an indole-
1-oxide derivative (Scheme 1, (2)). Herein, we report the results
in detail.
Due to their importance, a number of methods based on
different synthetic strategies have been developed for the
synthesis of indole-1-oxide and its derivatives. Traditionally,
they were prepared via oxidation of indoles4 or zinc-promoted
intramolecular reductive condensation of 1-(2-nitrophenyl)-2-
ones.2a,d Most of these reported methods are efficient and
reliable, but some of them still suffer from tedious synthetic
procedures, unselective oxidation, generation of hazardous
wastes, or use of expensive/toxic metal catalysts. Thus, the
development of more sustainable and straightforward methods
for the construction of indole-1-oxides is urgently needed.
Meanwhile, allene and allene-yne derivatives were found to
possess rich and diverse reactivity and have thus been used in the
At first, 1-(2-(phenylethynyl)phenyl)buta-2,3-dien-1-one
(1a) was used as the substrate to react with TBN (3, 2 equiv)
in ethanol (2a, 2 mL) at rt for 3 h, from which the formation of
the initially desired cyclobutanol-fused 2-nitronaphthalen-1-ol
(I) was not observed. Instead, 2-ethoxy-5-oxo-2-phenyl-3,5-
dihydro-2H-benzo[g]indole-1-oxide (4a), the structure of
Received: March 19, 2019
© XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.9b00968
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
a b
,
which was confirmed by a single-crystal X-ray diffraction study,
was formed in 76% yield (Table 1, entry 1). Notwithstanding
Scheme 2. Scope of Substrates for the Formation of 4 (1)
a
Table 1. Optimization Studies
b
entry
catalyst
T (°C)
time (h)
yield of 4a (%)
c
1
rt
rt
rt
rt
rt
rt
rt
rt
50
rt
rt
3
3
3
3
3
3
3
3
3
6
3
76
80
75
80
41
76
65
61
76
81
82
2
d
3
e
4
f
5
6
7
8
9
10
11
HOAc
TFA
TfOH
g
a
Reaction conditions: 1a (0.5 mmol), EtOH (10 mmol, 0.6 mL),
b
c
d
TBN (1 mmol), rt, air, 3 h. Isolated yield. EtOH (2 mL). EtOH (5
mmol, 0.3 mL). TBN (1.5 mmol). TBN (0.5 mmol). 95% EtOH
(10 mmol, 0.61 mL) was used.
e
f
g
that compound I was not obtained, the construction of 4a owns
two notable features. First, it reveals an unprecedented cascade
procedure consisting of formation of a cyclobutene moiety,
subsequent radical addition, and ring expansion without a metal
catalyst. Second, it gives a synthetically and biologically valuable
benzoindole-1-oxide derivative through a straightforward path-
way using TBN as an environmentally friendly and cheap NO
source.9
Encouraged by the above result, a systematic study on this
reaction with the aim to develop it into a general method for the
preparation of indole-1-oxide derivatives was conducted. First,
the loading of EtOH was reduced from 2 to 0.6 mL (10 mmol,
20 equiv) or 0.3 mL (5 mmol, 10 equiv) (Table 1, entries 2 and
3). It turned out that using 0.6 mL (20 equiv) of EtOH as both
substrate and solvent could guarantee an effective trans-
formation, giving 4a in a yield of 80%. Second, increasing or
reducing the loading of TBN did not benefit this reaction
(entries 4 and 5 vs 2). Third, different acids, such as HOAc,
TFA, and TfOH, were tried as possible catalysts. However, no
better result was obtained (entries 6−8). Fourth, when the
reaction temperature was increased from rt to 50 °C, a slight
decrease in the yield of 4a was observed (entry 9). Further study
showed that prolonging the reaction time could not improve the
yield of 4a obviously (entry 10). Finally, we tried to use the less
expensive and more sustainable 95% EtOH to replace EtOH as
substrate and reaction medium. Under this circumstance, 4a
precipitated upon cooling the resulting reaction mixture to 0 °C
and was collected through simple filtration in 82% yield (entry
11).
a
Reaction conditions: 1 (0.5 mmol), EtOH (10 mmol, 95%), TBN (1
b
mmol), rt, air, 3 h. Isolated yield via precipitation and filtration.
c
Isolated yield via column chromatography.
than those with EWGs (4d and 4g vs 4b, 4c, and 4e). In
addition, naphthalene-linked allene-yne could also lead to target
product 4h in 45% yield. Then, to test some more challenging
functional groups, we have been trying hard to synthesize
substrates with an amine, hydroxyl, or nitro group. However, our
efforts in this regard failed. Further study showed that 1 bearing
a methyl, ethyl, or amyl group at the internal or terminal position
of the allenic unit was suitable to give 4i−4p in 50−76% yields.
In addition, substrates with either EDGs or EWGs on the
arylalkynyl moiety worked well and delivered products 4q−4x in
42−76% yields. When the R2 unit was a 2-thienyl or 3-thienyl
group, products 4y and 4z were obtained in 60 and 71% yields,
respectively. Then, we found that thiophene-tethered allene-yne
could also react with EtOH and TBN to afford 4aa in 59% yield.
Nevertheless, a substrate with a cyclopropyl group on the alkynyl
moiety failed to give the target product 4bb.
Next, the suitability of different alcohol substrates (2) was
investigated by using 1a as the model substrate. It was first found
that alcohols with either a shorter or longer alkyl chain
compared with ethanol were compatible to afford 4cc and 4dd
(Scheme 3). Branched chain alcohol accessed the corresponding
product 4ee in moderate yield. Interestingly, both allyl and
propargyl alcohol were compatible with the applied radical
With the optimized conditions in hand, the reaction scope was
subsequently explored by varying the substituents attached on
the linking benzene ring of allene-ynes 1. It was found that
whether allene-ynes with electron-withdrawing groups (EWGs),
such as fluoro and chloro, or those with electron-donating group
(EDG) methoxy were compatible with this reaction and
afforded products 4a−4g in 64−85% yields (Scheme 2).
Overall, substrates bearing EDGs showed better efficiency
B
DOI: 10.1021/acs.orglett.9b00968
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
a b
,
improve the formation of 6a. As a result, when 1a was treated
with TBN (3, 2equiv) and 5a (1equiv) in DCE at 50 °C for 3 h,
6a was obtained in a maximum yield of 76% (Scheme 4, (3)).
Prompted by the above results, we also used some other
allene-ynes to explore the generality of this transformation for
the formation of naphthalene-1,2-diones. It showed that all of
them were suitable substrates to give 6b−6e in 60−82% yields
(Scheme 5).
Scheme 3. Scope of Substrates for the Formation of 4 (2)
a b
,
Scheme 5. Scope of Substrates for the Formation of 6
a
Reaction conditions: 1a (0.5 mmol), alcohol (10 mmol), TBN (1
a
b
Reaction conditions: 1a (0.5 mmol), 5 (0.5 mmol), TBN (1 mmol),
mmol), rt, air, 3 h. Isolated yield via precipitation and filtration.
b
c
d
DCE (2 mL), 50 °C, air, 3 h. Isolated yield via column
chromatography.
Isolated yield via chromatography. Thiol (2.5 mmol), DCE (2 mL),
isolated yield via column chromatography.
Based on the experimental results and previous reports,6,11
putative pathway leading to the formation of 4a was proposed in
Scheme 6. Initially, intramolecular [2 + 2] cycloaddition of 1a
a
reaction conditions, thus allowing for possible subsequent
structural elaboration of the products (4ff, 4gg). In addition to
primary alcohols, secondary alcohol could also take part in this
reaction efficiently to give 4hh. On the other hand, tert-butyl
alcohol and phenol were unable to convert into the according
products (4ii, 4jj), most likely owing to their steric hindrance
and/or weak nucleophilic ability. Promisingly, thiols were also
suitable for this cascade reaction and produced 4kk−4nn in 40−
66% yields.
Scheme 6. Plausible Pathway Accounting for 4a
Thus far, we have established an efficient synthesis of indole-
1-oxides from the reactions of allene-ynes with alcohols/thiols
and TBN. To further explore the scope of this transformation,
propylamine (5a) instead of alcohol was subjected to the
standard conditions, as shown in Scheme 4, (1). However, the
Scheme 4. Formation of 6a
occurs to afford intermediate A.6 Subsequent 1,6-addition of
ethanol to A gives intermediate B, which then undergoes a
tautomerization to form B′.6c Next, the NO radical (•NO),
generated from the decomposition of TBN, extracts a hydrogen
from B′ to deliver a radical intermediate C. Subsequently, C
couples with •NO to give intermediate D. Then, E was formed
via a ring expansion of D.11d Finally, tautomerization of E yields
the final product 4a.
To confirm the proposed pathway, some control experiments
were conducted. First, (2,2,6,6-tetramethylpiperidin-1-yl)oxyl
(TEMPO) as a radical inhibitor was added to the reaction, and
no product was formed, indicating the reaction might involve a
radical process (Scheme 7, (1)). Second, treating 1a with 95%
EtOH in the absence of TBN affords the proposed intermediate
B in 95% yield (Scheme 7, (2)). Next, B was subjected to the
standard conditions to afford 4a in 82% yield (Scheme 7, (3)).
The above results suggested that B might be the key
intermediate for the construction of 4a from 1a. Third,
reaction system was messy. Then, the loading of 5a was
decreased to 1 equiv, and DCE was used as the reaction medium
to improve the efficiency of this transformation. Surprisingly, an
iminated (Z)-naphthalene-1,2-dione (6a, 25%) was composed
without the formation of indole-1-oxide (Scheme 4, (2)). The
Z-selectivity of 6a was confirmed by X-ray diffraction analysis. It
is known that the naphthalene-1,2-dione scaffold constitutes the
core of numerous natural and pharmaceutical compounds.10
Therefore, the efficient and facile formation of 6a is synthetically
promising. Thus, extensive parameters were screened to
t
combination of BuOOtBu (TBP) and Bu3SnD was used to
capture the radical intermediate C, from which [D1]-B′/[D1]-B
was not obtained (Scheme 7, (4)). It indicated that the
hydrogen of intermediate B′ might be extracted by the in situ
C
DOI: 10.1021/acs.orglett.9b00968
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
construction of 6a should undergo a radical pathway. Next, 1a
was treated with 5a in the absence of TBN and afforded iminated
(Z)-1-naphthol (G′) in 95% yield (Scheme 9, (2)). Second, in
the absence of 5a, G′ was subjected to the standard reaction
conditions and delivered 6a in 85% yield (Scheme 9, (3)),
indicating that G′ may be the intermediate for the formation of
6a. Subsequently, when the reaction for the transformation of G′
was carried out under nitrogen instead of air, 6a was still
obtained in 82% yield (Scheme 9, (4)), suggesting that the effect
of molecular oxygen might be excluded. Third, treating G′ with
TBP instead of TBN could not deliver the product 6a (Scheme
9, (5)), excluding the effect of radical tBuO•. H218O (5 equiv)
was then added in the reaction for the preparation of 6a from G′
(Scheme 9, (6)), from which [18O1]-6a and [16O]-6a were
obtained in a ratio of 1:1.7 (see Supporting Information,
determined by HRMS analysis). It hints that H2O should be a
source of the oxygen atom of the newly formed carbonyl group
embedded in 6a.
Scheme 7. Control Experiments (I)
t
generated radical NO rather than radical BuO with possible
steric hindrance.
For the construction of 6a, the initial generation of
intermediate A should be involved. Subsequent 1,6-addition of
amine (5a) to A delivers intermediate F. Then, tautomerization
of F occurs to afford F′, which tends to undergo a ring-opening
process and intramolecular hydrogen transfer to form
intermediate G with unstable exocyclic double bonds. Then,
G isomerizes into more stable intermediate G′.6d Next, addition
of the in situ generated NO radical9d to intermediate G′ and
subsequent hydrogen migration generate oxime intermediate
I,12a which was further hydrolyzed to give the final product 6a
(Scheme 8).12b
To demonstrate the scalability of the synthetic method
developed in this paper, the preparations of 4a and 6a were
performed at a 5 mmol scale. As a result, 4a and 6a were
efficiently obtained in 79 and 71% yields, respectively (Scheme
10).
Scheme 10. Gram-Scale Synthesis of 4a and 6a
Scheme 8. Plausible Pathway Accounting for 6a
Having established a convenient and efficient synthesis of
benzoindole-1-oxide derivatives (4), the synthetic applications
of 4 were subsequently studied (Scheme 11). Thus, 4a was
Scheme 11. Synthesis of 1H-Benzo[g]indol-5-ols (7)
More control experiments were performed to confirm the
mechanism. First, BHT (butylated hydroxytoluene, 2 equiv) was
used as a radical inhibitor in this reaction. As a result, the yield of
6a was decreased to 16% (Scheme 9, (1)). It showed that the
treated with zinc powder in acetic acid at rt for 4 h. From this
reaction, 2-phenyl-1H-benzo[g]indol-5-ol (7a) was obtained in
90% yield. This unprecedented transformation is attractive as
benzo[g]indol-5-ol is a key building block of many compounds
displaying significant medicinal activities.13 To explore its
generality, the suitability of other benzoindole-1-oxides was
studied. It was found that all of them could be smoothly
transformed into products 7b−7d in high yields, thus providing
a highly convenient and efficient pathway toward 1H-benzo-
[g]indol-5-ol derivatives.
Scheme 9. Control Experiments (II)
In summary, an efficient and novel methodology for the
synthesis of 5-oxo-2H-benzo[g]indole-1-oxides/functionalized
naphthalene-1,2-diones via the cascade reaction of allenynes
with alcohols/amines and TBN without using any catalyst has
been successfully developed in this paper. Notably, most of the
reactions used aqueous alcohol as the substrate and involved a
D
DOI: 10.1021/acs.orglett.9b00968
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
́
Tripathi, A.; Parra, L. L. L.; Williams, R. M.; Berlinck, R. G. S.; Joullie,
M. M.; Sherman, D. H. J. Am. Chem. Soc. 2016, 138, 11176.
(5) (a) Ma, S. Chem. Rev. 2005, 105, 2829. (b) Aubert, C.;
Fensterbank, L.; Garcia, P.; Malacria, M.; Simonneau, A. Chem. Rev.
2011, 111, 1954. (c) Shen, Q.; Hammond, G. B. J. Am. Chem. Soc. 2002,
124, 6534. (d) Brummond, K. M.; Chen, D. Org. Lett. 2005, 7, 3473.
(e) Saito, N.; Tanaka, Y.; Sato, Y. Org. Lett. 2009, 11, 4124. (f) Siebert,
M. R.; Osbourn, J. M.; Brummond, K. M.; Tantillo, D. J. J. Am. Chem.
Soc. 2010, 132, 11952. (g) Lu, B.-L.; Shi, M. Angew. Chem., Int. Ed.
2011, 50, 12027. (h) He, Y.; Zhang, X.; Cui, L.; Wang, J.; Fan, X. Green
Chem. 2012, 14, 3429. (i) Feng, T.; Tian, M.; Zhang, X.; Fan, X. J. Org.
Chem. 2018, 83, 5313.
convenient purification process of simple precipitation and
filtration. With advantages such as mild reaction conditions, a
wide range of substrates, a simple operational process, and large-
scale preparation, this facile method is expected to find more
applications in expanding the scaffold space of N-oxide and
naphthalene-1,2-dione derivatives as valuable candidates and
versatile intermediates in medicinal chemistry.
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.orglett.9b00968.
(6) (a) Wang, J.-Y.; Zhou, P.; Li, G.; Hao, W.-J.; Tu, S.-J.; Jiang, B. Org.
Lett. 2017, 19, 6682. (b) Liu, F.; Wang, J.-Y.; Zhou, P.; Li, G.; Hao, W.-
J.; Tu, S.-J.; Jiang, B. Angew. Chem., Int. Ed. 2017, 56, 15570. (c) Zhou,
P.; Wang, J.-Y.; Zhang, T.-S.; Li, G.; Hao, W.-J.; Tu, S.-J.; Jiang, B. Chem.
Commun. 2018, 54, 164. (d) Sha, H.-K.; Liu, F.; Lu, J.; Liu, Z.-Q.; Hao,
W.-J.; Tang, J.-L.; Tu, S.-J.; Jiang, B. Green Chem. 2018, 20, 3476. (e) Li,
H.; Hao, W.-J.; Wang, M.; Qin, X.; Tu, S.-J.; Zhou, P.; Li, G.; Wang, J.;
Jiang, B. Org. Lett. 2018, 20, 4362. (f) Sha, H.-K.; Xu, T.; Liu, F.; Tang,
B.-Z.; Hao, W.-J.; Tu, S.-J.; Jiang, B. Chem. Commun. 2018, 54, 10415.
(g) Li, H.; Zhou, P.; Xie, F.; Hu, J.-Q.; Yang, S.-Z.; Wang, Y.-J.; Hao, W.-
J.; Tu, S.-J.; Jiang, B. J. Org. Chem. 2018, 83, 13335.
(7) Wei, H.; Zhai, H.; Xu, P.-F. J. Org. Chem. 2009, 74, 2224.
(8) Feng, T.; He, Y.; Zhang, X.; Fan, X. Adv. Synth. Catal. 2019, 361,
1271.
(9) (a) Yang, X.-H.; Song, R.-J.; Li, J.-H. Adv. Synth. Catal. 2015, 357,
3849. (b) Chaudhary, P.; Gupta, S.; Muniyappan, N.; Sabiah, S.;
Kandasamy, J. Green Chem. 2016, 18, 2323. (c) He, K.; Li, P.; Zhang, S.;
Chen, Q.; Ji, H.; Yuan, Y.; Jia, X. Chem. Commun. 2018, 54, 13232.
(d) He, Y.; Zheng, Z.; Liu, Y.; Qiao, J.; Zhang, X.; Fan, X. Org. Lett.
2019, 21, 1676.
Experimental procedure, characterization data, and NMR
spectra of all products (PDF)
Accession Codes
CCDC 1878661 and 1882514 contain 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
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Authors
■
*E-mail: heyan@htu.cn
*E-mail: xuesen.fan@htu.cn
ORCID
(10) (a) Hatfield, M. J.; Chen, J.; Fratt, E. M.; Chi, L.; Bollinger, J. C.;
Binder, R. J.; Bowling, J.; Hyatt, J. L.; Scarborough, J.; Jeffries, C.;
Potter, P. M. J. Med. Chem. 2017, 60, 1568. (b) Ding, C.; Tian, Q.; Li, J.;
Jiao, M.; Song, S.; Wang, Y.; Miao, Z.; Zhang, A. J. Med. Chem. 2018, 61,
760.
(11) (a) Kobayashi, Y.; Kuroda, M.; Toba, N.; Okada, M.; Tanaka, R.;
Kimachi, T. Org. Lett. 2011, 13, 6280. (b) Chen, F.; Huang, X.; Li, X.;
Shen, T.; Zou, M.; Jiao, N. Angew. Chem., Int. Ed. 2014, 53, 10495.
(c) Yuan, B.; Zhang, F.; Li, Z.; Yang, S.; Yan, R. Org. Lett. 2016, 18,
5928. (d) Senadi, G. C.; Wang, J.-Q.; Gore, B. S.; Wang, J.-J. Adv. Synth.
Catal. 2017, 359, 2747. (e) Marien, N.; Reddy, B. N.; De Vleeschouwer,
F.; Goderis, S.; Van Hecke, K.; Verniest, G. Angew. Chem., Int. Ed. 2018,
57, 5660.
Yan He: 0000-0003-2679-2547
Xuesen Fan: 0000-0002-2040-6919
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We greatly appreciate the National Natural Science Foundation
of China (21572047, 21702050), Plan for Scientific Innovation
Talents of Henan Province (184200510012), and 111 Project
(D17007) for financial support.
(12) (a) Gao, X.; Zhang, F.; Deng, G.; Yang, L. Org. Lett. 2014, 16,
3664. (b) Barton, D. H. R.; Finet, J.-P.; Thomas, M. Tetrahedron 1988,
44, 6397.
(13) (a) Koeberle, A.; Haberl, E.-M.; Rossi, A.; Pergola, C.; Dehm, F.;
Northoff, H.; Troschuetz, R.; Sautebin, L.; Werz, O. Bioorg. Med. Chem.
REFERENCES
■
(1) (a) Miller, K. A.; Williams, R. M. Chem. Soc. Rev. 2009, 38, 3160.
(b) Kochanowska-Karamyan, A. J.; Hamann, M. T. Chem. Rev. 2010,
110, 4489. (c) Shiri, M. Chem. Rev. 2012, 112, 3508. (d) Platon, M.;
Amardeil, R.; Djakovitch, L.; Hierso, J.-C. Chem. Soc. Rev. 2012, 41,
3929. (e) Bartoli, G.; Dalpozzo, R.; Nardi, M. Chem. Soc. Rev. 2014, 43,
4728. (f) Lancianesi, S.; Palmieri, A.; Petrini, M. Chem. Rev. 2014, 114,
7108. (g) Bariwal, J.; Voskressensky, L. G.; Van der Eycken, E. V. Chem.
Soc. Rev. 2018, 47, 3831.
(2) (a) Nising, C. F. Chem. Soc. Rev. 2010, 39, 591. (b) Qian-Cutrone,
J.; Huang, S.; Shu, Y.-Z.; Vyas, D.; Fairchild, C.; Menendez, A.;
Krampitz, K.; Dalterio, R.; Klohr, S. E.; Gao, Q. J. Am. Chem. Soc. 2002,
124, 14556. (c) Myers, A. G.; Herzon, S. B. J. Am. Chem. Soc. 2003, 125,
12080. (d) Herzon, S. B.; Myers, A. G. J. Am. Chem. Soc. 2005, 127,
5342. (e) Wulff, J. E.; Herzon, S. B.; Siegrist, R.; Myers, A. G. J. Am.
Chem. Soc. 2007, 129, 4898.
2009, 17, 7924. (b) Karg, E.-M.; Luderer, S.; Pergola, C.; Bu
Rossi, A.; Northoff, H.; Sautebin, L.; Troschutz, R.; Werz, O. J. Med.
̈
hring, U.;
̈
Chem. 2009, 52, 3474. (c) Nie, G.; Wang, L.; Liu, C. J. Mater. Chem. C
2015, 3, 11318. (d) Bruno, F.; Errico, S.; Pace, S.; Nawrozkij, M. B.;
Mkrtchyan, A. S.; Guida, F.; Maisto, R.; Olgac,̧ A.; D’Amico, M.;
Maione, S.; De Rosa, M.; Banoglu, E.; Werz, O.; Fiorentino, A.; Filosa,
R. Eur. J. Med. Chem. 2018, 155, 946.
(3) (a) Wang, X.; You, J.; King, J. B.; Powell, D. R.; Cichewicz, R. H. J.
Nat. Prod. 2012, 75, 707. (b) Mukai, K.; de Sant’Ana, D. P.; Hirooka, Y.;
Mercado-Marin, E. V.; Stephens, D. E.; Kou, K. G. M.; Richter, S. C.;
Kelley, N.; Sarpong, R. Nat. Chem. 2018, 10, 38.
(4) (a) Baran, P. S.; Hafensteiner, B. D.; Ambhaikar, N. B.; Guerrero,
C. A.; Gallagher, J. D. J. Am. Chem. Soc. 2006, 128, 8678. (b) Artman, G.
D., III; Grubbs, A. W.; Williams, R. M. J. Am. Chem. Soc. 2007, 129,
6336. (c) Newmister, S. A.; Gober, C. M.; Romminger, S.; Yu, F.;
E
DOI: 10.1021/acs.orglett.9b00968
Org. Lett. XXXX, XXX, XXX−XXX