Tuneable access to indole, indolone, and cinnoline derivatives from a common 1,4-diketone Michael acceptor

Article abstract of DOI:10.3762/BJOC.16.144

A convergent strategy is reported for the construction of nitrogen-containing heterocycles from common substrates: 1,4-diketones and primary amines. Indeed, by just varying the substrates, the substituents, or the heating mode, it is possible to selectively synthesize indole, indolone (1,5,6,7-tetrahydroindol-4-one), or cinnoline (5,6,7,8-tetrahydrocinnoline) derivatives in moderate to excellent yields.

Full text of DOI:10.3762/BJOC.16.144

Tuneable access to indole, indolone, and cinnoline
derivatives from a common 1,4-diketone Michael acceptor
Dalel El-Marrouki1,2, Sabrina Touchet*1, Abderrahmen Abdelli2, Hédi M’Rabet2,
Mohamed Lotfi Efrit2 and Philippe C. Gros*1
Full Research Paper
Open Access
Address:
Beilstein J. Org. Chem. 2020, 16, 1722–1731.
1Université de Lorraine, CNRS, L2CM, F-5400 Nancy, France and
2Université de Tunis El Manar, SOHES-LR17ES01, Tunis, Tunisia
doi:10.3762/bjoc.16.144
Received: 24 April 2020
Accepted: 06 July 2020
Published: 17 July 2020
Email:
Sabrina Touchet* - sabrina.touchet@univ-lorraine.fr;
Philippe C. Gros* - philippe.gros@univ-lorraine.fr
Associate Editor: J. A. Murphy
* Corresponding author
© 2020 El-Marrouki et al.; licensee Beilstein-Institut.
License and terms: see end of document.
Keywords:
cinnoline; 1,4-diketone; indole; indolone; N-heterocycle
Abstract
A convergent strategy is reported for the construction of nitrogen-containing heterocycles from common substrates: 1,4-diketones
and primary amines. Indeed, by just varying the substrates, the substituents, or the heating mode, it is possible to selectively synthe-
size indole, indolone (1,5,6,7-tetrahydroindol-4-one), or cinnoline (5,6,7,8-tetrahydrocinnoline) derivatives in moderate to excel-
lent yields.
Introduction
Nitrogen-containing heterocycles are widespread in plenty of marketed drugs used as anticancer, antiemetic, antihypertensive,
molecules of interest, either in materials science, optics, elec- antidepressant, anti-inflammatory, or anti-HIV agents, among
tronics, or biology [1-4]. They are also very useful building others [9]. In contrast, concerning indolone and cinnoline deriv-
blocks to create more sophisticated organic molecules. There- atives, there are very few marketed drugs, but many molecules
fore, the search for efficient methods for the synthesis of are under investigations for their activities as antibacterial, anti-
nitrogen-containing heterocycles is crucial to both organic and fungal, anticancer, or anti-inflammatory agents or even on the
medicinal chemists. Among these, indole, indolone (1,5,6,7- central nervous system [7,12,13].
tetrahydroindol-4-one), and cinnoline (5,6,7,8-tetrahydrocinno-
line) derivatives are important classes of functionalized com- Several routes have been reported to access these key com-
pounds, having biological and medicinal activities of interest pounds, the most developed being for the indole [14] deriva-
(Figure 1) [5-8].
tives using the Fischer indole synthesis involving sigmatropic
rearrangements [15-18], nucleophilic and electrophilic cycliza-
Indeed, indole ring-containing compounds have various biologi- tions [19-25], reductive and oxidative cyclizations [26,27], and
cal and pharmacological activities and are part of many transition-metal catalysis [28-37]. There are fewer ways to
1722

Beilstein J. Org. Chem. 2020, 16, 1722–1731.
Figure 1: Examples of bioactive nitrogen-containing heterocycles (indole [9], indolone [10], and cinnoline [11] derivatives).
access indolone derivatives, mainly based on the use of di- have shown that it can be selectively directed towards the syn-
[12,38,39] or triketones [10,13] and enaminones [40-43] as thesis of indole, indolone, or cinnoline derivatives by just
starting materials. For the synthesis of cinnoline derivatives, changing the substrates, substituents, or heating mode
aryldiazenes and aryltriazenes are substrates of choice for tran- (Scheme 1).
sition-metal-catalyzed (Rh, Pd, Cu) cross-coupling reactions,
followed by intramolecular cyclizations [44-47]. Moreover, Results and Discussion
arylhydrazones and arylhydrazines/hydrazines can be used as The synthesis of the target compounds required the prior prepa-
well, respectively, as partners in [4 + 2] cyclization reactions ration of a panel of variously substituted 1,4-diketones 5. The
[48-51] or by reacting mostly with carbonyl derivatives [52-55]. 1,4-diketones 5 have been prepared either by a Nef reaction
[56] from the corresponding nitroenone 3 or a Wittig reaction
From the state-of-the-art, a strategy that promotes the synthesis [57] from 1,2-cyclohexanedione and the corresponding ylide 4
of indole, indolone, or cinnoline derivatives from the same (Scheme 2).
starting material is not yet available. To reach this goal, the
Michael reaction between 1,4-diketones and primary amines The nitrenones 3a–d were obtained in three steps from
seems particularly attractive because of its straightforward and the appropriate commercially available cyclohexenones
metal-free properties, and because they can be performed under (Scheme 2). First, a Baylis–Hillman reaction between cyclo-
air. Herein, we report our investigations on this reaction, and we hexanone and formaldehyde led to the formation of the corre-
Scheme 1: General strategy to access indole, indolone, and cinnoline derivatives from 1,4-diketones.
1723

Beilstein J. Org. Chem. 2020, 16, 1722–1731.
Scheme 2: Synthesis of the 1,4-diketones 5a–k via the Nef reaction or the Wittig reaction. i) HCHO (aq), DMAP, THF, rt, 24 h; ii) Ac2O, Et3N, DMAP,
0 °C, then 2 h, rt; iii) R1–CH2–NO2, Et3N, EtOH, reflux, 24 h; iv) EtONa, EtOH, rt, 3 h, then H2SO4, −50 °C, 1 h; v) toluene or DCM, reflux, 48 h, then
rt, 2 d. aVia the Nef reaction. bVia the Wittig reaction.
sponding Baylis–Hillman alcohols 1a/b in good yield [58], fol- Wittig reaction [57], offering a much more straightforward and
lowed by a DMAP-catalyzed acetylation of these alcohols, efficient route to a panel of new diketones, 5e–k, from 1,2-
which gave the corresponding acetates 2a–d [59]. The cyclohexanedione and the corresponding Wittig ylides 4a–g
nitrenones 3a–d were finally obtained in an acceptable yield by (readily accessible from the corresponding halogenated deriva-
reacting the acetate derivatives with the appropriate nitro- tives, Scheme 2). Indeed, the Wittig reaction leads exclusively
alkanes [60]. The next step was the transformation of the nitro to the isomerized products 5.
group of 3a–d via the Nef reaction, using sodium ethoxide in
ethanol, followed by the hydrolysis with concentrated sulfuric With the 1,4-diketones 5 in hand, we first investigated the syn-
acid at a low temperature [56], leading to the corresponding thesis of indole and indolone derivatives. The reaction mecha-
new γ-diketones 5a–d in 61–87% yield (Scheme 2).
nism shown in Scheme 3 involves the formation of an imine
upon the reaction of the primary amine with the most reactive
Despite the efficiency of the Nef reaction, the diversity at the R1 carbonyl moiety (nonconjugated and exocyclic carbonyl func-
position via this synthetic route remains limited in terms of tion). Then, depending on the reaction conditions, the imine can
chemical diversity as it depends on the availability of the corre- react following a 1,2- or 1,4-addition process, leading respec-
sponding nitro derivative. It was thus decided to move on to the tively to an indole 6 (after dehydration and aromatization) or an
1724

Beilstein J. Org. Chem. 2020, 16, 1722–1731.
Scheme 3: Mechanism of the formation of indole and indolone derivatives.
indolone 7. The reaction was first investigated by mixing the di- 6b:7b ratio obtained in Table 1, entry 5. While in aprotic sol-
ketone 5b as the Michael acceptor and benzylamine under vents, other than toluene (Table 1, entries 7 and 8), the reaction
various conditions (Table 1).
produced complex mixtures of degradation products, and using
alcohols had a notable impact on the reaction contents. Indeed,
We first investigated the reactivity in the presence of a set of going from ethanol to propanol, and thus increasing the
catalysts with different acidities (Table 1, entries 1–5). Among refluxing temperature, led to the indolone 7b as the main prod-
them, only acetic acid afforded reaction products, while the uct, with the best yield being obtained in butanol (43%, Table 1,
others only produced complex mixtures of degradation prod- entry 11), however, with the formation of 6b occurring only in
ucts. Under the conditions of entry 5, the indole 6b was isolat- 10% yield. Switching to microwave irradiation formed exclu-
ed in 47%, and the indolone 7b was also formed concomitantly sively 7b in 60% yield after 3 h (Table 1, entry 13). Note, that
in 10% yield. The experiments in Table 1, entries 6–11 were to check the effect of a shorter reaction time on the reaction
next performed with the aim to favor the 1,4-addition process, outcome, we reduced the time to 3 h also under the classical
and thus to form the indolone 7b. Removing the acid catalyst refluxing conditions from Table 1, entry 11 and obtained a
from the reaction mixture (Table 1, entry 6) did not affect the partial conversion of the starting diketone 5b. Despite the side
Table 1: Effects of solvent and heating mode on the 6b:7b ratio.
entrya
catalyst
solvent
t (h)
6b (%)b
7b (%)b
6b:7b
1
TfOH (3%)
toluene
toluene
toluene
toluene
toluene
toluene
CH2Cl2
THF
16 h
16 h
16 h
16 h
16 h
16 h
16 h
16 h
16 h
16 h
16 h
16 h
MWI 3 h
–
–
–
2
AgOTf (3%)
–
–
–
3
TFA (3%)
–
–
–
4
pTsOH (3%)
–
–
–
5
AcOH (3%)
47
33
–
10
8
83:17
80:20
–
6
–
–
–
–
–
–
–
–
7
–
8
–
–
–
9
ethanol
propanol
butanol
pentanol
butanol
13
6
16
31
43
28
60
45:55
16:84
19:81
20:80
0:100
10
11
12
13c
10
7
–
aReaction conditions: 5b (0.54 mmol), primary amine (0.81 mmol), 4 mL solvent, and catalyst (0.02 mmol) unless otherwise specified (in column 2,
the catalyst percentage corresponds to 0.02 mmol). bIsolated yield. c13 mL of butanol, MWI 100 °C.
1725

Beilstein J. Org. Chem. 2020, 16, 1722–1731.
formation of the indolone 7b in Table 1, entry 5, these condi- We then succeeded in directing the reaction exclusively towards
tions were applied to several amines, producing the correspond- indole formation by reacting the diketone with appropriate sub-
ing substituted indoles 6a and 6c–f in 41–54% yield strates, combining a primary amine with a tertiary amine or a
(Scheme 4). The yield of the indolones 7a and 7c–f was found pyridine separated by several spacer arms (Scheme 6).
almost constant (10–14%) with all amines involved. It is worthy
of note that the two compounds were easily separated using Under these conditions, the functional indoles 6h–l were ob-
usual chromatographic techniques.
tained exclusively in 45–55% yield. We assume that the tertiary
amine would interact with the protonated intermediate, and thus
The reaction was also applied to a diamine (Scheme 5). When promoting the 1,2-addition (Scheme 6). However, for the pyri-
1,3-diaminopropane was used, the bisindole 6g was isolated in dine substituent (compounds 6k and 6l), another intermediate
46% yield. Interestingly, the mixed indolone/indole compound may be involved as the shape of this diamine does not allow
9 was also obtained as a side product. However, no traces of the enough flexibility to achieve the conformation of the proposed
bisindolone derivative were detected.
intermediate.
Scheme 4: Synthesis of the indoles 6a–f and the corresponding side product indolones 7a–f.
1726

Beilstein J. Org. Chem. 2020, 16, 1722–1731.
Scheme 5: Reaction of 5b with a diamine.
Scheme 6: Synthesis of the indoles 6h–l.
We next examined the preparation of a set of indolones under not from a degradation of the indolone 7b. For this purpose, the
the microwave conditions determined in Table 1, entry 13. indolone 7b was refluxed overnight with acetic acid in toluene,
These conditions were applied to several amines, producing ex- under these conditions producing mainly the indole (Table 1,
clusively the corresponding substituted indolones 7d and 7g–k entry 5). The indolone 7b was found unchanged, with no trace
in 48–56% yield (Scheme 7).
of the indole 6b being detected (see Supporting Information
File 1, chapter I), indicating that the indole was formed intramo-
Here again, the amount of indolone was found to be almost con- lecularly by a 1,2-addition of the intermediately formed imine
stant, whatever the amine involved was, suggesting that the to the Michael acceptor (Scheme 3).
reaction is not dependent on the nature of the amine. It is worth
to notice that, for a substrate combining a primary amine with a We then investigated the synthesis of cinnoline derivatives by
pyridine separated by a spacer arm, only the indolone deriva- mixing the diketone 5a and hydrazine monohydrate under
tive is obtained in those conditions as well (compound 7i, various conditions (Table 2). We first investigated the reactivi-
Scheme 7). Based on these results, we found it important to ty in ethanol, as a protic solvent, at room temperature (Table 2,
check whether the indole 6b resulted from a 1,2-addition and entry 1). Under these conditions, the expected cinnoline 8a
1727

Beilstein J. Org. Chem. 2020, 16, 1722–1731.
Scheme 7: Synthesis of the indolone derivatives 7b, 7d, and 7g–k.
Table 2: Optimization of the reaction conditions for the synthesis of the cinnolines 8.
entrya
catalyst
solvent
T (°C)
t (h)
8a (%)b
1
2
3
4
–
EtOH
EtOH
toluene
EtOH
rt
48
48
48
16
20
40
35
82
–
reflux
reflux
reflux
–
AcOH (3 mol %)
aReaction conditions: 5a (1 mmol), hydrazine monohydrate (1.5 mmol), solvent (6 mL), catalyst (0.03 mmol), unless otherwise specified. The re-
ported catalyst percentage exactly corresponds to 0.03 mmol. bIsolated yield.
was obtained in a low yield of 20% that could be increased up vation, the reaction was found to be efficient for producing the
to 40% upon refluxing the mixture (Table 2, entry 2). Switching expected cinnoline derivatives 8a–k in good to excellent yield
to toluene (Table 2, entry 3) did not improve the reaction (77–94%) and tolerated alkyl, aromatic, and heteroaromatic
outcome. However, the addition of a catalytic amount of acetic groups as R1.
acid in refluxing ethanol while shortening the reaction time
dramatically increased the yield of 8a up to 82% (Table 2, entry The success of our convergent strategy here can be explained
4).
through the mechanism suggested in Scheme 9. The synthetic
pathway leading to the formation of the indolone 7 starts with
These optimized conditions were then applied to the previously an imine formation between the secondary amine and the
synthesized 1,4-diketones 5a–k (Scheme 8). As a general obser- nonconjugated carbonyl from the 1,4-diketone. After an
1728

Beilstein J. Org. Chem. 2020, 16, 1722–1731.
Scheme 8: Synthesis of the cinnoline derivatives 8a–k.
Scheme 9: Proposed mechanism for the preparation of the compounds 6, 7, and 8.
1729

Beilstein J. Org. Chem. 2020, 16, 1722–1731.
imine–enamine equilibrium, an intramolecular 1,4-addition to
the Michael acceptor part of the molecule occurs, followed by a
prototropy, leading to an intermediate enol that, after a
keto–enol equilibrium and aromatization, gives the indolone 7.
For the indole 6 and the cinnoline 8, the synthesis starts with the
protonation of the oxygen atom of the conjugated carbonyl
group of the 1,4-diketone, followed by an imine formation be-
tween the secondary amine and the nonconjugated carbonyl
unit. Next, an intramolecular 1,2-addition to the Michael
acceptor part of the molecule, previously activated by acid ca-
talysis, takes place (after an imine–enamine equilibrium for the
indole pathway), followed by a prototropy, the release of a
water molecule, the recovery of the proton catalyst, and atmos-
pheric oxygen aromatization, leading to the indole 6 or the
cinnoline 8.
ORCID® iDs
Sabrina Touchet - https://orcid.org/0000-0002-4550-6756
Hédi M’Rabet - https://orcid.org/0000-0002-3301-2900
Mohamed Lotfi Efrit - https://orcid.org/0000-0002-6950-0519
Philippe C. Gros - https://orcid.org/0000-0003-4905-1581
Preprint
A non-peer-reviewed version of this article has been previously published
as a preprint doi:10.3762/bxiv.2020.56.v1
References
1. Kumar, D.; Kumar Jain, S. Curr. Med. Chem. 2016, 23, 4338–4394.
doi:10.2174/0929867323666160809093930
2. Liu, J.-C.; Narva, S.; Zhou, K.; Zhang, W. Mini-Rev. Med. Chem. 2019,
19, 1517–1530. doi:10.2174/1389557519666190312152358
3. Wang, S.-Y.; Shi, X.-C.; Laborda, P. Eur. J. Med. Chem. 2020, 185,
111847. doi:10.1016/j.ejmech.2019.111847
Conclusion
4. Rubina, B.; Dharam P, P.; Garima, K.; Ravi, K.; Manni, D.
Indian J. Pharm. Educ. Res. 2019, 53, s1–s16.
In summary, we have successfully developed a straightforward
and metal-free strategy for the synthesis of nitrogen-containing
heterocyclic moieties of biological interest; indoles 6, indolones
7, and cinnolines 8, starting from common substrates
1,4-diketones 5 and primary amines. The protocols developed
here used mild conditions, were functional-group tolerant,
transition-metal-free, proceeded in moderate to good yield,
and could therefore easily be used in medicinal chemistry
projects for the rapid access to a wide range of variously
substituted compounds for structure–activity relationship
studies. The biological activity of the molecules is currently
being studied.
doi:10.5530/ijper.53.2s.44
5. Singh, T. P.; Singh, O. M. Mini-Rev. Med. Chem. 2018, 18, 9–25.
doi:10.2174/1389557517666170807123201
6. Thanikachalam, P. V.; Maurya, R. K.; Garg, V.; Monga, V.
Eur. J. Med. Chem. 2019, 180, 562–612.
doi:10.1016/j.ejmech.2019.07.019
7. Lewgowd, W.; Stanczak, A. Arch. Pharm. (Weinheim, Ger.) 2007, 340,
65–80. doi:10.1002/ardp.200500194
8. Awad, E. D.; El-Abadelah, M. M.; Matar, S.; Zihlif, M. A.; Naffa, R. G.;
Al-Momani, E. Q.; Mubarak, M. S. Molecules 2012, 17, 227–239.
doi:10.3390/molecules17010227
9. Kaushik, N. K.; Kaushik, N.; Attri, P.; Kumar, N.; Kim, C. H.;
Verma, A. K.; Choi, E. H. Molecules 2013, 18, 6620–6662.
doi:10.3390/molecules18066620
10.Martínez, R.; Clara-Sosa, A.; Ramírez Apan, M. T. Bioorg. Med. Chem.
2007, 15, 3912–3918. doi:10.1016/j.bmc.2006.12.018
11.Yuvaraj, T. V.; Unnissa, S. H.; Surendiran, N. S.; Ur rahman, M. A.;
Binumon, V. Asian J. Res. Chem. 2010, 3, 853–858.
12.Batchu, H.; Batra, S. Eur. J. Org. Chem. 2012, 2935–2944.
doi:10.1002/ejoc.201200107
Supporting Information
Supporting Information File 1
Experimental procedures, characterization data, and copies
of the spectra of all compounds.
13.Khalafy, J.; Badparvar, F.; Mariani, A. P. J. Chil. Chem. Soc. 2016, 61,
3112–3115. doi:10.4067/s0717-97072016000300021
14.Gribble, G. W. J. Chem. Soc., Perkin Trans. 1 2000, 1045–1075.
doi:10.1039/a909834h
[https://www.beilstein-journals.org/bjoc/content/
supplementary/1860-5397-16-144-S1.pdf]
15.Vuong, H.; Duarte, S.; Klumpp, D. A. Top. Catal. 2018, 61, 685–688.
doi:10.1007/s11244-018-0908-3
16.Ghiyasabadi, Z.; Bahadorikhalili, S.; Saeedi, M.;
Karimi‐Niyazagheh, M.; Mirfazli, S. S. J. Heterocycl. Chem. 2020, 57,
606–610. doi:10.1002/jhet.3790
Acknowledgements
The authors would like to thank François Dupire (UMR 7053 –
L2CM) and Fabien Lachaud (UMR 7053 – L2CM) for the
HRMS and GC–MS experiments and related discussions. They
thank also the Université de Lorraine and the CNRS for their
support.
17.Irgashev, R. A.; Steparuk, A. S.; Rusinov, G. L. Tetrahedron Lett. 2019,
60, 151185. doi:10.1016/j.tetlet.2019.151185
18.Yu, J.; Xu, J.; Yu, Z.; Jin, Y.; Li, J.; Lv, Y. J. Flow Chem. 2017, 7,
33–36. doi:10.1556/1846.2017.00004
19.Chesnokov, G. A.; Ageshina, A. A.; Topchiy, M. A.; Nechaev, M. S.;
Asachenko, A. F. Eur. J. Org. Chem. 2019, 4844–4854.
doi:10.1002/ejoc.201900772
Funding
The University of Tunis El Manar and the Tunisian Ministry of
Higher Education and Scientific Research are acknowledged for
a grant to D. M.
20.Yao, T.; Yue, D.; Larock, R. C. J. Org. Chem. 2005, 70, 9985–9989.
doi:10.1021/jo0517038
1730

Beilstein J. Org. Chem. 2020, 16, 1722–1731.
21.Zhao, H.; Yuan, H.; Zhang, Y.; Li, R.; Li, W. Org. Lett. 2019, 21,
6557–6561. doi:10.1021/acs.orglett.9b02507
47.Danilkina, N. A.; Bukhtiiarova, N. S.; Govdi, A. I.; Vasileva, A. A.;
Rumyantsev, A. M.; Volkov, A. A.; Sharaev, N. I.; Povolotskiy, A. V.;
Boyarskaya, I. A.; Kornyakov, I. V.; Tokareva, P. V.; Balova, I. A.
Molecules 2019, 24, 2386. doi:10.3390/molecules24132386
48.Attanasi, O. A.; Favi, G.; Filippone, P.; Perrulli, F. R.; Santeusanio, S.
Org. Lett. 2009, 11, 309–312. doi:10.1021/ol802432z
49.South, M. S.; Jakuboski, T. L.; Westmeyer, M. D.; Dukesherer, D. R.
Tetrahedron Lett. 1996, 37, 1351–1354.
22.Yue, D.; Larock, R. C. Org. Lett. 2004, 6, 1037–1040.
doi:10.1021/ol0498996
23.Chen, Y.; Cho, C.-H.; Shi, F.; Larock, R. C. J. Org. Chem. 2009, 74,
6802–6811. doi:10.1021/jo9014003
24.Yue, D.; Yao, T.; Larock, R. C. J. Org. Chem. 2006, 71, 62–69.
doi:10.1021/jo051549p
25.Zhao, G.; Roudaut, C.; Gandon, V.; Alami, M.; Provot, O. Green Chem.
2019, 21, 4204–4210. doi:10.1039/c9gc01880h
doi:10.1016/0040-4039(96)00020-2
50.South, M. S.; Jakuboski, T. L.; Westmeyer, M. D.; Dukesherer, D. R.
J. Org. Chem. 1996, 61, 8921–8934. doi:10.1021/jo960029e
51.South, M. S.; Jakuboski, T. L. Tetrahedron Lett. 1995, 36, 5703–5706.
doi:10.1016/0040-4039(95)01128-5
26.Sathishkumar, P. N.; Prabha, P. S.; Bhuvanesh, N. S. P.; Karvembu, R.
J. Organomet. Chem. 2020, 908, 121087.
doi:10.1016/j.jorganchem.2019.121087
27.Rode, N. D.; Abdalghani, I.; Arcadi, A.; Aschi, M.; Chiarini, M.;
Marinelli, F. J. Org. Chem. 2018, 83, 6354–6362.
52.Chang, M.-Y.; Lu, Y.-J.; Cheng, Y.-C. Tetrahedron 2015, 71,
6840–6845. doi:10.1016/j.tet.2015.07.025
doi:10.1021/acs.joc.8b00508
53.Fukumoto, S.; Imamiya, E.; Kusumoto, K.; Fujiwara, S.; Watanabe, T.;
Shiraishi, M. J. Med. Chem. 2002, 45, 3009–3021.
28.He, Y.-P.; Wu, H.; Wang, Q.; Zhu, J. Angew. Chem., Int. Ed. 2020, 59,
2105–2109. doi:10.1002/anie.201914049
doi:10.1021/jm0104567
29.Arcadi, A.; Cacchi, S.; Fabrizi, G.; Goggiamani, A.; Iazzetti, A.;
Marinelli, F. Org. Biomol. Chem. 2013, 11, 545–548.
doi:10.1039/c2ob27125g
54.Khalafy, J.; Rimaz, M.; Ezzati, M.; Poursattar Marjani, A.
Curr. Chem. Lett. 2013, 2, 43–48. doi:10.5267/j.ccl.2012.11.002
55.Altomare, C.; Cellamare, S.; Summo, L.; Catto, M.; Carotti, A.;
Thull, U.; Carrupt, P.-A.; Testa, B.; Stoeckli-Evans, H. J. Med. Chem.
1998, 41, 3812–3820. doi:10.1021/jm981005y
30.Yao, B.; Wang, Q.; Zhu, J. Angew. Chem., Int. Ed. 2012, 51,
5170–5174. doi:10.1002/anie.201201640
31.Yao, B.; Wang, Q.; Zhu, J. Angew. Chem., Int. Ed. 2013, 52,
12992–12996. doi:10.1002/anie.201307738
56.Chamakh, A.; M'hirsi, M.; Villiéras, J.; Lebreton, J.; Amri, H. Synthesis
2000, 295–299. doi:10.1055/s-2000-6257
32.Zhao, G.; Bignon, J.; Levaique, H.; Dubois, J.; Alami, M.; Provot, O.
J. Org. Chem. 2018, 83, 15323–15332. doi:10.1021/acs.joc.8b02563
33.Krüger (née Alex), K.; Tillack, A.; Beller, M. Adv. Synth. Catal. 2008,
350, 2153–2167. doi:10.1002/adsc.200800409
57.Mawaziny, S.; Lawny, A. M. Phosphorus, Sulfur Silicon Relat. Elem.
2000, 163, 99–120. doi:10.1080/10426500008046614
58.Rezgui, F.; El Gaied, M. M. Tetrahedron Lett. 1998, 39, 5965–5966.
doi:10.1016/s0040-4039(98)01206-4
34.Ho, H. E.; Oniwa, K.; Yamamoto, Y.; Jin, T. Org. Lett. 2016, 18,
2487–2490. doi:10.1021/acs.orglett.6b01067
59.Rezgui, F.; El Gaïed, M. M. Tetrahedron 1997, 53, 15711–15716.
doi:10.1016/s0040-4020(97)10023-0
35.Sperança, A.; Godoi, B.; Menezes, P.; Zeni, G. Synlett 2013, 24,
1125–1132. doi:10.1055/s-0033-1338427
60.Mhasni, O.; Rezgui, F. Tetrahedron Lett. 2010, 51, 586–587.
doi:10.1016/j.tetlet.2009.11.053
36.Zeng, X.; Kinjo, R.; Donnadieu, B.; Bertrand, G. Angew. Chem., Int. Ed.
2010, 49, 942–945. doi:10.1002/anie.200905341
37.Filatova, E. A.; Pozharskii, A. F.; Gulevskaya, A. V.; Ozeryanskii, V. A.
J. Org. Chem. 2015, 80, 872–881. doi:10.1021/jo502363t
38.Heravi, M. M.; Baghernejad, B.; Oskooie, H. A.; Hekmatshoar, R.
Tetrahedron Lett. 2008, 49, 6101–6103.
License and Terms
This is an Open Access article under the terms of the
Creative Commons Attribution License
doi:10.1016/j.tetlet.2008.08.012
(http://creativecommons.org/licenses/by/4.0). Please note
that the reuse, redistribution and reproduction in particular
requires that the authors and source are credited.
39.Wu, S.; Fluxe, A.; Janusz, J. M.; Sheffer, J. B.; Browning, G.; Blass, B.;
Cobum, K.; Hedges, R.; Murawsky, M.; Fang, B.; Fadayel, G. M.;
Hare, M.; Djandjighian, L. Bioorg. Med. Chem. Lett. 2006, 16,
5859–5863. doi:10.1016/j.bmcl.2006.08.057
40.To, Q. H.; Lee, Y. R.; Kim, S. H. Tetrahedron 2014, 70, 8108–8113.
doi:10.1016/j.tet.2014.08.011
The license is subject to the Beilstein Journal of Organic
Chemistry terms and conditions:
41.Lan, X.-C.; Chen, T.-T.; Zhao, Y.; Wu, Y.; Wang, J.; Tu, S.-J.; Jiang, B.;
Hao, W.-J. Tetrahedron Lett. 2017, 58, 1519–1522.
doi:10.1016/j.tetlet.2017.03.009
(https://www.beilstein-journals.org/bjoc)
42.Jiang, B.; Yi, M.-S.; Shi, F.; Tu, S.-J.; Pindi, S.; McDowell, P.; Li, G.
Chem. Commun. 2012, 48, 808–810. doi:10.1039/c1cc15913e
43.Jiang, B.; Li, Q.-Y.; Zhang, H.; Tu, S.-J.; Pindi, S.; Li, G. Org. Lett.
2012, 14, 700–703. doi:10.1021/ol203166c
The definitive version of this article is the electronic one
which can be found at:
doi:10.3762/bjoc.16.144
44.Zhu, C.; Yamane, M. Tetrahedron 2011, 67, 4933–4938.
doi:10.1016/j.tet.2011.04.079
45.Zhao, D.; Wu, Q.; Huang, X.; Song, F.; Lv, T.; You, J. Chem. – Eur. J.
2013, 19, 6239–6244. doi:10.1002/chem.201300155
46.Muralirajan, K.; Cheng, C.-H. Chem. – Eur. J. 2013, 19, 6198–6202.
doi:10.1002/chem.201300922
1731