Organocatalytic Nazarov-type cyclization of 3-alkynyl-2-indolylmethanols: construction of axially chiral cyclopenta[b]indole scaffolds

Ping Wu; Xin-Yu Yan; Song Jiang; Yi-Nan Lu; Wei Tan; Feng Shi

doi:10.20517/cs.2022.42

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Research Article | Open Access | 2 Feb 2023

Organocatalytic Nazarov-type cyclization of 3-alkynyl-2-indolylmethanols: construction of axially chiral cyclopenta[b]indole scaffolds

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Ping Wu^1,2

,

Xin-Yu Yan²

, ...

Feng Shi^1,2,*

Chem Synth 2023;3:6.

10.20517/cs.2022.42 | © The Author(s) 2023.

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Abstract

In recent years, it has become an urgent task to design new types of indole-based platform molecules for Nazarov-type cyclizations and develop organocatalytic Nazarov-type cyclizations for synthesizing indole derivatives. To fulfill this task, in this work, by changing the alkynyl terminal substituent from t-Bu to an aryl group, the reactivity of 3-alkynyl-2-indolylmethanols is modulated and the new platform molecules serve as competent substrates for Brønsted acid-catalyzed Nazarov-type cyclization. Based on this new reactivity, the first organocatalytic Nazarov-type cyclization of aryl-substituted 3-alkynyl-2-indolylmethanols with 2-naphthols is accomplished, leading to the efficient construction of a new class of axially chiral 3, 4-dihydrocyclopenta[b]indole scaffolds. This preliminary investigation of organocatalytic asymmetric Nazarov-type cyclization provides an optional strategy for the atroposelective construction of this new class of axially chiral cyclopenta[b]indole scaffolds. In addition, the first preparation of axially chiral 3, 4-dihydrocyclopenta[b]indole with optical purity is established through chiral resolution, which could serve as a complementary method to catalytic asymmetric approaches.

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Keywords

2-indolylmethanol, Nazarov cyclization, organocatalysis, asymmetric organocatalysis, axial chirality

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INTRODUCTION

Indoles belong to an important nitrogen-containing heterocyclic motif that is present in many bioactive natural products and pharmaceuticals^[1-4]. Therefore, the construction of indole-based frameworks, particularly via organocatalysis, has become an important field of study^[5-8]. Among indole-fused rings, cyclopenta[b]indoles are attractive frameworks^[9-13], which constitute the core structures of many natural products and biologically important compounds, such as yuehchukene^[9], bruceolline I^[10], fischerindole L^[11], thomitrem A^[12] and MK-0524^[13][Figure 1].

Organocatalytic Nazarov-type cyclization of 3-alkynyl-2-indolylmethanols: construction of axially chiral cyclopenta[<i>b</i>]indole scaffolds

Figure 1. Representative natural products and bioactive compounds containing the cyclopenta[b]indole scaffold.

As a result, the construction of such indole-containing scaffolds has remained a long-standing goal in the chemistry community^[14-20] and many synthetic approaches have been developed for the synthesis of these important structural units^[21-29]. Among these approaches, the Nazarov-type cyclization^[30-37] for the construction of 1, 2, 3, 4-tetrahydrocyclopenta[b]indole scaffolds is undoubtedly one of the most step-economical and efficient methods^[38-47]. However, the classical synthesis of such indole derivatives via Nazarov-type cyclizations has largely focused on the Lewis acid (LA)-catalyzed 4π-electrocyclizations of indole-fused 1,4-dien-3-ones, which involve the process of generating a pentadienyl cation (I) intermediate to form the corresponding 1, 2, 3, 4-tetrahydrocyclopenta[b]indoles [Scheme 1A]^[37-41]. Nevertheless, other Nazarov-type cyclizations for the construction of such scaffolds are rather rare^[42-47]. In our previous work, we designed 3-alkenyl-2-indolylmethanols as a new class of indole-based platform molecules for Brønsted acid-catalyzed interrupted Nazarov-type cyclizations with various nucleophiles^[45-47]based on the formation of a pentadienyl cation (II) intermediate to construct 1, 2, 3, 4-tetrahydrocyclopenta[b]indole scaffolds [Scheme 1B]. In spite of these approaches, there are still some challenges in this research field. The first is that the indole-derived substrates suitable for Nazarov-type cyclizations are confined to indole-fused 1, 4-dien-3-ones and 3-alkenyl-2-indolylmethanols. The second is that many Nazarov-type cyclizations are enabled by Lewis acid catalysis and organocatalytic Nazarov-type cyclizations are underdeveloped^[40,48-56], even though organocatalysis has been proven to have tremendous advantages^[57-63]. Therefore, it has become an urgent task to design new types of indole-based platform molecules for Nazarov-type cyclizations and develop organocatalytic Nazarov-type cyclizations for synthesizing indole derivatives.

Scheme 1. Profile of the construction of 1, 2, 3, 4-tetrahydrocyclopenta[b]indole scaffolds via Nazarov-type cyclizations.

To overcome these challenges and fulfill this task, based on our long-lasting interests in synthesizing indole derivatives via designing indole-based platform molecules and their involved organocatalytic reactions^[5-8], we decided to design a new type of indole-based platform molecules for organocatalytic Nazarov-type cyclizations. In our previous work, we designed t-Bu-substituted 3-alkynyl-2-indolylmethanols for constructing axially chiral alkene-indole scaffolds via addition reactions [Scheme 2A]. Specifically, in the presence of a chiral Brønsted acid, this class of 3-alkynyl-2-indolylmethanols transformed into allene-iminium intermediates, which were readily attacked by nucleophiles to undergo 1, 4-addition, thus giving axially chiral alkene-indoles. When using dinucleophiles, the OH group of 2-indolylmethanols undergoes dehydration to give carbocation intermediates^[64-72], which subsequently undergo an intramolecular addition reaction to generate axially chiral cyclic alkene-indoles^[73,74]. In these previous studies, the t-Bu group, as an aliphatic and bulky group, was detrimental to the delocalization of carbocation, thus making this class of 3-alkynyl-2-indolylmethanols unsuitable for Nazarov-type cyclizations. On this basis, we considered changing the t-Bu group to a less steric aryl (Ar) group, thus making aryl-substituted 3-alkynyl-2-indolylmethanols suitable for Nazarov-type cyclizations [Scheme 2B]. This design is based on the consideration that the carbocation can readily undergo 4π electron delocalization due to the existence of the terminal aryl group, therefore undergoing Nazarov-type cyclization and constructing 3, 4-dihydro-cyclopenta[b]indoles.

Scheme 2. Design of a new type of 3-alkynyl-2-indolylmethanols for constructing 3, 4-dihydrocyclopenta[b]indoles via organocatalytic Nazarov-type cyclization.

Based on this concept, we design an organocatalytic Nazarov-type cyclization of aryl-substituted 3-alkynyl-2-indolylmethanols with 2-naphthols [Scheme 2C]. The selection of 2-naphthols as suitable nucleophiles is based on the consideration that 2-naphthols^[75-77] are easily activated by Brønsted acids through the interaction of hydrogen bonding. It is noteworthy that 2-naphthols with a planar structure and the effect of steric congestion should lead to the formation of a C-C bond as a chiral axis^[78-80], thus endowing the constructed cyclopenta[b]indole frameworks with axial chirality^[81-89]. Therefore, the significance of this work is threefold: (1) modulating the terminal substituents of 3-alkynyl-2-indolylmethanols to achieve different reactivities; (2) the first organocatalytic Nazarov-type cyclization of aryl-substituted 3-alkynyl-2-indolylmethanols; (3) the efficient construction of a new class of axially chiral 3, 4-dihydrocyclopenta[b]indole scaffolds.

EXPERIMENTAL

To a mixture of 3-phenyl-2-indolylmethanol 1 (0.30 mmol), 2-naphthol 2 (0.2 mmol) and catalyst 4a (7.0 mg, 0.02 mmol) was added CHCl₃ (1 mL). The reaction mixture was then stirred at 30 °C for 12 h. After the completion of the reaction, which was indicated by thin layer chromatography, the reaction mixture was directly purified through column chromatography on silica gel (petroleum ether:dichloromethane = 2:1 as eluent) to afford pure product 3.

RESULTS AND DISCUSSION

Based on this design, we initially attempted the reaction of 3-alkynyl-2-indolylmethanol 1a bearing a terminal phenyl group with 2-naphthol 2a in the presence of 10 mol% racemic phosphoric acid 4a in chloroform (CHCl₃) at 20 °C for 12 h [Table 1 and entry 1]. Gratifyingly, the designed Nazarov-type cyclization occurred in a facile manner to afford cyclopenta[b]indole 3aa in a moderate yield of 55%. A series of Brønsted acids 4 were then evaluated for the reaction (entries 2-7), which revealed that p-toluenesulfonic acid monohydrate 4c (TsOH^.H₂O) and trifluoromethanesulfonic acid 4d (TfOH) could catalyze the reaction to some extent (entries 3 and 4), whereas other Brønsted acids could barely catalyze the reaction and only trace amounts of product were observed (entries 2 and 5-7). Therefore, racemic phosphoric acid 4a was selected as the optimal catalyst for this Nazarov-type cyclization. Subsequently, several different types of solvents were screened (entries 8-12). It was found that the reaction could only occur in chloroform (entry 1) and toluene (entry 8), with chloroform acting as a better reaction medium in terms of yield. To further improve the yield of this model reaction, other reaction parameters, such as reagent ratio and reaction concentration and temperature, were modulated (entries 13-20). It was found that the yield of product 3aa could be improved by modulating the ratio of 1a and 2a (entries 13-15). When the ratio was adjusted to 1.5:1, the yield of product 3aa could be increased to 70% (entry 15). In addition, the subsequent evaluation of the reaction concentration (entries 16-18) revealed that a higher concentration was helpful for increasing the yield (entry 16), i.e., when the reaction was performed in 0.5 mL CHCl₃, product 3aa could be obtained in a higher yield of 76% (entry 16). Finally, slightly modulating the reaction temperature (entries 19 and 20) resulted in the yield of product 3aa being further improved to 85% when performing the reaction at 30 °C (entry 19). Therefore, the optimal conditions for the Nazarov-type cyclization were set as those of entry 19.

Table 1

Screening of catalysts and optimization of reaction conditions^a


Entry	Cat.	Solvent	T (^oC)	1a: 2a	Yield (%)^b
1	4a	CHCl₃	20	1:1.2	55
2	4b	CHCl₃	20	1:1.2	trace
3	4c	CHCl₃	20	1:1.2	45
4	4d	CHCl₃	20	1:1.2	11
5	4e	CHCl₃	20	1:1.2	trace
6	4f	CHCl₃	20	1:1.2	trace
7	4g	CHCl₃	20	1:1.2	trace
8	4a	toluene	20	1:1.2	43
9	4a	acetone	20	1:1.2	trace
10	4a	MeCN	20	1:1.2	trace
11	4a	THF	20	1:1.2	trace
12	4a	EtOAc	20	1:1.2	trace
13	4a	CHCl₃	20	1:1.5	64
14	4a	CHCl₃	20	1.2:1	62
15	4a	CHCl₃	20	1.5:1	70
16^c	4a	CHCl₃	20	1.5:1	76
17^d	4a	CHCl₃	20	1.5:1	61
18^e	4a	CHCl₃	20	1.5:1	37
19^c	4a	CHCl₃	30	1.5:1	85
20^c	4a	CHCl₃	40	1.5:1	79

^aUnless otherwise indicated, the reaction was carried out at a 0.1 mmol scale and catalyzed by 10 mol% Cat. in a solvent (1.0 mL) at the indicated temperature for 12 h; ^bIsolated yield; ^cPerformed in 0.5 mL of CHCl₃; ^dPerformed in 2.0 mL of CHCl₃; ^ePerformed in 3.0 mL of CHCl₃.

With the optimal reaction conditions determined, we then investigated the substrate scope of the Nazarov-type cyclization [Figure 2]. First, the substrate scope of the 3-alkynyl-2-indolylmethanols 1 was studied by reactions with indole 2a. As shown in Figure 2, the Brønsted acid-catalyzed Nazarov-type cyclization was compatible with a variety of substrates 1 bearing different R/Ar/Ar¹substituents, which successfully participated in the reaction to give the expected 3, 4-dihydrocyclopenta[b]indoles 3 in moderate to good yields. Specifically, the terminal Ar substituents of the alkyne functionality in the structures of 3-alkynyl-2-indolylmethanols 1 could be para- and meta-substituted phenyl groups with different electronic natures and these substrates successfully engaged in the reaction to deliver the corresponding products 3ba-3ga in generally high yields. In addition, the R substituents on the indole ring could be changed and C5- and C6-substituted substrates 1h-1j were employed in the reaction for synthesizing 3, 4-dihydrocyclopenta[b]indoles 3ha-3ja in moderate yields. Regarding the Ar¹ substituents, meta- and para-substituted phenyl groups with either electron-donating or electron-withdrawing properties proved to be suitable substituents for substrates 1k-1n, which readily took part in the Nazarov-type cyclization to give the desired 3, 4-dihydrocyclopenta[b]indole products 3ka-3na in moderate to good yields (57%-71%).

Figure 2. Substrate scope of Nazarov-type cyclization. Reaction conditions: 0.2 mmol scale; 10 mol% 4a; CHCl₃ (1.0 mL); 30 ℃; 12 h; 1:2 = 1.5:1. Isolated yields.

Next, the substrate scope of 2-naphthols 2 was investigated by the Nazarov-type cyclization with 3-alkynyl-2-indolylmethanol 1a. As shown in Figure 2, this reaction was amenable to a series of C6- and C7-substituted 2-naphthols 2b-2i, which underwent the Nazarov-type cyclization to afford the desired products 3ab-3ai in moderate to good yields. In detail, C6-substituted 2-naphthols 2, regardless of their electronic nature, could be applicable to the reaction, and it was found that 2-naphthol 2c with an electron-donating group could give product 3ac in the highest yield of 86%. For C7-substituted 2-naphthols 2, various substituents with electron-donating or electron-withdrawing properties were tolerant to the reaction and 2-naphthol 2g with a C7-methoxyl group could furnish product 3ag in a high yield of 81%. Interestingly, 2-naphthalenethiol 2j serving as an analogue of 2-naphthol 2a could be employed for the Nazarov-type cyclization under the standard conditions, giving product 3aj in a moderate yield.

In addition, we performed a 1 mmol scale reaction of 3-alkynyl-2-indolylmethanol 1a with 2-naphthol 2a under the optimal reaction conditions [Scheme 3A]. In this case, product 3aa was afforded in a high yield of 80%, which demonstrated that this Brønsted acid-catalyzed Nazarov-type cyclization could be scaled up and should have potential applications. In order to gain some insights into the organocatalytic Nazarov-type cyclization, we performed some control experiments [Scheme 3B]. First, N-methyl-protected 3-alkynyl-2-indolylmethanol 1o was employed as a substrate to the reaction with 2-naphthol 2a under the standard reaction conditions with no reaction observed, which indicated that the NH group of 3-alkynyl-2-indolylmethanol 1 played an important role in controlling the reactivity. Second, O-methyl-protected substrate 2k was used as a nucleophile to react with 1a and still no reaction occurred. This result demonstrated that the OH group of substrate 2 was necessary for performing the reaction.

Scheme 3. One mmol scale reaction and control experiments.

Based on the control experiments, a possible reaction pathway and activation mode of this Brønsted acid-catalyzed reaction were proposed [Scheme 4]. As exemplified by the model reaction, 3-alkynyl-2-indolylmethanol 1a was initially transformed into allene-iminium intermediate A under the activation of Brønsted acid 4a via hydrogen-bonding interaction. Subsequently, catalyst 4a simultaneously activated allene-iminium intermediate A and 2-naphthol 2a via forming two hydrogen bonds, thus facilitating a 1, 4-addition between them to generate intermediate B. Intermediate B then experienced a dehydration process under the catalysis of Brønsted acid 4a to give carbocation C, which was easily converted into 4π carbocation D due to electron delocalization. Finally, activated by catalyst 4a via the interactions of hydrogen bonding and ion pairing, intermediate D underwent a Nazarov-type cyclization to form the cyclic carbocation intermediate E, which immediately underwent α-H elimination to deliver 3, 4-dihydrocyclopenta[b]indole 3aa with the regeneration of catalyst 4a.

Scheme 4. Suggested reaction pathway.

Because this class of 3, 4-dihydrocyclopenta[b]indole scaffolds 3 contains a carbon-carbon chiral axis, we then carried out a preliminary investigation on the organocatalytic asymmetric version of the Nazarov-type cyclization. In fact, in recent years, the catalytic asymmetric construction of axially chiral indole-based scaffolds has become an emerging area of study^[8,78] due to the importance of such scaffolds in many natural products^[90-92], bioactive molecules^[93,94] and chiral catalysts or ligands^[95-101]. Although a number of axially chiral indole-based scaffolds, such as N-arylindoles^[102-110], 3-arylindoles^[111-120], 2-arylindoles^[121-127], 3-quinonylindoles^[128,129], isochromenone-indoles^[130], bisindoles^[131-135] and other indole derivatives^[136-143], have been successfully synthesized, the catalytic asymmetric construction of axially chiral 3, 4-dihydrocyclopenta[b]indole scaffolds is unknown. As shown in Table 2, a series of chiral phosphoric acids (CPAs)^[144-151]5-7 were chosen as chiral organocatalysts to promote the reaction between 1a and 2a (entries 1-13). As expected, axially chiral cyclopenta[b]indole 3aa could be obtained in an atroposelective manner. Particularly, when CPA (S)-5f was used as a chiral organocatalyst, axially chiral product 3aa was generated with an atroposelectivity of 47% ee, albeit with an extremely low yield of 7% (entry 6). Under the catalysis of CPA (S)-5f, several different types of solvents were examined (entries 14-18), which disclosed that only toluene could serve as an effective reaction media to deliver axially chiral product 3aa in 69% ee and 11% yield (entry 14). Subsequently, to further improve the atroposelectivity and the yield of product 3aa, we attempted to modulate the catalyst loading in the reaction (entries 19 and 20). When the catalyst loading of (S)-5f was increased to 20 mol%, product 3aa was generated in a slightly improved yield of 20% with the retained atroposelectivity of 69% ee (entry 20). These preliminary results implied that simultaneously controlling both the enantioselectivity and the yield of this organocatalytic asymmetric Nazarov-type cyclization is a significant challenge. Although the yield and atroposelectivity of axially chiral product 3aa in this organocatalytic asymmetric version are not satisfactory, this organocatalytic asymmetric Nazarov-type cyclization provides an optional strategy for the atroposelective construction of this new class of axially chiral cyclopenta[b]indole scaffolds.

Table 2

Preliminary investigation of organocatalytic asymmetric version of Nazarov-type cyclization^a


Entry	Cat.	Solvent	Yield (%)^b	ee (%)^c
1	5a	CHCl₃	85	12
2	5b	CHCl₃	32	10
3	5c	CHCl₃	trace	-
4	5d	CHCl₃	21	27
5	5e	CHCl₃	10	4
6	5f	CHCl₃	7	47
7	5g	CHCl₃	trace	-
8	5h	CHCl₃	89	2
9	5i	CHCl₃	47	10
10	6a	CHCl₃	58	15
11	6b	CHCl₃	trace	-
12	7a	CHCl₃	34	16
13	7b	CHCl₃	trace	-
14	5f	toluene	11	69
15	5f	EtOAc	trace	-
16	5f	THF	trace	-
17	5f	MeCN	trace	-
18	5f	acetone	trace	-
19^d	5f	toluene	9	68
20^e	5f	toluene	20	69

^aUnless otherwise indicated, the reaction was carried out at a 0.1 mmol scale and catalyzed by 10 mol% Cat. in a solvent (1.0 mL) at 30 °C for 18 h and the molar ratio of 1a:2a was 1.2:1; ^bIsolated yield; ^cEnantiomeric excess (ee) was determined by high-performance liquid chromatography; ^dCatalyzed by 5 mol% 5f; ^eCatalyzed by 20 mol% 5f.

Finally, to obtain the two enantiomers of axially chiral 3aa, we tried using the strategy of chiral resolution [Scheme 5]. In detail, the racemic compound rac-3aa was subjected to the acylation reaction with (R)-(-)-O-formylmandeloyl chloride (R)-8 as a resolution reagent in the presence of DMAP, which gave rise to two separable diastereomers (S_a, R)-9 and (R_a, R)-9. By treating with hydrazine hydrate, the two diastereomers were then easily transformed into the corresponding single enantiomers (S_a)-3aa and (R_a)-3aa, respectively, in high yields with excellent atroposelectivities. In this manner, the first preparation of axially chiral 3, 4-dihydrocyclopenta[b]indoles with optical purity was established, which could serve as a complementary method to catalytic asymmetric approaches. Moreover, the absolute configuration of product (S_a)-3aa was determined by X-ray diffraction analysis^[152] of its single crystal (see Supplementary Materials), which was obtained by recrystallization.

Scheme 5. Preparation of (S_a)-3aa and (R_a)-3aa by the strategy of chiral resolution.

CONCLUSION

In summary, by changing the alkynyl terminal substituent from t-Bu to an aryl group, the reactivity of 3-alkynyl-2-indolylmethanols was modulated as competent platform molecules for Brønsted acid-catalyzed Nazarov-type cyclization. Based on this new reactivity, we accomplished the first organocatalytic Nazarov-type cyclization of aryl-substituted 3-alkynyl-2-indolylmethanols with 2-naphthols, thus realizing the efficient construction of a new class of axially chiral 3, 4-dihydrocyclopenta[b]indole scaffolds. The preliminary investigation on the organocatalytic asymmetric Nazarov-type cyclization provided an optional strategy for atroposelective construction of this new class of axially chiral cyclopenta[b]indole scaffolds. In addition, we realized the first preparation of axially chiral 3, 4-dihydrocyclopenta[b]indoles with optical purity by the strategy of chiral resolution, which could serve as a complementary method to catalytic asymmetric approaches. This work will not only add new contents to the chemistry of Nazarov-type cyclization and indolylmethanols, but also contribute to the research field of constructing axially chiral indole-based scaffolds via asymmetric organocatalysis.

DECLARATIONS

Acknowledgments

We sincerely thank all the group members who are involved in the development of new kinds of indolylmethanols as platform molecules.

Authors’ contributions

Performing the majority of the experiments: Wu P

Doing some of the experiments: Yan XY, Jiang S

Initially trying the model reaction: Lu YN

Co-directing this project and writing the draft manuscript: Tan W

Directing this project and revising the manuscript: Shi F

Availability of data and materials

Supplementary Materials are available online for this paper.

Financial support and sponsorship

We thank National Natural Science Foundation of China (22125104 and 21831007), Natural Science Foundation of Jiangsu Province (BK20210916) and High Education Natural Science Foundation of Jiangsu Province (No. 21KJB150009) for financial support.

Conflicts of interest

The author declared that there is no conflict of interest.

Ethical approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Copyright

Supplementary Materials

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Cite This Article

Research Article

Open Access

Organocatalytic Nazarov-type cyclization of 3-alkynyl-2-indolylmethanols: construction of axially chiral cyclopenta[b]indole scaffolds

Ping Wu, ... Feng Shi

How to Cite

Wu, P.; Yan, X. Y.; Jiang, S.; Lu, Y. N.; Tan, W.; Shi, F. Organocatalytic Nazarov-type cyclization of 3-alkynyl-2-indolylmethanols: construction of axially chiral cyclopenta[b]indole scaffolds. Chem. Synth. 2023, 3, 6. http://dx.doi.org/10.20517/cs.2022.42

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This article belongs to the Special Issue Celebrating the 45th Anniversary of Changzhou University - Applications and Future Prospects of Asymmetric Organocatalysis

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© The Author(s) 2023. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, sharing, adaptation, distribution and reproduction in any medium or format, for any purpose, even commercially, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Author Biographies

Ping Wu

Ping Wu joined the group of Prof. Feng Shi when he was an undergraduate student in 2016. He received his Bachelor's degree and M.S. degree from Jiangsu Normal University in 2019 and 2022, respectively. In 2022, he started to pursue his Ph.D. degree under the supervision of Prof. Feng Shi and Prof. Yu Peng. His current research interests focus on designing new organocatalytic asymmetric reactions for constructing chiral indole scaffolds. He has published 7 research papers in international peer-reviewed journals.

Xin-Yu Yan

Xin-Yu Yan joined the group of Prof. Feng Shi when he was an undergraduate student in 2019. His current research interests focus on the organocatalytic cycloaddition reaction for the synthesis of indole derivatives. He has published 2 research papers in international peer-reviewed journals.

Song Jiang

Song Jiang joined the group of Prof. Feng Shi when she was an undergraduate student in 2020. Her current research interests focus on the organocatalytic cycloaddition reaction for the synthesis of indole derivatives. She has published 2 research papers in international peer-reviewed journals.

Yi-Nan Lu

Yi-Nan Lu joined the group of Prof. Feng Shi in 2017 to pursue her Master’s degree at Jiangsu Normal University. After receiving her Master’s degree in 2020, she started to pursue her Ph.D. degree under the supervision of Prof. Chun-Jiang Wang at Wuhan University. Her current research interests focus on visible light-induced photochemical synthesis. She has published 6 research papers in international peer-reviewed journals.

Wei Tan

Wei Tan received his Master's degree in 2015 from Jiangsu Normal University and received his Ph.D. degree from East China Normal University in 2019. Then, he joined Jiangsu Normal University as a faculty member and was appointed as an associate professor in 2021. His current research interests focus on organocatalytic asymmetric construction of axially chiral scaffolds and catalytic asymmetric synthesis of chiral bioactive molecules. He has published over 20 research papers in peer-reviewed journals.

Feng Shi

Feng Shi received her bachelor's degree and master's degree from Jiangsu Normal University in 1998 and 2004, respectively. She received her Ph.D. degree in 2013 at Soochow University and University of Science and Technology of China. She started her independent career in 2013 and was appointed as a Full Professor at Jiangsu Normal University in 2015. She was appointed as a Distinguished Professor at Changzhou University in 2022. Her research interests focus on organocatalytic asymmetric reactions for the construction of chiral heterocyclic frameworks, particularly the construction of chiral indole-based scaffolds. She has published more than 130 papers as a corresponding author in peer-reviewed international journals. She is supported by the National Science Fund for Distinguished Young Scholars from the National Natural Science Foundation of China and received the Outstanding Youth Funds of Jiangsu Province. She has received some awards and honors such as the Natural Science Award of Jiangsu Province, the NHU-CJC Innovation Award, the Thieme Chemistry Journal Award and the Asian Core Program Lectureship Award. She is a member of the editorial board for Chem. Synth., Eur. J. Org. Chem., Chin. J. Org. Chem. and a member of the international advisory board for Org. Chem. Front., J. Org. Chem. and Synthesis.

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