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Tanaka H, Yasui T, Uyanik M, Ishihara K. 1,3-Migrative Ring Expansion of Spiroindolenines to Azepino[3,4- b]indoles. Org Lett 2023; 25:2377-2381. [PMID: 36847223 DOI: 10.1021/acs.orglett.3c00207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/01/2023]
Abstract
We serendipitously found an unprecedented 5-to-7-membered ring expansion of 2-alkylspiroindolenines to azepinoindoles mediated by n-tetrabutylammonium fluoride. The starting materials can be easily prepared by the hypoiodite-catalyzed oxidative dearomative spirocyclization of indole derivatives. Mildly basic conditions and electron-deficient protecting groups for the amines were found to be crucial to promoting chemoselective reactions. Moreover, the ring expansion of aniline-derived spiroindolenines proceeds smoothly under much milder conditions using only a catalytic amount of cesium carbonate.
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Affiliation(s)
- Hiroki Tanaka
- Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8603, Japan
| | - Toshihiro Yasui
- Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8603, Japan
| | - Muhammet Uyanik
- Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8603, Japan
| | - Kazuaki Ishihara
- Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8603, Japan
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2
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Said MS, Khonde NS, Kumar P, Gajbhiye JM. Electron-Deficient Fluoroarene-Mediated Synthesis of Trifluoromethyl Ketones from Carboxylic Acids. Org Lett 2023; 25:1094-1098. [PMID: 36757825 DOI: 10.1021/acs.orglett.2c04318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
Fluoroarene-mediated trifluoromethylation of carboxylic acids for the synthesis of trifluoromethyl ketones is disclosed. The fluoroarene activates the acid group and generates the fluoride source in situ for the trifluoromethylation reaction. The present protocol is safe and metal-free, operates under mild reaction conditions, and does not require any external additives to generate trifluoromethyl anion. The current transformation provides good functional group tolerance and also delivers 92% and 88% yields of trifluoromethyl ketones in batch and continuous flow, respectively.
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Affiliation(s)
- Madhukar S Said
- Division of Organic Chemistry, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Nilesh S Khonde
- Division of Organic Chemistry, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Pradeep Kumar
- Division of Organic Chemistry, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Jayant M Gajbhiye
- Division of Organic Chemistry, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
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3
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Pupo G, Gouverneur V. Hydrogen Bonding Phase-Transfer Catalysis with Alkali Metal Fluorides and Beyond. J Am Chem Soc 2022; 144:5200-5213. [PMID: 35294171 PMCID: PMC9084554 DOI: 10.1021/jacs.2c00190] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Phase-transfer catalysis (PTC) is one of the most powerful catalytic manifolds for asymmetric synthesis. Chiral cationic or anionic PTC strategies have enabled a variety of transformations, yet studies on the use of insoluble inorganic salts as nucleophiles for the synthesis of enantioenriched molecules have remained elusive. A long-standing challenge is the development of methods for asymmetric carbon-fluorine bond formation from readily available and cost-effective alkali metal fluorides. In this Perspective, we describe how H-bond donors can provide a solution through fluoride binding. We use examples, primarily from our own research, to discuss how hydrogen bonding interactions impact fluoride reactivity and the role of H-bond donors as phase-transfer catalysts to bring solid-phase alkali metal fluorides in solution. These studies led to hydrogen bonding phase-transfer catalysis (HB-PTC), a new concept in PTC, originally crafted for alkali metal fluorides but offering opportunities beyond enantioselective fluorination. Looking ahead, the unlimited options that one can consider to diversify the H-bond donor, the inorganic salt, and the electrophile, herald a new era in phase-transfer catalysis. Whether abundant inorganic salts of lattice energy significantly higher than those studied to date could be considered as nucleophiles, e.g., CaF2, remains an open question, with solutions that may be found through synergistic PTC catalysis or beyond PTC.
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Affiliation(s)
- Gabriele Pupo
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Véronique Gouverneur
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K
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Zeng JL, Xu ZH, Niu LF, Yao C, Liang LL, Zou YL, Yang L. Generating Monofluoro‐Substituted Amines and Amino Acids by the Interaction of Inexpensive KF and Sulfamidates. European J Org Chem 2022. [DOI: 10.1002/ejoc.202200001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Jun-Liang Zeng
- Xuchang University College of chemical and materials engineering 88 Bayi Road, Weidu District, 461000 Xuchang City CHINA
| | - Zhi-Hong Xu
- Xuchang University college of chemical and materials engineering CHINA
| | - Liang-Feng Niu
- Xuchang University college of chemical and materials engineering CHINA
| | - Chuan Yao
- Xuchang University college of chemical and matericals engineering CHINA
| | - Lu-Lu Liang
- Xuchang University college of chemical and materials engineering CHINA
| | - Yu-Lu Zou
- Xuchang University college of chemical and matericals engineering CHINA
| | - Lijun Yang
- Chinese Academy of Medical Sciences & Peking Union Medical College key laboratory of radiopharmacokinetics for innovative drugs CHINA
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Patil NB, Atapalkar RS, Chavan SP, Kulkarni AA. Multi-Step Synthesis of Miltefosine: Integration of Flow Chemistry with Continuous Mechanochemistry. Chemistry 2021; 27:17695-17699. [PMID: 34697844 DOI: 10.1002/chem.202103499] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Indexed: 11/09/2022]
Abstract
Herein we report for the first time, an advanced continuous flow synthesis of the blockbuster Leishmaniasis drug miltefosine from simple starting materials by a sequence involving four steps of chemical transformation including a continuous mechanochemical step. First three reaction steps were performed in simple tubular reactors in a telescopic mode, while in the last step the product precipitated from the 3rd step was used for a continuous mechanochemical synthesis of miltefosine. When compared to a typical batch protocol that takes 15 h, miltefosine was obtained in 58 % overall yield in flow synthesis mode at the laboratory scale in a total residence time 34 min at synthesis rate of 10 g/hr, which is sufficient to treat 4800 patients per day.
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Affiliation(s)
- Niteen B Patil
- Division of Organic Chemistry, CSIR-National Chemical Laboratory, Pune, 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India
| | - Ranjit S Atapalkar
- Chemical Engineering & Process Development, CSIR-National Chemical Laboratory, Pune, 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India
| | - Subhash P Chavan
- Division of Organic Chemistry, CSIR-National Chemical Laboratory, Pune, 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India
| | - Amol A Kulkarni
- Chemical Engineering & Process Development, CSIR-National Chemical Laboratory, Pune, 411008, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India
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Pliego JR. The role of intermolecular forces in ionic reactions: the solvent effect, ion-pairing, aggregates and structured environment. Org Biomol Chem 2021; 19:1900-1914. [PMID: 33554992 DOI: 10.1039/d0ob02413a] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The environment enclosing an ionic species has a critical effect on its reactivity. In a more general sense, medium effects are not limited to the solvent, but involve the counter ion effect (ion pairing), formation of larger aggregates and structured environment as provided by the host in the case of host-guest complexes. In this review, a general view of the medium effect on anion-molecule reactions is presented. Nucleophilic substitution reactions of aliphatic (SN2) and aromatic (SNAr) systems, as well as elimination reactions (E2), are the focus of the discussion. In particular, nucleophilic fluorination with KF, CsF and tetraalkylammonium fluoride was used as the main model, because of the importance of this kind of reaction and the recent advances in the study of these systems. The solvent effect, ion pairing, formation of aggregates and formation of complexes with crown ethers, cryptands and calixarenes are discussed. For a deeper insight into the medium effect, many results of reliable theoretical calculations in close agreement with experiments were chosen as examples.
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Affiliation(s)
- Josefredo R Pliego
- Departamento de Ciências Naturais, Universidade Federal de São João del-Rei, 36301-160, São João del-Rei, MG, Brazil.
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Abstract
Nanocellulose (NC) is a biomaterial with growing interest in the field of nanocomposites and sustainable materials. NC has various applications including biodegradable materials, reinforcing agents, packaging films, transpiring membranes and medical devices. Among the many applications, the use of NC functionalized with organic and inorganic groups has found wide use as a catalyst in chemical transformations. The goal of this review is to collect the current knowledge on its catalytic applications for chemical groups conversion. We have chosen to organize the manuscript according to subdivision of NC into Bacterial Nanocellulose (BNC), Cellulose Nanocrystals (CNCs), and Cellulose Nanofibers (CNFs) and their role as inorganic- and organic-functionalized NC-catalysts in organic synthesis. However, in consideration of the fact that the literature on this field is very extensive, we have decided to focus our attention on the scientific productions of the last five years.
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