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Kalar PL, Jain K, Agrawal S, Khan S, Vishwakarma R, Shivhare A, Deshmukh MM, Das K. Green Synthesis of Electrophilic Alkenes Using a Magnesium Catalyst under Aqueous Conditions and Mechanistic Insights by Density Functional Theory. J Org Chem 2023. [PMID: 38038383 DOI: 10.1021/acs.joc.3c01540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2023]
Abstract
A green approach for the synthesis of electrophilic alkenes has been developed via Knoevenagel condensation between active methylene compounds and carbonyl compounds using Mg powder under aqueous conditions. In this strategy, Mg(OH)2 acts as a catalyst, which was generated in situ by the reaction between metallic Mg (20 mol %) and water. Mg was found to be an efficient, nontoxic, and inexpensive metal catalyst system for producing a range of electrophilic alkenes in excellent yields (≤98%). A gram-scale synthesis of electrophilic alkenes has been developed, and Mg metal was recovered and recycled up to three times without an appreciable loss of catalytic activity. A catalytic cycle was proposed, and the reaction mechanism was investigated using density functional theory. The key steps are enolization of ethyl cyanoacetate, C-C bond formation, and then regeneration of the catalyst via metathesis with H2O. The overall reaction occurs easily with a maximum ΔG°⧧ value of 7.9 kcal/mol for the rate-determining C-C bond formation step. Our protocol has several advantages and can be further extended to one-pot sequential Knoevenagel condensation and Michael addition, and one-pot sequential Knoevenagel condensation and chemoselective reduction can be used for the synthesis of valuable precursors of pharmaceutical products under green and aqueous conditions.
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Affiliation(s)
- Pankaj Lal Kalar
- Department of Chemistry, School of Chemical Sciences and Technology, Dr. Harisingh Gour Central University, Sagar 470 003, Madhya Pradesh, India
| | - Kavita Jain
- Department of Chemistry, School of Chemical Sciences and Technology, Dr. Harisingh Gour Central University, Sagar 470 003, Madhya Pradesh, India
| | - Swatantra Agrawal
- Department of Chemistry, School of Chemical Sciences and Technology, Dr. Harisingh Gour Central University, Sagar 470 003, Madhya Pradesh, India
| | - Siddique Khan
- Department of Chemistry, School of Chemical Sciences and Technology, Dr. Harisingh Gour Central University, Sagar 470 003, Madhya Pradesh, India
| | - Rampal Vishwakarma
- School of Chemical Science, National Institute of Science Education and Research, OCC of HBNI, Bhubaneswar 752050, Odisha, India
| | - Ayush Shivhare
- Department of Chemistry, School of Chemical Sciences and Technology, Dr. Harisingh Gour Central University, Sagar 470 003, Madhya Pradesh, India
| | - Milind M Deshmukh
- Department of Chemistry, School of Chemical Sciences and Technology, Dr. Harisingh Gour Central University, Sagar 470 003, Madhya Pradesh, India
| | - Kalpataru Das
- Department of Chemistry, School of Chemical Sciences and Technology, Dr. Harisingh Gour Central University, Sagar 470 003, Madhya Pradesh, India
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Yasui M, Fujioka H, Takeda N, Ueda M. Anhydrous Hydrogen Iodide-Mediated Reductive Indolization of In Situ-Generated Cyclopropyl Hydrazones. Org Lett 2021; 24:43-47. [PMID: 34881907 DOI: 10.1021/acs.orglett.1c03607] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Fischer-type indolization of N-aryl-C-cyclopropyl hydrazones generated in situ followed by chemoselective reduction using tert-butyl iodide as an anhydrous HI generator was developed. This protocol provides indoles bearing carboxylic acid derivative units. A series of control experiments indicated the HI-mediated formation and reduction of spirocyclopropyl indolenines. Anhydrous HI functions as a Brønsted acid as well as a reducing agent, facilitating the successful conversion of unstable reaction intermediates and iodinated mixtures in equilibrium.
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Affiliation(s)
- Motohiro Yasui
- Kobe Pharmaceutical University, Motoyamakita, Higashinada, Kobe 658-8558, Japan
| | - Hiroki Fujioka
- Kobe Pharmaceutical University, Motoyamakita, Higashinada, Kobe 658-8558, Japan
| | - Norihiko Takeda
- Kobe Pharmaceutical University, Motoyamakita, Higashinada, Kobe 658-8558, Japan
| | - Masafumi Ueda
- Kobe Pharmaceutical University, Motoyamakita, Higashinada, Kobe 658-8558, Japan
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