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Sahoo S, Manna S, Rit A. Unravelling a bench-stable zinc-amide compound as highly active multitasking catalyst for radical-mediated selective alk(en)ylation of unactivated carbocycles under mild conditions. Chem Sci 2024; 15:5238-5247. [PMID: 38577381 PMCID: PMC10988604 DOI: 10.1039/d3sc06334h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 02/20/2024] [Indexed: 04/06/2024] Open
Abstract
The direct functionalization of unactivated organic moieties via C-C bond formation has long fascinated synthetic chemists. Although base-metal systems are steadily emerging in this area, achieving multitasking activity in a single catalyst to execute several such functionalizations under mild conditions is challenging. To address this, we herein report an effective protocol for the selective C-alk(en)ylation of indene/fluorene with alcohol as a green alkylating agent employing a naturally abundant and eco-friendly zinc-derived compound, for the first time. Notably, this study unveils the unique potential of a bench-stable Zn compound bearing an amidated imidazolium salt towards C-C bond-forming reactions utilizing an array of alcohols, ranging from aliphatic to aromatic and, attractively, even secondary alcohols. Moreover, this readily scalable protocol, which proceeds via an underdeveloped radical-mediated borrowing hydrogen protocol (an aldehyde is generated from an alcohol, and subsequent condensation with indene/fluorene provides the corresponding alkenylated products) established based on a range of control experiments, works effortlessly under mild conditions using a low catalyst loading. Notably, this approach affords remarkable selectivity towards alkylated or alkenylated products with a high level of functional group tolerance and chemoselectivity. Crucially, the catalytic activity of these Zn compounds can be attributed to their hydrogen atom transfer (HAT) capability, while their selectivity towards different products can be understood in terms of employed reaction conditions. Lastly, the synthetic utility of obtained products was showcased by their late-stage functionalization to access unsymmetrical 9,9-disubstituted fluorenes, which are potentially useful for various optoelectronic applications.
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Affiliation(s)
- Sangita Sahoo
- Department of Chemistry, Indian Institute of Technology Madras Chennai 600036 India
| | - Subarna Manna
- Department of Chemistry, Indian Institute of Technology Madras Chennai 600036 India
| | - Arnab Rit
- Department of Chemistry, Indian Institute of Technology Madras Chennai 600036 India
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Kamal, Samanta S. Noninnocent Azo-Aromatic Cobalt(II)-Catalyzed sp 3 C-H Alkylation of Fluorenes with Alcohols. J Org Chem 2024; 89:1910-1926. [PMID: 38205792 DOI: 10.1021/acs.joc.3c02657] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2024]
Abstract
Herein, employing well-defined redox noninnocent cobalt(II) complexes an efficient sp3 C-H alkylation of fluorenes using alcohols as alkylating agents to result in alkylated fluorenes is reported. The catalytic protocol was versatile with various fluorenes and benzyl alcohols. It also showed very good functional group tolerance with both alcohols and fluorenes. Moreover, an efficient single-step and simultaneous di C-C as well as both C-C and the C-N alkylation reaction of fluorenes was observed with this catalytic protocol. Such selective single-step dialkylation of fluorenes is indeed beneficial. Several control experiments, deuterium labeling, and 1H NMR kinetic studies have revealed a ligand radical-based borrowing hydrogen mechanism involving the azo-aromatic complexes of cobalt as catalysts for the alkylation of fluorenes.
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Affiliation(s)
- Kamal
- Department of Chemistry, Indian Institute of Technology (IIT) Jammu, Jagti, Jammu, Jammu & Kashmir 181221, India
| | - Subhas Samanta
- Department of Chemistry, Indian Institute of Technology (IIT) Jammu, Jagti, Jammu, Jammu & Kashmir 181221, India
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Swatiputra AA, Mukherjee D, Dinda S, Roy S, Pramanik K, Ganguly S. Electron transfer catalysis mediated by 3d complexes of redox non-innocent ligands possessing an azo function: a perspective. Dalton Trans 2023; 52:15627-15646. [PMID: 37792473 DOI: 10.1039/d3dt02567e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/06/2023]
Abstract
It was first reported almost two decades ago that ligands with azo functions are capable of accepting electron(s) upon coordination to produce azo-anion radical complexes, thereby exhibiting redox non-innocence. Over the past two decades, there have been numerous reports of such complexes along with their structures and diverse characteristics. The ability of a coordinated azo function to accept one or more electron(s), thereby acting as an electron reservoir, is currently employed to carry out electron transfer catalysis since they can undergo redox transformation at mild potentials due to the presence of energetically accessible energy levels. The cooperative involvement of redox non-innocent ligand(s) containing an azo group and the coordinated metal centre can adjust and modulate the Lewis acidity of the latter through selective ligand-centred redox events, thereby manipulating the capacity of the metal centre to bind to the substrate. We have summarized the list of first row transition metal complexes of iron, cobalt, nickel, copper and zinc with redox non-innocent ligands incorporating an azo function that have been exploited as electron transfer catalysts to effectuate sustainable synthesis of a wide variety of useful chemicals. These include ketazines, pyrimidines, benzothiazole, benzoxazoles, N-acyl hydrazones, quinazoline-4(3)H-ones, C-3 alkylated indoles, N-alkylated anilines and N-alkylated heteroamines. The reaction pathways, as demonstrated by catalytic loops, reveal that the azo function of a coordinated ligand can act as an electron sink in the initial steps to bring about alcohol oxidation and thereafter, they serve as an electron pool to produce the final products either via HAT or PCET processes.
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Affiliation(s)
- Alok Apan Swatiputra
- Department of Chemistry, St. Xavier's College (Autonomous), Kolkata - 700016, India.
| | - Debaarjun Mukherjee
- Department of Chemistry, St. Xavier's College (Autonomous), Kolkata - 700016, India.
| | - Soumitra Dinda
- Department of Chemistry, St. Xavier's College (Autonomous), Kolkata - 700016, India.
| | - Subhadip Roy
- Department of Chemistry, The ICFAI University Tripura, Tripura 799210, India
| | - Kausikisankar Pramanik
- Department of Chemistry, Inorganic Chemistry Section, Jadavpur University, Kolkata - 700032, India
| | - Sanjib Ganguly
- Department of Chemistry, St. Xavier's College (Autonomous), Kolkata - 700016, India.
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Sharma V, Chavan KA, Mali G, Sarkar D, Lama P, Majumder M, Erande RD, Metre RK. A Catecholaldimine-Based Ni II-Complex as an Effective Catalyst for the Direct Conversion of Alcohols to trans-Cinnamonitriles and Aldehydes. J Org Chem 2023. [PMID: 37155715 DOI: 10.1021/acs.joc.2c03067] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
A nickel(II) complex [Ni(HL)2] 1 was synthesized by treatment of a new catecholaldimine-based ligand with NiCl2·6H2O in methanol at room temperature. Complex 1 showed excellent catalytic activity where aromatic and heterocyclic alcohols were rapidly converted into trans-cinnamonitrile in a one-pot manner via oxidative olefination in the presence of KOH. The potential of the disclosed catalyst and the results obtained for the direct conversion of alcohols to two different functionalities (trans-cinnamonitrile and aldehydes) are well supported by DFT studies.
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Affiliation(s)
- Vivek Sharma
- Department of Chemistry, Indian Institute of Technology Jodhpur, Jodhpur 342030, Rajasthan, India
| | - Kailas Arjun Chavan
- Department of Chemistry, Indian Institute of Technology Jodhpur, Jodhpur 342030, Rajasthan, India
| | - Ghanshyam Mali
- Department of Chemistry, Indian Institute of Technology Jodhpur, Jodhpur 342030, Rajasthan, India
| | - Dipanjana Sarkar
- Department of Chemistry, Indian Institute of Technology Jodhpur, Jodhpur 342030, Rajasthan, India
| | - Prem Lama
- CSIR-Indian Institute of Petroleum, Haridwar Road, Mokhampur, Dehradun 248005, India
| | - Moumita Majumder
- Department of Metallurgical and Materials Engineering, Indian Institute of Technology Jodhpur, Jodhpur 342030, India
| | - Rohan D Erande
- Department of Chemistry, Indian Institute of Technology Jodhpur, Jodhpur 342030, Rajasthan, India
| | - Ramesh K Metre
- Department of Chemistry, Indian Institute of Technology Jodhpur, Jodhpur 342030, Rajasthan, India
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Donthireddy SNR, Siddique M, Rit A. N-Heterocyclic Carbene-Supported Nickel-Catalyzed Selective (Un)Symmetrical N-Alkylation of Aromatic Diamines with Alcohols. J Org Chem 2023; 88:1135-1146. [PMID: 36603160 DOI: 10.1021/acs.joc.2c02639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The "borrowing hydrogen" (BH) approach for the N-alkylation of phenylenediamines using alcohols as coupling partners is highly challenging due to the selectivity issue of the generated products. Furthermore, the development of base-metal systems that can potentially substitute precious metals with competitive activity is a major challenge in BH catalysis. We present herein an efficient protocol for the N,N'-di-alkylation of aromatic diamines using an in situ-generated Ni-NHC complex from NiCl2 and the ligand L1, which gave access to a wide range of N,N'-di-alkylated orthophenylene diamines (rather than the generally observed benzimidazole derivatives), meta- and para-phenylene diamines along with 2,6-diamino pyridine derivatives in good to excellent yields. Moreover, the catalyst system was also successful in the derivatization of a clinically important drug molecule, Dapsone. Notably, the present protocol could be applied effectively to synthesize unsymmetrically substituted N,N'-di-alkylated diamines via sequential alkylation and is the first report in the base-metal system to the best of our knowledge. Diverse control experiments including the deuterium incorporation studies suggest that the present protocol proceeds via a BH sequence.
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Affiliation(s)
- S N R Donthireddy
- Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India
| | - Misba Siddique
- Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India
| | - Arnab Rit
- Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India
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Singh K, Kundu A, Adhikari D. Ligand-Based Redox: Catalytic Applications and Mechanistic Aspects. ACS Catal 2022. [DOI: 10.1021/acscatal.2c02655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kirti Singh
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, SAS Nagar, Manauli 140306, India
| | - Abhishek Kundu
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, SAS Nagar, Manauli 140306, India
| | - Debashis Adhikari
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, SAS Nagar, Manauli 140306, India
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