An iron(<scp>ii</scp>)-based metalloradical system for intramolecular amination of C(sp<sup>2</sup>)–H and C(sp<sup>3</sup>)–H bonds: synthetic applications and mechanistic studies

Das, Sandip Kumar; Das, Subrata; Ghosh, Supratim; Roy, Satyajit; Pareek, Monika; Roy, B.; Sunoj, Raghavan B.; Chattopadhyay, Buddhadeb

doi:10.1039/d2sc03505g

Cited by 30 publications

(18 citation statements)

References 57 publications

(99 reference statements)

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“…Fe–porphyrin–nitrene species are known to possess a triplet ground state, ,,,,− which was also verified with the current complexes derived from 1 – 6 at the DFT-B3LYP level of theory (Table S1). In the following discussion, we will initially present the electronic structure investigation of the Fe–porphyrin–nitrene species 1-Sul and 2-Sul followed by a generalization for all of the complexes, 1-Sul to 6-Sul .…”

Section: Results and Discussionsupporting

confidence: 68%

How Axial Coordination Regulates the Electronic Structure and C–H Amination Reactivity of Fe–Porphyrin–Nitrene?

Mahajan,

Mondal

2023

JACS Au

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Detailed electronic structure and its correlation with the intramolecular C–H amination reactivity of Fe–porphyrin–nitrene intermediates bearing different “axial” coordination have been investigated using multiconfigurational complete active space self-consistent field (CASSCF), N-electron valence perturbation theory (NEVPT2), and hybrid density functional theory (DFT-B3LYP) calculations. Three types of “axial” coordination, −OMe/–O(H)Me ( 1-Sul / 2-Sul ), −SMe/–S(H)Me ( 3-Sul/4-Sul ), and −NMeIm (MeIm = 3-methyl-imidazole) ( 5-Sul ) mimicking serine, cysteine, and histidine, respectively, along with no axial coordination ( 6-Sul ) have been considered to decipher how the “axial” coordination of different strengths regulates the electronic integrity of the Fe–N core and nitrene-transfer reactivity of Fe–porphyrin–nitrene intermediates. CASSCF-based natural orbitals reveal two distinct classes of electronic structures: Fe-nitrenes ( 1-Sul and 3-Sul ) with relatively stronger axial coordination (−OMe and −SMe) display “imidyl” nature and those ( 2-Sul, 4-Sul, and 6-Sul ) with weaker axial coordination (−O(H)Me, −S(H)Me and no axial coordination) exhibit “imido-like” character. A borderline between the two classes is also observed with NMeIm axial coordination ( 5-Sul ). Axial coordination of different strengths not only regulates the electronic structure but also modulates the Fe-3d orbital energies, as revealed through the d – d transition energies obtained by CASSCF/NEVPT2 calculations. The relatively lower energy of Fe-3 d z 2 orbital allows easy access to low-lying high-spin quintet states in the cases of weaker “axial” coordination ( 2-Sul, 4-Sul, and 6-Sul ), and the associated hydrogen atom transfer (HAT) reactivity appears to involve two-state triplet-quintet reactivity through minimum energy crossing point ( 3,5 MECP) between the spin states. In stark contrast, Fe-nitrenes with relatively stronger “axial” coordination ( 1-Sul and 3-Sul ) undergo triplet-only HAT reactivity. Overall, this in-depth electronic structure investigation and HAT reactivity evaluation reveal that the weaker axial coordination in Fe–porphyrin–nitrene complexes ( 2-Sul, 4-Sul, and 6-Sul ) can promote more efficient C–H oxidation through the quintet spin state.

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Section: Results and Discussionsupporting

confidence: 68%

How Axial Coordination Regulates the Electronic Structure and C–H Amination Reactivity of Fe–Porphyrin–Nitrene?

Mahajan,

Mondal

2023

JACS Au

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“…Notably, in recent years, Pro fessor Chattopadhyay's group demonstrated that tetrazole can be employed as an effective nitrene precursor 10 for the intra molecular C(sp 2 )-H amination via iridiumcatalyzed electro cyclization, 11 ironcatalyzed C(sp 3 )-H amination and C(sp 2 )-H amination via a radical mechanism (Scheme 1, D). 12,13 Pro fessor Chattopadhyay remarked: "After that, we were keen to develop a method for intermolecular amination reaction using tetrazole as nitrene precursor to access 2pyridylsub stituted benzylamine. In order to establish suitable reaction…”

Section: Literature Coverage Synformmentioning

confidence: 99%

Synform Issue 2023/04

Zanda¹

2023

Synfacts

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“…In 2018, Chattopadhyay et al reported the Ir-catalyzed intramolecular transannulation/C(sp 2 )−H amination of 1,2,3,4-tetrazoles. 11 In this process, the denitrogenation of 1,2,3,4-tetrazole occurs at 130 °C by the combination of [Cp*IrCl 2 ] 2 and AgSbF 6 . Thereafter, Mn-porphyrin and Feporphyrin were successively developed by Chattopadhyay for nitrene transfer reactions with 1,2,3,4-tetrazoles (Scheme 1b).…”

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confidence: 99%

Visible-Light-Driven Iron-Catalyzed Intermolecular Benzylic C(sp³)–H Amination with 1,2,3,4-Tetrazoles

Du,

Tang,

Wang

et al. 2024

Org. Lett.

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A visible-light-driven iron-catalyzed C(sp 3 )−H amination of diphenylmethane derivatives with 1,2,3,4-tetrazoles under mild conditions has been developed. The reaction proceeds with photosensitizer-free conditions and features satisfactory to good yields. Mechanistic studies revealed that the reaction proceeded via an iron−nitrene intermediate, and H atom abstraction was the rate-determining step. Computational studies showed that the denitrogenation of 1,2,3,4-tetrazole depends on the conversion of the sextet ground state of 1,2,3,4-tetrazolebounding iron species to the quartet spin state under visible-light irradiation.

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An iron(ii)-based metalloradical system for intramolecular amination of C(sp²)–H and C(sp³)–H bonds: synthetic applications and mechanistic studies

Abstract: A catalytic system for intramolecular C(sp2)–H and C(sp3)–H amination of substituted tetrazolopyridines has been successfully developed. The amination reactions are developed using an iron-porphyrin based catalytic system. It has been...

Cited by 30 publications

References 57 publications

How Axial Coordination Regulates the Electronic Structure and C–H Amination Reactivity of Fe–Porphyrin–Nitrene?

How Axial Coordination Regulates the Electronic Structure and C–H Amination Reactivity of Fe–Porphyrin–Nitrene?

Synform Issue 2023/04

Visible-Light-Driven Iron-Catalyzed Intermolecular Benzylic C(sp³)–H Amination with 1,2,3,4-Tetrazoles

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An iron(ii)-based metalloradical system for intramolecular amination of C(sp2)–H and C(sp3)–H bonds: synthetic applications and mechanistic studies

Abstract: A catalytic system for intramolecular C(sp2)–H and C(sp3)–H amination of substituted tetrazolopyridines has been successfully developed. The amination reactions are developed using an iron-porphyrin based catalytic system. It has been...

Cited by 30 publications

References 57 publications

How Axial Coordination Regulates the Electronic Structure and C–H Amination Reactivity of Fe–Porphyrin–Nitrene?

How Axial Coordination Regulates the Electronic Structure and C–H Amination Reactivity of Fe–Porphyrin–Nitrene?

Synform Issue 2023/04

Visible-Light-Driven Iron-Catalyzed Intermolecular Benzylic C(sp3)–H Amination with 1,2,3,4-Tetrazoles

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An iron(ii)-based metalloradical system for intramolecular amination of C(sp²)–H and C(sp³)–H bonds: synthetic applications and mechanistic studies

Visible-Light-Driven Iron-Catalyzed Intermolecular Benzylic C(sp³)–H Amination with 1,2,3,4-Tetrazoles