Comparative Nitrene-Transfer Chemistry to Olefins Mediated by First-Row Transition Metal Catalysts Supported by a Pyridinophane Macrocycle with N4 Ligation

Author

Himanshu Bhatia
Lillian P. Adams
Ingrid Cordsiemon
Suraj Kumar Sahoo
Amitava Choudhury, Missouri University of Science and TechnologyFollow
Thomas R. Cundari
Pericles Stavropoulos, Missouri University of Science and TechnologyFollow

Abstract

A 12-membered pyridinophane scaffold containing two pyridine and two tertiary amine residues is examined as a prototype ligand (^tBuN4) for supporting nitrene transfer to olefins. The known [(^tBuN4)M^II(MeCN)2]²⁺ (M = Mn, Fe, Co, and Ni) and [(^tBuN4)Cu^I(MeCN)]⁺ cations are synthesized with the hexafluorophosphate counteranion. The aziridination of para-substituted styrenes with PhI=NTs (Ts = tosyl) in various solvents proved to be high yielding for the Cu(I) and Cu(II) reagents, in contrast to the modest efficacy of all other metals. For α-substituted styrenes, aziridination is accompanied by products of aziridine ring opening, especially in chlorinated solvents. Bulkier β-substituted styrenes reduce product yields, largely for the Cu(II) reagent. Aromatic olefins are more reactive than aliphatic congeners by a significant margin. Mechanistic studies (Hammett plots, KIE, and stereochemical scrambling) suggest that both copper reagents operate via sequential formation of two N–C bonds during the aziridination of styrene, but with differential mechanistic parameters, pointing towards two distinct catalytic manifolds. Computational studies indicate that the putative copper nitrenes derived from Cu(I) and Cu(II) are each associated with closely spaced dual spin states, featuring high spin densities on the nitrene N atom. The computed electrophilicity of the Cu(I)-derived nitrene reflects the faster operation of the Cu(I) manifold.

Recommended Citation

H. Bhatia et al., "Comparative Nitrene-Transfer Chemistry to Olefins Mediated by First-Row Transition Metal Catalysts Supported by a Pyridinophane Macrocycle with N4 Ligation," Molecules, vol. 30, no. 15, article no. 3097, MDPI, Aug 2025.

The definitive version is available at https://doi.org/10.3390/molecules30153097

Department(s)

Chemistry

Publication Status

Open Access

Comments

National Institutes of Health, Grant R15GM117508

Keywords and Phrases

aziridination; copper nitrenes; electrophilicity; nitrene transfer; olefins; pyridine-containing macrocycles

International Standard Serial Number (ISSN)

1420-3049

Document Type

Article - Journal

Document Version

Final Version

File Type

text

Language(s)

English

Rights

© 2025 The Authors, All rights reserved.

Creative Commons Licensing

This work is licensed under a Creative Commons Attribution 4.0 License.

Publication Date

01 Aug 2025

PubMed ID

40807272