Comparative Nitrene-Transfer Chemistry to Olefinic Substrates Mediated by a Library of Anionic Mn(II) Triphenylamido-Amine Reagents and M(II) Congeners (M = Fe, Co, Ni) Favoring Aromatic Over Aliphatic Alkenes

Author

Vivek Bagchi
Anshika Kalra
Purak Das
Patrina Paraskevopoulou
Saidulu Gorla
Lin Ai
Qiuwen Wang
Sudip Mohapatra
Amitava Choudhury, Missouri University of Science and TechnologyFollow
Zhicheng Sun
Thomas R. Cundari
Pericles Stavropoulos, Missouri University of Science and TechnologyFollow

Abstract

Selective amination of σ and π entities such as C-H and C=C bonds of substrates remains a challenging endeavor for current catalytic methodologies devoted to the synthesis of abundant nitrogen-containing chemicals. The present work addresses an approach toward discriminating aromatic over aliphatic alkenes in aziridination reactions, relying on the use of anionic metal reagents (M = Mn, Fe, Co, Ni) to attenuate reactivity in a metal-dependent manner. A family of Mn^II reagents bearing a triphenylamido-amine scaffold and various pendant arms has been synthesized and characterized by various techniques, including cyclic voltammetry. Aziridination of styrene by PhI=NTs in the presence of each Mn^II catalyst establishes a trend of increasing yield with increasing Mn^II/III anodic potential. The Fe^II, Co^II, and Ni^II congeners of the highest-yielding Mn^II catalyst have been synthesized and explored in the aziridination of aromatic and aliphatic alkenes, exhibiting good to high yields with para-substituted styrenes, low to modest yields with sterically congested styrenes, and invariably low yields with aliphatic olefins. Co^II mediates faster styrene aziridination in comparison to Mn^II but is less selective than Mn^II in competitive aziridinations of conjugated versus nonconjugated olefins. Indeed, Mn^II proved to be highly selective even versus well-established copper and rhodium aziridination reagents. Mechanistic investigations and computational studies indicate that all metals follow a two-step styrene aziridination pathway (successive formation of two N-C bonds), featuring a turnover-limiting metal-nitrene addition to an olefinic carbon, followed by product-determining ring closure. Both steps exhibit activation barriers in the order Fe > Mn > Co, most likely stemming from relevant metal-nitrene electrophilicities and MII/III redox potentials. The aziridination of aliphatic olefins follows the same stepwise path, albeit with a considerably higher activation barrier and a weaker driving force for the formation of the initial N-C bond, succeeded by ring closure with a miniscule barrier.

Recommended Citation

V. Bagchi and A. Kalra and P. Das and P. Paraskevopoulou and S. Gorla and L. Ai and Q. Wang and S. Mohapatra and A. Choudhury and Z. Sun and T. R. Cundari and P. Stavropoulos, "Comparative Nitrene-Transfer Chemistry to Olefinic Substrates Mediated by a Library of Anionic Mn(II) Triphenylamido-Amine Reagents and M(II) Congeners (M = Fe, Co, Ni) Favoring Aromatic Over Aliphatic Alkenes," ACS Catalysis, vol. 8, no. 10, pp. 9183 - 9206, American Chemical Society (ACS), Oct 2018.

The definitive version is available at https://doi.org/10.1021/acscatal.8b01941

Department(s)

Chemistry

Keywords and Phrases

Cobalt; Computational Studies; Electrochemistry; Iron; Manganese; Mechanistic Studies; Nitrene-Transfer Catalysis; Trisamido-Amine Ligands

International Standard Serial Number (ISSN)

2155-5435

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2018 American Chemical Society (ACS), All rights reserved.

Publication Date

01 Oct 2018