Mechanistic insights into copper-catalyzed aerobic oxidative coupling of N–N bonds

Ryan, Michael; Kim, Yeon Jung; Gerken, James B.; Wang, Fei; Aristov, Michael M.; Martinelli, Joseph R.; Stahl, Shannon S.

doi:10.1039/c9sc04305e

Cited by 33 publications

(18 citation statements)

References 41 publications

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“…Additionally, we determined the O2 stoichiometry of the reaction by measuring gas consumption within a sealed reaction vessel equipped with a pressure transducer (Figure S16). 34 These data indicate that just over 2 equivalents of O2 are consumed over the course of the reaction, consistent with O2 acting as only a one-electron oxidant. 35 As anticipated, we found that only minimal oxygen is consumed during the induction period.…”

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confidence: 73%

Unveiling Potent Photooxidation Behavior of Catalytic Photoreductants

Targos¹,

Williams²,

Wickens

2021

Preprint

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We describe a photocatalytic system that reveals latent photooxidant behavior from one of the most reducing conventional photoredox catalysts, N-phenylphenothiazine (PTH). This aerobic photochemical reaction engages difficult to oxidize feedstocks, such as benzene, in C(sp2)–N coupling reactions through direct oxidation. Mechanistic studies are consistent with activation of PTH via photooxidation and that Lewis acid co-catalysts scavenge inhibitors formed upon catalyst activation.

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confidence: 73%

Unveiling Potent Photooxidation Behavior of Catalytic Photoreductants

Targos¹,

Williams²,

Wickens

2021

Preprint

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“…Copper ( ii ) was chosen as the catalytic oxidant of hydrazines because the aerobic oxidation of copper ( i ) complexes to copper ( ii ) ones is generally easy (Figure 1). [26] Besides, copper ( i ) is effective for the oxidative coupling [27] of amines to hydrazines, [28–30] or azo derivatives, [31] as well as that of various N‐functions, where at least one of the nitrogen atoms is sp 2 [32–35] . However, from that perspective hydrazines themselves, particularly the poorly substituted, highly reducing ones are more challenging because of their ability to engage in single electron transfers [36] …”

Section: Resultsmentioning

confidence: 99%

Catalytic Aerobic Oxidation of Hydrazines into 2‐Tetrazenes

2022

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Dedicated to Holger Braunschweig on his 60th birthday, for his continued support and inspiration.We report a catalytic formation of 2-tetrazenes by copper (ii) promoted oxidation of hydrazines in the presence of bipyridine ligands, that uses air or dioxygen as terminal oxidant. The method was applied to a series of hydrazines, delivering symmetrical tetrazenes, which were previously prepared using toxic or stoichiometric oxidants. The catalytic reaction could be used for the formation of a cyclic tetrazene from a bishydrazine, presumably with the help of a chelation of the substrate to the catalytic metal, which favored cyclization over oligomerization. Finally, the method could be used to prepare dissymmetric structures, albeit in the presence of an excess of one of the hydrazines.

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“…In order to better understand this reaction, the same group recently reported new mechanistic insights. 34 In particular, the authors showed that under such reaction conditions, typically first order kinetics are observed for the O 2 gas, while second order kinetics are observed for the copper salt, indicating that the copper catalysed activation of O 2 is a key step in this reaction ( Scheme 18 ). In contrast, the N–H substrate seems to display a negative kinetic order.…”

Section: Dehydrogenative N–n Heterocouplingmentioning

confidence: 99%