Iron-Catalyzed Intermolecular C-H Amination Assisted by an Isolated Iron-Imido Radical Intermediate

Here we report the use of a base metal complex [(tBupyrpyrr2)Fe(OEt2)] (1-OEt2) (tBupyrpyrr22-=3,5-tBu2-bis(pyrrolyl)pyridine) as a catalyst for intermolecular amination of Csp3-H bonds of 9,10-dihydroanthracene (2 a) using 2,4,6-trimethyl phenyl azide (3 a) as the nitrene source. The reaction is complete within one hour at 80 degrees C using as low as 2 mol % 1-OEt2 with control in selectivity for single C-H amination versus double C-H amination. Catalytic C-H amination reactions can be extended to other substrates such as cyclohexadiene and xanthene derivatives and can tolerate a variety of aryl azides having methyl groups in both ortho positions. Under stoichiometric conditions the imido radical species [(tBupyrpyrr2)Fe{=N(2,6-Me2-4-tBu-C6H2)] (1-imido) can be isolated in 56 % yield, and spectroscopic, magnetometric, and computational studies confirmed it to be an S = 1 FeIV complex. Complex 1-imido reacts with 2 a to produce the ferrous aniline adduct [(tBupyrpyrr2)Fe{NH(2,6-Me2-4-tBu-C6H2)(C14H11)}] (1-aniline) in 45 % yield. Lastly, it was found that complexes 1-imido and 1-aniline are both competent intermediates in catalytic intermolecular C-H amination. @Penn, @MindiolaGroup, @MunzDominik, @uniFAUimage

Automated summary

In this study, a base metal complex was used as a catalyst for the intermolecular amination reaction of Csp3-H bonds. The reaction exhibited high selectivity and good substrate tolerance.