Heterogeneous Fe-N-C Catalyst for Aerobic Dehydrogenation of Hydrazones to Diazo Compounds Used for Carbene Transfer

• Type of Material: Article
• Authors: Melissa N. Hall, University of Wisconsin-Madison; Maizie Lee, Emory University; Thatcher W. Root, University of Wisconsin-Madison; Huw M.L. Davies, Emory University; Shannon S. Stahl, University of Wisconsin-Madison
• Language: English
• Date: 2024-05-08
• Publisher: American Chemical Society
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2024 American Chemical Society
• Final Published Version (URL): https://doi.org/10.1021/jacs.4c04430
• Title of Journal or Parent Work: Journal of the American Chemical Society
• Volume: 46
• Issue: 20
• Start Page: 13741
• End Page: 13747
• Grant/Funding Agency: National Institutes of Health; U.S. Department of Energy, Office of Science, Basic Energy Sciences; National Science Foundation; University of Wisconsin; Paul J. Bender
• Grant/Funding Information: This research was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences (SSS, DE-FG02-05ER15690 – synthesis of M-N-C catalysts), the National Institutes of Health (SSS, R35GM134929 – optimization and application of M-N-C catalysts; HMLD, R01 GM099142), the National Science Foundation (HMLD, CHE-1956154), and partially supported by the National Science Foundation under the CCI Center for Selective C–H Functionalization (SSS, CHE-1700982). Constructive discussions within the Catalysis Innovation Consortium facilitated this study. Spectroscopic instrumentation was supported by a generous gift from Paul J. Bender, the NSF (CHE-1048642), and the NIH (S10OD012245). ICP-OES instrumentation at the Water Sciences Engineering Laboratory was supported by the University of Wisconsin.
• Keywords: Organic diazo compounds; synthetic accessibility; chemical synthesis
• Subject - Topics: Chemistry

Abstract

Organic diazo compounds are versatile reagents in chemical synthesis and would benefit from improved synthetic accessibility, especially for larger scale applications. Here, we report a mild method for the synthesis of diazo compounds from hydrazones using a heterogeneous Fe-N-C catalyst, which has Fe ions dispersed within a graphitic nitrogen-doped carbon support. The reactions proceed readily at room temperature using O2 (1 atm) as the oxidant. Aryl diazoesters, ketones, and amides are accessible, in addition to less stable diaryl diazo compounds. Initial-rate data show that the Fe-N-C catalyst achieves faster rates than a heterogeneous Pt/C catalyst. The oxidative dehydrogenation of hydrazones may be performed in tandem with Rh-catalyzed enantioselective C–H insertion and cyclopropanation of alkenes, without requiring isolation of the diazo intermediate. This sequence is showcased by using a flow reactor for continuous synthesis of diazo compounds.