Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012, Bern, Switzerland.
Department of Chemistry, LMU München, Butenandtstrasse 5-13, 81377, München, Germany.
Nat Commun. 2018 Nov 20;9(1):4888. doi: 10.1038/s41467-018-07196-9.
Radical fluorination has been known for a long time, but synthetic applications were severely limited by the hazardous nature of the first generation of reagents such as F and the strongly electrophilic nature of the second generation of reagents such as N-fluorobenzenesulfonimide (NFSI) and Selecfluor. Here, we report the preparation, use and properties of N-fluoro-N-arylsulfonamides (NFASs), a class of fluorinating reagents suitable for radical fluorination under mild conditions. Their N-F bond dissociation energies (BDE) are 30-45 kJ mol lower than the N-F BDE of the reagents of the second generation. This favors clean radical fluorination processes over undesired side reactions. The utility of NFASs is demonstrated by a metal-free radical hydrofluorination of alkenes including an efficient remote C-H fluorination via a 1,5-hydrogen atom transfer. NFASs have the potential to become the reagents of choice in many radical fluorination processes.
自由基氟化早已为人所知，但第一代试剂（如 F）的危害性以及第二代试剂（如 N-氟代苯磺酰胺（NFSI）和Selecfluor）的强亲电性，严重限制了其在合成中的应用。在这里，我们报告了 N-氟代-N-芳磺酰胺（NFAS）的制备、使用和性质，这是一类适合在温和条件下进行自由基氟化的氟化试剂。它们的 N-F 键离解能（BDE）比第二代试剂的 N-F BDE 低 30-45kJ/mol。这有利于清洁的自由基氟化过程，而不是不希望的副反应。NFAS 的实用性通过烯烃的无金属自由基氢氟化反应得到证明，包括通过 1,5-氢原子转移的有效远程 C-H 氟化。NFAS 有可能成为许多自由基氟化过程中首选的试剂。
