Naslov
Radical Stability as a Guideline in C–H Amination Reactions

Autori
Šakić, Davor ; Zipse, Hendrik

Izvornik
Advanced synthesis & catalysis (1615-4150) 358 (2016), 24; 3983-3991

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
amination ; C–H activation ; radical stability ; remote functionalization

Sažetak
The stability of N-centered radicals and radical cations of potential relevance in C–H amidation reactions has been quantified using highly accurate theoretical methods. Combination with available C–H bond energies for substrate fragments allows for the prediction of reaction enthalpies in 1, 5-hydrogen atom transfer (HAT) steps frequently encountered in reactions such as the Hoffman–Löffler–Freytag (HLF) reaction. Protonation of N- radicals is found to be essential in classical HLF reactions for thermochemically feasible HAT steps. The stability of neutral N- radicals depends strongly on the type of N-substituent. Among the electron-withdrawing substituents, the trifluoroacetyl (TFA) group is the least and the toluenesulfonyl (tosyl) group the most stabilizing. This implies that TFA-aminyl radicals have the broadest and tosyl-aminyl radicals the smallest window of synthetic applicability. In how far the intramolecular C–H amidation reactions compete with hydrogen abstraction from common organic solvents can be judged based on a comparison of reaction thermodynamics.

Izvorni jezik
Engleski

Znanstvena područja
Kemija, Farmacija

POVEZANOST RADA