Ligand-Free Iron-Catalyzed Intramolecular Amination of C(sp³)—H Bond for the Synthesis of Imidazolinones

Abstract

Transition-metal-nitrenoids intramolecular C-H insertion is one of the most effective methods to synthesize nitrogen-containing heterocycles. Using 2-azido-N,N-dibenzylacetamides as substrates, an iron-catalyzed intramolecular C(sp 3 )-H bond amination reaction under ligand-free and external oxidant-free conditions has been developed. A series of imidazolinones were synthesized in moderate to good yields.

Discovery of a simple iron catalyst reveals the intimate steps of C–H amination to form C–N bonds

“…21 In pioneering work, Betley et al described the use of an iron dipyrrin complex for the intramolecular C-H amination with organic azides to form 5-membered N-heterocycles, 22 a class of compounds relevant to the pharmaceutical industry. 23,24 Based on this breakthrough, several other catalysts were developed by using sophisticated ligand design and involving iron, [25][26][27][28][29][30][31][32][33][34] cobalt, [35][36][37][38][39] nickel, 40,41 ruthenium 42,43 and palladium. 44,45 Currently, iron is the most attractive metal for this transformation with high turnover numbers (TONs) up to 7600, 31 and with additional benets such as low costs, low toxicity and high Earth-abundance.…”