Recent Progress on Cyclic Nitrenoid Precursors in Transition‐Metal‐Catalyzed Nitrene‐Transfer Reactions

Abstract

Nitrene-transfer reactions have been a powerful synthetic method for direct incorporation of nitrogen atoms into organic molecules. Discovery of novel nitrene-transfer reactions has been dominantly supported by not only the improvement in transition-metal catalysts but also by the employment of novel precursors of nitrenoids. Since the pioneering works utilizing organic azides or iminoiodinanes as practical synthetic tools for nitrogen-containing compounds were reported, a new approach using various N-heterocycles containing strain energy or a weak bond has emerged. In this review, we briefly summarize the history of nitrene-transfer chemistry from the viewpoint of its precursors. In particular, the use of N-heterocycles such as 2H-azirines, 1,4,2-dioxazol-5-ones, 1,2,4-oxadiazol-5-ones, isoxazol-5(4H)-ones, and isoxazoles are comprehensively described, showing the recent remarkable progress in this chemistry.

Organic Azides: Versatile Synthons in Transition Metal‐Catalyzed C(sp2)−H Amination/Annulation for N‐Heterocycle Synthesis

“…Compared with intramolecular process, the intermolecular C( sp 2 )−H amination/annulation are more challenging [10d,f] . In 2013, Ellman and co‐workers achieved an efficient Rh(III)‐catalyzed intermolecular [3+3] annulation of aryl azides with aromatic imines and azobenzenes for the synthesis of a wide range of acridines and phenazines (Scheme 11).…”

Nitrene-Mediated P–N Coupling Under Iron Catalysis

“…Herein, we report a nitrene-mediated P-N coupling reaction of various phosphorus nucleophiles and dioxazolones under simple iron catalysis. [30][31][32][33][34][35][36][37][38] A) Selected…”

Organophotoredox‐Catalyzed Decarboxylative N‐Alkylation of Sulfonamides

“…As with N-arylation chemistry, N-alkylation of sulfonamides has traditionally relied on transition metal catalysis (Figure 1A). For example, transition metal catalyzed intramolecular or intermolecular hydroamination of alkenes, [5] metal nitrenoid-mediated C(sp 3 )-H amination [6] and dehydrative alkylation with alcohols [7] have been reported. Although other approaches have been introduced, such as those using strong acids [8] and electrophilic iodine reagents, [9] the scope of compatible sulfonamides and alkyl groups under these conditions is reasonably limited.…”