Remote Radical Azidation of Unactivated C(sp3)-H Bonds in Sulfamoyl Azides

An efficient method for remote radical C(sp3)-H azidation at unactivated sites is described. C-H functionalization proceeds via intramolecular 1,5-hydrogen atom transfer to N-centered radicals that are generated via azido group transfer and/or fragmentation. The readily installed sulfamoyl azide serves as both an amidyl radical precursor and an azido source. This reaction features excellent site selectivity for tertiary, secondary, primary, and benzylic C(sp3)-H bonds and exhibits broad functional group compatibility.

Fluoroamide-Directed Regiodivergent C-Alkylation of Nitroalkanes

Herein, by exploiting different activation modes of fluoroamides, we achieved α- and δ-C(sp³)-H alkylation of nitroalkanes with switchable regioselectivity. Cu catalysis enabled the interception of a distal C-centered radical by a N-centered radical to couple nitroalkanes and unactivated δ-C-H bonds. In addition, imines generated in situ by fluoroamides were trapped by nitroalkanes to realize the α-C-H alkylation of amides. Both of those scalable protocols have broad substrate scopes and good functional group tolerance.

Copper-Catalyzed, N-Directed Distal C(sp3)-H Functionalization toward Azepanes

We herein report a copper-catalyzed formal [5 + 2] aza-annulation of N-fluorosulfonamides and 1,3-dienes/1,3-enynes for synthesis of structurally diverse alkene/alkyne-containing azepanes. The reaction features selective functionalization of distal unactivated C(sp³)-H bonds and a broad substrate scope, thus allowing the late-stage modification of pharmaceuticals and natural products. A radical mechanism involving 1,5-hydrogen atom transfer of N-radicals, facile coupling of alkyl radicals with 1,3-dienes/1,3-enynes, and the construction of azepane motifs via C-N bond formation is proposed.

Directed evolution of nonheme iron enzymes to access abiological radical-relay C(sp3)-H azidation

We report the reprogramming of nonheme iron enzymes to catalyze an abiological C(sp³)‒H azidation reaction through iron-catalyzed radical relay. This biocatalytic transformation uses amidyl radicals as hydrogen atom abstractors and Fe(III)‒N₃ intermediates as radical trapping agents. We established a high-throughput screening platform based on click chemistry for rapid evolution of the catalytic performance of identified enzymes. The final optimized variants deliver a range of azidation products with up to 10,600 total turnovers and 93% enantiomeric excess. Given the prevalence of radical relay reactions in organic synthesis and the diversity of nonheme iron enzymes, we envision that this discovery will stimulate future development of metalloenzyme catalysts for synthetically useful transformations unexplored by natural evolution.

Iron-Catalyzed, Site-Selective Difluoromethylthiolation (-SCF2H) and Difluoromethylselenation (-SeCF2H) of Unactivated C(sp3)-H Bonds in N-Fluoroamides

The iron-catalyzed δ-C(sp³)-H bond difluoromethylthiolation and difluoromethylselenation of aliphatic amides with high site selectivity are reported. Essential to the success is the employment of an amide radical formed in situ to activate the inert C(sp³)-H bond and the utilization of the easily handled PhSO₂SCF₂H and PhSO₂SeCF₂H as coupling reagents under mild conditions. This scalable protocol exhibits a broad substrate scope bearing versatile functional groups. Mechanistic studies indicate that the reaction proceeds through -SCF₂H and -SeCF₂H radical transfer.

Transition-Metal-Free α Csp3 -H Cyanation of Sulfonamides

This report describes the site-selective α-functionalization of sulfonylamide derivatives through the in-situ generation of imine intermediates. The N-F sulfonylamides, which could facilitate the elimination to generate imines, are coupled with TBACN to efficiently and mildly afford α-amino cyanides. Comparing with Strecker reaction, this transformation offers a complementary strategy to efficiently construct α-amino cyanides from direct α C-H functionalization of sulfonylamindes. The reaction is also characterized by broad substrate scope and flash chromatography column free workup. More importantly, the new two-electron pathway to generate imines through manipulation of the leaving group allows us to achieve excellent α site-selectivity.

Copper-catalyzed, N-directed remote C(sp3)–H azidation and thiocyanation

A mild and practical protocol is developed for the synthesis of distal azido and thiocyanato alkylamines via N-directed remote C(sp³)–H functionalization.

Manganese-Catalyzed N-F Bond Activation for Hydroamination and Carboamination of Alkenes

A visible-light-promoted method for generating amidyl radicals from N-fluorosulfonamides via a manganese-catalyzed N-F bond activation strategy is reported. This protocol employs a simple manganese complex, Mn₂(CO)₁₀, as the precatalyst and a cheap silane, (MeO)₃SiH, as both the hydrogen-atom donor and the F-atom acceptor, enabling intramolecular/intermolecular hydroaminations of alkenes, two-component carboamination of alkenes, and even three-component carboamination of alkenes. A wide range of valuable aliphatic sulfonamides can be readily prepared using these practical reactions.

Transition Metal Catalyzed Azidation Reactions

A wide range of methodologies for the preparation of organic azides has been reported in the literature for many decades, due to their interest as building blocks for different transformations and their applications in biology as well as in materials science. More recently, with the spread of the use of transition metal-catalyzed reactions, new perspectives have also materialized in azidation processes, especially concerning the azidation of C–H bonds and direct difunctionalization of multiple carbon-carbon bonds. In this review, special emphasis will be placed on reactions involving substrates bearing a leaving group, hydroazidation reactions and azidation reactions that proceed with the formation of more than one bond. Further reactions for the preparation of allyl and vinyl azides as well as for azidations involving the opening of a ring complete the classification of the material.