Electrochemical Synthesis of Dimeric λ³‑Bromane: Platform for Hypervalent Bromine(III) Compounds

A straightforward and scalable approach to a previously unreported class of cyclic hypervalent Br(III) species capitalizes on the anodic oxidation of aryl bromide to dimeric benzbromoxole that serves as a versatile platform to access a range of structurally diverse Br(III) congeners such as acetoxy-, alkoxy-, and ethynyl-λ3-bromanes as well as diaryl-λ3-bromanes. The synthetic utility of dimeric λ3-bromane is exemplified by photoinduced Minisci-type heteroarylation reactions and benzylic oxidation

<i>Para</i>-Selective Cu-Catalyzed C–H Aryloxylation of Electron-Rich Arenes and Heteroarenes

Cu-catalyzed reaction of phenols with electron-rich arene or heteroarene ligands of unsymmetrical diaryl-λ³-iodanes is a key step in the developed one-pot two-step method for intermolecular <i>para</i>-selective C–H aryloxylation of heteroarenes and arenes

Copper-Catalyzed <i>para</i>-Selective C–H Amination of Electron-Rich Arenes

A one-pot two-step method for <i>para</i>-selective C–H amination of carbocyclic arenes comprises the <i>in situ</i> formation of unsymmetrical diaryl-λ³-iodanes followed by their Cu­(I)-catalyzed reaction with a range of N-unprotected amines

Copper-Catalyzed Intermolecular C–H Amination of (Hetero)arenes via Transient Unsymmetrical λ³‑Iodanes

A one-pot two-step method for intermolecular C–H amination of electron-rich heteroarenes and arenes has been developed. The approach is based on a room-temperature copper-catalyzed regioselective reaction of the in situ formed unsymmetrical (hetero)­aryl-λ³-iodanes with a wide range of primary and secondary aliphatic amines and anilines

Indirect C–H Azidation of Heterocycles via Copper-Catalyzed Regioselective Fragmentation of Unsymmetrical λ³‑Iodanes

A C–H bond of electron-rich heterocycles is transformed into a C–N bond in a reaction sequence comprising the formation of heteroaryl­(phenyl)­iodonium azides and their in situ regioselective fragmentation to heteroaryl azides. A Cu­(I) catalyst ensures complete regiocontrol in the fragmentation step and catalyzes the subsequent 1,3-dipolar cycloaddition of the formed azido heterocycles with acetylenes. The heteroaryl azides can also be conveniently reduced to heteroarylamines by aqueous ammonium sulfide. The overall C–H to C–N transformation is a mild and operationally simple one-pot sequential multistep process

Copper-Catalyzed Intermolecular C–H Amination of (Hetero)arenes via Transient Unsymmetrical λ³‑Iodanes

A one-pot two-step method for intermolecular C–H amination of electron-rich heteroarenes and arenes has been developed. The approach is based on a room-temperature copper-catalyzed regioselective reaction of the in situ formed unsymmetrical (hetero)­aryl-λ³-iodanes with a wide range of primary and secondary aliphatic amines and anilines

Copper-Catalyzed <i>para</i>-Selective C–H Amination of Electron-Rich Arenes

A one-pot two-step method for <i>para</i>-selective C–H amination of carbocyclic arenes comprises the <i>in situ</i> formation of unsymmetrical diaryl-λ³-iodanes followed by their Cu­(I)-catalyzed reaction with a range of N-unprotected amines

Diastereoselective Hydroxymethylation of Cyclic <i>N</i>-<i>tert</i>-Butanesulfinylketimines Using Methoxymethanol as Formaldehyde Source

Hydroxymethylation of cyclic <i>tert</i>-butanesulfinylketimine-derived lithium enamides with methoxymethanol proceeds with excellent diastereoselectivity (99:1 dr). Methoxymethanol is a stable and easy-to-handle source of anhydrous monomeric formaldehyde in the reaction with lithium enamides. Cyclic α-hydroxymethyl ketimines undergo highly diastereoselective reduction to <i>syn</i>- or <i>anti</i>-1,3-amino alcohols

Diastereoselective Hydroxymethylation of Cyclic <i>N</i>-<i>tert</i>-Butanesulfinylketimines Using Methoxymethanol as Formaldehyde Source

Hydroxymethylation of cyclic <i>tert</i>-butanesulfinylketimine-derived lithium enamides with methoxymethanol proceeds with excellent diastereoselectivity (99:1 dr). Methoxymethanol is a stable and easy-to-handle source of anhydrous monomeric formaldehyde in the reaction with lithium enamides. Cyclic α-hydroxymethyl ketimines undergo highly diastereoselective reduction to <i>syn</i>- or <i>anti</i>-1,3-amino alcohols

Synthesis of Benzoxazoles Using Electrochemically Generated Hypervalent Iodine

The indirect (“ex-cell”) electrochemical synthesis of benzoxazoles from imines using a redox mediator based on the iodine­(I)/iodine­(III) redox couple is reported. Tethering the redox-active iodophenyl subunit to a tetra-alkylammonium moiety allowed for anodic oxidation to be performed without supporting electrolyte. The mediator salt can be easily recovered and reused. Our “ex-cell” approach toward the electrosynthesis of benzoxazoles is compatible with a range of redox-sensitive functional groups. An unprecedented concerted reductive elimination mechanism for benzoxazole formation is proposed on the basis of control experiments and DFT calculations