Visible‐Light‐Accelerated Copper(II)‐Catalyzed Regio‐ and Chemoselective Oxo‐Azidation of Vinyl Arenes

Abstract

The visible-light-accelerated oxo-azidation of vinyl arenes with trimethylsilylazide and molecular oxygen as stoichiometric oxidant was achieved. In contrast to photocatalysts based on iridium, ruthenium, or organic dyes, [Cu(dap) ]Cl or [Cu(dap)Cl ] were found to be unique for this transformation, which is attributed to their ability to interact with the substrates through ligand exchange and rebound mechanisms. Cu is proposed as the catalytically active species, which upon coordinating azide will undergo light-accelerated homolysis to form Cu and azide radicals. This activation principle (Cu -X→Cu +X ) opens up new avenues for copper-based photocatalysis.

Hypervalent Iodine(III)‐Promoted Rapid Cascade Reaction of Quinoxalinones with Unactivated Alkenes and TMSN3

“…Other oxidants, such as PhI(OAc) 2 , K 2 S 2 O 8 and TBHP did not enhance the product yield ( Table 1, entries [2][3][4][5]. Subsequently, some organic solvents including dichloromethane (DCM), dichloroethane (DCE), toluene, tetrahydrofuran (THF), dimethyl formamide (DMF) and dimethylsulfoxide (DMSO) were explored (Table 1, entries 1,[6][7][8][9][10][11], and found that dichloromethane (DCM) was the optimal solvent for this transformation. After obtained the optimal oxidant and solvent, we tried to reduce the amounts of substrates 2 a and 3.…”

A Retrosynthetic Approach for Photocatalysis

“…Moreover, Leonori and co‐workers developed a method for the azidation of α‐amino acids giving α‐amino azides after decarboxylative azidation catalyzed by Rhodamine 6G . Another alternative procedure was developed by Reiser and co‐workers who reported a copper‐catalyzed oxo‐azidation of vinyl arenes to give α‐azido‐ketones . A similar procedure was developed by Lu and co‐workers yielding α‐azido alcohols instead of ketones …”

Catalytic Azido‐Hydrazination of Alkenes Enabled by Visible Light: Mechanistic Studies and Synthetic Applications

“…[17] When this catalytic system was applied with an alkene and BocN=NBoc, an oxy-hydrazination product was obtained, [18] revealing the feasibility of an orderly radical addition cascade among a nucleophile, an unactivated alkene and an electrophilic azodicarboxylate with a simple catalyst. [22] Azide anion and its equivalents are well-known to be converted to azide radicals by multiple types of oxidants like redox-active transition metals, [23] hyper-valent iodines, [24] peroxide, [25] electrochemical mediators, [26] and photosensitizers. Azide anion was thereby chosen as the "nucleophile" to continue our exploration because the anticipated azido-hydrazination products could be excellent precursors to vicinal amino hydrazines, azido-amines and diamine derivatives.…”

“…[19] Also, azide is a versatile functional group that serves an excellent linker, [20] a reliable nitrene precursor [21] and many other roles. [22] Azide anion and its equivalents are well-known to be converted to azide radicals by multiple types of oxidants like redox-active transition metals, [23] hyper-valent iodines, [24] peroxide, [25] electrochemical mediators, [26] and photosensitizers. [27,28]…”