Facile Cu(I)-Catalyzed Oxidative Coupling of Anilines to Azo Compounds and Hydrazines with Diaziridinone under Mild Conditions

Abstract

A mild and highly efficient Cu(I)-catalyzed oxidative coupling of anilines is described. Various primary and secondary anilines can be efficiently coupled under mild conditions to the corresponding azo compounds and hydrazines in high yields. This method provides a direct and practical access to these compounds, and is also amenable to gram scale with no special precautions to exclude air or moisture.

Synthesis of mono-functionalized S-diazocines via intramolecular Baeyer–Mills reactions

“…Unfortunately, the benzylic position of the bridge is deprotonated under these conditions, leading to a plethora of side products. Formation of the N=N double bond by oxidation of diamines [ 21 – 23 ] cannot be applied either, because the sulfur bridge is oxidized to the sulfoxide or sulfone. Hence, neither reductive nor oxidative conditions are compatible with the –CH 2 -S– bridge.…”

A facile copper(i)-catalyzed homocoupling of terminal alkynes to 1,3-diynes with diaziridinone under mild conditions

“…Recently, we have shown that di- tert -butyldiaziridinone ( 1 ) can also be used for the oxidation of alcohols 22 and oxidative coupling of anilines 23 using Cu(I) as catalyst. During our studies on the oxidation of alcohols, 1,6-diphenylhexa-2,4-diyne-1,6-dione ( 4a ) instead of 1-phenylpropynone ( 3a ) was obtained in 31% yield under the reaction conditions when propargyl alcohol 2 was used as substrate (Scheme 1).…”

Continuous-flow methodologies for copper-catalyzed reactions

“…In recent years, the copper-catalyzed oxidative dimerization of aniline derivatives brought new opportunities for the synthesis of azobenzenes. [71][72][73][74][75] Typically, copper(I) halides were used as catalytic copper source in the presence of different bases, ligands, and oxidants. As base, pyridine proved to be the most efficient, and the oxidative conditions were achieved by the application of oxidizing agents, oxygen or air atmosphere.…”

“…To avoid precipitation and blockage in the reactor channels, the applied concentration of the starting material proved to be 0.5 M. According to literature data, due to the typical temperature range 60-100 °C, the reaction media are mainly nonvolatile solvents, such as toluene [69,72,75] and MeCN. [69,[71][72][73][74][75] As a consequence of the restrictive batch technology, the application of low-boiling solvents is still unexplored in this transformation. Thus we versions were registered with the value of 12% and 4% respectively ( Table 5 entries 1 and 2).…”

“…The syntheses of multisubstituted aromatic azo compounds are quite rare in the literature, possibly because of the exceptional steric hindrance generated by the functional groups. [63,64,73] We were delighted to find that di-and trisubstituted aniline derivatives showed excellent reactivities. Even di-ortho-substituted anilines were converted quantitatively to the desired adducts (entries 12 and 13), and all corresponding multisubstituted derivatives were achieved in excellent yields of 89-93% (entries [11][12][13][14].…”