2-Bromoanilines, copper-catalyzed

Copper-catalyzed coupling reaction of 2-bromoanilines and pipecoli-nic acid provided 6,6fl,7,8,9,10-hexahydro-5H-pyrido[l,2-a]quinoxalin-6-ones 392 (09BML4119). Using [Pd(r/3-C3H5)Cl2]2 with (2-biphenyl)di-ferf-butylphosphine catalyst system and Cu(I)Br gave lower yields. 

A three-component reaction for the synthesis of functionalized benzimidazoles from terminal alkynes, o-aminoanilines, and / -tolylsulfonyl azide is developed by Wang and coworkers (Scheme 8.52). The C(sp)-H bond of alkyne was activated in this reaction via Cul-catalyzed azide-alkyne cycloaddtion (CuAAC) reaction which could lead to the formation of a ketenimine intermediate by the release of N2- The benzimidazoles could be obtained by intramolecular nucleophilic addition and subsequent elimination of amide intermediate with 2% H2SO4 under reflux conditions [91]. They also developed another protocol for the synthesis of substituted benzimidazole derivatives via a sequential three-component cascade reaction from sulfonyl azides, alkynes, and 2-bromoanilines using Cul as catalyst. Similarly, the C-H bond of alkyne was activated at the process of copper-catalyzed azide-alkyne cycloaddtion (CuAAC) reaction [92]. 

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