Unsymmetrical piperazines are key constituents of many pharmaceuticals. Given that the selective introduction of an aryl and alkyl motif onto the piperazine is not always straightforward, direct arylation and alkenylation of 1,4‐diaza‐bicyclo[2.2.2]octane would obviate the inefficiencies associated with the preparation of these target molecules. We have utilized alkyl halides, aryl or alkenyl triflates, and 1,4‐diaza‐bicyclo[2.2.2]octane for the synthesis of N‐alkyl‐N′‐aryl or alkenylpiperazines. The optimum conditions are developed using CuCl, t‐BuOLi in NMP. Alkenyl triflates requires N,N′‐dimethylethylenediamine and higher temperature to afford the desired cross‐coupled product. Substrates bearing electron‐deficient and electron‐rich groups were successfully coupled under the optimum reaction conditions.
O-Methyl oximes have been employed as nucleophiles in reactions with ketenimines derived from sulfonyl azides and terminal alkynes to form N-alkylidene N′-tosylacetimidamide derivatives. The optimized conditions involved the use of CuPF6 and i-Pr2NEt in MeCN at 65 °C. Both O-methyl aldoximes and ketoximes were tolerated under the optimum conditions.
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