Copper‐catalyzed [4+2] cycloaddition of N‐(2‐pyridyl)ketimines and terminal alkynes has been achieved. Ketimines bearing a trifluoromethyl group reacted with various terminal alkynes to produce pyrido[1,2‐a]pyrimidines in good to high yields. This reaction proceeded through a propargylamine intermediate and the corresponding product was obtained via 6‐endo‐dig cyclization.

中文翻译：

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使用N-（2-吡啶基）酮亚胺和末端炔烃的铜催化[4 + 2]环加成反应

N-（2-吡啶基）酮亚胺和末端炔的铜催化[4 + 2]环加成反应已实现。带有三氟甲基的ketimines与各种末端炔烃反应生成吡啶[1,2- a ]嘧啶，产率高至高。该反应通过炔丙基胺中间体进行，并且通过6-endo-dig环化获得了相应的产物。