A novel synthesis of pyrrolidine-2-carbaldehydes or tetrahydropyridine-2-carbaldehydes from the cascade reactions of N-arylpiperidines or N-arylazepanes is presented. Mechanistically, the formation of the title compounds involves an unprecedented oxidative ring contraction of inactivated cyclic amines via Cu(OAc)₂/KI/O₂-promoted oxidative cleavage and reformation of the C–N bond. Interestingly, when PhI(OAc)₂ was used in place of KI, 1,1-diacetates of the corresponding aldehydes were directly obtained with good efficiency. To the best of our knowledge, this is the first example of regioselective C(sp³)–H bond functionalization and C(sp³)–N bond activation of saturated cyclic amines using copper salt and oxygen.

中文翻译：

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由涉及氧化环收缩的失活环胺合成α-甲酰化的N-杂环及其1,1-二乙酸酯

提出了一种由N-芳基哌啶或N-芳基氮杂环庚烷的级联反应合成吡咯烷-2-甲醛或四氢吡啶-2-甲醛的新方法。从机理上讲，标题化合物的形成涉及通过Cu（OAc）₂ / KI / O ₂促进的氧化裂解和C–N键的重整，使灭活的环状胺发生前所未有的氧化环收缩。有趣的是，当用PhI（OAc）₂代替KI时，可以高效地直接获得相应醛的1,1-二乙酸酯。据我们所知，这是区域选择性C（sp ³）–H键功能化和C（sp ³）–使用铜盐和氧使饱和环胺的N键活化。