C-Cyclopropylnitrones derived from spiro[2.4]hepta-4,6-diene-1-carbaldehyde and its benzo analog undergo an unprecedented tandem cyclization-retro-Diels–Alder reaction of the 5,6-dihydro-1,2-oxazine intermediates to give the corresponding cyclopentadienones. Computational work indicates that the cyclization step is concerted but highly asynchronous.

中文翻译：

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环戊二烯酮通过串联C-环丙基亚硝基环化-环还原序列

螺[2.4]庚-4,6-二烯-1-甲醛及其苯并类似物衍生的C-环丙基硝酮经历了5,6-二氢-1,2-恶嗪中间体的空前串联环化-复古-狄尔斯-阿尔德反应给出相应的环戊二烯酮。计算工作表明环化步骤是协调的，但高度异步。