We present here a combined experimental and computational investigation into the photorearrangement of N-cyclopropylimines to yield pyrrolines. We show that the photochemistry, regiochemistry, and stereochemistry of the reaction can be understood in terms of a mechanism involving barrierless evolution in three different (S(2), S(1), S(0)) singlet states and sequential decay through two different (S(2)/S(1), and S(1)/S(0)) conical intersection funnels. We provide evidence that the reaction mechanism involves the generation of a nonequilibrated (i.e., transient) excited state diradical, whose decay can lead not only to pyrrolines but also to cyclopropylimine isomers. It is concluded that the reaction outcome depends on the details of the structure of such transient diradical and on the nature of the dynamics of its decay through the S(1)/S(0) conical intersection.

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N-环丙亚胺-1-吡咯啉光重排的机理

我们在这里介绍了对 N-环丙基亚胺的光重排产生吡咯啉的联合实验和计算研究。我们表明，该反应的光化学、区域化学和立体化学可以通过涉及三种不同（S（2）、S（1）、S（0））单线态的无障碍演化和通过两个连续衰变的机制来理解。不同的 (S(2)/S(1) 和 S(1)/S(0)) 锥形交叉漏斗。我们提供的证据表明，反应机制涉及非平衡（即瞬态）激发态双自由基的产生，其衰变不仅会导致吡咯啉，还会导致环丙亚胺异构体。