An unprecedented visible-light-mediated intramolecular crossed and straight [2 + 2] cycloaddition has been developed. Irradiation of bis(cinnamoyl)ketenedithioacetals, with visible light as the sole requirement, resulted in the formation of two kinds of complex molecular architecture: bridged bicyclo[3.1.1]heptane-2,4-diones and fused bicyclo[3.2.0]heptane-2,4-diones. Further mechanistic investigations proved that bis(cinnamoyl)ketenedithioacetals could be directly excited by visible light, and DFT calculations were used to explore the unconventional crossed [2 + 2] cycloaddition process.

中文翻译：

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可见光驱动、无催化剂分子内交叉和直链[2 + 2]环加成

一种前所未有的可见光介导的分子内交叉和直[2 + 2]环加成反应已经被开发出来。以可见光为唯一要求的双(肉桂酰基)烯酮二硫缩醛的辐照导致形成两种复杂的分子结构：桥联双环[3.1.1]庚烷-2,4-二酮和稠合双环[3.2.0]庚烷-2,4-二酮。进一步的机理研究证明双(肉桂酰)烯酮二硫代缩醛可以被可见光直接激发，并利用DFT计算探索了非常规的交叉[2+2]环加成过程。