The [2+2]photocycloaddition of alkenes and 5,6-substituted 2-oxo-2H-pyran-3-carboxylates with an ester as an electron-withdrawing group was developed. The 3,4-adducts, 4,5-disubstituted 3-oxa-2-oxobicyclo[4.2.0]oct-4-ene-1-carboxylates, were obtained in moderate yields accompanied by considerable amounts of the 5,6-adducts, 1,6-disubstituted 2-oxa-3-oxobicyclo[4.2.0]oct-4-ene-4-carboxylates. These structures, including their stereochemistry, were determined by various spectral and computational analyses, and some were examined by X-ray crystallographic analysis. The determined regio- and stereoselectivities were explained by frontier orbital theory.



中文翻译：

---

[2 + 2] 5,6-取代的2-Oxo-2的光环加成

开发了具有酯作为吸电子基团的烯烃和5，6-取代的2-氧代-2- H-吡喃-3-羧酸酯的[2 + 2]光环加成反应。3,4-加合物，4,5-二取代的3-氧杂-2-氧代双环[4.2.0]辛-4-烯-1-羧酸酯以适中的产率获得，并伴随有相当数量的5,6-加合物，1，6-二取代的2-氧杂-3-氧代双环[4.2.0]辛-4-烯-4-羧酸盐。这些结构，包括其立体化学，是通过各种光谱和计算分析确定的，其中一些通过X射线晶体学分析进行了检查。边界轨道理论解释了确定的区域选择性和立体选择性。