1‐Benzoyl‐1‐(o‐alkoxyphenyl)cyclopropanes undergo Yang photocyclization to form dihydrobenzo‐pyranols in a stereospecific manner. The cyclopropyl group at alpha position to carbonyls gives not only a bias in the most stable geometries of the starting ketones but also conformational restriction on geometries of biradical intermediates. More importantly, intramolecular hydrogen bonds seem to give an
1-苯甲酰基-1-(邻-烷氧基苯基)
环丙烷经过杨光环化反应以立体定向方式形成二氢苯并
吡喃醇。在羰基的α位上的环丙基不仅会给起始酮的最稳定几何结构带来偏倚,而且还会对双自由基中间体的几何结构产生构象限制。更重要的是,分子内氢键似乎对双自由基反应性的构象控制产生附加作用。