results in favorable spatial relationships between the alkenoyl groups to effect efficient intramolecular cycloadditions: irradiation of bis(alkenoyl)ketenedithioacetals in solution leads to facile and stereospecific intramolecular [2 + 2] photocycloadditions resulting in the formation of substituted bicyclo[3.2.0]heptane-2,4-diones, the observed conformational rigidity of which is attributed to the
在1,7-取代的1,6,6-庚二烯-3,5-二酮的C-4处引入烯酮二
硫缩醛部分引起的构象变化导致烯酰基之间的空间关系良好,从而实现了有效的分子内环加成反应:溶液中的双(烯基)酮基二
硫缩醛可导致容易的立体定向分子内[2 + 2]光环加成反应,从而形成取代的双环[3.2.0]
庚烷-2,4-二酮,其构象刚度可归因于推动作用酮二
硫缩醛基团的α-拉特性。