condensation, underwent intramolecular [2 + 2] cycloaddition in the presence of Lewis acid to form bicyclo[4.2.0] (26-57% yield) and bicyclo[3.2.0]skeleton (14-38% yield), respectively. Similar treatment of homologous 1,3-dienylphosphonate 11 and 1,3,5-trienylphosphonate 12 resulted in the formation of ionone derivatives (30-94% yield). The intramolecular cycloaddition reaction was applicable to several
通过Knoevenagel缩合制备的α-酯取代的1,3-二烯基
膦酸酯7和8,在
路易斯酸存在下进行分子内[2 + 2]环加成反应,形成双环[4.2.0](产率26-57%),并且双环[3.2.0]骨架(产率14-38%)。同源的1,3-二烯基
膦酸酯11和1,3,5-
三烯基
膦酸酯12的类似处理导致紫罗兰酮衍
生物的形成(30-94%产率)。分子内环加成反应适用于几种带有酯基的共轭二烯。