Benzotropones 6 react with dienophiles 7 to give endo-adducts 8 as shown by PMR. Unlike similar ketones which usually undergo 1,3-acyl shifts or oxadi-π-methane rearrangements, these ethenobenzocycloheptenones 8, on direct or sensitized irradiation, lead to the di-π-methane rearrangement products 1H-benzo[f]cycloprop[cd]-indenones 9. The structures of the latter were elucidated by the use of Eu(FOD)3
Benzotropones 6与亲二烯体反应,7,得到内型-adducts 8如图PMR。与通常经过1,3-酰基转移或恶二酮-π-
甲烷重排的类似酮不同,这些
乙炔苯并
环庚烯酮8在直接或敏化辐射下会导致二-π-
甲烷重排产物1H-苯并[f]环丙[cd] -
茚二酮9。通过使用Eu(FOD)3和X射线衍射阐明了后者的结构。四氢
芴酮19的长时间辐射(乙苯并
环庚烯酮的潜在1,3-酰基转移产物)仅产生二烯基醛21低转换率。这些结果表明,在这些反应中选择的
化学途径取决于几何和电子因素。