4-Methylene-2-trimethylsilyl-3-phenylcyclobutenones 3 are obtained from the corresponding cyclobutenedione 7 by Tebbe and Peterson methylenation reactions, and upon photolysis give 3-phenyl substituted allenylketenes R1CH=C=C(Ph)C(SiMe3)=C=O 4. These are more reactive in ring closure back to 3 than are the 3-trimethylsilyl analogs 1, as predicted on the basis of molecular orbital calculations. Reactions of allenylketenes 1 and 4 include addition of H2O followed by cyclization to form butenolides 13, addition of aniline to give allenyl carboxamide 14 and lactam 15, addition of CF3CO2H to form allenyl carboxylic acid 17, addition of Br2 in a 1,4-fashion to give penta-2,4-dienoic acid derivatives 18, and reaction with m-chloroperbenzoic acid to give the unique allenyl acylsilane 23. [4 + 1]-Cycloaddition reactions of 1 and 4 with Me3SiCHN2 give methylenecyclopentenones 24 and 25 while acetaldehyde undergoes BF3 · OEt2 catalyzed [2 + 2] cycloadditions forming β-lactones. [4 + 2] Cycloadditions occur with benzaldehyde to form the highly crowded exomethylene pentenolactone 29, and with TCNE forming methylenecyclohexenones 31.
4-美基-2-三甲基
硅基-3-苯基
环丁烯酮 3 由相应的
环丁烯二酮 7 经过特贝反应和彼得森反应获得,并在光解后生成 3-苯基取代的烯丙基酮烯 R1CH=C=C(Ph)C(SiMe3)=C=O 4。这些烯丙基酮烯在环闭合回到 3 时比 3-三甲基
硅基类似物 1 更具反应性,这一预测基于分子轨道计算。烯丙基酮烯 1 和 4 的反应包括与
H2O 的加成后环化形成
丁烯内酯 13,与
苯胺的加成生成烯丙基
氨基酸 14 和内酰胺 15,与 CF3CO2H 的加成形成烯丙基
羧酸 17,以 1,4 方式与 Br2 的加成生成五烯酸衍
生物 18,以及与间
氯过
苯甲酸反应生成独特的烯丙基酰基
硅烷 23。[4 + 1] 环加成反应中 1 和 4 与 Me3SiCHN2 生成亚甲基
环戊烯酮 24 和 25,而
乙醛在
BF3·OEt2 催化下发生 [2 + 2] 环加成形成 β-内酯。[4 + 2] 环加成与
苯甲醛反应形成高度拥挤的外亚甲基
戊烯内酯 29,与 TCNE 反应生成亚甲基
环己烯酮 31。