Barluenga José, Alonso Jorge, Fañanás Francisco J
Instituto Universitario de Química Organometálica "Enrique Moles", Unidad Asociada al CSIC, Universidad de Oviedo, Julián Clavería 8, 33006 Oviedo, Spain.
Chemistry. 2005 Aug 19;11(17):4995-5006. doi: 10.1002/chem.200500164.
beta-Substituted alkenylcarbene complexes react with methyl ketone lithium enolates to give different carbocyclization products depending on the structure of the lithium enolate, on the metal of the carbene complex, and on the reaction media. Thus, the reactions of aryl and alkyl methyl ketone lithium enolates with beta-substituted alkenyl chromium and tungsten carbene complexes in diethyl ether afford 1,3-cyclopentanediol derivatives derived from a formal [2+2+1] carbocyclization reaction. However, the lithium enolates of acetone and tungsten complexes furnish formal [3+2+2] carbocyclization products. In the case of alkynyl methyl ketone lithium enolates, competitive formal [2+2+1] and [3+2] carbocyclization reactions occur and 1,3-cyclopentanediol and 3-cyclopentenol derivatives are formed. Conversely, alkenyl methyl ketone lithium enolates react with alkenylcarbene complexes under the same reaction conditions to form 2-cycloheptenone derivatives by a formal [4+3] carbocyclization reaction. Finally, when the reaction was performed in the presence of a coordinating medium, the [3+2] carbocyclization pattern was observed independently of the nature of the methyl ketone lithium enolate used.
β-取代的烯基卡宾配合物与甲基酮的烯醇锂盐反应，根据烯醇锂盐的结构、卡宾配合物的金属以及反应介质的不同，会生成不同的碳环化产物。因此，芳基和烷基甲基酮的烯醇锂盐与β-取代的烯基铬和钨卡宾配合物在乙醚中反应，通过形式上的[2+2+1]碳环化反应得到1,3-环戊二醇衍生物。然而，丙酮的烯醇锂盐与钨配合物则生成形式上的[3+2+2]碳环化产物。对于炔基甲基酮的烯醇锂盐，会发生竞争性的形式上的[2+2+1]和[3+2]碳环化反应，并生成1,3-环戊二醇和3-环戊烯醇衍生物。相反，烯基甲基酮的烯醇锂盐在相同反应条件下与烯基卡宾配合物反应，通过形式上的[4+3]碳环化反应生成2-环庚烯酮衍生物。最后，当反应在配位介质存在下进行时，无论使用何种甲基酮烯醇锂盐，都会观察到[3+2]碳环化模式。
