A Convenient Ruthenium-Catalysed α-Methylation of Carbonyl Compounds using Methanol
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- 作者：Tuan Thanh Dang and Abdul Majeed Seayad
- 刊名：Advanced Synthesis & Catalysis
- 出版年：2016
- 出版时间：November 3, 2016
- 年：2016
- 卷：358
- 期：21
- 页码：3373-3380
- 全文大小：1452K
- ISSN：1615-4169
文摘
An efficient ruthenium catalyst is reported, for the first time, to catalyse the α-methylation of ketones and esters using methanol as a green methylating agent. The in situ generated catalyst from the complexes [RuCp*Cl2]2 or [RuCp*Cl2]n with dpePhos provided up to quantitative yields in the presence of only 20 mol% of lithium tert-butoxide (LiO-t-Bu) as a base. Regioselective mono- or multi-methylation could be effectively controlled by temperature. This catalyst system was also effective for the one-pot sequential α-alkylation–α-methylation of methyl ketones and conjugate reduction–α-methylation of α,β-unsaturated ketones to synthesise α-branched ketones. An application of the α-methylation of esters using the ruthenium catalyst was demonstrated for an alternative catalytic synthesis of Ketoprofen.