Methylenation for Aldehydes and Ketones Using 1-Methylbenzimidazol-2-yl Methyl Sulfone
The methylenation reagent 1-methylbenzimidazol-2-yl methyl sulfone 2 reacts with various aldehydes and ketones in the presence of t-BuOK (room temperature, 1 h) in dimethylformamide to give the corresponding terminal alkenes generally in high yields. For sensitive substrates, the reaction is better carried out at low temperature using sodium hexamethyldisilazide in 1,2-dimethoxyethane. The byproduct is easily removed from the products, and the reaction conditions are mild and practical. Reagent 2 can be easily prepared from commercially available 2-mercaptobenzimidazole 5 in 95% yield without any expensive reagents.
Ionic liquids - Promoted S-methylation of thiols utilizing dimethyl carbonate
Convenient and efficient S-methylation of mercaptans or thiophenols occurs with dimethyl carbonate (DMC) in room temperature ionic liquids (RTILs) [Bmim]Cl. [Bmim]Cl can be recycled in four subsequent runs with only a gradual decrease in activity. A possible mechanism of this transformation is also discussed. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. Copyright Taylor & Francis Group, LLC.