DABCO-based ionic liquids: recyclable catalysts for aza-Michael addition of α,β-unsaturated amides under solvent-free conditions
Anguo Ying1, Zhifeng Li, Jianguo Yang
1School of Pharmaceutical and Chemical Engineering, Taizhou University , Taizhou 318000, People's Republic of China.
Abstract:
An array of novel 1,4-diazobicyclo[2.2.2]octane (DABCO) based ionic liquids were developed and used as recyclable catalysts for the aza-Michael addition at room temperature without any organic solvent. [DABCO-PDO][OAc] was found to be the most efficient catalyst, and the amount of catalyst was only 10 mol %. Various amines reacted with a wide range of α,β-unsaturated amides, smoothly affording target products in good to excellent yields within hours. Moreover, the catalyst could be reused up to eight times, still maintaining a high catalytic activity. Finally, a plausible mechanism was proposed. FTIR and computational chemistry were used to verify the catalytic mechanism.
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