Polyvinylidene chloride supported L -prolineamide as recoverable catalyst for asymmetric aldol reaction between ketone and aromatic aldehyde

摘要

A series of prolineamide modified by polyvinylidene chloride (PVDC) was synthesized and used as green recoverable organocatalysts for the asymmetric Aldol reactions between various ketones and aromatic aldehydes. The effects of solvent and catalyst dosage on the catalytic performances of as-synthesized organocatalysts were investigated. It was found that as-synthesized PVDC-supported L-prolineamides possessed good catalytic performance for the asymmetric Aldol reactions between cyclohexanone and a variety of aromatic aldehydes, affording high yields of up to 99%, excellent diastereoselectivities of up to above 8: 92 d.r. value, and high enantioselectivities of up to above 92.3% e.e. value. In general, the catalytic performance of as-synthesized organocatalysts closely depended on the catalyst dosage and solvent type as well. Particularly, as-synthesized organocatalyst 1c, at a dosage of 5 mol % in 10 μL of water, exhibited high catalytic activity and stereoselectivity for the asymmetric Aldol reaction between cyclohexanone and p-nitrobenzaldehyde at room temperature. In the meantime, it could be easily recovered and recycled, while the activity and enantioselectivity were nearly completely retained even after five cycles of recovery, showing promising application as an efficient green organocatalyst for the aforementioned asymmetric Aldol reactions.