Organocatalyst Efficiency in the Michael Additions of Aldehydes to Nitroalkenes in Water and in a Ball-Mill

摘要

The enantioselective organocatalytic Michael addition in aqueous solution was compared with the reaction performed under solvent-free ball-milling conditions. A range of pyrrolidine-derived organocatalysts were tested in the addition of aldehydes to nitroalkenes. Both procedures afforded good yields, diastereoselectivities, and enantioselectivities. The best catalyst in aqueous media was O-lauroyl-trans-4-hydroxyproline, whilst the ball-milling technique was most-efficient with a,a-diphenyl-2-pyrrolidinemethanol trimethylsilyl ether.