Asymmetric Michael addition of thiols to β-nitrostyrenes using a novel phenylpyrrolidine-based urea catalyst

The catalyst 1-[(3R,4S)-1-benzyl-4-phenyl-pyrrolidin-3-yl]-3-[3,5-bis(trifluoromethyl)phenyl]urea (8) designed based on 1-[(3R)-1-benzylpyrrolidin-3-yl]-3-[3,5-bis(trifluoromethyl)phenyl]thiourea (4) and 1,3-bis[(3R,4S)-1-benzyl-4-phenylpyrrolidin-3-yl]urea (7) exhibited potent catalytic activity for the asymmetric Michael addition of thiols to β-nitrostyrenes. A mere 2 mol % of the catalyst afforded 2-nitro-1-phenylethylsulfides in high yields of up to 93% ee.

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