α-Fluoro-α-nitro(phenylsulfonyl)methane as a fluoromethyl pronucleophile: Efficient stereoselective Michael addition to chalcones

Highly efficient stereoselective 1,4-addition of racemic alpha-fluoro-alpha-nitro(phenylsulfonyl) methane (FNSM) as a fluoromethyl pronucleophile to alpha,beta-unsaturated ketones using a wide range of chiral organobifunctional catalysts under moderate conditions in the absence of an additional base has been achieved. A series of catalysts was screened for the enantioselective addition of FNSM to chalcones and the catalysts CN I, CD I, QN I-IV, and QD I were found to enable this reaction, successfully providing exclusive 1,4-addition products stereoselectively in high yields (conversion, diastereomeric ratio, and enantiomeric excess). Studies involving a model reaction and systematic analysis of the absolute configuration support the suggested mechanism.