AbstractThe Michael addition of 2‐substituted cyclopentanones1to β‐nitrostyrene2proceeds at room temperature in the presence of catalysts such as NEt3, DMAP, KOAc, or Ni(acac)2leading to 2‐substituted 2‐(2‐nitro‐1‐phenylethyl)cyclopentanones3/4. Depending on substituents R in1compoundsrac‐3/4may be obtained with high diastereoselectivity. The influences of reaction conditions were studied and the diastereomeric ratio was determined by means of1H‐NMR spectroscopy. In the cases ofrac‐3/4a‐c,rac‐3g–i,rac‐3k, the diastereomers could be isolated in pure form. The configuration of compoundsrac‐3a,rac‐4awas establ