A novel and concise synthetic access to chiral 2-substituted-4-piperidone

A novel and concise synthetic access to enantiopure chiral 2-aryl/alkyl substituted 4-piperidone has been demonstrated. This new route features two key steps: the highly diastereoselective conjugate addition of homochiral lithium amides to trans-β-substituted-α,β-unsaturated methyl esters guaranteed the enantiopurity at 2 position (de >19:1) and the intramolecular attacking of carbanions to methyl esters led to the formation of the piperidone ring. A wide range of substrates, including chiral 2-aryl and 2-alkyl-4-piperidones, were successfully synthesized with modest to high yield. Moreover, some non-chiral 3-substituted-4-piperidones were also synthesized with enhanced ring-formation yield, implicating the versatility of this method in construction of various piperidine rings.