Synthesis and stereochemistry of highly crowded N-benzylpiperidones

► The new piperidin-4-one adopts chair conformation with equatorial substituents. ► The N-benzylpiperidin-4-ones are also in the chair conformation with equatorial substituents. ► The highly crowded 3,5-dialkylcompounds also adopt similar stereochemistry of 3-alkyl analogs. ► The N-benzylation significantly changed the chemical shifts but no conformational changes. ► The N-benzylpiperidin-4-ones exist in the chair form in solid state as well, witnessed by XRD.