Aminals as substrates for sulfur ylides:: A synthesis of functionalized aziridines and N-heterocycles

Sulfur ylides stabilized by Ar, vinyl, or amide groups react with five-membered-ring tert-butylsulfinyl aminals to give functionalized chiral, nonracemic aziridines in high yield and with good selectivities ( up to 15:1 trans: cis, up to > 95: 5 trans dr, always > 95:5 cis dr). The intermediate aziridines can be converted into pyrrolidines or piperidines depending on the reaction conditions.