One-pot stereoselective synthesis of anti 3-alkyl and 3-aryl-N-p-tosyl- aziridine-2-ketones and 3-aryl-N-p-tosyl-aziridine-2-carboxylates

An efficient and practical synthesis of N-p-tosyl-aziridine-2-ketones and carboxylates through the use of α,β-unsaturated esters and ketones has been reported. The synthesis was conducted via a one-pot procedure consisting of aminohalogenation and in situ intramolecular S_N2 substitution. Triethylamine was found to be an effective base for the in situ cyclization for most substrates. Interestingly, for several enone cases, a slightly modified procedure in which 1.0 equivalent of p-TsNCl₂ was slowly added into 2.0 equivalents of enone for aminohalogenation followed by quenching with aqueous Na₂SO₃ resulted in crude aziridines which were proven to be nearly pure by the crude ¹H NMR analysis. Moderate to good yields and excellent anti stereoselectivity were achieved for 21 examples.