Synthesis of 2-chloro-2-imidoylaziridines via aza-Darzens-type reaction of 3,3-dichloro-1-azaallylic anions and N-(arylsulfonyl)imines.

3,3-Dichloro-1-azaallylic anions, generated by deprotonation of alpha,alpha-dichloroketimines 10 with lithium diisopropylamide, reacted with N-sulfonylaldimines 7 to produce the Mannich-type products N-[2,2-dichloro-3-(N-alkylimino)-1,3-diarylpropyl]benzenesulfonamides 11. The latter stable compounds were hydrolyzed at the imino functionality to afford N-[2,2-dichloro-3-oxo-1,3-diarylpropyl]benzenesulfonamides 12 in excellent yields. N-[2,2-Dichloro-3-(N-alkylimino)-1,3-diarylpropyl]benzenesulfonamides 11 were cyclized to cis-3-aryl-2-chloro-2-imidoylaziridines 19 in 81-99% yield with high diastereoselectivity, representing a novel and readily available class of stable 2-chloroaziridines. Finally, a highly stereoselective entry to 2-(aminomethyl)-2-chloroaziridines 27 (70-98% yield; de > 95-99) was worked out from the reaction of cis-3-aryl-2-chloro-2-imidoylaziridines 19 and sodium cyanoborohydride in the presence of acetic acid. The latter 2-(aminomethyl)aziridines 27 represent stereochemically defined small azaheterocyclic rings which were scarcely reported in the literature.