The regioselectivity ratio RS = normal: abnormal opening of activated 2‐methylaziridines 2 by nucleophiles is found to range from 0.10 to unmeasurable large (only normal opening = substitution at CH2 by strongly basic carbanions). RS is assumed to result from SN2 variants differing in the degree to which bond breaking is ahead of bond making including perhaps synchronous SN2. Bond breaking will be more ahead for the N‐CMe bond. High nucleophilic power pushes bond making toward a synchronous process resulting in great RS. The decrease in RS with acyl activation relative to sulfonyl activation is in accord with a flattening of the nitrogen pyramid (planarization effect). The planarization effect is retained in acidic medium by O‐protonation: Rs 0.10–0.14 for methanolysis as compared to RS 0.43 for N‐protonated sulfonylaziridine 2h. AM1 calculations support the planarization hypothesis. – No indication for SET with trityl anion was found.

Reactions of N‐acylaziridines 1a–g (N‐benzoyl except 1d) with sodium or naphthalenide N.− in THF provide a variety of products that usually arise via the aziridino ketyls 2. Homolytic ring opening of 2 generates the amidatoalkyl radicals 3. Only with a very short reaction time were small amounts of benzil or benzoylnaphthalenes obtained indicating a reversible trapping of 2 by dimerization or coupling with N.−. Homolysis of 2 produced always the more stable 3 apart from reactions of monomethylaziridines 1c,d where the primary radical i‐3c,d is kinetically favoured. The amides R1CONHCHR4CHR2R3 (9, isopropylamides i‐9c,d from 1c,d) were usually the main products. 9 arise from 3 either by H atom abstraction from THF (probably in sodium metal runs) or by reduction of 3 to carbanions 5 that abstract a proton from THF (N.− runs). Addition of 5a (R2−4 = H) to 1a gives finally the ketone 8a. Self reaction of primary radical 3a is dimerization. Self reaction of tertiary or secondary radicals is disproportionation when an allylamide arises. This isomerizes to an enamide unless it is conjugated. R2R3CCHR4 and R1CONH2 arise (probably) always. The mechanism, possibly a cyclic process of anion 6, is not clear.

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