Berthold Buchholz

Nucleophilic cleavage of 2,2-dimethylaziridines: competition between SN2 and postulated “SET” mechanism.

Abstract Regioselectivity of nucleophilic attack on 2,2-dimethylaziridines depends on the degree of leaving group activation: in highly activated aziridines it occurs at the methylene carbon and in less activated at the tertiary carbon. This latter abnormal ring opening is explained by an SET mechanism.

Reactions with aziridines - 39 : Ring opening of activated 2,2-dimethylaziridines by grignard reagents. A mechanistic study

Abstract Reaction of activated 2,2-dimethylaziridines 1 with Grignard reagents RMgHal in boiling THF can yield the products 2 of normal aziridine ring opening, the rearranged opening products 3 , and the methallylamides 4 (isomers of 1 ). The product distribution depends on R, Hal, and experimental conditions, and very strongly on the nature of the activating group A. It is shown that 1 is opened (reversibly for A = sulfonyl) forming 10 through a Lewis acid assisted attack of Halθ on the tert carbon of 1 (abnormal opening by Halθ ). Evidence is presented to show that 4 as well as 3 come from this intermediate.

Electron attachment to N-benzoylaziridines followed by C−N homolysis of the aziridine ring

Reactions of N-benzoylaziridines with strong electron sources provided direct evidence for the formation of ketyls (2) and radicals (3), both of which are postulated intermediates in the single electron transfer mechanism of nucleophilic ring opening of activated aziridines.

Aziridines, 61. Ring Opening of 2,2-Dimethyl-l-sulfonylaziridines by Anilines: Regioselectivity and Revised Structure of Main Products

It is shown (1) that in most reactions of anilines 2 with 1-sulfonyl-2,2-dimethylaziridines 1 both isomeric products 3 and 4 are formed, (2) that the “normal” product 4 obtained by attack on position 3 of 1 usually arises in a small or negligible amount that seems to decrease with decreasing basicity of 2, and (3) that the amount of 4 strongly increases with increasing steric demand of 2. Formation of 4 is explained by a lag of bond making in SN2.