Reaction of activated 2,2-dimethylaziridines with Grignardreagents RMgHal in boiling THF can yield the products of normal aziridine ring opening, the rearranged opening products , and the methallylamides (isomers of ). 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 is opened (reversibly for A = sulfonyl)