in competition with the substitution products, i.e. 2-(tert-butoxymethyl)aziridines. Various attempted functionalizations of 1-(arylmethyl)-2-methyleneaziridines failed, but they proved to be excellent substrates for the synthesis of beta-lactam derivatives, i.e. 1-(arylmethyl)-2-iminoazetidines, through ring expansion with azides carrying electron-withdrawingsubstituents.
Mechanistic Considerations for the Consecutive Cyclization of 2,3-Dibromopropylamine Hydrobromide Giving a Strained Molecule, 1-Azabicyclo[1.1.0]butane
The effective formation of 1-azabicyclo[1.1.0]butane (2) by treatment of 2,3-dibromopropylamine hydrobromide (1) with n-BuLi could be understood considering a rational reaction pathway via both transition states 10 and 19 based on the intramolecular Br···Li+ coordination. A similar cyclization pathway starting from N-benzyl-3-bromopropylamine hydrochloride (17) to afford N-benzylazetidine (18) could also be postulated on the basis of a transition state 20 involving the intramolecular Br···Li+ coordination.