Mass and 13C
nuclear magnetic resonance spectroscopy are used to determine the structures of
the poly(N-methylpyrrolidines), poly(N-methylpiperidines) and low molecular weight products
obtained from N-allyl-N-methyl(2-substituted allyl)amines by cyanoisopropyl radical induced cyclizations.
The structures are used to determine the preferred site of initial radical
addition to the diallylamine and the subsequent
direction of cyclization of the intermediate azaheptenyl
radicals. Steric interactions induced by the β-substituents tend to favour
attack at the unsubstituted allyl group whereas conjugated substituents favour
attack at the substituted group with the consequent formation of
conjugation-stabilized radicals. Kinetically controlled cyclization to the pyrrolidines occurs in all cases except that of the t-butyl
derivative in which steric interactions induce cyclization to both piperidine and pyrrolidine
products.