ABSTRACT
Studies of the catalytic reductive N-methylation of polyamines have elucidated key aspects of the reaction mechanism. In investigations of the reductive pennethylation of a homologous series of diamines, ranging from 1 ,2ethanediamine to 1,6-hexanediamine, it was discovered that selectivity to byproduct formamides was much greater for 1 ,3-propanediamine as compared to the other diamines. Detailed studies of 1 ,3-propanediamine and derivatives revealed the presence of intennediate cyclic aminals (hexahydropyrimidines) during N-methylation. Further probe reaction studies positively confirmed the intennediacy of the cyclic aminals in the formation of by-product formarnides. Though certain details of the mechanism require further study, a generalized reaction scheme that accounts for products and by-products, as well as the differences in selectivity for ethylenearnine and propyleneamine substrates, has been developed.
