Reaction of polyamines with diethyloxalate: A convenient route for the synthesis of tetraazacycloalkanes

Abstract

The reactivity of various polyamines with diethyloxalate has been investigated. It appears that, in similar experimental conditions, primary diamines give predominantly [2+2] adducts while the use of secondary benzylated polyamines results in [1+1] condensation. Although the intermediate tetraamides formed in the first case are extremely poorly soluble and show very slow reactivity towards reducing agents, cyclam has been obtained by using ultrasounds during the reaction of the corresponding tetraoxomacrocycle with BH3/THF. The [1+1] cyclization reaction of diversely N-benzylated linear tetraamines, whose selective syntheses have been devised herein, gives access to various N-benzylated cyclens and cyclams. New macrocyclic ligands containing both amine and amide type nitrogen atoms have been formed as intermediates in these syntheses. Two compounds containing an aminal function exhibit an unexpected reactivity, leading to the formation of new bisaminal products whose structures have been established by X-ray diffraction.