Schiff-base template synthesis of tetra-aza macrocycles involving diethylmalonate as a padlock

Diethylmalonate acts as an efficient locking fragment in the CuII directed synthesis of 14-membered tetra-aza-macrocycles. In the reaction of [CuII(en)2+ (en = 1,2-diaminoethane) with 2 equiv. of diethylmalonate in the presence of formaldehyde and triethylamine the 1,4,8,11-tetraazacyclotetradecane-6,6,13,13-tetracarboxylic acid tetraethyl ester copper(II) diperchlorate complex salt is formed: monoclinic, space group C2/c with , and Z = 4 (R = 0.072, Rw = 0.072). The formaldehyde building block can be replaced by benzaldehyde in the same type of template procedure if the two en fragments are replaced by the tetra-amine 2.3.2-tet (N/N′-bis-(2-amino-ethyl)-propane-1,3-diamine) and if the synthesis is carried out under strictly anhydrous conditions. The 5,7-diphenyl-1,4,8,11-tetraazacyclotetradecane-6,6-dicarboxylic acid diethyl ester copper(II) diperchlorate complex is obtained in good yield and exhibits a regular square coordination which is not disturbed by the bulky phenyl substituents