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

Diethylmalonate acts as an efficient locking fragment in the Cu-II directed synthesis of 14-membered tetra-aza-macrocycles. In the reaction of [Cu-II(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 a = 12.201(5) Angstrom, b = 12.464(5) Angstrom, c = 21.353(22) Angstrom, alpha = 90 degrees, beta = 91.30(6)degrees, gamma = 90 degrees, V = 3247(4) Angstrom(3), and Z = 4 (R(W) = 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: triclinic, space group P (1) over bar, with a = 11.742(5) Angstrom, b = 16.949(8)Angstrom, c = 8.718(4) Angstrom, alpha = 101.15(4)degrees, beta = 105.92(4)degrees, gamma = 96.21(4)degrees, V = 1613(1) Angstrom(3), and Z = 2 (R = 0.047, R(W) = 0.051).