Facile acid-promoted decarboxylation of a macrocyclic complex. Crystal structure of [6,14-diacetyl-7,13-dimethyl-1,4,8,12-tetraazacyclopentadeca-1(15),5,7,13- tetraen-2-olato]nickel(II)

A new chiral tetradentate compound has been prepared from (S)-2,3-diaminopropanoic acid and 3-ethoxymethylenepentane-2,4-dione and the corresponding nickel(II) and palladium(II) complexes have been characterized. The racemic form of the nickel(II) complex underwent template-controlled ring closure with 1,3-diaminopropane to form a new 15-membered carboxylato-substituted macrocycle. In the presence of acid, this species underwent an unusual and facile oxidative-decarboxylation reaction to produce a new hydroxy-substituted macrocycle, the crystal structure of which has been determined.