Abstract: The reaction of one mole of a Mannich base corresponding to the formula ##SPC1##And one mole of a Mannich base corresponding to the formula ##SPC2##Wherein R.sub.1, R.sub.2, R.sub.4 and R.sub.5 are independently selected from alkyl groups having 1 to 6 carbon atoms and R is alkyl, preferably lower alkyl, with 1 mole of a carboxylic acid ester corresponding to the formula R.sub.3 CH.sub.2 COOR.sub.4 wherein R.sub.3 is --H, --CN or --COOR.sub.4 and R.sub.4 is an alkyl, thioether, oxyether or aralkyl group having up to 20 carbons in the presence of a catalytically effective amount of an alkaline catalyst is useful for preparing compounds corresponding to the formula ##SPC3##The compounds represented by the above formula are useful as stabilizers for synthetic resins, particularly polyolefins. Compounds of the above formula, when R.sub.3 is --CN are novel and may also be prepared by reacting 1 mole of ##SPC4##And 1 mole of ##SPC5##Wherein X is halogen with 1 mole of NCCH.sub.2 COOR.sub.