Both triads of I-pyridyl-l,3-butanediones and 1,3-dipyridyl-l,3-propanediones, easily accessible by Claisen condensation, inspired us to the study of some reactions. In the first place we were interested in the reductions of diketones I with zinc and formic acid. We already had some experience with this reaction in the pyridine series1 ... It was found that in the mentioned reduction of all three I-pyridyl-l,3-butane- diones (I) only the attack on one keto group takes place, ...