Compounds containing both a primary or secondary amine and carbonyl functional group are often labile.  This guideline applies to amino aldehydes, amino-ketones, and amino-esters; indeed a molecule cannot carry simultaneously (unprotected) aldehyde and amine groups. Aminoacetone, the simplest amino ketone, cannot be isolated as a liquid or solid, and 2-aminobenzaldehyde oligomerizes in solution or in the melt.  An α-formyl aziridine, reduced with DIBAL from the ester, reversibly dimerizes to an oxazolidine: