E. Matter (1) has recently described, as one product of interaction between acetone and ammonia, 2,2,4,6,6-pentamethyl-1,2,5,6-tetrahydropyrimidine, which could be reduced by means of sodium and alcohol to the corresponding hexahydro compound (I).1 Its structure derives from the observation that both dilute hydrochloric acid and alcoholic sodium hydroxide solution decompose it into 2,4-diamino-4-methylpentane (II) and acetone, in the manner indicated in (I). Veer (3) had observed the same degradation, by acids, of the condensation products from 1,3-dianilinopropane and aldehydes, which he also considered as hexahydr opyrimidines.We wish to report in this connection that substances of the type (I) are obtained easily and in good yield, when a 1,3-diamine such as (II) is heated with a ketone in benzene solution in such a way that the water liberated is continuously removed in form of its azeotrope with benzene. Obviously, acetone which boils below that azeotrope (63°) cannot be condensed with (II) by this method; but 3-methyl-3-butanol-2-one (III) and cyclohexanone reacted in the desired manner.