Salts of 1,1-dimethyl-2-acylhydrazines andThe information available on the reaction of acrolein [1, 2] and methyl vinyl ketone [3, 4] with N,N-dimethylhydrazine salts, on one hand, and ~e reaction with. 1-alkyl-'and 1,aryl-2-acylhydrazines [5][6][7], on the other, indicated the feasibility of a reaction between ~x,/3-unsaturated carbonyl compounds and salts of 1,1-dialkyl-2-acylhydrazines and N,N-dialkylhydroxylamines, which was shown to be possible in principle in our previous work [8]. Detailed results are given here on the features of this reaction and the structure of its products. We found that the reaction proceeds only with a,/3-unsaturated carbonyl compounds possessing an unsubstituted vinyl group. Mesityl oxide, crotonaldehyde, cinnamaldehyde, and metfiacrolein all do not undergo this reaction. However, the reaction readily proceeds with acrolein, methyl vinyl ketone, and phenyl vinyl ketone to give 1:1 addition products (I-XII) in rather high yields (Table 1).The structures of I-XII are determined by the nature of the substituent at the carbonyl group. In the reaction with acrolein, independently of the nature of the substituent at the acyl group of the hydrazide molecule, products I-IV have the cyclic structure of 1,1-dialkyl-2-acyl-3-hydroxypyrazolidinium salts (B) similar to derivatives of hydroxylamines XI and XII, which are 2,2-dialkyl-5-hydroxyisoxazolidinium salts, as demonstrated by the PMR signals for 3-1-1 (5-H in the case of XI and XII) at 5.8-6.2 ppm and for the hydroxyl group at 6.9-9.2 ppm and by the magnetic inequivalence of the methyl groups at the nitrogen atom due to their diastereotopy ~esulting from the chiral center at the carbon atom bound to the hydroxyl group (Table 2).