Saturated five membered heterocyclics, II: Preparation of 1,3,4‐oxadiazolidines

2,3,4,5-Alkyl substituted 1,3,4-oxadiazolidines are prepared in good yields by reaction of a symm.dialkylhydrazine and an aliphatic aldehyde. Two alternate mechanisms of the reaction are discussed. The N.M.R. spectra could be analysed taking into account the possible stereochemical configurations.