There is a large body of publications on the synthesis and chemical properties of various derivatives of 4,7-dihydro[1,2,4]triazolo[1,5-a]pyrimidine, 1,2 including those containing an acceptor substituent at position 6. 3 At the same time, derivatives of 4,7-dihydro[1,2,4]triazolo[1,5-a]-pyrimidine-6-sulfonamides which are of interest due to their biological properties 3f are still not well studied. The goal of this work was the synthesis of these substances.The starting β-ketosulfonamides 3а,b were prepared by us according to a literature method 4 using 1-(methylsulfonyl)piperidine (1) as the starting material (Scheme 1). Compound 1 was metalated at -15 °C in THF solution by the action of 2.5 M solution of n-butyllithium in hexane; the resulting lithium salt was treated with a solution of the corresponding aliphatic aldehyde in THF with cooling. Work-up of the reaction mixture afforded the corresponding β-sulfoalcohols 2а,b, which were further oxidized by Jones reagent affording the required β-sulfoketones 3a,b. 5 The yield of compounds 3а,b (based on compound 1) was 86 and 98%, respectively.The reaction of compounds 3a,b, aromatic aldehydes, and 3-amino-1,2,4-triazole in boiling DMF led to the formation of the target compounds 4a-e in 18-42% yields (Scheme 2). The low yields were probably due to both the A three-component condensation of 1-(1-piperidinylsulfonyl)acetones, aromatic aldehydes, and 3-amino-1,2,4-triazole in DMF leads to the formation of 5-alkyl-6-(1-piperidinylsulfonyl)-4,7-dihydro[1,2,4]triazolo[1,5-a]pyrimidine derivatives. If 4-nitrobenzaldehyde is employed, 5-methyl-7-(4-nitrophenyl)[1,2,4]triazolo[1,5-a]pyrimidine is the single isolated reaction product. The starting 1-(1-piperidinylsulfonyl)acetones were obtained from 1-(methylsulfonyl)piperidine in sequential metalation with n-butyllithium, reaction with aliphatic aldehydes, and oxidation of the obtained sulfoalcohols.