Diethyl 2-aryl-4-hydroxy-4-methyl-6-(thio)semicarbazonocyclohexane-1,3-dicarboxylates were synthesized, and their structure was determined by 1 H and 13 C NMR spectroscopy, including the HSQC technique. The molecular and crystalline structure of diethyl 4-hydroxy-4-methyl-6-thiosemicarbazono-2-phenylcyclohexane-1,3-dicarboxylate was determined by X-ray analysis. Ia, IIa, IIb, Ar = Ph; Ib, IIc, Ar = 4-MeOC 6 H 4 ; Ic, IId, Ar = 3-O 2 NC 6 H 4 ; Id, IIe, Ar = 4-HO-3-MeOC 6 H 3 ; Ie, IIf, Ar = 2-thienyl; X = S (a), O (b-f).Polycarbonyl compounds of the dialkyl 2-aryl-4-hydroxy-4-methyl-6-oxocyclohexane-1,3-dicarboxylate series (β-keto esters) are used as model structures for stereochemical studies and keto-enol transformations, as well as intermediate products in the synthesis of carbo-and heterocyclic systems [1][2][3]. Their reactions with nitrogen-centered nucleophiles have been well documented; depending on the nucleophile structure, these reactions lead to the formation of enamines, oximes, fused heterocycles, and heterocyclic spiro compounds whose structure was determined by spectral methods and X-ray analysis [4][5][6][7].Reactions of such β-keto esters with thiosemicarbazides have been studied in the recent years [3,8]; however, the available spectral data (IR, 1 H NMR) are clearly insufficient to unambiguously assign the struc-
