Reaction of aromatic aldehydes with β-dicarbonyl compounds in a catalytic system: Piperidinium acetate-1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid

Abstract

Condensation of aromatic (heteroaromatic) aldehydes with 1,3 dicarbonyl com pounds under the 1 butyl 3 methylimidazolium tetrafluoroborate ([Bmim][BF 4 ]) ionic liq uid-piperidinium acetate catalytic system (0.2 equiv. of each component) in the absence of a solvent affords, depending on the structures of the reagents, 2 arylidene derivatives of methyl acetoacetate and acetylacetone, diethyl 2,4 bis(trifluoroacetyl) 3 phenylpentanedioate, or di methyl 2 aryl 4 hydroxy 6 oxocyclohexane 1,3 dicarboxylates. The reactions of the resulting 2 arylidene derivatives with O methylisourea in the [Bmim] [BF 4 ] ionic liquid produced me thyl 2 methoxy 4 methyl 6 aryldihydropyrimidine 5 carboxylates and 1 (2 methoxy 4 me thyl 6 phenyldihydropyrimidin 5 yl)ethanone (mixtures of 3,6 and 1,6 dihydro isomers), which were transformed into the corresponding 3,4 dihydropyrimidin 2(1H ) one derivatives.

Update 1 of: Ionic Liquids in Heterocyclic Synthesis

“…Zlotin et al 416 The results of this study demonstrated that the condensation process was substantially affected by the ionic liquid. The authors affirmed that the product from the first step undergoes partial isomerization under the reaction conditions in the presence of NaHCO 3 and in an ionic liquid medium in a molar ratio of 1:0.2 (reactant/IL), which is more polar than DMF.…”

“…The authors affirmed that the product from the first step undergoes partial isomerization under the reaction conditions in the presence of NaHCO 3 and in an ionic liquid medium in a molar ratio of 1:0.2 (reactant/IL), which is more polar than DMF . This compound is then transformed into the corresponding 3,4-dihydropyrimidin-2-(1 H )-ones 134 by regioselective N -alkoxycarbonylation and O-demethylation of 132 . When the same procedure was performed with the molecular solvent DMF using K 2 CO 3 as base, the products were only attained after 16 h at room temperature .…”

“…417 This compound is then transformed into the corresponding 3,4-dihydropyrimidin-2-(1H)-ones 134 by regioselective N-alkoxycarbonylation and O-demethylation of 132. 416 When the same procedure was performed with the molecular solvent DMF using K 2 CO 3 as base, the products were only attained after 16 h at room temperature. 418 [BMIM][BF 4 ] therefore improved the reaction by dramatically reducing the reaction time.…”

“…Zlotin et al demonstrated the application of ionic liquids in the synthesis of 3,4-dihydropyrimidin-2-(1 H )-ones 132 using [BMIM]­[BF 4 ]. The reaction consisted of the condensation between 2-arylidenes 130 and O -methylisourea sulfate 131 (Scheme ).…”

Study on the Pd/C‐Catalyzed (Retro‐)Michael Addition Reaction of Activated Methylene Compounds to Electron‐Poor Styrenes

“…Electrospray ionization (positive mode) mass spectra were recorded on a WATERS LCT mass spectrometer. The styrene derivatives 1b, [14] 1c, [15] 1g, [16] and 1h [15] and the Michael adducts 3a, [17] 3c, [18] 3h, [10] 3i, [10] 3j, [19] 3k, [20] and 3l [19] were prepared according to literature procedures.…”