Effect of the solvent nature on the course of quaternization of 3,5-diethoxycarbonyl-2,6-dimethyl-4-(3-pyridyl)-1,4-dihydropyridine

Synthesis and Evaluation of Self-Assembling Properties of 3-(3,5-Difluoro-3,5-bis((alkoxy)carbonyl)-2,6-dioxoheptan-4-yl)-1-methylpyridin-1-ium Iodides

“…Firstly, the parent 2',6'-dimethyl-1',4'-dihydro-[3,4'-bipyridine]-3',5'-dicarboxylates 1a,b were obtained in good yields by three-component Hantzsch-type one-pot cyclocondensation reaction of the corresponding acetoacetate, 3-pyridinecarbaldehyde and ammonia solution in ethanol under reflux for 8 h according to the previously described procedures [23,24]. The next step-electrophilic fluorination of 1,4-DHPs 1 with Selectfluor ® (2)-was performed following a procedure elaborated by our research group [25,26] and resulted in the formation of fluorine-containing dialkyl 3-(pyridin-3-yl)pentanedioates 3a and 3b with yields of 98 and 94%, respectively.…”

“…The last step-treatment of dialkyl 2,4-diacetyl-2,4-difluoro-3-(pyridin-3-yl)pentanedioates 3 with an excess of methyl iodide-led to quaternization of the pyridine moiety and formation of target compounds-3-(3,5-difluoro-3,5-bis((alkoxy)carbonyl)-2,6-dioxoheptan-4-yl)-1-methylpyridin-1-ium iodides 4 with 56 and 43% yields, respectively. Quaternization reactions of 4-pyridyl-1,4dihydropyridines were usually carried out in acetone or in an acetone-chloroform mixture if the starting substance was insoluble in acetone [23] or in methyl ethyl ketone (MEK), which decreased the reaction time and increased the yield of product [24]. In this work, quaternization reaction was performed in MEK, and the average yields of the product can be explained by steric hindrance.…”

“…To a stirred solution of 4-pyridyl-1,4-dihydropyridines 1a,b [23,24] (1.5 mmol) in acetonitrile (15 mL), water (2 mL) was added, after which Selectfluor ® (2, 1.34 g, 3.8 mmol) was added in portions at room temperature. After being stirred at reflux for 1 h, the solvents were evaporated in vacuo.…”