Crystal Structures of Ethyl 4-(4-Florophenyl)-6-phenyl-2-substituted-3-pyridinecarboxylates

Three substituted pyridinecarboxylates were synthesized; (I) ethyl 2-bromo-4-4(fluorophenyl)-6-phenyl-3-pyridinecarboxylate, C20H15BrFNO2, (II) ethyl 4-(4-fluorophenyl)-2-(4-morpholinyl)-6-phenyl-3-pyridinecarboxylate, C24H23FN2O3, and (III) ethyl 4-(4-fluorophenyl)-6-phenyl-2-(1-piperidinyl)-3-pyridinecarboxylate, C25H25FN2O2. It was found that compound (I) belongs to the orthorhombic system with space group P212121, compound (II) to the monoclinic system with space group P21/c, and compound (III) to the monoclinic system with space group C2/c. The morpholine ring in (II) and piperidine ring in (III) have the shape of the distorted chair configuration. 1. Introduction Nicotinate (3-pyridinecarboxylate) esters represent an important class of heterocyclic compounds characterized by highly pronounced pharmacological and biological importance. Many publications have reported on numerous activities of various 3-pyridinecarboxylate esters as agrochemical fungicides [1, 2], herbicides [3, 4], A3 adenosine receptor antagonists [5], cholesteryl ester transfer protein inhibitors [6], blood circulation promoters, and anti-inflammatory agents [7, 8]. Pharmacological compositions containing nicotinate esters have been, also, appeared for using as antidandruff, anti-itching, and hair loss preventing [9, 10]. 2. Materials and Methods 2.1. Synthesis 2.1.1. Ethyl 2-Bromo-4-(4-fluorophenyl)-6-phenyl-3-pyridinecarboxylate (I) To a solution of ethyl 4-benzoyl-3-(4-fluorophenyl)-2-cyanobutyrate (10？mmol) in glacial acetic acid (20？mL), heated at 60–70°C, a solution of bromine (11？mmol) in glacial acetic acid (5？mL) was added dropwise while stirring, at such a rate maintaining the same temperature (15？min.). After complete addition, stirring was continued for 3？h at the same temperature. Then, the reaction mixture was stored at room temperature (25–30°C) overnight and poured into ice-cold water (200？mL). So, the separated solid was collected, washed with water, and crystallized from ethanol giving the corresponding compound (I) as colourless crystals. Reaction time 40？h; m.p. 134–136°C; yield 0.8？g (79%). Anal. for C20H15BrFNO2 (400.24): calcd. C 60.01, H 3.78, and N 3.50; found: C 60.22, H 3.70, and N 3.47, Figure 1. Figure 1: Scheme for synthesis of the investigated compounds. 2.1.2. Ethyl-4-(4-fluorophenyl)-2-(4-morpholinyl)-6-phenyl-3-pyridinecarboxylate (II) A mixture of (I) (2.5？mmol) and the corresponding secondary amine (10？mmol) in tetrahydrofuran (20？mL) was boiled under reflux for the appropriate time. The clear reaction mixture was evaporated till dryness under