X-ray Structures of Precursors of Styrylpyridine-Derivatives Used to Obtain 4-((E)-2-(Pyridin-2-yl)vinyl)benzamido-TEMPO: Synthesis and Characterization

摘要

The synthesis and characterization of the precursor isomers trans-4-(2-(pyridin-2-yl)vinylbenzaldehyde (>I), trans-4-(2-(pyridin-4-yl)vinylbenzaldehyde (>II), trans-4-(2-(pyridin-2-yl)vinylbenzoic acid (>III) and (E)-4-(2-(pydridin-4-yl)vinylbenzoic acid (>IV) are reported. These compounds were prepared in order to obtain trans-4-((E)-2-(pyridin-2-yl)vinyl)benzamide-TEMPO (>V). Compounds >I and >II were obtained by using a Knoevenagel reaction in the absence of a condensing agent and solvent. Oxidation of the aldehyde group using the Jones reagent afforded the corresponding acid forms >III and >IV. A condensation reaction with 4-amino-TEMPO using oxalyl chloride/DMF/CH2Cl2 provided the 4-((E)-2-(pyridin-2-yl)vinyl)benzamide-TEMPO. Single crystals of compounds >I, >II and >III were obtained and characterized by X-ray diffraction. Compound >I belongs to space group P21/c, a = 12.6674(19) Å, b = 7.2173(11) Å, c = 11.5877(14) Å, β = 97.203(13)° and the asymmetric unit was Z = 4, whereas compound >II was in the space group P21, with a = 3.85728(9) Å, b = 10.62375(19) Å, c = 12.8625(2) Å, β = 91.722 (2)° and the asymmetric unit was Z = 2. Compound >III crystallized as single colorless needle crystals, belonging to the monoclinic system with space group P21, with Z = 2, with a = 3.89359(7) Å, b = 17.7014(3) Å, c = 8.04530(12) Å, β = 94.4030 (16)°. All compounds were completely characterized by IR, ¹H-NMR, EI-MS and UV-Vis.