Experimental and Theoretical Approach to Novel Polyfunctionalized Isoxazole

A novel, fast, and straightforward procedure for the synthesis of di- and trifunctionalized isoxazoles starting from 2-ethoxymethylenemalononitrile with different ratios of hydroxylamine in the presence of sodium acetate is described in this paper. The current method’s features include the availability of the starting materials, moderate reaction conditions, and the simplicity of the workup. The structures are characterized using different spectroscopic studies, such as infrared (IR), ¹H/¹³C nuclear magnetic resonance (NMR), and elemental analysis, in addition to X-ray single-crystal determination. The gauge-invariant atomic orbital (GIAO) ¹H and ¹³C NMR chemical shift values of 5-aminoisoxazole-4-carbonitrile and 3,5-diaminoisoxazole-4-carboxamide are calculated in the ground state using the density functional theory (DFT) with the 6-311+G(d, p) basis set and are compared with the experimental data, in addition to the calculation of the molecular electrostatic potential (MEP) distribution, and the frontier molecular orbitals (FMOs) for the synthesized isoxazoles are illustrated theoretically.