Reaction of diethyl vinylphosphonate with 1,3-benzothiazol-2-amine

Abstract

Development of methods for the synthesis of new aminophosphoryl compounds is an important field of modern organoelement chemistry due to wide potential of using them as biologically active substances, extractants, and membrane carriers [1–3]. Of particular interest are phosphonates functionalized by pharmacophoric nitrogen-containing heterocyclic fragments. With the goal of obtaining such derivatives, we have studied the reaction of diethyl vinylphosphonate (1) with 1,3-benzothiazol-2-amine (2). An equimolar mixture of compounds 1 and 2 was heated for 25 h at 70°C. Repeated washing of the reaction mixture with hexane until constant refractive index gave a thick yellow transparent oil. The P NMR spectrum of the product contained only one signal at δP 28 ppm, indicating that the reaction was selective. The reaction of vinylphosphonate 1 with aminobenzothiazole 2 can take two paths involving attack on the β-carbon atom of the vinyl group by the endocyclic nitrogen atom of 2 with formation of adduct 3 (path a) or by the exocyclic amino nitrogen atom with formation of adduct 4 (path b). The H NMR spectrum of the product contained the following signals (CDCl3), δ, ppm: 1.36 t (6H, CH3CH2O, JHH = 7.06 Hz), 2.28 m (2H, PCH2, JPH = 18.6, JHH = 7.6 Hz), 3.82 m (2H, CH2N), 4.15 m (4H, CH3CH2O), 5.71 br.s (NH), 7.10–7.50 m (4H, Harom). We previously studied the reaction of diethyl 3-methylbuta-1,2-dien-1-ylphosphonate with 2-aminobenzothiazole [4], and the structure of the product was determined by X-ray analysis. It was found that the addition involved the endocyclic nitrogen atom. Taking these data into account, we presumed that the addition of phosphonate 1 to aminobenzothiazole 2 yields diethyl 2-[2-imino-1,3-benzothiazol-3(2H)-yl]ethylphosphonate (3). The above given H and P NMR spectral data are consistent with structure 3. Yield 64%, nD = 1.5553. Found, %: C 49.23; H 5.81. C13H19N2O3PS. Calculated, %: C 49.67; H 6.05. The H and P NMR spectra were recorded on a Varian Unity-300 spectrometer a t 300 and 121.4 MHz, respectively. The chemical shifts were measured relative to the residual proton signal of the solvent (H) or 85% H3PO4 (P, external standard). This study was funded by the subsidy allocated to Kazan Federal University for the project part of the state assignment in the sphere of scientific activities. ISSN 1070-4280, Russian Journal of Organic Chemistry, 2015, Vol. 51, No. 4, pp. 593–594. © Pleiades Publishing, Ltd., 2015. Original Russian Text © N.G. Khusainova, E.P. Pogodina, 2015, published in Zhurnal Organicheskoi Khimii, 2015, Vol. 51, No. 4, pp. 609–610.