Understanding 2-(Nitromethylene)hexahydropyrimidin-5-ol Reaction Processes and NMR Spectroscopy: A Theoretical and Experimental Investigation

Ketene dithioacetals have significant applications in various fields, including natural products, pharmaceuticals, agrochemicals, and corrosion inhibitors. These compounds are highly valued for their reactivity and ability to participate in a wide range of organic syntheses. In this context, the reaction between 1,3-diaminopropan-2-ol and 1,1-bismethylsulfanyl-2-nitroethylene has been studied experimentally and theoretically by using density functional theory (DFT) calculations. A theoretical mechanism of formation of two possible products, 2-(nitromethylene)hexahydropyrimidin-5-ol (with a six-membered heterocycle) and (2-(nitromethylene)oxazolidin-5-yl)methanamine (with a five-membered heterocycle), is for the first time predicted. The present DFT results indicate that both mechanisms are exothermic, with energy barriers approximately 20 kcal/mol higher than those of the reactants. Among the two, the formation of 2-(nitromethylene)hexahydropyrimidin-5-ol is energetically more favorable. This compound was synthesized and analyzed by different experimental techniques (IR, nuclear magnetic resonance (NMR), and high-resolution mass spectrometry). The ¹H and ¹³C NMR chemical shifts of 2-(nitromethylene)hexahydropyrimidin-5-ol were calculated using the GIAO/B3LYP, showing good agreement with our experimental observations. These findings highlight an important match between experimental results and theoretical predictions, offering deeper insights into ketene dithioacetal reactions. The new data and contributions are expected to generate significant interest in future applications.