Heterocyclic compounds containing nitrogen and oxygen atoms are of great importance and wide applications in the fields of biomedicine and functional materials. In this paper, novel 13-aryl-6H,12H-6,12-epiminodibenzo[b,f][1,5]dioxocines generated from cascade reactions between arylamines and 2-hydroxybenzaldehyde have been explored through both experiments and theoretical calculations. Experimental investigations showed that pyrimidin-2-amine could react with 2-hydroxybenzaldehyde in acetonitrile at 80 °C to afford the desired 13-(pyrimidin-2-yl)-6H,12H-6,12-epiminodibenzo[b,f][1,5]dioxocines with 50 mol % of p-toluenesulfonic acid as catalyst, but aniline reacted with 2-hydroxybenzaldehyde to generate aldimine instead of the target bridged heterocylic compound. Density functional theory (DFT) computations were conducted to investigate the reaction mechanisms of 2-hydroxybenzaldehyde reacting with pyrimidin-2-amine and aniline, respectively. The experimental findings can be reasonably explained by theoretical calculations. Both the experimental explorations and suggested mechanisms indicate that the reactivity of the model reaction is sensitive to the electron density on the amino group of arylamine and the aldehyde group of 2-hydroxybenzaldehyde, which can be finely tuned with the aromatic ring structure and the substituents on it.
Read full abstract