Abstract
An efficient, mild, and green method was developed for the synthesis of indeno[1,2-b]quinoxaline derivatives via o-phenylenediamine (OPD) and 2-indanone derivatives utilizing β-cyclodextrin (β-CD) as the supramolecular catalyst. The reaction can be carried out in water and in a solid state at room temperature. β-CD can also catalyze the reaction of indan-1,2-dione with OPD with a high degree of efficiency. Compared to the reported methods, this procedure is milder, simpler, and less toxic, making it an eco-friendly alternative. In addition, the β-CD can be recovered and reused without the loss of activity.
Highlights
We explored the synthesis of indeno[1,2-b]quinoxalines at room temperature using β-CD as a catalyst (Scheme 1, Equation (iv))
The results showed that β-CD exhibits high catalytic performance for the construction of indeno[1,2-b]quinoxaline skeleton compounds from 2-indanone and OPD under mild conditions in an aqueous medium
Using 2-indanone and OPD as template substrates, we compared the catalytic effects of the base and of different CDs at room temperature (Table 1, entries 2–8) and ascertained whether the reaction could be carried out in the absence of a catalyst (Table 1, entry 1)
Summary
A great deal of attention has been paid to the construction of indeno[1,2b]quinoxaline skeleton compounds [10] Among these methods, the condensation of OPD with indan-1,2-diones or 1,2,3-indanetriones [11,12,13] (Scheme 1, Equation (i)) and the α-halogenation of 1-indanones with OPDs are the most commonly practiced [14,15]. In addition to these strategies, other oxidation methods or ways of using other types of substrates have been developed, such as the reaction between 2-indanone and OPD [16] (Scheme 1, Equation (iii)) Most of these methodologies still suffer from some disadvantages, such as the use of toxic or strongly alkaline catalysts, hazardous solvents, a complicated process, or the formation of side products. A plausible mechanism was proposed on the basis of two-dimensional nuclear magnetic resonance spectroscopy (2D NMR)
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