[CMMIM][BF 4 ] as a Sustainable Catalyst for Spirooxindoles Synthesis via One‐Pot Multicomponent Reaction: Insights into their Photophysical Properties and Theoretical Calculations

Abstract This study shows an effective approach for the synthesis of spirooxindole‐pyrans and bis‐spirooxindole‐pyrans derivatives using 5 mol % of [CMMIM][BF 4 ] ionic liquid. The synthesis of a library of 28 derivatives was accomplished with impressive yields, ranging from 81 % to 97 %. The derivatives were successfully characterized by 1 H‐NMR, 13 C‐NMR, FT‐IR, and high‐resolution mass spectral techniques. In addition, the photophysical properties of 17 selected derivatives, including the molar extinction coefficient (ϵ) and the Stokes shift (Δυ̅), have been investigated. The values for spirooxindole‐pyrans vary between 14863 to 47372 and 5516 to 9766 cm −1 , respectively. On the other hand, the corresponding values vary from 30871 to 57622 and 9199 to 13351 cm −1 for bis‐spirooxindole‐pyrans. Furthermore, the experimental data is supported by density functional theory (DFT) and time‐dependent DFT calculations. The theoretical studies conducted demonstrated a trend remarkably consistent with the experimental results.