Dipolar and aprotic solvents are often required in acid‐catalyzed reactions, however, many of them are listed in solvent selection guides as not‐recommended due to their toxicity or explosivity. A catalytically functionalized ionic liquid, namely a sulfone‐containing imidazolium‐based Brønsted acid ionic liquid, was synthesized. It alleviates the detrimental effect of classical dipolar aprotic solvents because this ionic liquid integrates the function of a dipolar aprotic solvent able to stabilize carbocation intermediates and the activating effect of a strong Brønsted acid on electrophiles. The use of this tailor‐made ionic liquid was exemplified in some transformation reactions of indoles, which proceeded with high yield and selectivity using a green and an industrially acceptable solvent, butyl acetate. The recyclability of the ionic liquid catalyst was also demonstrated. Industrially acceptable: Dipolar and aprotic solvents are widely used in organic synthesis. These solvents are however generally toxic and hazardous. We created a new ionic liquid that allow the acid‐catalyzed reactions performed very well in green and an industrially acceptable solvent, butyl acetate. Indole transformations are model reactions to show the proof‐of‐the‐concept.