The effect of pressure on the Diels-Alder reaction was examined in room temperature ionic liquids, followed by high-pressure FT-IR spectroscopy using pressures up to 150 MPa. Pressure enhances the kinetic sensitivity of the reaction. The kinetic effect of fluorophobic interactions was examined using ionic liquids with fluorous cations. Ionic liquids in combination with ZnI₂ as a Lewis acid catalyst were also studied under high pressure.