Silica-supported chlorometallate(iii) ionic liquids as recyclable catalysts for Diels-Alder reaction under solventless conditionsElectronic supplementary information (ESI) available. See DOI: 10.1039/c6cy01771a

A range of Lewis acidic metal chlorides were tested as homogeneous catalysts in a model Diels-Alder reaction; AlCl 3 and GaCl 3 performed best in terms of conversion and endo : exo selectivity. Based on this outcome, the corresponding chlorometallate( iii ) ionic liquids were tested as homogeneous catalysts, without a decrease in performance compared to the chlorides. Finally, these ionic liquids were heterogenised by covalent tethering of the cation onto a multimodal porous silica support; such supported chlorogallate( iii ) ionic liquids are reported for the first time. Supported chlorometallate( iii ) ionic liquids were used as recyclable heterogeneous catalysts for the Diels-Alder reaction under solventless conditions. High yields (99%) and high endo -selectivities (95%) were obtained after very short reaction times (5 min) at near-ambient temperature (25 °C). The first catalytic application of supported chlorometallate( iii ) ionic liquids as recyclable heterogeneous catalysts for a Diels-Alder reaction under solventless conditions.