Evaluating Lewis acid catalyzed hydroalkylation of alkenes in neat and in ionic liquids

Recent emphasis on green chemistry has called for the exploration of more environmentally friendly media such as supercritical CO2 and water. Ionic liquids offer interesting alternative reaction media to volatile organic solvents due to their low vapor pressure and the possibility of recycling. Towards this end, we have explored the addition of activated methylenes to alkenes in ionic liquids and under neat conditions. These alternatives are advantageous over our previous method, which requires the use of toxic organic solvent and expensive catalysts. Our results show that 1,3-diketones can be added to alkenes in ionic liquid with the use of 10% SnBr4 or under solventless conditions with 10% Cu(OTf)2. Up to 85% yield can be achieved using these new methodologies.

Graphical abstractAddition of 1,3-dicarbonyls to alkenes is catalyzed by 10% SnBr4 in ionic liquid or by 10% Cu(OTf)2 in solventless conditions. The method is more environmentally benign and avoids the use of volatile organic solvents. Figure optionsDownload full-size imageDownload as PowerPoint slide