Hydroaminomethylation of n-alkenes in a biphasic ionic liquid system

Hydroaminomethylation reactions were performed successfully in an imidazolium-based ionic liquid using a rhodium/sulfoxantphos system by reacting piperidine with different n-alkenes, affording yields higher than 95% of the resulting amine with turnover frequencies of up to 16,000 h(-1), along with high regioselectivity for the linear amines with l/b ratios up to 78. Additionally, facile quantitative catalyst recovery was accomplished and recycling of the catalyst and product separation was achieved by a fast phase separation after the reaction. The product distribution was monitored over time at different temperatures both in an organic solvent and in the ionic liquid in order to investigate and compare the course of the formation of (side) products and intermediates in these reactions. Furthermore, it was shown that the nature of the rhodium precatalyst has a profound effect on the activity and selectivity. Protic organic solvents and ionic liquids containing a C-H acidic bond in the imidazolium part have a beneficial effect on the hydrogenation activity of the catalyst systems.