Heterogeneous palladium-catalyzed telomerization of myrcene with glycerol derivatives in supercritical carbon dioxide: a facile route to new building blocks

摘要

In the last two decades, increasing interest has been devoted to the design and utilization of alternative (green) solvents such as ionic liquids and supercritical fluids for catalyzed processes. There has been a large emphasis, in both industrial and academic research, on the development of processes based on alternative solvents, i.e. supercritical fluids. Such processes have addressed a potential advantage of supercritical fluids used as a promising alternative to conventional routes. Owing to the large amount of glycerol that has been formed as a byproduct during biodiesel production, there are great efforts to develop new reactions and processes based on glycerol as a cheap feedstock. Much attention has been directed towards the use of naturally available terpenes as an eligible renewable feedstock for green processes. Myrcene is considered to be an unsaturated renewable hydrocarbon with chemistry similar to well-established chemicals of fossil origin. Myrcene has already been used in industry because it is easily obtained from the crude resin of pines. Myrcene is a promising candidate for processes carried out in scCO2 because CO2 is highly soluble in myrcene and recent research has demonstrated the potential for using scCO2 in the heterogeneously catalyzed selective hydrogenation of myrcene. The critical pressure of myrcene and CO2 system is conveniently below 10 MPa at moderate temperatures, allowing an easy switching from two phases to a homogeneous one-phase fluid. A homogeneous telomerization of P-myrcene with diethylamine, similarly to commonly used 1,3-butadiene and isopropene, has been reported to generate C_(20) amines. A heterogeneous telomerization of β-myrcene seems like an obvious alternative to expensive homogeneous telomerization where rare metals as catalysts used must be recycled as completely as possible.