No abstract

No abstract

Aluminium triisopropoxide, a versatile and cheap oligomeric Lewis acid catalyst, easily reacts with carbon dioxide to build complex oligomeric aluminium alkoxo-alkylcarbonato compounds. A first series of experiments with cyclohexene oxide and CO 2 showed that the catalyst is highly active in the copolymerisation with carbon dioxide and that a satisfactory carbon dioxide insertion takes place when the reaction is run at temperatures between 50 and 80 uC and pressures around 100 bar CO 2 . High yields of polyether-carbonates can be obtained (up to 1000 g of copolymer per g aluminium) with molecular weight up to 11 000 g mol 21 and a better selectivity of the CO 2 -insertion than other aluminium trialkoxides (carbonate to ether linkages ratio: 1 to 3). On the basis of 27 Al-NMR spectra it can be seen that the high reactivity of the catalyst is due to a rearrangement of the stable tetrameric aluminium isopropoxide in a more reactive oligomer and, most likely, during the copolymerisation, to a further fragmentation into reactive monomeric species.

No abstract

A new "halogen-free" binary catalytic system for the synthesis of cyclic carbonate from epoxides and carbon dioxide is described. The catalysis relies on a synergy between the main catalyst, zinc(II) pyridine-2-carboxylate, and a Lewis base, 1-methyl imidazole. In this preliminary study four epoxides have been tested and the operating capabilities of this system have been evaluated. Using propylene oxide as test substrate and performing the catalysis in a high-pressure NMR tube, allowed us to gather some spectroscopic information on this catalytic system and to propose a reaction mechanism.